system-proxy/proxy_connect_job.cc - mirrors/cros/chromiumos/platform2 - Git at Google

 // Copyright 2020 The Chromium OS 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 "system-proxy/proxy_connect_job.h"

 #include <algorithm>
 #include <utility>
 #include <vector>

 #include <curl/easy.h>

 #include <base/base64.h>
 #include <base/bind.h>
 #include <base/bind_helpers.h>
 #include <base/callback_helpers.h>
 #include <base/files/file_util.h>
 #include <base/strings/stringprintf.h>
 #include <base/strings/string_util.h>
 #include <base/time/time.h>
 #include <base/threading/thread.h>
 #include <base/threading/thread_task_runner_handle.h>
 #include <brillo/http/http_transport.h>
 #include <chromeos/patchpanel/net_util.h>
 #include <chromeos/patchpanel/socket.h>
 #include <chromeos/patchpanel/socket_forwarder.h>

 #include "system-proxy/curl_socket.h"
 #include "system-proxy/http_util.h"

 // The libpatchpanel-util library overloads << for socket data structures.
 // By C++'s argument-dependent lookup rules, operators defined in a
 // different namespace are not visible. We need the using directive to make
 // the overload available this namespace.
 using patchpanel::operator<<;

 namespace {
 // There's no RFC recomandation for the max size of http request headers but
 // popular http server implementations (Apache, IIS, Tomcat) set the lower limit
 // to 8000.
 constexpr int kMaxHttpRequestHeadersSize = 8000;
 constexpr base::TimeDelta kCurlConnectTimeout =
     base::TimeDelta::FromSeconds(30);
 constexpr base::TimeDelta kWaitClientConnectTimeout =
     base::TimeDelta::FromSeconds(15);
 constexpr size_t kMaxBadRequestPrintSize = 120;

 constexpr int64_t kHttpCodeProxyAuthRequired = 407;

 // HTTP error codes and messages with origin information for debugging (RFC723,
 // section 6.1).
 const std::string_view kHttpBadRequest =
     "HTTP/1.1 400 Bad Request - Origin: local proxy\r\n\r\n";
 const std::string_view kHttpConnectionTimeout =
     "HTTP/1.1 408 Request Timeout - Origin: local proxy\r\n\r\n";
 const std::string_view kHttpInternalServerError =
     "HTTP/1.1 500 Internal Server Error - Origin: local proxy\r\n\r\n";
 const std::string_view kHttpBadGateway =
     "HTTP/1.1 502 Bad Gateway - Origin: local proxy\r\n\r\n";
 const std::string_view kHttpProxyAuthRequired =
     "HTTP/1.1 407 Credentials required - Origin: local proxy\r\n\r\n";
 constexpr char kHttpErrorTunnelFailed[] =
     "HTTP/1.1 %s Error creating tunnel - Origin: local proxy\r\n\r\n";
 }  // namespace

 namespace system_proxy {
 // CURLOPT_HEADERFUNCTION callback implementation that only returns the headers
 // from the last response sent by the sever. This is to make sure that we
 // send back valid HTTP replies and auhentication data from the HTTP messages is
 // not being leaked to the client. |userdata| is set on the libcurl CURL handle
 // used to configure the request, using the the CURLOPT_HEADERDATA option. Note,
 // from the libcurl documentation: This callback is being called for all the
 // responses received from the proxy server after intiating the connection
 // request. Multiple responses can be received in an authentication sequence.
 // Only the last response's headers should be forwarded to the System-proxy
 // client. The header callback will be called once for each header and only
 // complete header lines are passed on to the callback.
 static size_t WriteHeadersCallback(char* contents,
                                    size_t size,
                                    size_t nmemb,
                                    void* userdata) {
   std::vector<char>* vec = (std::vector<char>*)userdata;

   // Check if we are receiving a new HTTP message (after the last one was
   // terminated with an empty line).
   if (IsEndingWithHttpEmptyLine(base::StringPiece(vec->data(), vec->size()))) {
     VLOG(1) << "Removing the http reply headers from the server "
             << base::StringPiece(vec->data(), vec->size());
     vec->clear();
   }
   vec->insert(vec->end(), contents, contents + (nmemb * size));
   return size * nmemb;
 }

 // CONNECT requests may have a reply body. This method will capture the reply
 // and save it in |userdata|. |userdata| is set on the libcurl CURL handle
 // used to configure the request, using the the CURLOPT_WRITEDATA option.
 static size_t WriteCallback(char* contents,
                             size_t size,
                             size_t nmemb,
                             void* userdata) {
   std::vector<char>* vec = (std::vector<char>*)userdata;
   vec->insert(vec->end(), contents, contents + (nmemb * size));
   return size * nmemb;
 }

 ProxyConnectJob::ProxyConnectJob(
     std::unique_ptr<patchpanel::Socket> socket,
     const std::string& credentials,
     ResolveProxyCallback resolve_proxy_callback,
     AuthenticationRequiredCallback auth_required_callback,
     OnConnectionSetupFinishedCallback setup_finished_callback)
     : credentials_(credentials),
       first_http_connect_attempt_(true),
       resolve_proxy_callback_(std::move(resolve_proxy_callback)),
       auth_required_callback_(std::move(auth_required_callback)),
       setup_finished_callback_(std::move(setup_finished_callback)),
       // Safe to use |base::Unretained| because the callback will be canceled
       // when it goes out of scope.
       client_connect_timeout_callback_(base::Bind(
           &ProxyConnectJob::OnClientConnectTimeout, base::Unretained(this))) {
   client_socket_ = std::move(socket);
 }

 ProxyConnectJob::~ProxyConnectJob() = default;

 bool ProxyConnectJob::Start() {
   // Make the socket non-blocking.
   if (!base::SetNonBlocking(client_socket_->fd())) {
     PLOG(ERROR) << *this << " Failed to mark the socket as non-blocking.";
     client_socket_->SendTo(kHttpInternalServerError.data(),
                            kHttpInternalServerError.size());
     return false;
   }
   base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
       FROM_HERE, client_connect_timeout_callback_.callback(),
       kWaitClientConnectTimeout);
   read_watcher_ = base::FileDescriptorWatcher::WatchReadable(
       client_socket_->fd(), base::Bind(&ProxyConnectJob::OnClientReadReady,
                                        weak_ptr_factory_.GetWeakPtr()));
   return true;
 }

 void ProxyConnectJob::OnClientReadReady() {
   if (!read_watcher_) {
     // The connection has timed out while waiting for the client's HTTP CONNECT
     // request. See |OnClientConnectTimeout|.
     return;
   }
   client_connect_timeout_callback_.Cancel();
   // Stop watching.
   read_watcher_.reset();
   // The first message should be a HTTP CONNECT request.
   std::vector<char> connect_request;
   if (!TryReadHttpHeader(&connect_request)) {
     std::string encoded;
     base::Base64Encode(
         base::StringPiece(connect_request.data(), connect_request.size()),
         &encoded);
     LOG(ERROR) << *this
                << " Failure to read proxy CONNECT request. Base 64 encoded "
                   "request message from client: "
                << encoded;
     OnError(kHttpBadRequest);
     return;
   }
   base::StringPiece request(connect_request.data(), connect_request.size());
   target_url_ = GetUriAuthorityFromHttpHeader(request);
   if (target_url_.empty()) {
     LOG(ERROR)
         << *this
         << " Failed to extract target url from the HTTP CONNECT request.";
     OnError(kHttpBadRequest);
     return;
   }

   // The proxy resolution service in Chrome expects a proper URL, formatted as
   // scheme://host:port. It's safe to assume only https will be used for the
   // target url.
   std::move(resolve_proxy_callback_)
       .Run(base::StringPrintf("https://%s", target_url_.c_str()),
            base::Bind(&ProxyConnectJob::OnProxyResolution,
                       weak_ptr_factory_.GetWeakPtr()));
 }

 bool ProxyConnectJob::TryReadHttpHeader(std::vector<char>* raw_request) {
   size_t read_byte_count = 0;
   raw_request->resize(kMaxHttpRequestHeadersSize);

   // Read byte-by-byte and stop when reading an empty line (only CRLF) or when
   // exceeding the max buffer size.
   // TODO(acostinas, chromium:1064536) This may have some measurable performance
   // impact. We should read larger blocks of data, consume the HTTP headers,
   // cache the tunneled payload that may have already been included (e.g. TLS
   // ClientHello) and send it to server after the connection is established.
   while (read_byte_count < kMaxHttpRequestHeadersSize) {
     if (client_socket_->RecvFrom(raw_request->data() + read_byte_count, 1) <=
         0) {
       raw_request->resize(std::min(read_byte_count, kMaxBadRequestPrintSize));
       return false;
     }
     ++read_byte_count;

     if (IsEndingWithHttpEmptyLine(
             base::StringPiece(raw_request->data(), read_byte_count))) {
       raw_request->resize(read_byte_count);
       return true;
     }
   }
   return false;
 }

 void ProxyConnectJob::OnProxyResolution(
     const std::list<std::string>& proxy_servers) {
   proxy_servers_ = proxy_servers;
   DoCurlServerConnection();
 }

 void ProxyConnectJob::AuthenticationRequired(
     const std::vector<char>& http_response_headers) {
   DCHECK(!proxy_servers_.empty());
   SchemeRealmPairList scheme_realm_pairs = ParseAuthChallenge(base::StringPiece(
       http_response_headers.data(), http_response_headers.size()));
   if (scheme_realm_pairs.empty()) {
     LOG(ERROR) << "Failed to parse authentication challenge";
     OnError(kHttpBadGateway);
     return;
   }

   std::move(auth_required_callback_)
       .Run(proxy_servers_.front(), scheme_realm_pairs.front().first,
            scheme_realm_pairs.front().second,
            base::Bind(&ProxyConnectJob::OnAuthCredentialsProvided,
                       base::Unretained(this)));
 }

 void ProxyConnectJob::OnAuthCredentialsProvided(
     const std::string& credentials) {
   if (credentials.empty()) {
     SendHttpResponseToClient(/* http_response_headers= */ {},
                              /* http_response_body= */ {});
     std::move(setup_finished_callback_).Run(nullptr, this);
     return;
   }
   credentials_ = credentials;
   VLOG(1) << "Connecting to the remote server with provided credentials";
   DoCurlServerConnection();
 }

 bool ProxyConnectJob::AreAuthCredentialsRequired(CURL* easyhandle) {
   if (http_response_code_ != kHttpCodeProxyAuthRequired) {
     return false;
   }

   CURLcode res;
   int64_t server_proxy_auth_scheme = 0;
   res = curl_easy_getinfo(easyhandle, CURLINFO_PROXYAUTH_AVAIL,
                           &server_proxy_auth_scheme);
   if (res != CURLE_OK || !server_proxy_auth_scheme) {
     return false;
   }

   // If kerberos is enabled, then we need to wait for the user to request a
   // kerberos ticket from Chrome.
   return !(server_proxy_auth_scheme & CURLAUTH_NEGOTIATE);
 }

 void ProxyConnectJob::DoCurlServerConnection() {
   DCHECK(!proxy_servers_.empty());
   CURL* easyhandle = curl_easy_init();
   CURLcode res;
   curl_socket_t newSocket = -1;

   if (!easyhandle) {
     // Unfortunately it's not possible to get the failure reason.
     LOG(ERROR) << *this << " Failure to create curl handle.";
     curl_easy_cleanup(easyhandle);
     OnError(kHttpInternalServerError);
     return;
   }
   curl_easy_setopt(easyhandle, CURLOPT_URL, target_url_.c_str());
   std::vector<char> http_response_headers;
   std::vector<char> http_response_body;

   if (proxy_servers_.front().c_str() != brillo::http::kDirectProxy) {
     curl_easy_setopt(easyhandle, CURLOPT_PROXY, proxy_servers_.front().c_str());
     curl_easy_setopt(easyhandle, CURLOPT_HTTPPROXYTUNNEL, 1L);
     curl_easy_setopt(easyhandle, CURLOPT_CONNECT_ONLY, 1);
     // Allow libcurl to pick authentication method. Curl will use the most
     // secure one the remote site claims to support.
     curl_easy_setopt(easyhandle, CURLOPT_PROXYAUTH, CURLAUTH_ANY);
     curl_easy_setopt(easyhandle, CURLOPT_PROXYUSERPWD, credentials_.c_str());
   }
   curl_easy_setopt(easyhandle, CURLOPT_CONNECTTIMEOUT_MS,
                    kCurlConnectTimeout.InMilliseconds());
   curl_easy_setopt(easyhandle, CURLOPT_HEADERFUNCTION, WriteHeadersCallback);
   curl_easy_setopt(easyhandle, CURLOPT_HEADERDATA, &http_response_headers);
   curl_easy_setopt(easyhandle, CURLOPT_WRITEFUNCTION, WriteCallback);
   curl_easy_setopt(easyhandle, CURLOPT_WRITEDATA, &http_response_body);

   res = curl_easy_perform(easyhandle);
   curl_easy_getinfo(easyhandle, CURLINFO_HTTP_CONNECTCODE,
                     &http_response_code_);

   if (res != CURLE_OK) {
     LOG(ERROR) << *this << " curl_easy_perform() failed with error: "
                << curl_easy_strerror(res);
     if (first_http_connect_attempt_ && AreAuthCredentialsRequired(easyhandle)) {
       first_http_connect_attempt_ = false;
       AuthenticationRequired(http_response_headers);
       curl_easy_cleanup(easyhandle);
       return;
     }
     curl_easy_cleanup(easyhandle);

     SendHttpResponseToClient(/* http_response_headers= */ {},
                              /* http_response_body= */ {});
     std::move(setup_finished_callback_).Run(nullptr, this);
     return;
   }
   // Extract the socket from the curl handle.
   res = curl_easy_getinfo(easyhandle, CURLINFO_ACTIVESOCKET, &newSocket);
   if (res != CURLE_OK) {
     LOG(ERROR) << *this << " Failed to get socket from curl with error: "
                << curl_easy_strerror(res);
     curl_easy_cleanup(easyhandle);
     OnError(kHttpBadGateway);
     return;
   }

   ScopedCurlEasyhandle scoped_handle(easyhandle, FreeCurlEasyhandle());
   auto server_conn = std::make_unique<CurlSocket>(base::ScopedFD(newSocket),
                                                   std::move(scoped_handle));

   // Send the server reply to the client. If the connection is successful, the
   // reply headers should be "HTTP/1.1 200 Connection Established".
   if (!SendHttpResponseToClient(http_response_headers, http_response_body)) {
     std::move(setup_finished_callback_).Run(nullptr, this);
     return;
   }

   auto fwd = std::make_unique<patchpanel::SocketForwarder>(
       base::StringPrintf("%d-%d", client_socket_->fd(), server_conn->fd()),
       std::move(client_socket_), std::move(server_conn));
   // Start forwarding data between sockets.
   fwd->Start();
   std::move(setup_finished_callback_).Run(std::move(fwd), this);
 }

 bool ProxyConnectJob::SendHttpResponseToClient(
     const std::vector<char>& http_response_headers,
     const std::vector<char>& http_response_body) {
   if (http_response_code_ == 0) {
     // No HTTP CONNECT response code is available.
     return client_socket_->SendTo(kHttpInternalServerError.data(),
                                   kHttpInternalServerError.size());
   }

   if (http_response_code_ == kHttpCodeProxyAuthRequired) {
     // This will be a hint for the user to authenticate via the Browser or
     // acquire a Kerberos ticket.
     return client_socket_->SendTo(kHttpProxyAuthRequired.data(),
                                   kHttpProxyAuthRequired.size());
   }

   if (http_response_code_ >= 400) {
     VLOG(1) << "Failed to set up HTTP tunnel with code " << http_response_code_;
     std::string http_error = base::StringPrintf(
         kHttpErrorTunnelFailed, std::to_string(http_response_code_).c_str());
     return client_socket_->SendTo(http_error.c_str(), http_error.size());
   }

   if (http_response_headers.empty()) {
     return client_socket_->SendTo(kHttpInternalServerError.data(),
                                   kHttpInternalServerError.size());
   }

   VLOG(1) << "Sending server reply to client";
   if (!client_socket_->SendTo(http_response_headers.data(),
                               http_response_headers.size())) {
     PLOG(ERROR) << "Failed to send HTTP server response headers to client";
     return false;
   }
   if (!http_response_body.empty()) {
     if (!client_socket_->SendTo(http_response_body.data(),
                                 http_response_body.size())) {
       PLOG(ERROR) << "Failed to send HTTP server response payload to client";
       return false;
     }
   }
   return true;
 }

 void ProxyConnectJob::OnError(const std::string_view& http_error_message) {
   client_socket_->SendTo(http_error_message.data(), http_error_message.size());
   std::move(setup_finished_callback_).Run(nullptr, this);
 }

 void ProxyConnectJob::OnClientConnectTimeout() {
   // Stop listening for client connect requests.
   read_watcher_.reset();
   LOG(ERROR) << *this
              << " Connection timed out while waiting for the client to send a "
                 "connect request.";
   OnError(kHttpConnectionTimeout);
 }

 std::ostream& operator<<(std::ostream& stream, const ProxyConnectJob& job) {
   stream << "{fd: " << job.client_socket_->fd();
   if (!job.target_url_.empty()) {
     stream << ", url: " << job.target_url_;
   }
   stream << "}";
   return stream;
 }

 }  // namespace system_proxy
	// Copyright 2020 The Chromium OS 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 "system-proxy/proxy_connect_job.h"

	#include <algorithm>
	#include <utility>
	#include <vector>

	#include <curl/easy.h>

	#include <base/base64.h>
	#include <base/bind.h>
	#include <base/bind_helpers.h>
	#include <base/callback_helpers.h>
	#include <base/files/file_util.h>
	#include <base/strings/stringprintf.h>
	#include <base/strings/string_util.h>
	#include <base/time/time.h>
	#include <base/threading/thread.h>
	#include <base/threading/thread_task_runner_handle.h>
	#include <brillo/http/http_transport.h>
	#include <chromeos/patchpanel/net_util.h>
	#include <chromeos/patchpanel/socket.h>
	#include <chromeos/patchpanel/socket_forwarder.h>

	#include "system-proxy/curl_socket.h"
	#include "system-proxy/http_util.h"

	// The libpatchpanel-util library overloads << for socket data structures.
	// By C++'s argument-dependent lookup rules, operators defined in a
	// different namespace are not visible. We need the using directive to make
	// the overload available this namespace.
	using patchpanel::operator<<;

	namespace {
	// There's no RFC recomandation for the max size of http request headers but
	// popular http server implementations (Apache, IIS, Tomcat) set the lower limit
	// to 8000.
	constexpr int kMaxHttpRequestHeadersSize = 8000;
	constexpr base::TimeDelta kCurlConnectTimeout =
	base::TimeDelta::FromSeconds(30);
	constexpr base::TimeDelta kWaitClientConnectTimeout =
	base::TimeDelta::FromSeconds(15);
	constexpr size_t kMaxBadRequestPrintSize = 120;

	constexpr int64_t kHttpCodeProxyAuthRequired = 407;

	// HTTP error codes and messages with origin information for debugging (RFC723,
	// section 6.1).
	const std::string_view kHttpBadRequest =
	"HTTP/1.1 400 Bad Request - Origin: local proxy\r\n\r\n";
	const std::string_view kHttpConnectionTimeout =
	"HTTP/1.1 408 Request Timeout - Origin: local proxy\r\n\r\n";
	const std::string_view kHttpInternalServerError =
	"HTTP/1.1 500 Internal Server Error - Origin: local proxy\r\n\r\n";
	const std::string_view kHttpBadGateway =
	"HTTP/1.1 502 Bad Gateway - Origin: local proxy\r\n\r\n";
	const std::string_view kHttpProxyAuthRequired =
	"HTTP/1.1 407 Credentials required - Origin: local proxy\r\n\r\n";
	constexpr char kHttpErrorTunnelFailed[] =
	"HTTP/1.1 %s Error creating tunnel - Origin: local proxy\r\n\r\n";
	} // namespace

	namespace system_proxy {
	// CURLOPT_HEADERFUNCTION callback implementation that only returns the headers
	// from the last response sent by the sever. This is to make sure that we
	// send back valid HTTP replies and auhentication data from the HTTP messages is
	// not being leaked to the client. \|userdata\| is set on the libcurl CURL handle
	// used to configure the request, using the the CURLOPT_HEADERDATA option. Note,
	// from the libcurl documentation: This callback is being called for all the
	// responses received from the proxy server after intiating the connection
	// request. Multiple responses can be received in an authentication sequence.
	// Only the last response's headers should be forwarded to the System-proxy
	// client. The header callback will be called once for each header and only
	// complete header lines are passed on to the callback.
	static size_t WriteHeadersCallback(char* contents,
	size_t size,
	size_t nmemb,
	void* userdata) {
	std::vector<char>* vec = (std::vector<char>*)userdata;

	// Check if we are receiving a new HTTP message (after the last one was
	// terminated with an empty line).
	if (IsEndingWithHttpEmptyLine(base::StringPiece(vec->data(), vec->size()))) {
	VLOG(1) << "Removing the http reply headers from the server "
	<< base::StringPiece(vec->data(), vec->size());
	vec->clear();
	}
	vec->insert(vec->end(), contents, contents + (nmemb * size));
	return size * nmemb;
	}

	// CONNECT requests may have a reply body. This method will capture the reply
	// and save it in \|userdata\|. \|userdata\| is set on the libcurl CURL handle
	// used to configure the request, using the the CURLOPT_WRITEDATA option.
	static size_t WriteCallback(char* contents,
	size_t size,
	size_t nmemb,
	void* userdata) {
	std::vector<char>* vec = (std::vector<char>*)userdata;
	vec->insert(vec->end(), contents, contents + (nmemb * size));
	return size * nmemb;
	}

	ProxyConnectJob::ProxyConnectJob(
	std::unique_ptr<patchpanel::Socket> socket,
	const std::string& credentials,
	ResolveProxyCallback resolve_proxy_callback,
	AuthenticationRequiredCallback auth_required_callback,
	OnConnectionSetupFinishedCallback setup_finished_callback)
	: credentials_(credentials),
	first_http_connect_attempt_(true),
	resolve_proxy_callback_(std::move(resolve_proxy_callback)),
	auth_required_callback_(std::move(auth_required_callback)),
	setup_finished_callback_(std::move(setup_finished_callback)),
	// Safe to use \|base::Unretained\| because the callback will be canceled
	// when it goes out of scope.
	client_connect_timeout_callback_(base::Bind(
	&ProxyConnectJob::OnClientConnectTimeout, base::Unretained(this))) {
	client_socket_ = std::move(socket);
	}

	ProxyConnectJob::~ProxyConnectJob() = default;

	bool ProxyConnectJob::Start() {
	// Make the socket non-blocking.
	if (!base::SetNonBlocking(client_socket_->fd())) {
	PLOG(ERROR) << *this << " Failed to mark the socket as non-blocking.";
	client_socket_->SendTo(kHttpInternalServerError.data(),
	kHttpInternalServerError.size());
	return false;
	}
	base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
	FROM_HERE, client_connect_timeout_callback_.callback(),
	kWaitClientConnectTimeout);
	read_watcher_ = base::FileDescriptorWatcher::WatchReadable(
	client_socket_->fd(), base::Bind(&ProxyConnectJob::OnClientReadReady,
	weak_ptr_factory_.GetWeakPtr()));
	return true;
	}

	void ProxyConnectJob::OnClientReadReady() {
	if (!read_watcher_) {
	// The connection has timed out while waiting for the client's HTTP CONNECT
	// request. See \|OnClientConnectTimeout\|.
	return;
	}
	client_connect_timeout_callback_.Cancel();
	// Stop watching.
	read_watcher_.reset();
	// The first message should be a HTTP CONNECT request.
	std::vector<char> connect_request;
	if (!TryReadHttpHeader(&connect_request)) {
	std::string encoded;
	base::Base64Encode(
	base::StringPiece(connect_request.data(), connect_request.size()),
	&encoded);
	LOG(ERROR) << *this
	<< " Failure to read proxy CONNECT request. Base 64 encoded "
	"request message from client: "
	<< encoded;
	OnError(kHttpBadRequest);
	return;
	}
	base::StringPiece request(connect_request.data(), connect_request.size());
	target_url_ = GetUriAuthorityFromHttpHeader(request);
	if (target_url_.empty()) {
	LOG(ERROR)
	<< *this
	<< " Failed to extract target url from the HTTP CONNECT request.";
	OnError(kHttpBadRequest);
	return;
	}

	// The proxy resolution service in Chrome expects a proper URL, formatted as
	// scheme://host:port. It's safe to assume only https will be used for the
	// target url.
	std::move(resolve_proxy_callback_)
	.Run(base::StringPrintf("https://%s", target_url_.c_str()),
	base::Bind(&ProxyConnectJob::OnProxyResolution,
	weak_ptr_factory_.GetWeakPtr()));
	}

	bool ProxyConnectJob::TryReadHttpHeader(std::vector<char>* raw_request) {
	size_t read_byte_count = 0;
	raw_request->resize(kMaxHttpRequestHeadersSize);

	// Read byte-by-byte and stop when reading an empty line (only CRLF) or when
	// exceeding the max buffer size.
	// TODO(acostinas, chromium:1064536) This may have some measurable performance
	// impact. We should read larger blocks of data, consume the HTTP headers,
	// cache the tunneled payload that may have already been included (e.g. TLS
	// ClientHello) and send it to server after the connection is established.
	while (read_byte_count < kMaxHttpRequestHeadersSize) {
	if (client_socket_->RecvFrom(raw_request->data() + read_byte_count, 1) <=
	0) {
	raw_request->resize(std::min(read_byte_count, kMaxBadRequestPrintSize));
	return false;
	}
	++read_byte_count;

	if (IsEndingWithHttpEmptyLine(
	base::StringPiece(raw_request->data(), read_byte_count))) {
	raw_request->resize(read_byte_count);
	return true;
	}
	}
	return false;
	}

	void ProxyConnectJob::OnProxyResolution(
	const std::list<std::string>& proxy_servers) {
	proxy_servers_ = proxy_servers;
	DoCurlServerConnection();
	}

	void ProxyConnectJob::AuthenticationRequired(
	const std::vector<char>& http_response_headers) {
	DCHECK(!proxy_servers_.empty());
	SchemeRealmPairList scheme_realm_pairs = ParseAuthChallenge(base::StringPiece(
	http_response_headers.data(), http_response_headers.size()));
	if (scheme_realm_pairs.empty()) {
	LOG(ERROR) << "Failed to parse authentication challenge";
	OnError(kHttpBadGateway);
	return;
	}

	std::move(auth_required_callback_)
	.Run(proxy_servers_.front(), scheme_realm_pairs.front().first,
	scheme_realm_pairs.front().second,
	base::Bind(&ProxyConnectJob::OnAuthCredentialsProvided,
	base::Unretained(this)));
	}

	void ProxyConnectJob::OnAuthCredentialsProvided(
	const std::string& credentials) {
	if (credentials.empty()) {
	SendHttpResponseToClient(/* http_response_headers= */ {},
	/* http_response_body= */ {});
	std::move(setup_finished_callback_).Run(nullptr, this);
	return;
	}
	credentials_ = credentials;
	VLOG(1) << "Connecting to the remote server with provided credentials";
	DoCurlServerConnection();
	}

	bool ProxyConnectJob::AreAuthCredentialsRequired(CURL* easyhandle) {
	if (http_response_code_ != kHttpCodeProxyAuthRequired) {
	return false;
	}

	CURLcode res;
	int64_t server_proxy_auth_scheme = 0;
	res = curl_easy_getinfo(easyhandle, CURLINFO_PROXYAUTH_AVAIL,
	&server_proxy_auth_scheme);
	if (res != CURLE_OK \|\| !server_proxy_auth_scheme) {
	return false;
	}

	// If kerberos is enabled, then we need to wait for the user to request a
	// kerberos ticket from Chrome.
	return !(server_proxy_auth_scheme & CURLAUTH_NEGOTIATE);
	}

	void ProxyConnectJob::DoCurlServerConnection() {
	DCHECK(!proxy_servers_.empty());
	CURL* easyhandle = curl_easy_init();
	CURLcode res;
	curl_socket_t newSocket = -1;

	if (!easyhandle) {
	// Unfortunately it's not possible to get the failure reason.
	LOG(ERROR) << *this << " Failure to create curl handle.";
	curl_easy_cleanup(easyhandle);
	OnError(kHttpInternalServerError);
	return;
	}
	curl_easy_setopt(easyhandle, CURLOPT_URL, target_url_.c_str());
	std::vector<char> http_response_headers;
	std::vector<char> http_response_body;

	if (proxy_servers_.front().c_str() != brillo::http::kDirectProxy) {
	curl_easy_setopt(easyhandle, CURLOPT_PROXY, proxy_servers_.front().c_str());
	curl_easy_setopt(easyhandle, CURLOPT_HTTPPROXYTUNNEL, 1L);
	curl_easy_setopt(easyhandle, CURLOPT_CONNECT_ONLY, 1);
	// Allow libcurl to pick authentication method. Curl will use the most
	// secure one the remote site claims to support.
	curl_easy_setopt(easyhandle, CURLOPT_PROXYAUTH, CURLAUTH_ANY);
	curl_easy_setopt(easyhandle, CURLOPT_PROXYUSERPWD, credentials_.c_str());
	}
	curl_easy_setopt(easyhandle, CURLOPT_CONNECTTIMEOUT_MS,
	kCurlConnectTimeout.InMilliseconds());
	curl_easy_setopt(easyhandle, CURLOPT_HEADERFUNCTION, WriteHeadersCallback);
	curl_easy_setopt(easyhandle, CURLOPT_HEADERDATA, &http_response_headers);
	curl_easy_setopt(easyhandle, CURLOPT_WRITEFUNCTION, WriteCallback);
	curl_easy_setopt(easyhandle, CURLOPT_WRITEDATA, &http_response_body);

	res = curl_easy_perform(easyhandle);
	curl_easy_getinfo(easyhandle, CURLINFO_HTTP_CONNECTCODE,
	&http_response_code_);

	if (res != CURLE_OK) {
	LOG(ERROR) << *this << " curl_easy_perform() failed with error: "
	<< curl_easy_strerror(res);
	if (first_http_connect_attempt_ && AreAuthCredentialsRequired(easyhandle)) {
	first_http_connect_attempt_ = false;
	AuthenticationRequired(http_response_headers);
	curl_easy_cleanup(easyhandle);
	return;
	}
	curl_easy_cleanup(easyhandle);

	SendHttpResponseToClient(/* http_response_headers= */ {},
	/* http_response_body= */ {});
	std::move(setup_finished_callback_).Run(nullptr, this);
	return;
	}
	// Extract the socket from the curl handle.
	res = curl_easy_getinfo(easyhandle, CURLINFO_ACTIVESOCKET, &newSocket);
	if (res != CURLE_OK) {
	LOG(ERROR) << *this << " Failed to get socket from curl with error: "
	<< curl_easy_strerror(res);
	curl_easy_cleanup(easyhandle);
	OnError(kHttpBadGateway);
	return;
	}

	ScopedCurlEasyhandle scoped_handle(easyhandle, FreeCurlEasyhandle());
	auto server_conn = std::make_unique<CurlSocket>(base::ScopedFD(newSocket),
	std::move(scoped_handle));

	// Send the server reply to the client. If the connection is successful, the
	// reply headers should be "HTTP/1.1 200 Connection Established".
	if (!SendHttpResponseToClient(http_response_headers, http_response_body)) {
	std::move(setup_finished_callback_).Run(nullptr, this);
	return;
	}

	auto fwd = std::make_unique<patchpanel::SocketForwarder>(
	base::StringPrintf("%d-%d", client_socket_->fd(), server_conn->fd()),
	std::move(client_socket_), std::move(server_conn));
	// Start forwarding data between sockets.
	fwd->Start();
	std::move(setup_finished_callback_).Run(std::move(fwd), this);
	}

	bool ProxyConnectJob::SendHttpResponseToClient(
	const std::vector<char>& http_response_headers,
	const std::vector<char>& http_response_body) {
	if (http_response_code_ == 0) {
	// No HTTP CONNECT response code is available.
	return client_socket_->SendTo(kHttpInternalServerError.data(),
	kHttpInternalServerError.size());
	}

	if (http_response_code_ == kHttpCodeProxyAuthRequired) {
	// This will be a hint for the user to authenticate via the Browser or
	// acquire a Kerberos ticket.
	return client_socket_->SendTo(kHttpProxyAuthRequired.data(),
	kHttpProxyAuthRequired.size());
	}

	if (http_response_code_ >= 400) {
	VLOG(1) << "Failed to set up HTTP tunnel with code " << http_response_code_;
	std::string http_error = base::StringPrintf(
	kHttpErrorTunnelFailed, std::to_string(http_response_code_).c_str());
	return client_socket_->SendTo(http_error.c_str(), http_error.size());
	}

	if (http_response_headers.empty()) {
	return client_socket_->SendTo(kHttpInternalServerError.data(),
	kHttpInternalServerError.size());
	}

	VLOG(1) << "Sending server reply to client";
	if (!client_socket_->SendTo(http_response_headers.data(),
	http_response_headers.size())) {
	PLOG(ERROR) << "Failed to send HTTP server response headers to client";
	return false;
	}
	if (!http_response_body.empty()) {
	if (!client_socket_->SendTo(http_response_body.data(),
	http_response_body.size())) {
	PLOG(ERROR) << "Failed to send HTTP server response payload to client";
	return false;
	}
	}
	return true;
	}

	void ProxyConnectJob::OnError(const std::string_view& http_error_message) {
	client_socket_->SendTo(http_error_message.data(), http_error_message.size());
	std::move(setup_finished_callback_).Run(nullptr, this);
	}

	void ProxyConnectJob::OnClientConnectTimeout() {
	// Stop listening for client connect requests.
	read_watcher_.reset();
	LOG(ERROR) << *this
	<< " Connection timed out while waiting for the client to send a "
	"connect request.";
	OnError(kHttpConnectionTimeout);
	}

	std::ostream& operator<<(std::ostream& stream, const ProxyConnectJob& job) {
	stream << "{fd: " << job.client_socket_->fd();
	if (!job.target_url_.empty()) {
	stream << ", url: " << job.target_url_;
	}
	stream << "}";
	return stream;
	}

	} // namespace system_proxy