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Do not use output buffer for internal XOR during decryption.

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Signed-off-by: Mateusz Starzyk <mateusz.starzyk@mobica.com>
This commit is contained in:
Mateusz Starzyk 2021-07-28 15:08:47 +02:00
parent 36d3b89c84
commit 22f7a35ca4
2 changed files with 47 additions and 11 deletions
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2
include/mbedtls/ccm.h
View File

@ -61,6 +61,8 @@
#define MBEDTLS_ERR_CCM_BAD_INPUT -0x000D
/** Authenticated decryption failed. */
#define MBEDTLS_ERR_CCM_AUTH_FAILED -0x000F
/** Memory allocation failed */
#define MBEDTLS_ERR_CCM_ALLOC_FAILED -0x0011
#ifdef __cplusplus
extern "C" {

56
library/ccm.c
View File

@ -36,14 +36,17 @@
#include <string.h>
#if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C)
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C)
#include <stdio.h>
#define mbedtls_printf printf
#endif /* MBEDTLS_PLATFORM_C */
#endif /* MBEDTLS_SELF_TEST && MBEDTLS_AES_C */
#include <stdlib.h>
#define mbedtls_calloc calloc
#define mbedtls_free free
#endif /* MBEDTLS_PLATFORM_C */
#if !defined(MBEDTLS_CCM_ALT)
@ -330,13 +333,16 @@ int mbedtls_ccm_update( mbedtls_ccm_context *ctx,
unsigned char *output, size_t output_size,
size_t *output_len )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
int ret;
unsigned char i;
size_t use_len, offset, olen;
const size_t local_output_len = input_len;
unsigned char* local_output = NULL;
if( ctx->state & CCM_STATE__ERROR )
{
return ret;
return MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
}
if( ctx->processed + input_len > ctx->plaintext_len )
@ -344,10 +350,24 @@ int mbedtls_ccm_update( mbedtls_ccm_context *ctx,
return MBEDTLS_ERR_CCM_BAD_INPUT;
}
/* Local output is used for decryption only. */
if( ctx->mode == MBEDTLS_CCM_DECRYPT || \
ctx->mode == MBEDTLS_CCM_STAR_DECRYPT )
{
local_output = mbedtls_calloc( local_output_len, sizeof( *local_output) );
if( local_output == NULL )
{
ctx->state |= CCM_STATE__ERROR;
return MBEDTLS_ERR_CCM_ALLOC_FAILED;
}
}
if( output_size < input_len )
return( MBEDTLS_ERR_CCM_BAD_INPUT );
*output_len = input_len;
ret = 0;
while ( input_len > 0 )
{
offset = ctx->processed % 16;
@ -370,31 +390,37 @@ int mbedtls_ccm_update( mbedtls_ccm_context *ctx,
if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, ctx->y, 16, ctx->y, &olen ) ) != 0 )
{
ctx->state |= CCM_STATE__ERROR;
return( ret );
goto exit;
}
}
ret = mbedtls_ccm_crypt( ctx, offset, use_len, input, output );
if( ret != 0 )
return ret;
goto exit;
}
if( ctx->mode == MBEDTLS_CCM_DECRYPT || \
ctx->mode == MBEDTLS_CCM_STAR_DECRYPT )
{
ret = mbedtls_ccm_crypt( ctx, offset, use_len, input, output );
/* Write decrypted data to local_output to avoid using output variable as
* input in the XOR operation for Y.
*/
ret = mbedtls_ccm_crypt( ctx, offset, use_len, input, local_output );
if( ret != 0 )
return ret;
goto exit;
for( i = 0; i < use_len; i++ )
ctx->y[i + offset] ^= output[i];
ctx->y[i + offset] ^= local_output[i];
memcpy( output, local_output, use_len );
mbedtls_platform_zeroize( local_output, local_output_len );
if( use_len + offset == 16 || ctx->processed == ctx->plaintext_len )
{
if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, ctx->y, 16, ctx->y, &olen ) ) != 0 )
{
ctx->state |= CCM_STATE__ERROR;
return( ret );
goto exit;
}
}
}
@ -411,7 +437,15 @@ int mbedtls_ccm_update( mbedtls_ccm_context *ctx,
output += use_len;
}
return 0;
exit:
if( ctx->mode == MBEDTLS_CCM_DECRYPT || \
ctx->mode == MBEDTLS_CCM_STAR_DECRYPT )
{
mbedtls_platform_zeroize( local_output, local_output_len );
mbedtls_free( local_output );
}
return ret;
}
int mbedtls_ccm_finish( mbedtls_ccm_context *ctx,