Apache-AuthCookie
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lib/Apache2_4/AuthCookie.pm view on Meta::CPAN
</Location>
# These documents don't require logging in, but allow it.
<FilesMatch "\.ok$">
AuthType Sample::Apache2::AuthCookieHandler
AuthName WhatEver
PerlFixupHandler Sample::Apache2::AuthCookieHandler->recognize_user
</FilesMatch>
# This is the action of the login.pl script above.
<Files LOGIN>
AuthType Sample::Apache2::AuthCookieHandler
AuthName WhatEver
SetHandler perl-script
PerlResponseHandler Sample::Apache2::AuthCookieHandler->login
</Files>
=head1 DESCRIPTION
This module is for C<mod_perl> version 2 for C<Apache> version 2.4.x. If you
are running mod_perl version 1, you need B<Apache::AuthCookie> instead. If you
are running C<Apache> 2.0.0-2.2.x, you need B<Apache2::AuthCookie> instead.
B<Apache2_4::AuthCookie> allows you to intercept a user's first unauthenticated
access to a protected document. The user will be presented with a custom form
where they can enter authentication credentials. The credentials are posted to
the server where AuthCookie verifies them and returns a session key.
The session key is returned to the user's browser as a cookie. As a cookie, the
browser will pass the session key on every subsequent accesses. AuthCookie will
verify the session key and re-authenticate the user.
All you have to do is write a custom module that inherits from AuthCookie.
Your module is a class which implements two methods:
=over 4
=item C<authen_cred()>
Verify the user-supplied credentials and return a session key. The session key
can be any string - often you'll use some string containing username, timeout
info, and any other information you need to determine access to documents, and
append a one-way hash of those values together with some secret key.
=item C<authen_ses_key()>
Verify the session key (previously generated by C<authen_cred()>, possibly
during a previous request) and return the user ID. This user ID will be fed to
C<$r-E<gt>user()> to set Apache's idea of who's logged in.
=back
By using AuthCookie versus Apache's built-in AuthBasic you can design your own
authentication system. There are several benefits.
=over 4
=item 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.
=item 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.
=item 3.
AuthBasic dialog boxes are ugly. You can design your own HTML login forms when
you use AuthCookie.
=item 4.
You can specify the domain of a cookie using C<PerlSetVar> commands. For
instance, if your AuthName is C<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 C<.yourhost.com>.
=item 5.
You can optionally specify the name of your cookie using the C<CookieName>
directive. For instance, if your AuthName is C<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.
=back
This is the flow of the authentication handler, less the details of the
redirects. Two HTTP_MOVED_TEMPORARILY'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 ) | HTTP_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.
=head1 METHODS
=head2 authen_cred()
You must define this method yourself in your subclass of
C<Apache2_4::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 ($$\@) {
my $self = shift; # Package name (same as AuthName directive)
my $r = shift; # Apache request object
my @cred = @_; # Credentials from login form
...blah blah blah, create a session key...
return $session_key;
}
The only limitation on the session key is that you should be able to look at it
later and determine the user's username. You are responsible for implementing
your own session key format. A typical format is to make a string that
contains the username, an expiration time, whatever else you need, and an MD5
hash of all that data together with a secret key. The hash will ensure that
the user doesn't tamper with the session key.
=head2 authen_ses_key()
You must define this method yourself in your subclass of
C<Apache2_4::AuthCookie>. Its job is to look at a session key and determine
whether it is valid. If so, it returns the username of the authenticated user.
sub authen_ses_key ($$$) {
my ($self, $r, $session_key) = @_;
...blah blah blah, check whether $session_key is valid...
return $ok ? $username : undef;
}
Optionally, return an array of 2 or more items that will be passed to method
custom_errors. It is the responsibility of this method to return the correct
response to the main Apache module.
=head2 custom_errors($r,@_)
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
lib/Apache2_4/AuthCookie.pm view on Meta::CPAN
=item *
Due to the way HTTP works, cookies cannot contain non-ASCII characters.
Because of this, if you are including the username in your generated session
key, you will need to escape any non-ascii characters in the session key
returned by L<authen_cred()>.
=item *
Similarly, you must reverse this escaping process in L<authen_ses_key()> and
return a L<Encode/decode()> decoded username. If your L<authen_cred()>
function already only generates ASCII-only session keys then you do not need to
worry about any of this.
=item *
The value stored in C<< $r-E<gt>user >> will be encoded using bytes semantics
using the configured B<Encoding>. If you want the decoded user value, use
L<decoded_user()> instead.
=back
=head2 Requires
You can also specify what the charset is of the Apache C<< $r-E<gt>requires >>
data is by setting C<< ${auth_name}RequiresEncoding >> in httpd.conf.
E.g.:
PerlSetVar WhatEverRequiresEncoding UTF-8
This will make it so that AuthCookie will decode your C<requires> directives
using the configured character set. You really only need to do this if you
have used non-ascii characters in any of your C<requires> directives in
httpd.conf. e.g.:
requires user programmør
=head1 THE LOGIN SCRIPT
You will need to create a login script (called login.pl above) that generates
an HTML form for the user to fill out. You might generate the page using a
ModPerl::Registry script, a HTML::Mason component, an Apache handler, or
perhaps even using a static HTML page. It's usually useful to generate it
dynamically so that you can define the 'destination' field correctly (see
below).
The following fields must be present in the form:
=over 4
=item 1.
The ACTION of the form must be /LOGIN (or whatever you defined in your
server configuration as handled by the C<-E<gt>login()> method - see example in
the SYNOPSIS section).
=item 2.
The various user input fields (username, passwords, etc.) must be named
'credential_0', 'credential_1', etc. on the form. These will get passed to
your C<authen_cred()> method.
=item 3.
You must define a form field called 'destination' that tells AuthCookie where
to redirect the request after successfully logging in. Typically this value is
obtained from C<$r-E<gt>prev-E<gt>uri>. See the login.pl script in t/eg/.
=back
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, B<AuthCookie> will set
C<$r-E<gt>subprocess_env('AuthCookieReason')> to one of the following values.
=over 4
=item I<no_cookie>
The user presented no cookie at all. Typically this means the user is
trying to log in for the first time.
=item I<bad_cookie>
The cookie the user presented is invalid. Typically this means that the user
is not allowed access to the given page.
=item I<bad_credentials>
The user tried to log in, but the credentials that were passed are invalid.
=back
You can examine this value in your login form by examining
C<$r-E<gt>prev-E<gt>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 C<authen_ses_key()> method can set
arbitrary entries in C<$r-E<gt>subprocess_env>.
=head1 THE LOGOUT SCRIPT
If you want to let users log themselves out (something that can't be done using
Basic Auth), you need to create a logout script. For an example, see
t/htdocs/docs/logout.pl. Logout scripts may want to take advantage of
AuthCookie's C<logout()> method, which will set the proper cookie headers in
order to clear the user's cookie. This usually looks like
C<$r-E<gt>auth_type-E<gt>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.
=head1 ABOUT SESSION KEYS
Unlike the sample AuthCookieHandler, you have you verify the user's login and
password in C<authen_cred()>, then you do something like:
my $date = localtime;
my $ses_key = Digest::SHA::sha256_hex(join(';', $date, $PID, $PAC));
save C<$ses_key> along with the user's login, and return C<$ses_key>.
Now C<authen_ses_key()> looks up the C<$ses_key> passed to it and returns the
saved login. I use a database to store the session key and retrieve it later.
=head1 FREQUENTLY ASKED QUESTIONS
=over 4
=item *
I upgraded to Apache 2.4 and now AuthCookie doesn't work!
Apache 2.4 radically changed the authentication and authorization API. You will
need to port your AuthCookie subclass over to the Apache 2.4 API. See the POD
documentation in L<README.apache-2.4> for more information, but the quick
rundown is you need to:
=over 4
=item *
Inherit from C<Apache2_4::AuthCookie>
=item *
Remove all C<PerlAuthzHandler> configuration entries.
=item *
Write Authz Provider methods for any C<Requires> directives that you are using
that Apache does not provide for already (e.g. Apache already handles C<user>
and C<valid-user>) and register them with something like.
PerlAddAuthzProvier species Sample::AuthCookieHandler->authz_species
=item *
Replace instances of C<${AuthName}Satistfy> with either C<RequireAll> or
C<RequireAny> blocks.
=back
=item *
Why is my authz method called twice per request?
This is normal behaviour under Apache 2.4. This is to accommodate for
authorization of anonymous access. You are expected to return
C<Apache2::Const::AUTHZ_DENIED_NO_USER> IF C<< $r->user >> has not yet been set
if you want authentication to proceed. Your authz handler will be called a
second time after the user has been authenticated.
=item *
AuthCookie authenticates, but the authorization handler is returning
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