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使用 workflow 来中转 http 请求

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本文字数： 652 阅读时长 ≈ 2 分钟

Sogou 的 workflow 是一个 C++ 编写的简单易用的 web 框架，这里我对官方的 http_proxy 做一点简单修改，来实现抓包。
通常的抓包是设置代理服务器来实现的，我这里不通过代理，而是 http_proxy 作为一个中继一样的存在。
把官方的 http_proxy 修改成下面的样子

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/*
  Copyright (c) 2019 Sogou, Inc.

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.

  Author: Xie Han (xiehan@sogou-inc.com;63350856@qq.com)
*/

#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <utility>
#include "workflow/Workflow.h"
#include "workflow/HttpMessage.h"
#include "workflow/HttpUtil.h"
#include "workflow/WFHttpServer.h"

#ifndef _WIN32
#include <unistd.h>
#endif

struct tutorial_series_context
{
	std::string url;
	WFHttpTask *proxy_task;
	bool is_keep_alive;
};

void reply_callback(WFHttpTask *proxy_task)
{
	SeriesWork *series = series_of(proxy_task);
	tutorial_series_context *context =
		(tutorial_series_context *)series->get_context();
	auto *proxy_resp = proxy_task->get_resp();
	size_t size = proxy_resp->get_output_body_size();

	if (proxy_task->get_state() == WFT_STATE_SUCCESS)
	{
		fprintf(stderr, "%s: Success. Http Status: %s, BodyLength: %zu\n",
			context->url.c_str(), proxy_resp->get_status_code(), size);
	}
	else
	{
		/* WFT_STATE_SYS_ERROR*/
		fprintf(stderr, "%s: Reply failed: %s, BodyLength: %zu\n",
			context->url.c_str(), strerror(proxy_task->get_error()), size);
	}
}

void http_callback(WFHttpTask *task)
{
	int state = task->get_state();
	int error = task->get_error();
	auto *resp = task->get_resp();
	SeriesWork *series = series_of(task);
	tutorial_series_context *context =
		(tutorial_series_context *)series->get_context();
	auto *proxy_resp = context->proxy_task->get_resp();

	/* Some servers may close the socket as the end of http response. */
	if (state == WFT_STATE_SYS_ERROR && error == ECONNRESET)
		state = WFT_STATE_SUCCESS;

	if (state == WFT_STATE_SUCCESS)
	{
		const void *body;
		size_t len;

		/* set a callback for getting reply status. */
		context->proxy_task->set_callback(reply_callback);

		/* Copy the remote webserver's response, to proxy response. */
		if (resp->get_parsed_body(&body, &len))
			resp->append_output_body_nocopy(body, len);
		*proxy_resp = std::move(*resp);
		if (!context->is_keep_alive)
			proxy_resp->set_header_pair("Connection", "close");
	}
	else
	{
		const char *err_string;
		int error = task->get_error();

		if (state == WFT_STATE_SYS_ERROR)
			err_string = strerror(error);
		else if (state == WFT_STATE_DNS_ERROR)
			err_string = gai_strerror(error);
		else if (state == WFT_STATE_SSL_ERROR)
			err_string = "SSL error";
		else /* if (state == WFT_STATE_TASK_ERROR) */
			err_string = "URL error (Cannot be a HTTPS proxy)";

		fprintf(stderr, "%s: Fetch failed. state = %d, error = %d: %s\n",
				context->url.c_str(), state, task->get_error(),
				err_string);

		/* As a tutorial, make it simple. And ignore reply status. */
		proxy_resp->set_status_code("404");
		proxy_resp->append_output_body_nocopy(
							"<html>404 Not Found.</html>", 27);
	}
}

void process(WFHttpTask *proxy_task)
{
	auto *req = proxy_task->get_req();
	SeriesWork *series = series_of(proxy_task);
	WFHttpTask *http_task; /* for requesting remote webserver. */

	tutorial_series_context *context = new tutorial_series_context;
	context->url = req->get_request_uri();
	context->proxy_task = proxy_task;

	series->set_context(context);
	series->set_callback([](const SeriesWork *series) {
		delete (tutorial_series_context *)series->get_context();
	});
	std::string requesturi = req->get_request_uri();
        
        // add begain
	protocol::HttpHeaderCursor header_cursor(req);
	std::string host;
	if (header_cursor.find("Host", host))
	{
		requesturi = "http://" + host + requesturi;
	}
	printf("uri: %s\r\n", requesturi.c_str());
        // add end

	context->is_keep_alive = req->is_keep_alive();
	http_task = WFTaskFactory::create_http_task(requesturi.c_str(), 0, 0,
												http_callback);

	const void *body;
	size_t len;

	/* Copy user's request to the new task's reuqest using std::move() */
	req->set_request_uri(http_task->get_req()->get_request_uri());
	req->get_parsed_body(&body, &len);
	req->append_output_body_nocopy(body, len);
	*http_task->get_req() = std::move(*req);

	/* also, limit the remote webserver response size. */
	http_task->get_resp()->set_size_limit(200 * 1024 * 1024);

	*series << http_task;
}

void sig_handler(int signo) { }

int main(int argc, char *argv[])
{
	unsigned short port;

	if (argc != 2)
	{
		fprintf(stderr, "USAGE: %s <port>\n", argv[0]);
		exit(1);
	}

	port = atoi(argv[1]);
	signal(SIGINT, sig_handler);

	struct WFServerParams params = HTTP_SERVER_PARAMS_DEFAULT;
	/* for safety, limit request size to 8MB. */
	params.request_size_limit = 8 * 1024 * 1024;

	WFHttpServer server(&params, process);

	if (server.start(port) == 0)
	{
#ifndef _WIN32
		pause();
#else
		getchar();
#endif
		server.stop();
	}
	else
	{
		perror("Cannot start server");
		exit(1);
	}

	return 0;
}