Stack/19 security - #1297
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Included review availability: This review used your included allowance. Your plan provides up to 8 included reviews per hour; 5 remain after this review. 📝 WalkthroughWalkthroughThe pull request adds broker write-path restrictions, renderer process validation and termination, and safeguards for request handling, file loading, cookies, and storage. It also adds a security assessment and updates process-isolation documentation. ChangesProcess and Engine Security Controls
Priority: ➖ Normal Estimated code review effort: 4 (Complex) | ~60 minutes Change: Bug fix Sequence Diagram(s)sequenceDiagram
participant ForkServerClient
participant is_stream_socket
participant open_child_pidfd
participant ResidentRenderer
participant pidfd_kill
participant RendererProcess
ForkServerClient->>is_stream_socket: Check handed-over descriptor
ForkServerClient->>open_child_pidfd: Verify renderer PID and parent
open_child_pidfd-->>ForkServerClient: Return owned pidfd
ForkServerClient->>ResidentRenderer: Store pidfd
ResidentRenderer->>pidfd_kill: Kill on first mark_dead transition
pidfd_kill->>RendererProcess: Send SIGKILL through pidfd
Merge Risk: ⚪ Minimal · up to No actionable merge-blocking risk remains from the reviewed changes. The reset-origin check has a narrow limitation, but it restricts access compared with the previous behavior. Security Architecture ReviewSecurity architecture risk: 🔵 Low · up to The inspected changes strengthen isolation and reduce cross-site interference. No introduced or materially worsened security exposure was established. Remaining uncertainty concerns adoption by other applications, degraded confinement, and existing persistence and local-access limits. Retained concerns Security review detailsSecurity Blast Radius
Security Findings and Attack Paths
Trust Boundaries and Controls
Resilience and Maintainability Implications
Hardening Proposals
🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
✨ Finishing Touches📝 Generate docstrings
🧪 Generate unit tests (beta)
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jaytaph
added this pull request to stack #1211
October 2, 2026 10:59
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Actionable comments posted: 4
- 🪄 Fix CodeRabbit comments on this PR
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Inline comments:
Review comments at @crates/gosub_engine/src/engine/cookies/cookie_jar.rs:
- Around line 277-281: Update the eviction selection around `written` and
`self.entries`: choose the written origin only when its registrable domain is
also the largest by cookie count; otherwise evict from the largest-domain
bucket. Add a test where `bank.test` stores two cookies, the jar is flooded,
then `bank.test` stores another cookie, and assert `session=1` survives.
Review comments at @crates/gosub_engine/src/metrics.rs:
- Line 82: The `host_is_local(req)` check in the metrics reset handler does not
prevent cross-site form submissions; validate the request `Origin` against the
local origin or require a CSRF token before calling `reset_stats()`. Update the
comment near the handler so it does not claim Host filtering blocks cross-site
POSTs.
Review comments at @crates/gosub_engine/src/net/file_loader.rs:
- Around line 165-169: Update the file-reading flow in serve to detect files
that grow beyond MAX_FILE_BYTES: read up to one byte beyond the cap and return
an error if that extra byte is present, rather than treating the capped content
as a successful complete body.
Review comments at @crates/gosub_sandbox/src/linux.rs:
- Around line 1186-1190: Update the writable-path loop that adds entries to
rules so a missing directory does not cause the entire Landlock ruleset to fail:
skip that path with a warning while retaining the other rules, or propagate the
failure explicitly to the caller.
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📒 Files selected for processing (20)
crates/gosub_engine/src/bin/isolation-harness.rscrates/gosub_engine/src/child_process.rscrates/gosub_engine/src/engine/context.rscrates/gosub_engine/src/engine/cookies/cookie_jar.rscrates/gosub_engine/src/engine/cookies/store/json.rscrates/gosub_engine/src/engine/storage.rscrates/gosub_engine/src/engine/storage/local/file_store.rscrates/gosub_engine/src/fork_server/client.rscrates/gosub_engine/src/metrics.rscrates/gosub_engine/src/net/file_loader.rscrates/gosub_engine/src/storage_service/client.rscrates/gosub_ipc/src/channel.rscrates/gosub_ipc/src/channel/unix.rscrates/gosub_sandbox/src/lib.rscrates/gosub_sandbox/src/linux.rscrates/gosub_sandbox/src/selftest.rsdocs/README.mddocs/process-isolation.mddocs/security-assessment.mdexamples/mini-browser/main.rs
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…ad renderer is killed
RendererSpawned { pid } was the fork server's word, and the broker
placed that pid in a 1.25 GiB, 256-task cgroup: pid 0 is the writer
itself, so a compromised fork server could confine the broker, or the
network process. The broker now opens a pidfd for the pid first and
requires /proc to name the fork server as its parent; a wrong claim is
a hostile fork server and stops it. The pidfd is what the broker kills
through once it gives up on a renderer - the per-request deadline bounds
a page that loops, not a renderer that disarmed its own timer, and the
broker held only a socket. The link handed over must be a stream socket,
not any socket. Unit test for the verification.
Bound to 127.0.0.1 but dispatching on the request line alone, it answered a page on attacker.example whose DNS answer switched to 127.0.0.1 after it loaded: /events, every URL the browser fetches, same-origin. And POST /metrics/reset was a cross-site form away. A Host that is not 127.0.0.1, localhost or ::1 gets 403. Tests for both sides.
The jar-wide cap evicted the oldest cookie anywhere, so a page naming 3000 of its own subdomains - the newest cookies in the jar - logged the user out of every other site in the zone. Eviction now takes from the origin being written (while it has more than the cookie just stored), then the registrable domain holding the most cookies, then the oldest anywhere: RFC 6265 section 5.3 step 12's order. Test rewritten for it.
<img src="file:///dev/zero"> from any local HTML page had the broker read without end (in-process on main as well); a FIFO held the reading thread until its timeout. Regular files only, at most 256 MiB, read with a limit rather than trusting the size.
…lone Created with the umask: 0755 directories and a 0644 cookie file, which another local user reads if the profile directory is traversable. 0700 and 0600 now; an existing directory keeps the embedder's mode.
TileMemory::remove walked the arrival deque per hash; a pass may evict 50 000 against 20 000 kept, repeatable per hover, on the tab thread. Sequence numbers in a map, stale deque entries skipped lazily.
…s checked Control and bidi override characters in a title reached the embedder's window; a hit region's image string reached the embedder's open-image and save-image menus with any scheme. Both bounded where the renderer's other claims are.
… the mini-browser and the harness lock_down_broker had no caller in the engine or any example: every statement about the broker's Landlock scope held for nobody. It takes the embedder's writable directories now (profile, downloads, logs), gosub_engine::child_process::lock_down_broker exposes it, the embedder contract names it as the step after dispatch, the mini-browser applies it with its data directory, and the harness runs every engine scenario under it so CI exercises the engine confined.
Attacker positions, assets, what this branch fixed, what is accepted with what the sandbox still prevents, and what is open. The contract gains the broker lockdown; the deadline, telemetry and file: sentences say what they now mean.
…ne at a time telemetry::enabled() is process-wide, true while any test's stream holds a subscription; the idle-client test asserted it false while a sibling ran, and failed under the full parallel suite only.
The Host check closes the cross-site read, not a cross-site write: a form on any page may POST to 127.0.0.1 and the browser sends this server's own name as Host. The reset now requires an Origin that is a loopback origin when one is present; a request without one is not a browser's (examples/metrics_cli.rs). The comment no longer claims Host filtering covers the POST. Test with attacker, null, lookalike, loopback and absent origins.
take(cap) returned the first 256 MiB of a file that grew after the size check as a complete 200 body. One byte past the cap is read; if it is there, the file is refused whole.
… fatal to the ruleset A directory an embedder names but has not created yet (downloads, made later) failed the O_PATH anchor, which failed the ruleset whole and left the broker's filesystem unconfined for every path. Such a path is named on stderr and skipped; the mini-browser says so when it cannot create its data directory rather than ignoring the error.
…hat domain Taking from the writing origin first meant that at a cap a flooder had filled, every cookie a victim site stored evicted the victim's own oldest - usually its session - while the flood sat untouched. The registrable domain with the most cookies gives first; within it the writer, if that is where it sits, else the domain's oldest. Test: the victim writes two more cookies at the cap and keeps all three.
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Summary by CodeRabbit
Security & Privacy
Bug Fixes
Documentation