Split payload application code into a subdirectory.

This patch splits from the main libupdate_engine code the part that
is strictly used to download and apply a payload into a new static
library, moving the code to subdirectories. The new library is divided
in two subdirectories: common/ and payload_consumer/, and should not
depend on other update_engine files outside those two subdirectories.
The main difference between those two is that the common/ tools are more
generic and not tied to the payload consumer process, but otherwise they
are both compiled together.

There are still dependencies from the new libpayload_consumer library
into the main directory files and DBus generated files. Those will be
addressed in follow up CLs.

Bug: 25197634
Test: FEATURES=test emerge-link update_engine; `mm` on Brillo.

Change-Id: Id8d0204ea573627e6e26ca9ea17b9592ca95bc23
diff --git a/payload_consumer/payload_verifier.h b/payload_consumer/payload_verifier.h
new file mode 100644
index 0000000..22ced40
--- /dev/null
+++ b/payload_consumer/payload_verifier.h
@@ -0,0 +1,65 @@
+//
+// Copyright (C) 2014 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef UPDATE_ENGINE_PAYLOAD_CONSUMER_PAYLOAD_VERIFIER_H_
+#define UPDATE_ENGINE_PAYLOAD_CONSUMER_PAYLOAD_VERIFIER_H_
+
+#include <string>
+#include <vector>
+
+#include <base/macros.h>
+#include <brillo/secure_blob.h>
+
+#include "update_engine/update_metadata.pb.h"
+
+// This class encapsulates methods used for payload signature verification.
+// See payload_generator/payload_signer.h for payload signing.
+
+namespace chromeos_update_engine {
+
+class PayloadVerifier {
+ public:
+  // Interprets |signature_blob| as a protocol buffer containing the Signatures
+  // message and decrypts each signature data using the |public_key_path|.
+  // Returns whether *any* of the decrypted hashes matches the |hash_data|.
+  // In case of any error parsing the signatures or the public key, returns
+  // false.
+  static bool VerifySignature(const brillo::Blob& signature_blob,
+                              const std::string& public_key_path,
+                              const brillo::Blob& hash_data);
+
+  // Decrypts sig_data with the given public_key_path and populates
+  // out_hash_data with the decoded raw hash. Returns true if successful,
+  // false otherwise.
+  static bool GetRawHashFromSignature(const brillo::Blob& sig_data,
+                                      const std::string& public_key_path,
+                                      brillo::Blob* out_hash_data);
+
+  // Pads a SHA256 hash so that it may be encrypted/signed with RSA2048
+  // using the PKCS#1 v1.5 scheme.
+  // hash should be a pointer to vector of exactly 256 bits. The vector
+  // will be modified in place and will result in having a length of
+  // 2048 bits. Returns true on success, false otherwise.
+  static bool PadRSA2048SHA256Hash(brillo::Blob* hash);
+
+ private:
+  // This should never be constructed
+  DISALLOW_IMPLICIT_CONSTRUCTORS(PayloadVerifier);
+};
+
+}  // namespace chromeos_update_engine
+
+#endif  // UPDATE_ENGINE_PAYLOAD_CONSUMER_PAYLOAD_VERIFIER_H_