Apache Module mod_session_dbd

Available Languages: en

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Description:	DBD/SQL based session support
Status:	Extension
Module Identifier:	session_dbd_module
Source File:	mod_session_dbd.c

Summary

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Warning

The session modules make use of HTTP cookies, and as such can fall + victim to Cross Site Scripting attacks, or expose potentially private + information to clients. Please ensure that the relevant risks have + been taken into account before enabling the session functionality on + your server.

+ +

This submodule of mod_session provides support for the + storage of user sessions within a SQL database using the + mod_dbd module.

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Sessions can either be anonymous, where the session is + keyed by a unique UUID string stored on the browser in a cookie, or + per user, where the session is keyed against the userid of + the logged in user.

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

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

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

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Topics

DBD Configuration
Anonymous Sessions
Per User Sessions
Database Housekeeping

DBD Configuration

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Before the mod_session_dbd module can be configured to maintain a + session, the mod_dbd module must be configured to make the various database queries + available to the server.

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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.

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Sample DBD configuration

+ DBDriver pgsql + DBDParams "dbname=apachesession user=apache password=xxxxx host=localhost" + DBDPrepareSQL "delete from session where key = %s" deletesession + DBDPrepareSQL "update session set value = %s, expiry = %lld where key = %s" updatesession + DBDPrepareSQL "insert into session (value, expiry, key) values (%s, %lld, %s)" insertsession + DBDPrepareSQL "select value from session where key = %s and (expiry = 0 or expiry > %lld)" selectsession + DBDPrepareSQL "delete from session where expiry != 0 and expiry < %lld" cleansession +

+ +

Anonymous Sessions

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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.

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

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SQL based anonymous session

+ Session On + SessionDBDCookieName session path=/ +

+ +

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

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

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Per User Sessions

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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.

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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 like + mod_auth_form.

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

+ +

SQL based per user session

+ Session On + SessionDBDPerUser On +

+ +

Database Housekeeping

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

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Warning

The administrator will need to set up an external process via cron to clean + out expired sessions.

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SessionDBDCookieName Directive

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Description:	Name and attributes for the RFC2109 cookie storing the session ID
Syntax:	`SessionDBDCookieName name attributes`
Default:	`none`
Context:	directory
Status:	Extension
Module:	mod_session_dbd
Compatibility:	Available in Apache 2.3.0 and later

The SessionDBDCookieName 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 the Set-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. +

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Cookie with attributes

+ Session On + SessionDBDCookieName session path=/private;domain=example.com;httponly;secure;version=1; +

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SessionDBDCookieName2 Directive

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Description:	Name and attributes for the RFC2965 cookie storing the session ID
Syntax:	`SessionDBDCookieName2 name attributes`
Default:	`none`
Context:	directory
Status:	Extension
Module:	mod_session_dbd
Compatibility:	Available in Apache 2.3.0 and later

The SessionDBDCookieName2 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 the Set-Cookie2 HTTP header. +

+ +

Cookie2 with attributes

+ Session On + SessionDBDCookieName2 session path=/private;domain=example.com;httponly;secure;version=1; +

+ + +

SessionDBDCookieRemove Directive

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Description:	Control for whether session ID cookies should be removed from incoming HTTP headers
Syntax:	`SessionDBDCookieRemove On\|Off`
Default:	`SessionDBDCookieRemove On`
Context:	directory
Status:	Extension
Module:	mod_session_dbd
Compatibility:	Available in Apache 2.3.0 and later

The SessionDBDCookieRemove 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.

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SessionDBDDeleteLabel Directive

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Description:	The SQL query to use to remove sessions from the database
Syntax:	`SessionDBDDeleteLabel label`
Default:	`SessionDBDDeleteLabel deletesession`
Context:	directory
Status:	Extension
Module:	mod_session_dbd
Compatibility:	Available in Apache 2.3.0 and later

The SessionDBDDeleteLabel 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 the DBDPrepareSQL directive.

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SessionDBDInsertLabel Directive

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Description:	The SQL query to use to insert sessions into the database
Syntax:	`SessionDBDInsertLabel label`
Default:	`SessionDBDInsertLabel insertsession`
Context:	directory
Status:	Extension
Module:	mod_session_dbd
Compatibility:	Available in Apache 2.3.0 and later

The SessionDBDInsertLabel directive sets the default insert + query label to be used to load in a session. This label must have been previously defined using the + DBDPrepareSQL directive.

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

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SessionDBDPerUser Directive

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Description:	Enable a per user session
Syntax:	`SessionDBDPerUser On\|Off`
Default:	`SessionDBDPerUser Off`
Context:	directory
Status:	Extension
Module:	mod_session_dbd
Compatibility:	Available in Apache 2.3.0 and later

The SessionDBDPerUser 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.

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SessionDBDSelectLabel Directive

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Description:	The SQL query to use to select sessions from the database
Syntax:	`SessionDBDSelectLabel label`
Default:	`SessionDBDSelectLabel selectsession`
Context:	directory
Status:	Extension
Module:	mod_session_dbd
Compatibility:	Available in Apache 2.3.0 and later

The SessionDBDSelectLabel directive sets the default select + query label to be used to load in a session. This label must have been previously defined using the + DBDPrepareSQL directive.

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SessionDBDUpdateLabel Directive

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Description:	The SQL query to use to update existing sessions in the database
Syntax:	`SessionDBDUpdateLabel label`
Default:	`SessionDBDUpdateLabel updatesession`
Context:	directory
Status:	Extension
Module:	mod_session_dbd
Compatibility:	Available in Apache 2.3.0 and later

The SessionDBDUpdateLabel directive sets the default update + query label to be used to load in a session. This label must have been previously defined using the + DBDPrepareSQL directive.

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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.

+ + +

Apache Module mod_session_dbd

Summary

Warning

Directives

Topics

See also

Sample DBD configuration

SQL based anonymous session

SQL based per user session

Warning

Cookie with attributes

Cookie2 with attributes