Merge remote-tracking branch 'upstream-restricted/pr/351' into development-restricted-proposed

Move the added ChangeLog entry to the bottom so that the list remains
in merge order.

ChangeLog

@@ -17,6 +17,8 @@ Security
      implementation allowed an offline 2^80 brute force attack on the
      HMAC key of a single, uninterrupted connection (with no
      resumption of the session).
+   * Verify results of RSA private key operations to defend
+     against Bellcore glitch attack.
 
 Features
    * Extend PKCS#8 interface by introducing support for the entire SHA

include/mbedtls/config.h

@@ -1049,7 +1049,8 @@
 /**
  * \def MBEDTLS_RSA_NO_CRT
  *
- * Do not use the Chinese Remainder Theorem for the RSA private operation.
+ * Do not use the Chinese Remainder Theorem
+ * for the RSA private operation.
  *
  * Uncomment this macro to disable the use of CRT in RSA.
  *

include/mbedtls/rsa.h

@@ -518,6 +518,18 @@ int mbedtls_rsa_public( mbedtls_rsa_context *ctx,
  *
  * \note           The input and output buffers must be large
  *                 enough. For example, 128 Bytes if RSA-1024 is used.
+ *
+ * \note           Blinding is used if and only if a PRNG is provided.
+ *
+ * \note           If blinding is used, both the base of exponentation
+ *                 and the exponent are blinded, providing protection
+ *                 against some side-channel attacks.
+ *
+ * \warning        It is deprecated and a security risk to not provide
+ *                 a PRNG here and thereby prevent the use of blinding.
+ *                 Future versions of the library may enforce the presence
+ *                 of a PRNG.
+ *
  */
 int mbedtls_rsa_private( mbedtls_rsa_context *ctx,
                  int (*f_rng)(void *, unsigned char *, size_t),

library/bignum.c

@@ -1623,7 +1623,7 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
     mbedtls_mpi RR, T, W[ 2 << MBEDTLS_MPI_WINDOW_SIZE ], Apos;
     int neg;
 
-    if( mbedtls_mpi_cmp_int( N, 0 ) < 0 || ( N->p[0] & 1 ) == 0 )
+    if( mbedtls_mpi_cmp_int( N, 0 ) <= 0 || ( N->p[0] & 1 ) == 0 )
         return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
 
     if( mbedtls_mpi_cmp_int( E, 0 ) < 0 )

library/rsa.c

@@ -773,16 +773,38 @@ int mbedtls_rsa_private( mbedtls_rsa_context *ctx,
 {
     int ret;
     size_t olen;
-    mbedtls_mpi T, T1, T2;
+
+    /* Temporary holding the result */
+    mbedtls_mpi T;
+
+    /* Temporaries holding P-1, Q-1 and the
+     * exponent blinding factor, respectively. */
     mbedtls_mpi P1, Q1, R;
-#if defined(MBEDTLS_RSA_NO_CRT)
-    mbedtls_mpi D_blind;
-    mbedtls_mpi *D = &ctx->D;
-#else
+
+#if !defined(MBEDTLS_RSA_NO_CRT)
+    /* Temporaries holding the results mod p resp. mod q. */
+    mbedtls_mpi TP, TQ;
+
+    /* Temporaries holding the blinded exponents for
+     * the mod p resp. mod q computation (if used). */
     mbedtls_mpi DP_blind, DQ_blind;
+
+    /* Pointers to actual exponents to be used - either the unblinded
+     * or the blinded ones, depending on the presence of a PRNG. */
     mbedtls_mpi *DP = &ctx->DP;
     mbedtls_mpi *DQ = &ctx->DQ;
-#endif
+#else
+    /* Temporary holding the blinded exponent (if used). */
+    mbedtls_mpi D_blind;
+
+    /* Pointer to actual exponent to be used - either the unblinded
+     * or the blinded one, depending on the presence of a PRNG. */
+    mbedtls_mpi *D = &ctx->D;
+#endif /* MBEDTLS_RSA_NO_CRT */
+
+    /* Temporaries holding the initial input and the double
+     * checked result; should be the same in the end. */
+    mbedtls_mpi I, C;
 
     if( rsa_check_context( ctx, 1             /* private key checks */,
                                 f_rng != NULL /* blinding y/n       */ ) != 0 )
@@ -790,8 +812,17 @@ int mbedtls_rsa_private( mbedtls_rsa_context *ctx,
         return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
     }
 
-    mbedtls_mpi_init( &T ); mbedtls_mpi_init( &T1 ); mbedtls_mpi_init( &T2 );
-    mbedtls_mpi_init( &P1 ); mbedtls_mpi_init( &Q1 ); mbedtls_mpi_init( &R );
+#if defined(MBEDTLS_THREADING_C)
+    if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
+        return( ret );
+#endif
+
+    /* MPI Initialization */
+    mbedtls_mpi_init( &T );
+
+    mbedtls_mpi_init( &P1 );
+    mbedtls_mpi_init( &Q1 );
+    mbedtls_mpi_init( &R );
 
     if( f_rng != NULL )
     {
@@ -803,12 +834,15 @@ int mbedtls_rsa_private( mbedtls_rsa_context *ctx,
 #endif
     }
 
-
-#if defined(MBEDTLS_THREADING_C)
-    if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
-        return( ret );
+#if !defined(MBEDTLS_RSA_NO_CRT)
+    mbedtls_mpi_init( &TP ); mbedtls_mpi_init( &TQ );
 #endif
 
+    mbedtls_mpi_init( &I );
+    mbedtls_mpi_init( &C );
+
+    /* End of MPI initialization */
+
     MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &T, input, ctx->len ) );
     if( mbedtls_mpi_cmp_mpi( &T, &ctx->N ) >= 0 )
     {
@@ -816,6 +850,8 @@ int mbedtls_rsa_private( mbedtls_rsa_context *ctx,
         goto cleanup;
     }
 
+    MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &I, &T ) );
+
     if( f_rng != NULL )
     {
         /*
@@ -874,24 +910,25 @@ int mbedtls_rsa_private( mbedtls_rsa_context *ctx,
     /*
      * Faster decryption using the CRT
      *
-     * T1 = input ^ dP mod P
-     * T2 = input ^ dQ mod Q
+     * TP = input ^ dP mod P
+     * TQ = input ^ dQ mod Q
      */
-    MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &T1, &T, DP, &ctx->P, &ctx->RP ) );
-    MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &T2, &T, DQ, &ctx->Q, &ctx->RQ ) );
+
+    MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &TP, &T, DP, &ctx->P, &ctx->RP ) );
+    MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &TQ, &T, DQ, &ctx->Q, &ctx->RQ ) );
 
     /*
-     * T = (T1 - T2) * (Q^-1 mod P) mod P
+     * T = (TP - TQ) * (Q^-1 mod P) mod P
      */
-    MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( &T, &T1, &T2 ) );
-    MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &T1, &T, &ctx->QP ) );
-    MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &T, &T1, &ctx->P ) );
+    MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( &T, &TP, &TQ ) );
+    MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &TP, &T, &ctx->QP ) );
+    MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &T, &TP, &ctx->P ) );
 
     /*
-     * T = T2 + T * Q
+     * T = TQ + T * Q
      */
-    MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &T1, &T, &ctx->Q ) );
-    MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &T, &T2, &T1 ) );
+    MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &TP, &T, &ctx->Q ) );
+    MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &T, &TQ, &TP ) );
 #endif /* MBEDTLS_RSA_NO_CRT */
 
     if( f_rng != NULL )
@@ -904,6 +941,15 @@ int mbedtls_rsa_private( mbedtls_rsa_context *ctx,
         MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &T, &T, &ctx->N ) );
     }
 
+    /* Verify the result to prevent glitching attacks. */
+    MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &C, &T, &ctx->E,
+                                          &ctx->N, &ctx->RN ) );
+    if( mbedtls_mpi_cmp_mpi( &C, &I ) != 0 )
+    {
+        ret = MBEDTLS_ERR_RSA_VERIFY_FAILED;
+        goto cleanup;
+    }
+
     olen = ctx->len;
     MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &T, output, olen ) );
 
@@ -913,8 +959,9 @@ cleanup:
         return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
 #endif
 
-    mbedtls_mpi_free( &T ); mbedtls_mpi_free( &T1 ); mbedtls_mpi_free( &T2 );
-    mbedtls_mpi_free( &P1 ); mbedtls_mpi_free( &Q1 ); mbedtls_mpi_free( &R );
+    mbedtls_mpi_free( &P1 );
+    mbedtls_mpi_free( &Q1 );
+    mbedtls_mpi_free( &R );
 
     if( f_rng != NULL )
     {
@@ -926,6 +973,15 @@ cleanup:
 #endif
     }
 
+    mbedtls_mpi_free( &T );
+
+#if !defined(MBEDTLS_RSA_NO_CRT)
+    mbedtls_mpi_free( &TP ); mbedtls_mpi_free( &TQ );
+#endif
+
+    mbedtls_mpi_free( &C );
+    mbedtls_mpi_free( &I );
+
     if( ret != 0 )
         return( MBEDTLS_ERR_RSA_PRIVATE_FAILED + ret );
 
@@ -2222,7 +2278,8 @@ int mbedtls_rsa_self_test( int verbose )
         if( verbose != 0 )
             mbedtls_printf( "failed\n" );
 
-        return( 1 );
+        ret = 1;
+        goto cleanup;
     }
 
     if( verbose != 0 )
@@ -2237,7 +2294,8 @@ int mbedtls_rsa_self_test( int verbose )
         if( verbose != 0 )
             mbedtls_printf( "failed\n" );
 
-        return( 1 );
+        ret = 1;
+        goto cleanup;
     }
 
     if( verbose != 0 )
@@ -2250,7 +2308,8 @@ int mbedtls_rsa_self_test( int verbose )
         if( verbose != 0 )
             mbedtls_printf( "failed\n" );
 
-        return( 1 );
+        ret = 1;
+        goto cleanup;
     }
 
     if( memcmp( rsa_decrypted, rsa_plaintext, len ) != 0 )
@@ -2258,7 +2317,8 @@ int mbedtls_rsa_self_test( int verbose )
         if( verbose != 0 )
             mbedtls_printf( "failed\n" );
 
-        return( 1 );
+        ret = 1;
+        goto cleanup;
     }
 
     if( verbose != 0 )
@@ -2283,7 +2343,8 @@ int mbedtls_rsa_self_test( int verbose )
         if( verbose != 0 )
             mbedtls_printf( "failed\n" );
 
-        return( 1 );
+        ret = 1;
+        goto cleanup;
     }
 
     if( verbose != 0 )
@@ -2296,7 +2357,8 @@ int mbedtls_rsa_self_test( int verbose )
         if( verbose != 0 )
             mbedtls_printf( "failed\n" );
 
-        return( 1 );
+        ret = 1;
+        goto cleanup;
     }
 
     if( verbose != 0 )

scripts/config.pl

@@ -17,7 +17,7 @@
 #
 # Full usage description provided below.
 #
-# Things that shouldn't be enabled with "full".
+# The following options are disabled instead of enabled with "full".
 #
 #   MBEDTLS_TEST_NULL_ENTROPY
 #   MBEDTLS_DEPRECATED_REMOVED
@@ -30,6 +30,7 @@
 #   MBEDTLS_NO_PLATFORM_ENTROPY
 #   MBEDTLS_REMOVE_ARC4_CIPHERSUITES
 #   MBEDTLS_SSL_HW_RECORD_ACCEL
+#   MBEDTLS_RSA_NO_CRT
 #   MBEDTLS_X509_ALLOW_EXTENSIONS_NON_V3
 #   MBEDTLS_X509_ALLOW_UNSUPPORTED_CRITICAL_EXTENSION
 #       - this could be enabled if the respective tests were adapted
@@ -86,6 +87,7 @@ MBEDTLS_ECP_DP_M383_ENABLED
 MBEDTLS_ECP_DP_M511_ENABLED
 MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES
 MBEDTLS_NO_PLATFORM_ENTROPY
+MBEDTLS_RSA_NO_CRT
 MBEDTLS_REMOVE_ARC4_CIPHERSUITES
 MBEDTLS_SSL_HW_RECORD_ACCEL
 MBEDTLS_X509_ALLOW_EXTENSIONS_NON_V3

tests/scripts/all.sh

@@ -530,6 +530,22 @@ make test
 msg "test: !MBEDTLS_SSL_RENEGOTIATION - ssl-opt.sh (ASan build)" # ~ 6 min
 if_build_succeeded tests/ssl-opt.sh
 
+msg "build: Default + RSA_NO_CRT (ASan build)" # ~ 6 min
+cleanup
+cp "$CONFIG_H" "$CONFIG_BAK"
+scripts/config.pl set MBEDTLS_RSA_NO_CRT
+CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Asan .
+make
+
+msg "test: RSA_NO_CRT - main suites (inc. selftests) (ASan build)" # ~ 50s
+make test
+
+msg "test: RSA_NO_CRT - RSA-related part of ssl-opt.sh (ASan build)" # ~ 5s
+tests/ssl-opt.sh -f RSA
+
+msg "test: RSA_NO_CRT - RSA-related part of compat.sh (ASan build)" # ~ 3 min
+tests/compat.sh -t RSA
+
 msg "build: cmake, full config, clang, C99" # ~ 50s
 cleanup
 cp "$CONFIG_H" "$CONFIG_BAK"

tests/suites/test_suite_pk.function

@@ -43,7 +43,8 @@ int mbedtls_rsa_decrypt_func( void *ctx, int mode, size_t *olen,
                        const unsigned char *input, unsigned char *output,
                        size_t output_max_len )
 {
-    return( mbedtls_rsa_pkcs1_decrypt( (mbedtls_rsa_context *) ctx, NULL, NULL, mode, olen,
+    return( mbedtls_rsa_pkcs1_decrypt( (mbedtls_rsa_context *) ctx,
+                                       rnd_std_rand, NULL, mode, olen,
                                        input, output, output_max_len ) );
 }
 int mbedtls_rsa_sign_func( void *ctx,
@@ -51,7 +52,9 @@ int mbedtls_rsa_sign_func( void *ctx,
                    int mode, mbedtls_md_type_t md_alg, unsigned int hashlen,
                    const unsigned char *hash, unsigned char *sig )
 {
-    return( mbedtls_rsa_pkcs1_sign( (mbedtls_rsa_context *) ctx, f_rng, p_rng, mode,
+    ((void) f_rng);
+    ((void) p_rng);
+    return( mbedtls_rsa_pkcs1_sign( (mbedtls_rsa_context *) ctx, rnd_std_rand, NULL, mode,
                             md_alg, hashlen, hash, sig ) );
 }
 size_t mbedtls_rsa_key_len_func( void *ctx )
@@ -105,7 +108,8 @@ void mbedtls_pk_check_pair( char *pub_file, char *prv_file, int ret )
     if( mbedtls_pk_get_type( &prv ) == MBEDTLS_PK_RSA )
     {
         TEST_ASSERT( mbedtls_pk_setup_rsa_alt( &alt, mbedtls_pk_rsa( prv ),
-                     mbedtls_rsa_decrypt_func, mbedtls_rsa_sign_func, mbedtls_rsa_key_len_func ) == 0 );
+                     mbedtls_rsa_decrypt_func, mbedtls_rsa_sign_func,
+                     mbedtls_rsa_key_len_func ) == 0 );
         TEST_ASSERT( mbedtls_pk_check_pair( &pub, &alt ) == ret );
     }
 #endif