--- a/src/pk/dsa/dsa_verify_hash.c	Fri May 06 13:23:02 2005 +0000
+++ b/src/pk/dsa/dsa_verify_hash.c	Wed Jul 06 03:53:40 2005 +0000
@@ -20,6 +20,71 @@
 
 /**
   Verify a DSA signature
+  @param r        DSA "r" parameter
+  @param s        DSA "s" parameter
+  @param hash     The hash that was signed
+  @param hashlen  The length of the hash that was signed
+  @param stat     [out] The result of the signature verification, 1==valid, 0==invalid
+  @param key      The corresponding public DH key
+  @return CRYPT_OK if successful (even if the signature is invalid)
+*/
+int dsa_verify_hash_raw(         mp_int *r,          mp_int *s,
+                    const unsigned char *hash, unsigned long hashlen, 
+                                    int *stat,      dsa_key *key)
+{
+   mp_int        w, v, u1, u2;
+   int           err;
+
+   LTC_ARGCHK(r    != NULL);
+   LTC_ARGCHK(s    != NULL);
+   LTC_ARGCHK(stat != NULL);
+   LTC_ARGCHK(key  != NULL);
+
+   /* default to invalid signature */
+   *stat = 0;
+
+   /* init our variables */
+   if ((err = mp_init_multi(&w, &v, &u1, &u2, NULL)) != MP_OKAY) {
+      return mpi_to_ltc_error(err);
+   }
+
+   /* neither r or s can be null or >q*/
+   if (mp_iszero(r) == MP_YES || mp_iszero(s) == MP_YES || mp_cmp(r, &key->q) != MP_LT || mp_cmp(s, &key->q) != MP_LT) {
+      err = CRYPT_INVALID_PACKET;
+      goto done;
+   }
+   
+   /* w = 1/s mod q */
+   if ((err = mp_invmod(s, &key->q, &w)) != MP_OKAY)                                      { goto error; }
+
+   /* u1 = m * w mod q */
+   if ((err = mp_read_unsigned_bin(&u1, (unsigned char *)hash, hashlen)) != MP_OKAY)       { goto error; }
+   if ((err = mp_mulmod(&u1, &w, &key->q, &u1)) != MP_OKAY)                                { goto error; }
+
+   /* u2 = r*w mod q */
+   if ((err = mp_mulmod(r, &w, &key->q, &u2)) != MP_OKAY)                                 { goto error; } 
+
+   /* v = g^u1 * y^u2 mod p mod q */
+   if ((err = mp_exptmod(&key->g, &u1, &key->p, &u1)) != MP_OKAY)                          { goto error; }
+   if ((err = mp_exptmod(&key->y, &u2, &key->p, &u2)) != MP_OKAY)                          { goto error; }
+   if ((err = mp_mulmod(&u1, &u2, &key->p, &v)) != MP_OKAY)                                { goto error; }
+   if ((err = mp_mod(&v, &key->q, &v)) != MP_OKAY)                                         { goto error; }
+
+   /* if r = v then we're set */
+   if (mp_cmp(r, &v) == MP_EQ) {
+      *stat = 1;
+   }
+
+   err = CRYPT_OK;
+   goto done;
+
+error : err = mpi_to_ltc_error(err);
+done  : mp_clear_multi(&w, &v, &u1, &u2, NULL);
+   return err;
+}
+
+/**
+  Verify a DSA signature
   @param sig      The signature
   @param siglen   The length of the signature (octets)
   @param hash     The hash that was signed
@@ -32,59 +97,32 @@
                     const unsigned char *hash, unsigned long hashlen, 
                     int *stat, dsa_key *key)
 {
-   mp_int        r, s, w, v, u1, u2;
-   int           err;
+   int    err;
+   mp_int r, s;
 
-   LTC_ARGCHK(sig  != NULL);
-   LTC_ARGCHK(hash != NULL);
-   LTC_ARGCHK(stat != NULL);
-   LTC_ARGCHK(key  != NULL);
-
-   /* default to invalid signature */
-   *stat = 0;
-
-   /* init our variables */
-   if ((err = mp_init_multi(&r, &s, &w, &v, &u1, &u2, NULL)) != MP_OKAY) {
-      return mpi_to_ltc_error(err);
+   if ((err = mp_init_multi(&r, &s, NULL)) != CRYPT_OK) {
+      return CRYPT_MEM;
    }
 
-   /* read in r followed by s */
-   if ((err = der_get_multi_integer(sig, &siglen, &r, &s, NULL)) != CRYPT_OK)              { goto done; }
-
-   /* neither r or s can be null */
-   if (mp_iszero(&r) == MP_YES || mp_iszero(&s) == MP_YES) {
-      err = CRYPT_INVALID_PACKET;
-      goto done;
-   }
-   
-   /* w = 1/s mod q */
-   if ((err = mp_invmod(&s, &key->q, &w)) != MP_OKAY)                                      { goto error; }
-
-   /* u1 = m * w mod q */
-   if ((err = mp_read_unsigned_bin(&u1, (unsigned char *)hash, hashlen)) != MP_OKAY)       { goto error; }
-   if ((err = mp_mulmod(&u1, &w, &key->q, &u1)) != MP_OKAY)                                { goto error; }
-
-   /* u2 = r*w mod q */
-   if ((err = mp_mulmod(&r, &w, &key->q, &u2)) != MP_OKAY)                                 { goto error; } 
-
-   /* v = g^u1 * y^u2 mod p mod q */
-   if ((err = mp_exptmod(&key->g, &u1, &key->p, &u1)) != MP_OKAY)                          { goto error; }
-   if ((err = mp_exptmod(&key->y, &u2, &key->p, &u2)) != MP_OKAY)                          { goto error; }
-   if ((err = mp_mulmod(&u1, &u2, &key->p, &v)) != MP_OKAY)                                { goto error; }
-   if ((err = mp_mod(&v, &key->q, &v)) != MP_OKAY)                                         { goto error; }
-
-   /* if r = v then we're set */
-   if (mp_cmp(&r, &v) == MP_EQ) {
-      *stat = 1;
+   /* decode the sequence */
+   if ((err = der_decode_sequence_multi(sig, siglen,
+                                  LTC_ASN1_INTEGER, 1UL, &r, 
+                                  LTC_ASN1_INTEGER, 1UL, &s, 
+                                  LTC_ASN1_EOL,     0UL, NULL)) != CRYPT_OK) {
+      goto LBL_ERR;
    }
 
-   err = CRYPT_OK;
-   goto done;
+   /* do the op */
+   err = dsa_verify_hash_raw(&r, &s, hash, hashlen, stat, key);
 
-error : err = mpi_to_ltc_error(err);
-done  : mp_clear_multi(&r, &s, &w, &v, &u1, &u2, NULL);
+LBL_ERR:
+   mp_clear_multi(&r, &s, NULL);
    return err;
 }
 
 #endif
 
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/dsa/dsa_verify_hash.c,v $ */
+/* $Revision: 1.8 $ */
+/* $Date: 2005/05/15 21:48:59 $ */