The reviewer runs an opencode agent with `bash: "*": allow` over a checkout of
the PR author's branch, and the pod holds a Gitea Write credential. Those two
facts had no wall between them.
Security
- _build_env now allow-lists the subprocess environment instead of inheriting
it, so PRAGENT_BOT_TOKEN and WEBHOOK_SECRET never reach the agent. This was
the live hole: a PR body or an AGENTS.md could ask the agent to `curl` the
token out, and it had both the value and the tool.
- sanitize_workdir deletes author-controlled agent-instruction files from the
checkout before opencode starts (AGENTS.md at any depth, CLAUDE.md,
.cursorrules, a repo opencode.json/.opencode, copilot-instructions.md).
opencode loads nested AGENTS.md as instructions, so a PR could otherwise ship
its own system prompt. They are still reviewed, as data.
- The brief fences PR title/body and diff in --- UNTRUSTED --- markers under a
trust-boundary preamble; the pragent agent, the three lens subagents and the
review-methodology skill now treat injection attempts as a critical finding
to report rather than an instruction to obey.
- .pr-review.json is read from the PR's base branch, not the head sha. Its
`instructions` field is spliced into the reviewer's prompt, so head-ref
reading let any author rewrite the reviewer's rules. Fields are length-capped.
- Untar rejects escaping symlinks, parent traversal, and writes through a
planted symlink (tar-slip).
- The image runs as uid 10001 instead of root.
Robustness
- Bounded review concurrency (PRAGENT_MAX_CONCURRENT_REVIEWS, default 2). Each
review forks an opencode process; a thread per delivery was a fork bomb on a
burst of labels or Gitea retries.
- An in-flight (repo, index, sha) claim closes the check-then-act race in the
sha-marker dedupe, where two deliveries a second apart both read "not yet
reviewed" and both posted.
- Request bodies are capped before being read into memory.
Correctness
- parse_diff_anchors counts a whitespace-stripped blank context line. Skipping
it desynced the new-line counter for the rest of the hunk and silently
misplaced every later inline comment in that file.
- post_inline_review's body-only fallback folds the anchored findings into the
body. It previously posted a summary saying "N inline comment(s) below" with
no comments and no findings — losing them all on the one path that matters.
- fetch_pr_diff's files-endpoint fallback emits real a// b/ prefixes (so
changed_files and the anchor parser work on it) and reports both HTTP statuses
in its error instead of the same one twice.
- The CI workflow template pins PRAGENT_ENGINE=ollama; review_pr defaults to
opencode, which does not exist on a Gitea Actions runner.
Tests: 68 -> 101, covering each of the above.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B11e8TZZxJyzHW7jj7KWUN
Marcos