Relanding Porting of HKDF changes from server.

crypto/hkdf.h

+// Copyright (c) 2013 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_HKDF_H_
+#define CRYPTO_HKDF_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/string_piece.h"
+#include "build/build_config.h"
+#include "crypto/crypto_export.h"
+
+namespace crypto {
+
+// HKDF implements the key derivation function specified in RFC 5869 (using
+// SHA-256) and outputs key material, as needed by QUIC.
+// See https://tools.ietf.org/html/rfc5869 for details.
+class CRYPTO_EXPORT HKDF {
+ public:
+  // |secret|: The input shared secret (or, from RFC 5869, the IKM).
+  // |salt|: an (optional) public salt / non-secret random value. While
+  // optional, callers are strongly recommended to provide a salt. There is no
+  // added security value in making this larger than the SHA-256 block size of
+  // 64 bytes.
+  // |info|: an (optional) label to distinguish different uses of HKDF. It is
+  // optional context and application specific information (can be a zero-length
+  // string).
+  // |key_bytes_to_generate|: the number of bytes of key material to generate.
+  // |iv_bytes_to_generate|: the number of bytes of IV to generate.
+  HKDF(const base::StringPiece& secret,
+       const base::StringPiece& salt,
+       const base::StringPiece& info,
+       size_t key_bytes_to_generate,
+       size_t iv_bytes_to_generate);
+  virtual ~HKDF();
+
+  base::StringPiece client_write_key() const {
+    return client_write_key_;
+  }
+  base::StringPiece client_write_iv() const {
+    return client_write_iv_;
+  }
+  base::StringPiece server_write_key() const {
+    return server_write_key_;
+  }
+  base::StringPiece server_write_iv() const {
+    return server_write_iv_;
+  }
+
+ private:
+  std::vector<uint8> output_;
+
+  base::StringPiece client_write_key_;
+  base::StringPiece server_write_key_;
+  base::StringPiece client_write_iv_;
+  base::StringPiece server_write_iv_;
+};
+
+}  // namespace crypto
+
+#endif  // CRYPTO_HKDF_H_