From aed606579340a277fb1cc6a4e81f0ee769daa6ce Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Manuel=20P=C3=A9gouri=C3=A9-Gonnard?= Date: Wed, 7 May 2014 13:14:42 +0200 Subject: [PATCH] CCM source cosmetics/tune-ups - source a bit shorter - generated code slightly smaller - preserving performance --- library/ccm.c | 145 ++++++++++++++++++++------------------------------ 1 file changed, 58 insertions(+), 87 deletions(-) diff --git a/library/ccm.c b/library/ccm.c index fafa23869..98987b2fb 100644 --- a/library/ccm.c +++ b/library/ccm.c @@ -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 ); \ - } \ - \ - for( i = 0; i < 16; i++ ) \ - dst[i] ^= src[i]; \ -} +/* + * 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++ ) \ + 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 ); }