Managing Operation Policies

Operation policies are the rules used for each IPP operation in CUPS. These rules include things like "user must provide a password", "user must be in the system group", "allow only from the local system", and so forth. Until CUPS 1.2, these rules were largely hardcoded and could only be customized at a very basic level.

CUPS 1.2 adds a new fine-grained policy layer which allows you to completely redefine the rules for each operation and/or printer. Each policy is named and defines access control rules for each IPP operation. This document describes how to manage policies and their rules.

The Basics

Operation policies are used for all IPP requests sent to the scheduler and are evaluated after the Location based access control rules. This means that operation policies can only add additional security restrictions to a request, never relax them. Use Location based access control rules for server-wide limits and operation policies for limits on individual printers, tasks, or services.

Policies are stored in the cupsd.conf file in Policy sections. Each policy has an alphanumeric name that is used to select it. Inside the policy section are one or more Limit subsections which list the operations that are affected by the rules inside it. Listing 1 shows the default operation policy, appropriately called "default", that is shipped with CUPS.

The easiest way to add a policy to the cupsd.conf file is to use the web interface. Click on the Administration tab and then the Edit Configuration File button to edit the current cupsd.conf file. Click on the Save Changes button to save the changes and restart the scheduler. If you edit the cupsd.conf file from the console, make sure to restart the cupsd process before trying to use the new policy.

The Default CUPS Operation Policy

The operation names are listed on a single line with spaces separating them. Each name corresponds to the IPP operation described in any of the IETF or PWG standards documents for the Internet Printing Protocol. Table 1 lists all of the operations that have been defined along with their usage in CUPS.

The access control rules are listed after the Limit line and are the same as those used for Location sections. In this case, we require the owner of the job ("@OWNER") or a member of the SystemGroup ("@SYSTEM") to do the operation. Because we do not include an AuthType directive here, the user information can come from the IPP request itself or the authenticated username from the HTTP request. The administrative operations starting on line 9, however, do use the AuthType directive, and so administrative operations need to be authenticated:

The "Order deny,allow" line at the end of both Limit subsections allows the request to come from any system allowed by the Location sections elsewhere in the cupsd.conf file.

The Cancel-Job and CUPS-Authenticate-Job operations are listed separately to allow the web interface to more easily edit their policy without disturbing the rest. Like the rest of the job operations, we want the job's owner ("@OWNER") or an administrator ("@SYSTEM") to do it:

The last Limit subsection in any policy uses the special operation name All. CUPS will use the rules in this subsection for any operation you don't list specifically in the policy. In this case, all other operations are allowed without a username or authentication:

Table 1: IPP Operation Names
Name	Used by CUPS?	Description
`Print-Job`	Yes	Creates a print job with a single file.
`Print-URI`	No	Create a print job with a single URI.
`Validate-Job`	Yes	Validates a print request before printing.
`Create-Job`	Yes	Creates a print job with no files or URIs.
`Send-Document`	Yes	Adds a file to a print job.
`Send-URI`	No	Adds a URI to a print job.
`Cancel-Job`	Yes	Cancels a print job.
`Get-Job-Attributes`	Yes	Gets information and options associated with a job.
`Get-Jobs`	Yes	Gets a list of jobs.
`Get-Printer-Attributes`	Yes	Gets information and options associated with a printer or class.
`Hold-Job`	Yes	Holds a print job for printing.
`Release-Job`	Yes	Releases a print job for printing.
`Restart-Job`	Yes	Reprints a print job.
`Pause-Printer`	Yes	Stops a printer or class.
`Resume-Printer`	Yes	Starts a printer or class.
`Purge-Jobs`	Yes	Cancels all jobs on the server or a printer or class and removes the job history information.
`Set-Printer-Attributes`	No	Sets printer or class information; CUPS uses CUPS-Add-Modify-Printer and CUPS-Add-Modify-Class instead.
`Set-Job-Attributes`	Yes	Changes job options.
`Get-Printer-Supported-Values`	No	Gets -supported attributes for a printer based on job options.
`Create-Printer-Subscription`	Yes	Creates an event subscription for a printer or the server.
`Create-Job-Subscription`	Yes	Creates an event subscription for a job.
`Get-Subscription-Attributes`	Yes	Gets information for an event subscription.
`Get-Subscriptions`	Yes	Gets a list of event subscriptions.
`Renew-Subscription`	Yes	Renews an event subscription that is about to expire.
`Cancel-Subscription`	Yes	Cancels an event subscription.
`Get-Notifications`	Yes	Gets (pending) events for an event subscription.
`Send-Notifications`	No	Sends events for an event subscription.
`Get-Printer-Support-Files`	No	Gets printer driver files for a Novell client.
`Enable-Printer`	Yes	Starts a printer or class.
`Disable-Printer`	Yes	Stops a printer or class.
`Pause-Printer-After-Current-Job`	No	Stops a printer or class after the current job is finished.
`Hold-New-Jobs`	No	Holds new jobs submitted to a printer or class.
`Release-Held-New-Jobs`	No	Releases jobs that were held because of the Hold-New-Jobs operation.
`Deactivate-Printer`	No	Deactivates a printer or class.
`Activate-Printer`	No	Activates a printer or class.
`Restart-Printer`	No	Restarts a printer or class, resuming print jobs as needed.
`Shutdown-Printer`	No	Powers a printer or class off.
`Startup-Printer`	No	Powers a printer or class on.
`Reprocess-Job`	No	Reprints a job on a different printer or class; CUPS has the CUPS-Move-Job operation instead.
`Cancel-Current-Job`	No	Cancels the current job on a printer or class.
`Suspend-Current-Job`	No	Stops the current job on a printer or class.
`Resume-Job`	No	Resumes printing of a stopped job.
`Promote-Job`	No	Prints a job before others.
`Schedule-Job-After`	No	Prints a job after others.
`CUPS-Get-Default`	Yes	Gets the server/network default printer or class.
`CUPS-Get-Printers`	Yes	Gets a list of printers and/or classes.
`CUPS-Add-Modify-Printer`	Yes	Adds or modifies a printer.
`CUPS-Delete-Printer`	Yes	Removes a printer.
`CUPS-Get-Classes`	Yes	Gets a list of classes.
`CUPS-Add-Modify-Class`	Yes	Adds or modifies a class.
`CUPS-Delete-Class`	Yes	Removes a class.
`CUPS-Accept-Jobs`	Yes	Sets a printer's or class' printer-is-accepting-jobs attribute to true.
`CUPS-Reject-Jobs`	Yes	Sets a printer's or class' printer-is-accepting-jobs attribute to false.
`CUPS-Set-Default`	Yes	Sets the server/network default printer or class.
`CUPS-Get-Devices`	Yes	Gets a list of printer devices.
`CUPS-Get-PPDs`	Yes	Gets a list of printer drivers or manufacturers.
`CUPS-Move-Job`	Yes	Moves a job to a different printer or class.
`CUPS-Authenticate-Job`	Yes	Authenticates a job for printing.

Creating Your Own Policies

The easiest way to create a new policy is to start with the default policy and then make changes to the copy. The first change you'll make is to give the policy a new name. Policy names can use the same characters as a printer name, specifically all printable characters except space, slash (/), and pound (#):

Then you need to decide exactly what limits you want for the policy. For example, if you want to allow any user to cancel any other users' jobs, you can change the Cancel-Job limits to:

Table 2: Access Control Recipes
Access Level	Directives to Use
Allow Everyone	Order deny,allow Allow from all
Allow Everyone on the Local Network	Order deny,allow Allow from @LOCAL
Deny Everyone/Disable Operation(s)	Order allow,deny Deny from all
Require Login (System) Password	AuthType Basic
Require CUPS (lppasswd) Password	AuthType BasicDigest
Require the Owner of a Job or Subscription	Require user @OWNER
Require an Administrative User	Require user @SYSTEM
Require Member of Group "foogroup"	Require user @foogroup
Require "john" or "mary"	Require user john mary
Require Encryption	Encryption Required

Creating a Policy for a Computer Lab

One common operating scenario is a computer lab. The lab is managed by one or more technicians that assist the users of the lab and handle the basic administration tasks. Listing 2 shows an operation policy that only allows access from the lab's subnet, 10.0.2.x, and allows the lab technicians, who are members of a special UNIX group for that lab called "lab999", to do job, printer, and subscription management operations.

Using Policies

Once you have created a policy, you can use it in two ways. The first way is to assign it as the default policy for the system using the DefaultPolicy directive in the cupsd.conf file. For example, add the following line to the cupsd.conf file to use the "lab999" policy from the previous section:

To associate the policy with one or more printers, use either the lpadmin(8) command or the web interface to change the operation policy for each printer. When using the lpadmin command, the -o printer-op-policy=name option sets the operation policy for a printer. For example, enter the following command to use the "lab999" policy from the previous section with a printer named "LaserJet4000":

To make the same change in the web interface, go to the printer's web page, for example "http://localhost:631/printers/LaserJet4000", and click on the Set Printer Options button. Scroll down to the bottom of the page and choose the desired policy from the pull-down list. Click on Save Changes to change the policy for the printer.