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Fix issues in CMAC in repeated updates

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Successive calls to mbedtls_cipher_cmac_update() which weren't block aligned
were failing, which is fixed by this commit.
This commit is contained in:
Simon Butcher 2016-10-10 21:37:42 +01:00 committed by Janos Follath
parent b98eaff408
commit 6b0774ab1a
1 changed files with 9 additions and 8 deletions
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17
library/cmac.c
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@ -256,8 +256,8 @@ int mbedtls_cipher_cmac_update( mbedtls_cipher_context_t *ctx,
block_size = ctx->cipher_info->block_size; block_size = ctx->cipher_info->block_size;
state = ctx->cmac_ctx->state; state = ctx->cmac_ctx->state;
/* Is their data still to process from the last call, that's equal to /* Is there data still to process from the last call, that's greater in
* or greater than a block? */ * size than a block? */
if( cmac_ctx->unprocessed_len > 0 && if( cmac_ctx->unprocessed_len > 0 &&
ilen > block_size - cmac_ctx->unprocessed_len ) ilen > block_size - cmac_ctx->unprocessed_len )
{ {
@ -273,9 +273,8 @@ int mbedtls_cipher_cmac_update( mbedtls_cipher_context_t *ctx,
goto exit; goto exit;
} }
ilen -= block_size; input += block_size - cmac_ctx->unprocessed_len;
input += cmac_ctx->unprocessed_len; ilen -= block_size - cmac_ctx->unprocessed_len;
cmac_ctx->unprocessed_len = 0; cmac_ctx->unprocessed_len = 0;
} }
@ -300,8 +299,10 @@ int mbedtls_cipher_cmac_update( mbedtls_cipher_context_t *ctx,
/* If there is data left over that wasn't aligned to a block */ /* If there is data left over that wasn't aligned to a block */
if( ilen > 0 ) if( ilen > 0 )
{ {
memcpy( &cmac_ctx->unprocessed_block, input, ilen ); memcpy( &cmac_ctx->unprocessed_block[cmac_ctx->unprocessed_len],
cmac_ctx->unprocessed_len = ilen; input,
ilen );
cmac_ctx->unprocessed_len += ilen;
if( ilen % block_size > 0 ) if( ilen % block_size > 0 )
cmac_ctx->padding_flag = 1; cmac_ctx->padding_flag = 1;
@ -339,7 +340,7 @@ int mbedtls_cipher_cmac_finish( mbedtls_cipher_context_t *ctx,
last_block = cmac_ctx->unprocessed_block; last_block = cmac_ctx->unprocessed_block;
/* Calculate last block */ /* Calculate last block */
if( cmac_ctx->padding_flag ) if( cmac_ctx->padding_flag && cmac_ctx->unprocessed_len < block_size )
{ {
cmac_pad( M_last, block_size, last_block, cmac_ctx->unprocessed_len ); cmac_pad( M_last, block_size, last_block, cmac_ctx->unprocessed_len );
cmac_xor_block( M_last, M_last, K2, block_size ); cmac_xor_block( M_last, M_last, K2, block_size );