| /* 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.com |
| */ |
| |
| /** |
| @file eax_decrypt_verify_memory.c |
| EAX implementation, decrypt block of memory, by Tom St Denis |
| */ |
| #include "tomcrypt.h" |
| |
| #ifdef EAX_MODE |
| |
| /** |
| Decrypt a block of memory and verify the provided MAC tag with EAX |
| @param cipher The index of the cipher desired |
| @param key The secret key |
| @param keylen The length of the key (octets) |
| @param nonce The nonce data (use once) for the session |
| @param noncelen The length of the nonce data. |
| @param header The session header data |
| @param headerlen The length of the header (octets) |
| @param ct The ciphertext |
| @param ctlen The length of the ciphertext (octets) |
| @param pt [out] The plaintext |
| @param tag The authentication tag provided by the encoder |
| @param taglen [in/out] The length of the tag (octets) |
| @param stat [out] The result of the decryption (1==valid tag, 0==invalid) |
| @return CRYPT_OK if successful regardless of the resulting tag comparison |
| */ |
| int eax_decrypt_verify_memory(int cipher, |
| const unsigned char *key, unsigned long keylen, |
| const unsigned char *nonce, unsigned long noncelen, |
| const unsigned char *header, unsigned long headerlen, |
| const unsigned char *ct, unsigned long ctlen, |
| unsigned char *pt, |
| unsigned char *tag, unsigned long taglen, |
| int *stat) |
| { |
| int err; |
| eax_state *eax; |
| unsigned char *buf; |
| unsigned long buflen; |
| |
| LTC_ARGCHK(stat != NULL); |
| LTC_ARGCHK(key != NULL); |
| LTC_ARGCHK(pt != NULL); |
| LTC_ARGCHK(ct != NULL); |
| LTC_ARGCHK(tag != NULL); |
| |
| /* default to zero */ |
| *stat = 0; |
| |
| /* allocate ram */ |
| buf = XMALLOC(taglen); |
| eax = XMALLOC(sizeof(*eax)); |
| if (eax == NULL || buf == NULL) { |
| if (eax != NULL) { |
| XFREE(eax); |
| } |
| if (buf != NULL) { |
| XFREE(buf); |
| } |
| return CRYPT_MEM; |
| } |
| |
| if ((err = eax_init(eax, cipher, key, keylen, nonce, noncelen, header, headerlen)) != CRYPT_OK) { |
| goto LBL_ERR; |
| } |
| |
| if ((err = eax_decrypt(eax, ct, pt, ctlen)) != CRYPT_OK) { |
| goto LBL_ERR; |
| } |
| |
| buflen = taglen; |
| if ((err = eax_done(eax, buf, &buflen)) != CRYPT_OK) { |
| goto LBL_ERR; |
| } |
| |
| /* compare tags */ |
| if (buflen >= taglen && XMEMCMP(buf, tag, taglen) == 0) { |
| *stat = 1; |
| } |
| |
| err = CRYPT_OK; |
| LBL_ERR: |
| #ifdef LTC_CLEAN_STACK |
| zeromem(buf, taglen); |
| zeromem(eax, sizeof(*eax)); |
| #endif |
| |
| XFREE(eax); |
| XFREE(buf); |
| |
| return err; |
| } |
| |
| #endif |
| |
| /* $Source: /cvs/libtom/libtomcrypt/src/encauth/eax/eax_decrypt_verify_memory.c,v $ */ |
| /* $Revision: 1.5 $ */ |
| /* $Date: 2006/11/01 09:28:17 $ */ |