Change cupsd.conf to force authentication when accessing administration

[AtariDreams]

With the current default configuration, someone can request to Find New Printers without being authenticated and with no way to be authenticated. Without authentication cups does not detects printers on the network. The person might not realize that it's because authentication is missing. It seems natural to always offer to authenticate when accessing the administration page.

Co-Authored-By: Dominic Mayers dominic.mayers@meditationstudies.org

[AtariDreams]

@michaelrsweet Could we merge this one too please

[michaelrsweet]

@AtariDreams I'm not the only developer for the CUPS project, and in particular @zdohnal is the release manager for the CUPS 2.4.x series... As he also works for a Linux distribution, I'd like him to review this PR and make sure it doesn't cause problems.

[AtariDreams]

Sure thing.

[AtariDreams]

@zdohnal Thoughts?

[AtariDreams]

@michaelrsweet Does this mean you can merge this PR or?

[zdohnal]

Hi all,

I'm still cleaning up things in Fedora/RHEL after my sickness, but I briefly looked into this PR.

In general any change in configuration file is bigger or smaller problem for migrations (either between single CUPS version updates or between OS version's migrations), especially ones which depend on being in a specific scope in the config. Because the proposed change is of this kind, I would prefer the same behavior as Add Printer has - the user is asked for authentication once he clicks on the button Add Printer (but in our case he would click on Find New Printers).

IIUC this authentication prompt is brought by cupsGetDevices() from do_am_printer() in cgi-bin/admin.c, which is not used in do_list_printers() used for finding new printers. The function uses IPP requests for getting permanent queues and then for getting devices instead of calling CUPS API, so its usage could get the same behavior as it is for adding a printer - but this has to be done a separate function, which will be called only if we want find new printers (we don't want to hide printer's list under authentication...)

So my plan is:

• find out whether I can create a scriptlet-fu for migration with the proposed change and let you know then,

or (if the migration can't be done by a script during upgrade and it would require an external migration solution like LEAPP)

• introduce a do_find_new_printers() which will start with auth prompt.

Once I'm done with my script research, I'll clear the review request and let you know how we can proceed.

[zdohnal]

Plus I've tried to check whether other clients (like cupsenable etc.) will be affected by the change, since they send requests to /admin/ resource path, but it doesn't seem to change for them - the tools require the authentication even now.

[zdohnal]

Ok, I've come with the following:

grep -m 1 -A 20 "^\s*<Location /admin>" /etc/cups/cupsd.conf | grep -m 1 -B 20 "^\s*</Location>" | grep -E '^\s*AuthType|^\s*Require' &> /dev/null || sed -i '/^\s*<Location \/admin>/a\  AuthType Default\n  Require user @SYSTEM' /etc/cups/cupsd.conf

which will get you location /admin scope in case it is not longer than 20 lines (I accounted some possible specific Allow/Deny lines, so it should cover most of use case).

So Ack to the PR.

[zdohnal]

LGTM once migration script is applied.

[zdohnal]

A little bit better command, where colleague helped me and taught me new things about sed. Additionally the command does a backup of config (in case the script goes wrong) - here I use .rpmsave, but other distros can use a different one:

sed -ne '/^\s*<Location \/admin>/ { :loop; /<\/Location>/ ! {N; b loop}; p }' /etc/cups/cupsd.conf \
| grep -E '^\s*(AuthType|Require)' &> /dev/null || cp /etc/cups/cupsd.conf{,.rpmsave} && \
sed -i '/^\s*<Location \/admin>/a\  AuthType Default\n  Require user @SYSTEM' /etc/cups/cupsd.conf

I hope it is useful for someone.