Add additional sanity checks to RSA verification code.

firmware/lib/cryptolib/rsa.c

 /* 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.
  */
 
 /* Implementation of RSA signature verification which uses a pre-processed
  * key for computation. The code extends Android's RSA verification code to
  * support multiple RSA key lengths and hash digest algorithms.
  */
 
@@ skipping 116 matching lines @@
 int RSAVerify(const RSAPublicKey *key,
               const uint8_t *sig,
               const uint32_t sig_len,
               const uint8_t sig_type,
               const uint8_t *hash) {
   int i;
   uint8_t* buf;
   const uint8_t* padding;
   int success = 1;
 
+  if (!key || !sig || !hash)
+    return 0;
+
   if (sig_len != (key->len * sizeof(uint32_t))) {
     VBDEBUG(("Signature is of incorrect length!\n"));
     return 0;
   }
 
   if (sig_type >= kNumAlgorithms) {
     VBDEBUG(("Invalid signature type!\n"));
     return 0;
   }
 
@@ skipping 29 matching lines @@
       VBDEBUG(("Digest: Expecting = %02x Got = %02x\n", padding[i], buf[i]));
 #endif
       success = 0;
     }
   }
 
   Free(buf);
 
   return success;
 }