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 12 /** 13 @file ocb_done_decrypt.c 14 OCB implementation, terminate decryption, by Tom St Denis 15 */ 16 #include "tomcrypt.h" 17 18 #ifdef OCB_MODE 19 20 /** 21 Terminate a decrypting OCB state 22 @param ocb The OCB state 23 @param ct The ciphertext (if any) 24 @param ctlen The length of the ciphertext (octets) 25 @param pt [out] The plaintext 26 @param tag The authentication tag (to compare against) 27 @param taglen The length of the authentication tag provided 28 @param stat [out] The result of the tag comparison 29 @return CRYPT_OK if the process was successful regardless if the tag is valid 30 */ 31 int ocb_done_decrypt(ocb_state *ocb, 32 const unsigned char *ct, unsigned long ctlen, 33 unsigned char *pt, 34 const unsigned char *tag, unsigned long taglen, int *stat) 35 { 36 int err; 37 unsigned char *tagbuf; 38 unsigned long tagbuflen; 39 40 LTC_ARGCHK(ocb != NULL); 41 LTC_ARGCHK(pt != NULL); 42 LTC_ARGCHK(ct != NULL); 43 LTC_ARGCHK(tag != NULL); 44 LTC_ARGCHK(stat != NULL); 45 46 /* default to failed */ 47 *stat = 0; 48 49 /* allocate memory */ 50 tagbuf = XMALLOC(MAXBLOCKSIZE); 51 if (tagbuf == NULL) { 52 return CRYPT_MEM; 53 } 54 55 tagbuflen = MAXBLOCKSIZE; 56 if ((err = s_ocb_done(ocb, ct, ctlen, pt, tagbuf, &tagbuflen, 1)) != CRYPT_OK) { 57 goto LBL_ERR; 58 } 59 60 if (taglen <= tagbuflen && XMEMCMP(tagbuf, tag, taglen) == 0) { 61 *stat = 1; 62 } 63 64 err = CRYPT_OK; 65 LBL_ERR: 66 #ifdef LTC_CLEAN_STACK 67 zeromem(tagbuf, MAXBLOCKSIZE); 68 #endif 69 70 XFREE(tagbuf); 71 72 return err; 73 } 74 75 #endif 76 77 78 /* $Source: /cvs/libtom/libtomcrypt/src/encauth/ocb/ocb_done_decrypt.c,v $ */ 79 /* $Revision: 1.5 $ */ 80 /* $Date: 2006/11/01 09:28:17 $ */ 81
