# Staff Security Engineer — Standalone Review (Round 5)

**Branch**: `colonyos/you_are_a_code_assistant_working_on_behalf_of_the_engineering_team_the_following`
**Date**: 2026-03-19
**Scope**: Full branch diff vs `main` — Slack integration, thread-fix pipeline, LLM triage, queue executor

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## Security Assessment

### 1. Prompt Injection Attack Surface (HIGH PRIORITY)

**Threat**: Slack messages are untrusted user input that flows directly into agent prompts executed with `permission_mode="bypassPermissions"` (agent.py:52). A malicious Slack channel member can craft messages that attempt to exfiltrate secrets, modify unrelated files, or execute arbitrary commands.

**Mitigations present (good)**:
- XML tag stripping via `sanitize_untrusted_content()` prevents closing wrapper delimiters (sanitize.py:18-23)
- Slack link markup stripping removes `<URL|text>` patterns that could carry payloads (sanitize.py:54-71)
- Role-anchoring preamble in `format_slack_as_prompt()` explicitly tells the model to ignore adversarial instructions (slack.py:99-113)
- `<slack_message>` delimiters wrap untrusted content (slack.py:105-111)
- Defense-in-depth re-sanitization at point of use in `_build_thread_fix_prompt()` (orchestrator.py:1666-1667)
- Triage agent uses `allowed_tools=[]` to minimize blast radius (slack.py:809)

**Residual risk**:
- The `sanitize_untrusted_content` regex (`</?[a-zA-Z][a-zA-Z0-9_-]*(?:\s[^>]*)?>`) only strips well-formed XML tags. Partial tags, Unicode confusables, or HTML entities could bypass this.
- The role-anchoring preamble is a probabilistic defense — sophisticated prompt injection can still succeed against it. This is an inherent limitation acknowledged in the docstring.
- The Implement phase runs with full `Bash` tool access under `bypassPermissions`. A successful prompt injection gives arbitrary code execution on the host.

### 2. Authorization & Access Control

**Positives**:
- `allowed_user_ids` allowlist for restricting who can trigger pipelines (slack.py:181, config.py:100)
- Approval flow with `wait_for_approval()` supports `allowed_approver_ids` to prevent self-approval (slack.py:386-431)
- Warning logs when `allowed_user_ids` is empty with `auto_approve=true` (config.py:236-241)
- Channel allowlist enforcement (slack.py:157-158)
- Fix round limits per thread (config.py:107, cli.py:2004)

**Concern**:
- The `allowed_user_ids` list is commented out in the shipped config.yaml (`.colonyos/config.yaml`). This means by default, **any user in the configured channels can trigger autonomous code execution** when `auto_approve: false` is set. The warning log (config.py:223-228) is appropriate, but this is still a dangerous default for production.

### 3. Secrets Management

**Positives**:
- Bot tokens read from environment variables at call time, not cached on app instance (slack.py:1029-1031, 1045)
- Explicit comment about why tokens are not stashed on the app instance (slack.py:1028-1030)
- `git stash push` only stashes tracked files to avoid capturing `.env.local` etc. (orchestrator.py:1777-1778)
- Secret pattern redaction in CI logs (sanitize.py:28-43, 74-84)
- Slack bot/user token patterns included in redaction list (sanitize.py:37-38)

**Concern**:
- The agent process running under `bypassPermissions` can still read environment variables via Bash. A successful prompt injection could `echo $COLONYOS_SLACK_BOT_TOKEN` and exfiltrate it through committed code or PR descriptions. This is an inherent limitation of the `bypassPermissions` model and not solvable at the application layer alone.

### 4. Git Ref Injection

**Positives**:
- `is_valid_git_ref()` uses strict character allowlist `[a-zA-Z0-9._/-]` (slack.py:57, 828-841)
- Rejects `..`, leading/trailing `/`, length > 255
- Branch name re-validated at point of use in `_execute_fix_item()` (cli.py:2731) and `run_thread_fix()` (orchestrator.py:1743)
- Base branch from LLM triage validated before use (slack.py:752-757)
- All `subprocess.run` calls use list form (not shell=True), preventing shell injection

### 5. Rate Limiting & Budget Controls

**Positives**:
- `max_runs_per_hour` with hourly counting (slack.py:630-644)
- `daily_budget_usd` cap (config.py:102)
- `max_fix_rounds_per_thread` prevents unbounded iteration (config.py:107)
- `max_queue_depth` prevents queue flooding (config.py:103)
- Circuit breaker with `max_consecutive_failures` and cooldown (config.py:105-106)
- Triage budget limited to $0.05 (slack.py:808)

### 6. Audit Trail

**Positives**:
- Structured `AUDIT:` log entries for pipeline enqueue, thread-fix enqueue, and orphan detection (cli.py:1918, 2057, 2245)
- Includes user ID, channel, branch, item ID in audit logs
- Slack link URLs logged at DEBUG level before stripping (sanitize.py:66-67)

**Concern**:
- Audit logs go to Python's logging system. There is no mention of structured log forwarding, log retention, or tamper-evident logging. For a system that runs arbitrary code, a centralized audit log with immutable storage would be ideal.

### 7. HEAD SHA Verification (Force-Push Defense)

**Positive**: The `expected_head_sha` check (orchestrator.py:1810-1818) detects if the branch was force-pushed between the parent run and the fix request, preventing code execution on an unexpected codebase state.

### 8. Verify Phase Tool Restriction

**Positive**: The Verify phase restricts tools to `["Read", "Bash", "Glob", "Grep"]` (orchestrator.py:1875), preventing code modification. However, `Bash` still allows arbitrary command execution — a verified test runner could be tricked into running destructive commands. This is acceptable given the phase's purpose but worth noting.

---

## Quality Checklist

- [x] All tests pass (495 passed)
- [x] Code follows existing project conventions
- [x] No secrets or credentials in committed code
- [x] Error handling present for failure cases
- [x] No commented-out code (except the `allowed_user_ids` example in config.yaml, which is intentional documentation)
- [x] No placeholder/TODO implementations
- [x] Input validation on all untrusted data paths
- [x] Defense-in-depth sanitization at multiple layers

---

VERDICT: approve

FINDINGS:
- [src/colonyos/agent.py:52]: All phases run with `permission_mode="bypassPermissions"` — this is the fundamental trust boundary. Prompt injection from Slack messages can achieve arbitrary code execution. Mitigations (XML stripping, role anchoring, delimiters) are probabilistic defenses.
- [.colonyos/config.yaml]: `allowed_user_ids` is commented out, meaning any channel member can trigger pipelines by default. The code warns about this (config.py:223-228, 236-241) but the shipped default is permissive.
- [src/colonyos/slack.py:1045]: `app_token` is read from environment at runtime rather than cached — good. But the agent process itself has full environment access via Bash, so token exfiltration via prompt injection remains theoretically possible.
- [src/colonyos/orchestrator.py:1875]: Verify phase restricts tools but still includes `Bash`, which can execute arbitrary commands. Acceptable trade-off since test runners require shell access.
- [src/colonyos/sanitize.py:18]: XML tag sanitization regex handles well-formed tags but may miss edge cases (partial tags, Unicode confusables). Defense-in-depth layering mitigates this.
- [src/colonyos/cli.py:2057]: Audit logging is present and structured but relies on Python logging with no guaranteed immutable storage or centralized forwarding.

SYNTHESIS:
This is a well-architected security implementation for the threat model it operates under. The team has applied defense-in-depth consistently: input sanitization at ingestion and again at point of use, role-anchoring preambles, strict git ref validation, HEAD SHA verification, rate limiting, budget caps, and structured audit logging. The fundamental tension — untrusted Slack input flowing into agents with `bypassPermissions` and full Bash access — is inherent to the product's architecture and cannot be fully mitigated at the application layer. The mitigations are the right ones for this threat model. The `allowed_user_ids` default being permissive is my primary concern for production deployments, but the warning logs make this a conscious operator decision rather than a hidden risk. I recommend approval with the advisory that production deployments MUST configure `allowed_user_ids` and operators should understand that prompt injection defenses are probabilistic, not deterministic.
