AU: Verify delta payload signature and signed hash.

payload_signer.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 CHROMEOS_PLATFORM_UPDATE_ENGINE_PAYLOAD_SIGNER_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_PAYLOAD_SIGNER_H__
 
 #include <string>
 #include <vector>
 #include "base/basictypes.h"
@@ skipping 10 matching lines @@
  public:
   static bool SignPayload(const std::string& unsigned_payload_path,
                           const std::string& private_key_path,
                           std::vector<char>* out_signature_blob);
 
   // Returns the length of out_signature_blob that will result in a call
   // to SignPayload with a given private key. Returns true on success.
   static bool SignatureBlobLength(const std::string& private_key_path,
                                   uint64_t* out_length);
 
+  // Returns false if the payload signature can't be verified. Returns true
+  // otherwise and sets |out_hash| to the signed payload hash.
+  static bool VerifySignature(const std::vector<char>& signature_blob,
+                              const std::string& public_key_path,
+                              std::vector<char>* out_hash_data);
+
  private:
   // This should never be constructed
   DISALLOW_IMPLICIT_CONSTRUCTORS(PayloadSigner);
 };
 
 }  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_PAYLOAD_SIGNER_H__