Apache::AuthCookie(3) User Contributed Perl DocumentationApache::AuthCookie(3)NAMEApache::AuthCookie - Perl Authentication and Authorization via cookies
VERSION
version 3.18
SYNOPSIS
Make sure your mod_perl is at least 1.24, with StackedHandlers,
MethodHandlers, Authen, and Authz compiled in.
# In httpd.conf or .htaccess:
PerlModule Sample::Apache::AuthCookieHandler
PerlSetVar WhatEverPath /
PerlSetVar WhatEverLoginScript /login.pl
# use to alter how "require" directives are matched. Can be "Any" or "All".
# If its "Any", then you must only match Any of the "require" directives. If
# its "All", then you must match All of the require directives.
#
# Default: All
PerlSetVar WhatEverSatisfy Any
# The following line is optional - it allows you to set the domain
# scope of your cookie. Default is the current domain.
PerlSetVar WhatEverDomain .yourdomain.com
# Use this to only send over a secure connection
PerlSetVar WhatEverSecure 1
# Use this if you want user session cookies to expire if the user
# doesn't request a auth-required or recognize_user page for some
# time period. If set, a new cookie (with updated expire time)
# is set on every request.
PerlSetVar WhatEverSessionTimeout +30m
# to enable the HttpOnly cookie property, use HttpOnly.
# this is an MS extension. See
# http://msdn.microsoft.com/workshop/author/dhtml/httponly_cookies.asp
PerlSetVar WhatEverHttpOnly 1
# Usually documents are uncached - turn off here
PerlSetVar WhatEverCache 1
# Use this to make your cookies persistent (+2 hours here)
PerlSetVar WhatEverExpires +2h
# Use to make AuthCookie send a P3P header with the cookie
# see http://www.w3.org/P3P/ for details about what the value
# of this should be
PerlSetVar WhatEverP3P "CP=\"...\""
# These documents require user to be logged in.
<Location /protected>
AuthType Sample::Apache::AuthCookieHandler
AuthName WhatEver
PerlAuthenHandler Sample::Apache::AuthCookieHandler->authenticate
PerlAuthzHandler Sample::Apache::AuthCookieHandler->authorize
require valid-user
</Location>
# These documents don't require logging in, but allow it.
<FilesMatch "\.ok$">
AuthType Sample::Apache::AuthCookieHandler
AuthName WhatEver
PerlFixupHandler Sample::Apache::AuthCookieHandler->recognize_user
</FilesMatch>
# This is the action of the login.pl script above.
<Files LOGIN>
AuthType Sample::Apache::AuthCookieHandler
AuthName WhatEver
SetHandler perl-script
PerlHandler Sample::Apache::AuthCookieHandler->login
</Files>
DESCRIPTIONApache::AuthCookie allows you to intercept a user's first
unauthenticated access to a protected document. The user will be
presented with a custom form where they can enter authentication
credentials. The credentials are posted to the server where AuthCookie
verifies them and returns a session key.
The session key is returned to the user's browser as a cookie. As a
cookie, the browser will pass the session key on every subsequent
accesses. AuthCookie will verify the session key and re-authenticate
the user.
All you have to do is write a custom module that inherits from
AuthCookie. Your module is a class which implements two methods:
"authen_cred()"
Verify the user-supplied credentials and return a session key. The
session key can be any string - often you'll use some string
containing username, timeout info, and any other information you
need to determine access to documents, and append a one-way hash of
those values together with some secret key.
"authen_ses_key()"
Verify the session key (previously generated by "authen_cred()",
possibly during a previous request) and return the user ID. This
user ID will be fed to "$r->connection->user()" to set Apache's
idea of who's logged in.
By using AuthCookie versus Apache's built-in AuthBasic you can design
your own authentication system. There are several benefits.
1. The client doesn't *have* to pass the user credentials on every
subsequent access. If you're using passwords, this means that the
password can be sent on the first request only, and subsequent
requests don't need to send this (potentially sensitive)
information. This is known as "ticket-based" authentication.
2. When you determine that the client should stop using the
credentials/session key, the server can tell the client to delete
the cookie. Letting users "log out" is a notoriously impossible-
to-solve problem of AuthBasic.
3. AuthBasic dialog boxes are ugly. You can design your own HTML
login forms when you use AuthCookie.
4. You can specify the domain of a cookie using PerlSetVar commands.
For instance, if your AuthName is "WhatEver", you can put the
command
PerlSetVar WhatEverDomain .yourhost.com
into your server setup file and your access cookies will span all
hosts ending in ".yourhost.com".
5. You can optionally specify the name of your cookie using the
"CookieName" directive. For instance, if your AuthName is
"WhatEver", you can put the command
PerlSetVar WhatEverCookieName MyCustomName
into your server setup file and your cookies for this AuthCookie
realm will be named MyCustomName. Default is AuthType_AuthName.
6. By default users must satisfy ALL of the "require" directives. If
you want authentication to succeed if ANY "require" directives are
met, use the "Satisfy" directive. For instance, if your AuthName
is "WhatEver", you can put the command
PerlSetVar WhatEverSatisfy Any
into your server startup file and authentication for this realm
will succeed if ANY of the "require" directives are met.
This is the flow of the authentication handler, less the details of the
redirects. Two REDIRECT's are used to keep the client from displaying
the user's credentials in the Location field. They don't really change
AuthCookie's model, but they do add another round-trip request to the
client.
(-----------------------) +---------------------------------+
( Request a protected ) | AuthCookie sets custom error |
( page, but user hasn't )---->| document and returns |
( authenticated (no ) | FORBIDDEN. Apache abandons |
( session key cookie) ) | current request and creates sub |
(-----------------------) | request for the error document. |<-+
| Error document is a script that | |
| generates a form where the user | |
return | enters authentication | |
^------------------->| credentials (login & password). | |
/ \ False +---------------------------------+ |
/ \ | |
/ \ | |
/ \ V |
/ \ +---------------------------------+ |
/ Pass \ | User's client submits this form | |
/ user's \ | to the LOGIN URL, which calls | |
| credentials |<------------| AuthCookie->login(). | |
\ to / +---------------------------------+ |
\authen_cred/ |
\ function/ |
\ / |
\ / |
\ / +------------------------------------+ |
\ / return | Authen cred returns a session | +--+
V------------->| key which is opaque to AuthCookie.*| |
True +------------------------------------+ |
| |
+--------------------+ | +---------------+
| | | | If we had a |
V | V | cookie, add |
+----------------------------+ r | ^ | a Set-Cookie |
| If we didn't have a session| e |T / \ | header to |
| key cookie, add a | t |r / \ | override the |
| Set-Cookie header with this| u |u / \ | invalid cookie|
| session key. Client then | r |e / \ +---------------+
| returns session key with | n | / pass \ ^
| successive requests | | / session \ |
+----------------------------+ | / key to \ return |
| +-| authen_ses_key|------------+
V \ / False
+-----------------------------------+ \ /
| Tell Apache to set Expires header,| \ /
| set user to user ID returned by | \ /
| authen_ses_key, set authentication| \ /
| to our type (e.g. AuthCookie). | \ /
+-----------------------------------+ \ /
V
(---------------------) ^
( Request a protected ) |
( page, user has a )--------------+
( session key cookie )
(---------------------)
* The session key that the client gets can be anything you want. For
example, encrypted information about the user, a hash of the
username and password (similar in function to Digest
authentication), or the user name and password in plain text
(similar in function to HTTP Basic authentication).
The only requirement is that the authen_ses_key function that you
create must be able to determine if this session_key is valid and
map it back to the originally authenticated user ID.
METHODS
"Apache::AuthCookie" has several methods you should know about. Here
is the documentation for each. =)
· authenticate()
This method is one you'll use in a server config file (httpd.conf,
.htaccess, ...) as a PerlAuthenHandler. If the user provided a
session key in a cookie, the "authen_ses_key()" method will get
called to check whether the key is valid. If not, or if there is
no key provided, we redirect to the login form.
· authorize()
This will step through the "require" directives you've given for
protected documents and make sure the user passes muster. The
"require valid-user" and "require user joey-jojo" directives are
handled for you. You can implement custom directives, such as
"require species hamster", by defining a method called "species()"
in your subclass, which will then be called. The method will be
called as "$r->species($r, $args)", where $args is everything on
your "require" line after the word "species". The method should
return OK on success and FORBIDDEN on failure.
· authen_cred()
You must define this method yourself in your subclass of
"Apache::AuthCookie". Its job is to create the session key that
will be preserved in the user's cookie. The arguments passed to it
are:
sub authen_cred ($$\@) {
my $self = shift; # Package name (same as AuthName directive)
my $r = shift; # Apache request object
my @cred = @_; # Credentials from login form
...blah blah blah, create a session key...
return $session_key;
}
The only limitation on the session key is that you should be able
to look at it later and determine the user's username. You are
responsible for implementing your own session key format. A
typical format is to make a string that contains the username, an
expiration time, whatever else you need, and an MD5 hash of all
that data together with a secret key. The hash will ensure that
the user doesn't tamper with the session key. More info in the
Eagle book.
· authen_ses_key()
You must define this method yourself in your subclass of
Apache::AuthCookie. Its job is to look at a session key and
determine whether it is valid. If so, it returns the username of
the authenticated user.
sub authen_ses_key ($$$) {
my ($self, $r, $session_key) = @_;
...blah blah blah, check whether $session_key is valid...
return $ok ? $username : undef;
}
Optionally, return an array of 2 or more items that will be passed
to method custom_errors. It is the responsibility of this method to
return the correct response to the main Apache module.
· custom_errors($r,@_)
Note: this interface is experimental.
This method handles the server response when you wish to access the
Apache custom_response method. Any suitable response can be used.
this is particularly useful when implementing 'by directory' access
control using the user authentication information. i.e.
/restricted
/one user is allowed access here
/two not here
/three AND here
The authen_ses_key method would return a normal response when the
user attempts to access 'one' or 'three' but return (NOT_FOUND,
'File not found') if an attempt was made to access subdirectory
'two'. Or, in the case of expired credentials, (AUTH_REQUIRED,'Your
session has timed out, you must login again').
example 'custom_errors'
sub custom_errors {
my ($self,$r,$CODE,$msg) = @_;
# return custom message else use the server's standard message
$r->custom_response($CODE, $msg) if $msg;
return($CODE);
}
where CODE is a valid code from Apache::Constants
· login()
This method handles the submission of the login form. It will call
the "authen_cred()" method, passing it $r and all the submitted
data with names like "credential_#", where # is a number. These
will be passed in a simple array, so the prototype is
"$self->authen_cred($r, @credentials)". After calling
"authen_cred()", we set the user's cookie and redirect to the URL
contained in the "destination" submitted form field.
· login_form()
This method is responsible for displaying the login form. The
default implementation will make an internal redirect and display
the URL you specified with the "PerlSetVar WhatEverLoginScript"
configuration directive. You can overwrite this method to provide
your own mechanism.
· logout()
This is simply a convenience method that unsets the session key for
you. You can call it in your logout scripts. Usually this looks
like "$r->auth_type->logout($r);".
· send_cookie($session_key)
By default this method simply sends out the session key you give
it. If you need to change the default behavior (perhaps to update
a timestamp in the key) you can override this method.
· recognize_user()
If the user has provided a valid session key but the document isn't
protected, this method will set "$r->connection->user" anyway. Use
it as a PerlFixupHandler, unless you have a better idea.
· key()
This method will return the current session key, if any. This can
be handy inside a method that implements a "require" directive
check (like the "species" method discussed above) if you put any
extra information like clearances or whatever into the session key.
· untaint_destination($self, $uri)
This method returns a modified version of the destination parameter
before embedding it into the response header. Per default it
escapes CR, LF and TAB characters of the uri to avoid certain types
of security attacks. You can override it to more limit the allowed
destinations, e.g., only allow relative uris, only special hosts or
only limited set of characters.
EXAMPLE
For an example of how to use Apache::AuthCookie, you may want to check
out the test suite, which runs AuthCookie through a few of its paces.
The documents are located in t/eg/, and you may want to peruse t/real.t
to see the generated httpd.conf file (at the bottom of real.t) and
check out what requests it's making of the server (at the top of
real.t).
THE LOGIN SCRIPT
You will need to create a login script (called login.pl above) that
generates an HTML form for the user to fill out. You might generate
the page using an Apache::Registry script, or an HTML::Mason component,
or perhaps even using a static HTML page. It's usually useful to
generate it dynamically so that you can define the 'destination' field
correctly (see below).
The following fields must be present in the form:
1. The ACTION of the form must be /LOGIN (or whatever you defined in
your server configuration as handled by the ->login() method - see
example in the SYNOPSIS section).
2. The various user input fields (username, passwords, etc.) must be
named 'credential_0', 'credential_1', etc. on the form. These will
get passed to your authen_cred() method.
3. You must define a form field called 'destination' that tells
AuthCookie where to redirect the request after successfully logging
in. Typically this value is obtained from "$r->prev->uri". See
the login.pl script in t/eg/.
In addition, you might want your login page to be able to tell why the
user is being asked to log in. In other words, if the user sent bad
credentials, then it might be useful to display an error message saying
that the given username or password are invalid. Also, it might be
useful to determine the difference between a user that sent an invalid
auth cookie, and a user that sent no auth cookie at all. To cope with
these situations, AuthCookie will set
"$r->subprocess_env('AuthCookieReason')" to one of the following
values.
no_cookie
The user presented no cookie at all. Typically this means the user
is trying to log in for the first time.
bad_cookie
The cookie the user presented is invalid. Typically this means
that the user is not allowed access to the given page.
bad_credentials
The user tried to log in, but the credentials that were passed are
invalid.
You can examine this value in your login form by examining
"$r->prev->subprocess_env('AuthCookieReason')" (because it's a sub-
request).
Of course, if you want to give more specific information about why
access failed when a cookie is present, your "authen_ses_key()" method
can set arbitrary entries in "$r->subprocess_env".
THE LOGOUT SCRIPT
If you want to let users log themselves out (something that can't be
done using Basic Auth), you need to create a logout script. For an
example, see t/htdocs/docs/logout.pl. Logout scripts may want to take
advantage of AuthCookie's "logout()" method, which will set the proper
cookie headers in order to clear the user's cookie. This usually looks
like "$r->auth_type->logout($r);".
Note that if you don't necessarily trust your users, you can't count on
cookie deletion for logging out. You'll have to expire some server-
side login information too. AuthCookie doesn't do this for you, you
have to handle it yourself.
ABOUT SESSION KEYS
Unlike the sample AuthCookieHandler, you have you verify the user's
login and password in "authen_cred()", then you do something like:
my $date = localtime;
my $ses_key = MD5->hexhash(join(';', $date, $PID, $PAC));
save $ses_key along with the user's login, and return $ses_key.
Now "authen_ses_key()" looks up the $ses_key passed to it and returns
the saved login. I use Oracle to store the session key and retrieve it
later, see the ToDo section below for some other ideas.
TO DO
· It might be nice if the logout method could accept some parameters
that could make it easy to redirect the user to another URI, or
whatever. I'd have to think about the options needed before I
implement anything, though.
HISTORY
Originally written by Eric Bartley <bartley@purdue.edu>
versions 2.x were written by Ken Williams <ken@forum.swarthmore.edu>
SEE ALSOperl(1), mod_perl(1), Apache(1).
AUTHOR
Michael Schout <mschout@cpan.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2000 by Ken Williams.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
BUGS
Please report any bugs or feature requests to
bug-apache-authcookie@rt.cpan.org or through the web interface at:
http://rt.cpan.org/Public/Dist/Display.html?Name=Apache-AuthCookie
perl v5.18.1 2011-01-24 Apache::AuthCookie(3)
