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CCM source cosmetics/tune-ups

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- source a bit shorter
- generated code slightly smaller
- preserving performance
This commit is contained in:
Manuel Pégourié-Gonnard 2014-05-07 13:14:42 +02:00
parent 58d78a8d70
commit aed6065793
1 changed files with 58 additions and 87 deletions
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143
library/ccm.c
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@ -84,33 +84,33 @@ void ccm_free( ccm_context *ctx )
memset( ctx, 0, sizeof( ccm_context ) );
}
#define UPDATE_CBC_MAC( src ) \
{ \
size_t olen; \
\
for( i = 0; i < 16; i++ ) \
src[i] ^= y[i]; \
\
if( ( ret = cipher_update( &ctx->cipher_ctx, src, 16, \
y, &olen ) ) != 0 ) \
{ \
return( ret ); \
} \
}
/*
* Macros for common operations.
* Results in smaller compiled code than static inline functions.
*/
#define CTR_CRYPT_BLOCK( dst, src ) \
{ \
size_t olen; \
\
if( ( ret = cipher_update( &ctx->cipher_ctx, ctr, 16, \
dst, &olen ) ) != 0 ) \
{ \
return( ret ); \
} \
\
/*
* Update the CBC-MAC state in y using a block in b
* (Always using b as the source helps the compiler optimise a bit better.)
*/
#define UPDATE_CBC_MAC \
for( i = 0; i < 16; i++ ) \
dst[i] ^= src[i]; \
}
y[i] ^= b[i]; \
\
if( ( ret = cipher_update( &ctx->cipher_ctx, y, 16, y, &olen ) ) != 0 ) \
return( ret );
/*
* Encrypt or decrypt a partial block with CTR
* Warning: using b for temporary storage! src and dst must not be b!
* (This avoids allocating one more 16 bytes buffer.)
*/
#define CTR_CRYPT( dst, src, len ) \
if( ( ret = cipher_update( &ctx->cipher_ctx, ctr, 16, b, &olen ) ) != 0 ) \
return( ret ); \
\
for( i = 0; i < len; i++ ) \
dst[i] = src[i] ^ b[i];
/*
* Authenticated encryption or decryption
@ -124,7 +124,7 @@ static int ccm_auth_crypt( ccm_context *ctx, int mode, size_t length,
int ret;
unsigned char i;
unsigned char q = 16 - 1 - iv_len;
size_t len_left;
size_t len_left, olen;
unsigned char b[16];
unsigned char y[16];
unsigned char ctr[16];
@ -174,7 +174,7 @@ static int ccm_auth_crypt( ccm_context *ctx, int mode, size_t length,
/* Start CBC-MAC with first block */
memset( y, 0, 16 );
UPDATE_CBC_MAC( b );
UPDATE_CBC_MAC;
/*
* If there is additional data, update CBC-MAC with
@ -195,28 +195,23 @@ static int ccm_auth_crypt( ccm_context *ctx, int mode, size_t length,
len_left -= use_len;
src += use_len;
UPDATE_CBC_MAC( b );
UPDATE_CBC_MAC;
while( len_left > 16 )
while( len_left > 0 )
{
memcpy( b, src, 16 );
UPDATE_CBC_MAC( b );
use_len = len_left > 16 ? 16 : len_left;
len_left -= 16;
src += 16;
}
if( len_left > 0 )
{
memset( b, 0, 16 );
memcpy( b, src, len_left );
memcpy( b, src, use_len );
UPDATE_CBC_MAC;
UPDATE_CBC_MAC( b );
len_left -= use_len;
src += use_len;
}
}
/*
* Counter block:
* Prepare counter block for encryption:
* 0 .. 0 flags
* 1 .. iv_len nonce (aka iv)
* iv_len+1 .. 15 counter (initially 1)
@ -230,34 +225,39 @@ static int ccm_auth_crypt( ccm_context *ctx, int mode, size_t length,
memset( ctr + 1 + iv_len, 0, q );
ctr[15] = 1;
/*
* Authenticate and {en,de}crypt the message.
*
* The only difference between encryption and decryption is
* the respective order of authentication and {en,de}cryption.
*/
len_left = length;
src = input;
dst = output;
/*
* Authenticate and crypt message
* The only difference between encryption and decryption is
* the respective order of authentication and {en,de}cryption
*/
while( len_left > 16 )
while( len_left > 0 )
{
unsigned char use_len = len_left > 16 ? 16 : len_left;
if( mode == CCM_ENCRYPT )
{
memcpy( b, src, 16 );
UPDATE_CBC_MAC( b );
memset( b, 0, 16 );
memcpy( b, src, use_len );
UPDATE_CBC_MAC;
}
CTR_CRYPT_BLOCK( dst, src );
CTR_CRYPT( dst, src, use_len );
if( mode == CCM_DECRYPT )
{
memcpy( b, dst, 16 );
UPDATE_CBC_MAC( b );
memset( b, 0, 16 );
memcpy( b, dst, use_len );
UPDATE_CBC_MAC;
}
dst += 16;
src += 16;
len_left -= 16;
dst += use_len;
src += use_len;
len_left -= use_len;
/*
* Increment counter.
@ -268,43 +268,14 @@ static int ccm_auth_crypt( ccm_context *ctx, int mode, size_t length,
break;
}
if( len_left > 0 )
{
unsigned char mask[16];
size_t olen;
if( mode == CCM_ENCRYPT )
{
memset( b, 0, 16 );
memcpy( b, src, len_left );
UPDATE_CBC_MAC( b );
}
if( ( ret = cipher_update( &ctx->cipher_ctx, ctr, 16,
mask, &olen ) ) != 0 )
{
return( ret );
}
for( i = 0; i < len_left; i++ )
dst[i] = src[i] ^ mask[i];
if( mode == CCM_DECRYPT )
{
memset( b, 0, 16 );
memcpy( b, dst, len_left );
UPDATE_CBC_MAC( b );
}
}
/*
* Authentication: reset counter and {en,de}crypt internal tag
* Authentication: reset counter and crypt/mask internal tag
*/
for( i = 0; i < q; i++ )
ctr[15-i] = 0;
CTR_CRYPT_BLOCK( b, y );
memcpy( tag, b, tag_len );
CTR_CRYPT( y, y, 16 );
memcpy( tag, y, tag_len );
return( 0 );
}