--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/pk/rsa/rsa_verify_hash.c	Sat Feb 03 08:20:34 2007 +0000
@@ -0,0 +1,167 @@
+/* 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 rsa_verify_hash.c
+  RSA PKCS #1 v1.5 or v2 PSS signature verification, Tom St Denis and Andreas Lange
+*/
+
+#ifdef MRSA
+
+/**
+  PKCS #1 de-sign then v1.5 or PSS depad
+  @param sig              The signature data
+  @param siglen           The length of the signature data (octets)
+  @param hash             The hash of the message that was signed
+  @param hashlen          The length of the hash of the message that was signed (octets)
+  @param padding          Type of padding (LTC_PKCS_1_PSS or LTC_PKCS_1_V1_5)
+  @param hash_idx         The index of the desired hash
+  @param saltlen          The length of the salt used during signature
+  @param stat             [out] The result of the signature comparison, 1==valid, 0==invalid
+  @param key              The public RSA key corresponding to the key that performed the signature
+  @return CRYPT_OK on success (even if the signature is invalid)
+*/
+int rsa_verify_hash_ex(const unsigned char *sig,      unsigned long siglen,
+                       const unsigned char *hash,     unsigned long hashlen,
+                             int            padding,
+                             int            hash_idx, unsigned long saltlen,
+                             int           *stat,     rsa_key      *key)
+{
+  unsigned long modulus_bitlen, modulus_bytelen, x;
+  int           err;
+  unsigned char *tmpbuf;
+
+  LTC_ARGCHK(hash  != NULL);
+  LTC_ARGCHK(sig   != NULL);
+  LTC_ARGCHK(stat  != NULL);
+  LTC_ARGCHK(key   != NULL);
+
+  /* default to invalid */
+  *stat = 0;
+
+  /* valid padding? */
+
+  if ((padding != LTC_PKCS_1_V1_5) &&
+      (padding != LTC_PKCS_1_PSS)) {
+    return CRYPT_PK_INVALID_PADDING;
+  }
+
+  if (padding == LTC_PKCS_1_PSS) {
+    /* valid hash ? */
+    if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
+       return err;
+    }
+  }
+
+  /* get modulus len in bits */
+  modulus_bitlen = mp_count_bits( (key->N));
+
+  /* outlen must be at least the size of the modulus */
+  modulus_bytelen = mp_unsigned_bin_size( (key->N));
+  if (modulus_bytelen != siglen) {
+     return CRYPT_INVALID_PACKET;
+  }
+
+  /* allocate temp buffer for decoded sig */
+  tmpbuf = XMALLOC(siglen);
+  if (tmpbuf == NULL) {
+     return CRYPT_MEM;
+  }
+
+  /* RSA decode it  */
+  x = siglen;
+  if ((err = ltc_mp.rsa_me(sig, siglen, tmpbuf, &x, PK_PUBLIC, key)) != CRYPT_OK) {
+     XFREE(tmpbuf);
+     return err;
+  }
+
+  /* make sure the output is the right size */
+  if (x != siglen) {
+     XFREE(tmpbuf);
+     return CRYPT_INVALID_PACKET;
+  }
+
+  if (padding == LTC_PKCS_1_PSS) {
+    /* PSS decode and verify it */
+    err = pkcs_1_pss_decode(hash, hashlen, tmpbuf, x, saltlen, hash_idx, modulus_bitlen, stat);
+  } else {
+    /* PKCS #1 v1.5 decode it */
+    unsigned char *out;
+    unsigned long outlen, loid[16];
+    int           decoded;
+    ltc_asn1_list digestinfo[2], siginfo[2];
+
+    /* not all hashes have OIDs... so sad */
+    if (hash_descriptor[hash_idx].OIDlen == 0) {
+       err = CRYPT_INVALID_ARG;
+       goto bail_2;
+    }
+
+    /* allocate temp buffer for decoded hash */
+    outlen = ((modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0)) - 3;
+    out    = XMALLOC(outlen);
+    if (out == NULL) {
+      err = CRYPT_MEM;
+      goto bail_2;
+    }
+
+    if ((err = pkcs_1_v1_5_decode(tmpbuf, x, LTC_PKCS_1_EMSA, modulus_bitlen, out, &outlen, &decoded)) != CRYPT_OK) {
+      XFREE(out);       
+      goto bail_2;
+    }
+
+    /* now we must decode out[0...outlen-1] using ASN.1, test the OID and then test the hash */
+    /* construct the SEQUENCE 
+      SEQUENCE {
+         SEQUENCE {hashoid OID
+                   blah    NULL
+         }
+         hash    OCTET STRING 
+      }
+   */
+    LTC_SET_ASN1(digestinfo, 0, LTC_ASN1_OBJECT_IDENTIFIER, loid, sizeof(loid)/sizeof(loid[0]));
+    LTC_SET_ASN1(digestinfo, 1, LTC_ASN1_NULL,              NULL,                          0);
+    LTC_SET_ASN1(siginfo,    0, LTC_ASN1_SEQUENCE,          digestinfo,                    2);
+    LTC_SET_ASN1(siginfo,    1, LTC_ASN1_OCTET_STRING,      tmpbuf,                        siglen);
+   
+    if ((err = der_decode_sequence(out, outlen, siginfo, 2)) != CRYPT_OK) {
+       XFREE(out);
+       goto bail_2;
+    }
+
+    /* test OID */
+    if ((digestinfo[0].size == hash_descriptor[hash_idx].OIDlen) &&
+        (XMEMCMP(digestinfo[0].data, hash_descriptor[hash_idx].OID, sizeof(unsigned long) * hash_descriptor[hash_idx].OIDlen) == 0) &&
+        (siginfo[1].size == hashlen) &&
+        (XMEMCMP(siginfo[1].data, hash, hashlen) == 0)) {
+       *stat = 1;
+    }
+
+#ifdef LTC_CLEAN_STACK
+    zeromem(out, outlen);
+#endif
+    XFREE(out);
+  }
+
+bail_2:
+#ifdef LTC_CLEAN_STACK
+  zeromem(tmpbuf, siglen);
+#endif
+  XFREE(tmpbuf);
+  return err;
+}
+
+#endif /* MRSA */
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/rsa/rsa_verify_hash.c,v $ */
+/* $Revision: 1.11 $ */
+/* $Date: 2006/12/04 03:09:28 $ */