/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (c) 2002-2017, University of Amsterdam
VU University Amsterdam
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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*/
:- module(httpd_wrapper,
[ http_wrapper/5, % :Goal, +In, +Out, -Conn, +Options
http_current_request/1, % -Request
http_peer/2, % +Request, -PeerIP
http_send_header/1, % +Term
http_relative_path/2, % +AbsPath, -RelPath
% Internal API
http_wrap_spawned/3, % :Goal, -Request, -Connection
http_spawned/1 % +ThreadId
]).
:- use_module(http_header).
:- use_module(http_stream).
:- use_module(http_exception).
:- use_module(library(lists)).
:- use_module(library(debug)).
:- use_module(library(broadcast)).
:- meta_predicate
http_wrapper(0, +, +, -, +).
:- multifile
http:request_expansion/2.
/** <module> Server processing of an HTTP request
Most code doesn't need to use this directly; instead use
library(http/http_server), which combines this library with the
typical HTTP libraries that most servers need.
This library provides the core of the implementation of the HTTP
protocol at the server side and is mainly intended for *internal use*.
It is used by library(thread_httpd) and library(inet_httpd)
(deprecated).
Still, it provides a few predicates that are occasinally useful for
applications:
- http_current_request/1 finds the current request for occasional
usage in places where it is not avaialable otherwise.
- http_peer/2 finds the (IP4) peer address, getting the original
address if we are behind a proxy (=X-Forwarded-For=)
- http_relative_path/2 can be used to find a relative path from
the current request.
*/
%! http_wrapper(:Goal, +In, +Out, -Close, +Options) is det.
%
% Simple wrapper to read and decode an HTTP header from `In', call
% :Goal while watching for exceptions and send the result to the
% stream `Out'.
%
% The goal is assumed to write the reply to =current_output=
% preceeded by an HTTP header, closed by a blank line. The header
% *must* contain a Content-type: <type> line. It may optionally
% contain a line =|Transfer-encoding: chunked|= to request chunked
% encoding.
%
% Options:
%
% * request(-Request)
% Return the full request to the caller
% * peer(+Peer)
% IP address of client
%
% @param Close Unified to one of =close=, =|Keep-Alive|= or
% spawned(ThreadId).
http_wrapper(Goal, In, Out, Close, Options) :-
status(Id, State0),
catch(http_read_request(In, Request0), ReqError, true),
( Request0 == end_of_file
-> Close = close,
extend_request(Options, [], _) % return request
; var(ReqError)
-> extend_request(Options, Request0, Request1),
cgi_open(Out, CGI, cgi_hook, [request(Request1)]),
cgi_property(CGI, id(Id)),
( debugging(http(request))
-> memberchk(method(Method), Request1),
memberchk(path(Location), Request1),
debug(http(request), "[~D] ~w ~w ...", [Id,Method,Location])
; true
),
handler_with_output_to(Goal, Id, Request1, CGI, Error),
cgi_close(CGI, Request1, State0, Error, Close)
; Id = 0,
add_header_context(ReqError),
( debugging(http(request))
-> print_message(warning, ReqError)
; true
),
send_error(Out, [], State0, ReqError, Close),
extend_request(Options, [], _)
).
add_header_context(error(_,context(_,in_http_request))) :- !.
add_header_context(_).
status(Id, state0(Thread, CPU, Id)) :-
thread_self(Thread),
thread_cputime(CPU).
%! http_wrap_spawned(:Goal, -Request, -Close) is det.
%
% Internal use only. Helper for wrapping the handler for
% http_spawn/2.
%
% @see http_spawned/1, http_spawn/2.
http_wrap_spawned(Goal, Request, Close) :-
current_output(CGI),
cgi_property(CGI, id(Id)),
handler_with_output_to(Goal, Id, -, current_output, Error),
( retract(spawned(ThreadId))
-> Close = spawned(ThreadId),
Request = []
; cgi_property(CGI, request(Request)),
status(Id, State0),
catch(cgi_close(CGI, Request, State0, Error, Close),
_,
Close = close)
).
:- thread_local
spawned/1.
%! http_spawned(+ThreadId)
%
% Internal use only. Indicate that the request is handed to thread
% ThreadId.
http_spawned(ThreadId) :-
assert(spawned(ThreadId)).
%! cgi_close(+CGI, +Request, +State0, +Error, -Close) is det.
%
% The wrapper has completed. Finish the CGI output. We have three
% cases:
%
% * The wrapper delegated the request to a new thread
% * The wrapper succeeded
% * The wrapper threw an error, non-200 status reply
% (e.g., =not_modified=, =moved=) or a request to reply with
% the content of a file.
%
% @error socket I/O errors.
cgi_close(_, _, _, _, Close) :-
retract(spawned(ThreadId)),
!,
Close = spawned(ThreadId).
cgi_close(CGI, _, State0, ok, Close) :-
!,
catch(cgi_finish(CGI, Status, Close, Bytes), E, true),
( var(E)
-> http_done(Status, ok, Bytes, State0)
; http_done(500, E, 0, State0), % TBD: amount written?
throw(E)
).
cgi_close(CGI, Request, Id, http_reply(Status), Close) :-
!,
cgi_close(CGI, Request, Id, http_reply(Status, []), Close).
cgi_close(CGI, Request, Id, http_reply(Status, ExtraHdrOpts), Close) :-
cgi_property(CGI, header_codes(Text)),
Text \== [],
!,
http_parse_header(Text, ExtraHdrCGI),
cgi_property(CGI, client(Out)),
cgi_discard(CGI),
close(CGI),
append(ExtraHdrCGI, ExtraHdrOpts, ExtraHdr),
send_error(Out, Request, Id, http_reply(Status, ExtraHdr), Close).
cgi_close(CGI, Request, Id, Error, Close) :-
cgi_property(CGI, client(Out)),
cgi_discard(CGI),
close(CGI),
send_error(Out, Request, Id, Error, Close).
cgi_finish(CGI, Status, Close, Bytes) :-
flush_output(CGI), % update the content-length
cgi_property(CGI, connection(Close)),
cgi_property(CGI, content_length(Bytes)),
( cgi_property(CGI, header(Header)),
memberchk(status(Status), Header)
-> true
; Status = 200
),
close(CGI).
%! send_error(+Out, +Request, +State0, +Error, -Close)
%
% Send status replies and reply files. The =current_output= no
% longer points to the CGI stream, but simply to the socket that
% connects us to the client.
%
% @param State0 is start-status as returned by status/1. Used to
% find CPU usage, etc.
send_error(Out, Request, State0, Error, Close) :-
map_exception_to_http_status(Error, Reply, HdrExtra0, Context),
update_keep_alive(HdrExtra0, HdrExtra, Request),
catch(http_reply(Reply,
Out,
[ content_length(CLen)
| HdrExtra
],
Context,
Request,
Code),
E, true),
( var(E)
-> http_done(Code, Error, CLen, State0)
; http_done(500, E, 0, State0),
throw(E) % is that wise?
),
( Error = http_reply(switching_protocols(Goal, SwitchOptions), _)
-> Close = switch_protocol(Goal, SwitchOptions)
; memberchk(connection(Close), HdrExtra)
-> true
; Close = close
).
update_keep_alive(Header0, Header, Request) :-
memberchk(connection(C), Header0),
!,
( C == close
-> Header = Header0
; client_wants_close(Request)
-> selectchk(connection(C), Header0,
connection(close), Header)
; Header = Header0
).
update_keep_alive(Header, Header, _).
client_wants_close(Request) :-
memberchk(connection(C), Request),
!,
C == close.
client_wants_close(Request) :-
\+ ( memberchk(http_version(Major-_Minor), Request),
Major >= 1
).
%! http_done(+Code, +Status, +BytesSent, +State0) is det.
%
% Provide feedback for logging and debugging on how the request
% has been completed.
http_done(Code, Status, Bytes, state0(_Thread, CPU0, Id)) :-
thread_cputime(CPU1),
CPU is CPU1 - CPU0,
( debugging(http(request))
-> debug_request(Code, Status, Id, CPU, Bytes)
; true
),
broadcast(http(request_finished(Id, Code, Status, CPU, Bytes))).
%! handler_with_output_to(:Goal, +Id, +Request, +Output, -Status) is det.
%
% Run Goal with output redirected to Output. Unifies Status with
% =ok=, the error from catch/3 or a term error(goal_failed(Goal),
% _).
%
% @param Request The HTTP request read or '-' for a continuation
% using http_spawn/2.
handler_with_output_to(Goal, Id, Request, current_output, Status) :-
!,
( catch(call_handler(Goal, Id, Request), Status, true)
-> ( var(Status)
-> Status = ok
; true
)
; Status = error(goal_failed(Goal),_)
).
handler_with_output_to(Goal, Id, Request, Output, Error) :-
stream_property(OldOut, alias(current_output)),
set_output(Output),
handler_with_output_to(Goal, Id, Request, current_output, Error),
set_output(OldOut).
call_handler(Goal, _, -) :- % continuation through http_spawn/2
!,
call(Goal).
call_handler(Goal, Id, Request0) :-
expand_request(Request0, Request),
current_output(CGI),
cgi_set(CGI, request(Request)),
broadcast(http(request_start(Id, Request))),
call(Goal, Request).
%! thread_cputime(-CPU) is det.
%
% CPU is the CPU time used by the calling thread.
thread_cputime(CPU) :-
statistics(cputime, CPU).
%! cgi_hook(+Event, +CGI) is det.
%
% Hook called from the CGI processing stream. See http_stream.pl
% for details.
:- public cgi_hook/2.
cgi_hook(What, _CGI) :-
debug(http(hook), 'Running hook: ~q', [What]),
fail.
cgi_hook(header, CGI) :-
cgi_property(CGI, header_codes(HeadText)),
cgi_property(CGI, header(Header0)), % see http_send_header/1
http_parse_header(HeadText, CgiHeader0),
append(Header0, CgiHeader0, CgiHeader),
cgi_property(CGI, request(Request)),
http_update_connection(CgiHeader, Request, Connection, Header1),
http_update_transfer(Request, Header1, Transfer, Header2),
http_update_encoding(Header2, Encoding, Header),
set_stream(CGI, encoding(Encoding)),
cgi_set(CGI, connection(Connection)),
cgi_set(CGI, header(Header)),
debug(http(transfer_encoding), 'Transfer-encoding: ~w', [Transfer]),
cgi_set(CGI, transfer_encoding(Transfer)). % must be LAST
cgi_hook(send_header, CGI) :-
cgi_property(CGI, header(Header)),
debug(http(cgi), 'Header: ~q', [Header]),
cgi_property(CGI, client(Out)),
( redirect(Header, Action, RedirectHeader)
-> http_status_reply(Action, Out, RedirectHeader, _),
cgi_discard(CGI)
; cgi_property(CGI, transfer_encoding(chunked))
-> http_reply_header(Out, chunked_data, Header)
; cgi_property(CGI, content_length(Len))
-> http_reply_header(Out, cgi_data(Len), Header)
).
cgi_hook(close, _).
%! redirect(+Header, -Action, -RestHeader) is semidet.
%
% Detect the CGI =Location= and optional =Status= headers for
% formulating a HTTP redirect. Redirection is only established if
% no =Status= is provided, or =Status= is 3XX.
redirect(Header, Action, RestHeader) :-
selectchk(location(To), Header, Header1),
( selectchk(status(Status), Header1, RestHeader)
-> between(300, 399, Status)
; RestHeader = Header1,
Status = 302
),
redirect_action(Status, To, Action).
redirect_action(301, To, moved(To)).
redirect_action(302, To, moved_temporary(To)).
redirect_action(303, To, see_other(To)).
%! http_send_header(+Header)
%
% This API provides an alternative for writing the header field as
% a CGI header. Header has the format Name(Value), as produced by
% http_read_header/2.
%
% @deprecated Use CGI lines instead
http_send_header(Header) :-
current_output(CGI),
cgi_property(CGI, header(Header0)),
cgi_set(CGI, header([Header|Header0])).
%! expand_request(+Request0, -Request)
%
% Allow for general rewrites of a request by calling
% http:request_expansion/2.
expand_request(R0, R) :-
http:request_expansion(R0, R1), % Hook
R1 \== R0,
!,
expand_request(R1, R).
expand_request(R, R).
%! extend_request(+Options, +RequestIn, -Request)
%
% Merge options in the request.
extend_request([], R, R).
extend_request([request(R)|T], R0, R) :-
!,
extend_request(T, R0, R).
extend_request([H|T], R0, R) :-
request_option(H),
!,
extend_request(T, [H|R0], R).
extend_request([_|T], R0, R) :-
extend_request(T, R0, R).
request_option(peer(_)).
request_option(protocol(_)).
request_option(pool(_)).
%! http_current_request(-Request) is semidet.
%
% Returns the HTTP request currently being processed. Fails
% silently if there is no current request. This typically happens
% if a goal is run outside the HTTP server context.
http_current_request(Request) :-
current_output(CGI),
is_cgi_stream(CGI),
cgi_property(CGI, request(Request)).
%! http_peer(+Request, -PeerIP:atom) is semidet.
%
% True when PeerIP is the IP address of the connection peer. If the
% connection is established via a proxy or CDN we try to find the
% initiating peer. Currently supports:
%
% - =Fastly-client-ip=
% - =X-real-ip=
% - =X-forwarded-for=
% - Direct connections
%
% @bug The =X-forwarded-for= header is problematic. According to
% [Wikipedia](https://en.wikipedia.org/wiki/X-Forwarded-For), the
% original client is the _first_, while according to
% [AWS](http://docs.aws.amazon.com/elasticloadbalancing/latest/classic/x-forwarded-headers.html)
% it is the _last_.
http_peer(Request, Peer) :-
memberchk(fastly_client_ip(Peer), Request), !.
http_peer(Request, Peer) :-
memberchk(x_real_ip(Peer), Request), !.
http_peer(Request, IP) :-
memberchk(x_forwarded_for(IP0), Request),
!,
atomic_list_concat(Parts, ', ', IP0),
last(Parts, IP).
http_peer(Request, IP) :-
memberchk(peer(Peer), Request),
!,
peer_to_ip(Peer, IP).
peer_to_ip(ip(A,B,C,D), IP) :-
atomic_list_concat([A,B,C,D], '.', IP).
%! http_relative_path(+AbsPath, -RelPath) is det.
%
% Convert an absolute path (without host, fragment or search) into
% a path relative to the current page. This call is intended to
% create reusable components returning relative paths for easier
% support of reverse proxies.
http_relative_path(Path, RelPath) :-
http_current_request(Request),
memberchk(path(RelTo), Request),
http_relative_path(Path, RelTo, RelPath),
!.
http_relative_path(Path, Path).
http_relative_path(Path, RelTo, RelPath) :-
atomic_list_concat(PL, /, Path),
atomic_list_concat(RL, /, RelTo),
delete_common_prefix(PL, RL, PL1, PL2),
to_dot_dot(PL2, DotDot, PL1),
atomic_list_concat(DotDot, /, RelPath).
delete_common_prefix([H|T01], [H|T02], T1, T2) :-
!,
delete_common_prefix(T01, T02, T1, T2).
delete_common_prefix(T1, T2, T1, T2).
to_dot_dot([], Tail, Tail).
to_dot_dot([_], Tail, Tail) :- !.
to_dot_dot([_|T0], ['..'|T], Tail) :-
to_dot_dot(T0, T, Tail).
/*******************************
* DEBUG SUPPORT *
*******************************/
%! debug_request(+Code, +Status, +Id, +CPU0, Bytes)
%
% Emit debugging info after a request completed with Status.
debug_request(Code, ok, Id, CPU, Bytes) :-
!,
debug(http(request), '[~D] ~w OK (~3f seconds; ~D bytes)',
[Id, Code, CPU, Bytes]).
debug_request(Code, Status, Id, _, Bytes) :-
map_exception(Status, Reply),
!,
debug(http(request), '[~D] ~w ~w; ~D bytes',
[Id, Code, Reply, Bytes]).
debug_request(Code, Except, Id, _, _) :-
Except = error(_,_),
!,
message_to_string(Except, Message),
debug(http(request), '[~D] ~w ERROR: ~w',
[Id, Code, Message]).
debug_request(Code, Status, Id, _, Bytes) :-
debug(http(request), '[~D] ~w ~w; ~D bytes',
[Id, Code, Status, Bytes]).
map_exception(http_reply(Reply), Reply).
map_exception(http_reply(Reply, _), Reply).
map_exception(error(existence_error(http_location, Location), _Stack),
error(404, Location)).