1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2006-2023, University of Amsterdam
    7                              VU University Amsterdam
    8                              SWI-Prolog Solutions b.v.
    9    All rights reserved.
   10
   11    Redistribution and use in source and binary forms, with or without
   12    modification, are permitted provided that the following conditions
   13    are met:
   14
   15    1. Redistributions of source code must retain the above copyright
   16       notice, this list of conditions and the following disclaimer.
   17
   18    2. Redistributions in binary form must reproduce the above copyright
   19       notice, this list of conditions and the following disclaimer in
   20       the documentation and/or other materials provided with the
   21       distribution.
   22
   23    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   24    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   25    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   26    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   27    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   28    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   29    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   30    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   31    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   33    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   34    POSSIBILITY OF SUCH DAMAGE.
   35*/
   36
   37:- module(http_error,
   38          [
   39          ]).   40:- use_module(library(prolog_stack), []).   41:- use_module(library(settings)).   42:- use_module(library(broadcast)).   43:- use_module(library(debug)).   44
   45/** <module> Decorate uncaught HTTP exceptions with stack-trace
   46
   47This module decorates uncaught exceptions of the   user code with a full
   48stack-trace and sends error reports to the Prolog console. The behaviour
   49can be controlled by
   50
   51  - nodebug(http(error))
   52    After disabling the http(error) debug channal, errors are only sent
   53    to the client.  See nodebug/1 and debug/1.
   54  - set_setting(http:client_backtrace, false)
   55    Stop sending stack traces to the client. Note that sending the stack
   56    trace to the client simplifies debugging, it also provides clues to
   57    hackers on how to compromise your site. The more information you
   58    give them, the easier it is to break into your server!  See
   59    set_setting/2 and set_setting_default/2.
   60  - assert(http_error:suppress_code(Code)) makes this library become
   61    silent for replies with a matching HTTP status code.   This may be
   62    used to suppress >400 replies that are "normal" in the application.
   63*/
   64
   65:- setting(http:client_backtrace, boolean, true,
   66           'Make backtrace visible to the client').   67
   68
   69                 /*******************************
   70                 *     LOG ERRORS TO STDERR     *
   71                 *******************************/
   72
   73:- debug(http(error)).   74
   75:- listen(http(Message),
   76          http_listen(Message)).   77
   78:- dynamic
   79    saved_request/2,
   80    suppress_code/1.   81
   82http_listen(_) :-
   83    \+ debugging(http(error)),
   84    !.
   85http_listen(request_start(Id, Request)) :-
   86    !,
   87    asserta(saved_request(Id, Request)).
   88http_listen(request_finished(Id, Code, Status, _CPU, _Bytes)) :-
   89    retract(saved_request(Id, Request)),
   90    !,
   91    Code >= 400,
   92    \+ suppress_code(Code),
   93    memberchk(path(Path), Request),
   94    memberchk(method(Method), Request),
   95    upcase_atom(Method, UMethod),
   96    reply_status(Status, Reply),
   97    debug(http(error),
   98          '~w ~w: [~w] ~w', [UMethod, Path, Code, Reply]).
   99
  100reply_status(Status, Reply) :-
  101    map_exception(Status, Reply),
  102    !.
  103reply_status(Status, Message) :-
  104    Status = error(_,_),
  105    !,
  106    message_to_string(Status, Message).
  107reply_status(Status, Status).
  108
  109map_exception(http_reply(bytes(ContentType,Bytes),_), bytes(ContentType,L)) :-
  110    string_length(Bytes, L).        % also does lists
  111map_exception(http_reply(Reply), Reply).
  112map_exception(http_reply(Reply, _), Reply).
  113map_exception(error(existence_error(http_location, Location), _Stack),
  114              error(404, Location)).
  115
  116
  117                 /*******************************
  118                 *     DECORATE STACK TRACES    *
  119                 *******************************/
  120
  121:- dynamic prolog_stack:stack_guard/1.  122:- multifile prolog_stack:stack_guard/1.  123
  124prolog_stack:stack_guard(httpd_wrapper:wrapper/5).
  125prolog_stack:stack_guard(httpd_wrapper:handler_with_output_to/5)