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I installed CUPS 2.2.1 on a fresh installation of Debian 9 (stretch/stable). The root account is disabled on this machine. I use sudo to elevate the privileges of my normal user account ma. The /etc/cups/cupsd.conf file looks like this

#
# Configuration file for the CUPS scheduler.  See "man cupsd.conf" for a
# complete description of this file.
#
# EDIT: added this line
SystemGroup printadmin

# Log general information in error_log - change "warn" to "debug"
# for troubleshooting...
LogLevel warn
PageLogFormat

# Deactivate CUPS' internal logrotating, as we provide a better one, especially
# LogLevel debug2 gets usable now
MaxLogSize 0

# Only listen for connections from the local machine.
Listen localhost:631
Listen /var/run/cups/cups.sock

# Show shared printers on the local network.
Browsing On
BrowseLocalProtocols dnssd

# Default authentication type, when authentication is required...
# EDIT: changed DefaultAuthType Basic to DefaultAuthType None
DefaultAuthType None

# Web interface setting...
WebInterface Yes

# Restrict access to the server...
<Location />
  Order allow,deny
</Location>

# Restrict access to the admin pages...
# EDIT: added Allow localhost
<Location /admin>
    Order allow,deny
    Allow localhost
</Location>


# Restrict access to configuration files...
<Location /admin/conf>
  AuthType Default
  Require user @SYSTEM
  Order allow,deny
</Location>

# Restrict access to log files...
<Location /admin/log>
  AuthType Default
  Require user @SYSTEM
  Order allow,deny
</Location>


# Set the default printer/job policies...
<Policy default>
  # Job/subscription privacy...
  JobPrivateAccess default
  JobPrivateValues default
  SubscriptionPrivateAccess default
  SubscriptionPrivateValues default

  # Job-related operations must be done by the owner or an administrator...
  <Limit Create-Job Print-Job Print-URI Validate-Job>
    Order deny,allow
  </Limit>

  <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 Cancel-My-Jobs Close-Job CUPS-Move-Job CUPS-Get-Document>
    Require user @OWNER @SYSTEM
    Order deny,allow
  </Limit>

  # All administration operations require an administrator to authenticate...
# EDIT: changed AuthType Default to AuthType None
  <Limit CUPS-Add-Modify-Printer CUPS-Delete-Printer CUPS-Add-Modify-Class CUPS-Delete-Class CUPS-Set-Default CUPS-Get-Devices>
    AuthType None
    Require user @SYSTEM
    Order deny,allow
  </Limit>

  # All printer operations require a printer operator to authenticate...
  <Limit Pause-Printer Resume-Printer 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 Cancel-Jobs CUPS-Accept-Jobs CUPS-Reject-Jobs>
    AuthType Default
    Require user @SYSTEM
    Order deny,allow
  </Limit>

  # Only the owner or an administrator can cancel or authenticate a job...
  <Limit Cancel-Job CUPS-Authenticate-Job>
    Require user @OWNER @SYSTEM
    Order deny,allow
  </Limit>

  <Limit All>
    Order deny,allow
  </Limit>
</Policy>

# Set the authenticated printer/job policies...
<Policy authenticated>
  # Job/subscription privacy...
  JobPrivateAccess default
  JobPrivateValues default
  SubscriptionPrivateAccess default
  SubscriptionPrivateValues default

  # Job-related operations must be done by the owner or an administrator...
  <Limit Create-Job Print-Job Print-URI Validate-Job>
    AuthType Default
    Order deny,allow
  </Limit>

  <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 Cancel-My-Jobs Close-Job CUPS-Move-Job CUPS-Get-Document>
    AuthType Default
    Require user @OWNER @SYSTEM
    Order deny,allow
  </Limit>

  # All administration operations require an administrator to authenticate...
  <Limit CUPS-Add-Modify-Printer CUPS-Delete-Printer CUPS-Add-Modify-Class CUPS-Delete-Class CUPS-Set-Default>
    AuthType Default
    Require user @SYSTEM
    Order deny,allow
  </Limit>

  # All printer operations require a printer operator to authenticate...
  <Limit Pause-Printer Resume-Printer 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 Cancel-Jobs CUPS-Accept-Jobs CUPS-Reject-Jobs>
    AuthType Default
    Require user @SYSTEM
    Order deny,allow
  </Limit>

  # Only the owner or an administrator can cancel or authenticate a job...
  <Limit Cancel-Job CUPS-Authenticate-Job>
    AuthType Default
    Require user @OWNER @SYSTEM
    Order deny,allow
  </Limit>

  <Limit All>
    Order deny,allow
  </Limit>
</Policy>

I created the printadmin group and added myself to it

sudo groupadd printadmin
sudo usermod -a -G printadmin ma

and did the same for the lp group, per this post.

Then a reboot, but when I click "Add Printer" in the admin interface (localhost:631), I get the same "Unable to add printer: Forbidden" error as before. The log file /var/log/cups/error_log contains this

E [16/Sep/2017:11:34:23 -0500] [Client 24] Returning HTTP Forbidden for CUPS-Get-Devices (no URI) from localhost
E [16/Sep/2017:11:34:23 -0500] [CGI] CUPS-Get-Devices request failed with status 401: Forbidden

which doesn't tell me anything new. What am I doing wrong?

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  • I think you forgot some details. "Then a reboot, but still the same error." You don't say what you did to produce the error. And also, do you have any printers installed? Commented Sep 16, 2017 at 19:51
  • @FaheemMitha Thanks for the correction. I updated the post. I get this error when I try to add a printer through the admin web interface, i.e. localhost:631 Commented Sep 16, 2017 at 20:57
  • Interesting. There is an executable, lpadmin, which you can also use to add a printer. Try using that instead - it might be easier to diagnose. Commented Sep 16, 2017 at 22:29
  • And nitpick - "I get the same "Unable to add printer: Forbidden" error as before". But you didn't mention it the first time. :-) I suggest leaving out the "as before" bit. Commented Sep 16, 2017 at 22:31
  • @FaheemMitha Fair enough. I mentioned it in the title, but maybe that isn't enough. Commented Sep 16, 2017 at 23:19

1 Answer 1

Reset to default
3

My (fedora) cups 2.1.3 man page for cupsd.conf says

File, directory, and user configuration directives that used to be allowed in the cupsd.conf file are now stored in the cups-files.conf(5) file instead

So your SystemGroup printadmin line should probably be moved into /etc/cups/cups-files.conf

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