1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        jan@swi-prolog.org
    5    WWW:           https://www.swi-prolog.org
    6    Copyright (C): 2015-2025, VU University Amsterdam
    7			      SWI-Prolog Solutions b.v.
    8
    9    This program is free software; you can redistribute it and/or
   10    modify it under the terms of the GNU General Public License
   11    as published by the Free Software Foundation; either version 2
   12    of the License, or (at your option) any later version.
   13
   14    This program is distributed in the hope that it will be useful,
   15    but WITHOUT ANY WARRANTY; without even the implied warranty of
   16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   17    GNU General Public License for more details.
   18
   19    You should have received a copy of the GNU General Public
   20    License along with this library; if not, write to the Free Software
   21    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
   22
   23    As a special exception, if you link this library with other files,
   24    compiled with a Free Software compiler, to produce an executable, this
   25    library does not by itself cause the resulting executable to be covered
   26    by the GNU General Public License. This exception does not however
   27    invalidate any other reasons why the executable file might be covered by
   28    the GNU General Public License.
   29*/
   30
   31:- module(jwt,
   32	  [ jwt/2			% +String, -Data
   33	  ]).   34:- use_module(library(codesio)).   35:- use_module(library(base64)).   36:- use_module(library(utf8)).   37:- use_module(library(json)).   38
   39/** <module> JSON Web Token library
   40
   41This library is a very  early  start   to  deal  with  JOSE: JSON Object
   42Signing and Encryption. This is needed   for OpenID Connect. The current
   43library only extracts the claimed object  from a non-encrypted JWT (JSON
   44Web Token). This is enough to deal   with Google's OpenID Connect, which
   45guarantees that the token comes from Google in other ways.
   46
   47@see https://tools.ietf.org/html/draft-jones-json-web-token
   48*/
   49
   50%%	jwt(+String, -Object) is det.
   51%
   52%	True if Object is claimed in the JWT represented in String.
   53%
   54%	@tbd Currently does not validate the claim using the signature.
   55
   56jwt(String, Object) :-
   57	nonvar(String),
   58	split_string(String, ".", "", [Header64,Object64|_Parts]),
   59	base64url_json(Header64, _Header),
   60	base64url_json(Object64, Object).
   61
   62%%	base64url_json(+String, -JSONDict) is semidet.
   63%
   64%	True when JSONDict is represented  in   the  Base64URL and UTF-8
   65%	encoded String.
   66
   67base64url_json(String, JSON) :-
   68	string_codes(String, Codes),
   69	phrase(base64url(Bytes), Codes),
   70	phrase(utf8_codes(Text), Bytes),
   71	setup_call_cleanup(
   72	    open_codes_stream(Text, Stream),
   73	    json_read_dict(Stream, JSON),
   74	    close(Stream))