// 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 "net/server/web_socket.h"

#include "base/base64.h"
#include "base/rand_util.h"
#include "base/logging.h"
#include "base/md5.h"
#include "base/sha1.h"
#include "base/string_number_conversions.h"
#include "base/stringprintf.h"
#include "net/server/http_connection.h"
#include "net/server/http_server_request_info.h"

#if defined(OS_WIN)
#include <winsock2.h>
#else
#include <arpa/inet.h>
#endif

#include <limits>

namespace net {

namespace {

static uint32 WebSocketKeyFingerprint(const std::string& str) {
  std::string result;
  const char* p_char = str.c_str();
  int length = str.length();
  int spaces = 0;
  for (int i = 0; i < length; ++i) {
    if (p_char[i] >= '0' && p_char[i] <= '9')
      result.append(&p_char[i], 1);
    else if (p_char[i] == ' ')
      spaces++;
  }
  if (spaces == 0)
    return 0;
  int64 number = 0;
  if (!base::StringToInt64(result, &number))
    return 0;
  return htonl(static_cast<uint32>(number / spaces));
}

class WebSocketHixie76 : public net::WebSocket {
 public:
  static net::WebSocket* Create(HttpConnection* connection,
                                const HttpServerRequestInfo& request,
                                size_t* pos) {
    if (connection->recv_data().length() < *pos + kWebSocketHandshakeBodyLen)
      return NULL;
    return new WebSocketHixie76(connection, request, pos);
  }

  virtual void Accept(const HttpServerRequestInfo& request) {
    std::string key1 = request.GetHeaderValue("Sec-WebSocket-Key1");
    std::string key2 = request.GetHeaderValue("Sec-WebSocket-Key2");

    uint32 fp1 = WebSocketKeyFingerprint(key1);
    uint32 fp2 = WebSocketKeyFingerprint(key2);

    char data[16];
    memcpy(data, &fp1, 4);
    memcpy(data + 4, &fp2, 4);
    memcpy(data + 8, &key3_[0], 8);

    base::MD5Digest digest;
    base::MD5Sum(data, 16, &digest);

    std::string origin = request.GetHeaderValue("Origin");
    std::string host = request.GetHeaderValue("Host");
    std::string location = "ws://" + host + request.path;
    connection_->Send(base::StringPrintf(
        "HTTP/1.1 101 WebSocket Protocol Handshake\r\n"
        "Upgrade: WebSocket\r\n"
        "Connection: Upgrade\r\n"
        "Sec-WebSocket-Origin: %s\r\n"
        "Sec-WebSocket-Location: %s\r\n"
        "\r\n",
        origin.c_str(),
        location.c_str()));
    connection_->Send(reinterpret_cast<char*>(digest.a), 16);
  }

  virtual ParseResult Read(std::string* message) {
    DCHECK(message);
    const std::string& data = connection_->recv_data();
    if (data[0])
      return FRAME_ERROR;

    size_t pos = data.find('\377', 1);
    if (pos == std::string::npos)
      return FRAME_INCOMPLETE;

    std::string buffer(data.begin() + 1, data.begin() + pos);
    message->swap(buffer);
    connection_->Shift(pos + 1);

    return FRAME_OK;
  }

  virtual void Send(const std::string& message) {
    char message_start = 0;
    char message_end = -1;
    connection_->Send(&message_start, 1);
    connection_->Send(message);
    connection_->Send(&message_end, 1);
  }

 private:
  static const int kWebSocketHandshakeBodyLen;

  WebSocketHixie76(HttpConnection* connection,
                   const HttpServerRequestInfo& request,
                   size_t* pos) : WebSocket(connection) {
    std::string key1 = request.GetHeaderValue("Sec-WebSocket-Key1");
    std::string key2 = request.GetHeaderValue("Sec-WebSocket-Key2");

    if (key1.empty()) {
      connection->Send500("Invalid request format. "
                          "Sec-WebSocket-Key1 is empty or isn't specified.");
      return;
    }

    if (key2.empty()) {
      connection->Send500("Invalid request format. "
                          "Sec-WebSocket-Key2 is empty or isn't specified.");
      return;
    }

    key3_ = connection->recv_data().substr(
        *pos,
        *pos + kWebSocketHandshakeBodyLen);
    *pos += kWebSocketHandshakeBodyLen;
  }

  std::string key3_;

  DISALLOW_COPY_AND_ASSIGN(WebSocketHixie76);
};

const int WebSocketHixie76::kWebSocketHandshakeBodyLen = 8;


// Constants for hybi-10 frame format.

typedef int OpCode;

const OpCode kOpCodeContinuation = 0x0;
const OpCode kOpCodeText = 0x1;
const OpCode kOpCodeBinary = 0x2;
const OpCode kOpCodeClose = 0x8;
const OpCode kOpCodePing = 0x9;
const OpCode kOpCodePong = 0xA;

const unsigned char kFinalBit = 0x80;
const unsigned char kReserved1Bit = 0x40;
const unsigned char kReserved2Bit = 0x20;
const unsigned char kReserved3Bit = 0x10;
const unsigned char kOpCodeMask = 0xF;
const unsigned char kMaskBit = 0x80;
const unsigned char kPayloadLengthMask = 0x7F;

const size_t kMaxSingleBytePayloadLength = 125;
const size_t kTwoBytePayloadLengthField = 126;
const size_t kEightBytePayloadLengthField = 127;
const size_t kMaskingKeyWidthInBytes = 4;

class WebSocketHybi10 : public WebSocket {
 public:
  static WebSocket* Create(HttpConnection* connection,
                           const HttpServerRequestInfo& request,
                           size_t* pos) {
    std::string version = request.GetHeaderValue("Sec-WebSocket-Version");
    if (version != "8")
      return NULL;

    std::string key = request.GetHeaderValue("Sec-WebSocket-Key");
    if (key.empty()) {
      connection->Send500("Invalid request format. "
              "Sec-WebSocket-Key is empty or isn't specified.");
      return NULL;
    }
    return new WebSocketHybi10(connection, request, pos);
  }

  virtual void Accept(const HttpServerRequestInfo& request) {
    static const char* const kWebSocketGuid =
        "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
    std::string key = request.GetHeaderValue("Sec-WebSocket-Key");
    std::string data = base::StringPrintf("%s%s", key.c_str(), kWebSocketGuid);
    std::string encoded_hash;
    base::Base64Encode(base::SHA1HashString(data), &encoded_hash);

    std::string response = base::StringPrintf(
        "HTTP/1.1 101 WebSocket Protocol Handshake\r\n"
        "Upgrade: WebSocket\r\n"
        "Connection: Upgrade\r\n"
        "Sec-WebSocket-Accept: %s\r\n"
        "\r\n",
        encoded_hash.c_str());
    connection_->Send(response);
  }

  virtual ParseResult Read(std::string* message) {
    size_t data_length = connection_->recv_data().length();
    if (data_length < 2)
      return FRAME_INCOMPLETE;

    const char* p = connection_->recv_data().c_str();
    const char* buffer_end = p + data_length;

    unsigned char first_byte = *p++;
    unsigned char second_byte = *p++;

    final_ = first_byte & kFinalBit;
    reserved1_ = first_byte & kReserved1Bit;
    reserved2_ = first_byte & kReserved2Bit;
    reserved3_ = first_byte & kReserved3Bit;
    op_code_ = first_byte & kOpCodeMask;
    masked_ = second_byte & kMaskBit;

    CHECK_EQ(kOpCodeText, op_code_);

    uint64 payload_length64 = second_byte & kPayloadLengthMask;
    if (payload_length64 > kMaxSingleBytePayloadLength) {
      int extended_payload_length_size;
      if (payload_length64 == kTwoBytePayloadLengthField)
        extended_payload_length_size = 2;
      else {
        DCHECK(payload_length64 == kEightBytePayloadLengthField);
        extended_payload_length_size = 8;
      }
      if (buffer_end - p < extended_payload_length_size)
        return FRAME_INCOMPLETE;
      payload_length64 = 0;
      for (int i = 0; i < extended_payload_length_size; ++i) {
        payload_length64 <<= 8;
        payload_length64 |= static_cast<unsigned char>(*p++);
      }
    }

    static const uint64 max_payload_length = 0x7FFFFFFFFFFFFFFFull;
    size_t masking_key_length = masked_ ? kMaskingKeyWidthInBytes : 0;
    static size_t max_length = std::numeric_limits<size_t>::max();
    if (payload_length64 > max_payload_length ||
        payload_length64 + masking_key_length > max_length) {
      // WebSocket frame length too large.
      return FRAME_ERROR;
    }
    payload_length_ = static_cast<size_t>(payload_length64);

    size_t total_length = masking_key_length + payload_length_;
    if (static_cast<size_t>(buffer_end - p) < total_length)
      return FRAME_INCOMPLETE;

    if (masked_) {
      message->resize(payload_length_);
      const char* masking_key = p;
      char* payload = const_cast<char*>(p + kMaskingKeyWidthInBytes);
      for (size_t i = 0; i < payload_length_; ++i)  // Unmask the payload.
        (*message)[i] = payload[i] ^ masking_key[i % kMaskingKeyWidthInBytes];
    } else {
      std::string buffer(p, p + payload_length_);
      message->swap(buffer);
    }

    size_t pos = p + masking_key_length + payload_length_ -
        connection_->recv_data().c_str();
    connection_->Shift(pos);
    return FRAME_OK;
  }

  virtual void Send(const std::string& message) {
    std::vector<char> frame;
    OpCode op_code = kOpCodeText;
    size_t data_length = message.length();

    frame.push_back(kFinalBit | op_code);
    if (data_length <= kMaxSingleBytePayloadLength)
      frame.push_back(kMaskBit | data_length);
    else if (data_length <= 0xFFFF) {
      frame.push_back(kMaskBit | kTwoBytePayloadLengthField);
      frame.push_back((data_length & 0xFF00) >> 8);
      frame.push_back(data_length & 0xFF);
    } else {
      frame.push_back(kMaskBit | kEightBytePayloadLengthField);
      char extended_payload_length[8];
      size_t remaining = data_length;
      // Fill the length into extended_payload_length in the network byte order.
      for (int i = 0; i < 8; ++i) {
        extended_payload_length[7 - i] = remaining & 0xFF;
        remaining >>= 8;
      }
      frame.insert(frame.end(),
                   extended_payload_length,
                   extended_payload_length + 8);
      DCHECK(!remaining);
    }

    // Mask the frame.
    size_t masking_key_start = frame.size();
    // Add placeholder for masking key. Will be overwritten.
    frame.resize(frame.size() + kMaskingKeyWidthInBytes);
    size_t payload_start = frame.size();
    const char* data = message.c_str();
    frame.insert(frame.end(), data, data + data_length);

    base::RandBytes(&frame[0] + masking_key_start,
                    kMaskingKeyWidthInBytes);
    for (size_t i = 0; i < data_length; ++i) {
      frame[payload_start + i] ^=
          frame[masking_key_start + i % kMaskingKeyWidthInBytes];
    }
    connection_->Send(&frame[0], frame.size());
  }

 private:
  WebSocketHybi10(HttpConnection* connection,
                  const HttpServerRequestInfo& request,
                  size_t* pos)
    : WebSocket(connection),
      op_code_(0),
      final_(false),
      reserved1_(false),
      reserved2_(false),
      reserved3_(false),
      masked_(false),
      payload_(0),
      payload_length_(0),
      frame_end_(0) {
  }

  OpCode op_code_;
  bool final_;
  bool reserved1_;
  bool reserved2_;
  bool reserved3_;
  bool masked_;
  const char* payload_;
  size_t payload_length_;
  const char* frame_end_;

  DISALLOW_COPY_AND_ASSIGN(WebSocketHybi10);
};

}  // anonymous namespace

WebSocket* WebSocket::CreateWebSocket(HttpConnection* connection,
                                      const HttpServerRequestInfo& request,
                                      size_t* pos) {
  WebSocket* socket = WebSocketHybi10::Create(connection, request, pos);
  if (socket)
    return socket;

  return WebSocketHixie76::Create(connection, request, pos);
}

WebSocket::WebSocket(HttpConnection* connection) : connection_(connection) {
}

}  // namespace net