1/*  Part of SWISH
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@cs.vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (C): 2017, VU University Amsterdam
    7			 CWI 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(config_auth_stackoverflow, []).   37:- use_module(swish(lib/oauth2)).   38:- use_module(swish(lib/plugin/login)).   39:- use_module(library(http/http_open)).   40:- use_module(library(http/http_dispatch)).   41:- use_module(library(http/http_header)).   42:- use_module(library(http/http_session)).   43:- use_module(library(http/http_json)).   44:- use_module(library(http/json)).   45:- use_module(library(http/http_path)).   46:- use_module(library(uri)).   47:- use_module(library(debug)).   48:- use_module(library(apply)).

   69:- multifile
   70    oauth2:login/3,
   71    oauth2:server_attribute/3,
   72    swish_config:login_item/2,          % -Server, -HTML_DOM
   73    swish_config:login/2,               % +Server, +Request
   74    swish_config:user_info/2.           % +Request, ?Server, -Info
   75
   76:- http_set_session_options([create(noauto)]).   77
   78:- http_handler(swish(logout), stackexchange_logout, []).

 oauth2:server_attribute(?ServerID, ?Attribute, ?Value)

Declare properties of an oauth2 identity provider. The values below are for StackExchange server.

EDIT:

• url: base URL of the stackexchange authentication server
• api_endpoint: Stack Apps API endpoint
• redirect_uri: our location
• client_id: Client Id from Stack Apps
• client_secret: Client Secret from Stack Apps
• key: Key from Stack Apps to access their API (/me)
• site: Stack exchange site for which to ask info

See also

- swish(lib/oauth2) for a description of the attributes.

   95oauth2:server_attribute(stackexchange, url,
   96                        'https://stackexchange.com').
   97oauth2:server_attribute(stackexchange, redirect_uri,
   98                        'http://cplint.eu/oauth2/stackexchange/reply').
   99oauth2:server_attribute(stackexchange, authorization_endpoint,
  100                        '/oauth').
  101oauth2:server_attribute(stackexchange, token_endpoint,
  102                        '/oauth/access_token').
  103oauth2:server_attribute(stackexchange, api_endpoint,
  104                        'https://api.stackexchange.com').
  105oauth2:server_attribute(stackexchange, client_id,
  106                        '12983').
  107oauth2:server_attribute(stackexchange, client_secret,
  108                        'gTRdP5ub6ktEVrBXmOaOCA((').
  109oauth2:server_attribute(stackexchange, key,
  110                        'eAFMxVCc)KtvEvIZvCfiOA((').
  111oauth2:server_attribute(stackexchange, site,
  112                        'stackoverflow').
  113oauth2:server_attribute(stackexchange, scope,
  114                        '').
  115
  116
  117		 /*******************************
  118		 *          SWISH HOOKS		*
  119		 *******************************/
  120
  121swish_config:login_item(stackexchange, 10-Item) :-
  122    http_absolute_location(icons('so-icon.png'), Img, []),
  123    Item = img([ src(Img),
  124                 class('login-with'),
  125                 'data-server'(stackexchange),
  126                 'data-frame'(popup),
  127                 title('Login with StackOverflow')
  128               ]).
  129
  130swish_config:login(stackexchange, Request) :-
  131    oauth2_login(Request, [server(stackexchange)]).
  132
  133oauth2:login(_Request, stackexchange, TokenInfo) :-
  134    debug(oauth, 'TokenInfo: ~p', [TokenInfo]),
  135    stackexchange_me(TokenInfo.access_token, Claim),
  136    debug(oauth, 'Claim: ~p', [Claim]),
  137    map_user_info(Claim, UserInfo),
  138    http_open_session(_SessionID, []),
  139    session_remove_user_data,
  140    http_session_assert(oauth2(stackexchange, TokenInfo)),
  141    http_session_assert(user_info(stackexchange, UserInfo)),
  142    reply_logged_in([ identity_provider('StackOverflow'),
  143                      name(UserInfo.name),
  144                      user_info(UserInfo)
  145                    ]).

 stackexchange_me(+AccessToken, -Info)

Stack exchange does not support the oauth2 user_info endpoint. Instead, we must use the =/me= API. This is a little unlucky as we need to duplicate some infrastructure from the generic oauth2.pl module.

  154stackexchange_me(AccessToken, Info) :-
  155    oauth2:server_attribute(stackexchange, api_endpoint,  URLBase),
  156    oauth2:server_attribute(stackexchange, client_id,     ClientID),
  157    oauth2:server_attribute(stackexchange, client_secret, ClientSecret),
  158    oauth2:server_attribute(stackexchange, key,           Key),
  159    oauth2:server_attribute(stackexchange, site,          Site),
  160
  161    uri_extend(URLBase, '/2.2/me',
  162               [ key(Key),
  163                 site(Site),
  164                 access_token(AccessToken)
  165               ],
  166               URL),
  167
  168    setup_call_cleanup(
  169        http_open(URL, In,
  170                  [ authorization(basic(ClientID, ClientSecret)),
  171                    header(content_type, ContentType),
  172                    status_code(Code)
  173                  ]),
  174        read_reply(Code, ContentType, In, Info0),
  175        close(In)),
  176    me_info(Info0, Info).
  177
  178me_info(Info, Me) :-
  179    [Me] = Info.get(items),
  180    !.
  181me_info(Info, Info).
  182
  183
  184read_reply(Code, ContentType, In, Dict) :-
  185    debug(oauth, '/me returned ~p ~p', [Code, ContentType]),
  186    http_parse_header_value(content_type, ContentType, Parsed),
  187    read_reply2(Code, Parsed, In, Dict).

 read_reply2(+Code, +ContentType, +Stream, -Dict) is det

Read the server reply as a dict. Normally, the reply is a JSON object, but stackexchange seems to send it as a www-form-encoded string.

  195read_reply2(200, media(application/json, _Attributes), In, Dict) :- !,
  196    json_read_dict(In, Dict).
  197read_reply2(Code, media(application/json, _Attributes), In,
  198            error{code:Code, details:Details}) :- !,
  199    json_read_dict(In, Details).
  200read_reply2(Code, Type, In,
  201            error{code:Code, message:Reply}) :-
  202    debug(oauth(token), 'Got code ~w, type ~q', [Code, Type]),
  203    read_string(In, _, Reply).

 stackexchange_logout(+Request)

Logout by removing the session data

  210stackexchange_logout(_Request) :-
  211    catch(session_remove_user_data, _, true),
  212    reply_logged_out([]).

 swish_config:user_info(+Request, ?Server, -Info:dict) is semidet

True if Info represents describes the currently logged in user.

  218swish_config:user_info(_Request, stackexchange, UserInfo) :-
  219    http_in_session(_SessionID),
  220    http_session_data(user_info(stackexchange, UserInfo)).

 map_user_info(+OAuthInfo, -UserInfo) is det

u{user:User, group:Group, name:Name, email:Email}

  226map_user_info(Dict0, Dict) :-
  227    dict_pairs(Dict0, Tag, Pairs0),
  228    maplist(map_user_field, Pairs0, Pairs),
  229    http_link_to_id(stackexchange_logout, [], LogoutURL),
  230    dict_pairs(Dict, Tag,
  231               [ identity_provider-stackexchange,
  232                 auth_method-oauth2,
  233                 logout_url-LogoutURL
  234               | Pairs
  235               ]).
  236
  237map_user_field(display_name-Name, name-Name) :- !.
  238map_user_field(profile_image-URL, picture-URL) :- !.
  239map_user_field(link-URL,          profile_url-URL) :- !.
  240map_user_field(user_id-Id,        external_identity-SId) :- !,
  241    format(string(SId), '~w', [Id]).
  242map_user_field(Field, Field).
  243
  244session_remove_user_data :-
  245    http_session_retractall(oauth2(_,_)),
  246    http_session_retractall(user_info(_,_)).
  247
  248
  249		 /*******************************
  250		 *	     URI BASICS		*
  251		 *******************************/

 uri_extend(+Base:atom, +Rel:atom, +Query:list, -URI:atom) is det

Create a URI from Base, A relative URI and a query.

  257uri_extend(Base, Relative, Query, URI) :-
  258    uri_resolve(Relative, Base, URI0),
  259    uri_extend_query(URI0, Query, URI).

 uri_extend_query(+URI0:atom, +Query:list, -URI:atom) is det

Extend a URI with a query. If URI0 already has a query, keep all parameters that do not conflict.

  266uri_extend_query(URI0, Query, URI) :-
  267    uri_components(URI0, Components0),
  268    extend_query(Components0, Query, Query1),
  269    uri_data(search, Components0, Query1, Components1),
  270    uri_components(URI, Components1).
  271
  272extend_query(Components, QueryEx, Query) :-
  273    uri_data(search, Components, Query0),
  274    (   var(Query0)
  275    ->  uri_query_components(Query, QueryEx)
  276    ;   uri_query_components(Query0, Q0),
  277        merge_components(Q0, QueryEx, Q),
  278        uri_query_components(Query, Q)
  279    ).
  280
  281merge_components([], Q, Q).
  282merge_components([N=_|T0], Q1, Q) :-
  283    memberchk(N=_, Q1), !,
  284    merge_components(T0, Q1, Q).
  285merge_components([H|T0], Q1, [H|Q]) :-
  286    merge_components(T0, Q1, Q)