I imagine a plugin that modifies the login screen to use <http://recaptcha.net/>. You would then be required to fill in the captcha as well as log in in the normal way.
+-- [[users/Will]]
+
> I hate CAPTCHAs with a passion. Someone else is welcome to write such a
> plugin.
>
>> white/black lists, were you thinking of listing the openids, or the content?
>> Something like the moinmoin global <http://master.moinmo.in/BadContent>
>> list?
+
+>>> OpenID can be thought of as pushing the problem of determining if
+>>> someone is a human or a spambot back from the openid consumer to the
+>>> openid provider. So, providers that make it possible for spambots to
+>>> use their openids, or that are even set up explicitly for use in
+>>> spamming, would be the ones to block. Or, providers that are known to
+>>> use very good screening for humans would be the ones to allow.
+>>> (Openid delegation makes it a bit harder than just looking at the
+>>> openid url though.) --[[Joey]]
+
+>>>> Well, OpenID only addresses authentication issues, not authorisation issues.
+>>>> Given that it is trivial to set up your own OpenID provider (a full provider, not
+>>>> just a forward to another provider), I can't see a
+>>>> blacklist working in the long term (it would be like blacklisting email).
+>>>> A whitelist might work (it would not be quite as bad as whitelisting email). In any case,
+>>>> there is now a captcha plugin for those that want it. It is accessible
+>>>> (there is an audio option) and serves a social purpose along with
+>>>> keeping bots out (the captcha is used to help digitise hard to read
+>>>> words in books for [Carnegie Mellon University](http://www.cs.cmu.edu/) and
+>>>> [The Internet Archive](http://www.archive.org/) ). Finally, because the actual captcha is outsourced
+>>>> it means that someone else is taking care of keeping it ahead of
+>>>> the bot authors.
+
+Okie - I have a first pass of this. There are still some issues.
+
+Currently the code verifies the CAPTCHA. If you get it right then you're fine.
+If you get the CAPTCHA wrong then the current code tells formbuilder that
+one of the fields is invalid. This stops the login from going through.
+Unfortunately, formbuilder is caching this validity somewhere, and I haven't
+found a way around that yet. This means that if you get the CAPTCHA
+wrong, it will continue to fail. You need to load the login page again so
+it doesn't have the error message on the screen, then it'll work again.
+
+> fixed this - updated code is attached.
+
+A second issue is that the OpenID login system resets the 'required' flags
+of all the other fields, so using OpenID will cause the CAPTCHA to be
+ignored.
+
+> This is still not fixed. I would have thought the following patch would
+> have fixed this second issue, but it doesn't.
+
+(code snipped as a working [[patch]] is below)
+
+>> What seems to be happing here is that the openid plugin defines a
+>> validate hook for openid_url that calls validate(). validate() in turn
+>> redirects the user to the openid server for validation, and exits. If
+>> the openid plugins' validate hook is called before your recaptcha
+>> validator, your code never gets a chance to run. I don't know how to
+>> control the other that FormBuilder validates fields, but the only fix I
+>> can see is to somehow influence that order.
+>>
+>> Hmm, maybe you need to move your own validation code out of the validate
+>> hook. Instead, just validate the captcha in the formbuilder_setup hook.
+>> The problem with this approach is that if validation fails, you can't
+>> just flag it as invalid and let formbuilder handle that. Instead, you'd
+>> have to hack something in to redisplay the captcha by hand. --[[Joey]]
+
+>>> Fixed this. I just modified the OpenID plugin to check if the captcha
+>>> succeeded or failed. Seeing as the OpenID plugin is the one that is
+>>> abusing the normal validate method, I figured it was best to keep
+>>> the fix in the same place. I also added a config switch so you can set if
+>>> the captcha is needed for OpenID logins. OpenID defaults to ignoring
+>>> the captcha.
+>>> Patch is inline below.
+>>> I think this whole thing is working now.
+
+>>>> Ok, glad it's working. Not thrilled that it needs to modify the
+>>>> openid plugin, especially as I'm not sure if i I will integrate the
+>>>> captcha plugin into mainline. Also because it's not very clean to have
+>>>> the oprnid plugin aware of another plugin like that. I'd like to
+>>>> prusue my idea of not doing the captcha validation in the validate
+>>>> hook.
+
+--- a/IkiWiki/Plugin/openid.pm
++++ b/IkiWiki/Plugin/openid.pm
+@@ -18,6 +18,7 @@ sub getopt () {
+ error($@) if $@;
+ Getopt::Long::Configure('pass_through');
+ GetOptions("openidsignup=s" => \$config{openidsignup});
++ GetOptions("openidneedscaptcha=s" => \$config{openidneedscaptcha});
+ }
+
+ sub formbuilder_setup (@) {
+@@ -61,6 +62,7 @@ sub formbuilder_setup (@) {
+ # Skip all other required fields in this case.
+ foreach my $field ($form->field) {
+ next if $field eq "openid_url";
++ next if $config{openidneedscaptcha} && $field eq "recaptcha";
+ $form->field(name => $field, required => 0,
+ validate => '/.*/');
+ }
+@@ -96,6 +98,18 @@ sub validate ($$$;$) {
+ }
+ }
+
++ if ($config{openidneedscaptcha} && defined $form->field("recaptcha")) {
++ foreach my $field ($form->field) {
++ next unless ($field eq "recaptcha");
++ if (! $field->validate) {
++ # if they didn't get the captcha right,
++ # then just claim we validated ok so the
++ # captcha can cause a fail
++ return 1;
++ }
++ }
++ }
++
+ my $check_url = $claimed_identity->check_url(
+ return_to => IkiWiki::cgiurl(do => "postsignin"),
+ trust_root => $config{cgiurl},
+
+
+Instructions
+=====
+
+You need to go to <http://recaptcha.net/api/getkey> and get a key set.
+The keys are added as options.
+
+ reCaptchaPubKey => "LONGPUBLICKEYSTRING",
+ reCaptchaPrivKey => "LONGPRIVATEKEYSTRING",
+
+You can also use "signInSSL" if you're using ssl for your login screen.
+
+
+The following code is just inline. It will probably not display correctly, and you should just grab it from the page source.
+
+----------
+
+#!/usr/bin/perl
+# Ikiwiki password authentication.
+package IkiWiki::Plugin::recaptcha;
+
+use warnings;
+use strict;
+use IkiWiki 2.00;
+
+sub import {
+ hook(type => "formbuilder_setup", id => "recaptcha", call => \&formbuilder_setup);
+}
+
+sub getopt () {
+ eval q{use Getopt::Long};
+ error($@) if $@;
+ Getopt::Long::Configure('pass_through');
+ GetOptions("reCaptchaPubKey=s" => \$config{reCaptchaPubKey});
+ GetOptions("reCaptchaPrivKey=s" => \$config{reCaptchaPrivKey});
+}
+
+sub formbuilder_setup (@) {
+ my %params=@_;
+
+ my $form=$params{form};
+ my $session=$params{session};
+ my $cgi=$params{cgi};
+ my $pubkey=$config{reCaptchaPubKey};
+ my $privkey=$config{reCaptchaPrivKey};
+ debug("Unknown Public Key. To use reCAPTCHA you must get an API key from http://recaptcha.net/api/getkey")
+ unless defined $config{reCaptchaPubKey};
+ debug("Unknown Private Key. To use reCAPTCHA you must get an API key from http://recaptcha.net/api/getkey")
+ unless defined $config{reCaptchaPrivKey};
+ my $tagtextPlain=<<EOTAG;
+ <script type="text/javascript"
+ src="http://api.recaptcha.net/challenge?k=$pubkey">
+ </script>
+
+ <noscript>
+ <iframe src="http://api.recaptcha.net/noscript?k=$pubkey"
+ height="300" width="500" frameborder="0"></iframe><br>
+ <textarea name="recaptcha_challenge_field" rows="3" cols="40"></textarea>
+ <input type="hidden" name="recaptcha_response_field"
+ value="manual_challenge">
+ </noscript>
+EOTAG
+
+ my $tagtextSSL=<<EOTAGS;
+ <script type="text/javascript"
+ src="https://api-secure.recaptcha.net/challenge?k=$pubkey">
+ </script>
+
+ <noscript>
+ <iframe src="https://api-secure.recaptcha.net/noscript?k=$pubkey"
+ height="300" width="500" frameborder="0"></iframe><br>
+ <textarea name="recaptcha_challenge_field" rows="3" cols="40"></textarea>
+ <input type="hidden" name="recaptcha_response_field"
+ value="manual_challenge">
+ </noscript>
+EOTAGS
+
+ my $tagtext;
+
+ if ($config{signInSSL}) {
+ $tagtext = $tagtextSSL;
+ } else {
+ $tagtext = $tagtextPlain;
+ }
+
+ if ($form->title eq "signin") {
+ # Give up if module is unavailable to avoid
+ # needing to depend on it.
+ eval q{use LWP::UserAgent};
+ if ($@) {
+ debug("unable to load LWP::UserAgent, not enabling reCaptcha");
+ return;
+ }
+
+ die("To use reCAPTCHA you must get an API key from http://recaptcha.net/api/getkey")
+ unless $pubkey;
+ die("To use reCAPTCHA you must get an API key from http://recaptcha.net/api/getkey")
+ unless $privkey;
+ die("To use reCAPTCHA you must know the remote IP address")
+ unless $session->remote_addr();
+
+ $form->field(
+ name => "recaptcha",
+ label => "",
+ type => 'static',
+ comment => $tagtext,
+ required => 1,
+ message => "CAPTCHA verification failed",
+ );
+
+ # validate the captcha.
+ if ($form->submitted && $form->submitted eq "Login" &&
+ defined $form->cgi_param("recaptcha_challenge_field") &&
+ length $form->cgi_param("recaptcha_challenge_field") &&
+ defined $form->cgi_param("recaptcha_response_field") &&
+ length $form->cgi_param("recaptcha_response_field")) {
+
+ my $challenge = "invalid";
+ my $response = "invalid";
+ my $result = { is_valid => 0, error => 'recaptcha-not-tested' };
+
+ $form->field(name => "recaptcha",
+ message => "CAPTCHA verification failed",
+ required => 1,
+ validate => sub {
+ if ($challenge ne $form->cgi_param("recaptcha_challenge_field") or
+ $response ne $form->cgi_param("recaptcha_response_field")) {
+ $challenge = $form->cgi_param("recaptcha_challenge_field");
+ $response = $form->cgi_param("recaptcha_response_field");
+ debug("Validating: ".$challenge." ".$response);
+ $result = check_answer($privkey,
+ $session->remote_addr(),
+ $challenge, $response);
+ } else {
+ debug("re-Validating");
+ }
+
+ if ($result->{is_valid}) {
+ debug("valid");
+ return 1;
+ } else {
+ debug("invalid");
+ return 0;
+ }
+ });
+ }
+ }
+}
+
+# The following function is borrowed from
+# Captcha::reCAPTCHA by Andy Armstrong and are under the PERL Artistic License
+
+sub check_answer {
+ my ( $privkey, $remoteip, $challenge, $response ) = @_;
+
+ die
+ "To use reCAPTCHA you must get an API key from http://recaptcha.net/api/getkey"
+ unless $privkey;
+
+ die "For security reasons, you must pass the remote ip to reCAPTCHA"
+ unless $remoteip;
+
+ if (! ($challenge && $response)) {
+ debug("Challenge or response not set!");
+ return { is_valid => 0, error => 'incorrect-captcha-sol' };
+ }
+
+ my $ua = LWP::UserAgent->new();
+
+ my $resp = $ua->post(
+ 'http://api-verify.recaptcha.net/verify',
+ {
+ privatekey => $privkey,
+ remoteip => $remoteip,
+ challenge => $challenge,
+ response => $response
+ }
+ );
+
+ if ( $resp->is_success ) {
+ my ( $answer, $message ) = split( /\n/, $resp->content, 2 );
+ if ( $answer =~ /true/ ) {
+ debug("CAPTCHA valid");
+ return { is_valid => 1 };
+ }
+ else {
+ chomp $message;
+ debug("CAPTCHA failed: ".$message);
+ return { is_valid => 0, error => $message };
+ }
+ }
+ else {
+ debug("Unable to contact reCaptcha verification host!");
+ return { is_valid => 0, error => 'recaptcha-not-reachable' };
+ }
+}
+
+1;