From 8b1f65ea00d2cb444f63bf436ebee917ef7ee87a 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 01/12] 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 3135ec4ad..ba4bb831f 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1859,6 +1859,10 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
     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 8c650f985d09dfadd8b80c462c8911e8a8266325 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 02/12] 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 734fd97ac..64f0ca306 100644
--- a/tests/suites/test_suite_dhm.data
+++ b/tests/suites/test_suite_dhm.data
@@ -19,10 +19,13 @@ 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:"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":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 a6a642306..6764359fe 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -673,9 +673,12 @@ 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 303e2f47d47b46fd4e17bd416f6a46c3c1a67c2a 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 03/12] 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 65ad4cff7be23bc34cde1403e81ca8685fc3045f 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 04/12] 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 64f0ca306..3b71c3569 100644
--- a/tests/suites/test_suite_dhm.data
+++ b/tests/suites/test_suite_dhm.data
@@ -19,8 +19,11 @@ 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 4fd8fff23..2d1ef26f7 100644
--- a/tests/suites/test_suite_dhm.function
+++ b/tests/suites/test_suite_dhm.function
@@ -99,6 +99,36 @@ 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 6764359fe..5ac0d6d43 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -676,8 +676,17 @@ 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:"50000000000000000000000000000000000000000000000000000000100014e4c3111300f060355040a13086f53534c00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000052b810400224ee06ec30e5753333958e280a8000000809539c2885280afd66aab21ddb8d31c6e58b8cae8b2698ef341ad29c3b45f75a7476fd5192955699a533b20b4661660341e00000040000000160000000000001604149d316d202449023f2bcb78b519bc7fffc9cbfb357c316e0603cdcdcdcd0ba34677b8b3be2c3633023100fdbfff7b67df9d7b7f7f00476fd5192955699a533b20b4661660341e00000040000000160000000000001604149d316d202449023f2bcb78b519bc7fffc9cbfb357c316e0603cdcdcdcd0ba34677b8b3be2c3633023100fdbfff7b67df9d7b7f7f000000000001000400000000000000506f6c617253530000000000000000000000000000000000000000110000f6de000000000000000000000000000000000000000000000000000000000000000000000000000000000000004c323536193017060000004f000000000000000000000005000000000000000000000000001603030039020000350303cf02020244e8786d95de3d020202e101f2f34e75c8b70a610e44c1000000000000008400000d00a30000ff60010001000016000016030102660b00026200025f00025c30820258308201c1a003020102020900fbb04c2eab109b0c300d06092a864886f70d01010505003045310b3009060355040e130241553113301106035504080c0a536f6d654853746174653121301f060355040a0c18496e7465726e6574205769646769747320507479204c7464301e170d3134303732333230353034305a170d3137303432323230353034305a3045310b3009060355042e130241553113301106035574080c0a136f6d652d53746174653121301f06035504050c18496e7465726e6574205769646769747320507479204c746430819f300d06092a864886f70d010101050003818d003081890281816602ffffff9e000000000000020000bf1400000000000100000000000000feffef00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001e1e1e001e1e1e1e1e00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000050000000000000000000000000000000000000000000000000000000000000000000000000000000000040ffd0100010000160000000000000000000000000000ff00000008000000000000000000000000000000000000000000000000000000000000000000000100014e4c3111300f060355040a13086f53534c00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000052b810400224ee06ec30e5753333958e280a8000000809539c2885280afd66aab21ddb8d31c6e58b8cae8b2698ef341ad29c3b45f75a7476fd5192955699a533b20b4661660341e00000040000000160000000000001604149d316d202449023f2bcb78b519bc7fffc9cbfb357c316e0603cdcdcdcd0ba34677b8b3be2c3633023100fdbfff7b67df9d7b7f7f00476fd5192955699a533b20b4661660341e00000040000000160000000000001604149d316d202449023f2bcb78b519bc7fffc9cbfb357c316e0603cdcdcdcd0ba34677b8b3be2c3633023100fdbfff7b67df9d7b7f7f000000000001000400000000000000506f6c617253530000000000000000000000000000000000000000110000f6de000000000000000000000000000000000000000000000000000000000000000000000000000000000000004c323536193017060000004f000000000000000000000005000000000000000000000000001603030039020000350303cf02020244e8786d95de3d020202e101f2f34e75c8b70a610e44c1000000000000008400000d00a30000ff60010001000016000016030102660b00026200025f00025c30820258308201c1a003020102020900fbb04c2eab109b0c300d06092a864886f70dc9784adc17e9e82f4cadccc1747090a92f8ca6840c0f404db671d219301706035504031310506f6c617253534c205465737420434130820122300d06092a864886f70d0101010500038201160303005b02000057030367c6699151ff4aec29cdbaabf2fbe3467cc254f81be8e78d765a2e63339fc99a2009fc99a2066310db7315864fc99a2066320db73058a3ff7f00001758e942d4abb2cdc64e9bb43ddc87c03db1b28d17e02cb23":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 6f5abf3b8..d1a96b68a 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -899,6 +899,37 @@ 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, int div_result )

From 2facdeeadfbc1773ebb140b77fa6c02c1c5d6066 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 05/12] 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 5ac0d6d43..4261f053a 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -688,6 +688,12 @@ 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 2f7d147dc8dd4ea15c626b99d37cd0c2a3baa1dd 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 06/12] 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 4261f053a..fcef9c648 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -676,22 +676,22 @@ 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 d1a96b68a..0c5781c85 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -901,28 +901,31 @@ 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 263320505b68c986f262d45be09870e7acc464a9 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 07/12] 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 fcef9c648..68b88372e 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -677,10 +677,10 @@ 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 d6e113fcbe0bf3677a95f7742ea0e6d7b492f635 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 08/12] 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 0c5781c85..b0ebee416 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
 {
     uint8_t     *data;
@@ -868,7 +872,7 @@ 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, char *input_X, int div_result )

From 942774eb528c7a285c03e68f65bfd6cc7f34ab5b 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 09/12] 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 68b88372e..11ec6c85b 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -695,12 +695,14 @@ 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 b0ebee416..d7fe6b9bf 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -872,7 +872,7 @@ 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, char *input_X, int div_result )

From 419c1046104e41cd93e323abb4725550034f0011 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 10/12] 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 ede3addc1714c45787475c6949d525db481bb522 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 11/12] 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 2d1ef26f7..9f1f1ff2f 100644
--- a/tests/suites/test_suite_dhm.function
+++ b/tests/suites/test_suite_dhm.function
@@ -119,7 +119,7 @@ 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 43e7acd3b457706c7502e7a0353e1edd9f28567f 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 12/12] 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 11ec6c85b..f625d7315 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -695,14 +695,14 @@ 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 d7fe6b9bf..5bf4c2775 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