Fixes to compiler warnings in MSVC

firmware/lib/cryptolib/include/rsa.h

 /* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef VBOOT_REFERENCE_RSA_H_
 #define VBOOT_REFERENCE_RSA_H_
 
 #ifndef VBOOT_REFERENCE_CRYPTOLIB_H_
 #error "Do not include this file directly. Use cryptolib.h instead."
@@ skipping 17 matching lines @@
   uint32_t* n;  /* modulus as little endian array */
   uint32_t* rr; /* R^2 as little endian array */
   int algorithm; /* Algorithm to use when verifying binaries with the key */
 } RSAPublicKey;
 
 /* Verify a RSA PKCS1.5 signature [sig] of [sig_type] and length [sig_len]
  * against an expected [hash] using [key]. Returns 0 on failure, 1 on success.
  */
 int RSAVerify(const RSAPublicKey *key,
               const uint8_t* sig,
-              const int sig_len,
+              const uint32_t sig_len,
               const uint8_t sig_type,
               const uint8_t* hash);
 
 /* Perform RSA signature verification on [buf] of length [len] against expected
  * signature [sig] using signature algorithm [algorithm]. The public key used
  * for verification can either be in the form of a pre-process key blob
  * [key_blob] or RSAPublicKey structure [key]. One of [key_blob] or [key] must
  * be non-NULL, and the other NULL or the function will fail.
  *
  * Returns 1 on verification success, 0 on verification failure or invalid
@@ skipping 34 matching lines @@
 
 /* Create a RSAPublic key structure from binary blob [buf] of length
  * [len].
  *
  * Caller owns the returned key and must free it.
  */
 RSAPublicKey* RSAPublicKeyFromBuf(const uint8_t* buf, int len);
 
 
 #endif  /* VBOOT_REFERENCE_RSA_H_ */