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Split tag handling out of cipher_finish()

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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
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35
include/polarssl/cipher.h
View File

@ -519,11 +519,6 @@ int cipher_update( cipher_context_t *ctx, const unsigned char *input, size_t ile
* \param ctx Generic cipher context
* \param output buffer to write data to. Needs block_size available.
* \param olen length of the data written to the output buffer.
* \param tag Ignore by non-AEAD ciphers. For AEAD ciphers:
* - on encryption: buffer to write the tag;
* - on decryption: tag to verify.
* May be NULL if tag_len is zero.
* \param tag_len Length of the tag to write/check for AEAD ciphers.
*
* \returns 0 on success, POLARSSL_ERR_CIPHER_BAD_INPUT_DATA if
* parameter verification fails,
@ -533,8 +528,34 @@ int cipher_update( cipher_context_t *ctx, const unsigned char *input, size_t ile
* while decrypting or a cipher specific error code.
*/
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 );
/**
* \brief Write tag for AEAD ciphers.
* No effect for other ciphers.
* Must be called after cipher_finish().
*
* \param tag buffer to write the tag
* \param tag_len Length of the tag to write
*
* \return 0 on success, or a specific error code.
*/
int cipher_write_tag( cipher_context_t *ctx,
unsigned char *tag, size_t tag_len );
/**
* \brief Check tag for AEAD ciphers.
* No effect for other ciphers.
* Calling time depends on the cipher:
* for GCM, must be called after cipher_finish().
*
* \param tag Buffer holding the tag
* \param tag_len Length of the tag to check
*
* \return 0 on success, or a specific error code.
*/
int cipher_check_tag( cipher_context_t *ctx,
const unsigned char *tag, size_t tag_len );
/**
* \brief Checkup routine

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>

5
library/pkcs12.c
View File

@ -196,11 +196,8 @@ int pkcs12_pbe( asn1_buf *pbe_params, int mode,
goto exit;
}
if( ( ret = cipher_finish( &cipher_ctx, output + olen, &olen, NULL, 0 ) )
!= 0 )
{
if( ( ret = cipher_finish( &cipher_ctx, output + olen, &olen ) ) != 0 )
ret = POLARSSL_ERR_PKCS12_PASSWORD_MISMATCH;
}
exit:
cipher_free_ctx( &cipher_ctx );

5
library/pkcs5.c
View File

@ -199,11 +199,8 @@ int pkcs5_pbes2( asn1_buf *pbe_params, int mode,
goto exit;
}
if( ( ret = cipher_finish( &cipher_ctx, output + olen, &olen, NULL, 0 ) )
!= 0 )
{
if( ( ret = cipher_finish( &cipher_ctx, output + olen, &olen ) ) != 0 )
ret = POLARSSL_ERR_PKCS5_PASSWORD_MISMATCH;
}
exit:
md_free_ctx( &md_ctx );

4
programs/aes/crypt_and_hash.c
View File

@ -343,7 +343,7 @@ int main( int argc, char *argv[] )
}
}
if( cipher_finish( &cipher_ctx, output, &olen, NULL, 0 ) != 0 )
if( cipher_finish( &cipher_ctx, output, &olen ) != 0 )
{
fprintf( stderr, "cipher_finish() returned error\n" );
goto exit;
@ -461,7 +461,7 @@ int main( int argc, char *argv[] )
/*
* Write the final block of data
*/
cipher_finish( &cipher_ctx, output, &olen, NULL, 0 );
cipher_finish( &cipher_ctx, output, &olen );
if( fwrite( output, 1, olen, fout ) != olen )
{

20
tests/suites/test_suite_cipher.function
View File

@ -76,10 +76,11 @@ void enc_dec_buf( int cipher_id, char *cipher_string, int key_len,
total_len < length &&
total_len + cipher_get_block_size( &ctx_enc ) > length ) );
TEST_ASSERT( 0 == cipher_finish( &ctx_enc, encbuf + outlen, &outlen,
tag, 16 ) );
TEST_ASSERT( 0 == cipher_finish( &ctx_enc, encbuf + outlen, &outlen ) );
total_len += outlen;
TEST_ASSERT( 0 == cipher_write_tag( &ctx_enc, tag, 16 ) );
TEST_ASSERT( total_len == length ||
( total_len % cipher_get_block_size( &ctx_enc ) == 0 &&
total_len > length &&
@ -94,10 +95,11 @@ void enc_dec_buf( int cipher_id, char *cipher_string, int key_len,
total_len < length &&
total_len + cipher_get_block_size( &ctx_dec ) >= length ) );
TEST_ASSERT( 0 == cipher_finish( &ctx_dec, decbuf + outlen, &outlen,
tag, 16 ) );
TEST_ASSERT( 0 == cipher_finish( &ctx_dec, decbuf + outlen, &outlen ) );
total_len += outlen;
TEST_ASSERT( 0 == cipher_check_tag( &ctx_dec, tag, 16 ) );
TEST_ASSERT( total_len == length );
TEST_ASSERT( 0 == memcmp(inbuf, decbuf, length) );
@ -145,7 +147,7 @@ void enc_fail( int cipher_id, int pad_mode, int key_len,
/* encode length number of bytes from inbuf */
TEST_ASSERT( 0 == cipher_update( &ctx, inbuf, length, encbuf, &outlen ) );
TEST_ASSERT( ret == cipher_finish( &ctx, encbuf + outlen, &outlen, NULL, 0 ) );
TEST_ASSERT( ret == cipher_finish( &ctx, encbuf + outlen, &outlen ) );
/* done */
TEST_ASSERT( 0 == cipher_free_ctx( &ctx ) );
@ -192,7 +194,7 @@ void dec_empty_buf()
TEST_ASSERT( 0 == cipher_update( &ctx_dec, encbuf, 0, decbuf, &outlen ) );
TEST_ASSERT( 0 == outlen );
TEST_ASSERT( POLARSSL_ERR_CIPHER_FULL_BLOCK_EXPECTED == cipher_finish(
&ctx_dec, decbuf + outlen, &outlen, NULL, 0 ) );
&ctx_dec, decbuf + outlen, &outlen ) );
TEST_ASSERT( 0 == outlen );
TEST_ASSERT( 0 == cipher_free_ctx( &ctx_dec ) );
@ -259,8 +261,7 @@ void enc_dec_buf_multipart( int cipher_id, int key_len, int first_length_val,
totaloutlen < length &&
totaloutlen + cipher_get_block_size( &ctx_enc ) > length ) );
TEST_ASSERT( 0 == cipher_finish( &ctx_enc, encbuf + totaloutlen, &outlen,
NULL, 0 ) );
TEST_ASSERT( 0 == cipher_finish( &ctx_enc, encbuf + totaloutlen, &outlen ) );
totaloutlen += outlen;
TEST_ASSERT( totaloutlen == length ||
( totaloutlen % cipher_get_block_size( &ctx_enc ) == 0 &&
@ -276,8 +277,7 @@ void enc_dec_buf_multipart( int cipher_id, int key_len, int first_length_val,
totaloutlen < length &&
totaloutlen + cipher_get_block_size( &ctx_dec ) >= length ) );
TEST_ASSERT( 0 == cipher_finish( &ctx_dec, decbuf + outlen, &outlen,
NULL, 0 ) );
TEST_ASSERT( 0 == cipher_finish( &ctx_dec, decbuf + outlen, &outlen ) );
totaloutlen += outlen;
TEST_ASSERT( totaloutlen == length );