WebSocket握手：不正确的Sec-WebSocket-Access标头值

Question

我正在用C编写一个websocket服务器，无法让握手正常工作。Chrome报告错误是由于错误的accept头，但我相信该值是正确的。

作为exchange的一个示例，客户端发送以下密钥：

Sec-WebSocket-Key: ypX0m2zum/pt80mxlVo8PA==

我的服务器会发回：

Sec-WebSocket-Accept: Kl4mnqm5QA6bBmGf3EAN0nyGXws=

我已经根据RFC中的示例测试了我的服务器，并进行了验证。我不知道为什么不被接受。我的理论是，我必须做一些其他事情，产生与坏接受值相同的错误。

以下是不同于wireshark捕获的请求：

Hypertext Transfer Protocol
    GET /websocket HTTP/1.1\r\n
    Host: 127.0.0.1:8443\r\n
    Connection: Upgrade\r\n
    Pragma: no-cache\r\n
    Cache-Control: no-cache\r\n
    User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.109 Safari/537.36\r\n
    Upgrade: websocket\r\n
    Origin: chrome-extension://eajaahbjpnhghjcdaclbkeamlkepinbl\r\n
    Sec-WebSocket-Version: 13\r\n
    Accept-Encoding: gzip, deflate, br\r\n
    Accept-Language: en-US,en;q=0.9\r\n
    Sec-WebSocket-Key: +zJ3/KI/Zrumgh+AjxopRQ==\r\n
    Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits\r\n
    \r\n
    [Full request URI: http://127.0.0.1:8443/websocket]
    [HTTP request 1/1]
    [Response in frame: 6]

以下是回应：

Hypertext Transfer Protocol
    HTTP/1.1 101 Switching Protocols\r\n
    Upgrade: websocket\r\n
    Connection: Upgrade\r\n
    Sec-WebSocket-Accept: anTEIFyI/gTepr8Q3okBj81M2/4=\r\n
    \r\n
    [HTTP response 1/1]
    [Time since request: 0.000245010 seconds]
    [Request in frame: 4]

有人能告诉我这个回答有什么问题吗？我的接受值是否不正确？

编辑1：

我用来创建响应值的代码。在此之前，会从请求中获取websocket_密钥。

    const char *magic_string = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";

    int pre_hash_size = 36 + websocket_key.size();
    char pre_hash[pre_hash_size];

    memcpy(pre_hash, websocket_key.c_str(), websocket_key.size());
    memcpy(pre_hash + websocket_key.size(), magic_string, 36);

    unique_ptr<Botan::HashFunction> hash1(Botan::HashFunction::create("SHA-1"));
    Botan::secure_vector<uint8_t> post_hash = hash1->process(reinterpret_cast<const uint8_t *>(pre_hash), pre_hash_size);

    string accept_response = base64_encode(post_hash.data(), post_hash.size());

下面是base 64函数：

/* 
   base64.cpp and base64.h
   base64 encoding and decoding with C++.
   Version: 1.01.00
   Copyright (C) 2004-2017 René Nyffenegger
   This source code is provided 'as-is', without any express or implied
   warranty. In no event will the author be held liable for any damages
   arising from the use of this software.
   Permission is granted to anyone to use this software for any purpose,
   including commercial applications, and to alter it and redistribute it
   freely, subject to the following restrictions:
   1. The origin of this source code must not be misrepresented; you must not
      claim that you wrote the original source code. If you use this source code
      in a product, an acknowledgment in the product documentation would be
      appreciated but is not required.
   2. Altered source versions must be plainly marked as such, and must not be
      misrepresented as being the original source code.
   3. This notice may not be removed or altered from any source distribution.
   René Nyffenegger [e-mail]
*/

static const std::string base64_chars =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    "abcdefghijklmnopqrstuvwxyz"
    "0123456789+/";

std::string base64_encode(unsigned char const *bytes_to_encode, unsigned int in_len)
{
  std::string ret;
  int i = 0;
  int j = 0;
  unsigned char char_array_3[3];
  unsigned char char_array_4[4];

  while (in_len--)
  {
    char_array_3[i++] = *(bytes_to_encode++);
    if (i == 3)
    {
      char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
      char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
      char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
      char_array_4[3] = char_array_3[2] & 0x3f;

      for (i = 0; (i < 4); i++)
        ret += base64_chars[char_array_4[i]];
      i = 0;
    }
  }

  if (i)
  {
    for (j = i; j < 3; j++)
      char_array_3[j] = '\0';

    char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
    char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
    char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);

    for (j = 0; (j < i + 1); j++)
      ret += base64_chars[char_array_4[j]];

    while ((i++ < 3))
      ret += '=';
  }

  return ret;
}

Answer 1

问题是，当我连接来自websocket键（由客户端发送）的pre_散列字符串和神奇字符串（常量）时，我没有考虑 size（）函数在其计数中包含的空终止符。 我在解析请求头时无意中添加了额外的空间。