eden-emu/mbedtls
15
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Split tag handling out of cipher_finish()

Browse source
This commit is contained in:
Manuel Pégourié-Gonnard 2013-09-03 16:19:22 +02:00
parent 2adc40c346
commit aa9ffc5e98
6 changed files with 88 additions and 54 deletions
Download patch file Download diff file Expand all files Collapse all files

73
library/cipher.c
View file

@ -777,8 +777,7 @@ static int get_no_padding( unsigned char *input, size_t input_len,
}
int cipher_finish( cipher_context_t *ctx,
unsigned char *output, size_t *olen,
unsigned char *tag, size_t tag_len )
unsigned char *output, size_t *olen )
{
int ret = 0;
@ -797,10 +796,6 @@ int cipher_finish( cipher_context_t *ctx,
#if defined(POLARSSL_GCM_C)
if( POLARSSL_MODE_GCM == ctx->cipher_info->mode )
{
unsigned char check_tag[16];
size_t i;
int diff;
if( 0 != ( ret = gcm_update( ctx->cipher_ctx,
ctx->unprocessed_len, ctx->unprocessed_data,
output ) ) )
@ -810,29 +805,8 @@ int cipher_finish( cipher_context_t *ctx,
*olen += ctx->unprocessed_len;
if( 0 != ( ret = gcm_finish( ctx->cipher_ctx, check_tag, tag_len ) ) )
return( ret );
/* On encryption, write the tag */
if( POLARSSL_ENCRYPT == ctx->operation )
{
if( tag_len != 0 )
memcpy( tag, check_tag, tag_len );
return( 0 );
}
/* On decryption, check the tag (in "constant-time") */
for( diff = 0, i = 0; i < tag_len; i++ )
diff |= tag[i] ^ check_tag[i];
if( diff != 0 )
return( POLARSSL_ERR_GCM_AUTH_FAILED );
return( 0 );
}
#else
((void) tag);
((void) tag_len);
#endif
if( POLARSSL_MODE_CBC == ctx->cipher_info->mode )
@ -930,6 +904,51 @@ int cipher_set_padding_mode( cipher_context_t *ctx, cipher_padding_t mode )
return 0;
}
int cipher_write_tag( cipher_context_t *ctx,
unsigned char *tag, size_t tag_len )
{
if( NULL == ctx || NULL == ctx->cipher_info || NULL == tag )
return POLARSSL_ERR_CIPHER_BAD_INPUT_DATA;
if( POLARSSL_MODE_GCM != ctx->cipher_info->mode )
return( 0 );
if( POLARSSL_ENCRYPT != ctx->operation )
return POLARSSL_ERR_CIPHER_BAD_INPUT_DATA;
return gcm_finish( ctx->cipher_ctx, tag, tag_len );
}
int cipher_check_tag( cipher_context_t *ctx,
const unsigned char *tag, size_t tag_len )
{
int ret;
unsigned char check_tag[16];
size_t i;
int diff;
if( NULL == ctx || NULL == ctx->cipher_info )
return POLARSSL_ERR_CIPHER_BAD_INPUT_DATA;
if( POLARSSL_MODE_GCM != ctx->cipher_info->mode )
return( 0 );
if( POLARSSL_DECRYPT != ctx->operation || tag_len > sizeof( check_tag ) )
return POLARSSL_ERR_CIPHER_BAD_INPUT_DATA;
if( 0 != ( ret = gcm_finish( ctx->cipher_ctx, check_tag, tag_len ) ) )
return( ret );
/* On decryption, check the tag (in "constant-time") */
for( diff = 0, i = 0; i < tag_len; i++ )
diff |= tag[i] ^ check_tag[i];
if( diff != 0 )
return( POLARSSL_ERR_GCM_AUTH_FAILED );
return( 0 );
}
#if defined(POLARSSL_SELF_TEST)
#include <stdio.h>