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.

    Listing 1: Default Operation Policy

     1    <Policy default>
     2      # Job-related operations must be done by the owner or an
          adminstrator...
     3      <Limit Send-Document Send-URI Hold-Job Release-Job
          Restart-Job Purge-Jobs Set-Job-Attributes
          Create-Job-Subscription Renew-Subscription
          Cancel-Subscription Get-Notifications Reprocess-Job
          Cancel-Current-Job Suspend-Current-Job Resume-Job
          CUPS-Move-Job>
     4        Require user @OWNER @SYSTEM
     5        Order deny,allow
     6      </Limit>
     7
     8      # All administration operations require an adminstrator
          to authenticate...
     9      <Limit Pause-Printer Resume-Printer
          Set-Printer-Attributes Enable-Printer Disable-Printer
          Pause-Printer-After-Current-Job Hold-New-Jobs
          Release-Held-New-Jobs Deactivate-Printer Activate-Printer
          Restart-Printer Shutdown-Printer Startup-Printer
          Promote-Job Schedule-Job-After CUPS-Add-Printer
          CUPS-Delete-Printer CUPS-Add-Class CUPS-Delete-Class
          CUPS-Accept-Jobs CUPS-Reject-Jobs CUPS-Set-Default>
    10        AuthType Basic
    11        Require user @SYSTEM
    12        Order deny,allow
    13      </Limit>
    14
    15      # Only the owner or an administrator can cancel or
          authenticate a job...
    16      <Limit Cancel-Job CUPS-Authenticate-Job>
    17        Require user @OWNER @SYSTEM
    18        Order deny,allow
    19      </Limit>
    20
    21      <Limit All>
    22        Order deny,allow
    23      </Limit>
    24    </Policy>

### The Default CUPS Operation Policy

The policy definition starts with an opening `Policy` directive:

     1    <Policy default>

The first `Limit` subsection defines the rules for IPP job operations:

     3      <Limit Send-Document Send-URI Hold-Job Release-Job
          Restart-Job Purge-Jobs Set-Job-Attributes
          Create-Job-Subscription Renew-Subscription
          Cancel-Subscription Get-Notifications Reprocess-Job
          Cancel-Current-Job Suspend-Current-Job Resume-Job
          CUPS-Move-Job>
     4        Require user @OWNER @SYSTEM
     5        Order deny,allow
     6      </Limit>

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:

     9      <Limit Pause-Printer Resume-Printer
          Set-Printer-Attributes Enable-Printer Disable-Printer
          Pause-Printer-After-Current-Job Hold-New-Jobs
          Release-Held-New-Jobs Deactivate-Printer Activate-Printer
          Restart-Printer Shutdown-Printer Startup-Printer
          Promote-Job Schedule-Job-After CUPS-Add-Printer
          CUPS-Delete-Printer CUPS-Add-Class CUPS-Delete-Class
          CUPS-Accept-Jobs CUPS-Reject-Jobs CUPS-Set-Default>
    10        AuthType Basic
    11        Require user @SYSTEM
    12        Order deny,allow
    13      </Limit>

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:

    16      <Limit Cancel-Job CUPS-Authenticate-Job>
    17        Require user @OWNER @SYSTEM
    18        Order deny,allow
    19      </Limit>

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:

    21      <Limit All>
    22        Order deny,allow
    23      </Limit>
    24    </Policy>

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 (#):

    <Policy mypolicy>

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:

    <Limit Cancel-Job>
      Order deny,allow
    </Limit>

The directives inside the `Limit` subsection can use any of the normal limiting directives: `Allow`, `AuthType`, `Deny`, `Encryption`, `Require`, and `Satisfy`. Table 2 lists some basic "recipes" for different access control rules.

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.

    Listing 2: Operation Policy for a Lab

     1    <Policy lab999>
     2      # Job- and subscription-related operations must be done
          by the owner, a lab technician, or an adminstrator...
     3      <Limit Send-Document Send-URI Hold-Job Release-Job
          Restart-Job Purge-Jobs Set-Job-Attributes
          Create-Job-Subscription Renew-Subscription
          Cancel-Subscription Get-Notifications Reprocess-Job
          Cancel-Current-Job Suspend-Current-Job Resume-Job
          CUPS-Move-Job Cancel-Job CUPS-Authenticate-Job>
     4        Require user @OWNER @lab999 @SYSTEM
     5        Order allow,deny
     6        Allow from 10.0.2.0/24
     7      </Limit>
     8
     9      # All administration operations require a lab technician
          or an adminstrator to authenticate...
    10      <Limit Pause-Printer Resume-Printer
          Set-Printer-Attributes Enable-Printer Disable-Printer
          Pause-Printer-After-Current-Job Hold-New-Jobs
          Release-Held-New-Jobs Deactivate-Printer Activate-Printer
          Restart-Printer Shutdown-Printer Startup-Printer
          Promote-Job Schedule-Job-After CUPS-Accept-Jobs
          CUPS-Reject-Jobs CUPS-Set-Default>
    11        AuthType Basic
    12        Require user @lab999 @SYSTEM
    13        Order allow,deny
    14        Allow from 10.0.2.0/24
    15      </Limit>
    16
    17      # All other operations are allowed from the lab network...
    18      <Limit All>
    19        Order allow,deny
    20        Allow from 10.0.2.0/24
    21      </Limit>
    22    </Policy>

## 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:

    DefaultPolicy lab999

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":

    lpadmin -p LaserJet4000 -o printer-op-policy=lab999

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.