Apache Module mod_session_dbd

Summary

This submodule ofmod_session provides support for the storage of user sessions within a SQL database using themod_dbd module.

Sessions can either beanonymous, where the session is keyed by a unique UUID string stored on the browser in a cookie, orper user, where the session is keyed against the userid of the logged in user.

SQL based sessions are hidden from the browser, and so offer a measure of privacy without the need for encryption.

Different webservers within a server farm may choose to share a database, and so share sessions with one another.

For more details on the session interface, see the documentation for themod_session module.

Topics

• DBD Configuration
• Anonymous Sessions
• Per User Sessions
• Database Housekeeping

Directives

• SessionDBDCookieName
• SessionDBDCookieName2
• SessionDBDCookieRemove
• SessionDBDDeleteLabel
• SessionDBDInsertLabel
• SessionDBDPerUser
• SessionDBDSelectLabel
• SessionDBDUpdateLabel

Bugfix checklist

• httpd changelog
• Known issues
• Report a bug

See also

• mod_session
• mod_session_crypto
• mod_session_cookie
• mod_dbd
• Comments

DBD Configuration

Before themod_session_dbd module can be configured to maintain a session, themod_dbd module must be configured to make the various database queries available to the server.

There are four queries required to keep a session maintained, to select an existing session, to update an existing session, to insert a new session, and to delete an expired or empty session. These queries are configured as per the example below.

DBDriver pgsqlDBDParams "dbname=apachesession user=apache password=xxxxx host=localhost"DBDPrepareSQL "delete from session where key = %s" deletesessionDBDPrepareSQL "update session set value = %s, expiry = %lld, key = %s where key = %s" updatesessionDBDPrepareSQL "insert into session (value, expiry, key) values (%s, %lld, %s)" insertsessionDBDPrepareSQL "select value from session where key = %s and (expiry = 0 or expiry > %lld)" selectsessionDBDPrepareSQL "delete from session where expiry != 0 and expiry < %lld" cleansession

Anonymous Sessions

Anonymous sessions are keyed against a unique UUID, and stored on the browser within an HTTP cookie. This method is similar to that used by most application servers to store session information.

To create a simple anonymous session and store it in a postgres database table calledapachesession, and save the session ID in a cookie calledsession, configure the session as follows:

Session OnSessionDBDCookieName session path=/

For more examples on how the session can be configured to be read from and written to by a CGI application, see themod_session examples section.

For documentation on how the session can be used to store username and password details, see themod_auth_form module.

Per User Sessions

Per user sessions are keyed against the username of a successfully authenticated user. It offers the most privacy, as no external handle to the session exists outside of the authenticated realm.

Per user sessions work within a correctly configured authenticated environment, be that using basic authentication, digest authentication or SSL client certificates. Due to the limitations of who came first, the chicken or the egg, per user sessions cannot be used to store authentication credentials from a module likemod_auth_form.

To create a simple per user session and store it in a postgres database table calledapachesession, and with the session keyed to the userid, configure the session as follows:

Session OnSessionDBDPerUser On

Database Housekeeping

Over the course of time, the database can be expected to start accumulating expired sessions. At this point, themod_session_dbd module is not yet able to handle session expiry automatically.

SessionDBDCookieNameDirective

TheSessionDBDCookieName directive specifies the name and optional attributes of an RFC2109 compliant cookie inside which the session ID will be stored. RFC2109 cookies are set using theSet-Cookie HTTP header.

An optional list of cookie attributes can be specified, as per the example below. These attributes are inserted into the cookie as is, and are not interpreted by Apache. Ensure that your attributes are defined correctly as per the cookie specification.

Session OnSessionDBDCookieName session path=/private;domain=example.com;httponly;secure;version=1;

SessionDBDCookieName2Directive

TheSessionDBDCookieName2 directive specifies the name and optional attributes of an RFC2965 compliant cookie inside which the session ID will be stored. RFC2965 cookies are set using theSet-Cookie2 HTTP header.

An optional list of cookie attributes can be specified, as per the example below. These attributes are inserted into the cookie as is, and are not interpreted by Apache. Ensure that your attributes are defined correctly as per the cookie specification.

Session OnSessionDBDCookieName2 session path=/private;domain=example.com;httponly;secure;version=1;

SessionDBDCookieRemoveDirective

TheSessionDBDCookieRemove flag controls whether the cookies containing the session ID will be removed from the headers during request processing.

In a reverse proxy situation where the Apache server acts as a server frontend for a backend origin server, revealing the contents of the session ID cookie to the backend could be a potential privacy violation. When set to on, the session ID cookie will be removed from the incoming HTTP headers.

SessionDBDDeleteLabelDirective

TheSessionDBDDeleteLabel directive sets the default delete query label to be used to delete an expired or empty session. This label must have been previously defined using theDBDPrepareSQL directive.

SessionDBDInsertLabelDirective

TheSessionDBDInsertLabel directive sets the default insert query label to be used to load in a session. This label must have been previously defined using theDBDPrepareSQL directive.

If an attempt to update the session affects no rows, this query will be called to insert the session into the database.

SessionDBDPerUserDirective

TheSessionDBDPerUser flag enables a per user session keyed against the user's login name. If the user is not logged in, this directive will be ignored.

SessionDBDSelectLabelDirective

TheSessionDBDSelectLabel directive sets the default select query label to be used to load in a session. This label must have been previously defined using theDBDPrepareSQL directive.

SessionDBDUpdateLabelDirective

TheSessionDBDUpdateLabel directive sets the default update query label to be used to load in a session. This label must have been previously defined using theDBDPrepareSQL directive.

If an attempt to update the session affects no rows, the insert query will be called to insert the session into the database. If the database supports InsertOrUpdate, override this query to perform the update in one query instead of two.