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): 2013-2025, VU University Amsterdam 7 CWI, Amsterdam 8 SWI-Prolog Solutions b.v. 9 10 This program is free software; you can redistribute it and/or 11 modify it under the terms of the GNU General Public License 12 as published by the Free Software Foundation; either version 2 13 of the License, or (at your option) any later version. 14 15 This program is distributed in the hope that it will be useful, 16 but WITHOUT ANY WARRANTY; without even the implied warranty of 17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 18 GNU General Public License for more details. 19 20 You should have received a copy of the GNU General Public 21 License along with this library; if not, write to the Free Software 22 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 23 24 As a special exception, if you link this library with other files, 25 compiled with a Free Software compiler, to produce an executable, this 26 library does not by itself cause the resulting executable to be covered 27 by the GNU General Public License. This exception does not however 28 invalidate any other reasons why the executable file might be covered by 29 the GNU General Public License. 30*/ 31 32:- module(recaptcha, 33 [ recaptcha//1, % +Options 34 recaptcha_parameters/1, % -HTTP parameter list 35 recaptcha_verify/2 % +Request, +HTTPParamList 36 ]). 37:- use_module(library(http/html_write)). 38:- use_module(library(http/http_open)). 39:- use_module(library(option)). 40:- use_module(library(debug)). 41:- use_module(library(json)).
79:- multifile 80 key/2. 81 82test_key(public, '6LeIxAcTAAAAAJcZVRqyHh71UMIEGNQ_MXjiZKhI'). 83test_key(private, '6LeIxAcTAAAAAGG-vFI1TnRWxMZNFuojJ4WifJWe').
clean.
96recaptcha(Options) -->
97 { ( key(public, PublicKey)
98 -> true
99 ; test_key(public, PublicKey)
100 ),
101 option(theme(Theme), Options, clean)
102 },
103 html_post(head, script([src('https://www.google.com/recaptcha/api.js'),
104 async(async),
105 defer(defer)
106 ], [])),
107 html(div([ class('g-recaptcha'),
108 'data-theme'(Theme),
109 'data-sitekey'(PublicKey)
110 ], [])).
117recaptcha_parameters(
118 [ 'g-recaptcha-response'(_Response, [])
119 ]).133recaptcha_verify(Request, Parameters) :- 134 memberchk('g-recaptcha-response'(Response, _), Parameters), 135 remote_IP(Request, Peer), 136 ( key(private, PrivateKey) 137 -> true 138 ; test_key(private, PrivateKey) 139 ), 140 debug(recaptcha, 'Verify: response ~p for IP ~p', [Response, Peer]), 141 setup_call_cleanup( 142 http_open('https://www.google.com/recaptcha/api/siteverify', 143 In, 144 [ post(form([ secret(PrivateKey), 145 remoteip(Peer), 146 response(Response) 147 ])) 148 ]), 149 json_read_dict(In, Dict), 150 close(In)), 151 debug(recaptcha, 'Recaptcha verify: ~p', [Dict]), 152 ( is_dict(Dict, _), 153 Dict.get(success) == true 154 -> true 155 ; is_dict(Dict, _), 156 Dict.get(success) == false 157 -> fail 158 ; throw(error(recaptcha_error(Dict), _)) 159 ). 160 161 162remote_IP(Request, IP) :- 163 memberchk(x_forwarded_for(IP0), Request), !, 164 atomic_list_concat(Parts, ', ', IP0), 165 last(Parts, IP). 166remote_IP(Request, IP) :- 167 memberchk(peer(Peer), Request), !, 168 peer_to_ip(Peer, IP). 169remote_IP(_, -). 170 171 172peer_to_ip(ip(A,B,C,D), IP) :- 173 atomic_list_concat([A,B,C,D], '.', IP).
public and to the reCAPTCHA private key if Which is private.
We leave the key handling to a hook to accomodate different ways for storing and transferring the keys. A simple implementation is:
:- use_module(library(http/recaptcha)). :- multifile recaptcha:key/2. recaptcha:key(public, 'Public key goes here'). recaptcha:key(private, 'Private key goes here').
When missing, a reserved test key pair is used.
Add reCAPTCHA functionality to a form
This module is a plugin for the SWI-Prolog HTTP/HTML framework to add reCAPTCHA functionality to a form. It works as follows:
method('POST')and include, in addition to the data you request from the human user, the reCAPTCHA widget using e.g.,process_recaptcha_form(Request) :- recaptcha_parameters(RecapthaParams), http_parameters(Recaptha, [ name(Name, []), age(Age, []), ... | RecapthaParams ]), ( recaptcha_verify(Request, RecapthaParams) -> <process normal user fields> ; <you are not human> ).examples/demo.plcontains a fully functional demo.