Can't get default printer under Apple sandbox

[Simplestas]

Scenario:
try to get default printer in sandboxed app
cupsGetNamedDest(CUPS_HTTP_DEFAULT, 0, 0)
when specific default printer is set in System Preferences - Printers.

Expected:
default printer

Actual:
IPP_STATUS_ERROR_NOT_FOUND

What happens:
libcups tries to access ~/.cups/loptions to get default printer
Apple does provide entitlement com.apple.security.print which does allow that
BUT
cups uses getenv("HOME") to get home folder pathwhich returns ~/Containers/{bundle id}/Data under sandbox
while it should use real home folder (getpwuid(getuid())->pw_dir)

[michaelrsweet]

Hmm, this seems to be working in Safari (also sandboxed). What version of macOS and CUPS are you using?

[Simplestas]

That's on macOS 10.15.1 / CUPS 2.3.0

Safari uses PrintCore which talks to cups via printtool daemon.

I.e. PMSessionGetCurrentPrinter works fine in sandbox, but we would like to use cups directly as well.

[michaelrsweet]

OK, I've created a short test program to reproduce this, and confirmed that ~/.cups can be safely read in a sandboxed application.

Changes will be a little more involved (need to replace all uses of getenv("HOME")) but will see what I can do...

[michaelrsweet]

[master e2eb28c] Sandboxed applications were not able to get the default printer (Issue #5676)

Unfortunately, that doesn't do much to help you now - you'll need to wait until this fix makes it into a macOS release...

[Simplestas]

Thanks, we can work with that.