diff --git a/ChangeLog b/ChangeLog index 683240ae5..1e3ffbfbc 100644 --- a/ChangeLog +++ b/ChangeLog @@ -16,6 +16,15 @@ Security plaintexts and forge RSA signatures. Other asymmetric algorithms may have been similarly vulnerable. Reported by Eyal Ronen, Robert Gillham, Daniel Genkin, Adi Shamir, David Wong and Yuval Yarom. + * Wipe sensitive buffers on the stack in the CTR_DRBG and HMAC_DRBG + modules. + +API Changes + * The new functions mbedtls_ctr_drbg_update_ret() and + mbedtls_hmac_drbg_update_ret() are similar to mbedtls_ctr_drbg_update() + and mbedtls_hmac_drbg_update() respectively, but the new functions + report errors whereas the old functions return void. We recommend that + applications use the new functions. = mbed TLS 2.14.0 branch released 2018-11-19 diff --git a/include/mbedtls/ctr_drbg.h b/include/mbedtls/ctr_drbg.h index c91ca58b3..304bc911c 100644 --- a/include/mbedtls/ctr_drbg.h +++ b/include/mbedtls/ctr_drbg.h @@ -237,20 +237,41 @@ int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx, const unsigned char *additional, size_t len ); /** - * \brief This function updates the state of the CTR_DRBG context. + * \brief This function updates the state of the CTR_DRBG context. * - * \note If \p add_len is greater than - * #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT, only the first - * #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT Bytes are used. - * The remaining Bytes are silently discarded. + * \param ctx The CTR_DRBG context. + * \param additional The data to update the state with. + * \param add_len Length of \p additional in bytes. This must be at + * most #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT. * - * \param ctx The CTR_DRBG context. - * \param additional The data to update the state with. - * \param add_len Length of \p additional data. + * \return \c 0 on success. + * \return #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG if + * \p add_len is more than + * #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT. + * \return An error from the underlying AES cipher on failure. + */ +int mbedtls_ctr_drbg_update_ret( mbedtls_ctr_drbg_context *ctx, + const unsigned char *additional, + size_t add_len ); + +/** + * \brief This function updates the state of the CTR_DRBG context. * + * \warning This function cannot report errors. You should use + * mbedtls_ctr_drbg_update_ret() instead. + * + * \note If \p add_len is greater than + * #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT, only the first + * #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT Bytes are used. + * The remaining Bytes are silently discarded. + * + * \param ctx The CTR_DRBG context. + * \param additional The data to update the state with. + * \param add_len Length of \p additional data. */ void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx, - const unsigned char *additional, size_t add_len ); + const unsigned char *additional, + size_t add_len ); /** * \brief This function updates a CTR_DRBG instance with additional diff --git a/include/mbedtls/hmac_drbg.h b/include/mbedtls/hmac_drbg.h index 3bc675ec7..2e1108b0b 100644 --- a/include/mbedtls/hmac_drbg.h +++ b/include/mbedtls/hmac_drbg.h @@ -195,11 +195,31 @@ void mbedtls_hmac_drbg_set_reseed_interval( mbedtls_hmac_drbg_context *ctx, * \param additional Additional data to update state with, or NULL * \param add_len Length of additional data, or 0 * + * \return \c 0 on success, or an error from the underlying + * hash calculation. + * + * \note Additional data is optional, pass NULL and 0 as second + * third argument if no additional data is being used. + */ +int mbedtls_hmac_drbg_update_ret( mbedtls_hmac_drbg_context *ctx, + const unsigned char *additional, size_t add_len ); + +/** + * \brief HMAC_DRBG update state + * + * \warning This function cannot report errors. You should use + * mbedtls_hmac_drbg_update_ret() instead. + * + * \param ctx HMAC_DRBG context + * \param additional Additional data to update state with, or NULL + * \param add_len Length of additional data, or 0 + * * \note Additional data is optional, pass NULL and 0 as second * third argument if no additional data is being used. */ void mbedtls_hmac_drbg_update( mbedtls_hmac_drbg_context *ctx, - const unsigned char *additional, size_t add_len ); + const unsigned char *additional, + size_t add_len ); /** * \brief HMAC_DRBG reseeding (extracts data from entropy source) diff --git a/library/ctr_drbg.c b/library/ctr_drbg.c index fead18f72..0655e7652 100644 --- a/library/ctr_drbg.c +++ b/library/ctr_drbg.c @@ -299,9 +299,7 @@ static int ctr_drbg_update_internal( mbedtls_ctr_drbg_context *ctx, * Crypt counter block */ if( ( ret = mbedtls_aes_crypt_ecb( &ctx->aes_ctx, MBEDTLS_AES_ENCRYPT, ctx->counter, p ) ) != 0 ) - { - return( ret ); - } + goto exit; p += MBEDTLS_CTR_DRBG_BLOCKSIZE; } @@ -313,12 +311,12 @@ static int ctr_drbg_update_internal( mbedtls_ctr_drbg_context *ctx, * Update key and counter */ if( ( ret = mbedtls_aes_setkey_enc( &ctx->aes_ctx, tmp, MBEDTLS_CTR_DRBG_KEYBITS ) ) != 0 ) - { - return( ret ); - } + goto exit; memcpy( ctx->counter, tmp + MBEDTLS_CTR_DRBG_KEYSIZE, MBEDTLS_CTR_DRBG_BLOCKSIZE ); - return( 0 ); +exit: + mbedtls_platform_zeroize( tmp, sizeof( tmp ) ); + return( ret ); } /* CTR_DRBG_Instantiate with derivation function (SP 800-90A §10.2.1.3.2) @@ -333,21 +331,36 @@ static int ctr_drbg_update_internal( mbedtls_ctr_drbg_context *ctx, * and with outputs * ctx = initial_working_state */ -void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx, - const unsigned char *additional, size_t add_len ) +int mbedtls_ctr_drbg_update_ret( mbedtls_ctr_drbg_context *ctx, + const unsigned char *additional, + size_t add_len ) { unsigned char add_input[MBEDTLS_CTR_DRBG_SEEDLEN]; + int ret; - if( add_len > 0 ) - { - /* MAX_INPUT would be more logical here, but we have to match - * block_cipher_df()'s limits since we can't propagate errors */ - if( add_len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT ) - add_len = MBEDTLS_CTR_DRBG_MAX_SEED_INPUT; + if( add_len == 0 ) + return( 0 ); - block_cipher_df( add_input, additional, add_len ); - ctr_drbg_update_internal( ctx, add_input ); - } + if( ( ret = block_cipher_df( add_input, additional, add_len ) ) != 0 ) + goto exit; + if( ( ret = ctr_drbg_update_internal( ctx, add_input ) ) != 0 ) + goto exit; + +exit: + mbedtls_platform_zeroize( add_input, sizeof( add_input ) ); + return( ret ); +} + +/* Deprecated function, kept for backward compatibility. */ +void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx, + const unsigned char *additional, + size_t add_len ) +{ + /* MAX_INPUT would be more logical here, but we have to match + * block_cipher_df()'s limits since we can't propagate errors */ + if( add_len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT ) + add_len = MBEDTLS_CTR_DRBG_MAX_SEED_INPUT; + (void) mbedtls_ctr_drbg_update_ret( ctx, additional, add_len ); } /* CTR_DRBG_Reseed with derivation function (SP 800-90A §10.2.1.4.2) @@ -399,20 +412,18 @@ int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx, * Reduce to 384 bits */ if( ( ret = block_cipher_df( seed, seed, seedlen ) ) != 0 ) - { - return( ret ); - } + goto exit; /* * Update state */ if( ( ret = ctr_drbg_update_internal( ctx, seed ) ) != 0 ) - { - return( ret ); - } + goto exit; ctx->reseed_counter = 1; - return( 0 ); +exit: + mbedtls_platform_zeroize( seed, sizeof( seed ) ); + return( ret ); } /* CTR_DRBG_Generate with derivation function (SP 800-90A §10.2.1.5.2) @@ -467,13 +478,9 @@ int mbedtls_ctr_drbg_random_with_add( void *p_rng, if( add_len > 0 ) { if( ( ret = block_cipher_df( add_input, additional, add_len ) ) != 0 ) - { - return( ret ); - } + goto exit; if( ( ret = ctr_drbg_update_internal( ctx, add_input ) ) != 0 ) - { - return( ret ); - } + goto exit; } while( output_len > 0 ) @@ -489,9 +496,7 @@ int mbedtls_ctr_drbg_random_with_add( void *p_rng, * Crypt counter block */ if( ( ret = mbedtls_aes_crypt_ecb( &ctx->aes_ctx, MBEDTLS_AES_ENCRYPT, ctx->counter, tmp ) ) != 0 ) - { - return( ret ); - } + goto exit; use_len = ( output_len > MBEDTLS_CTR_DRBG_BLOCKSIZE ) ? MBEDTLS_CTR_DRBG_BLOCKSIZE : output_len; @@ -504,12 +509,13 @@ int mbedtls_ctr_drbg_random_with_add( void *p_rng, } if( ( ret = ctr_drbg_update_internal( ctx, add_input ) ) != 0 ) - { - return( ret ); - } + goto exit; ctx->reseed_counter++; +exit: + mbedtls_platform_zeroize( add_input, sizeof( add_input ) ); + mbedtls_platform_zeroize( tmp, sizeof( tmp ) ); return( 0 ); } @@ -581,7 +587,7 @@ int mbedtls_ctr_drbg_update_seed_file( mbedtls_ctr_drbg_context *ctx, const char if( fread( buf, 1, n, f ) != n ) ret = MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR; else - mbedtls_ctr_drbg_update( ctx, buf, n ); + ret = mbedtls_ctr_drbg_update_ret( ctx, buf, n ); fclose( f ); diff --git a/library/hmac_drbg.c b/library/hmac_drbg.c index dad55ff86..73c606b99 100644 --- a/library/hmac_drbg.c +++ b/library/hmac_drbg.c @@ -66,29 +66,56 @@ void mbedtls_hmac_drbg_init( mbedtls_hmac_drbg_context *ctx ) /* * HMAC_DRBG update, using optional additional data (10.1.2.2) */ -void mbedtls_hmac_drbg_update( mbedtls_hmac_drbg_context *ctx, - const unsigned char *additional, size_t add_len ) +int mbedtls_hmac_drbg_update_ret( mbedtls_hmac_drbg_context *ctx, + const unsigned char *additional, + size_t add_len ) { size_t md_len = mbedtls_md_get_size( ctx->md_ctx.md_info ); unsigned char rounds = ( additional != NULL && add_len != 0 ) ? 2 : 1; unsigned char sep[1]; unsigned char K[MBEDTLS_MD_MAX_SIZE]; + int ret; for( sep[0] = 0; sep[0] < rounds; sep[0]++ ) { /* Step 1 or 4 */ - mbedtls_md_hmac_reset( &ctx->md_ctx ); - mbedtls_md_hmac_update( &ctx->md_ctx, ctx->V, md_len ); - mbedtls_md_hmac_update( &ctx->md_ctx, sep, 1 ); + if( ( ret = mbedtls_md_hmac_reset( &ctx->md_ctx ) ) != 0 ) + goto exit; + if( ( ret = mbedtls_md_hmac_update( &ctx->md_ctx, + ctx->V, md_len ) ) != 0 ) + goto exit; + if( ( ret = mbedtls_md_hmac_update( &ctx->md_ctx, + sep, 1 ) ) != 0 ) + goto exit; if( rounds == 2 ) - mbedtls_md_hmac_update( &ctx->md_ctx, additional, add_len ); - mbedtls_md_hmac_finish( &ctx->md_ctx, K ); + { + if( ( ret = mbedtls_md_hmac_update( &ctx->md_ctx, + additional, add_len ) ) != 0 ) + goto exit; + } + if( ( ret = mbedtls_md_hmac_finish( &ctx->md_ctx, K ) ) != 0 ) + goto exit; /* Step 2 or 5 */ - mbedtls_md_hmac_starts( &ctx->md_ctx, K, md_len ); - mbedtls_md_hmac_update( &ctx->md_ctx, ctx->V, md_len ); - mbedtls_md_hmac_finish( &ctx->md_ctx, ctx->V ); + if( ( ret = mbedtls_md_hmac_starts( &ctx->md_ctx, K, md_len ) ) != 0 ) + goto exit; + if( ( ret = mbedtls_md_hmac_update( &ctx->md_ctx, + ctx->V, md_len ) ) != 0 ) + goto exit; + if( ( ret = mbedtls_md_hmac_finish( &ctx->md_ctx, ctx->V ) ) != 0 ) + goto exit; } + +exit: + mbedtls_platform_zeroize( K, sizeof( K ) ); + return( ret ); +} + +void mbedtls_hmac_drbg_update( mbedtls_hmac_drbg_context *ctx, + const unsigned char *additional, + size_t add_len ) +{ + (void) mbedtls_hmac_drbg_update_ret( ctx, additional, add_len ); } /* @@ -108,10 +135,13 @@ int mbedtls_hmac_drbg_seed_buf( mbedtls_hmac_drbg_context *ctx, * Use the V memory location, which is currently all 0, to initialize the * MD context with an all-zero key. Then set V to its initial value. */ - mbedtls_md_hmac_starts( &ctx->md_ctx, ctx->V, mbedtls_md_get_size( md_info ) ); + if( ( ret = mbedtls_md_hmac_starts( &ctx->md_ctx, ctx->V, + mbedtls_md_get_size( md_info ) ) ) != 0 ) + return( ret ); memset( ctx->V, 0x01, mbedtls_md_get_size( md_info ) ); - mbedtls_hmac_drbg_update( ctx, data, data_len ); + if( ( ret = mbedtls_hmac_drbg_update_ret( ctx, data, data_len ) ) != 0 ) + return( ret ); return( 0 ); } @@ -124,6 +154,7 @@ int mbedtls_hmac_drbg_reseed( mbedtls_hmac_drbg_context *ctx, { unsigned char seed[MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT]; size_t seedlen; + int ret; /* III. Check input length */ if( len > MBEDTLS_HMAC_DRBG_MAX_INPUT || @@ -135,7 +166,8 @@ int mbedtls_hmac_drbg_reseed( mbedtls_hmac_drbg_context *ctx, memset( seed, 0, MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT ); /* IV. Gather entropy_len bytes of entropy for the seed */ - if( ctx->f_entropy( ctx->p_entropy, seed, ctx->entropy_len ) != 0 ) + if( ( ret = ctx->f_entropy( ctx->p_entropy, + seed, ctx->entropy_len ) ) != 0 ) return( MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED ); seedlen = ctx->entropy_len; @@ -148,13 +180,16 @@ int mbedtls_hmac_drbg_reseed( mbedtls_hmac_drbg_context *ctx, } /* 2. Update state */ - mbedtls_hmac_drbg_update( ctx, seed, seedlen ); + if( ( ret = mbedtls_hmac_drbg_update_ret( ctx, seed, seedlen ) ) != 0 ) + goto exit; /* 3. Reset reseed_counter */ ctx->reseed_counter = 1; +exit: /* 4. Done */ - return( 0 ); + mbedtls_platform_zeroize( seed, seedlen ); + return( ret ); } /* @@ -180,7 +215,8 @@ int mbedtls_hmac_drbg_seed( mbedtls_hmac_drbg_context *ctx, * Use the V memory location, which is currently all 0, to initialize the * MD context with an all-zero key. Then set V to its initial value. */ - mbedtls_md_hmac_starts( &ctx->md_ctx, ctx->V, md_size ); + if( ( ret = mbedtls_md_hmac_starts( &ctx->md_ctx, ctx->V, md_size ) ) != 0 ) + return( ret ); memset( ctx->V, 0x01, md_size ); ctx->f_entropy = f_entropy; @@ -273,16 +309,24 @@ int mbedtls_hmac_drbg_random_with_add( void *p_rng, /* 2. Use additional data if any */ if( additional != NULL && add_len != 0 ) - mbedtls_hmac_drbg_update( ctx, additional, add_len ); + { + if( ( ret = mbedtls_hmac_drbg_update_ret( ctx, + additional, add_len ) ) != 0 ) + goto exit; + } /* 3, 4, 5. Generate bytes */ while( left != 0 ) { size_t use_len = left > md_len ? md_len : left; - mbedtls_md_hmac_reset( &ctx->md_ctx ); - mbedtls_md_hmac_update( &ctx->md_ctx, ctx->V, md_len ); - mbedtls_md_hmac_finish( &ctx->md_ctx, ctx->V ); + if( ( ret = mbedtls_md_hmac_reset( &ctx->md_ctx ) ) != 0 ) + goto exit; + if( ( ret = mbedtls_md_hmac_update( &ctx->md_ctx, + ctx->V, md_len ) ) != 0 ) + goto exit; + if( ( ret = mbedtls_md_hmac_finish( &ctx->md_ctx, ctx->V ) ) != 0 ) + goto exit; memcpy( out, ctx->V, use_len ); out += use_len; @@ -290,13 +334,16 @@ int mbedtls_hmac_drbg_random_with_add( void *p_rng, } /* 6. Update */ - mbedtls_hmac_drbg_update( ctx, additional, add_len ); + if( ( ret = mbedtls_hmac_drbg_update_ret( ctx, + additional, add_len ) ) != 0 ) + goto exit; /* 7. Update reseed counter */ ctx->reseed_counter++; +exit: /* 8. Done */ - return( 0 ); + return( ret ); } /* @@ -388,7 +435,7 @@ int mbedtls_hmac_drbg_update_seed_file( mbedtls_hmac_drbg_context *ctx, const ch if( fread( buf, 1, n, f ) != n ) ret = MBEDTLS_ERR_HMAC_DRBG_FILE_IO_ERROR; else - mbedtls_hmac_drbg_update( ctx, buf, n ); + ret = mbedtls_hmac_drbg_update_ret( ctx, buf, n ); fclose( f ); diff --git a/tests/suites/test_suite_ctr_drbg.function b/tests/suites/test_suite_ctr_drbg.function index f10e98aa5..4a97826f6 100644 --- a/tests/suites/test_suite_ctr_drbg.function +++ b/tests/suites/test_suite_ctr_drbg.function @@ -244,9 +244,11 @@ void ctr_drbg_entropy_usage( ) } TEST_ASSERT( last_idx == test_offset_idx ); - /* Call update with too much data (sizeof entropy > MAX(_SEED)_INPUT) - * (just make sure it doesn't cause memory corruption) */ - mbedtls_ctr_drbg_update( &ctx, entropy, sizeof( entropy ) ); + /* Call update with too much data (sizeof entropy > MAX(_SEED)_INPUT). + * Make sure it's detected as an error and doesn't cause memory + * corruption. */ + TEST_ASSERT( mbedtls_ctr_drbg_update_ret( + &ctx, entropy, sizeof( entropy ) ) != 0 ); /* Now enable PR, so the next few calls should all reseed */ mbedtls_ctr_drbg_set_prediction_resistance( &ctx, MBEDTLS_CTR_DRBG_PR_ON );