/* 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, [email protected], http://libtomcrypt.com
 */
#include "tomcrypt.h"

/**
   @file dsa_sign_hash.c
   DSA implementation, sign a hash, Tom St Denis
*/

#ifdef MDSA

/**
  Sign a hash with DSA
  @param in       The hash to sign
  @param inlen    The length of the hash to sign
  @param r        The "r" integer of the signature (caller must initialize with mp_init() first)
  @param s        The "s" integer of the signature (caller must initialize with mp_init() first)
  @param prng     An active PRNG state
  @param wprng    The index of the PRNG desired
  @param key      A private DSA key
  @return CRYPT_OK if successful
*/
int dsa_sign_hash_raw(const unsigned char *in,  unsigned long inlen,
                                   void   *r,   void *s,
                               prng_state *prng, int wprng, dsa_key *key)
{
   void         *k, *kinv, *tmp;
   unsigned char *buf;
   int            err;

   LTC_ARGCHK(in  != NULL);
   LTC_ARGCHK(r   != NULL);
   LTC_ARGCHK(s   != NULL);
   LTC_ARGCHK(key != NULL);

   if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
      return err;
   }
   if (key->type != PK_PRIVATE) {
      return CRYPT_PK_NOT_PRIVATE;
   }

   /* check group order size  */
   if (key->qord >= MDSA_MAX_GROUP) {
      return CRYPT_INVALID_ARG;
   }

   buf = XMALLOC(MDSA_MAX_GROUP);
   if (buf == NULL) {
      return CRYPT_MEM;
   }

   /* Init our temps */
   if ((err = mp_init_multi(&k, &kinv, &tmp, NULL)) != CRYPT_OK)                       { goto ERRBUF; }

retry:

   do {
      /* gen random k */
      if (prng_descriptor[wprng].read(buf, key->qord, prng) != (unsigned long)key->qord) {
         err = CRYPT_ERROR_READPRNG;
         goto error;
      }

      /* read k */
      if ((err = mp_read_unsigned_bin(k, buf, key->qord)) != CRYPT_OK)                 { goto error; }

      /* k > 1 ? */
      if (mp_cmp_d(k, 1) != LTC_MP_GT)                                                 { goto retry; }

      /* test gcd */
      if ((err = mp_gcd(k, key->q, tmp)) != CRYPT_OK)                                  { goto error; }