Fix #1590 (#1630)

* ClientImpl: Connection=close header control moved from process_request to send_

* Connection=close header control moved from send_ to handle_request

* SSLClient::connect_with_proxy error handling improved

* to_string definition added for Error::ProxyConnection

* Comment improvement

---------

Co-authored-by: akinelden <akin.elden@gmail.com>

httplib.h

@@ -950,6 +950,7 @@ enum class Error {
   UnsupportedMultipartBoundaryChars,
   Compression,
   ConnectionTimeout,
+  ProxyConnection,
 
   // For internal use only
   SSLPeerCouldBeClosed_,
@@ -1888,6 +1889,7 @@ inline std::string to_string(const Error error) {
     return "Unsupported HTTP multipart boundary characters";
   case Error::Compression: return "Compression failed";
   case Error::ConnectionTimeout: return "Connection timed out";
+  case Error::ProxyConnection: return "Proxy connection failed";
   case Error::Unknown: return "Unknown";
   default: break;
   }
@@ -6748,6 +6750,21 @@ inline bool ClientImpl::handle_request(Stream &strm, Request &req,
 
   if (!ret) { return false; }
 
+  if (res.get_header_value("Connection") == "close" ||
+      (res.version == "HTTP/1.0" && res.reason != "Connection established")) {
+    // TODO this requires a not-entirely-obvious chain of calls to be correct
+    // for this to be safe.
+
+    // This is safe to call because handle_request is only called by send_
+    // which locks the request mutex during the process. It would be a bug
+    // to call it from a different thread since it's a thread-safety issue
+    // to do these things to the socket if another thread is using the socket.
+    std::lock_guard<std::mutex> guard(socket_mutex_);
+    shutdown_ssl(socket_, true);
+    shutdown_socket(socket_);
+    close_socket(socket_);
+  }
+
   if (300 < res.status && res.status < 400 && follow_location_) {
     req = req_save;
     ret = redirect(req, res, error);
@@ -7162,24 +7179,6 @@ inline bool ClientImpl::process_request(Stream &strm, Request &req,
     }
   }
 
-  if (res.get_header_value("Connection") == "close" ||
-      (res.version == "HTTP/1.0" && res.reason != "Connection established")) {
-    // TODO this requires a not-entirely-obvious chain of calls to be correct
-    // for this to be safe. Maybe a code refactor (such as moving this out to
-    // the send function and getting rid of the recursiveness of the mutex)
-    // could make this more obvious.
-
-    // This is safe to call because process_request is only called by
-    // handle_request which is only called by send, which locks the request
-    // mutex during the process. It would be a bug to call it from a different
-    // thread since it's a thread-safety issue to do these things to the socket
-    // if another thread is using the socket.
-    std::lock_guard<std::mutex> guard(socket_mutex_);
-    shutdown_ssl(socket_, true);
-    shutdown_socket(socket_);
-    close_socket(socket_);
-  }
-
   // Log
   if (logger_) { logger_(req, res); }
 
@@ -8287,14 +8286,14 @@ inline bool SSLClient::create_and_connect_socket(Socket &socket, Error &error) {
 inline bool SSLClient::connect_with_proxy(Socket &socket, Response &res,
                                           bool &success, Error &error) {
   success = true;
-  Response res2;
+  Response proxy_res;
   if (!detail::process_client_socket(
           socket.sock, read_timeout_sec_, read_timeout_usec_,
           write_timeout_sec_, write_timeout_usec_, [&](Stream &strm) {
             Request req2;
             req2.method = "CONNECT";
             req2.path = host_and_port_;
-            return process_request(strm, req2, res2, false, error);
+            return process_request(strm, req2, proxy_res, false, error);
           })) {
     // Thread-safe to close everything because we are assuming there are no
     // requests in flight
@@ -8305,12 +8304,12 @@ inline bool SSLClient::connect_with_proxy(Socket &socket, Response &res,
     return false;
   }
 
-  if (res2.status == 407) {
+  if (proxy_res.status == 407) {
     if (!proxy_digest_auth_username_.empty() &&
         !proxy_digest_auth_password_.empty()) {
       std::map<std::string, std::string> auth;
-      if (detail::parse_www_authenticate(res2, auth, true)) {
+      if (detail::parse_www_authenticate(proxy_res, auth, true)) {
-        Response res3;
+        proxy_res = Response();
         if (!detail::process_client_socket(
                 socket.sock, read_timeout_sec_, read_timeout_usec_,
                 write_timeout_sec_, write_timeout_usec_, [&](Stream &strm) {
@@ -8321,7 +8320,7 @@ inline bool SSLClient::connect_with_proxy(Socket &socket, Response &res,
                       req3, auth, 1, detail::random_string(10),
                       proxy_digest_auth_username_, proxy_digest_auth_password_,
                       true));
-                  return process_request(strm, req3, res3, false, error);
+                  return process_request(strm, req3, proxy_res, false, error);
                 })) {
           // Thread-safe to close everything because we are assuming there are
           // no requests in flight
@@ -8332,12 +8331,24 @@ inline bool SSLClient::connect_with_proxy(Socket &socket, Response &res,
           return false;
         }
       }
-    } else {
-      res = res2;
-      return false;
     }
   }
 
+  // If status code is not 200, proxy request is failed.
+  // Set error to ProxyConnection and return proxy response 
+  // as the response of the request
+  if (proxy_res.status != 200)
+  {
+    error = Error::ProxyConnection;
+    res = std::move(proxy_res);
+    // Thread-safe to close everything because we are assuming there are
+    // no requests in flight
+    shutdown_ssl(socket, true);
+    shutdown_socket(socket);
+    close_socket(socket);
+    return false;
+  }
+
   return true;
 }