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lib/CGI/Session/Tutorial.pm  view on Meta::CPAN

Cookie is a piece of text-information that a web server is entitled to place in the user's hard disk, assuming a user agent (such as Internet Explorer, Mozilla, etc) is compatible with the specification. After the cookie is placed, user agents are re...

Although I<HTTP Cookies> seem to be promising solution for the statelessness of HTTP, they do carry certain limitations, such as limited number of cookies per domain and per user agent and limited size on each cookie. User Agents are required to stor...

=head2 QUERY STRING

Query string is a string appended to URL following a question mark (?) such as:

    http://my.dot.com/login.cgi?user=sherzodr;password=top-secret

As you probably guessed, it can also help you pass state information from a click to another, but how secure is it do you think, considering these URLs tend to get cached by most of the user agents and also logged in the servers access log, to which ...

=head2 HIDDEN FIELDS

Hidden field is another alternative to using query strings and they come in two flavors: hidden fields used in POST methods and the ones in GET. The ones used in GET methods will turn into a true query strings once submitted, so all the disadvantages...

Query strings and hidden fields are also lost easily by closing the browser, or by clicking the browser's "Back" button.

=head2 SERVER SIDE SESSION MANAGEMENT

This technique is built upon the aforementioned technologies plus a server-side storage device, which saves the state data on the server side. Each session has a unique id associated with the data in the server. This id is also associated with the us...

lib/CGI/Session/Tutorial.pm  view on Meta::CPAN

    $session->expire(_cc_access, '5m');

With the above syntax, the person will still have access to his personal information even after 5 idle hours. But when he tries to access or update his/her credit card information, he may be displayed a "login again, please" screen.

See L<expire()|CGI::Session/expire()> for details.

This concludes our discussion of CGI::Session programming style. The rest of the manual covers some L<"SECURITY"> issues. Driver specs from the previous manual were moved to L<CGI::Session::Driver|CGI::Session::Driver>.

=head1 SECURITY

"How secure is using CGI::Session?", "Can others hack down people's sessions using another browser if they can get the session id of the user?", "Are the session ids easy to guess?" are the questions I find myself answering over and over again.

=head2 STORAGE

Security of the library does in many aspects depend on the implementation. After making use of this library, you no longer have to send all the information to the user's cookie except for the session id. But, you still have to store the data in the s...

=over 4

=item *

First rule of thumb, do not store users' passwords or other sensitive data in the session, please. If you have to, use one-way encryption, such as md5, or SHA-1-1. For my own experience I can assure you that in properly implemented session-powered We...

lib/CGI/Session/Tutorial.pm  view on Meta::CPAN

Do not allow anyone to update contents of session files. If you're using L<default serializer|CGI::Session::Serialize::default> serialized data string needs to be eval()ed to bring the original data structure back to life. Of course, we use L<Safe|Sa...

=item *

Do not keep sessions open for very long. This will increase the possibility that some bad guy may have someone's valid session id at a given time (acquired somehow). To do this use L<expire()|CGI::Session/expire()> method to set expiration ticker. Th...

=back

=head2 SESSION IDs

Session ids are not easily guessed (unless you're using L<incr ID generator|CGI::Session::ID::incr>)! Default configuration of CGI::Session uses L<Digest::MD5|CGI::Session::ID::md5> to generate random, 32 character long identifier. Although this stri...

Consider the scenario, where you just give someone either via email or an instant messaging a link to a Web site where you're currently logged in. The URL you give to that person contains a session id as part of a query string. If the site was initia...

Even if you're solely using cookies as the session id transporters, it's not that difficult to plant a cookie in the cookie file with the same id and trick the web browser to send that particular session id to the server. So key for security is to ch...

One way to help with this is by also checking that the IP address that the session is being used from is always same. However, this turns out not to be practical in common cases because some large ISPs (such as AOL) use proxies which cause each and e...

If you have an application where you are sure your users' IPs are constant during a session, you can consider enabling an option to make this check:

    use CGI::Session '-ip_match';