From d5253bba324b2a31ad752f152ac424ccbf5dc00f Mon Sep 17 00:00:00 2001
From: gabor-mezei-arm <gabor.mezei@arm.com>
Date: Thu, 30 Jul 2020 16:41:25 +0200
Subject: [PATCH 01/19] Zeroize internal buffers and variables in PKCS and SHA

Zeroising of local buffers and variables which are used for calculations in
mbedtls_pkcs5_pbkdf2_hmac() and mbedtls_internal_sha*_process() functions
to erase sensitive data from memory.
Checked all function for possible missing zeroisation in PKCS and SHA.

Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
---
 ...oizations_of_sensitive_data_in_PKCS5_and_SHA.txt |  5 +++++
 library/pkcs5.c                                     |  4 ++++
 library/sha1.c                                      |  9 +++++++++
 library/sha256.c                                    |  6 ++++++
 library/sha512.c                                    | 13 +++++++++++++
 5 files changed, 37 insertions(+)
 create mode 100644 ChangeLog.d/zeroizations_of_sensitive_data_in_PKCS5_and_SHA.txt

diff --git a/ChangeLog.d/zeroizations_of_sensitive_data_in_PKCS5_and_SHA.txt b/ChangeLog.d/zeroizations_of_sensitive_data_in_PKCS5_and_SHA.txt
new file mode 100644
index 000000000..f8445615c
--- /dev/null
+++ b/ChangeLog.d/zeroizations_of_sensitive_data_in_PKCS5_and_SHA.txt
@@ -0,0 +1,5 @@
+Security
+   * Zeroising of local buffers and variables which are used for calculations
+     in mbedtls_pkcs5_pbkdf2_hmac() and mbedtls_internal_sha*_process()
+     functions to erase sensitive data from memory. Reported by
+     Johan Malmgren and Johan Uppman Bruce from Sectra.
diff --git a/library/pkcs5.c b/library/pkcs5.c
index 8a80aa5d0..69b85deeb 100644
--- a/library/pkcs5.c
+++ b/library/pkcs5.c
@@ -312,6 +312,10 @@ int mbedtls_pkcs5_pbkdf2_hmac( mbedtls_md_context_t *ctx, const unsigned char *p
                 break;
     }
 
+    /* Zeroise buffers to clear sensitive data from memory. */
+    mbedtls_platform_zeroize( work, MBEDTLS_MD_MAX_SIZE );
+    mbedtls_platform_zeroize( md1, MBEDTLS_MD_MAX_SIZE );
+
     return( 0 );
 }
 
diff --git a/library/sha1.c b/library/sha1.c
index 8682abd74..4bb51982f 100644
--- a/library/sha1.c
+++ b/library/sha1.c
@@ -313,6 +313,15 @@ int mbedtls_internal_sha1_process( mbedtls_sha1_context *ctx,
     ctx->state[3] += D;
     ctx->state[4] += E;
 
+    /* Zeroise buffers and variables to clear sensitive data from memory. */
+    mbedtls_platform_zeroize( &A, sizeof( A ) );
+    mbedtls_platform_zeroize( &B, sizeof( B ) );
+    mbedtls_platform_zeroize( &C, sizeof( C ) );
+    mbedtls_platform_zeroize( &D, sizeof( D ) );
+    mbedtls_platform_zeroize( &E, sizeof( E ) );
+    mbedtls_platform_zeroize( &W, sizeof( W ) );
+    mbedtls_platform_zeroize( &temp, sizeof( temp ) );
+
     return( 0 );
 }
 
diff --git a/library/sha256.c b/library/sha256.c
index 5169584b6..2decd08f0 100644
--- a/library/sha256.c
+++ b/library/sha256.c
@@ -281,6 +281,12 @@ int mbedtls_internal_sha256_process( mbedtls_sha256_context *ctx,
     for( i = 0; i < 8; i++ )
         ctx->state[i] += A[i];
 
+    /* Zeroise buffers and variables to clear sensitive data from memory. */
+    mbedtls_platform_zeroize( &A, sizeof( A ) );
+    mbedtls_platform_zeroize( &W, sizeof( W ) );
+    mbedtls_platform_zeroize( &temp1, sizeof( temp1 ) );
+    mbedtls_platform_zeroize( &temp2, sizeof( temp2 ) );
+
     return( 0 );
 }
 
diff --git a/library/sha512.c b/library/sha512.c
index 36d5d9614..37a01dd7b 100644
--- a/library/sha512.c
+++ b/library/sha512.c
@@ -312,6 +312,19 @@ int mbedtls_internal_sha512_process( mbedtls_sha512_context *ctx,
     ctx->state[6] += G;
     ctx->state[7] += H;
 
+    /* Zeroise buffers and variables to clear sensitive data from memory. */
+    mbedtls_platform_zeroize( &A, sizeof( A ) );
+    mbedtls_platform_zeroize( &B, sizeof( B ) );
+    mbedtls_platform_zeroize( &C, sizeof( C ) );
+    mbedtls_platform_zeroize( &D, sizeof( D ) );
+    mbedtls_platform_zeroize( &E, sizeof( E ) );
+    mbedtls_platform_zeroize( &F, sizeof( F ) );
+    mbedtls_platform_zeroize( &G, sizeof( G ) );
+    mbedtls_platform_zeroize( &H, sizeof( H ) );
+    mbedtls_platform_zeroize( &W, sizeof( W ) );
+    mbedtls_platform_zeroize( &temp1, sizeof( temp1 ) );
+    mbedtls_platform_zeroize( &temp2, sizeof( temp2 ) );
+
     return( 0 );
 }
 

From 5feba8dae17cb590811ccaf72facd4a4a32c5ae3 Mon Sep 17 00:00:00 2001
From: gabor-mezei-arm <gabor.mezei@arm.com>
Date: Wed, 19 Aug 2020 14:01:03 +0200
Subject: [PATCH 02/19] Force cleanup before return

Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
---
 library/pkcs5.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/library/pkcs5.c b/library/pkcs5.c
index 69b85deeb..c4447f154 100644
--- a/library/pkcs5.c
+++ b/library/pkcs5.c
@@ -247,7 +247,7 @@ int mbedtls_pkcs5_pbkdf2_hmac( mbedtls_md_context_t *ctx, const unsigned char *p
                        unsigned int iteration_count,
                        uint32_t key_length, unsigned char *output )
 {
-    int ret, j;
+    int ret = 0, j;
     unsigned int i;
     unsigned char md1[MBEDTLS_MD_MAX_SIZE];
     unsigned char work[MBEDTLS_MD_MAX_SIZE];
@@ -269,16 +269,16 @@ int mbedtls_pkcs5_pbkdf2_hmac( mbedtls_md_context_t *ctx, const unsigned char *p
         // U1 ends up in work
         //
         if( ( ret = mbedtls_md_hmac_starts( ctx, password, plen ) ) != 0 )
-            return( ret );
+            goto cleanup;
 
         if( ( ret = mbedtls_md_hmac_update( ctx, salt, slen ) ) != 0 )
-            return( ret );
+            goto cleanup;
 
         if( ( ret = mbedtls_md_hmac_update( ctx, counter, 4 ) ) != 0 )
-            return( ret );
+            goto cleanup;
 
         if( ( ret = mbedtls_md_hmac_finish( ctx, work ) ) != 0 )
-            return( ret );
+            goto cleanup;
 
         memcpy( md1, work, md_size );
 
@@ -287,13 +287,13 @@ int mbedtls_pkcs5_pbkdf2_hmac( mbedtls_md_context_t *ctx, const unsigned char *p
             // U2 ends up in md1
             //
             if( ( ret = mbedtls_md_hmac_starts( ctx, password, plen ) ) != 0 )
-                return( ret );
+                goto cleanup;
 
             if( ( ret = mbedtls_md_hmac_update( ctx, md1, md_size ) ) != 0 )
-                return( ret );
+                goto cleanup;
 
             if( ( ret = mbedtls_md_hmac_finish( ctx, md1 ) ) != 0 )
-                return( ret );
+                goto cleanup;
 
             // U1 xor U2
             //
@@ -312,11 +312,12 @@ int mbedtls_pkcs5_pbkdf2_hmac( mbedtls_md_context_t *ctx, const unsigned char *p
                 break;
     }
 
+cleanup:
     /* Zeroise buffers to clear sensitive data from memory. */
     mbedtls_platform_zeroize( work, MBEDTLS_MD_MAX_SIZE );
     mbedtls_platform_zeroize( md1, MBEDTLS_MD_MAX_SIZE );
 
-    return( 0 );
+    return( ret );
 }
 
 #if defined(MBEDTLS_SELF_TEST)

From f21639fc2fe67a7e2ad6a70c7f1377c1b6a76053 Mon Sep 17 00:00:00 2001
From: gabor-mezei-arm <gabor.mezei@arm.com>
Date: Wed, 19 Aug 2020 14:03:06 +0200
Subject: [PATCH 03/19] Zeroize internal buffers and variables in MD hashes

Zeroising of local buffers and variables which are used for calculations in
mbedtls_internal_md*_process() and mbedtls_internal_ripemd160_process()
functions to erase sensitive data from memory.
Checked all function for possible missing zeroisation in MD.

Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
---
 ...oizations_of_sensitive_data_in_PKCS5_and_SHA.txt |  3 ++-
 library/md2.c                                       |  3 +++
 library/md4.c                                       |  7 +++++++
 library/md5.c                                       |  7 +++++++
 library/ripemd160.c                                 | 13 +++++++++++++
 5 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/ChangeLog.d/zeroizations_of_sensitive_data_in_PKCS5_and_SHA.txt b/ChangeLog.d/zeroizations_of_sensitive_data_in_PKCS5_and_SHA.txt
index f8445615c..320bb0e86 100644
--- a/ChangeLog.d/zeroizations_of_sensitive_data_in_PKCS5_and_SHA.txt
+++ b/ChangeLog.d/zeroizations_of_sensitive_data_in_PKCS5_and_SHA.txt
@@ -1,5 +1,6 @@
 Security
    * Zeroising of local buffers and variables which are used for calculations
-     in mbedtls_pkcs5_pbkdf2_hmac() and mbedtls_internal_sha*_process()
+     in mbedtls_pkcs5_pbkdf2_hmac(), mbedtls_internal_sha*_process(),
+     mbedtls_internal_md*_process() and mbedtls_internal_ripemd160_process()
      functions to erase sensitive data from memory. Reported by
      Johan Malmgren and Johan Uppman Bruce from Sectra.
diff --git a/library/md2.c b/library/md2.c
index cbdaaabdc..fdcb630a1 100644
--- a/library/md2.c
+++ b/library/md2.c
@@ -177,6 +177,9 @@ int mbedtls_internal_md2_process( mbedtls_md2_context *ctx )
         t  = ctx->cksum[i];
     }
 
+    /* Zeroise variables to clear sensitive data from memory. */
+    mbedtls_platform_zeroize( &t, sizeof( t ) );
+
     return( 0 );
 }
 
diff --git a/library/md4.c b/library/md4.c
index cb16dce54..63bdcecf0 100644
--- a/library/md4.c
+++ b/library/md4.c
@@ -259,6 +259,13 @@ int mbedtls_internal_md4_process( mbedtls_md4_context *ctx,
     ctx->state[2] += C;
     ctx->state[3] += D;
 
+    /* Zeroise variables to clear sensitive data from memory. */
+    mbedtls_platform_zeroize( &X, sizeof( X ) );
+    mbedtls_platform_zeroize( &A, sizeof( A ) );
+    mbedtls_platform_zeroize( &B, sizeof( B ) );
+    mbedtls_platform_zeroize( &C, sizeof( C ) );
+    mbedtls_platform_zeroize( &D, sizeof( D ) );
+
     return( 0 );
 }
 
diff --git a/library/md5.c b/library/md5.c
index fe2592521..df783c3ac 100644
--- a/library/md5.c
+++ b/library/md5.c
@@ -265,6 +265,13 @@ int mbedtls_internal_md5_process( mbedtls_md5_context *ctx,
     ctx->state[2] += C;
     ctx->state[3] += D;
 
+    /* Zeroise variables to clear sensitive data from memory. */
+    mbedtls_platform_zeroize( &X, sizeof( X ) );
+    mbedtls_platform_zeroize( &A, sizeof( A ) );
+    mbedtls_platform_zeroize( &B, sizeof( B ) );
+    mbedtls_platform_zeroize( &C, sizeof( C ) );
+    mbedtls_platform_zeroize( &D, sizeof( D ) );
+
     return( 0 );
 }
 
diff --git a/library/ripemd160.c b/library/ripemd160.c
index 0b6efcb57..b991b5689 100644
--- a/library/ripemd160.c
+++ b/library/ripemd160.c
@@ -328,6 +328,19 @@ int mbedtls_internal_ripemd160_process( mbedtls_ripemd160_context *ctx,
     ctx->state[4] = ctx->state[0] + B + Cp;
     ctx->state[0] = C;
 
+    /* Zeroise variables to clear sensitive data from memory. */
+    mbedtls_platform_zeroize( &A, sizeof( A ) );
+    mbedtls_platform_zeroize( &B, sizeof( B ) );
+    mbedtls_platform_zeroize( &C, sizeof( C ) );
+    mbedtls_platform_zeroize( &D, sizeof( D ) );
+    mbedtls_platform_zeroize( &E, sizeof( E ) );
+    mbedtls_platform_zeroize( &Ap, sizeof( Ap ) );
+    mbedtls_platform_zeroize( &Bp, sizeof( Bp ) );
+    mbedtls_platform_zeroize( &Cp, sizeof( Cp ) );
+    mbedtls_platform_zeroize( &Dp, sizeof( Dp ) );
+    mbedtls_platform_zeroize( &Ep, sizeof( Ep ) );
+    mbedtls_platform_zeroize( &X, sizeof( X ) );
+
     return( 0 );
 }
 

From 70f7f6713312d72de51fce6cac3924cf384f5c67 Mon Sep 17 00:00:00 2001
From: gabor-mezei-arm <gabor.mezei@arm.com>
Date: Tue, 25 Aug 2020 19:12:01 +0200
Subject: [PATCH 04/19] Put local variables and buffers in a struct

This reduces the impact of the code size increase due to the addition
of calls to mbedtls_platform_zeroize.

Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
---
 library/md4.c       | 155 ++++++++++++++--------------
 library/md5.c       | 197 ++++++++++++++++++-----------------
 library/ripemd160.c | 243 +++++++++++++++++++++-----------------------
 library/sha1.c      | 233 +++++++++++++++++++++---------------------
 library/sha256.c    |  99 +++++++++++-------
 library/sha512.c    |  93 ++++++++---------
 6 files changed, 516 insertions(+), 504 deletions(-)

diff --git a/library/md4.c b/library/md4.c
index 63bdcecf0..95e893e65 100644
--- a/library/md4.c
+++ b/library/md4.c
@@ -143,31 +143,34 @@ void mbedtls_md4_starts( mbedtls_md4_context *ctx )
 int mbedtls_internal_md4_process( mbedtls_md4_context *ctx,
                                   const unsigned char data[64] )
 {
-    uint32_t X[16], A, B, C, D;
+    struct
+    {
+        uint32_t X[16], A, B, C, D;
+    } local;
 
-    GET_UINT32_LE( X[ 0], data,  0 );
-    GET_UINT32_LE( X[ 1], data,  4 );
-    GET_UINT32_LE( X[ 2], data,  8 );
-    GET_UINT32_LE( X[ 3], data, 12 );
-    GET_UINT32_LE( X[ 4], data, 16 );
-    GET_UINT32_LE( X[ 5], data, 20 );
-    GET_UINT32_LE( X[ 6], data, 24 );
-    GET_UINT32_LE( X[ 7], data, 28 );
-    GET_UINT32_LE( X[ 8], data, 32 );
-    GET_UINT32_LE( X[ 9], data, 36 );
-    GET_UINT32_LE( X[10], data, 40 );
-    GET_UINT32_LE( X[11], data, 44 );
-    GET_UINT32_LE( X[12], data, 48 );
-    GET_UINT32_LE( X[13], data, 52 );
-    GET_UINT32_LE( X[14], data, 56 );
-    GET_UINT32_LE( X[15], data, 60 );
+    GET_UINT32_LE( local.X[ 0], data,  0 );
+    GET_UINT32_LE( local.X[ 1], data,  4 );
+    GET_UINT32_LE( local.X[ 2], data,  8 );
+    GET_UINT32_LE( local.X[ 3], data, 12 );
+    GET_UINT32_LE( local.X[ 4], data, 16 );
+    GET_UINT32_LE( local.X[ 5], data, 20 );
+    GET_UINT32_LE( local.X[ 6], data, 24 );
+    GET_UINT32_LE( local.X[ 7], data, 28 );
+    GET_UINT32_LE( local.X[ 8], data, 32 );
+    GET_UINT32_LE( local.X[ 9], data, 36 );
+    GET_UINT32_LE( local.X[10], data, 40 );
+    GET_UINT32_LE( local.X[11], data, 44 );
+    GET_UINT32_LE( local.X[12], data, 48 );
+    GET_UINT32_LE( local.X[13], data, 52 );
+    GET_UINT32_LE( local.X[14], data, 56 );
+    GET_UINT32_LE( local.X[15], data, 60 );
 
 #define S(x,n) (((x) << (n)) | (((x) & 0xFFFFFFFF) >> (32 - (n))))
 
-    A = ctx->state[0];
-    B = ctx->state[1];
-    C = ctx->state[2];
-    D = ctx->state[3];
+    local.A = ctx->state[0];
+    local.B = ctx->state[1];
+    local.C = ctx->state[2];
+    local.D = ctx->state[3];
 
 #define F(x, y, z) (((x) & (y)) | ((~(x)) & (z)))
 #define P(a,b,c,d,x,s)                           \
@@ -178,22 +181,22 @@ int mbedtls_internal_md4_process( mbedtls_md4_context *ctx,
     } while( 0 )
 
 
-    P( A, B, C, D, X[ 0],  3 );
-    P( D, A, B, C, X[ 1],  7 );
-    P( C, D, A, B, X[ 2], 11 );
-    P( B, C, D, A, X[ 3], 19 );
-    P( A, B, C, D, X[ 4],  3 );
-    P( D, A, B, C, X[ 5],  7 );
-    P( C, D, A, B, X[ 6], 11 );
-    P( B, C, D, A, X[ 7], 19 );
-    P( A, B, C, D, X[ 8],  3 );
-    P( D, A, B, C, X[ 9],  7 );
-    P( C, D, A, B, X[10], 11 );
-    P( B, C, D, A, X[11], 19 );
-    P( A, B, C, D, X[12],  3 );
-    P( D, A, B, C, X[13],  7 );
-    P( C, D, A, B, X[14], 11 );
-    P( B, C, D, A, X[15], 19 );
+    P( local.A, local.B, local.C, local.D, local.X[ 0],  3 );
+    P( local.D, local.A, local.B, local.C, local.X[ 1],  7 );
+    P( local.C, local.D, local.A, local.B, local.X[ 2], 11 );
+    P( local.B, local.C, local.D, local.A, local.X[ 3], 19 );
+    P( local.A, local.B, local.C, local.D, local.X[ 4],  3 );
+    P( local.D, local.A, local.B, local.C, local.X[ 5],  7 );
+    P( local.C, local.D, local.A, local.B, local.X[ 6], 11 );
+    P( local.B, local.C, local.D, local.A, local.X[ 7], 19 );
+    P( local.A, local.B, local.C, local.D, local.X[ 8],  3 );
+    P( local.D, local.A, local.B, local.C, local.X[ 9],  7 );
+    P( local.C, local.D, local.A, local.B, local.X[10], 11 );
+    P( local.B, local.C, local.D, local.A, local.X[11], 19 );
+    P( local.A, local.B, local.C, local.D, local.X[12],  3 );
+    P( local.D, local.A, local.B, local.C, local.X[13],  7 );
+    P( local.C, local.D, local.A, local.B, local.X[14], 11 );
+    P( local.B, local.C, local.D, local.A, local.X[15], 19 );
 
 #undef P
 #undef F
@@ -206,22 +209,22 @@ int mbedtls_internal_md4_process( mbedtls_md4_context *ctx,
         (a) = S((a),(s));                               \
     } while( 0 )
 
-    P( A, B, C, D, X[ 0],  3 );
-    P( D, A, B, C, X[ 4],  5 );
-    P( C, D, A, B, X[ 8],  9 );
-    P( B, C, D, A, X[12], 13 );
-    P( A, B, C, D, X[ 1],  3 );
-    P( D, A, B, C, X[ 5],  5 );
-    P( C, D, A, B, X[ 9],  9 );
-    P( B, C, D, A, X[13], 13 );
-    P( A, B, C, D, X[ 2],  3 );
-    P( D, A, B, C, X[ 6],  5 );
-    P( C, D, A, B, X[10],  9 );
-    P( B, C, D, A, X[14], 13 );
-    P( A, B, C, D, X[ 3],  3 );
-    P( D, A, B, C, X[ 7],  5 );
-    P( C, D, A, B, X[11],  9 );
-    P( B, C, D, A, X[15], 13 );
+    P( local.A, local.B, local.C, local.D, local.X[ 0],  3 );
+    P( local.D, local.A, local.B, local.C, local.X[ 4],  5 );
+    P( local.C, local.D, local.A, local.B, local.X[ 8],  9 );
+    P( local.B, local.C, local.D, local.A, local.X[12], 13 );
+    P( local.A, local.B, local.C, local.D, local.X[ 1],  3 );
+    P( local.D, local.A, local.B, local.C, local.X[ 5],  5 );
+    P( local.C, local.D, local.A, local.B, local.X[ 9],  9 );
+    P( local.B, local.C, local.D, local.A, local.X[13], 13 );
+    P( local.A, local.B, local.C, local.D, local.X[ 2],  3 );
+    P( local.D, local.A, local.B, local.C, local.X[ 6],  5 );
+    P( local.C, local.D, local.A, local.B, local.X[10],  9 );
+    P( local.B, local.C, local.D, local.A, local.X[14], 13 );
+    P( local.A, local.B, local.C, local.D, local.X[ 3],  3 );
+    P( local.D, local.A, local.B, local.C, local.X[ 7],  5 );
+    P( local.C, local.D, local.A, local.B, local.X[11],  9 );
+    P( local.B, local.C, local.D, local.A, local.X[15], 13 );
 
 #undef P
 #undef F
@@ -234,37 +237,33 @@ int mbedtls_internal_md4_process( mbedtls_md4_context *ctx,
         (a) = S((a),(s));                               \
     } while( 0 )
 
-    P( A, B, C, D, X[ 0],  3 );
-    P( D, A, B, C, X[ 8],  9 );
-    P( C, D, A, B, X[ 4], 11 );
-    P( B, C, D, A, X[12], 15 );
-    P( A, B, C, D, X[ 2],  3 );
-    P( D, A, B, C, X[10],  9 );
-    P( C, D, A, B, X[ 6], 11 );
-    P( B, C, D, A, X[14], 15 );
-    P( A, B, C, D, X[ 1],  3 );
-    P( D, A, B, C, X[ 9],  9 );
-    P( C, D, A, B, X[ 5], 11 );
-    P( B, C, D, A, X[13], 15 );
-    P( A, B, C, D, X[ 3],  3 );
-    P( D, A, B, C, X[11],  9 );
-    P( C, D, A, B, X[ 7], 11 );
-    P( B, C, D, A, X[15], 15 );
+    P( local.A, local.B, local.C, local.D, local.X[ 0],  3 );
+    P( local.D, local.A, local.B, local.C, local.X[ 8],  9 );
+    P( local.C, local.D, local.A, local.B, local.X[ 4], 11 );
+    P( local.B, local.C, local.D, local.A, local.X[12], 15 );
+    P( local.A, local.B, local.C, local.D, local.X[ 2],  3 );
+    P( local.D, local.A, local.B, local.C, local.X[10],  9 );
+    P( local.C, local.D, local.A, local.B, local.X[ 6], 11 );
+    P( local.B, local.C, local.D, local.A, local.X[14], 15 );
+    P( local.A, local.B, local.C, local.D, local.X[ 1],  3 );
+    P( local.D, local.A, local.B, local.C, local.X[ 9],  9 );
+    P( local.C, local.D, local.A, local.B, local.X[ 5], 11 );
+    P( local.B, local.C, local.D, local.A, local.X[13], 15 );
+    P( local.A, local.B, local.C, local.D, local.X[ 3],  3 );
+    P( local.D, local.A, local.B, local.C, local.X[11],  9 );
+    P( local.C, local.D, local.A, local.B, local.X[ 7], 11 );
+    P( local.B, local.C, local.D, local.A, local.X[15], 15 );
 
 #undef F
 #undef P
 
-    ctx->state[0] += A;
-    ctx->state[1] += B;
-    ctx->state[2] += C;
-    ctx->state[3] += D;
+    ctx->state[0] += local.A;
+    ctx->state[1] += local.B;
+    ctx->state[2] += local.C;
+    ctx->state[3] += local.D;
 
     /* Zeroise variables to clear sensitive data from memory. */
-    mbedtls_platform_zeroize( &X, sizeof( X ) );
-    mbedtls_platform_zeroize( &A, sizeof( A ) );
-    mbedtls_platform_zeroize( &B, sizeof( B ) );
-    mbedtls_platform_zeroize( &C, sizeof( C ) );
-    mbedtls_platform_zeroize( &D, sizeof( D ) );
+    mbedtls_platform_zeroize( &local, sizeof( local ) );
 
     return( 0 );
 }
diff --git a/library/md5.c b/library/md5.c
index df783c3ac..d2b634fbb 100644
--- a/library/md5.c
+++ b/library/md5.c
@@ -142,135 +142,134 @@ void mbedtls_md5_starts( mbedtls_md5_context *ctx )
 int mbedtls_internal_md5_process( mbedtls_md5_context *ctx,
                                   const unsigned char data[64] )
 {
-    uint32_t X[16], A, B, C, D;
+    struct
+    {
+        uint32_t X[16], A, B, C, D;
+    } local;
 
-    GET_UINT32_LE( X[ 0], data,  0 );
-    GET_UINT32_LE( X[ 1], data,  4 );
-    GET_UINT32_LE( X[ 2], data,  8 );
-    GET_UINT32_LE( X[ 3], data, 12 );
-    GET_UINT32_LE( X[ 4], data, 16 );
-    GET_UINT32_LE( X[ 5], data, 20 );
-    GET_UINT32_LE( X[ 6], data, 24 );
-    GET_UINT32_LE( X[ 7], data, 28 );
-    GET_UINT32_LE( X[ 8], data, 32 );
-    GET_UINT32_LE( X[ 9], data, 36 );
-    GET_UINT32_LE( X[10], data, 40 );
-    GET_UINT32_LE( X[11], data, 44 );
-    GET_UINT32_LE( X[12], data, 48 );
-    GET_UINT32_LE( X[13], data, 52 );
-    GET_UINT32_LE( X[14], data, 56 );
-    GET_UINT32_LE( X[15], data, 60 );
+    GET_UINT32_LE( local.X[ 0], data,  0 );
+    GET_UINT32_LE( local.X[ 1], data,  4 );
+    GET_UINT32_LE( local.X[ 2], data,  8 );
+    GET_UINT32_LE( local.X[ 3], data, 12 );
+    GET_UINT32_LE( local.X[ 4], data, 16 );
+    GET_UINT32_LE( local.X[ 5], data, 20 );
+    GET_UINT32_LE( local.X[ 6], data, 24 );
+    GET_UINT32_LE( local.X[ 7], data, 28 );
+    GET_UINT32_LE( local.X[ 8], data, 32 );
+    GET_UINT32_LE( local.X[ 9], data, 36 );
+    GET_UINT32_LE( local.X[10], data, 40 );
+    GET_UINT32_LE( local.X[11], data, 44 );
+    GET_UINT32_LE( local.X[12], data, 48 );
+    GET_UINT32_LE( local.X[13], data, 52 );
+    GET_UINT32_LE( local.X[14], data, 56 );
+    GET_UINT32_LE( local.X[15], data, 60 );
 
 #define S(x,n)                                                          \
     ( ( (x) << (n) ) | ( ( (x) & 0xFFFFFFFF) >> ( 32 - (n) ) ) )
 
-#define P(a,b,c,d,k,s,t)                                        \
-    do                                                          \
-    {                                                           \
-        (a) += F((b),(c),(d)) + X[(k)] + (t);                   \
-        (a) = S((a),(s)) + (b);                                 \
+#define P(a,b,c,d,k,s,t)                                                \
+    do                                                                  \
+    {                                                                   \
+        (a) += F((b),(c),(d)) + local.X[(k)] + (t);                     \
+        (a) = S((a),(s)) + (b);                                         \
     } while( 0 )
 
-    A = ctx->state[0];
-    B = ctx->state[1];
-    C = ctx->state[2];
-    D = ctx->state[3];
+    local.A = ctx->state[0];
+    local.B = ctx->state[1];
+    local.C = ctx->state[2];
+    local.D = ctx->state[3];
 
 #define F(x,y,z) ((z) ^ ((x) & ((y) ^ (z))))
 
-    P( A, B, C, D,  0,  7, 0xD76AA478 );
-    P( D, A, B, C,  1, 12, 0xE8C7B756 );
-    P( C, D, A, B,  2, 17, 0x242070DB );
-    P( B, C, D, A,  3, 22, 0xC1BDCEEE );
-    P( A, B, C, D,  4,  7, 0xF57C0FAF );
-    P( D, A, B, C,  5, 12, 0x4787C62A );
-    P( C, D, A, B,  6, 17, 0xA8304613 );
-    P( B, C, D, A,  7, 22, 0xFD469501 );
-    P( A, B, C, D,  8,  7, 0x698098D8 );
-    P( D, A, B, C,  9, 12, 0x8B44F7AF );
-    P( C, D, A, B, 10, 17, 0xFFFF5BB1 );
-    P( B, C, D, A, 11, 22, 0x895CD7BE );
-    P( A, B, C, D, 12,  7, 0x6B901122 );
-    P( D, A, B, C, 13, 12, 0xFD987193 );
-    P( C, D, A, B, 14, 17, 0xA679438E );
-    P( B, C, D, A, 15, 22, 0x49B40821 );
+    P( local.A, local.B, local.C, local.D,  0,  7, 0xD76AA478 );
+    P( local.D, local.A, local.B, local.C,  1, 12, 0xE8C7B756 );
+    P( local.C, local.D, local.A, local.B,  2, 17, 0x242070DB );
+    P( local.B, local.C, local.D, local.A,  3, 22, 0xC1BDCEEE );
+    P( local.A, local.B, local.C, local.D,  4,  7, 0xF57C0FAF );
+    P( local.D, local.A, local.B, local.C,  5, 12, 0x4787C62A );
+    P( local.C, local.D, local.A, local.B,  6, 17, 0xA8304613 );
+    P( local.B, local.C, local.D, local.A,  7, 22, 0xFD469501 );
+    P( local.A, local.B, local.C, local.D,  8,  7, 0x698098D8 );
+    P( local.D, local.A, local.B, local.C,  9, 12, 0x8B44F7AF );
+    P( local.C, local.D, local.A, local.B, 10, 17, 0xFFFF5BB1 );
+    P( local.B, local.C, local.D, local.A, 11, 22, 0x895CD7BE );
+    P( local.A, local.B, local.C, local.D, 12,  7, 0x6B901122 );
+    P( local.D, local.A, local.B, local.C, 13, 12, 0xFD987193 );
+    P( local.C, local.D, local.A, local.B, 14, 17, 0xA679438E );
+    P( local.B, local.C, local.D, local.A, 15, 22, 0x49B40821 );
 
 #undef F
 
 #define F(x,y,z) ((y) ^ ((z) & ((x) ^ (y))))
 
-    P( A, B, C, D,  1,  5, 0xF61E2562 );
-    P( D, A, B, C,  6,  9, 0xC040B340 );
-    P( C, D, A, B, 11, 14, 0x265E5A51 );
-    P( B, C, D, A,  0, 20, 0xE9B6C7AA );
-    P( A, B, C, D,  5,  5, 0xD62F105D );
-    P( D, A, B, C, 10,  9, 0x02441453 );
-    P( C, D, A, B, 15, 14, 0xD8A1E681 );
-    P( B, C, D, A,  4, 20, 0xE7D3FBC8 );
-    P( A, B, C, D,  9,  5, 0x21E1CDE6 );
-    P( D, A, B, C, 14,  9, 0xC33707D6 );
-    P( C, D, A, B,  3, 14, 0xF4D50D87 );
-    P( B, C, D, A,  8, 20, 0x455A14ED );
-    P( A, B, C, D, 13,  5, 0xA9E3E905 );
-    P( D, A, B, C,  2,  9, 0xFCEFA3F8 );
-    P( C, D, A, B,  7, 14, 0x676F02D9 );
-    P( B, C, D, A, 12, 20, 0x8D2A4C8A );
+    P( local.A, local.B, local.C, local.D,  1,  5, 0xF61E2562 );
+    P( local.D, local.A, local.B, local.C,  6,  9, 0xC040B340 );
+    P( local.C, local.D, local.A, local.B, 11, 14, 0x265E5A51 );
+    P( local.B, local.C, local.D, local.A,  0, 20, 0xE9B6C7AA );
+    P( local.A, local.B, local.C, local.D,  5,  5, 0xD62F105D );
+    P( local.D, local.A, local.B, local.C, 10,  9, 0x02441453 );
+    P( local.C, local.D, local.A, local.B, 15, 14, 0xD8A1E681 );
+    P( local.B, local.C, local.D, local.A,  4, 20, 0xE7D3FBC8 );
+    P( local.A, local.B, local.C, local.D,  9,  5, 0x21E1CDE6 );
+    P( local.D, local.A, local.B, local.C, 14,  9, 0xC33707D6 );
+    P( local.C, local.D, local.A, local.B,  3, 14, 0xF4D50D87 );
+    P( local.B, local.C, local.D, local.A,  8, 20, 0x455A14ED );
+    P( local.A, local.B, local.C, local.D, 13,  5, 0xA9E3E905 );
+    P( local.D, local.A, local.B, local.C,  2,  9, 0xFCEFA3F8 );
+    P( local.C, local.D, local.A, local.B,  7, 14, 0x676F02D9 );
+    P( local.B, local.C, local.D, local.A, 12, 20, 0x8D2A4C8A );
 
 #undef F
 
 #define F(x,y,z) ((x) ^ (y) ^ (z))
 
-    P( A, B, C, D,  5,  4, 0xFFFA3942 );
-    P( D, A, B, C,  8, 11, 0x8771F681 );
-    P( C, D, A, B, 11, 16, 0x6D9D6122 );
-    P( B, C, D, A, 14, 23, 0xFDE5380C );
-    P( A, B, C, D,  1,  4, 0xA4BEEA44 );
-    P( D, A, B, C,  4, 11, 0x4BDECFA9 );
-    P( C, D, A, B,  7, 16, 0xF6BB4B60 );
-    P( B, C, D, A, 10, 23, 0xBEBFBC70 );
-    P( A, B, C, D, 13,  4, 0x289B7EC6 );
-    P( D, A, B, C,  0, 11, 0xEAA127FA );
-    P( C, D, A, B,  3, 16, 0xD4EF3085 );
-    P( B, C, D, A,  6, 23, 0x04881D05 );
-    P( A, B, C, D,  9,  4, 0xD9D4D039 );
-    P( D, A, B, C, 12, 11, 0xE6DB99E5 );
-    P( C, D, A, B, 15, 16, 0x1FA27CF8 );
-    P( B, C, D, A,  2, 23, 0xC4AC5665 );
+    P( local.A, local.B, local.C, local.D,  5,  4, 0xFFFA3942 );
+    P( local.D, local.A, local.B, local.C,  8, 11, 0x8771F681 );
+    P( local.C, local.D, local.A, local.B, 11, 16, 0x6D9D6122 );
+    P( local.B, local.C, local.D, local.A, 14, 23, 0xFDE5380C );
+    P( local.A, local.B, local.C, local.D,  1,  4, 0xA4BEEA44 );
+    P( local.D, local.A, local.B, local.C,  4, 11, 0x4BDECFA9 );
+    P( local.C, local.D, local.A, local.B,  7, 16, 0xF6BB4B60 );
+    P( local.B, local.C, local.D, local.A, 10, 23, 0xBEBFBC70 );
+    P( local.A, local.B, local.C, local.D, 13,  4, 0x289B7EC6 );
+    P( local.D, local.A, local.B, local.C,  0, 11, 0xEAA127FA );
+    P( local.C, local.D, local.A, local.B,  3, 16, 0xD4EF3085 );
+    P( local.B, local.C, local.D, local.A,  6, 23, 0x04881D05 );
+    P( local.A, local.B, local.C, local.D,  9,  4, 0xD9D4D039 );
+    P( local.D, local.A, local.B, local.C, 12, 11, 0xE6DB99E5 );
+    P( local.C, local.D, local.A, local.B, 15, 16, 0x1FA27CF8 );
+    P( local.B, local.C, local.D, local.A,  2, 23, 0xC4AC5665 );
 
 #undef F
 
 #define F(x,y,z) ((y) ^ ((x) | ~(z)))
 
-    P( A, B, C, D,  0,  6, 0xF4292244 );
-    P( D, A, B, C,  7, 10, 0x432AFF97 );
-    P( C, D, A, B, 14, 15, 0xAB9423A7 );
-    P( B, C, D, A,  5, 21, 0xFC93A039 );
-    P( A, B, C, D, 12,  6, 0x655B59C3 );
-    P( D, A, B, C,  3, 10, 0x8F0CCC92 );
-    P( C, D, A, B, 10, 15, 0xFFEFF47D );
-    P( B, C, D, A,  1, 21, 0x85845DD1 );
-    P( A, B, C, D,  8,  6, 0x6FA87E4F );
-    P( D, A, B, C, 15, 10, 0xFE2CE6E0 );
-    P( C, D, A, B,  6, 15, 0xA3014314 );
-    P( B, C, D, A, 13, 21, 0x4E0811A1 );
-    P( A, B, C, D,  4,  6, 0xF7537E82 );
-    P( D, A, B, C, 11, 10, 0xBD3AF235 );
-    P( C, D, A, B,  2, 15, 0x2AD7D2BB );
-    P( B, C, D, A,  9, 21, 0xEB86D391 );
+    P( local.A, local.B, local.C, local.D,  0,  6, 0xF4292244 );
+    P( local.D, local.A, local.B, local.C,  7, 10, 0x432AFF97 );
+    P( local.C, local.D, local.A, local.B, 14, 15, 0xAB9423A7 );
+    P( local.B, local.C, local.D, local.A,  5, 21, 0xFC93A039 );
+    P( local.A, local.B, local.C, local.D, 12,  6, 0x655B59C3 );
+    P( local.D, local.A, local.B, local.C,  3, 10, 0x8F0CCC92 );
+    P( local.C, local.D, local.A, local.B, 10, 15, 0xFFEFF47D );
+    P( local.B, local.C, local.D, local.A,  1, 21, 0x85845DD1 );
+    P( local.A, local.B, local.C, local.D,  8,  6, 0x6FA87E4F );
+    P( local.D, local.A, local.B, local.C, 15, 10, 0xFE2CE6E0 );
+    P( local.C, local.D, local.A, local.B,  6, 15, 0xA3014314 );
+    P( local.B, local.C, local.D, local.A, 13, 21, 0x4E0811A1 );
+    P( local.A, local.B, local.C, local.D,  4,  6, 0xF7537E82 );
+    P( local.D, local.A, local.B, local.C, 11, 10, 0xBD3AF235 );
+    P( local.C, local.D, local.A, local.B,  2, 15, 0x2AD7D2BB );
+    P( local.B, local.C, local.D, local.A,  9, 21, 0xEB86D391 );
 
 #undef F
 
-    ctx->state[0] += A;
-    ctx->state[1] += B;
-    ctx->state[2] += C;
-    ctx->state[3] += D;
+    ctx->state[0] += local.A;
+    ctx->state[1] += local.B;
+    ctx->state[2] += local.C;
+    ctx->state[3] += local.D;
 
     /* Zeroise variables to clear sensitive data from memory. */
-    mbedtls_platform_zeroize( &X, sizeof( X ) );
-    mbedtls_platform_zeroize( &A, sizeof( A ) );
-    mbedtls_platform_zeroize( &B, sizeof( B ) );
-    mbedtls_platform_zeroize( &C, sizeof( C ) );
-    mbedtls_platform_zeroize( &D, sizeof( D ) );
+    mbedtls_platform_zeroize( &local, sizeof( local ) );
 
     return( 0 );
 }
diff --git a/library/ripemd160.c b/library/ripemd160.c
index b991b5689..d6ee933b2 100644
--- a/library/ripemd160.c
+++ b/library/ripemd160.c
@@ -147,30 +147,33 @@ void mbedtls_ripemd160_starts( mbedtls_ripemd160_context *ctx )
 int mbedtls_internal_ripemd160_process( mbedtls_ripemd160_context *ctx,
                                         const unsigned char data[64] )
 {
-    uint32_t A, B, C, D, E, Ap, Bp, Cp, Dp, Ep, X[16];
+    struct
+    {
+        uint32_t A, B, C, D, E, Ap, Bp, Cp, Dp, Ep, X[16];
+    } local;
 
-    GET_UINT32_LE( X[ 0], data,  0 );
-    GET_UINT32_LE( X[ 1], data,  4 );
-    GET_UINT32_LE( X[ 2], data,  8 );
-    GET_UINT32_LE( X[ 3], data, 12 );
-    GET_UINT32_LE( X[ 4], data, 16 );
-    GET_UINT32_LE( X[ 5], data, 20 );
-    GET_UINT32_LE( X[ 6], data, 24 );
-    GET_UINT32_LE( X[ 7], data, 28 );
-    GET_UINT32_LE( X[ 8], data, 32 );
-    GET_UINT32_LE( X[ 9], data, 36 );
-    GET_UINT32_LE( X[10], data, 40 );
-    GET_UINT32_LE( X[11], data, 44 );
-    GET_UINT32_LE( X[12], data, 48 );
-    GET_UINT32_LE( X[13], data, 52 );
-    GET_UINT32_LE( X[14], data, 56 );
-    GET_UINT32_LE( X[15], data, 60 );
+    GET_UINT32_LE( local.X[ 0], data,  0 );
+    GET_UINT32_LE( local.X[ 1], data,  4 );
+    GET_UINT32_LE( local.X[ 2], data,  8 );
+    GET_UINT32_LE( local.X[ 3], data, 12 );
+    GET_UINT32_LE( local.X[ 4], data, 16 );
+    GET_UINT32_LE( local.X[ 5], data, 20 );
+    GET_UINT32_LE( local.X[ 6], data, 24 );
+    GET_UINT32_LE( local.X[ 7], data, 28 );
+    GET_UINT32_LE( local.X[ 8], data, 32 );
+    GET_UINT32_LE( local.X[ 9], data, 36 );
+    GET_UINT32_LE( local.X[10], data, 40 );
+    GET_UINT32_LE( local.X[11], data, 44 );
+    GET_UINT32_LE( local.X[12], data, 48 );
+    GET_UINT32_LE( local.X[13], data, 52 );
+    GET_UINT32_LE( local.X[14], data, 56 );
+    GET_UINT32_LE( local.X[15], data, 60 );
 
-    A = Ap = ctx->state[0];
-    B = Bp = ctx->state[1];
-    C = Cp = ctx->state[2];
-    D = Dp = ctx->state[3];
-    E = Ep = ctx->state[4];
+    local.A = local.Ap = ctx->state[0];
+    local.B = local.Bp = ctx->state[1];
+    local.C = local.Cp = ctx->state[2];
+    local.D = local.Dp = ctx->state[3];
+    local.E = local.Ep = ctx->state[4];
 
 #define F1( x, y, z )   ( (x) ^ (y) ^ (z) )
 #define F2( x, y, z )   ( ( (x) & (y) ) | ( ~(x) & (z) ) )
@@ -180,12 +183,12 @@ int mbedtls_internal_ripemd160_process( mbedtls_ripemd160_context *ctx,
 
 #define S( x, n ) ( ( (x) << (n) ) | ( (x) >> (32 - (n)) ) )
 
-#define P( a, b, c, d, e, r, s, f, k )                \
-    do                                                \
-    {                                                 \
-        (a) += f( (b), (c), (d) ) + X[r] + (k);       \
-        (a) = S( (a), (s) ) + (e);                    \
-        (c) = S( (c), 10 );                           \
+#define P( a, b, c, d, e, r, s, f, k )                      \
+    do                                                      \
+    {                                                       \
+        (a) += f( (b), (c), (d) ) + local.X[r] + (k);       \
+        (a) = S( (a), (s) ) + (e);                          \
+        (c) = S( (c), 10 );                                 \
     } while( 0 )
 
 #define P2( a, b, c, d, e, r, s, rp, sp )                               \
@@ -200,22 +203,22 @@ int mbedtls_internal_ripemd160_process( mbedtls_ripemd160_context *ctx,
 #define K   0x00000000
 #define Fp  F5
 #define Kp  0x50A28BE6
-    P2( A, B, C, D, E,  0, 11,  5,  8 );
-    P2( E, A, B, C, D,  1, 14, 14,  9 );
-    P2( D, E, A, B, C,  2, 15,  7,  9 );
-    P2( C, D, E, A, B,  3, 12,  0, 11 );
-    P2( B, C, D, E, A,  4,  5,  9, 13 );
-    P2( A, B, C, D, E,  5,  8,  2, 15 );
-    P2( E, A, B, C, D,  6,  7, 11, 15 );
-    P2( D, E, A, B, C,  7,  9,  4,  5 );
-    P2( C, D, E, A, B,  8, 11, 13,  7 );
-    P2( B, C, D, E, A,  9, 13,  6,  7 );
-    P2( A, B, C, D, E, 10, 14, 15,  8 );
-    P2( E, A, B, C, D, 11, 15,  8, 11 );
-    P2( D, E, A, B, C, 12,  6,  1, 14 );
-    P2( C, D, E, A, B, 13,  7, 10, 14 );
-    P2( B, C, D, E, A, 14,  9,  3, 12 );
-    P2( A, B, C, D, E, 15,  8, 12,  6 );
+    P2( local.A, local.B, local.C, local.D, local.E,  0, 11,  5,  8 );
+    P2( local.E, local.A, local.B, local.C, local.D,  1, 14, 14,  9 );
+    P2( local.D, local.E, local.A, local.B, local.C,  2, 15,  7,  9 );
+    P2( local.C, local.D, local.E, local.A, local.B,  3, 12,  0, 11 );
+    P2( local.B, local.C, local.D, local.E, local.A,  4,  5,  9, 13 );
+    P2( local.A, local.B, local.C, local.D, local.E,  5,  8,  2, 15 );
+    P2( local.E, local.A, local.B, local.C, local.D,  6,  7, 11, 15 );
+    P2( local.D, local.E, local.A, local.B, local.C,  7,  9,  4,  5 );
+    P2( local.C, local.D, local.E, local.A, local.B,  8, 11, 13,  7 );
+    P2( local.B, local.C, local.D, local.E, local.A,  9, 13,  6,  7 );
+    P2( local.A, local.B, local.C, local.D, local.E, 10, 14, 15,  8 );
+    P2( local.E, local.A, local.B, local.C, local.D, 11, 15,  8, 11 );
+    P2( local.D, local.E, local.A, local.B, local.C, 12,  6,  1, 14 );
+    P2( local.C, local.D, local.E, local.A, local.B, 13,  7, 10, 14 );
+    P2( local.B, local.C, local.D, local.E, local.A, 14,  9,  3, 12 );
+    P2( local.A, local.B, local.C, local.D, local.E, 15,  8, 12,  6 );
 #undef F
 #undef K
 #undef Fp
@@ -225,22 +228,22 @@ int mbedtls_internal_ripemd160_process( mbedtls_ripemd160_context *ctx,
 #define K   0x5A827999
 #define Fp  F4
 #define Kp  0x5C4DD124
-    P2( E, A, B, C, D,  7,  7,  6,  9 );
-    P2( D, E, A, B, C,  4,  6, 11, 13 );
-    P2( C, D, E, A, B, 13,  8,  3, 15 );
-    P2( B, C, D, E, A,  1, 13,  7,  7 );
-    P2( A, B, C, D, E, 10, 11,  0, 12 );
-    P2( E, A, B, C, D,  6,  9, 13,  8 );
-    P2( D, E, A, B, C, 15,  7,  5,  9 );
-    P2( C, D, E, A, B,  3, 15, 10, 11 );
-    P2( B, C, D, E, A, 12,  7, 14,  7 );
-    P2( A, B, C, D, E,  0, 12, 15,  7 );
-    P2( E, A, B, C, D,  9, 15,  8, 12 );
-    P2( D, E, A, B, C,  5,  9, 12,  7 );
-    P2( C, D, E, A, B,  2, 11,  4,  6 );
-    P2( B, C, D, E, A, 14,  7,  9, 15 );
-    P2( A, B, C, D, E, 11, 13,  1, 13 );
-    P2( E, A, B, C, D,  8, 12,  2, 11 );
+    P2( local.E, local.A, local.B, local.C, local.D,  7,  7,  6,  9 );
+    P2( local.D, local.E, local.A, local.B, local.C,  4,  6, 11, 13 );
+    P2( local.C, local.D, local.E, local.A, local.B, 13,  8,  3, 15 );
+    P2( local.B, local.C, local.D, local.E, local.A,  1, 13,  7,  7 );
+    P2( local.A, local.B, local.C, local.D, local.E, 10, 11,  0, 12 );
+    P2( local.E, local.A, local.B, local.C, local.D,  6,  9, 13,  8 );
+    P2( local.D, local.E, local.A, local.B, local.C, 15,  7,  5,  9 );
+    P2( local.C, local.D, local.E, local.A, local.B,  3, 15, 10, 11 );
+    P2( local.B, local.C, local.D, local.E, local.A, 12,  7, 14,  7 );
+    P2( local.A, local.B, local.C, local.D, local.E,  0, 12, 15,  7 );
+    P2( local.E, local.A, local.B, local.C, local.D,  9, 15,  8, 12 );
+    P2( local.D, local.E, local.A, local.B, local.C,  5,  9, 12,  7 );
+    P2( local.C, local.D, local.E, local.A, local.B,  2, 11,  4,  6 );
+    P2( local.B, local.C, local.D, local.E, local.A, 14,  7,  9, 15 );
+    P2( local.A, local.B, local.C, local.D, local.E, 11, 13,  1, 13 );
+    P2( local.E, local.A, local.B, local.C, local.D,  8, 12,  2, 11 );
 #undef F
 #undef K
 #undef Fp
@@ -250,22 +253,22 @@ int mbedtls_internal_ripemd160_process( mbedtls_ripemd160_context *ctx,
 #define K   0x6ED9EBA1
 #define Fp  F3
 #define Kp  0x6D703EF3
-    P2( D, E, A, B, C,  3, 11, 15,  9 );
-    P2( C, D, E, A, B, 10, 13,  5,  7 );
-    P2( B, C, D, E, A, 14,  6,  1, 15 );
-    P2( A, B, C, D, E,  4,  7,  3, 11 );
-    P2( E, A, B, C, D,  9, 14,  7,  8 );
-    P2( D, E, A, B, C, 15,  9, 14,  6 );
-    P2( C, D, E, A, B,  8, 13,  6,  6 );
-    P2( B, C, D, E, A,  1, 15,  9, 14 );
-    P2( A, B, C, D, E,  2, 14, 11, 12 );
-    P2( E, A, B, C, D,  7,  8,  8, 13 );
-    P2( D, E, A, B, C,  0, 13, 12,  5 );
-    P2( C, D, E, A, B,  6,  6,  2, 14 );
-    P2( B, C, D, E, A, 13,  5, 10, 13 );
-    P2( A, B, C, D, E, 11, 12,  0, 13 );
-    P2( E, A, B, C, D,  5,  7,  4,  7 );
-    P2( D, E, A, B, C, 12,  5, 13,  5 );
+    P2( local.D, local.E, local.A, local.B, local.C,  3, 11, 15,  9 );
+    P2( local.C, local.D, local.E, local.A, local.B, 10, 13,  5,  7 );
+    P2( local.B, local.C, local.D, local.E, local.A, 14,  6,  1, 15 );
+    P2( local.A, local.B, local.C, local.D, local.E,  4,  7,  3, 11 );
+    P2( local.E, local.A, local.B, local.C, local.D,  9, 14,  7,  8 );
+    P2( local.D, local.E, local.A, local.B, local.C, 15,  9, 14,  6 );
+    P2( local.C, local.D, local.E, local.A, local.B,  8, 13,  6,  6 );
+    P2( local.B, local.C, local.D, local.E, local.A,  1, 15,  9, 14 );
+    P2( local.A, local.B, local.C, local.D, local.E,  2, 14, 11, 12 );
+    P2( local.E, local.A, local.B, local.C, local.D,  7,  8,  8, 13 );
+    P2( local.D, local.E, local.A, local.B, local.C,  0, 13, 12,  5 );
+    P2( local.C, local.D, local.E, local.A, local.B,  6,  6,  2, 14 );
+    P2( local.B, local.C, local.D, local.E, local.A, 13,  5, 10, 13 );
+    P2( local.A, local.B, local.C, local.D, local.E, 11, 12,  0, 13 );
+    P2( local.E, local.A, local.B, local.C, local.D,  5,  7,  4,  7 );
+    P2( local.D, local.E, local.A, local.B, local.C, 12,  5, 13,  5 );
 #undef F
 #undef K
 #undef Fp
@@ -275,22 +278,22 @@ int mbedtls_internal_ripemd160_process( mbedtls_ripemd160_context *ctx,
 #define K   0x8F1BBCDC
 #define Fp  F2
 #define Kp  0x7A6D76E9
-    P2( C, D, E, A, B,  1, 11,  8, 15 );
-    P2( B, C, D, E, A,  9, 12,  6,  5 );
-    P2( A, B, C, D, E, 11, 14,  4,  8 );
-    P2( E, A, B, C, D, 10, 15,  1, 11 );
-    P2( D, E, A, B, C,  0, 14,  3, 14 );
-    P2( C, D, E, A, B,  8, 15, 11, 14 );
-    P2( B, C, D, E, A, 12,  9, 15,  6 );
-    P2( A, B, C, D, E,  4,  8,  0, 14 );
-    P2( E, A, B, C, D, 13,  9,  5,  6 );
-    P2( D, E, A, B, C,  3, 14, 12,  9 );
-    P2( C, D, E, A, B,  7,  5,  2, 12 );
-    P2( B, C, D, E, A, 15,  6, 13,  9 );
-    P2( A, B, C, D, E, 14,  8,  9, 12 );
-    P2( E, A, B, C, D,  5,  6,  7,  5 );
-    P2( D, E, A, B, C,  6,  5, 10, 15 );
-    P2( C, D, E, A, B,  2, 12, 14,  8 );
+    P2( local.C, local.D, local.E, local.A, local.B,  1, 11,  8, 15 );
+    P2( local.B, local.C, local.D, local.E, local.A,  9, 12,  6,  5 );
+    P2( local.A, local.B, local.C, local.D, local.E, 11, 14,  4,  8 );
+    P2( local.E, local.A, local.B, local.C, local.D, 10, 15,  1, 11 );
+    P2( local.D, local.E, local.A, local.B, local.C,  0, 14,  3, 14 );
+    P2( local.C, local.D, local.E, local.A, local.B,  8, 15, 11, 14 );
+    P2( local.B, local.C, local.D, local.E, local.A, 12,  9, 15,  6 );
+    P2( local.A, local.B, local.C, local.D, local.E,  4,  8,  0, 14 );
+    P2( local.E, local.A, local.B, local.C, local.D, 13,  9,  5,  6 );
+    P2( local.D, local.E, local.A, local.B, local.C,  3, 14, 12,  9 );
+    P2( local.C, local.D, local.E, local.A, local.B,  7,  5,  2, 12 );
+    P2( local.B, local.C, local.D, local.E, local.A, 15,  6, 13,  9 );
+    P2( local.A, local.B, local.C, local.D, local.E, 14,  8,  9, 12 );
+    P2( local.E, local.A, local.B, local.C, local.D,  5,  6,  7,  5 );
+    P2( local.D, local.E, local.A, local.B, local.C,  6,  5, 10, 15 );
+    P2( local.C, local.D, local.E, local.A, local.B,  2, 12, 14,  8 );
 #undef F
 #undef K
 #undef Fp
@@ -300,46 +303,36 @@ int mbedtls_internal_ripemd160_process( mbedtls_ripemd160_context *ctx,
 #define K   0xA953FD4E
 #define Fp  F1
 #define Kp  0x00000000
-    P2( B, C, D, E, A,  4,  9, 12,  8 );
-    P2( A, B, C, D, E,  0, 15, 15,  5 );
-    P2( E, A, B, C, D,  5,  5, 10, 12 );
-    P2( D, E, A, B, C,  9, 11,  4,  9 );
-    P2( C, D, E, A, B,  7,  6,  1, 12 );
-    P2( B, C, D, E, A, 12,  8,  5,  5 );
-    P2( A, B, C, D, E,  2, 13,  8, 14 );
-    P2( E, A, B, C, D, 10, 12,  7,  6 );
-    P2( D, E, A, B, C, 14,  5,  6,  8 );
-    P2( C, D, E, A, B,  1, 12,  2, 13 );
-    P2( B, C, D, E, A,  3, 13, 13,  6 );
-    P2( A, B, C, D, E,  8, 14, 14,  5 );
-    P2( E, A, B, C, D, 11, 11,  0, 15 );
-    P2( D, E, A, B, C,  6,  8,  3, 13 );
-    P2( C, D, E, A, B, 15,  5,  9, 11 );
-    P2( B, C, D, E, A, 13,  6, 11, 11 );
+    P2( local.B, local.C, local.D, local.E, local.A,  4,  9, 12,  8 );
+    P2( local.A, local.B, local.C, local.D, local.E,  0, 15, 15,  5 );
+    P2( local.E, local.A, local.B, local.C, local.D,  5,  5, 10, 12 );
+    P2( local.D, local.E, local.A, local.B, local.C,  9, 11,  4,  9 );
+    P2( local.C, local.D, local.E, local.A, local.B,  7,  6,  1, 12 );
+    P2( local.B, local.C, local.D, local.E, local.A, 12,  8,  5,  5 );
+    P2( local.A, local.B, local.C, local.D, local.E,  2, 13,  8, 14 );
+    P2( local.E, local.A, local.B, local.C, local.D, 10, 12,  7,  6 );
+    P2( local.D, local.E, local.A, local.B, local.C, 14,  5,  6,  8 );
+    P2( local.C, local.D, local.E, local.A, local.B,  1, 12,  2, 13 );
+    P2( local.B, local.C, local.D, local.E, local.A,  3, 13, 13,  6 );
+    P2( local.A, local.B, local.C, local.D, local.E,  8, 14, 14,  5 );
+    P2( local.E, local.A, local.B, local.C, local.D, 11, 11,  0, 15 );
+    P2( local.D, local.E, local.A, local.B, local.C,  6,  8,  3, 13 );
+    P2( local.C, local.D, local.E, local.A, local.B, 15,  5,  9, 11 );
+    P2( local.B, local.C, local.D, local.E, local.A, 13,  6, 11, 11 );
 #undef F
 #undef K
 #undef Fp
 #undef Kp
 
-    C             = ctx->state[1] + C + Dp;
-    ctx->state[1] = ctx->state[2] + D + Ep;
-    ctx->state[2] = ctx->state[3] + E + Ap;
-    ctx->state[3] = ctx->state[4] + A + Bp;
-    ctx->state[4] = ctx->state[0] + B + Cp;
-    ctx->state[0] = C;
+    local.C       = ctx->state[1] + local.C + local.Dp;
+    ctx->state[1] = ctx->state[2] + local.D + local.Ep;
+    ctx->state[2] = ctx->state[3] + local.E + local.Ap;
+    ctx->state[3] = ctx->state[4] + local.A + local.Bp;
+    ctx->state[4] = ctx->state[0] + local.B + local.Cp;
+    ctx->state[0] = local.C;
 
     /* Zeroise variables to clear sensitive data from memory. */
-    mbedtls_platform_zeroize( &A, sizeof( A ) );
-    mbedtls_platform_zeroize( &B, sizeof( B ) );
-    mbedtls_platform_zeroize( &C, sizeof( C ) );
-    mbedtls_platform_zeroize( &D, sizeof( D ) );
-    mbedtls_platform_zeroize( &E, sizeof( E ) );
-    mbedtls_platform_zeroize( &Ap, sizeof( Ap ) );
-    mbedtls_platform_zeroize( &Bp, sizeof( Bp ) );
-    mbedtls_platform_zeroize( &Cp, sizeof( Cp ) );
-    mbedtls_platform_zeroize( &Dp, sizeof( Dp ) );
-    mbedtls_platform_zeroize( &Ep, sizeof( Ep ) );
-    mbedtls_platform_zeroize( &X, sizeof( X ) );
+    mbedtls_platform_zeroize( &local, sizeof( local ) );
 
     return( 0 );
 }
diff --git a/library/sha1.c b/library/sha1.c
index 4bb51982f..e99a5e863 100644
--- a/library/sha1.c
+++ b/library/sha1.c
@@ -155,35 +155,40 @@ void mbedtls_sha1_starts( mbedtls_sha1_context *ctx )
 int mbedtls_internal_sha1_process( mbedtls_sha1_context *ctx,
                                    const unsigned char data[64] )
 {
-    uint32_t temp, W[16], A, B, C, D, E;
+    struct
+    {
+        uint32_t temp, W[16], A, B, C, D, E;
+    } local;
 
     SHA1_VALIDATE_RET( ctx != NULL );
     SHA1_VALIDATE_RET( (const unsigned char *)data != NULL );
 
-    GET_UINT32_BE( W[ 0], data,  0 );
-    GET_UINT32_BE( W[ 1], data,  4 );
-    GET_UINT32_BE( W[ 2], data,  8 );
-    GET_UINT32_BE( W[ 3], data, 12 );
-    GET_UINT32_BE( W[ 4], data, 16 );
-    GET_UINT32_BE( W[ 5], data, 20 );
-    GET_UINT32_BE( W[ 6], data, 24 );
-    GET_UINT32_BE( W[ 7], data, 28 );
-    GET_UINT32_BE( W[ 8], data, 32 );
-    GET_UINT32_BE( W[ 9], data, 36 );
-    GET_UINT32_BE( W[10], data, 40 );
-    GET_UINT32_BE( W[11], data, 44 );
-    GET_UINT32_BE( W[12], data, 48 );
-    GET_UINT32_BE( W[13], data, 52 );
-    GET_UINT32_BE( W[14], data, 56 );
-    GET_UINT32_BE( W[15], data, 60 );
+    GET_UINT32_BE( local.W[ 0], data,  0 );
+    GET_UINT32_BE( local.W[ 1], data,  4 );
+    GET_UINT32_BE( local.W[ 2], data,  8 );
+    GET_UINT32_BE( local.W[ 3], data, 12 );
+    GET_UINT32_BE( local.W[ 4], data, 16 );
+    GET_UINT32_BE( local.W[ 5], data, 20 );
+    GET_UINT32_BE( local.W[ 6], data, 24 );
+    GET_UINT32_BE( local.W[ 7], data, 28 );
+    GET_UINT32_BE( local.W[ 8], data, 32 );
+    GET_UINT32_BE( local.W[ 9], data, 36 );
+    GET_UINT32_BE( local.W[10], data, 40 );
+    GET_UINT32_BE( local.W[11], data, 44 );
+    GET_UINT32_BE( local.W[12], data, 48 );
+    GET_UINT32_BE( local.W[13], data, 52 );
+    GET_UINT32_BE( local.W[14], data, 56 );
+    GET_UINT32_BE( local.W[15], data, 60 );
 
 #define S(x,n) (((x) << (n)) | (((x) & 0xFFFFFFFF) >> (32 - (n))))
 
 #define R(t)                                                    \
     (                                                           \
-        temp = W[( (t) -  3 ) & 0x0F] ^ W[( (t) - 8 ) & 0x0F] ^ \
-               W[( (t) - 14 ) & 0x0F] ^ W[  (t)       & 0x0F],  \
-        ( W[(t) & 0x0F] = S(temp,1) )                           \
+        local.temp = local.W[( (t) -  3 ) & 0x0F] ^             \
+                     local.W[( (t) -  8 ) & 0x0F] ^             \
+                     local.W[( (t) - 14 ) & 0x0F] ^             \
+                     local.W[  (t)        & 0x0F],              \
+        ( local.W[(t) & 0x0F] = S(local.temp,1) )               \
     )
 
 #define P(a,b,c,d,e,x)                                          \
@@ -193,35 +198,35 @@ int mbedtls_internal_sha1_process( mbedtls_sha1_context *ctx,
         (b) = S((b),30);                                        \
     } while( 0 )
 
-    A = ctx->state[0];
-    B = ctx->state[1];
-    C = ctx->state[2];
-    D = ctx->state[3];
-    E = ctx->state[4];
+    local.A = ctx->state[0];
+    local.B = ctx->state[1];
+    local.C = ctx->state[2];
+    local.D = ctx->state[3];
+    local.E = ctx->state[4];
 
 #define F(x,y,z) ((z) ^ ((x) & ((y) ^ (z))))
 #define K 0x5A827999
 
-    P( A, B, C, D, E, W[0]  );
-    P( E, A, B, C, D, W[1]  );
-    P( D, E, A, B, C, W[2]  );
-    P( C, D, E, A, B, W[3]  );
-    P( B, C, D, E, A, W[4]  );
-    P( A, B, C, D, E, W[5]  );
-    P( E, A, B, C, D, W[6]  );
-    P( D, E, A, B, C, W[7]  );
-    P( C, D, E, A, B, W[8]  );
-    P( B, C, D, E, A, W[9]  );
-    P( A, B, C, D, E, W[10] );
-    P( E, A, B, C, D, W[11] );
-    P( D, E, A, B, C, W[12] );
-    P( C, D, E, A, B, W[13] );
-    P( B, C, D, E, A, W[14] );
-    P( A, B, C, D, E, W[15] );
-    P( E, A, B, C, D, R(16) );
-    P( D, E, A, B, C, R(17) );
-    P( C, D, E, A, B, R(18) );
-    P( B, C, D, E, A, R(19) );
+    P( local.A, local.B, local.C, local.D, local.E, local.W[0]  );
+    P( local.E, local.A, local.B, local.C, local.D, local.W[1]  );
+    P( local.D, local.E, local.A, local.B, local.C, local.W[2]  );
+    P( local.C, local.D, local.E, local.A, local.B, local.W[3]  );
+    P( local.B, local.C, local.D, local.E, local.A, local.W[4]  );
+    P( local.A, local.B, local.C, local.D, local.E, local.W[5]  );
+    P( local.E, local.A, local.B, local.C, local.D, local.W[6]  );
+    P( local.D, local.E, local.A, local.B, local.C, local.W[7]  );
+    P( local.C, local.D, local.E, local.A, local.B, local.W[8]  );
+    P( local.B, local.C, local.D, local.E, local.A, local.W[9]  );
+    P( local.A, local.B, local.C, local.D, local.E, local.W[10] );
+    P( local.E, local.A, local.B, local.C, local.D, local.W[11] );
+    P( local.D, local.E, local.A, local.B, local.C, local.W[12] );
+    P( local.C, local.D, local.E, local.A, local.B, local.W[13] );
+    P( local.B, local.C, local.D, local.E, local.A, local.W[14] );
+    P( local.A, local.B, local.C, local.D, local.E, local.W[15] );
+    P( local.E, local.A, local.B, local.C, local.D, R(16) );
+    P( local.D, local.E, local.A, local.B, local.C, R(17) );
+    P( local.C, local.D, local.E, local.A, local.B, R(18) );
+    P( local.B, local.C, local.D, local.E, local.A, R(19) );
 
 #undef K
 #undef F
@@ -229,26 +234,26 @@ int mbedtls_internal_sha1_process( mbedtls_sha1_context *ctx,
 #define F(x,y,z) ((x) ^ (y) ^ (z))
 #define K 0x6ED9EBA1
 
-    P( A, B, C, D, E, R(20) );
-    P( E, A, B, C, D, R(21) );
-    P( D, E, A, B, C, R(22) );
-    P( C, D, E, A, B, R(23) );
-    P( B, C, D, E, A, R(24) );
-    P( A, B, C, D, E, R(25) );
-    P( E, A, B, C, D, R(26) );
-    P( D, E, A, B, C, R(27) );
-    P( C, D, E, A, B, R(28) );
-    P( B, C, D, E, A, R(29) );
-    P( A, B, C, D, E, R(30) );
-    P( E, A, B, C, D, R(31) );
-    P( D, E, A, B, C, R(32) );
-    P( C, D, E, A, B, R(33) );
-    P( B, C, D, E, A, R(34) );
-    P( A, B, C, D, E, R(35) );
-    P( E, A, B, C, D, R(36) );
-    P( D, E, A, B, C, R(37) );
-    P( C, D, E, A, B, R(38) );
-    P( B, C, D, E, A, R(39) );
+    P( local.A, local.B, local.C, local.D, local.E, R(20) );
+    P( local.E, local.A, local.B, local.C, local.D, R(21) );
+    P( local.D, local.E, local.A, local.B, local.C, R(22) );
+    P( local.C, local.D, local.E, local.A, local.B, R(23) );
+    P( local.B, local.C, local.D, local.E, local.A, R(24) );
+    P( local.A, local.B, local.C, local.D, local.E, R(25) );
+    P( local.E, local.A, local.B, local.C, local.D, R(26) );
+    P( local.D, local.E, local.A, local.B, local.C, R(27) );
+    P( local.C, local.D, local.E, local.A, local.B, R(28) );
+    P( local.B, local.C, local.D, local.E, local.A, R(29) );
+    P( local.A, local.B, local.C, local.D, local.E, R(30) );
+    P( local.E, local.A, local.B, local.C, local.D, R(31) );
+    P( local.D, local.E, local.A, local.B, local.C, R(32) );
+    P( local.C, local.D, local.E, local.A, local.B, R(33) );
+    P( local.B, local.C, local.D, local.E, local.A, R(34) );
+    P( local.A, local.B, local.C, local.D, local.E, R(35) );
+    P( local.E, local.A, local.B, local.C, local.D, R(36) );
+    P( local.D, local.E, local.A, local.B, local.C, R(37) );
+    P( local.C, local.D, local.E, local.A, local.B, R(38) );
+    P( local.B, local.C, local.D, local.E, local.A, R(39) );
 
 #undef K
 #undef F
@@ -256,26 +261,26 @@ int mbedtls_internal_sha1_process( mbedtls_sha1_context *ctx,
 #define F(x,y,z) (((x) & (y)) | ((z) & ((x) | (y))))
 #define K 0x8F1BBCDC
 
-    P( A, B, C, D, E, R(40) );
-    P( E, A, B, C, D, R(41) );
-    P( D, E, A, B, C, R(42) );
-    P( C, D, E, A, B, R(43) );
-    P( B, C, D, E, A, R(44) );
-    P( A, B, C, D, E, R(45) );
-    P( E, A, B, C, D, R(46) );
-    P( D, E, A, B, C, R(47) );
-    P( C, D, E, A, B, R(48) );
-    P( B, C, D, E, A, R(49) );
-    P( A, B, C, D, E, R(50) );
-    P( E, A, B, C, D, R(51) );
-    P( D, E, A, B, C, R(52) );
-    P( C, D, E, A, B, R(53) );
-    P( B, C, D, E, A, R(54) );
-    P( A, B, C, D, E, R(55) );
-    P( E, A, B, C, D, R(56) );
-    P( D, E, A, B, C, R(57) );
-    P( C, D, E, A, B, R(58) );
-    P( B, C, D, E, A, R(59) );
+    P( local.A, local.B, local.C, local.D, local.E, R(40) );
+    P( local.E, local.A, local.B, local.C, local.D, R(41) );
+    P( local.D, local.E, local.A, local.B, local.C, R(42) );
+    P( local.C, local.D, local.E, local.A, local.B, R(43) );
+    P( local.B, local.C, local.D, local.E, local.A, R(44) );
+    P( local.A, local.B, local.C, local.D, local.E, R(45) );
+    P( local.E, local.A, local.B, local.C, local.D, R(46) );
+    P( local.D, local.E, local.A, local.B, local.C, R(47) );
+    P( local.C, local.D, local.E, local.A, local.B, R(48) );
+    P( local.B, local.C, local.D, local.E, local.A, R(49) );
+    P( local.A, local.B, local.C, local.D, local.E, R(50) );
+    P( local.E, local.A, local.B, local.C, local.D, R(51) );
+    P( local.D, local.E, local.A, local.B, local.C, R(52) );
+    P( local.C, local.D, local.E, local.A, local.B, R(53) );
+    P( local.B, local.C, local.D, local.E, local.A, R(54) );
+    P( local.A, local.B, local.C, local.D, local.E, R(55) );
+    P( local.E, local.A, local.B, local.C, local.D, R(56) );
+    P( local.D, local.E, local.A, local.B, local.C, R(57) );
+    P( local.C, local.D, local.E, local.A, local.B, R(58) );
+    P( local.B, local.C, local.D, local.E, local.A, R(59) );
 
 #undef K
 #undef F
@@ -283,44 +288,38 @@ int mbedtls_internal_sha1_process( mbedtls_sha1_context *ctx,
 #define F(x,y,z) ((x) ^ (y) ^ (z))
 #define K 0xCA62C1D6
 
-    P( A, B, C, D, E, R(60) );
-    P( E, A, B, C, D, R(61) );
-    P( D, E, A, B, C, R(62) );
-    P( C, D, E, A, B, R(63) );
-    P( B, C, D, E, A, R(64) );
-    P( A, B, C, D, E, R(65) );
-    P( E, A, B, C, D, R(66) );
-    P( D, E, A, B, C, R(67) );
-    P( C, D, E, A, B, R(68) );
-    P( B, C, D, E, A, R(69) );
-    P( A, B, C, D, E, R(70) );
-    P( E, A, B, C, D, R(71) );
-    P( D, E, A, B, C, R(72) );
-    P( C, D, E, A, B, R(73) );
-    P( B, C, D, E, A, R(74) );
-    P( A, B, C, D, E, R(75) );
-    P( E, A, B, C, D, R(76) );
-    P( D, E, A, B, C, R(77) );
-    P( C, D, E, A, B, R(78) );
-    P( B, C, D, E, A, R(79) );
+    P( local.A, local.B, local.C, local.D, local.E, R(60) );
+    P( local.E, local.A, local.B, local.C, local.D, R(61) );
+    P( local.D, local.E, local.A, local.B, local.C, R(62) );
+    P( local.C, local.D, local.E, local.A, local.B, R(63) );
+    P( local.B, local.C, local.D, local.E, local.A, R(64) );
+    P( local.A, local.B, local.C, local.D, local.E, R(65) );
+    P( local.E, local.A, local.B, local.C, local.D, R(66) );
+    P( local.D, local.E, local.A, local.B, local.C, R(67) );
+    P( local.C, local.D, local.E, local.A, local.B, R(68) );
+    P( local.B, local.C, local.D, local.E, local.A, R(69) );
+    P( local.A, local.B, local.C, local.D, local.E, R(70) );
+    P( local.E, local.A, local.B, local.C, local.D, R(71) );
+    P( local.D, local.E, local.A, local.B, local.C, R(72) );
+    P( local.C, local.D, local.E, local.A, local.B, R(73) );
+    P( local.B, local.C, local.D, local.E, local.A, R(74) );
+    P( local.A, local.B, local.C, local.D, local.E, R(75) );
+    P( local.E, local.A, local.B, local.C, local.D, R(76) );
+    P( local.D, local.E, local.A, local.B, local.C, R(77) );
+    P( local.C, local.D, local.E, local.A, local.B, R(78) );
+    P( local.B, local.C, local.D, local.E, local.A, R(79) );
 
 #undef K
 #undef F
 
-    ctx->state[0] += A;
-    ctx->state[1] += B;
-    ctx->state[2] += C;
-    ctx->state[3] += D;
-    ctx->state[4] += E;
+    ctx->state[0] += local.A;
+    ctx->state[1] += local.B;
+    ctx->state[2] += local.C;
+    ctx->state[3] += local.D;
+    ctx->state[4] += local.E;
 
     /* Zeroise buffers and variables to clear sensitive data from memory. */
-    mbedtls_platform_zeroize( &A, sizeof( A ) );
-    mbedtls_platform_zeroize( &B, sizeof( B ) );
-    mbedtls_platform_zeroize( &C, sizeof( C ) );
-    mbedtls_platform_zeroize( &D, sizeof( D ) );
-    mbedtls_platform_zeroize( &E, sizeof( E ) );
-    mbedtls_platform_zeroize( &W, sizeof( W ) );
-    mbedtls_platform_zeroize( &temp, sizeof( temp ) );
+    mbedtls_platform_zeroize( &local, sizeof( local ) );
 
     return( 0 );
 }
diff --git a/library/sha256.c b/library/sha256.c
index 2decd08f0..75a8f8a2b 100644
--- a/library/sha256.c
+++ b/library/sha256.c
@@ -209,83 +209,104 @@ static const uint32_t K[] =
 #define F0(x,y,z) (((x) & (y)) | ((z) & ((x) | (y))))
 #define F1(x,y,z) ((z) ^ ((x) & ((y) ^ (z))))
 
-#define R(t)                                    \
-    (                                           \
-        W[t] = S1(W[(t) -  2]) + W[(t) -  7] +  \
-               S0(W[(t) - 15]) + W[(t) - 16]    \
+#define R(t)                                                        \
+    (                                                               \
+        local.W[t] = S1(local.W[(t) -  2]) + local.W[(t) -  7] +    \
+                     S0(local.W[(t) - 15]) + local.W[(t) - 16]      \
     )
 
-#define P(a,b,c,d,e,f,g,h,x,K)                          \
-    do                                                  \
-    {                                                   \
-        temp1 = (h) + S3(e) + F1((e),(f),(g)) + (K) + (x);      \
-        temp2 = S2(a) + F0((a),(b),(c));                        \
-        (d) += temp1; (h) = temp1 + temp2;              \
+#define P(a,b,c,d,e,f,g,h,x,K)                                      \
+    do                                                              \
+    {                                                               \
+        local.temp1 = (h) + S3(e) + F1((e),(f),(g)) + (K) + (x);    \
+        local.temp2 = S2(a) + F0((a),(b),(c));                      \
+        (d) += local.temp1; (h) = local.temp1 + local.temp2;        \
     } while( 0 )
 
 int mbedtls_internal_sha256_process( mbedtls_sha256_context *ctx,
                                 const unsigned char data[64] )
 {
-    uint32_t temp1, temp2, W[64];
-    uint32_t A[8];
+    struct
+    {
+        uint32_t temp1, temp2, W[64];
+        uint32_t A[8];
+    } local;
+
     unsigned int i;
 
     SHA256_VALIDATE_RET( ctx != NULL );
     SHA256_VALIDATE_RET( (const unsigned char *)data != NULL );
 
     for( i = 0; i < 8; i++ )
-        A[i] = ctx->state[i];
+        local.A[i] = ctx->state[i];
 
 #if defined(MBEDTLS_SHA256_SMALLER)
     for( i = 0; i < 64; i++ )
     {
         if( i < 16 )
-            GET_UINT32_BE( W[i], data, 4 * i );
+            GET_UINT32_BE( local.W[i], data, 4 * i );
         else
             R( i );
 
-        P( A[0], A[1], A[2], A[3], A[4], A[5], A[6], A[7], W[i], K[i] );
+        P( local.A[0], local.A[1], local.A[2], local.A[3], local.A[4],
+           local.A[5], local.A[6], local.A[7], local.W[i], K[i] );
 
-        temp1 = A[7]; A[7] = A[6]; A[6] = A[5]; A[5] = A[4]; A[4] = A[3];
-        A[3] = A[2]; A[2] = A[1]; A[1] = A[0]; A[0] = temp1;
+        local.temp1 = local.A[7]; local.A[7] = local.A[6];
+        local.A[6] = local.A[5]; local.A[5] = local.A[4];
+        local.A[4] = local.A[3]; local.A[3] = local.A[2];
+        local.A[2] = local.A[1]; local.A[1] = local.A[0];
+        local.A[0] = local.temp1;
     }
 #else /* MBEDTLS_SHA256_SMALLER */
     for( i = 0; i < 16; i++ )
-        GET_UINT32_BE( W[i], data, 4 * i );
+        GET_UINT32_BE( local.W[i], data, 4 * i );
 
     for( i = 0; i < 16; i += 8 )
     {
-        P( A[0], A[1], A[2], A[3], A[4], A[5], A[6], A[7], W[i+0], K[i+0] );
-        P( A[7], A[0], A[1], A[2], A[3], A[4], A[5], A[6], W[i+1], K[i+1] );
-        P( A[6], A[7], A[0], A[1], A[2], A[3], A[4], A[5], W[i+2], K[i+2] );
-        P( A[5], A[6], A[7], A[0], A[1], A[2], A[3], A[4], W[i+3], K[i+3] );
-        P( A[4], A[5], A[6], A[7], A[0], A[1], A[2], A[3], W[i+4], K[i+4] );
-        P( A[3], A[4], A[5], A[6], A[7], A[0], A[1], A[2], W[i+5], K[i+5] );
-        P( A[2], A[3], A[4], A[5], A[6], A[7], A[0], A[1], W[i+6], K[i+6] );
-        P( A[1], A[2], A[3], A[4], A[5], A[6], A[7], A[0], W[i+7], K[i+7] );
+        P( local.A[0], local.A[1], local.A[2], local.A[3], local.A[4],
+           local.A[5], local.A[6], local.A[7], local.W[i+0], K[i+0] );
+        P( local.A[7], local.A[0], local.A[1], local.A[2], local.A[3],
+           local.A[4], local.A[5], local.A[6], local.W[i+1], K[i+1] );
+        P( local.A[6], local.A[7], local.A[0], local.A[1], local.A[2],
+           local.A[3], local.A[4], local.A[5], local.W[i+2], K[i+2] );
+        P( local.A[5], local.A[6], local.A[7], local.A[0], local.A[1],
+           local.A[2], local.A[3], local.A[4], local.W[i+3], K[i+3] );
+        P( local.A[4], local.A[5], local.A[6], local.A[7], local.A[0],
+           local.A[1], local.A[2], local.A[3], local.W[i+4], K[i+4] );
+        P( local.A[3], local.A[4], local.A[5], local.A[6], local.A[7],
+           local.A[0], local.A[1], local.A[2], local.W[i+5], K[i+5] );
+        P( local.A[2], local.A[3], local.A[4], local.A[5], local.A[6],
+           local.A[7], local.A[0], local.A[1], local.W[i+6], K[i+6] );
+        P( local.A[1], local.A[2], local.A[3], local.A[4], local.A[5],
+           local.A[6], local.A[7], local.A[0], local.W[i+7], K[i+7] );
     }
 
     for( i = 16; i < 64; i += 8 )
     {
-        P( A[0], A[1], A[2], A[3], A[4], A[5], A[6], A[7], R(i+0), K[i+0] );
-        P( A[7], A[0], A[1], A[2], A[3], A[4], A[5], A[6], R(i+1), K[i+1] );
-        P( A[6], A[7], A[0], A[1], A[2], A[3], A[4], A[5], R(i+2), K[i+2] );
-        P( A[5], A[6], A[7], A[0], A[1], A[2], A[3], A[4], R(i+3), K[i+3] );
-        P( A[4], A[5], A[6], A[7], A[0], A[1], A[2], A[3], R(i+4), K[i+4] );
-        P( A[3], A[4], A[5], A[6], A[7], A[0], A[1], A[2], R(i+5), K[i+5] );
-        P( A[2], A[3], A[4], A[5], A[6], A[7], A[0], A[1], R(i+6), K[i+6] );
-        P( A[1], A[2], A[3], A[4], A[5], A[6], A[7], A[0], R(i+7), K[i+7] );
+        P( local.A[0], local.A[1], local.A[2], local.A[3], local.A[4],
+           local.A[5], local.A[6], local.A[7], R(i+0), K[i+0] );
+        P( local.A[7], local.A[0], local.A[1], local.A[2], local.A[3],
+           local.A[4], local.A[5], local.A[6], R(i+1), K[i+1] );
+        P( local.A[6], local.A[7], local.A[0], local.A[1], local.A[2],
+           local.A[3], local.A[4], local.A[5], R(i+2), K[i+2] );
+        P( local.A[5], local.A[6], local.A[7], local.A[0], local.A[1],
+           local.A[2], local.A[3], local.A[4], R(i+3), K[i+3] );
+        P( local.A[4], local.A[5], local.A[6], local.A[7], local.A[0],
+           local.A[1], local.A[2], local.A[3], R(i+4), K[i+4] );
+        P( local.A[3], local.A[4], local.A[5], local.A[6], local.A[7],
+           local.A[0], local.A[1], local.A[2], R(i+5), K[i+5] );
+        P( local.A[2], local.A[3], local.A[4], local.A[5], local.A[6],
+           local.A[7], local.A[0], local.A[1], R(i+6), K[i+6] );
+        P( local.A[1], local.A[2], local.A[3], local.A[4], local.A[5],
+           local.A[6], local.A[7], local.A[0], R(i+7), K[i+7] );
     }
 #endif /* MBEDTLS_SHA256_SMALLER */
 
     for( i = 0; i < 8; i++ )
-        ctx->state[i] += A[i];
+        ctx->state[i] += local.A[i];
 
     /* Zeroise buffers and variables to clear sensitive data from memory. */
-    mbedtls_platform_zeroize( &A, sizeof( A ) );
-    mbedtls_platform_zeroize( &W, sizeof( W ) );
-    mbedtls_platform_zeroize( &temp1, sizeof( temp1 ) );
-    mbedtls_platform_zeroize( &temp2, sizeof( temp2 ) );
+    mbedtls_platform_zeroize( &local, sizeof( local ) );
 
     return( 0 );
 }
diff --git a/library/sha512.c b/library/sha512.c
index 37a01dd7b..986037ab7 100644
--- a/library/sha512.c
+++ b/library/sha512.c
@@ -243,8 +243,11 @@ int mbedtls_internal_sha512_process( mbedtls_sha512_context *ctx,
                                      const unsigned char data[128] )
 {
     int i;
-    uint64_t temp1, temp2, W[80];
-    uint64_t A, B, C, D, E, F, G, H;
+    struct
+    {
+        uint64_t temp1, temp2, W[80];
+        uint64_t A, B, C, D, E, F, G, H;
+    } local;
 
     SHA512_VALIDATE_RET( ctx != NULL );
     SHA512_VALIDATE_RET( (const unsigned char *)data != NULL );
@@ -261,69 +264,67 @@ int mbedtls_internal_sha512_process( mbedtls_sha512_context *ctx,
 #define F0(x,y,z) (((x) & (y)) | ((z) & ((x) | (y))))
 #define F1(x,y,z) ((z) ^ ((x) & ((y) ^ (z))))
 
-#define P(a,b,c,d,e,f,g,h,x,K)                                  \
-    do                                                          \
-    {                                                           \
-        temp1 = (h) + S3(e) + F1((e),(f),(g)) + (K) + (x);      \
-        temp2 = S2(a) + F0((a),(b),(c));                        \
-        (d) += temp1; (h) = temp1 + temp2;                      \
+#define P(a,b,c,d,e,f,g,h,x,K)                                      \
+    do                                                              \
+    {                                                               \
+        local.temp1 = (h) + S3(e) + F1((e),(f),(g)) + (K) + (x);    \
+        local.temp2 = S2(a) + F0((a),(b),(c));                      \
+        (d) += local.temp1; (h) = local.temp1 + local.temp2;        \
     } while( 0 )
 
     for( i = 0; i < 16; i++ )
     {
-        GET_UINT64_BE( W[i], data, i << 3 );
+        GET_UINT64_BE( local.W[i], data, i << 3 );
     }
 
     for( ; i < 80; i++ )
     {
-        W[i] = S1(W[i -  2]) + W[i -  7] +
-               S0(W[i - 15]) + W[i - 16];
+        local.W[i] = S1(local.W[i -  2]) + local.W[i -  7] +
+                     S0(local.W[i - 15]) + local.W[i - 16];
     }
 
-    A = ctx->state[0];
-    B = ctx->state[1];
-    C = ctx->state[2];
-    D = ctx->state[3];
-    E = ctx->state[4];
-    F = ctx->state[5];
-    G = ctx->state[6];
-    H = ctx->state[7];
+    local.A = ctx->state[0];
+    local.B = ctx->state[1];
+    local.C = ctx->state[2];
+    local.D = ctx->state[3];
+    local.E = ctx->state[4];
+    local.F = ctx->state[5];
+    local.G = ctx->state[6];
+    local.H = ctx->state[7];
     i = 0;
 
     do
     {
-        P( A, B, C, D, E, F, G, H, W[i], K[i] ); i++;
-        P( H, A, B, C, D, E, F, G, W[i], K[i] ); i++;
-        P( G, H, A, B, C, D, E, F, W[i], K[i] ); i++;
-        P( F, G, H, A, B, C, D, E, W[i], K[i] ); i++;
-        P( E, F, G, H, A, B, C, D, W[i], K[i] ); i++;
-        P( D, E, F, G, H, A, B, C, W[i], K[i] ); i++;
-        P( C, D, E, F, G, H, A, B, W[i], K[i] ); i++;
-        P( B, C, D, E, F, G, H, A, W[i], K[i] ); i++;
+        P( local.A, local.B, local.C, local.D, local.E,
+           local.F, local.G, local.H, local.W[i], K[i] ); i++;
+        P( local.H, local.A, local.B, local.C, local.D,
+           local.E, local.F, local.G, local.W[i], K[i] ); i++;
+        P( local.G, local.H, local.A, local.B, local.C,
+           local.D, local.E, local.F, local.W[i], K[i] ); i++;
+        P( local.F, local.G, local.H, local.A, local.B,
+           local.C, local.D, local.E, local.W[i], K[i] ); i++;
+        P( local.E, local.F, local.G, local.H, local.A,
+           local.B, local.C, local.D, local.W[i], K[i] ); i++;
+        P( local.D, local.E, local.F, local.G, local.H,
+           local.A, local.B, local.C, local.W[i], K[i] ); i++;
+        P( local.C, local.D, local.E, local.F, local.G,
+           local.H, local.A, local.B, local.W[i], K[i] ); i++;
+        P( local.B, local.C, local.D, local.E, local.F,
+           local.G, local.H, local.A, local.W[i], K[i] ); i++;
     }
     while( i < 80 );
 
-    ctx->state[0] += A;
-    ctx->state[1] += B;
-    ctx->state[2] += C;
-    ctx->state[3] += D;
-    ctx->state[4] += E;
-    ctx->state[5] += F;
-    ctx->state[6] += G;
-    ctx->state[7] += H;
+    ctx->state[0] += local.A;
+    ctx->state[1] += local.B;
+    ctx->state[2] += local.C;
+    ctx->state[3] += local.D;
+    ctx->state[4] += local.E;
+    ctx->state[5] += local.F;
+    ctx->state[6] += local.G;
+    ctx->state[7] += local.H;
 
     /* Zeroise buffers and variables to clear sensitive data from memory. */
-    mbedtls_platform_zeroize( &A, sizeof( A ) );
-    mbedtls_platform_zeroize( &B, sizeof( B ) );
-    mbedtls_platform_zeroize( &C, sizeof( C ) );
-    mbedtls_platform_zeroize( &D, sizeof( D ) );
-    mbedtls_platform_zeroize( &E, sizeof( E ) );
-    mbedtls_platform_zeroize( &F, sizeof( F ) );
-    mbedtls_platform_zeroize( &G, sizeof( G ) );
-    mbedtls_platform_zeroize( &H, sizeof( H ) );
-    mbedtls_platform_zeroize( &W, sizeof( W ) );
-    mbedtls_platform_zeroize( &temp1, sizeof( temp1 ) );
-    mbedtls_platform_zeroize( &temp2, sizeof( temp2 ) );
+    mbedtls_platform_zeroize( &local, sizeof( local ) );
 
     return( 0 );
 }

From 2f78062e7542100cc5f7a832f1b509af121ac167 Mon Sep 17 00:00:00 2001
From: Gilles Peskine <Gilles.Peskine@arm.com>
Date: Wed, 25 Nov 2020 15:37:20 +0100
Subject: [PATCH 05/19] Test mbedtls_mpi_fill_random

Positive tests: test that the RNG has the expected size, given that we
know how many leading zeros it has because we know how the function
consumes bytes and when the test RNG produces null bytes.

Negative tests: test that if the RNG is willing to emit less than the
number of wanted bytes, the function fails.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
---
 tests/suites/test_suite_mpi.data     | 42 ++++++++++++++++++++++++
 tests/suites/test_suite_mpi.function | 48 ++++++++++++++++++++++++++++
 2 files changed, 90 insertions(+)

diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index 00926ff97..a3e4eb974 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -929,6 +929,48 @@ mbedtls_mpi_set_bit:16:"00":32:1:16:"0100000000":0
 Test bit set (Invalid bit value)
 mbedtls_mpi_set_bit:16:"00":5:2:16:"00":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
+Fill random: 0 bytes
+mpi_fill_random:0:0:0
+
+Fill random: 1 byte, good
+mpi_fill_random:1:1:0
+
+Fill random: 2 bytes, good, no leading zero
+mpi_fill_random:2:2:0
+
+Fill random: 2 bytes, good, 1 leading zero
+mpi_fill_random:2:256:0
+
+Fill random: MAX_SIZE - 7, good
+mpi_fill_random:MBEDTLS_MPI_MAX_SIZE - 7:MBEDTLS_MPI_MAX_SIZE - 7:0
+
+Fill random: MAX_SIZE, good
+mpi_fill_random:MBEDTLS_MPI_MAX_SIZE:MBEDTLS_MPI_MAX_SIZE:0
+
+Fill random: 1 byte, RNG failure
+mpi_fill_random:1:0:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
+Fill random: 2 bytes, RNG failure after 1 byte
+mpi_fill_random:2:1:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
+Fill random: 4 bytes, RNG failure after 3 bytes
+mpi_fill_random:4:3:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
+Fill random: 8 bytes, RNG failure after 7 bytes
+mpi_fill_random:8:7:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
+Fill random: 16 bytes, RNG failure after 1 bytes
+mpi_fill_random:16:1:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
+Fill random: 16 bytes, RNG failure after 8 bytes
+mpi_fill_random:16:8:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
+Fill random: 16 bytes, RNG failure after 15 bytes
+mpi_fill_random:16:15:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
+Fill random: MAX_SIZE bytes, RNG failure after MAX_SIZE-1 bytes
+mpi_fill_random:MBEDTLS_MPI_MAX_SIZE:MBEDTLS_MPI_MAX_SIZE-1:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
+
 MPI Selftest
 depends_on:MBEDTLS_SELF_TEST
 mpi_selftest:
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index f2702f12b..a6d9effc2 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -1,5 +1,6 @@
 /* BEGIN_HEADER */
 #include "mbedtls/bignum.h"
+#include "mbedtls/entropy.h"
 
 typedef struct mbedtls_test_mpi_random
 {
@@ -43,6 +44,22 @@ int mbedtls_test_mpi_miller_rabin_determinizer( void* state,
 
     return( 0 );
 }
+
+/* Random generator that is told how many bytes to return. */
+static int f_rng_bytes_left( void *state, unsigned char *buf, size_t len )
+{
+    size_t *bytes_left = state;
+    size_t i;
+    for( i = 0; i < len; i++ )
+    {
+        if( *bytes_left == 0 )
+            return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
+        buf[i] = *bytes_left & 0xff;
+        --( *bytes_left );
+    }
+    return( 0 );
+}
+
 /* END_HEADER */
 
 /* BEGIN_DEPENDENCIES
@@ -1251,6 +1268,37 @@ exit:
 }
 /* END_CASE */
 
+/* BEGIN_CASE */
+void mpi_fill_random( int wanted_bytes, int rng_bytes, int expected_ret )
+{
+    mbedtls_mpi X;
+    int ret;
+    size_t bytes_left = rng_bytes;
+    mbedtls_mpi_init( &X );
+
+    ret = mbedtls_mpi_fill_random( &X, wanted_bytes,
+                                   f_rng_bytes_left, &bytes_left );
+    TEST_ASSERT( ret == expected_ret );
+
+    if( expected_ret == 0 )
+    {
+        /* mbedtls_mpi_fill_random is documented to use bytes from the RNG
+         * as a big-endian representation of the number. We know when
+         * our RNG function returns null bytes, so we know how many
+         * leading zero bytes the number has. */
+        size_t leading_zeros = 0;
+        if( wanted_bytes > 0 && rng_bytes % 256 == 0 )
+            leading_zeros = 1;
+        TEST_ASSERT( mbedtls_mpi_size( &X ) + leading_zeros ==
+                     (size_t) wanted_bytes );
+        TEST_ASSERT( (int) bytes_left == rng_bytes - wanted_bytes );
+    }
+
+exit:
+    mbedtls_mpi_free( &X );
+}
+/* END_CASE */
+
 /* BEGIN_CASE depends_on:MBEDTLS_SELF_TEST */
 void mpi_selftest(  )
 {

From 05251147521930cbd3ac2b415d7d25404230fd98 Mon Sep 17 00:00:00 2001
From: Gilles Peskine <Gilles.Peskine@arm.com>
Date: Wed, 25 Nov 2020 16:15:14 +0100
Subject: [PATCH 06/19] Handle random generator failure in
 mbedtls_mpi_fill_random()

Discuss the impact in a changelog entry.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
---
 ChangeLog.d/mpi_fill_random-rng_failure.txt | 8 ++++++++
 library/bignum.c                            | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)
 create mode 100644 ChangeLog.d/mpi_fill_random-rng_failure.txt

diff --git a/ChangeLog.d/mpi_fill_random-rng_failure.txt b/ChangeLog.d/mpi_fill_random-rng_failure.txt
new file mode 100644
index 000000000..8addf180c
--- /dev/null
+++ b/ChangeLog.d/mpi_fill_random-rng_failure.txt
@@ -0,0 +1,8 @@
+Security
+   * A failure of the random generator was ignored in mbedtls_mpi_fill_random(),
+     which is how most uses of randomization in asymmetric cryptography
+     (including key generation, intermediate value randomization and blinding)
+     are implemented. This could cause failures or the silent use of non-random
+     values. A random generator can fail if it needs reseeding and cannot not
+     obtain entropy, or due to an internal failure (which, for Mbed TLS's own
+     CTR_DRBG or HMAC_DRBG, can only happen due to a misconfiguration).
diff --git a/library/bignum.c b/library/bignum.c
index dfe976d64..0d363e6e0 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -2334,7 +2334,7 @@ int mbedtls_mpi_fill_random( mbedtls_mpi *X, size_t size,
     MBEDTLS_MPI_CHK( mbedtls_mpi_lset( X, 0 ) );
 
     Xp = (unsigned char*) X->p;
-    f_rng( p_rng, Xp + overhead, size );
+    MBEDTLS_MPI_CHK( f_rng( p_rng, Xp + overhead, size ) );
 
     mpi_bigendian_to_host( X->p, limbs );
 

From 027b6016900fb0bdbc3ab8f1dd6ac2577ab9a851 Mon Sep 17 00:00:00 2001
From: Paul Elliott <paul.elliott@arm.com>
Date: Tue, 24 Nov 2020 17:30:18 +0000
Subject: [PATCH 07/19] Add tag check to cert algorithm check

Add missing tag check for algorithm parameters when comparing the
signature in the description part of the cert against the actual
signature whilst loading a certificate. This was found by a
certificate (created by fuzzing) that openssl would not verify, but
mbedtls would.

Regression test added (one of the client certs modified accordingly)

Signed-off-by: Paul Elliott <paul.elliott@arm.com>
---
 .../x509-add-tag-check-to-algorithm-params        |  11 +++++++++++
 library/x509_crt.c                                |   1 +
 tests/data_files/Makefile                         |   6 +++++-
 tests/data_files/cli-rsa-sha256-badalg.crt.der    | Bin 0 -> 835 bytes
 tests/suites/test_suite_x509parse.data            |   4 ++++
 5 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 ChangeLog.d/x509-add-tag-check-to-algorithm-params
 create mode 100644 tests/data_files/cli-rsa-sha256-badalg.crt.der

diff --git a/ChangeLog.d/x509-add-tag-check-to-algorithm-params b/ChangeLog.d/x509-add-tag-check-to-algorithm-params
new file mode 100644
index 000000000..f2c72b0ec
--- /dev/null
+++ b/ChangeLog.d/x509-add-tag-check-to-algorithm-params
@@ -0,0 +1,11 @@
+Security
+   * Fix a compliance issue whereby we were not checking the tag on the
+     algorithm parameters (only the size) when comparing the signature in the
+     description part of the cert to the real signature. This meant that a
+     NULL algorithm parameters entry would look identical to an array of REAL
+     (size zero) to the library and thus the certificate would be considered
+     valid. However, if the parameters do not match in *any* way then the
+     certificate should be considered invalid, and indeed OpenSSL marks these
+     certs as invalid when mbedtls did not.
+     Many thanks to guidovranken who found this issue via differential fuzzing
+     and reported it in #3629.
diff --git a/library/x509_crt.c b/library/x509_crt.c
index d519a3fa1..fd89135b9 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -1088,6 +1088,7 @@ static int x509_crt_parse_der_core( mbedtls_x509_crt *crt, const unsigned char *
 
     if( crt->sig_oid.len != sig_oid2.len ||
         memcmp( crt->sig_oid.p, sig_oid2.p, crt->sig_oid.len ) != 0 ||
+        sig_params1.tag != sig_params2.tag ||
         sig_params1.len != sig_params2.len ||
         ( sig_params1.len != 0 &&
           memcmp( sig_params1.p, sig_params2.p, sig_params1.len ) != 0 ) )
diff --git a/tests/data_files/Makefile b/tests/data_files/Makefile
index 0429bddd1..6c9e24513 100644
--- a/tests/data_files/Makefile
+++ b/tests/data_files/Makefile
@@ -155,7 +155,11 @@ cli-rsa-sha256.crt.der: cli-rsa-sha256.crt
 	$(OPENSSL) x509 -in $< -out $@ -inform PEM -outform DER
 all_final += cli-rsa-sha256.crt.der
 
- cli-rsa.key.der: $(cli_crt_key_file_rsa)
+cli-rsa-sha256-badalg.crt.der: cli-rsa-sha256.crt.der
+	hexdump -ve '1/1 "%.2X"' $< | sed "s/06092A864886F70D01010B0500/06092A864886F70D01010B0900/2" | xxd -r -p > $@
+all_final += cli-rsa-sha256-badalg.crt.der
+
+cli-rsa.key.der: $(cli_crt_key_file_rsa)
 	$(OPENSSL) pkey -in $< -out $@ -inform PEM -outform DER
 all_final += cli-rsa.key.der
 
diff --git a/tests/data_files/cli-rsa-sha256-badalg.crt.der b/tests/data_files/cli-rsa-sha256-badalg.crt.der
new file mode 100644
index 0000000000000000000000000000000000000000..c40ba2a44b4c7a6d511eb40815cd9be1729619ce
GIT binary patch
literal 835
zcmXqLVzxJEVp3ng%*4pV#K>a6%f_kI=F#?@mywa1mBGN;klTQhjX9KsO_<5g$57CK
zAH?C};RwjjNh}Hu_A!(+5C;h{^9aC%6hcyqOB9?P4dldm4J{3f3=IrTOiT>SqQrTP
zkhumn1PzxmkboF22shk0Co?s#M8U|QiBSpJwT!F`%uS5^3_x)%rY1&4h7%=6&g}fT
zweqFwO_78RwYw*O%9fjNyq34W%O))K=^dAwXVO~Pul`Wq;AMItc^+4u^!8gH>Q=ww
z5t!WODPi(?h1R9;uX<PX%QagPeVYRMmrwO5_?qXt>8kMIOHyy2Ilpoed0q1Az+3q%
z;eIPWuXuau!9jyU10#d0m%njb2=jOA`xO7vHhp4;fu7T*`?bHH@|6F7V|bvVfB&KS
zQ)_b+ul3&S&g#p5F#Cr<*qP0J!lKViSkjKa`)S6PHT4_kEVlG7sf9mIE!n90;Ga#m
zDNFjU2mWQPf9n63Wp90XR+l-+Z?i4K`SoQBGQ*m)F0HuoJfQH|Rx{Re*4*k7PmcWc
zxvCh?#LURRxY*ag8ytbM!YoV%3<k2m;FRTK5n~Z4T*y#d<e(o?7H9k?sDIDLyV-7v
z2J#?jWflnou?CSXQBRg`zIQ3;+s>=Yrt-hG+jIQyf8+q?<^%;eBSV~e{?&V$dI3qA
ziOk<;ojG|Rw!vKC#I4SwD_JLsUp&FP=~`xyU)?*_k`$9|mMJl(J|{Ny`A)d;;D_s!
zCL1Qt6}#MJeSd7<8`Jsy{pqBx&tdxO#f{yB8HCp<{aShJ#NW&1sqZ4Dlsx(BzfgVI
zhKt;rZ-{NXo}R3Gr~0A9&0h7l(n{~|n+ZNT!N7O?<*^+%yzNaL|Noih>0jGt@19{S
z-t5A^epw{fN~6<}|L(@;bt~;?oFF!li={H@zc<Ur7?anT=iZ;r+h*+$dP?Pxood0m
z5^cWuhni+7Sd=eR>pC^Ry|n!Cxzsm>0;Z==`%5~%Hn?y~*Z!27Na9QbN29Ig$@$X(
Db~{is

literal 0
HcmV?d00001

diff --git a/tests/suites/test_suite_x509parse.data b/tests/suites/test_suite_x509parse.data
index 28ba79bff..14ba0ded1 100644
--- a/tests/suites/test_suite_x509parse.data
+++ b/tests/suites/test_suite_x509parse.data
@@ -1876,6 +1876,10 @@ X509 File parse (trailing spaces, OK)
 depends_on:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C:MBEDTLS_RSA_C
 x509parse_crt_file:"data_files/server7_trailing_space.crt":0
 
+X509 File parse (Algorithm Params Tag mismatch)
+depends_on:MBEDTLS_SHA256_C:MBEDTLS_RSA_C
+x509parse_crt_file:"data_files/cli-rsa-sha256-badalg.crt.der":MBEDTLS_ERR_X509_SIG_MISMATCH
+
 X509 Get time (UTC no issues)
 depends_on:MBEDTLS_X509_USE_C
 x509_get_time:MBEDTLS_ASN1_UTC_TIME:"500101000000Z":0:1950:1:1:0:0:0

From ad59a2a4a737ee8d1476015b14d4dcada12fc36b Mon Sep 17 00:00:00 2001
From: Chris Jones <christopher.jones@arm.com>
Date: Wed, 25 Nov 2020 15:12:39 +0000
Subject: [PATCH 08/19] Fix potential DoS by limiting number sizes in
 exponentiation

Check that the exponent and modulus is below `MBEDTLS_MPI_MAX_BITS` before
performing a time expensive operation (modular exponentiation). This prevents
a potential DoS from Diffie-Hellman computations with extremely
large key sizes.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
---
 library/bignum.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/library/bignum.c b/library/bignum.c
index dfe976d64..a9d51944e 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -2058,6 +2058,10 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A,
     if( mbedtls_mpi_cmp_int( E, 0 ) < 0 )
         return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
 
+    if( mbedtls_mpi_bitlen( E ) > MBEDTLS_MPI_MAX_BITS ||
+        mbedtls_mpi_bitlen( N ) > MBEDTLS_MPI_MAX_BITS )
+        return ( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
+
     /*
      * Init temps and window size
      */

From 63d19c0586d0a5776993a079cfc99eb170dd318b Mon Sep 17 00:00:00 2001
From: Chris Jones <christopher.jones@arm.com>
Date: Thu, 26 Nov 2020 11:21:53 +0000
Subject: [PATCH 09/19] Test that overly large Diffie-Hellman keys are rejected

Add a test case to ensure `mbedtls_mpi_exp_mod` fails when using a key size
larger than MBEDTLS_MPI_MAX_SIZE.
Add a test case to ensure that Diffie-Hellman operations fail when using a key
size larger than MBEDTLS_MPI_MAX_SIZE.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
---
 tests/suites/test_suite_dhm.data | 7 +++++--
 tests/suites/test_suite_mpi.data | 5 ++++-
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/tests/suites/test_suite_dhm.data b/tests/suites/test_suite_dhm.data
index edebce087..351ec840a 100644
--- a/tests/suites/test_suite_dhm.data
+++ b/tests/suites/test_suite_dhm.data
@@ -22,10 +22,13 @@ dhm_do_dhm:10:"3":10:"5":MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED
 Diffie-Hellman zero modulus
 dhm_do_dhm:10:"0":10:"5":MBEDTLS_ERR_DHM_BAD_INPUT_DATA
 
-Diffie-Hellman load parameters from file
+Diffie-Hellman huge modulus
+dhm_do_dhm:16:"50000000000000000000000000000000000000000000000000000000100014e4c3111300f060355040a13086f53534c00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000052b810400224ee06ec30e5753333958e280a8000000809539c2885280afd66aab21ddb8d31c6e58b8cae8b2698ef341ad29c3b45f75a7476fd5192955699a533b20b4661660341e00000040000000160000000000001604149d316d202449023f2bcb78b519bc7fffc9cbfb357c316e0603cdcdcdcd0ba34677b8b3be2c3633023100fdbfff7b67df9d7b7f7f00476fd5192955699a533b20b4661660341e00000040000000160000000000001604149d316d202449023f2bcb78b519bc7fffc9cbfb357c316e0603cdcdcdcd0ba34677b8b3be2c3633023100fdbfff7b67df9d7b7f7f000000000001000400000000000000506f6c617253530000000000000000000000000000000000000000110000f6de000000000000000000000000000000000000000000000000000000000000000000000000000000000000004c323536193017060000004f000000000000000000000005000000000000000000000000001603030039020000350303cf02020244e8786d95de3d020202e101f2f34e75c8b70a610e44c1000000000000008400000d00a30000ff60010001000016000016030102660b00026200025f00025c30820258308201c1a003020102020900fbb04c2eab109b0c300d06092a864886f70d01010505003045310b3009060355040e130241553113301106035504080c0a536f6d654853746174653121301f060355040a0c18496e7465726e6574205769646769747320507479204c7464301e170d3134303732333230353034305a170d3137303432323230353034305a3045310b3009060355042e130241553113301106035574080c0a136f6d652d53746174653121301f06035504050c18496e7465726e6574205769646769747320507479204c746430819f300d06092a864886f70d010101050003818d003081890281816602ffffff9e000000000000020000bf1400000000000100000000000000feffef00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001e1e1e001e1e1e1e1e00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000050000000000000000000000000000000000000000000000000000000000000000000000000000000000040ffd0100010000160000000000000000000000000000ff00000008000000000000000000000000000000000000000000000000000000000000000000000100014e4c3111300f060355040a13086f53534c00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000052b810400224ee06ec30e5753333958e280a8000000809539c2885280afd66aab21ddb8d31c6e58b8cae8b2698ef341ad29c3b45f75a7476fd5192955699a533b20b4661660341e00000040000000160000000000001604149d316d202449023f2bcb78b519bc7fffc9cbfb357c316e0603cdcdcdcd0ba34677b8b3be2c3633023100fdbfff7b67df9d7b7f7f00476fd5192955699a533b20b4661660341e00000040000000160000000000001604149d316d202449023f2bcb78b519bc7fffc9cbfb357c316e0603cdcdcdcd0ba34677b8b3be2c3633023100fdbfff7b67df9d7b7f7f000000000001000400000000000000506f6c617253530000000000000000000000000000000000000000110000f6de000000000000000000000000000000000000000000000000000000000000000000000000000000000000004c323536193017060000004f000000000000000000000005000000000000000000000000001603030039020000350303cf02020244e8786d95de3d020202e101f2f34e75c8b70a610e44c1000000000000008400000d00a30000ff60010001000016000016030102660b00026200025f00025c30820258308201c1a003020102020900fbb04c2eab109b0c300d06092a864886f70dc9784adc17e9e82f4cadccc1747090a92f8ca6840c0f404db671d219301706035504031310506f6c617253534c205465737420434130820122300d06092a864886f70d0101010500038201160303005b02000057030367c6699151ff4aec29cdbaabf2fbe3467cc254f81be8e78d765a2e63339fc99a2009fc99a2066310db7315864fc99a2066320db73058a3ff7f00001758e942d4abb2cdc64e9bb43ddc87c03db1b28d17e02cb23":10:"5":MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED+MBEDTLS_ERR_MPI_BAD_INPUT_DATA
+
+Diffie-Hellman load parameters from file [#1]
 dhm_file:"data_files/dhparams.pem":"9e35f430443a09904f3a39a979797d070df53378e79c2438bef4e761f3c714553328589b041c809be1d6c6b5f1fc9f47d3a25443188253a992a56818b37ba9de5a40d362e56eff0be5417474c125c199272c8fe41dea733df6f662c92ae76556e755d10c64e6a50968f67fc6ea73d0dca8569be2ba204e23580d8bca2f4975b3":"02":128
 
-Diffie-Hellman load parameters from file
+Diffie-Hellman load parameters from file [#2]
 dhm_file:"data_files/dh.optlen.pem":"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":"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":256
 
 Diffie-Hellman selftest
diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index 00926ff97..a640cf264 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -679,9 +679,12 @@ mbedtls_mpi_exp_mod:10:"-23":10:"13":10:"29":10:"":10:"5":0
 Base test mbedtls_mpi_exp_mod #5 (Negative exponent)
 mbedtls_mpi_exp_mod:10:"23":10:"-13":10:"29":10:"":10:"0":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
-Base test mbedtls_mpi_exp_mod #7 (Negative base + exponent)
+Base test mbedtls_mpi_exp_mod #6 (Negative base + exponent)
 mbedtls_mpi_exp_mod:10:"-23":10:"-13":10:"29":10:"":10:"0":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
+Base test mbedtls_mpi_exp_mod #7 (Huge exponent)
+mbedtls_mpi_exp_mod:10:"23":16:"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":10:"29":10:"":10:"0":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
+
 Test mbedtls_mpi_exp_mod #1
 mbedtls_mpi_exp_mod:10:"433019240910377478217373572959560109819648647016096560523769010881172869083338285573756574557395862965095016483867813043663981946477698466501451832407592327356331263124555137732393938242285782144928753919588632679050799198937132922145084847":10:"5781538327977828897150909166778407659250458379645823062042492461576758526757490910073628008613977550546382774775570888130029763571528699574717583228939535960234464230882573615930384979100379102915657483866755371559811718767760594919456971354184113721":10:"583137007797276923956891216216022144052044091311388601652961409557516421612874571554415606746479105795833145583959622117418531166391184939066520869800857530421873250114773204354963864729386957427276448683092491947566992077136553066273207777134303397724679138833126700957":10:"":10:"114597449276684355144920670007147953232659436380163461553186940113929777196018164149703566472936578890991049344459204199888254907113495794730452699842273939581048142004834330369483813876618772578869083248061616444392091693787039636316845512292127097865026290173004860736":0
 

From 25038abadb562b7b07f7af79cb7a1c012f3d71a1 Mon Sep 17 00:00:00 2001
From: Chris Jones <christopher.jones@arm.com>
Date: Mon, 30 Nov 2020 11:16:48 +0000
Subject: [PATCH 10/19] Add ChangeLog entry for modular exponentiation size
 limit

Signed-off-by: Chris Jones <christopher.jones@arm.com>
---
 ChangeLog.d/limit_size_of_diffie_hellman_calculations.txt | 4 ++++
 1 file changed, 4 insertions(+)
 create mode 100644 ChangeLog.d/limit_size_of_diffie_hellman_calculations.txt

diff --git a/ChangeLog.d/limit_size_of_diffie_hellman_calculations.txt b/ChangeLog.d/limit_size_of_diffie_hellman_calculations.txt
new file mode 100644
index 000000000..982b7bc2c
--- /dev/null
+++ b/ChangeLog.d/limit_size_of_diffie_hellman_calculations.txt
@@ -0,0 +1,4 @@
+Security
+   * Limit the size of calculations performed by mbedtls_mpi_exp_mod to 
+     MBEDTLS_MPI_MAX_SIZE to prevent a potential denial of service when 
+     generating Diffie-Hellman key pairs. Credit to OSS-Fuzz.
\ No newline at end of file

From 415c7be0aa11b426b699ad35e5ec98b0be4e7f5b Mon Sep 17 00:00:00 2001
From: Chris Jones <christopher.jones@arm.com>
Date: Wed, 2 Dec 2020 10:41:50 +0000
Subject: [PATCH 11/19] Test that overly large Diffie-Hellman keys are rejected

Adds test cases to ensure that `mbedtls_mpi_exp_mod` will return an error with
an exponent or modulus that is greater than `MBEDTLS_MPI_MAX_SIZE` in size.

Adds test cases to ensure that Diffie-Hellman will fail to make a key pair
(using `mbedtls_dhm_make_public`) when the prime modulus is greater than
`MBEDTLS_MPI_MAX_SIZE` in size.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
---
 tests/suites/test_suite_dhm.data     |  7 +++++--
 tests/suites/test_suite_dhm.function | 30 +++++++++++++++++++++++++++
 tests/suites/test_suite_mpi.data     | 13 ++++++++++--
 tests/suites/test_suite_mpi.function | 31 ++++++++++++++++++++++++++++
 4 files changed, 77 insertions(+), 4 deletions(-)

diff --git a/tests/suites/test_suite_dhm.data b/tests/suites/test_suite_dhm.data
index 351ec840a..c4795b6d3 100644
--- a/tests/suites/test_suite_dhm.data
+++ b/tests/suites/test_suite_dhm.data
@@ -22,8 +22,11 @@ dhm_do_dhm:10:"3":10:"5":MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED
 Diffie-Hellman zero modulus
 dhm_do_dhm:10:"0":10:"5":MBEDTLS_ERR_DHM_BAD_INPUT_DATA
 
-Diffie-Hellman huge modulus
-dhm_do_dhm:16:"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":10:"5":MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED+MBEDTLS_ERR_MPI_BAD_INPUT_DATA
+Diffie-Hellman MPI_MAX_SIZE modulus
+dhm_make_public:MBEDTLS_MPI_MAX_SIZE:10:"5":0
+
+Diffie-Hellman MPI_MAX_SIZE + 1 modulus
+dhm_make_public:MBEDTLS_MPI_MAX_SIZE + 1:10:"5":MBEDTLS_ERR_DHM_MAKE_PUBLIC_FAILED+MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
 Diffie-Hellman load parameters from file [#1]
 dhm_file:"data_files/dhparams.pem":"9e35f430443a09904f3a39a979797d070df53378e79c2438bef4e761f3c714553328589b041c809be1d6c6b5f1fc9f47d3a25443188253a992a56818b37ba9de5a40d362e56eff0be5417474c125c199272c8fe41dea733df6f662c92ae76556e755d10c64e6a50968f67fc6ea73d0dca8569be2ba204e23580d8bca2f4975b3":"02":128
diff --git a/tests/suites/test_suite_dhm.function b/tests/suites/test_suite_dhm.function
index 8a05a38df..f4a992cad 100644
--- a/tests/suites/test_suite_dhm.function
+++ b/tests/suites/test_suite_dhm.function
@@ -206,6 +206,36 @@ exit:
 }
 /* END_CASE */
 
+/* BEGIN_CASE */
+void dhm_make_public( int P_bytes, int radix_G, char *input_G, int result )
+{
+    mbedtls_mpi P, G;
+    mbedtls_dhm_context ctx;
+    unsigned char output[MBEDTLS_MPI_MAX_SIZE];
+
+    mbedtls_mpi_init( &P );
+    mbedtls_mpi_init( &G );
+    mbedtls_dhm_init( &ctx );
+
+    TEST_ASSERT( mbedtls_mpi_lset( &P, 1 ) == 0 );
+    TEST_ASSERT( mbedtls_mpi_shift_l( &P, ( P_bytes * 8 ) - 1 ) == 0 );
+    TEST_ASSERT( mbedtls_mpi_set_bit( &P, 0, 1 ) == 0 );
+
+    TEST_ASSERT( mbedtls_mpi_read_string( &G, radix_G, input_G ) == 0 );
+
+    TEST_ASSERT( mbedtls_dhm_set_group( &ctx, &P, &G ) == 0 );
+    TEST_ASSERT( mbedtls_dhm_make_public( &ctx, (int) mbedtls_mpi_size( &P ),
+                                          output, sizeof(output),
+                                          &mbedtls_test_rnd_pseudo_rand,
+                                          NULL ) == result );
+
+exit:
+    mbedtls_mpi_free( &P );
+    mbedtls_mpi_free( &G );
+    mbedtls_dhm_free( &ctx );
+}
+/* END_CASE */
+
 /* BEGIN_CASE depends_on:MBEDTLS_FS_IO */
 void dhm_file( char * filename, char * p, char * g, int len )
 {
diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index a640cf264..671756254 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -682,8 +682,17 @@ mbedtls_mpi_exp_mod:10:"23":10:"-13":10:"29":10:"":10:"0":MBEDTLS_ERR_MPI_BAD_IN
 Base test mbedtls_mpi_exp_mod #6 (Negative base + exponent)
 mbedtls_mpi_exp_mod:10:"-23":10:"-13":10:"29":10:"":10:"0":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
-Base test mbedtls_mpi_exp_mod #7 (Huge exponent)
-mbedtls_mpi_exp_mod:10:"23":16:"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":10:"29":10:"":10:"0":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
+Base test mbedtls_mpi_exp_mod #7 (MAX_SIZE exponent)
+mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE:2:10:"":0
+
+Base test mbedtls_mpi_exp_mod #8 (MAX_SIZE + 1 exponent)
+mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE + 1:2:10:"":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
+
+Base test mbedtls_mpi_exp_mod #9 (MAX_SIZE modulus)
+mbedtls_mpi_exp_mod_size:2:2:MBEDTLS_MPI_MAX_SIZE:10:"":0
+
+Base test mbedtls_mpi_exp_mod #10 (MAX_SIZE + 1 modulus)
+mbedtls_mpi_exp_mod_size:2:2:MBEDTLS_MPI_MAX_SIZE + 1:10:"":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
 Test mbedtls_mpi_exp_mod #1
 mbedtls_mpi_exp_mod:10:"433019240910377478217373572959560109819648647016096560523769010881172869083338285573756574557395862965095016483867813043663981946477698466501451832407592327356331263124555137732393938242285782144928753919588632679050799198937132922145084847":10:"5781538327977828897150909166778407659250458379645823062042492461576758526757490910073628008613977550546382774775570888130029763571528699574717583228939535960234464230882573615930384979100379102915657483866755371559811718767760594919456971354184113721":10:"583137007797276923956891216216022144052044091311388601652961409557516421612874571554415606746479105795833145583959622117418531166391184939066520869800857530421873250114773204354963864729386957427276448683092491947566992077136553066273207777134303397724679138833126700957":10:"":10:"114597449276684355144920670007147953232659436380163461553186940113929777196018164149703566472936578890991049344459204199888254907113495794730452699842273939581048142004834330369483813876618772578869083248061616444392091693787039636316845512292127097865026290173004860736":0
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index f2702f12b..c61d8b349 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -1110,6 +1110,37 @@ exit:
 }
 /* END_CASE */
 
+/* BEGIN_CASE */
+void mbedtls_mpi_exp_mod_size( int A_bytes, int E_bytes, int N_bytes,
+                               int radix_RR, char * input_RR, int div_result )
+{
+    mbedtls_mpi A, E, N, RR, Z;
+    mbedtls_mpi_init( &A  ); mbedtls_mpi_init( &E ); mbedtls_mpi_init( &N );
+    mbedtls_mpi_init( &RR ); mbedtls_mpi_init( &Z );
+
+    TEST_ASSERT( mbedtls_mpi_lset( &A, 1 ) == 0 );
+    TEST_ASSERT( mbedtls_mpi_lset( &E, 1 ) == 0 );
+    TEST_ASSERT( mbedtls_mpi_lset( &N, 1 ) == 0 );
+
+    TEST_ASSERT( mbedtls_mpi_shift_l( &A, ( A_bytes * 8 ) - 1 ) == 0 );
+    TEST_ASSERT( mbedtls_mpi_shift_l( &E, ( E_bytes * 8 ) - 1 ) == 0 );
+    TEST_ASSERT( mbedtls_mpi_shift_l( &N, ( N_bytes * 8 ) - 1 ) == 0 );
+
+    TEST_ASSERT( mbedtls_mpi_set_bit( &A, 0, 1 ) == 0 );
+    TEST_ASSERT( mbedtls_mpi_set_bit( &E, 0, 1 ) == 0 );
+    TEST_ASSERT( mbedtls_mpi_set_bit( &N, 0, 1 ) == 0 );
+
+    if( strlen( input_RR ) )
+        TEST_ASSERT( mbedtls_mpi_read_string( &RR, radix_RR, input_RR ) == 0 );
+
+    TEST_ASSERT( mbedtls_mpi_exp_mod( &Z, &A, &E, &N, &RR ) == div_result );
+
+exit:
+    mbedtls_mpi_free( &A  ); mbedtls_mpi_free( &E ); mbedtls_mpi_free( &N );
+    mbedtls_mpi_free( &RR ); mbedtls_mpi_free( &Z );
+}
+/* END_CASE */
+
 /* BEGIN_CASE */
 void mbedtls_mpi_inv_mod( int radix_X, char * input_X, int radix_Y,
                           char * input_Y, int radix_A, char * input_A,

From 4a0ccb6862dbe8ee69e5ebc7c44baa232503a171 Mon Sep 17 00:00:00 2001
From: Chris Jones <christopher.jones@arm.com>
Date: Wed, 2 Dec 2020 16:27:42 +0000
Subject: [PATCH 12/19] Extend exponentiation test coverage

Add two further boundary tests for cases where both the exponent and modulus to
`mbedtls_mpi_exp_mod()` are `MBEDTLS_MPI_MAX_SIZE`, or longer, bytes long.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
---
 tests/suites/test_suite_mpi.data | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index 671756254..bbb2cd45e 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -694,6 +694,12 @@ mbedtls_mpi_exp_mod_size:2:2:MBEDTLS_MPI_MAX_SIZE:10:"":0
 Base test mbedtls_mpi_exp_mod #10 (MAX_SIZE + 1 modulus)
 mbedtls_mpi_exp_mod_size:2:2:MBEDTLS_MPI_MAX_SIZE + 1:10:"":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
+Base test mbedtls_mpi_exp_mod #11 (MAX_SIZE exponent and modulus)
+mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE:MBEDTLS_MPI_MAX_SIZE:10:"":0
+
+Base test mbedtls_mpi_exp_mod #12 (MAX_SIZE + 1 exponent and modulus)
+mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE + 1:MBEDTLS_MPI_MAX_SIZE + 1:10:"":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
+
 Test mbedtls_mpi_exp_mod #1
 mbedtls_mpi_exp_mod:10:"433019240910377478217373572959560109819648647016096560523769010881172869083338285573756574557395862965095016483867813043663981946477698466501451832407592327356331263124555137732393938242285782144928753919588632679050799198937132922145084847":10:"5781538327977828897150909166778407659250458379645823062042492461576758526757490910073628008613977550546382774775570888130029763571528699574717583228939535960234464230882573615930384979100379102915657483866755371559811718767760594919456971354184113721":10:"583137007797276923956891216216022144052044091311388601652961409557516421612874571554415606746479105795833145583959622117418531166391184939066520869800857530421873250114773204354963864729386957427276448683092491947566992077136553066273207777134303397724679138833126700957":10:"":10:"114597449276684355144920670007147953232659436380163461553186940113929777196018164149703566472936578890991049344459204199888254907113495794730452699842273939581048142004834330369483813876618772578869083248061616444392091693787039636316845512292127097865026290173004860736":0
 

From a18813ea1c6c53835b187879fa00999de721eea5 Mon Sep 17 00:00:00 2001
From: Chris Jones <christopher.jones@arm.com>
Date: Thu, 3 Dec 2020 11:35:41 +0000
Subject: [PATCH 13/19] Reword test cases

Reword test cases to be easier to read and understand.
Adds comments to better explain what the test is doing.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
---
 tests/suites/test_suite_mpi.data     | 12 ++++++------
 tests/suites/test_suite_mpi.function | 19 +++++++++++--------
 2 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index bbb2cd45e..7a11f5ba1 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -682,22 +682,22 @@ mbedtls_mpi_exp_mod:10:"23":10:"-13":10:"29":10:"":10:"0":MBEDTLS_ERR_MPI_BAD_IN
 Base test mbedtls_mpi_exp_mod #6 (Negative base + exponent)
 mbedtls_mpi_exp_mod:10:"-23":10:"-13":10:"29":10:"":10:"0":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
-Base test mbedtls_mpi_exp_mod #7 (MAX_SIZE exponent)
+Test mbedtls_mpi_exp_mod: MAX_SIZE exponent
 mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE:2:10:"":0
 
-Base test mbedtls_mpi_exp_mod #8 (MAX_SIZE + 1 exponent)
+Test mbedtls_mpi_exp_mod: MAX_SIZE + 1 exponent
 mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE + 1:2:10:"":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
-Base test mbedtls_mpi_exp_mod #9 (MAX_SIZE modulus)
+Test mbedtls_mpi_exp_mod: MAX_SIZE modulus
 mbedtls_mpi_exp_mod_size:2:2:MBEDTLS_MPI_MAX_SIZE:10:"":0
 
-Base test mbedtls_mpi_exp_mod #10 (MAX_SIZE + 1 modulus)
+Test mbedtls_mpi_exp_mod: MAX_SIZE + 1 modulus
 mbedtls_mpi_exp_mod_size:2:2:MBEDTLS_MPI_MAX_SIZE + 1:10:"":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
-Base test mbedtls_mpi_exp_mod #11 (MAX_SIZE exponent and modulus)
+Test mbedtls_mpi_exp_mod: MAX_SIZE exponent and modulus
 mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE:MBEDTLS_MPI_MAX_SIZE:10:"":0
 
-Base test mbedtls_mpi_exp_mod #12 (MAX_SIZE + 1 exponent and modulus)
+Test mbedtls_mpi_exp_mod: MAX_SIZE + 1 exponent and modulus
 mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE + 1:MBEDTLS_MPI_MAX_SIZE + 1:10:"":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
 Test mbedtls_mpi_exp_mod #1
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index c61d8b349..848a8de53 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -1112,28 +1112,31 @@ exit:
 
 /* BEGIN_CASE */
 void mbedtls_mpi_exp_mod_size( int A_bytes, int E_bytes, int N_bytes,
-                               int radix_RR, char * input_RR, int div_result )
+                               int radix_RR, char * input_RR, int exp_result )
 {
     mbedtls_mpi A, E, N, RR, Z;
     mbedtls_mpi_init( &A  ); mbedtls_mpi_init( &E ); mbedtls_mpi_init( &N );
     mbedtls_mpi_init( &RR ); mbedtls_mpi_init( &Z );
 
+    /* Set A to 2^(A_bytes - 1) + 1 */
     TEST_ASSERT( mbedtls_mpi_lset( &A, 1 ) == 0 );
-    TEST_ASSERT( mbedtls_mpi_lset( &E, 1 ) == 0 );
-    TEST_ASSERT( mbedtls_mpi_lset( &N, 1 ) == 0 );
-
     TEST_ASSERT( mbedtls_mpi_shift_l( &A, ( A_bytes * 8 ) - 1 ) == 0 );
-    TEST_ASSERT( mbedtls_mpi_shift_l( &E, ( E_bytes * 8 ) - 1 ) == 0 );
-    TEST_ASSERT( mbedtls_mpi_shift_l( &N, ( N_bytes * 8 ) - 1 ) == 0 );
-
     TEST_ASSERT( mbedtls_mpi_set_bit( &A, 0, 1 ) == 0 );
+
+    /* Set E to 2^(E_bytes - 1) + 1 */
+    TEST_ASSERT( mbedtls_mpi_lset( &E, 1 ) == 0 );
+    TEST_ASSERT( mbedtls_mpi_shift_l( &E, ( E_bytes * 8 ) - 1 ) == 0 );
     TEST_ASSERT( mbedtls_mpi_set_bit( &E, 0, 1 ) == 0 );
+
+    /* Set N to 2^(N_bytes - 1) + 1 */
+    TEST_ASSERT( mbedtls_mpi_lset( &N, 1 ) == 0 );
+    TEST_ASSERT( mbedtls_mpi_shift_l( &N, ( N_bytes * 8 ) - 1 ) == 0 );
     TEST_ASSERT( mbedtls_mpi_set_bit( &N, 0, 1 ) == 0 );
 
     if( strlen( input_RR ) )
         TEST_ASSERT( mbedtls_mpi_read_string( &RR, radix_RR, input_RR ) == 0 );
 
-    TEST_ASSERT( mbedtls_mpi_exp_mod( &Z, &A, &E, &N, &RR ) == div_result );
+    TEST_ASSERT( mbedtls_mpi_exp_mod( &Z, &A, &E, &N, &RR ) == exp_result );
 
 exit:
     mbedtls_mpi_free( &A  ); mbedtls_mpi_free( &E ); mbedtls_mpi_free( &N );

From 877329af751a36218fe7e0b0b633d3dfbe12a015 Mon Sep 17 00:00:00 2001
From: Chris Jones <christopher.jones@arm.com>
Date: Thu, 3 Dec 2020 11:52:40 +0000
Subject: [PATCH 14/19] Fix cases where exponentiation was not fully tested

In two test cases, the exponentiation computation was not being fully tested
as when A_bytes (the base) == N_bytes (the modulus) -> A = N. When this is the
case A is reduced to 0 and therefore the result of the computation will always
be 0.

This fixes that issue and therefore increases the test coverage to ensure
different computations are actually being run.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
---
 tests/suites/test_suite_mpi.data | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index 7a11f5ba1..0805fa3e9 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -683,10 +683,10 @@ Base test mbedtls_mpi_exp_mod #6 (Negative base + exponent)
 mbedtls_mpi_exp_mod:10:"-23":10:"-13":10:"29":10:"":10:"0":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
 Test mbedtls_mpi_exp_mod: MAX_SIZE exponent
-mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE:2:10:"":0
+mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE:10:10:"":0
 
 Test mbedtls_mpi_exp_mod: MAX_SIZE + 1 exponent
-mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE + 1:2:10:"":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
+mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE + 1:10:10:"":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
 Test mbedtls_mpi_exp_mod: MAX_SIZE modulus
 mbedtls_mpi_exp_mod_size:2:2:MBEDTLS_MPI_MAX_SIZE:10:"":0

From ce6fa8f4119df6f4b3a0379f422251fc8620d407 Mon Sep 17 00:00:00 2001
From: Chris Jones <christopher.jones@arm.com>
Date: Thu, 3 Dec 2020 14:24:33 +0000
Subject: [PATCH 15/19] Fix broken testing on numbers that may be greater than
 MPI_MAX_SIZE

Previously `mbedtls_mpi_exp_mod` was tested with values that were over
`MBEDTLS_MPI_MAX_SIZE` in size. This is useful to do as some paths are only
taken when the exponent is large enough however, on builds where
`MBEDTLS_MPI_MAX_SIZE` is under the size of these test values.

This fix turns off these tests when `MBEDTLS_MPI_MAX_SIZE` is too small to
safely test (notably this is the case in config-thread.h).

Signed-off-by: Chris Jones <christopher.jones@arm.com>
---
 tests/suites/test_suite_mpi.function | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index 848a8de53..5d8cfc4c2 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -1,6 +1,10 @@
 /* BEGIN_HEADER */
 #include "mbedtls/bignum.h"
 
+#if MBEDTLS_MPI_MAX_BITS > 256
+#define MPI_MAX_BITS_LARGER_THAN_256
+#endif
+
 typedef struct mbedtls_test_mpi_random
 {
     data_t *data;
@@ -1078,7 +1082,7 @@ exit:
 }
 /* END_CASE */
 
-/* BEGIN_CASE */
+/* BEGIN_CASE depends_on:MPI_MAX_BITS_LARGER_THAN_256 */
 void mbedtls_mpi_exp_mod( int radix_A, char * input_A, int radix_E,
                           char * input_E, int radix_N, char * input_N,
                           int radix_RR, char * input_RR, int radix_X,

From 49e6e9d41086661ab38cbb7f6d4104c6b99bbe81 Mon Sep 17 00:00:00 2001
From: Chris Jones <christopher.jones@arm.com>
Date: Thu, 3 Dec 2020 15:22:25 +0000
Subject: [PATCH 16/19] Move dependancy to specific test cases

Move dependancy on `MBEDTLS_MPI_MAX_BITS` to apply to the specific test cases
which will break when `MBEDTLS_MPI_MAX_BITS` is too small. This re-enables
previous tests that were turned off accidentally.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
---
 tests/suites/test_suite_mpi.data     | 4 +++-
 tests/suites/test_suite_mpi.function | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index 0805fa3e9..076250e8e 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -701,12 +701,14 @@ Test mbedtls_mpi_exp_mod: MAX_SIZE + 1 exponent and modulus
 mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE + 1:MBEDTLS_MPI_MAX_SIZE + 1:10:"":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
 Test mbedtls_mpi_exp_mod #1
+depends_on:MPI_MAX_BITS_LARGER_THAN_256
 mbedtls_mpi_exp_mod:10:"433019240910377478217373572959560109819648647016096560523769010881172869083338285573756574557395862965095016483867813043663981946477698466501451832407592327356331263124555137732393938242285782144928753919588632679050799198937132922145084847":10:"5781538327977828897150909166778407659250458379645823062042492461576758526757490910073628008613977550546382774775570888130029763571528699574717583228939535960234464230882573615930384979100379102915657483866755371559811718767760594919456971354184113721":10:"583137007797276923956891216216022144052044091311388601652961409557516421612874571554415606746479105795833145583959622117418531166391184939066520869800857530421873250114773204354963864729386957427276448683092491947566992077136553066273207777134303397724679138833126700957":10:"":10:"114597449276684355144920670007147953232659436380163461553186940113929777196018164149703566472936578890991049344459204199888254907113495794730452699842273939581048142004834330369483813876618772578869083248061616444392091693787039636316845512292127097865026290173004860736":0
 
 Test mbedtls_mpi_exp_mod (Negative base)
 mbedtls_mpi_exp_mod:10:"-10000000000":10:"10000000000":10:"99999":10:"":10:"1":0
 
-Test mbedtls_mpi_exp_mod (Negative base)
+Test mbedtls_mpi_exp_mod (Negative base) [#2]
+depends_on:MPI_MAX_BITS_LARGER_THAN_256
 mbedtls_mpi_exp_mod:16:"-9f13012cd92aa72fb86ac8879d2fde4f7fd661aaae43a00971f081cc60ca277059d5c37e89652e2af2585d281d66ef6a9d38a117e9608e9e7574cd142dc55278838a2161dd56db9470d4c1da2d5df15a908ee2eb886aaa890f23be16de59386663a12f1afbb325431a3e835e3fd89b98b96a6f77382f458ef9a37e1f84a03045c8676ab55291a94c2228ea15448ee96b626b998":16:"40a54d1b9e86789f06d9607fb158672d64867665c73ee9abb545fc7a785634b354c7bae5b962ce8040cf45f2c1f3d3659b2ee5ede17534c8fc2ec85c815e8df1fe7048d12c90ee31b88a68a081f17f0d8ce5f4030521e9400083bcea73a429031d4ca7949c2000d597088e0c39a6014d8bf962b73bb2e8083bd0390a4e00b9b3":16:"eeaf0ab9adb38dd69c33f80afa8fc5e86072618775ff3c0b9ea2314c9c256576d674df7496ea81d3383b4813d692c6e0e0d5d8e250b98be48e495c1d6089dad15dc7d7b46154d6b6ce8ef4ad69b15d4982559b297bcf1885c529f566660e57ec68edbc3c05726cc02fd4cbf4976eaa9afd5138fe8376435b9fc61d2fc0eb06e3":16:"":16:"21acc7199e1b90f9b4844ffe12c19f00ec548c5d32b21c647d48b6015d8eb9ec9db05b4f3d44db4227a2b5659c1a7cceb9d5fa8fa60376047953ce7397d90aaeb7465e14e820734f84aa52ad0fc66701bcbb991d57715806a11531268e1e83dd48288c72b424a6287e9ce4e5cc4db0dd67614aecc23b0124a5776d36e5c89483":0
 
 Base test GCD #1
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index 5d8cfc4c2..186582d55 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -1082,7 +1082,7 @@ exit:
 }
 /* END_CASE */
 
-/* BEGIN_CASE depends_on:MPI_MAX_BITS_LARGER_THAN_256 */
+/* BEGIN_CASE */
 void mbedtls_mpi_exp_mod( int radix_A, char * input_A, int radix_E,
                           char * input_E, int radix_N, char * input_N,
                           int radix_RR, char * input_RR, int radix_X,

From c7ea6340cf5fb83a1384debc2b62e5bdd6fa75cc Mon Sep 17 00:00:00 2001
From: Chris Jones <christopher.jones@arm.com>
Date: Thu, 3 Dec 2020 15:45:29 +0000
Subject: [PATCH 17/19] Fix whitespace in changelog entry

Extra whitespace and a missing newline at end of file was causing an error with
`check_files.py`.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
---
 ChangeLog.d/limit_size_of_diffie_hellman_calculations.txt | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/ChangeLog.d/limit_size_of_diffie_hellman_calculations.txt b/ChangeLog.d/limit_size_of_diffie_hellman_calculations.txt
index 982b7bc2c..2ba98d541 100644
--- a/ChangeLog.d/limit_size_of_diffie_hellman_calculations.txt
+++ b/ChangeLog.d/limit_size_of_diffie_hellman_calculations.txt
@@ -1,4 +1,4 @@
 Security
-   * Limit the size of calculations performed by mbedtls_mpi_exp_mod to 
-     MBEDTLS_MPI_MAX_SIZE to prevent a potential denial of service when 
-     generating Diffie-Hellman key pairs. Credit to OSS-Fuzz.
\ No newline at end of file
+   * Limit the size of calculations performed by mbedtls_mpi_exp_mod to
+     MBEDTLS_MPI_MAX_SIZE to prevent a potential denial of service when
+     generating Diffie-Hellman key pairs. Credit to OSS-Fuzz.

From 74b7ee4f12a879da90cd1a099f83b39258a6129a Mon Sep 17 00:00:00 2001
From: Chris Jones <christopher.jones@arm.com>
Date: Thu, 3 Dec 2020 17:33:55 +0000
Subject: [PATCH 18/19] Fix test_suite_dhm build

Fix build as the name of the random function changed from development to 2.7.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
---
 tests/suites/test_suite_dhm.function | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/suites/test_suite_dhm.function b/tests/suites/test_suite_dhm.function
index f4a992cad..6ec1e7e88 100644
--- a/tests/suites/test_suite_dhm.function
+++ b/tests/suites/test_suite_dhm.function
@@ -226,7 +226,7 @@ void dhm_make_public( int P_bytes, int radix_G, char *input_G, int result )
     TEST_ASSERT( mbedtls_dhm_set_group( &ctx, &P, &G ) == 0 );
     TEST_ASSERT( mbedtls_dhm_make_public( &ctx, (int) mbedtls_mpi_size( &P ),
                                           output, sizeof(output),
-                                          &mbedtls_test_rnd_pseudo_rand,
+                                          &rnd_pseudo_rand,
                                           NULL ) == result );
 
 exit:

From 5dd1e266e1e594817df4509b635d950afc764186 Mon Sep 17 00:00:00 2001
From: Chris Jones <christopher.jones@arm.com>
Date: Thu, 3 Dec 2020 17:44:03 +0000
Subject: [PATCH 19/19] Fix exponentiation tests with `MBEDTLS_MPI_MAX_BITS`
 larger than 256

Fixes an issue where configs that had `MBEDTLS_MPI_MAX_BITS` greater than 256
but smaller than the test that was running (792 bits) the test would fail
incorrectly.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
---
 tests/suites/test_suite_mpi.data     | 4 ++--
 tests/suites/test_suite_mpi.function | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index 076250e8e..e5ec77796 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -701,14 +701,14 @@ Test mbedtls_mpi_exp_mod: MAX_SIZE + 1 exponent and modulus
 mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE + 1:MBEDTLS_MPI_MAX_SIZE + 1:10:"":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
 Test mbedtls_mpi_exp_mod #1
-depends_on:MPI_MAX_BITS_LARGER_THAN_256
+depends_on:MPI_MAX_BITS_LARGER_THAN_792
 mbedtls_mpi_exp_mod:10:"433019240910377478217373572959560109819648647016096560523769010881172869083338285573756574557395862965095016483867813043663981946477698466501451832407592327356331263124555137732393938242285782144928753919588632679050799198937132922145084847":10:"5781538327977828897150909166778407659250458379645823062042492461576758526757490910073628008613977550546382774775570888130029763571528699574717583228939535960234464230882573615930384979100379102915657483866755371559811718767760594919456971354184113721":10:"583137007797276923956891216216022144052044091311388601652961409557516421612874571554415606746479105795833145583959622117418531166391184939066520869800857530421873250114773204354963864729386957427276448683092491947566992077136553066273207777134303397724679138833126700957":10:"":10:"114597449276684355144920670007147953232659436380163461553186940113929777196018164149703566472936578890991049344459204199888254907113495794730452699842273939581048142004834330369483813876618772578869083248061616444392091693787039636316845512292127097865026290173004860736":0
 
 Test mbedtls_mpi_exp_mod (Negative base)
 mbedtls_mpi_exp_mod:10:"-10000000000":10:"10000000000":10:"99999":10:"":10:"1":0
 
 Test mbedtls_mpi_exp_mod (Negative base) [#2]
-depends_on:MPI_MAX_BITS_LARGER_THAN_256
+depends_on:MPI_MAX_BITS_LARGER_THAN_792
 mbedtls_mpi_exp_mod:16:"-9f13012cd92aa72fb86ac8879d2fde4f7fd661aaae43a00971f081cc60ca277059d5c37e89652e2af2585d281d66ef6a9d38a117e9608e9e7574cd142dc55278838a2161dd56db9470d4c1da2d5df15a908ee2eb886aaa890f23be16de59386663a12f1afbb325431a3e835e3fd89b98b96a6f77382f458ef9a37e1f84a03045c8676ab55291a94c2228ea15448ee96b626b998":16:"40a54d1b9e86789f06d9607fb158672d64867665c73ee9abb545fc7a785634b354c7bae5b962ce8040cf45f2c1f3d3659b2ee5ede17534c8fc2ec85c815e8df1fe7048d12c90ee31b88a68a081f17f0d8ce5f4030521e9400083bcea73a429031d4ca7949c2000d597088e0c39a6014d8bf962b73bb2e8083bd0390a4e00b9b3":16:"eeaf0ab9adb38dd69c33f80afa8fc5e86072618775ff3c0b9ea2314c9c256576d674df7496ea81d3383b4813d692c6e0e0d5d8e250b98be48e495c1d6089dad15dc7d7b46154d6b6ce8ef4ad69b15d4982559b297bcf1885c529f566660e57ec68edbc3c05726cc02fd4cbf4976eaa9afd5138fe8376435b9fc61d2fc0eb06e3":16:"":16:"21acc7199e1b90f9b4844ffe12c19f00ec548c5d32b21c647d48b6015d8eb9ec9db05b4f3d44db4227a2b5659c1a7cceb9d5fa8fa60376047953ce7397d90aaeb7465e14e820734f84aa52ad0fc66701bcbb991d57715806a11531268e1e83dd48288c72b424a6287e9ce4e5cc4db0dd67614aecc23b0124a5776d36e5c89483":0
 
 Base test GCD #1
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index 186582d55..03355382d 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -1,8 +1,8 @@
 /* BEGIN_HEADER */
 #include "mbedtls/bignum.h"
 
-#if MBEDTLS_MPI_MAX_BITS > 256
-#define MPI_MAX_BITS_LARGER_THAN_256
+#if MBEDTLS_MPI_MAX_BITS > 792
+#define MPI_MAX_BITS_LARGER_THAN_792
 #endif
 
 typedef struct mbedtls_test_mpi_random