| /* LibTomCrypt, modular cryptographic library -- Tom St Denis |
| * |
| * LibTomCrypt is a library that provides various cryptographic |
| * algorithms in a highly modular and flexible manner. |
| * |
| * The library is free for all purposes without any express |
| * guarantee it works. |
| * |
| * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.org |
| */ |
| |
| /** |
| @file eax_done.c |
| EAX implementation, terminate session, by Tom St Denis |
| */ |
| #include "tomcrypt.h" |
| |
| #ifdef EAX_MODE |
| |
| /** |
| Terminate an EAX session and get the tag. |
| @param eax The EAX state |
| @param tag [out] The destination of the authentication tag |
| @param taglen [in/out] The max length and resulting length of the authentication tag |
| @return CRYPT_OK if successful |
| */ |
| int eax_done(eax_state *eax, unsigned char *tag, unsigned long *taglen) |
| { |
| int err; |
| unsigned char *headermac, *ctmac; |
| unsigned long x, len; |
| |
| LTC_ARGCHK(eax != NULL); |
| LTC_ARGCHK(tag != NULL); |
| LTC_ARGCHK(taglen != NULL); |
| |
| /* allocate ram */ |
| headermac = XMALLOC(MAXBLOCKSIZE); |
| ctmac = XMALLOC(MAXBLOCKSIZE); |
| |
| if (headermac == NULL || ctmac == NULL) { |
| if (headermac != NULL) { |
| XFREE(headermac); |
| } |
| if (ctmac != NULL) { |
| XFREE(ctmac); |
| } |
| return CRYPT_MEM; |
| } |
| |
| /* finish ctomac */ |
| len = MAXBLOCKSIZE; |
| if ((err = omac_done(&eax->ctomac, ctmac, &len)) != CRYPT_OK) { |
| goto LBL_ERR; |
| } |
| |
| /* finish headeromac */ |
| |
| /* note we specifically don't reset len so the two lens are minimal */ |
| |
| if ((err = omac_done(&eax->headeromac, headermac, &len)) != CRYPT_OK) { |
| goto LBL_ERR; |
| } |
| |
| /* terminate the CTR chain */ |
| if ((err = ctr_done(&eax->ctr)) != CRYPT_OK) { |
| goto LBL_ERR; |
| } |
| |
| /* compute N xor H xor C */ |
| for (x = 0; x < len && x < *taglen; x++) { |
| tag[x] = eax->N[x] ^ headermac[x] ^ ctmac[x]; |
| } |
| *taglen = x; |
| |
| err = CRYPT_OK; |
| LBL_ERR: |
| #ifdef LTC_CLEAN_STACK |
| zeromem(ctmac, MAXBLOCKSIZE); |
| zeromem(headermac, MAXBLOCKSIZE); |
| zeromem(eax, sizeof(*eax)); |
| #endif |
| |
| XFREE(ctmac); |
| XFREE(headermac); |
| |
| return err; |
| } |
| |
| #endif |