Implementation of SecureP2PSocket

remoting/protocol/secure_p2p_socket.cc

+// 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.
+
+#include "remoting/protocol/secure_p2p_socket.h"
+
+#include "base/logging.h"
+#include "base/rand_util.h"
+#include "crypto/symmetric_key.h"
+#include "net/base/io_buffer.h"
+#include "net/base/net_errors.h"
+
+using net::CompletionCallback;
+using net::IOBuffer;
+
+namespace remoting {

[Wez, 2011/06/24 23:23:51]

nit: Add a blank line after namespace foo {.

[Sergey Ulanov, 2011/06/24 23:36:40]

IMO it is not necessary in case of nested namespaces like remoting::protocol.

+namespace protocol {
+
+namespace {

[Wez, 2011/06/24 23:23:51]

nit: Blank line after namespace {.

+const char kMaskSalt[16] = {0xDB, 0x68, 0xB5, 0xFD, 0x17, 0x0E, 0x15, 0x77,
+                            0x56, 0xAF, 0x7A, 0x3A, 0x1A, 0x57, 0x75, 0x02};
+const char kHashSalt[16] = {0x4E, 0x2F, 0x96, 0xAB, 0x0A, 0x39, 0x92, 0xA2,
+                            0x56, 0x94, 0x91, 0xF5, 0x7E, 0x58, 0x2E, 0xFA};
+const char kFrameType[4] = {0x0, 0x0, 0x0, 0x1};
+const int kFrameTypeSize = sizeof(kFrameType);
+const size_t kKeySize = 16;
+const int kHeaderSize = 44;
+const int kSeqNumberSize = 8;
+const int kHashPosition = 0;
+const int kNoncePosition = kKeySize;
+const int kRawMessagePosition = kNoncePosition + kKeySize;
+const int kSeqNumberPosition = kRawMessagePosition;
+const int kFrameTypePosition = kSeqNumberPosition + kSeqNumberSize;
+const int kMessagePosition = kFrameTypePosition + kFrameTypeSize;
+const int kReadBufferSize = 65536;
+const std::string kMaskSaltStr(kMaskSalt, kKeySize);
+const std::string kHashSaltStr(kHashSalt, kKeySize);
+
+inline void SetBE64(void* memory, uint64 v) {
+  uint8* mem_ptr = reinterpret_cast<uint8*>(memory);
+
+  mem_ptr[0] = static_cast<uint8>(v >> 56);
+  mem_ptr[1] = static_cast<uint8>(v >> 48);
+  mem_ptr[2] = static_cast<uint8>(v >> 40);
+  mem_ptr[3] = static_cast<uint8>(v >> 32);
+  mem_ptr[4] = static_cast<uint8>(v >> 24);
+  mem_ptr[5] = static_cast<uint8>(v >> 16);
+  mem_ptr[6] = static_cast<uint8>(v >>  8);
+  mem_ptr[7] = static_cast<uint8>(v >>  0);
+}
+
+inline uint64 GetBE64(const void* memory) {
+  const uint8* mem_ptr = reinterpret_cast<const uint8*>(memory);
+
+  return (static_cast<uint64>(mem_ptr[0]) << 56) |
+      (static_cast<uint64>(mem_ptr[1]) << 48) |
+      (static_cast<uint64>(mem_ptr[2]) << 40) |
+      (static_cast<uint64>(mem_ptr[3]) << 32) |
+      (static_cast<uint64>(mem_ptr[4]) << 24) |
+      (static_cast<uint64>(mem_ptr[5]) << 16) |
+      (static_cast<uint64>(mem_ptr[6]) <<  8) |
+      (static_cast<uint64>(mem_ptr[7]) <<  0);
+}
+
+}  // namespace
+
+////////////////////////////////////////////////////////////////////////////
+// SecureP2PSocket Implementation.
+SecureP2PSocket::SecureP2PSocket(Socket* socket, const std::string& ice_key)
+    : socket_(socket),
+      write_seq_(0),
+      read_seq_(0),
+      user_read_callback_(NULL),
+      user_read_buf_len_(0),
+      user_write_callback_(NULL),
+      user_write_buf_len_(0),
+      ALLOW_THIS_IN_INITIALIZER_LIST(
+          read_callback_(NewCallback(this, &SecureP2PSocket::ReadDone))),
+      read_buf_(new net::IOBufferWithSize(kReadBufferSize)),
+      ALLOW_THIS_IN_INITIALIZER_LIST(
+          write_callback_(NewCallback(this, &SecureP2PSocket::WriteDone))),
+      msg_hasher_(crypto::HMAC::SHA1) {
+  // Make sure the key is valid.
+  CHECK(ice_key.size() == kKeySize);
+
+  // Create the mask key from ice key.
+  crypto::HMAC mask_hasher(crypto::HMAC::SHA1);
+  bool ret = mask_hasher.Init(
+      reinterpret_cast<const unsigned char*>(ice_key.data()), kKeySize);
+  DCHECK(ret) << "Initialize HMAC-SHA1 for mask failed.";
+  scoped_array<uint8> mask_digest(new uint8[mask_hasher.DigestLength()]);
+  mask_hasher.Sign(kMaskSaltStr, mask_digest.get(),
+                   mask_hasher.DigestLength());
+  mask_key_.reset(crypto::SymmetricKey::Import(
+      crypto::SymmetricKey::AES,
+      std::string(mask_digest.get(), mask_digest.get() + kKeySize)));
+  DCHECK(mask_key_.get()) << "Import symmetric key failed.";
+
+  // Initialize the encryptor with mask key.
+  encryptor_.Init(mask_key_.get(), crypto::Encryptor::CTR, "");
+
+  // Create the hash key from ice key.
+  crypto::HMAC hash_hasher(crypto::HMAC::SHA1);
+  ret = hash_hasher.Init(
+      reinterpret_cast<const unsigned char*>(ice_key.data()), kKeySize);
+  DCHECK(ret) << "Initialize HMAC-SHA1 for hash failed.";
+  scoped_array<uint8> hash_key(new uint8[hash_hasher.DigestLength()]);
+  hash_hasher.Sign(kHashSaltStr, hash_key.get(), hash_hasher.DigestLength());
+
+  // Create a hasher for message.
+  ret = msg_hasher_.Init(hash_key.get(), kKeySize);
+  DCHECK(ret) << "Initialize HMAC-SHA1 for message failed.";
+}
+
+int SecureP2PSocket::Read(IOBuffer* buf, int buf_len,
+                          CompletionCallback* callback) {
+  DCHECK(!user_read_buf_);
+  DCHECK(!user_read_buf_len_);
+  DCHECK(!user_read_callback_);
+
+  user_read_buf_ = buf;
+  user_read_buf_len_ = buf_len;
+  user_read_callback_ = callback;
+  return ReadInternal();
+}
+
+int SecureP2PSocket::Write(IOBuffer* buf, int buf_len,
+                           CompletionCallback* callback) {
+  // See the spec for the steps taken in this method:
+  // http://www.whatwg.org/specs/web-apps/current-work/complete/video-conferencing-and-peer-to-peer-communication.html#peer-to-peer-connections
+  // 4. Increment sequence number by one.
+  ++write_seq_;
+
+  const int encrypted_buffer_size = kHeaderSize + buf_len;
+  scoped_refptr<net::IOBuffer> encrypted_buf =
+      new net::IOBuffer(encrypted_buffer_size);
+
+  // 6. Concatenate to form the raw message.
+  const int kRawMessageSize = kSeqNumberSize + kFrameTypeSize + buf_len;
+  std::string raw_message;
+  raw_message.resize(kRawMessageSize);
+  char* raw_message_buf = const_cast<char*>(raw_message.data());
+  SetBE64(raw_message_buf, write_seq_);
+  memcpy(raw_message_buf + kSeqNumberSize, kFrameType,
+         kFrameTypeSize);
+  memcpy(raw_message_buf + kSeqNumberSize + kFrameTypeSize,
+         buf->data(), buf_len);
+
+  // 7. Encrypt the message.
+  std::string nonce = base::RandBytesAsString(kKeySize);
+  CHECK(encryptor_.UpdateCounter(nonce));
+  std::string encrypted_message;
+  CHECK(encryptor_.Encrypt(raw_message, &encrypted_message));
+  memcpy(encrypted_buf->data() + kRawMessagePosition,
+         encrypted_message.data(), encrypted_message.size());
+
+  // 8. Concatenate nonce and encrypted message to form masked message.
+  memcpy(encrypted_buf->data() + kNoncePosition, nonce.data(), kKeySize);
+
+  // 10. Create hash from masked message with nonce.
+  scoped_array<uint8> msg_digest(new uint8[msg_hasher_.DigestLength()]);
+  msg_hasher_.Sign(
+      base::StringPiece(encrypted_buf->data() + kNoncePosition,
+                        kRawMessageSize + kKeySize),
+      msg_digest.get(), msg_hasher_.DigestLength());
+  memcpy(encrypted_buf->data() + kHashPosition, msg_digest.get(), kKeySize);
+
+  // Write to the socket.
+  int ret = socket_->Write(encrypted_buf, encrypted_buffer_size,
+                           write_callback_.get());
+  if (ret == net::ERR_IO_PENDING) {
+    DCHECK(callback);
+    user_write_callback_ = callback;
+    user_write_buf_len_ = buf_len;
+    return ret;
+  } else if (ret < 0) {
+    return ret;
+  }
+  DCHECK_EQ(buf_len + kHeaderSize, ret);
+  return buf_len;
+}
+
+bool SecureP2PSocket::SetReceiveBufferSize(int32 size) {
+  return true;
+}
+
+bool SecureP2PSocket::SetSendBufferSize(int32 size) {
+  return true;
+}
+
+int SecureP2PSocket::ReadInternal() {
+  while (true) {
+    int ret = socket_->Read(read_buf_, kReadBufferSize, read_callback_.get());
+    if (ret == net::ERR_IO_PENDING || ret < 0)
+      return ret;
+
+    ret = DecryptBuffer(ret);
+    if (ret == net::ERR_INVALID_RESPONSE)

[Sergey Ulanov, 2011/06/24 19:15:26]

nit: Add comment explaining why we retry here.

+      continue;
+
+    user_read_buf_ = NULL;
+    user_read_buf_len_ = 0;
+    user_read_callback_ = NULL;
+    return ret;
+  }
+}
+
+void SecureP2PSocket::ReadDone(int err) {
+  net::CompletionCallback* callback = user_read_callback_;
+  user_read_callback_ = NULL;
+
+  if (err < 0) {
+    user_read_buf_len_ = 0;
+    user_read_buf_ = NULL;
+    callback->Run(err);
+    return;
+  }
+
+  int ret = DecryptBuffer(err);
+  if (ret == net::ERR_INVALID_RESPONSE)
+    ret = ReadInternal();
+  if (ret == net::ERR_IO_PENDING)
+    return;
+
+  user_read_buf_ = NULL;
+  user_read_buf_len_ = 0;
+  callback->Run(ret);
+}
+
+void SecureP2PSocket::WriteDone(int err) {
+  net::CompletionCallback* callback = user_write_callback_;
+  int buf_len = user_write_buf_len_;
+
+  user_write_callback_ = NULL;
+  user_write_buf_len_ = 0;
+
+  if (err >= 0) {
+    DCHECK_EQ(buf_len + kHeaderSize, err);
+    callback->Run(buf_len);
+    return;
+  }
+  callback->Run(err);
+}
+
+int SecureP2PSocket::DecryptBuffer(int size) {
+  if (size < kRawMessagePosition)
+    return net::ERR_INVALID_RESPONSE;
+
+  // See the spec for the steps taken in this method:
+  // http://www.whatwg.org/specs/web-apps/current-work/complete/video-conferencing-and-peer-to-peer-communication.html#peer-to-peer-connections
+  // 5. Compute hash of the message.
+  scoped_array<uint8> msg_digest(new uint8[msg_hasher_.DigestLength()]);
+  msg_hasher_.Sign(
+      base::StringPiece(read_buf_->data() + kNoncePosition,
+                        size - kNoncePosition),
+      msg_digest.get(), msg_hasher_.DigestLength());
+
+  // 6. Compare the hash values.
+  int ret = memcmp(read_buf_->data(), msg_digest.get(), kKeySize);
+  if (ret)
+    return net::ERR_INVALID_RESPONSE;
+
+  // 7. Decrypt the message.
+  std::string nonce = std::string(
+      read_buf_->data() + kNoncePosition, kKeySize);
+  CHECK(encryptor_.UpdateCounter(nonce));
+  const int raw_message_size = size - kRawMessagePosition;
+
+  // TODO(hclam): Change Encryptor API to trim this memcpy.
+  std::string encrypted_message(read_buf_->data() + kRawMessagePosition,
+                                raw_message_size);
+  std::string raw_message;
+  CHECK(encryptor_.Decrypt(encrypted_message, &raw_message));
+
+  if (raw_message_size < kSeqNumberSize)
+    return net::ERR_INVALID_RESPONSE;
+
+  // 12. Read the sequence number.
+  uint64 seq_number = GetBE64(raw_message.data());
+
+  // The spec says we reject the packet if it is out of order. We don't do
+  // this so allow upper levels to do reordering.
+
+  // 14. Save the most recent sequence number.
+  read_seq_ = seq_number;
+
+  // 15. Parse the frame type.
+  if (raw_message_size < kSeqNumberSize + kFrameTypeSize)
+    return net::ERR_INVALID_RESPONSE;
+  ret = memcmp(raw_message.data() + kSeqNumberSize, kFrameType,
+               kFrameTypeSize);
+  if (ret)
+    return net::ERR_INVALID_RESPONSE;
+
+  // 16. Read the message.
+  const int kMessageSize = raw_message_size - kSeqNumberSize - kFrameTypeSize;
+  memcpy(user_read_buf_->data(),
+         raw_message.data() + kSeqNumberSize + kFrameTypeSize, kMessageSize);
+  return kMessageSize;
+}
+
+}  // namespace protocol
+}  // namespace remoting