ikiwiki/doc/plugins/contrib/unixauth.mdwn

[[!template id=plugin name=unixauth core=0 author="[[schmonz]]"]]
[[!tag type/auth]]

This plugin authenticates users against the Unix user database. It presents a similar UI to [[plugins/passwordauth]], but simpler, as there's no need to be able to register or change one's password.

To authenticate, either [checkpassword](http://cr.yp.to/checkpwd.html) or [pwauth](http://www.unixpapa.com/pwauth/) must be installed and configured. `checkpassword` is strongly preferred. If your web server runs as an unprivileged user -- as it darn well should! -- then `checkpassword` needs to be setuid root. (Or your ikiwiki CGI wrapper, I guess, but don't do that.) Other checkpassword implementations are available, notably [checkpassword-pam](http://checkpasswd-pam.sourceforge.net/).

Config variables that affect the behavior of `unixauth`:

* `unixauth_type`: defaults to unset, can be "checkpassword" or "pwauth"
* `unixauth_command`: defaults to unset, should contain the full path and any arguments
* `unixauth_requiressl`: defaults to 1, can be 0
* `sslcookie`: needs to be 1 if `unixauth_requiressl` is 1 (perhaps this should be done automatically?)

__Security__: [As with passwordauth](/security/#index14h2), be wary of sending usernames and passwords in cleartext. Unlike passwordauth, sniffing `unixauth` credentials can get an attacker much further than mere wiki access. Therefore, this plugin defaults to not even _displaying_ the login form fields unless we're running under SSL. Nobody should be able to do anything remotely dumb until the admin has done at least a little thinking. After that, dumb things are always possible. ;-)

`unixauth` tests for the presence of the `HTTPS` environment variable. `Wrapper.pm` needs to be tweaked to pass it through; without that, the plugin fails closed.

[[!toggle id="diff" text="Wrapper.pm.diff"]]

[[!toggleable id="diff" text="""

    --- Wrapper.pm.orig 2008-07-29 00:09:10.000000000 -0400
    +++ Wrapper.pm
    @@ -28,7 +28,7 @@ sub gen_wrapper () {
        my @envsave;
        push @envsave, qw{REMOTE_ADDR QUERY_STRING REQUEST_METHOD REQUEST_URI
                       CONTENT_TYPE CONTENT_LENGTH GATEWAY_INTERFACE
    -                  HTTP_COOKIE REMOTE_USER} if $config{cgi};
    +                  HTTP_COOKIE REMOTE_USER HTTPS} if $config{cgi};
        my $envsave="";
        foreach my $var (@envsave) {
                $envsave.=<<"EOF"

"""]]

[[!toggle id="code" text="unixauth.pm"]]

[[!toggleable id="code" text="""

    #!/usr/bin/perl
    # Ikiwiki unixauth authentication.
    package IkiWiki::Plugin::unixauth;
    
    use warnings;
    use strict;
    use IkiWiki 2.00;
    
    sub import {
        hook(type => "getsetup", id => "unixauth", call => \&getsetup);
            hook(type => "formbuilder_setup", id => "unixauth",
                call => \&formbuilder_setup);
            hook(type => "formbuilder", id => "unixauth",
                call => \&formbuilder);
        hook(type => "sessioncgi", id => "unixauth", call => \&sessioncgi);
    }
    
    sub getsetup () {
        return
        unixauth_type => {
                type => "string",
                example => "checkpassword",
                description => "type of authenticator; can be 'checkpassword' or 'pwauth'",
                safe => 0,
                rebuild => 1,
        },
        unixauth_command => {
                type => "string",
                example => "/path/to/checkpassword",
                description => "full path and any arguments",
                safe => 0,
                rebuild => 1,
        },
        unixauth_requiressl => {
                type => "boolean",
                example => "1",
                description => "require SSL? strongly recommended",
                safe => 0,
                rebuild => 1,
        },
        plugin => {
                description => "Unix user authentication",
                safe => 0,
                rebuild => 1,
        },
    }
    
    # Checks if a string matches a user's password, and returns true or false.
    sub checkpassword ($$;$) {
        my $user=shift;
        my $password=shift;
        my $field=shift || "password";
    
        # It's very important that the user not be allowed to log in with
        # an empty password!
        if (! length $password) {
                return 0;
        }
    
        my $ret=0;
        if (! exists $config{unixauth_type}) {
                # admin needs to carefully think over his configuration
                return 0;
        }
        elsif ($config{unixauth_type} eq "checkpassword") {
                open UNIXAUTH, "|$config{unixauth_command} true 3<&0" or die("Could not run $config{unixauth_type}");
                print UNIXAUTH "$user\0$password\0Y123456\0";
                close UNIXAUTH;
                $ret=!($?>>8);
        }
        elsif ($config{unixauth_type} eq "pwauth") {
                open UNIXAUTH, "|$config{unixauth_command}" or die("Could not run $config{unixauth_type}");
                print UNIXAUTH "$user\n$password\n";
                close UNIXAUTH;
                $ret=!($?>>8);
        }
        else {
                # no such authentication type
                return 0;
        }
    
        if ($ret) {
            my $userinfo=IkiWiki::userinfo_retrieve();
            if (! length $user || ! defined $userinfo ||
                ! exists $userinfo->{$user} || ! ref $userinfo->{$user}) {
                    IkiWiki::userinfo_setall($user, {
                        'email' => '',
                        'regdate' => time,
                    });
            }
        }
    
        return $ret;
    }
    
    sub formbuilder_setup (@) {
        my %params=@_;
    
        my $form=$params{form};
        my $session=$params{session};
        my $cgi=$params{cgi};
    
        # if not under SSL, die before even showing a login form,
        # unless the admin explicitly says it's fine
        if (! exists $config{unixauth_requiressl}) {
                $config{unixauth_requiressl} = 1;
        }
        if ($config{unixauth_requiressl}) {
            if ((! $config{sslcookie}) || (! exists $ENV{'HTTPS'})) {
                die("SSL required to login. Contact your administrator.<br>");
            }
        }
    
        if ($form->title eq "signin") {
                $form->field(name => "name", required => 0);
                $form->field(name => "password", type => "password", required => 0);
                
                if ($form->submitted) {
                        my $submittype=$form->submitted;
                        # Set required fields based on how form was submitted.
                        my %required=(
                                "Login" => [qw(name password)],
                        );
                        foreach my $opt (@{$required{$submittype}}) {
                                $form->field(name => $opt, required => 1);
                        }
        
                        # Validate password against name for Login.
                        if ($submittype eq "Login") {
                                $form->field(
                                        name => "password",
                                        validate => sub {
                                                checkpassword($form->field("name"), shift);
                                        },
                                );
                        }
                        
                        # XXX is this reachable? looks like no
                        elsif ($submittype eq "Login") {
                                $form->field( 
                                        name => "name",
                                        validate => sub {
                                                my $name=shift;
                                                length $name &&
                                                IkiWiki::userinfo_get($name, "regdate");
                                        },
                                );
                        }
                }
                else {
                        # First time settings.
                        $form->field(name => "name");
                        if ($session->param("name")) {
                                $form->field(name => "name", value => $session->param("name"));
                        }
                }
        }
        elsif ($form->title eq "preferences") {
                $form->field(name => "name", disabled => 1, 
                        value => $session->param("name"), force => 1,
                        fieldset => "login");
                $form->field(name => "password", disabled => 1, type => "password",
                        fieldset => "login"),
        }
    }
    
    sub formbuilder (@) {
        my %params=@_;
    
        my $form=$params{form};
        my $session=$params{session};
        my $cgi=$params{cgi};
        my $buttons=$params{buttons};
    
        if ($form->title eq "signin") {
                if ($form->submitted && $form->validate) {
                        if ($form->submitted eq 'Login') {
                                $session->param("name", $form->field("name"));
                                IkiWiki::cgi_postsignin($cgi, $session);
                        }
                }
        }
        elsif ($form->title eq "preferences") {
                if ($form->submitted eq "Save Preferences" && $form->validate) {
                        my $user_name=$form->field('name');
                }
        }
    }
    
    sub sessioncgi ($$) {
        my $q=shift;
        my $session=shift;
    }
    
    1

"""]]