security: scope polkit face auth to an allowlist and fail closed on unresolved user (Plan 03)#84
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tyvsmith wants to merge 3 commits into
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security: scope polkit face auth to an allowlist and fail closed on unresolved user (Plan 03)#84tyvsmith wants to merge 3 commits into
tyvsmith wants to merge 3 commits into
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…on unresolved user Closes polkit findings F1 (no action allowlist) and F2 (UID 0 fail-open). A single face match previously authorized *every* polkit action — pkexec, package install, disk mount, user admin. Now the agent offers face auth only for actions in a configurable allowlist (`polkit.face_eligible_actions`, default `["org.freedesktop.login1.lock-sessions"]`); high-risk actions are excluded by default. A non-allowlisted action is declined (Failed) so polkit falls through to the password dialog — a fall-through, never a denial. Users may extend the list; an empty list disables face entirely. Fail closed on unresolved username: `respond_to_polkit` resolves the target name to a uid and refuses if it does not resolve, instead of substituting UID 0 (which authenticated an unresolvable name as root). Container proof: pkg-validate.sh gains a busctl-driven assertion (test/polkit-agent-validate.sh) that the agent declines a non-allowlisted action_id and accepts an allowlisted one at its D-Bus boundary. Both test-deb-pkg and test-rpm-pkg now ship the agent binary and pass 24/24; rpm gains dbus-daemon so the runtime D-Bus block runs on Fedora. Docs: docs/contracts.md (new [polkit] key + Polkit Agent Semantics), docs/security.md (agent scoping section), config/facelock.toml sample. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Pull request overview
This PR hardens the facelock-polkit-agent so a successful face match is no longer a universal authorization mechanism for arbitrary polkit actions, and it removes a fail-open-to-root behavior when the target username cannot be resolved.
Changes:
- Introduces a configurable polkit
action_idallowlist (polkit.face_eligible_actions) and declines non-allowlisted actions to force password fall-through. - Changes polkit response behavior to fail closed when a username cannot be resolved to a UID (never substitutes UID 0).
- Adds container-level validation for the agent’s D-Bus boundary behavior and updates docs/sample config accordingly.
Reviewed changes
Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| test/polkit-agent-validate.sh | Adds a container-friendly D-Bus boundary validation script for allowlist behavior. |
| test/pkg-validate.sh | Hooks the new polkit-agent boundary check into package validation. |
| test/Containerfile.rpm-e2e | Ensures the RPM E2E container includes dbus-daemon and ships the polkit agent binary + validation script. |
| test/Containerfile.deb-e2e | Ships the polkit agent binary + validation script into the DEB E2E container. |
| docs/security.md | Documents the new polkit agent scoping and fail-closed UID resolution behavior. |
| docs/contracts.md | Extends config/contracts to include [polkit].face_eligible_actions and defines agent semantics. |
| crates/facelock-polkit/src/main.rs | Implements allowlist gating, fail-closed UID resolution, and a test-mode session-bus name hook. |
| crates/facelock-core/src/config.rs | Adds PolkitConfig to core config with defaults and tests for allowlist behavior. |
| config/facelock.toml | Updates sample config with the new [polkit] section and guidance. |
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| FAIL=0 | ||
| BUS_SOCK="$(mktemp -u /tmp/facelock-polkit-session-bus.XXXXXX)" | ||
| SESSION_ADDR="unix:path=${BUS_SOCK}" | ||
| AGENT_PID="" | ||
| BUS_PID="" | ||
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| cleanup() { | ||
| [ -n "$AGENT_PID" ] && kill "$AGENT_PID" 2>/dev/null || true | ||
| [ -n "$BUS_PID" ] && kill "$BUS_PID" 2>/dev/null || true | ||
| rm -f "$BUS_SOCK" | ||
| } |
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| # Wait for the session bus socket. | ||
| for _ in $(seq 1 50); do | ||
| [ -S "$BUS_SOCK" ] && break | ||
| sleep 0.1 | ||
| done |
cargo fmt --all -- --check was failing CI on unwrapped long assert! lines added by the polkit allowlist tests. Run cargo fmt --all to wrap them per rustfmt's max-width rules. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Two independent reviewers flagged that docs/security.md and docs/contracts.md overstated polkit agent behavior: they claimed a non-allowlisted action "falls through to the password dialog handled by another agent." polkit registers a single authentication agent per session and does not chain agents, so a decline from this agent likely produces an authorization denial rather than a fallthrough, depending on the desktop's agent registration. This is fail-closed (safe) but changes the UX story and has not been verified on a live desktop. Replace the fallthrough claims with an explicit "under review" caveat in both docs (including the contracts.md outcome table and the security.md polkit config example) instead of asserting either behavior as final. Surrounding allowlist documentation is unchanged. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Summary
Stops a single face match from authorizing every polkit action, and stops the fail-open-to-root on an unresolvable username (Plan 03, findings F1 and F2).
polkit.face_eligible_actions(default["org.freedesktop.login1.lock-sessions"]). High-risk actions (pkexec, PackageKit install/remove, udisks mount, accounts-service user admin) are excluded by default. A non-allowlisted action is declined (Failed) so polkit falls through to the password dialog — a fall-through, never a denial. Users may extend the list; an empty list disables face entirely.respond_to_polkitresolves the target name to a uid and refuses if it does not resolve, instead of substituting UID 0 (which previously authenticated an unresolvable name as root).Verification
cargo build/cargo test/cargo clippy -D warningsgreen; unit test added for therespond_to_polkituid-resolution branch (unresolved name → refusal, never UID 0).test/polkit-agent-validate.sh(busctl-driven) asserts at the agent's D-Bus boundary that it declines a non-allowlistedaction_idand accepts an allowlisted one.just test-deb-pkgandjust test-rpm-pkgboth ship the agent binary and pass 24/24 (rpm gainsdbus-daemonso the runtime D-Bus block runs on Fedora). No camera required.Contract docs
docs/contracts.md(new[polkit]key + Polkit Agent Semantics) anddocs/security.md(agent scoping — face is now scoped, not universal);config/facelock.tomlsample updated.Closes #65
Closes #66
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