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110 lines
2.9 KiB
C
110 lines
2.9 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*/
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/**
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@file eax_decrypt_verify_memory.c
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EAX implementation, decrypt block of memory, by Tom St Denis
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*/
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#include "tomcrypt.h"
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#ifdef LTC_EAX_MODE
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/**
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Decrypt a block of memory and verify the provided MAC tag with EAX
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@param cipher The index of the cipher desired
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@param key The secret key
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@param keylen The length of the key (octets)
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@param nonce The nonce data (use once) for the session
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@param noncelen The length of the nonce data.
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@param header The session header data
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@param headerlen The length of the header (octets)
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@param ct The ciphertext
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@param ctlen The length of the ciphertext (octets)
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@param pt [out] The plaintext
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@param tag The authentication tag provided by the encoder
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@param taglen [in/out] The length of the tag (octets)
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@param stat [out] The result of the decryption (1==valid tag, 0==invalid)
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@return CRYPT_OK if successful regardless of the resulting tag comparison
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*/
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int eax_decrypt_verify_memory(int cipher,
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const unsigned char *key, unsigned long keylen,
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const unsigned char *nonce, unsigned long noncelen,
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const unsigned char *header, unsigned long headerlen,
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const unsigned char *ct, unsigned long ctlen,
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unsigned char *pt,
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unsigned char *tag, unsigned long taglen,
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int *stat)
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{
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int err;
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eax_state *eax;
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unsigned char *buf;
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unsigned long buflen;
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LTC_ARGCHK(stat != NULL);
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LTC_ARGCHK(key != NULL);
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LTC_ARGCHK(pt != NULL);
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LTC_ARGCHK(ct != NULL);
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LTC_ARGCHK(tag != NULL);
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/* default to zero */
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*stat = 0;
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/* limit taglen */
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taglen = MIN(taglen, MAXBLOCKSIZE);
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/* allocate ram */
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buf = XMALLOC(taglen);
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eax = XMALLOC(sizeof(*eax));
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if (eax == NULL || buf == NULL) {
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if (eax != NULL) {
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XFREE(eax);
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}
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if (buf != NULL) {
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XFREE(buf);
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}
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return CRYPT_MEM;
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}
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if ((err = eax_init(eax, cipher, key, keylen, nonce, noncelen, header, headerlen)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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if ((err = eax_decrypt(eax, ct, pt, ctlen)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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buflen = taglen;
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if ((err = eax_done(eax, buf, &buflen)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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/* compare tags */
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if (buflen >= taglen && XMEM_NEQ(buf, tag, taglen) == 0) {
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*stat = 1;
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}
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err = CRYPT_OK;
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LBL_ERR:
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#ifdef LTC_CLEAN_STACK
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zeromem(buf, taglen);
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zeromem(eax, sizeof(*eax));
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#endif
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XFREE(eax);
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XFREE(buf);
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return err;
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}
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#endif
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/* ref: HEAD -> master, tag: v1.18.2 */
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/* git commit: 7e7eb695d581782f04b24dc444cbfde86af59853 */
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/* commit time: 2018-07-01 22:49:01 +0200 */
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