Vboot Reference: Add the "real" reference firmware verification function (VerifyFirmware).

src/platform/vboot_reference/include/file_keys.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.
  *
  * Utility functions for file and key handling.
  */
 
 #ifndef VBOOT_REFERENCE_FILE_KEYS_H_
 #define VBOOT_REFERENCE_FILE_KEYS_H_
 
 #include "rsa.h"
 
 /* Read file named [input_file] into a buffer and stores the length into
  * [len].
  *
  * Returns a pointer to the buffer. Caller owns the returned pointer and
  * must free it.
  */
 uint8_t* BufferFromFile(char* input_file, int* len);
 
 /* Read a pre-processed RSA Public Key from file [input_file].
  *
  * Returns a pointer to the read key. Caller owns the returned pointer and
  * must free it.
  */
 RSAPublicKey* RSAPublicKeyFromFile(char* input_file);
 
+/* Helper function to invoke external program to calculate signature on
+ * [input_file] using private key [key_file] and signature algorithm
+ * [algorithm].
+ *
+ * Returns the signature. Caller owns the buffer and must Free() it.
+ */
+uint8_t* SignatureFile(char* input_fie, char* key_file, int algorithm);
+
 #endif  /* VBOOT_REFERENCE_FILE_KEYS_H_ */