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CTR_DRBG: clean stack buffers

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Wipe stack buffers that may contain sensitive data (data that
contributes to the DRBG state.
This commit is contained in:
Gilles Peskine 2018-09-11 15:34:17 +02:00
parent 556d7d9e3b
commit e495a8ae35
1 changed files with 18 additions and 26 deletions
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44
library/ctr_drbg.c
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@ -299,9 +299,7 @@ static int ctr_drbg_update_internal( mbedtls_ctr_drbg_context *ctx,
* Crypt counter block * Crypt counter block
*/ */
if( ( ret = mbedtls_aes_crypt_ecb( &ctx->aes_ctx, MBEDTLS_AES_ENCRYPT, ctx->counter, p ) ) != 0 ) if( ( ret = mbedtls_aes_crypt_ecb( &ctx->aes_ctx, MBEDTLS_AES_ENCRYPT, ctx->counter, p ) ) != 0 )
{ goto exit;
return( ret );
}
p += MBEDTLS_CTR_DRBG_BLOCKSIZE; p += MBEDTLS_CTR_DRBG_BLOCKSIZE;
} }
@ -313,12 +311,12 @@ static int ctr_drbg_update_internal( mbedtls_ctr_drbg_context *ctx,
* Update key and counter * Update key and counter
*/ */
if( ( ret = mbedtls_aes_setkey_enc( &ctx->aes_ctx, tmp, MBEDTLS_CTR_DRBG_KEYBITS ) ) != 0 ) if( ( ret = mbedtls_aes_setkey_enc( &ctx->aes_ctx, tmp, MBEDTLS_CTR_DRBG_KEYBITS ) ) != 0 )
{ goto exit;
return( ret );
}
memcpy( ctx->counter, tmp + MBEDTLS_CTR_DRBG_KEYSIZE, MBEDTLS_CTR_DRBG_BLOCKSIZE ); 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) /* CTR_DRBG_Instantiate with derivation function (SP 800-90A §10.2.1.3.2)
@ -347,6 +345,7 @@ void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx,
block_cipher_df( add_input, additional, add_len ); block_cipher_df( add_input, additional, add_len );
ctr_drbg_update_internal( ctx, add_input ); ctr_drbg_update_internal( ctx, add_input );
mbedtls_platform_zeroize( add_input, sizeof( add_input ) );
} }
} }
@ -399,20 +398,18 @@ int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx,
* Reduce to 384 bits * Reduce to 384 bits
*/ */
if( ( ret = block_cipher_df( seed, seed, seedlen ) ) != 0 ) if( ( ret = block_cipher_df( seed, seed, seedlen ) ) != 0 )
{ goto exit;
return( ret );
}
/* /*
* Update state * Update state
*/ */
if( ( ret = ctr_drbg_update_internal( ctx, seed ) ) != 0 ) if( ( ret = ctr_drbg_update_internal( ctx, seed ) ) != 0 )
{ goto exit;
return( ret );
}
ctx->reseed_counter = 1; 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) /* CTR_DRBG_Generate with derivation function (SP 800-90A §10.2.1.5.2)
@ -467,13 +464,9 @@ int mbedtls_ctr_drbg_random_with_add( void *p_rng,
if( add_len > 0 ) if( add_len > 0 )
{ {
if( ( ret = block_cipher_df( add_input, additional, add_len ) ) != 0 ) if( ( ret = block_cipher_df( add_input, additional, add_len ) ) != 0 )
{ goto exit;
return( ret );
}
if( ( ret = ctr_drbg_update_internal( ctx, add_input ) ) != 0 ) if( ( ret = ctr_drbg_update_internal( ctx, add_input ) ) != 0 )
{ goto exit;
return( ret );
}
} }
while( output_len > 0 ) while( output_len > 0 )
@ -489,9 +482,7 @@ int mbedtls_ctr_drbg_random_with_add( void *p_rng,
* Crypt counter block * Crypt counter block
*/ */
if( ( ret = mbedtls_aes_crypt_ecb( &ctx->aes_ctx, MBEDTLS_AES_ENCRYPT, ctx->counter, tmp ) ) != 0 ) if( ( ret = mbedtls_aes_crypt_ecb( &ctx->aes_ctx, MBEDTLS_AES_ENCRYPT, ctx->counter, tmp ) ) != 0 )
{ goto exit;
return( ret );
}
use_len = ( output_len > MBEDTLS_CTR_DRBG_BLOCKSIZE ) ? MBEDTLS_CTR_DRBG_BLOCKSIZE : use_len = ( output_len > MBEDTLS_CTR_DRBG_BLOCKSIZE ) ? MBEDTLS_CTR_DRBG_BLOCKSIZE :
output_len; output_len;
@ -504,12 +495,13 @@ int mbedtls_ctr_drbg_random_with_add( void *p_rng,
} }
if( ( ret = ctr_drbg_update_internal( ctx, add_input ) ) != 0 ) if( ( ret = ctr_drbg_update_internal( ctx, add_input ) ) != 0 )
{ goto exit;
return( ret );
}
ctx->reseed_counter++; ctx->reseed_counter++;
exit:
mbedtls_platform_zeroize( add_input, sizeof( add_input ) );
mbedtls_platform_zeroize( tmp, sizeof( tmp ) );
return( 0 ); return( 0 );
} }