crypto: add OpenPGP symmetric encryption for ChromeOS

crypto/openpgp_symmetric_encryption.h

+// Copyright (c) 2011 The Chromium 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 CRYPTO_OPENPGP_SYMMETRIC_ENCRYPTION_H_
+#define CRYPTO_OPENPGP_SYMMETRIC_ENCRYPTION_H_
+#pragma once
+
+#include <string>
+
+#include "base/string_piece.h"
+
+namespace crypto {
+
+// OpenPGPSymmetricEncrytion implements enough of RFC 4880 to read and write
+// uncompressed, symmetrically encrypted data. You can create ciphertext
+// compatable with this code from the command line with:
+//    gpg --compress-algo=NONE --cipher-algo=AES -c
+//
+// Likewise, the output of this can be decrypted on the command line with:
+//    gpg < input
+class OpenPGPSymmetricEncrytion {
+ public:
+  enum Result {
+    OK,
+    UNKNOWN_CIPHER,  // you forgot to pass --cipher-algo=AES to gpg
+    UNKNOWN_HASH,
+    NOT_SYMMETRICALLY_ENCRYPTED,  // it's OpenPGP data, but not correct form
+    COMPRESSED,  // you forgot to pass --compress-algo=NONE
+    PARSE_ERROR,  // it's not OpenPGP data.
+    INTERNAL_ERROR,
+  };
+
+  static Result Decrypt(base::StringPiece encrypted,
+                        base::StringPiece passphrase,
+                        std::string *out);
+
+  static std::string Encrypt(base::StringPiece plaintext,
+                             base::StringPiece passphrase);
+};
+
+}  // namespace crypto
+
+#endif  // CRYPTO_OPENPGP_SYMMETRIC_ENCRYPTION_H_
+