1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker and Matt Lilley
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2015, University of Amsterdam
    7                         VU University Amsterdam
    8    All rights reserved.
    9
   10    Redistribution and use in source and binary forms, with or without
   11    modification, are permitted provided that the following conditions
   12    are met:
   13
   14    1. Redistributions of source code must retain the above copyright
   15       notice, this list of conditions and the following disclaimer.
   16
   17    2. Redistributions in binary form must reproduce the above copyright
   18       notice, this list of conditions and the following disclaimer in
   19       the documentation and/or other materials provided with the
   20       distribution.
   21
   22    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   23    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   24    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   25    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   26    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   27    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   28    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   29    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   30    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   31    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   32    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   33    POSSIBILITY OF SUCH DAMAGE.
   34*/
   35
   36:- module(http_proxy, []).   37:- use_module(library(http/http_header)).   38:- use_module(library(socket)).   39
   40/** <module> Use HTTP network proxies
   41
   42This  module  provides  a  plugin  for   tcp_connect/3  to  realise  TCP
   43connections through an HTTP proxy that   supports the HTTP 1.1 =CONNECT=
   44method.
   45*/
   46
   47                 /*******************************
   48                 *            PROXY             *
   49                 *******************************/
   50
   51%!  socket:try_proxy(+Proxy, +Address, -Socket, -StreamPair)
   52%
   53%   Connection is via an HTTP proxy   for  socket: Use HTTP CONNECT.
   54%   Note that most proxies will only  support this for connecting on
   55%   port 443
   56%
   57%   @arg Proxy is of the form proxy(Host, Port)
   58%   @error proxy_error(Message) if the proxy connection is
   59%   not successful.
   60
   61socket:try_proxy(proxy(Host, Port), Address, Socket, StreamPair) :-
   62    !,
   63    tcp_socket(Socket),
   64    tcp_connect(Socket, Host:Port, StreamPair),
   65    catch(negotiate_http_connect(StreamPair, Address),
   66          Error,
   67          ( close(StreamPair, [force(true)]),
   68            throw(Error)
   69          )).
   70
   71negotiate_http_connect(StreamPair, Address) :-
   72    format(StreamPair, 'CONNECT ~w HTTP/1.1\r\n\r\n', [Address]),
   73    flush_output(StreamPair),
   74    http_read_reply_header(StreamPair, Header),
   75    memberchk(status(_, Status, Message), Header),
   76    (   Status == ok
   77    ->  true
   78    ;   throw(error(proxy_error(Message), _))
   79    )