Merge pull request #8627 from mdisec/security/harden-cups-browsed
Harden CUPS printer discovery
This commit is contained in:
Ryan Hughes
@@ -0,0 +1,221 @@
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#!/bin/bash
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set -euo pipefail
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source "$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)/base-test.sh"
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packages="$ROOT/install/omarchy-base.packages"
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cups_browsed_conf="$ROOT/etc/cups/cups-browsed.conf"
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cups_files_conf="$ROOT/etc/cups/cups-files.conf"
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sysusers_conf="$ROOT/etc/sysusers.d/omarchy-cups-browsed.conf"
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service_dropin="$ROOT/etc/systemd/system/cups-browsed.service.d/10-omarchy.conf"
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grep -qxF cups-browsed "$packages" || fail "cups-browsed remains in the base package set"
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grep -qxF cups-pk-helper "$packages" || fail "Polkit printer administration is installed"
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! grep -qxF cups-pdf "$packages" || fail "the root CUPS-PDF backend is removed"
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pass "the base install keeps discovery and replaces CUPS-PDF with Polkit administration"
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grep -qxF 'CacheDir /var/cache/cups-browsed' "$cups_browsed_conf" ||
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fail "cups-browsed keeps state outside the print-filter cache"
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grep -qxF 'CreateIPPPrinterQueues Driverless' "$cups_browsed_conf" ||
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fail "automatic queues are limited to driverless IPP printers"
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grep -qxF 'CreateRemoteCUPSPrinterQueues No' "$cups_browsed_conf" ||
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fail "remote CUPS queues are not created automatically"
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! grep -q 'CreateRemotePrinters' "$cups_browsed_conf" ||
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fail "the unsupported CreateRemotePrinters directive is gone"
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pass "cups-browsed uses explicit supported discovery policy and an isolated cache"
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grep -qxF 'SystemGroup cups-browsed sys root' "$cups_files_conf" ||
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fail "only the printer discovery account receives passwordless CUPS administration"
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grep -qxF 'PeerCred on' "$cups_files_conf" ||
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fail "the packaged CUPS policy enables peer credentials"
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[[ $(grep -ciE '^[[:space:]]*SystemGroup[[:space:]]' "$cups_files_conf") == 1 ]] ||
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fail "the packaged CUPS policy has one SystemGroup directive"
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[[ $(grep -ciE '^[[:space:]]*PeerCred[[:space:]]' "$cups_files_conf") == 1 ]] ||
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fail "the packaged CUPS policy has one PeerCred directive"
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[[ ! -e $ROOT/install/config/printing.sh ]] ||
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fail "printing policy is not rewritten by an install script"
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! grep -q 'config/printing.sh' "$ROOT/install/config/all.sh" "$ROOT/migrations/1787815267.sh" ||
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fail "neither install nor update invokes a printing rewrite script"
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pass "CUPS authorization ships as a canonical package override"
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grep -qxF 'u cups-browsed - "CUPS printer discovery" / -' "$sysusers_conf" ||
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fail "a locked cups-browsed system account is declared"
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for setting in \
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'User=cups-browsed' \
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'Group=cups-browsed' \
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'CacheDirectory=cups-browsed' \
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'CacheDirectoryMode=0750' \
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'UMask=0027' \
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'NoNewPrivileges=yes' \
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'ProtectSystem=strict' \
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'ProtectHome=yes' \
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'PrivateTmp=yes' \
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'RestrictSUIDSGID=yes'; do
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grep -qxF "$setting" "$service_dropin" ||
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fail "cups-browsed service hardening includes $setting"
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done
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! grep -q '^\(Ambient\|CapabilityBoundingSet\).*CAP_NET_BIND_SERVICE' "$service_dropin" ||
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fail "cups-browsed is not granted an unverified network capability"
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pass "cups-browsed runs as its confined service account without added capabilities"
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test_tmp=$(mktemp -d)
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trap 'rm -rf "$test_tmp"' EXIT
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mock_bin="$test_tmp/bin"
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mkdir -p "$mock_bin" "$test_tmp/var/lib/omarchy/migrations"
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passwd_db="$test_tmp/passwd"
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group_db="$test_tmp/group"
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touch "$passwd_db" "$group_db"
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cat >"$mock_bin/getent" <<'SH'
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#!/bin/bash
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case "$1" in
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passwd) database="$OMARCHY_CUPS_TEST_PASSWD" ;;
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group) database="$OMARCHY_CUPS_TEST_GROUP" ;;
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*) exit 2 ;;
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esac
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if (($# == 1)); then
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cat "$database"
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else
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awk -F: -v name="$2" '$1 == name { print; found = 1 } END { exit !found }' "$database"
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fi
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SH
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cat >"$mock_bin/omarchy-pkg-present" <<'SH'
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#!/bin/bash
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[[ $1 == "cups" || $1 == "cups-browsed" ]]
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SH
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for command in omarchy-pkg-add omarchy-pkg-drop; do
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cat >"$mock_bin/$command" <<'SH'
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#!/bin/bash
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printf '%s\t%s\n' "${0##*/}" "$*" >>"$OMARCHY_CUPS_TEST_LOG"
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SH
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done
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cat >"$mock_bin/systemctl" <<'SH'
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#!/bin/bash
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printf 'systemctl\t%s\n' "$*" >>"$OMARCHY_CUPS_TEST_LOG"
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exit 0
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SH
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cat >"$mock_bin/sudo" <<'SH'
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#!/bin/bash
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printf 'sudo\t%s\n' "$*" >>"$OMARCHY_CUPS_TEST_LOG"
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exec "$@"
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SH
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chmod +x "$mock_bin"/*
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log="$test_tmp/actions.log"
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touch "$log"
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export OMARCHY_CUPS_TEST_LOG="$log"
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export OMARCHY_CUPS_TEST_PASSWD="$passwd_db"
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export OMARCHY_CUPS_TEST_GROUP="$group_db"
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printf 'cups-browsed:x:1000:1000:Desktop user:/home/cups-browsed:/usr/bin/bash\n' >"$passwd_db"
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printf 'cups-browsed:x:1000:\n' >"$group_db"
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if PATH="$mock_bin:$PATH" \
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OMARCHY_PATH="$ROOT" \
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OMARCHY_CUPS_MIGRATION_MARKER="$test_tmp/desktop-collision-marker" \
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bash -euo pipefail "$ROOT/migrations/1787815267.sh" 2>/dev/null; then
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fail "the migration accepts an existing desktop user named cups-browsed"
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fi
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[[ ! -s $log ]] || fail "an account collision stops the migration before changing the system"
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printf 'alice:x:1000:947:Desktop user:/home/alice:/usr/bin/bash\n' >"$passwd_db"
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printf 'cups-browsed:x:947:alice\n' >"$group_db"
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if PATH="$mock_bin:$PATH" \
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OMARCHY_PATH="$ROOT" \
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OMARCHY_CUPS_MIGRATION_MARKER="$test_tmp/group-collision-marker" \
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bash -euo pipefail "$ROOT/migrations/1787815267.sh" 2>/dev/null; then
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fail "the migration accepts an existing cups-browsed group with members"
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fi
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[[ ! -s $log ]] || fail "a group collision stops the migration before changing the system"
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printf 'cups-browsed:x:947:947:CUPS printer discovery:/:/usr/bin/nologin\n' >"$passwd_db"
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printf 'cups-browsed:x:947:\n' >"$group_db"
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pass "the migration rejects account and group collisions before changing printing"
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marker="$test_tmp/var/lib/omarchy/migrations/1787815267"
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PATH="$mock_bin:$PATH" \
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OMARCHY_PATH="$ROOT" \
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OMARCHY_CUPS_MIGRATION_MARKER="$marker" \
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bash -euo pipefail "$ROOT/migrations/1787815267.sh"
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grep -qxF $'omarchy-pkg-drop\tcups-pdf' "$log" ||
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fail "the migration removes CUPS-PDF"
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grep -qxF $'omarchy-pkg-add\tcups-pk-helper' "$log" ||
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fail "the migration installs authenticated printer administration"
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grep -qxF $'systemctl\tstop cups-browsed.service' "$log" ||
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fail "the migration stops the root cups-browsed process before reconfiguration"
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grep -qxF $'systemctl\tdaemon-reload' "$log" ||
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fail "the migration reloads the hardened service"
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grep -qxF $'systemctl\ttry-reload-or-restart cups.service' "$log" ||
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fail "the migration reloads the packaged CUPS authorization"
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grep -qxF $'systemctl\trestart cups-browsed.service' "$log" ||
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fail "the migration resumes an active cups-browsed service"
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[[ -f $marker ]] || fail "the migration records machine-wide completion"
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actions_after_first_run=$(wc -l <"$log")
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PATH="$mock_bin:$PATH" \
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OMARCHY_PATH="$ROOT" \
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OMARCHY_CUPS_MIGRATION_MARKER="$marker" \
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bash -euo pipefail "$ROOT/migrations/1787815267.sh"
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[[ $(wc -l <"$log") == "$actions_after_first_run" ]] ||
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fail "the machine-wide migration repeats privileged work"
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pass "the migration safely converts an active existing installation once"
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# An interrupted earlier run leaves cups-browsed stopped. A retry still needs
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# to resume an enabled service before recording completion.
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cat >"$mock_bin/systemctl" <<'SH'
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#!/bin/bash
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printf 'systemctl\t%s\n' "$*" >>"$OMARCHY_CUPS_TEST_LOG"
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[[ $1 == "is-active" ]] && exit 1
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exit 0
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SH
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chmod +x "$mock_bin/systemctl"
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retry_log="$test_tmp/retry.log"
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retry_marker="$test_tmp/var/lib/omarchy/migrations/1787815267-retry"
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OMARCHY_CUPS_TEST_LOG="$retry_log" \
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PATH="$mock_bin:$PATH" \
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OMARCHY_PATH="$ROOT" \
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OMARCHY_CUPS_MIGRATION_MARKER="$retry_marker" \
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bash -euo pipefail "$ROOT/migrations/1787815267.sh"
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grep -qxF $'systemctl\trestart cups-browsed.service' "$retry_log" ||
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fail "the retry resumes cups-browsed after an interrupted earlier run"
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pass "a run following an interrupted one still resumes printer discovery"
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# A masked or disabled unit is deliberately left alone.
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cat >"$mock_bin/systemctl" <<'SH'
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#!/bin/bash
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printf 'systemctl\t%s\n' "$*" >>"$OMARCHY_CUPS_TEST_LOG"
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[[ $1 == "is-active" || $1 == "is-enabled" ]] && exit 1
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exit 0
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SH
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chmod +x "$mock_bin/systemctl"
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masked_log="$test_tmp/masked.log"
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masked_marker="$test_tmp/var/lib/omarchy/migrations/1787815267-masked"
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OMARCHY_CUPS_TEST_LOG="$masked_log" \
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PATH="$mock_bin:$PATH" \
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OMARCHY_PATH="$ROOT" \
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OMARCHY_CUPS_MIGRATION_MARKER="$masked_marker" \
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bash -euo pipefail "$ROOT/migrations/1787815267.sh"
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! grep -qxF $'systemctl\trestart cups-browsed.service' "$masked_log" ||
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fail "the migration leaves a masked or disabled cups-browsed alone"
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[[ -f $masked_marker ]] || fail "the migration completes with cups-browsed masked"
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pass "a masked or disabled cups-browsed is left alone and does not fail the migration"
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@@ -144,11 +144,12 @@ pass "keyboard prompt propagates Esc and Ctrl+C without dying under set -e"
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# Username
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TAKEN_USERS=dhh run_prompt omarchy_prompt_username "0:Not A Username" "0:root" "0:dhh" "0:david"
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TAKEN_USERS=dhh run_prompt omarchy_prompt_username "0:Not A Username" "0:root" "0:cups-browsed" "0:dhh" "0:david"
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assert_status 0 "username prompt accepts a valid name"
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[[ $(field username) == "david" ]] || fail "username prompt keeps re-asking until the name is valid"
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assert_notices "username prompt explains each rejection" "Username must be alphanumeric with no spaces
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Username is reserved for system
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Username is reserved for system
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That username already exists on this machine"
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pass "username prompt rejects malformed, reserved, and taken names"
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