Session Validation

Magento Community allows you to validate session variables as a protective measure against
possible session fixation attacks, or attempts to poison or hijack user sessions. The Session
Validation Settings determine how session variables are validated during each store visit, and if
the session ID is included in the URL of the store.
The validation checks to see that visitors are who they say they are by comparing the value in
the validation variables against the session data that is already stored in $_SESSION data for
the user. Validation fails if the information is not transmitted as expected, and the
corresponding variable is empty. Depending on the session validation settings, if a session
variable fails the validation process, the client session immediately terminates.
Enabling all of the validation variables can help prevent attacks, but might also impact the
performance of the server. By default, all session variable validation is disabled. We recommend
that you experiment with the settings to find the best combination for your Magento
installation. Activating all of the validation variables might prove to be unduly restrictive, and
prevent access to customers who have Internet connections that pass through a proxy server, or
that originate from behind a firewall. To learn more about session variables and their use, see
the system administration documentation for your Linux system.

To configure the Session Validation Settings:

1. On the Admin menu, select System > Configuration. Then in the panel on the left under
General, select Web.
2. Click to expand the Session Validation Settings section. Then, do the following:

a. To verify that the IP address of a request matches what is stored in the $_SESSION
variable, set Validate REMOTE_ADDR to “Yes.”
b. To verify that the proxy address of an incoming request matches what is stored in the $_
SESSION variable, set Validate HTTP_VIA to “Yes.”
c. To verify that the forwarded-for address of a request matches what is stored in the $_
SESSION variable, set Validate HTTP_X_FORWARDED_FOR to “Yes.”
d. To verify that the browser or device that is used to access the store during a session
matches what is stored in the $_SESSION variable, set Validate HTTP_USER_AGENT to
e. If you want a user to stay logged in while switching between stores, set Use SID on
Frontend to “Yes.”
If including SID with analytics, you must configure your analytics software to filter the SID
from URLs, so the page visit counts are correct.
3. When complete, click the Save Config button.

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