/* LibTomCrypt, modular cryptographic library -- Tom St Denis */

/* SPDX-License-Identifier: Unlicense */

#include "tomcrypt_private.h"

/**

  @file hmac_done.c

  HMAC support, terminate stream, Tom St Denis/Dobes Vandermeer

*/

#ifdef LTC_HMAC

#define LTC_HMAC_BLOCKSIZE hash_descriptor[hash].blocksize

/**

   Terminate an HMAC session

   @param hmac    The HMAC state

   @param out     [out] The destination of the HMAC authentication tag

   @param outlen  [in/out]  The max size and resulting size of the HMAC authentication tag

   @return CRYPT_OK if successful

*/

int hmac_done(hmac_state *hmac, unsigned char *out, unsigned long *outlen)

{

    unsigned char *buf, *isha;

    unsigned long hashsize, i;

    int hash, err;

    LTC_ARGCHK(hmac  != NULL);

    LTC_ARGCHK(out   != NULL);

    /* test hash */

    hash = hmac->hash;

    if((err = hash_is_valid(hash)) != CRYPT_OK) {

        return err;

    }

    /* get the hash message digest size */

    hashsize = hash_descriptor[hash].hashsize;

    /* allocate buffers */

    buf  = XMALLOC(LTC_HMAC_BLOCKSIZE);

    isha = XMALLOC(hashsize);

    if (buf == NULL || isha == NULL) {

       if (buf != NULL) {

          XFREE(buf);

       }

       if (isha != NULL) {

          XFREE(isha);

       }

       return CRYPT_MEM;

    }

    /* Get the hash of the first HMAC vector plus the data */

    if ((err = hash_descriptor[hash].done(&hmac->md, isha)) != CRYPT_OK) {

       goto LBL_ERR;

    }

    /* Create the second HMAC vector vector for step (3) */

    for(i=0; i < LTC_HMAC_BLOCKSIZE; i++) {

        buf[i] = hmac->key[i] ^ 0x5C;

    }

    /* Now calculate the "outer" hash for step (5), (6), and (7) */

    if ((err = hash_descriptor[hash].init(&hmac->md)) != CRYPT_OK) {

       goto LBL_ERR;

    }

    if ((err = hash_descriptor[hash].process(&hmac->md, buf, LTC_HMAC_BLOCKSIZE)) != CRYPT_OK) {

       goto LBL_ERR;

    }

    if ((err = hash_descriptor[hash].process(&hmac->md, isha, hashsize)) != CRYPT_OK) {

       goto LBL_ERR;

    }

    if ((err = hash_descriptor[hash].done(&hmac->md, buf)) != CRYPT_OK) {

       goto LBL_ERR;

    }

    /* copy to output  */

    for (i = 0; i < hashsize && i < *outlen; i++) {

        out[i] = buf[i];

    }

    *outlen = i;

    err = CRYPT_OK;

LBL_ERR:

#ifdef LTC_CLEAN_STACK

    zeromem(isha, hashsize);

    zeromem(buf,  hashsize);

    zeromem(hmac, sizeof(*hmac));

#endif

    XFREE(isha);

    XFREE(buf);

    return err;

}

#endif