Cyber Sprocket Labs > Apache2-AuthCookieDBImg > Apache2::AuthCookieDBImg

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Module Version: 2.2   Source  

NAME ^

Apache2::AuthCookieDBImg

PURPOSE ^

An AuthCookie module backed by a DBI database with second level authentication via image matching. This is very simple image authentication scheme that is only meant to prevent robotic logins to a web page by adding a 2nd level of authentication.

SYNOPSIS ^

    # In httpd.conf or .htaccess
        
    PerlModule Apache2::AuthCookieDBImg
    PerlSetVar WhatEverPath /
    PerlSetVar WhatEverLoginScript /login.pl

    # Optional, to share tickets between servers.
    PerlSetVar WhatEverDomain .domain.com
    
    # These must be set
    PerlSetVar WhatEverDBI_DSN "DBI:mysql:database=test"
    PerlSetVar WhatEverDBI_SecretKey "489e5eaad8b3208f9ad8792ef4afca73598ae666b0206a9c92ac877e73ce835c"

    # These are optional, the module sets sensible defaults.
    PerlSetVar WhatEverDBI_User "nobody"
    PerlSetVar WhatEverDBI_Password "password"

    PerlSetVar WhatEverDBI_UsersTable "users"
    PerlSetVar WhatEverDBI_UserField "user"
    PerlSetVar WhatEverDBI_PasswordField "password"
    PerlSetVar WhatEverDBI_CryptType "none"

    PerlSetVar WhatEverDBI_GroupsTable "groups"
    PerlSetVar WhatEverDBI_GroupField "grp"
    PerlSetVar WhatEverDBI_GroupUserField "user"

         # These are optional, if all 3 are set
    # Image verification is performed
         # The word is passed in via credential_2
         # The key is passed in via credential_3
         #
    PerlSetVar WhatEverDBI_ImgTable             "images"
    PerlSetVar WhatEverDBI_ImgWordField         "imageword"
    PerlSetVar WhatEverDBI_ImgKeyField  "imagekey"

    PerlSetVar WhatEverDBI_EncryptionType "none"
    PerlSetVar WhatEverDBI_SessionLifetime 00-24-00-00

    # Protected by AuthCookieDBImg.
    <Directory /www/domain.com/authcookiedbimg>
        AuthType Apache2::AuthCookieDBImg
        AuthName WhatEver
        PerlAuthenHandler Apache2::AuthCookieDBImg->authenticate
        PerlAuthzHandler Apache2::AuthCookieDBImg->authorize
        require valid-user
        # or you can require users:
        require user jacob
        # You can optionally require groups.
        require group system
    </Directory>

    # Login location.
    <Files LOGIN>
        AuthType Apache2::AuthCookieDBImg
        AuthName WhatEver
        SetHandler perl-script
        PerlHandler Apache2::AuthCookieDBImg->login
    </Files>

DESCRIPTION ^

This module is an authentication handler that uses the basic mechanism provided by Apache2::AuthCookie with a DBI database for ticket-based protection. It is based on two tokens being provided, a username and password, which can be any strings (there are no illegal characters for either). The username is used to set the remote user as if Basic Authentication was used.

On an attempt to access a protected location without a valid cookie being provided, the module prints an HTML login form (produced by a CGI or any other handler; this can be a static file if you want to always send people to the same entry page when they log in). This login form has fields for username and password. On submitting it, the username and password are looked up in the DBI database. The supplied password is checked against the password in the database; the password in the database can be plaintext, or a crypt() or md5_hex() checksum of the password. If this succeeds, the user is issued a ticket. This ticket contains the username, an issue time, an expire time, and an MD5 checksum of those and a secret key for the server. It can optionally be encrypted before returning it to the client in the cookie; encryption is only useful for preventing the client from seeing the expire time. If you wish to protect passwords in transport, use an SSL-encrypted connection. The ticket is given in a cookie that the browser stores.

After a login the user is redirected to the location they originally wished to view (or to a fixed page if the login "script" was really a static file).

On this access and any subsequent attempt to access a protected document, the browser returns the ticket to the server. The server unencrypts it if encrypted tickets are enabled, then extracts the username, issue time, expire time and checksum. A new checksum is calculated of the username, issue time, expire time and the secret key again; if it agrees with the checksum that the client supplied, we know that the data has not been tampered with. We next check that the expire time has not passed. If not, the ticket is still good, so we set the username.

Authorization checks then check that any "require valid-user" or "require user jacob" settings are passed. Finally, if a "require group foo" directive was given, the module will look up the username in a groups database and check that the user is a member of one of the groups listed. If all these checks pass, the document requested is displayed.

If a ticket has expired or is otherwise invalid it is cleared in the browser and the login form is shown again.

IMAGE MATCHING

The image matching only occurs if all 3 of the following directives appear in the Apache configuration file: PerlSetVar WhatEverDBI_ImgTable "images" PerlSetVar WhatEverDBI_ImgWordField "imageword" PerlSetVar WhatEverDBI_ImgKeyField "imagekey"

The first ImgTable var is the DBI table that we will use to store our image key + word pairs. The key field is set by the second var, the word is the third var.

Your login form should set the 2 required fields for ALL AuthCookieDBI login forms: Your login ID: <input type="text" name="credential_0" value=""> Your password: <input type="password" name="credential_1" value="">

PLUS two additional fields for image processing: The image says: <input type="text" name="credential_2" value=""> <input type="hidden" name="credential_3" value="a_random_key">

The login form should also have an image displayed that shows the word that we are expecting to receive via credential_2 as semi-obscured text. Typically the image that is displayed is selected at random (provide your own image randomizer here) with the hidden credential_3 field also being set via the same random selector so that we can lookup the word in the images table via the key we get in credential_3.

For example, my randomizer (written in perl and called via a perl page template processor similar to Template::Toolkit) will spit out my image coding and hidden field coding into my HTML page selecting a random image + key from the images table. For example, the output from my perl randomizer spits out: <img src="/images/dbimg/junk.png"><input type="hidden" name="credential_3" value="1">

To make the work of the randomizer easier I create my images table like this: create table images ( imagekey serial, imageurl char(128), imageword char(20));

And load it up like this: inssert into images (imageurl,imageword) values ('/images/dbimg/junk.png','saywhat?');

Then create an image named junk.png and put it in my web server /images/dbimg folder. The text on the image has a background picture plus the word "saywhat?" across the front.

The randomizer just looks up the imageurl and imagekey in the database and spits out the appropriate HTML code. ApacheCookieDBImg then does a reverse operation, looking up the imageword based on the key.

CAVEATS ^

This is not a truly random image, so it is not overly secure. The initial idea is just to thwart stupid bots. Someone could easily visit the site and build a map of image sources and the matching words. i.e. when credential_3 == 1 the word is always "saywhat?".

Not fool-proof, just and extra level of bot protection.

APACHE CONFIGURATION DIRECTIVES ^

All configuration directives for this module are passed in PerlSetVars. These PerlSetVars must begin with the AuthName that you are describing, so if your AuthName is PrivateBankingSystem they will look like:

    PerlSetVar PrivateBankingSystemDBI_DSN "DBI:mysql:database=banking"

See also Apache2::Authcookie for the directives required for any kind of Apache2::AuthCookie-based authentication system.

In the following descriptions, replace "WhatEver" with your particular AuthName. The available configuration directives are as follows:

WhatEverDBI_DSN

Specifies the DSN for DBI for the database you wish to connect to retrieve user information. This is required and has no default value.

WhateverDBI_SecretKey

Specifies the secret key for this auth scheme. This should be a long random string. This should be secret; either make the httpd.conf file only readable by root, or put the PerlSetVar in a file only readable by root and include it.

This is required and has no default value. (NOTE: In AuthCookieDBImg versions 1.22 and earlier the secret key either could be or was required to be in a seperate file with the path configured with PerlSetVar WhateverDBI_SecretKeyFile, as of version 2.0 this is not possible, you must put the secret key in the Apache configuration directly, either in the main httpd.conf file or in an included file. You might wish to make the file not world-readable. Also, make sure that the Perl environment variables are not publically available, for example via the /perl-status handler.) See also "COMPATIBILITY" in this man page.

WhatEverDBI_User

The user to log into the database as. This is not required and defaults to undef.

WhatEverDBI_Password

The password to use to access the database. This is not required and defaults to undef.

Make sure that the Perl environment variables are not publically available, for example via the /perl-status handler since the password could be exposed.

WhatEverDBI_UsersTable

The table that user names and passwords are stored in. This is not required and defaults to 'users'.

WhatEverDBI_UserField

The field in the above table that has the user name. This is not required and defaults to 'user'.

WhatEverDBI_PasswordField

The field in the above table that has the password. This is not required and defaults to 'password'.

WhatEverDBI_CryptType

What kind of hashing is used on the password field in the database. This can be 'none', 'crypt', or 'md5'. This is not required and defaults to 'none'.

WhatEverDBI_GroupsTable

The table that has the user / group information. This is not required and defaults to 'groups'.

WhatEverDBI_GroupField

The field in the above table that has the group name. This is not required and defaults to 'grp' (to prevent conflicts with the SQL reserved word 'group').

WhatEverDBI_GroupUserField

The field in the above table that has the user name. This is not required and defaults to 'user'.

WhatEverDBI_ImgTable

The table that has the image to word mapping information. This is not required and defaults to 'groups'.

WhatEverDBI_GroupField

The field in the above table that has the group name. This is not required and defaults to 'grp' (to prevent conflicts with the SQL reserved word 'group').

WhatEverDBI_GroupUserField

The field in the above table that has the user name. This is not required and defaults to 'user'.

WhatEverDBI_EncryptionType

What kind of encryption to use to prevent the user from looking at the fields in the ticket we give them. This is almost completely useless, so don''t switch it on unless you really know you need it. It does not provide any protection of the password in transport; use SSL for that. It can be 'none', 'des', 'idea', 'blowfish', or 'blowfish_pp'.

This is not required and defaults to 'none'.

WhatEverDBI_SessionLifetime

How long tickets are good for after being issued. Note that presently Apache2::AuthCookie does not set a client-side expire time, which means that most clients will only keep the cookie until the user quits the browser. However, if you wish to force people to log in again sooner than that, set this value. This can be 'forever' or a life time specified as:

    DD-hh-mm-ss -- Days, hours, minute and seconds to live.

This is not required and defaults to '00-24-00-00' or 24 hours.

WhatEverDBI_SessionModule

Which Apache2::Session module to use for persistent sessions. For example, a value could be "Apache2::Session::MySQL". The DSN will be the same as used for authentication. The session created will be stored in $r->pnotes( WhatEver ).

If you use this, you should put:

    PerlModule Apache2::Session::MySQL

(or whatever the name of your session module is) in your httpd.conf file, so it is loaded.

If you are using this directive, you can timeout a session on the server side by deleting the user''s session. Authentication will then fail for them.

This is not required and defaults to none, meaning no session objects will be created.

WhatEverDBI_SessionActiveReset

Force the session cookie expiration to reset whenever user activity is detected (new page loaded, etc.). This allows a low expiration time (5 minutes) that logs off when a session is inactive. Active sessions will be granted more time each time they perform an action.

This is not required and defaults to 0 (Expire X minutes after initial logon).

SUBCLASSING ^

You can subclass this module to override public functions and change their behaviour.

extra_session_info()

This method returns extra fields to add to the session key. It should return a string consisting of ":field1:field2:field3" (where each field is preceded by a colon).

The default implementation does nothing.

DATABASE SCHEMAS ^

For this module to work, the database tables must be laid out at least somewhat according to the following rules: the user field must be a primary key so there is only one row per user; the password field must be NOT NULL. If you're using MD5 passwords the password field must be 32 characters long to allow enough space for the output of md5_hex(). If you're using crypt() passwords you need to allow 13 characters.

An minimal CREATE TABLE statement might look like:

    CREATE TABLE users (
        user VARCHAR(16) PRIMARY KEY,
        password VARCHAR(32) NOT NULL
    )

For the groups table, the access table is actually going to be a join table between the users table and a table in which there is one row per group if you have more per-group data to store; if all you care about is group membership though, you only need this one table. The only constraints on this table are that the user and group fields be NOT NULL.

A minimal CREATE TABLE statement might look like:

    CREATE TABLE groups (
        grp VARCHAR(16) NOT NULL,
        user VARCHAR(16) NOT NULL
    )

COPYRIGHT ^

 Copyright (C) 2006 Charleston Software Associates (www.CharlestonSW.com)

LICENSE ^

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

AUTHOR ^

Lance Cleveland, Charleston Software Associates <info@charlestonsw.com>

HISTORY ^

v2.1 - February 2006 Significant portions based on AuthCookieDBI v2.03

v2.2 - April 2006 Added SessionActiveReset configuration variable (reset logout timer)

REQUIRES ^

Apache::DBI Apache2::AuthCookie Apache2::Const Apache2::ServerUtil Date::Calc Digest::MD5

Apache2::Session (if using sessions) Cipher::CBC (if using CBC Ciphers)

SEE ALSO ^

Latest version: http://search.cpan.org/search?query=Apache%3A%3AAuthCookieDBImg&mode=all

Apache2::AuthCookieDBI(1) Apache2::AuthCookie(1) Apache2::Session(1)

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