/* 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_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 && memcmp(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: 1.3 $ *//* $Date: 2005/05/05 14:35:58 $ */