cmac: more cosmetic changes
diff --git a/include/mbedtls/cmac.h b/include/mbedtls/cmac.h
index 3b5c13e..c2ae83b 100644
--- a/include/mbedtls/cmac.h
+++ b/include/mbedtls/cmac.h
@@ -108,6 +108,7 @@
/**
* \brief AES-CMAC-128-PRF
+ * TODO: add reference to the standard
*
* \param ctx CMAC context
* \param key PRF key
@@ -115,6 +116,7 @@
* \param input buffer holding the input data
* \param in_len length of the input data in bytes
* \param tag buffer holding the tag to verify (16 bytes)
+ * TODO: update description of tag
*
* \return 0 if successful
*/
diff --git a/library/cmac.c b/library/cmac.c
index ff7cb21..23b8044 100644
--- a/library/cmac.c
+++ b/library/cmac.c
@@ -69,7 +69,8 @@
*
* Input and output MUST not point to the same buffer
*/
-static void multiply_by_u( unsigned char *output, const unsigned char *input )
+static void cmac_multiply_by_u( unsigned char *output,
+ const unsigned char *input )
{
const unsigned char Rb = 0x87; /* block size 16 only */
unsigned char mask;
@@ -101,7 +102,7 @@
/*
* Generate subkeys
*/
-static int generate_subkeys( mbedtls_cmac_context *ctx )
+static int cmac_generate_subkeys( mbedtls_cmac_context *ctx )
{
int ret;
unsigned char L[16];
@@ -118,14 +119,17 @@
/*
* Generate K1 and K2
*/
- multiply_by_u( ctx->K1, L );
- multiply_by_u( ctx->K2, ctx->K1 );
+ cmac_multiply_by_u( ctx->K1, L );
+ cmac_multiply_by_u( ctx->K2, ctx->K1 );
mbedtls_zeroize( L, sizeof( L ) );
return( 0 );
}
+/*
+ * Set key and prepare context for use
+ */
int mbedtls_cmac_setkey( mbedtls_cmac_context *ctx,
mbedtls_cipher_id_t cipher,
const unsigned char *key,
@@ -153,7 +157,7 @@
return( ret );
}
- return( generate_subkeys( ctx ) );
+ return( cmac_generate_subkeys( ctx ) );
}
/*
@@ -171,9 +175,9 @@
* We can't use the padding option from the cipher layer, as it only works for
* CBC and we use ECB mode, and anyway we need to XOR K1 or K2 in addition.
*/
-static void padding( unsigned char padded_block[16],
- const unsigned char *last_block,
- size_t length )
+static void cmac_pad( unsigned char padded_block[16],
+ const unsigned char *last_block,
+ size_t length )
{
size_t j;
@@ -237,7 +241,7 @@
/* Calculate last block */
if( needs_padding )
{
- padding( M_last, input + 16 * ( n - 1 ), in_len % 16 );
+ cmac_pad( M_last, input + 16 * ( n - 1 ), in_len % 16 );
XOR_128( M_last, M_last, ctx->K2 );
}
else
@@ -262,7 +266,7 @@
#undef UPDATE_CMAC
/*
- * Authenticated decryption
+ * Verify tag on complete message
*/
int mbedtls_cmac_verify( mbedtls_cmac_context *ctx,
const unsigned char *input, size_t in_len,
@@ -281,18 +285,19 @@
/* Check tag in "constant-time" */
for( diff = 0, i = 0; i < tag_len; i++ )
- {
diff |= tag[i] ^ check_tag[i];
- }
if( diff != 0 )
- {
return( MBEDTLS_ERR_CMAC_VERIFY_FAILED );
- }
return( 0 );
}
+/*
+ * PRF based on CMAC with AES-128
+ * TODO: add reference to the standard
+ * TODO: do we need to take a cmac_context as an argument here?
+ */
int mbedtls_aes_cmac_prf_128( mbedtls_cmac_context *ctx,
const unsigned char *key, size_t key_length,
const unsigned char *input, size_t in_len,
@@ -317,22 +322,17 @@
ret = mbedtls_cmac_setkey( &zero_ctx, MBEDTLS_CIPHER_ID_AES,
zero_key, 8 * sizeof zero_key );
if( ret != 0 )
- {
return( ret );
- }
+
ret = mbedtls_cmac_generate( &zero_ctx, key, key_length, int_key, 16 );
if( ret != 0 )
- {
return( ret );
- }
}
ret = mbedtls_cmac_setkey( ctx, MBEDTLS_CIPHER_ID_AES,
int_key, 8 * sizeof int_key );
if( ret != 0 )
- {
return( ret );
- }
mbedtls_zeroize( int_key, sizeof( int_key ) );
@@ -341,7 +341,7 @@
#if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C)
/*
- * Examples 1 to 4 from SP800-3B corrected Appendix D.1
+ * Examples 1 to 4 from SP800-38B corrected Appendix D.1
* http://csrc.nist.gov/publications/nistpubs/800-38B/Updated_CMAC_Examples.pdf
*/
@@ -456,7 +456,7 @@
if( mbedtls_cmac_setkey( &ctx, MBEDTLS_CIPHER_ID_AES, key, 8 * sizeof key ) != 0 )
{
if( verbose != 0 )
- mbedtls_printf( " CMAC: setup failed" );
+ mbedtls_printf( " CMAC: setup failed\n" );
return( 1 );
}
@@ -465,7 +465,7 @@
( memcmp( ctx.K2, K2, 16 ) != 0 ) )
{
if( verbose != 0 )
- mbedtls_printf( " CMAC: subkey generation failed" );
+ mbedtls_printf( " CMAC: subkey generation failed\n" );
return( 1 );
}