Temporarily remove automatic printer discovery
cups-browsed is the daemon that watches the network and creates print queues by itself. Hardening it took a root daemon with a predictable cache down to a confined service account, but a daemon that turns anything advertising itself on the network into a print queue is a lot of exposure for a convenience, so it comes out of the default install while that is reworked. Only the discovery half: CUPS itself stays and printing keeps working, with each printer added by hand in Print Settings. The migration disables the unit before removing the package because that is the only order that works: pacman deletes the unit file but not the enable symlink, and once the unit is gone systemd can no longer resolve it by name to clean that up. It then removes the queues discovery generated. cups-browsed keeps those when it stops, since KeepGeneratedQueuesOnShutdown defaults to Yes, and they route through its own implicitclass backend, which goes with the package, so they cannot print again. Idle ones go. A queue with jobs on it is left alone and named: implicitclass only needs cups-browsed to choose a destination, so a job already past that point finishes on its own, and deleting the queue would abort it. One printer's job does not hold up the removal. A printer added by hand has an ipp:// or usb:// device and is left where it is. A queue whose jobs cannot be asked about is left alone rather than assumed idle, including one named so that lpstat would misread it -- "all" is its word for every destination, and a leading dash or a comma reads as another option or a list. Where CUPS does not answer at all, or a queue will not delete, discovery is still stopped but the package stays and no marker is written. omarchy-migrate records a migration for the user as soon as it exits zero, so that is where the machine stays until someone removes the package by hand, and the message says so rather than implying a retry. The queue list is read under LC_ALL=C because lpstat translates "device for", and captured rather than piped, so a cupsd it cannot reach is reported instead of reading like a machine with nothing to clean up. It removes with plain pacman -R rather than omarchy-pkg-drop, which passes -n and would discard /etc/cups/cups-browsed.conf instead of keeping it as a .pacsave. A removal meant to be temporary should not delete the machine's copy of its own configuration. Without -s either, so it only ever removes the package it names: sweeping newly unneeded dependencies is nothing today, but it is not a promise a rolling dependency graph can keep. Queue names come off the network, since cups-browsed names its queues after what the printer advertised. CUPS allows every printable character but space, tab, / and #, and lpstat and lpadmin take a destination as an option value, so a name with a leading dash or a comma is reported rather than passed to them and guessed at. Migration state is per user, so a machine-wide marker records the one removal. Without it, an account whose first migration run came after someone deliberately reinstalled discovery would quietly take it back out again. The install-time override for cups-browsed.conf now waits for cups-browsed rather than for CUPS. Guarding it on a file CUPS still ships would write a configuration file for a package nothing installed, and pacman would later land the package's own copy beside it as a .pacnew. The hardened configuration stays in the tree. omarchy-settings still ships the cups-browsed.conf override, the sysusers account and the service drop-in, so they are what discovery returns onto. Co-Authored-By: Codex XHigh <noreply@openai.com>
This commit is contained in:
David Heinemeier Hansson
co-authored by
Codex XHigh
Codex XHigh
parent
0b3f1b7ead
commit
24c18df5b7
@@ -47,7 +47,7 @@ verify_services() {
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local unit
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for unit in \
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avahi-daemon.service cups.service cups-browsed.service docker.socket \
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avahi-daemon.service cups.service docker.socket \
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NetworkManager.service power-profiles-daemon.service sddm.service \
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systemd-resolved.service ufw.service; do
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systemctl is-enabled --quiet "$unit" || fail "core system services are enabled" "$unit is not enabled"
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@@ -65,29 +65,24 @@ verify_services() {
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}
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verify_printing_security() {
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local cups_browsed_pid lpinfo_output printer_name printer_process printer_tmp
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local lpinfo_output
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! pacman -Q cups-pdf >/dev/null 2>&1 || fail "CUPS-PDF is absent"
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pass "the root CUPS-PDF backend is not installed"
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getent passwd cups-browsed >/dev/null || fail "the cups-browsed service account exists"
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[[ $(systemctl show -P User cups-browsed.service) == "cups-browsed" ]] ||
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fail "cups-browsed runs as its service account"
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[[ $(systemctl show -P Group cups-browsed.service) == "cups-browsed" ]] ||
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fail "cups-browsed runs as its service group"
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systemctl is-active --quiet cups-browsed.service || fail "cups-browsed is running"
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# Automatic discovery is temporarily out of the default install: a daemon that
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# turns anything advertising itself on the network into a print queue is more
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# exposure than the convenience is worth while it is reworked. CUPS itself
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# stays, so what a stock machine proves here is that printing runs and that
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# the desktop user still cannot administer it without authenticating.
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! pacman -Q cups-browsed >/dev/null 2>&1 || fail "automatic printer discovery is not installed"
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! systemctl is-enabled --quiet cups-browsed.service 2>/dev/null ||
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fail "no discovery service is enabled"
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! systemctl is-active --quiet cups-browsed.service 2>/dev/null ||
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fail "no discovery service is running"
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pass "automatic printer discovery is absent from a stock install"
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cups_browsed_pid=$(systemctl show -P MainPID cups-browsed.service)
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[[ -r /proc/$cups_browsed_pid/status ]] || fail "cups-browsed has a readable process status"
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[[ $(awk '/^Uid:/{print $2}' "/proc/$cups_browsed_pid/status") != 0 ]] ||
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fail "cups-browsed does not run with root UID"
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[[ $(awk '/^CapEff:/{print $2}' "/proc/$cups_browsed_pid/status") == "0000000000000000" ]] ||
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fail "cups-browsed has no effective Linux capabilities"
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[[ $(stat -c '%a %U:%G' /var/cache/cups-browsed) == "750 cups-browsed:cups-browsed" ]] ||
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fail "cups-browsed has an isolated cache" "$(stat -c '%a %U:%G' /var/cache/cups-browsed)"
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[[ " $(id -nG cups-browsed) " != *" cups "* ]] ||
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fail "cups-browsed is separate from the print-filter group"
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systemctl is-active --quiet cups.service || fail "CUPS is running"
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if lpinfo_output=$(LC_ALL=C timeout 10 lpinfo -v </dev/null 2>&1); then
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fail "the desktop user cannot administer CUPS without authentication"
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@@ -95,39 +90,7 @@ verify_printing_security() {
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fail "CUPS explicitly denies unauthenticated desktop administration" "$lpinfo_output"
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fi
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pass "CUPS discovery is isolated from root, filters, and passwordless desktop administration"
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# A live driverless printer proves the non-root daemon can still discover and
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# create queues without the CAP_NET_BIND_SERVICE Ubuntu carries downstream.
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printer_name="OmarchyAcceptancePrinter"
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printer_tmp=$(mktemp -d)
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printf '#!/bin/bash\nexit 0\n' >"$printer_tmp/command"
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chmod 0700 "$printer_tmp/command"
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mkdir -m 0700 "$printer_tmp/spool"
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ippeveprinter -p 18631 -d "$printer_tmp/spool" -c "$printer_tmp/command" "$printer_name" \
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>"$printer_tmp/ippeveprinter.log" 2>&1 &
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printer_process=$!
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printing_test_cleanup() {
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kill "$printer_process" >/dev/null 2>&1 || true
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wait "$printer_process" >/dev/null 2>&1 || true
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rm -rf "$printer_tmp"
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}
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trap printing_test_cleanup EXIT
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for _ in {1..30}; do
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lpstat -v "$printer_name" 2>/dev/null | grep -q "implicitclass://$printer_name/" && break
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sleep 1
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done
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lpstat -v "$printer_name" 2>/dev/null | grep -q "implicitclass://$printer_name/" ||
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fail "non-root cups-browsed discovers a driverless IPP printer" "$(<"$printer_tmp/ippeveprinter.log")"
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printing_test_cleanup
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trap - EXIT
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pass "non-root cups-browsed still creates driverless IPP queues without capabilities"
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pass "CUPS runs with passwordless desktop administration still denied"
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}
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verify_runtime_tools() {
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