1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis 2 * 3 * LibTomCrypt is a library that provides various cryptographic 4 * algorithms in a highly modular and flexible manner. 5 * 6 * The library is free for all purposes without any express 7 * guarantee it works. 8 * 9 * Tom St Denis, tomstdenis (at) gmail.com, http://libtomcrypt.com 10 */ 11 #include "tomcrypt.h" 12 13 /** 14 @file omac_done.c 15 OMAC1 support, terminate a stream, Tom St Denis 16 */ 17 18 #ifdef LTC_OMAC 19 20 /** 21 Terminate an OMAC stream 22 @param omac The OMAC state 23 @param out [out] Destination for the authentication tag 24 @param outlen [in/out] The max size and resulting size of the authentication tag 25 @return CRYPT_OK if successful 26 */ 27 int omac_done(omac_state *omac, unsigned char *out, unsigned long *outlen) 28 { 29 int err, mode; 30 unsigned x; 31 32 LTC_ARGCHK(omac != NULL); 33 LTC_ARGCHK(out != NULL); 34 LTC_ARGCHK(outlen != NULL); 35 if ((err = cipher_is_valid(omac->cipher_idx)) != CRYPT_OK) { 36 return err; 37 } 38 39 if ((omac->buflen > (int)sizeof(omac->block)) || (omac->buflen < 0) || 40 (omac->blklen > (int)sizeof(omac->block)) || (omac->buflen > omac->blklen)) { 41 return CRYPT_INVALID_ARG; 42 } 43 44 /* figure out mode */ 45 if (omac->buflen != omac->blklen) { 46 /* add the 0x80 byte */ 47 omac->block[omac->buflen++] = 0x80; 48 49 /* pad with 0x00 */ 50 while (omac->buflen < omac->blklen) { 51 omac->block[omac->buflen++] = 0x00; 52 } 53 mode = 1; 54 } else { 55 mode = 0; 56 } 57 58 /* now xor prev + Lu[mode] */ 59 for (x = 0; x < (unsigned)omac->blklen; x++) { 60 omac->block[x] ^= omac->prev[x] ^ omac->Lu[mode][x]; 61 } 62 63 /* encrypt it */ 64 if ((err = cipher_descriptor[omac->cipher_idx].ecb_encrypt(omac->block, omac->block, &omac->key)) != CRYPT_OK) { 65 return err; 66 } 67 cipher_descriptor[omac->cipher_idx].done(&omac->key); 68 69 /* output it */ 70 for (x = 0; x < (unsigned)omac->blklen && x < *outlen; x++) { 71 out[x] = omac->block[x]; 72 } 73 *outlen = x; 74 75 #ifdef LTC_CLEAN_STACK 76 zeromem(omac, sizeof(*omac)); 77 #endif 78 return CRYPT_OK; 79 } 80 81 #endif 82 83 84 /* $Source: /cvs/libtom/libtomcrypt/src/mac/omac/omac_done.c,v $ */ 85 /* $Revision: 1.7 $ */ 86 /* $Date: 2006/11/03 00:39:49 $ */ 87
