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Split ccm_auth function.

Browse Source 
Move logic to ccm_starts, ccm_set_lengths, ccm_update_ad,
ccm_update and ccm_finish
Use separate variable to track context state.
Encode first block only if both mbedtls_ccm_starts() and
mbedtls_ccm_set_lengths() were called.

Signed-off-by: Mateusz Starzyk <mateusz.starzyk@mobica.com>
This commit is contained in:
Mateusz Starzyk 2021-06-22 20:34:20 +02:00
parent 89d469cdb4
commit 793692cbcb
2 changed files with 178 additions and 50 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/mbedtls/ccm.h
View File

@ -87,6 +87,9 @@ typedef struct mbedtls_ccm_context
#MBEDTLS_CCM_DECRYPT or
#MBEDTLS_CCM_STAR_ENCRYPT or
#MBEDTLS_CCM_STAR_DECRYPT. */
int MBEDTLS_PRIVATE(state); /*!< Working value holding context's
state. Used for chunked data
input */
}
mbedtls_ccm_context;

225
library/ccm.c
View File

@ -142,22 +142,105 @@ void mbedtls_ccm_free( mbedtls_ccm_context *ctx )
(dst)[i] = (src)[i] ^ ctx->b[i]; \
} while( 0 )
/*
* Authenticated encryption or decryption
*/
static int ccm_auth_crypt( mbedtls_ccm_context *ctx, int mode, size_t length,
const unsigned char *iv, size_t iv_len,
const unsigned char *add, size_t add_len,
const unsigned char *input, unsigned char *output,
unsigned char *tag, size_t tag_len )
#define CCM_STATE__CLEAR 0
#define CCM_STATE__STARTED 0x0001
#define CCM_STATE__LENGHTS_SET 0x0002
static void mbedtls_ccm_clear_state(mbedtls_ccm_context *ctx) {
ctx->state = CCM_STATE__CLEAR;
memset( ctx->b, 0, 16);
memset( ctx->y, 0, 16);
memset( ctx->ctr, 0, 16);
}
static int mbedtls_ccm_calculate_first_block(mbedtls_ccm_context *ctx)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char i;
size_t len_left, olen;
const unsigned char *src;
unsigned char *dst;
/* length calulcation can be done only after both
* mbedtls_ccm_starts() and mbedtls_ccm_set_lengths() have been executed
*/
if( !(ctx->state & CCM_STATE__STARTED) || !(ctx->state & CCM_STATE__LENGHTS_SET) )
return 0;
/*
* First block B_0:
* 0 .. 0 flags - set by: mbedtls_ccm_starts() and mbedtls_ccm_set_lenghts()
* 1 .. iv_len nonce (aka iv) - set by: mbedtls_ccm_starts()
* iv_len+1 .. 15 length - set by: mbedtls_ccm_calculate_first_block()
*/
for( i = 0, len_left = ctx->plaintext_len; i < ctx->q; i++, len_left >>= 8 )
ctx->b[15-i] = (unsigned char)( len_left & 0xFF );
if( len_left > 0 )
return( MBEDTLS_ERR_CCM_BAD_INPUT );
/* Start CBC-MAC with first block*/
UPDATE_CBC_MAC;
return (0);
}
int mbedtls_ccm_starts( mbedtls_ccm_context *ctx,
int mode,
const unsigned char *iv,
size_t iv_len )
{
int ret;
/* Also implies q is within bounds */
if( iv_len < 7 || iv_len > 13 )
return( MBEDTLS_ERR_CCM_BAD_INPUT );
ctx->mode = mode;
ctx->q = 16 - 1 - (unsigned char) iv_len;
/*
* Prepare counter block for encryption:
* 0 .. 0 flags
* 1 .. iv_len nonce (aka iv)
* iv_len+1 .. 15 counter (initially 1)
*
* With flags as (bits):
* 7 .. 3 0
* 2 .. 0 q - 1
*/
memset( ctx->ctr, 0, 16);
ctx->ctr[0] = ctx->q - 1;
memcpy( ctx->ctr + 1, iv, iv_len );
memset( ctx->ctr + 1 + iv_len, 0, ctx->q );
ctx->ctr[15] = 1;
/*
* First block B_0:
* 0 .. 0 flags - set by: mbedtls_ccm_starts() and mbedtls_ccm_set_lenghts()
* 1 .. iv_len nonce (aka iv) - set by: mbedtls_ccm_starts()
* iv_len+1 .. 15 length - set by: mbedtls_ccm_calculate_first_block()
*
* With flags as (bits):
* 7 0
* 6 add present? - set by: mbedtls_ccm_set_lengths()
* 5 .. 3 (t - 2) / 2 - set by: mbedtls_ccm_set_lengths()
* 2 .. 0 q - 1 - set by: mbedtls_ccm_starts()
*/
ctx->b[0] |= ctx->q - 1;
memcpy( ctx->b + 1, iv, iv_len );
ctx->state |= CCM_STATE__STARTED;
ret = mbedtls_ccm_calculate_first_block(ctx);
return ret;
}
int mbedtls_ccm_set_lengths( mbedtls_ccm_context *ctx,
size_t total_ad_len,
size_t plaintext_len,
size_t tag_len )
{
int ret;
/*
* Check length requirements: SP800-38C A.1
@ -169,44 +252,40 @@ static int ccm_auth_crypt( mbedtls_ccm_context *ctx, int mode, size_t length,
if( tag_len == 2 || tag_len > 16 || tag_len % 2 != 0 )
return( MBEDTLS_ERR_CCM_BAD_INPUT );
/* Also implies q is within bounds */
if( iv_len < 7 || iv_len > 13 )
if( total_ad_len >= 0xFF00 )
return( MBEDTLS_ERR_CCM_BAD_INPUT );
if( add_len >= 0xFF00 )
return( MBEDTLS_ERR_CCM_BAD_INPUT );
ctx->q = 16 - 1 - (unsigned char) iv_len;
/*
* First block B_0:
* 0 .. 0 flags
* 1 .. iv_len nonce (aka iv)
* iv_len+1 .. 15 length
* 0 .. 0 flags - set by: mbedtls_ccm_starts() and mbedtls_ccm_set_lenghts()
* 1 .. iv_len nonce (aka iv) - set by: mbedtls_ccm_starts()
* iv_len+1 .. 15 length - set by: mbedtls_ccm_calculate_first_block()
*
* With flags as (bits):
* 7 0
* 6 add present?
* 5 .. 3 (t - 2) / 2
* 2 .. 0 q - 1
* 6 add present? - set by: mbedtls_ccm_set_lengths()
* 5 .. 3 (t - 2) / 2 - set by: mbedtls_ccm_set_lengths()
* 2 .. 0 q - 1 - set by: mbedtls_ccm_starts()
*/
ctx->b[0] = 0;
ctx->b[0] |= ( add_len > 0 ) << 6;
ctx->b[0] |= ( total_ad_len > 0 ) << 6;
ctx->b[0] |= ( ( tag_len - 2 ) / 2 ) << 3;
ctx->b[0] |= ctx->q - 1;
memcpy( ctx->b + 1, iv, iv_len );
ctx->plaintext_len = plaintext_len;
for( i = 0, len_left = length; i < ctx->q; i++, len_left >>= 8 )
ctx->b[15-i] = (unsigned char)( len_left & 0xFF );
ctx->state |= CCM_STATE__LENGHTS_SET;
ret = mbedtls_ccm_calculate_first_block(ctx);
if( len_left > 0 )
return( MBEDTLS_ERR_CCM_BAD_INPUT );
return ret;
}
/* Start CBC-MAC with first block */
memset( ctx->y, 0, 16 );
UPDATE_CBC_MAC;
int mbedtls_ccm_update_ad( mbedtls_ccm_context *ctx,
const unsigned char *add,
size_t add_len )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char i;
size_t len_left, olen;
const unsigned char *src;
/*
* If there is additional data, update CBC-MAC with
@ -242,20 +321,24 @@ static int ccm_auth_crypt( mbedtls_ccm_context *ctx, int mode, size_t length,
}
}
/*
* Prepare counter block for encryption:
* 0 .. 0 flags
* 1 .. iv_len nonce (aka iv)
* iv_len+1 .. 15 counter (initially 1)
*
* With flags as (bits):
* 7 .. 3 0
* 2 .. 0 q - 1
*/
ctx->ctr[0] = ctx->q - 1;
memcpy( ctx->ctr + 1, iv, iv_len );
memset( ctx->ctr + 1 + iv_len, 0, ctx->q );
ctx->ctr[15] = 1;
return (0);
}
int mbedtls_ccm_update( mbedtls_ccm_context *ctx,
const unsigned char *input, size_t input_len,
unsigned char *output, size_t output_size,
size_t *output_len )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char i;
size_t len_left, olen;
const unsigned char *src;
unsigned char *dst;
if( output_size < input_len )
return( MBEDTLS_ERR_CCM_BAD_INPUT );
CCM_VALIDATE_RET( output_length != NULL );
*output_len = input_len;
/*
* Authenticate and {en,de}crypt the message.
@ -263,7 +346,7 @@ static int ccm_auth_crypt( mbedtls_ccm_context *ctx, int mode, size_t length,
* The only difference between encryption and decryption is
* the respective order of authentication and {en,de}cryption.
*/
len_left = length;
len_left = input_len;
src = input;
dst = output;
@ -300,6 +383,16 @@ static int ccm_auth_crypt( mbedtls_ccm_context *ctx, int mode, size_t length,
break;
}
return (0);
}
int mbedtls_ccm_finish( mbedtls_ccm_context *ctx,
unsigned char *tag, size_t tag_len )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char i;
size_t olen;
/*
* Authentication: reset counter and crypt/mask internal tag
*/
@ -308,6 +401,38 @@ static int ccm_auth_crypt( mbedtls_ccm_context *ctx, int mode, size_t length,
CTR_CRYPT( ctx->y, ctx->y, 16 );
memcpy( tag, ctx->y, tag_len );
mbedtls_ccm_clear_state(ctx);
return( 0 );
}
/*
* Authenticated encryption or decryption
*/
static int ccm_auth_crypt( mbedtls_ccm_context *ctx, int mode, size_t length,
const unsigned char *iv, size_t iv_len,
const unsigned char *add, size_t add_len,
const unsigned char *input, unsigned char *output,
unsigned char *tag, size_t tag_len )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t olen;
if( ( ret = mbedtls_ccm_starts( ctx, mode, iv, iv_len ) ) != 0 )
return( ret );
if( ( ret = mbedtls_ccm_set_lengths( ctx, add_len, length, tag_len ) ) != 0 )
return( ret );
if( ( ret = mbedtls_ccm_update_ad( ctx, add, add_len ) ) != 0 )
return( ret );
if( ( ret = mbedtls_ccm_update( ctx, input, length,
output, length, &olen ) ) != 0 )
return( ret );
if( ( ret = mbedtls_ccm_finish( ctx, tag, tag_len ) ) != 0 )
return( ret );
return( 0 );
}