Security Scrub

security-scrub

Scan content for secrets and sensitive data. Produces a structured SCRUB RESULT block that callers must check before proceeding.

Overview

Six mandatory steps — none can be skipped. The caller (human or skill) provides the content to scan either as inline text or a file path.

Step 1 — Load rules

Read the references/scrub-rules.md file adjacent to this SKILL.md to get the current pattern table, file-path block list, and masking format.

Step 2 — Pattern scan

Run Grep against the content for HIGH, MEDIUM, and LOW patterns from the table. Also check any file paths referenced in the content against the file-path block list.

Key regex groups to scan:

sk-[A-Za-z0-9]{20,}
ghp_[A-Za-z0-9]{36}
ghs_[A-Za-z0-9]{36}
AKIA[A-Z0-9]{16}
xoxb-[0-9]{11}-[0-9]{11}-[A-Za-z0-9]{24}
xoxp-[A-Za-z0-9-]{72,}
eyJ[A-Za-z0-9_-]{20,}\.eyJ
[A-Z_]{3,}=[[:alnum:]_-]{32,}
password\s*[=:]\s*\S{4,}
secret\s*[=:]\s*\S{4,}
token\s*[=:]\s*\S{8,}
api_key\s*[=:]\s*\S{8,}

For the private-key pattern (-----BEGIN ...), pass via -e to avoid the leading dash being parsed as a grep option:

grep -E -e '-----BEGIN (RSA|EC|OPENSSH|PGP) PRIVATE KEY'

File path patterns to block: .env, credentials, id_rsa, .pem, ~/.ssh/, ~/.aws/credentials

Step 3 — Classify findings

Classify each match as HIGH / MEDIUM / LOW per the pattern table in references/scrub-rules.md.

• Any HIGH finding → overall result is BLOCKED
• Any MEDIUM finding with no HIGH → overall result is WARN
• LOW findings only (no HIGH or MEDIUM) → overall result is PASS; list findings as informational notes
• No findings → overall result is PASS

Step 4 — Mask values before reporting

For any matched value: show first 4 chars + *** + last 4 chars. Example: sk-abcdefgh1234wxyz → sk-a***wxyz

Never output unmasked secret values.

Step 5 — Emit structured report

Output exactly this block (fill in the brackets):

SCRUB RESULT: [PASS | BLOCKED | WARN]
---
Findings:
  - [HIGH|MEDIUM|LOW] <pattern-name>: <masked-value> (line N)
ALLOWLIST verdict: [PASS | BLOCKED]
Reason: <one sentence>

If no findings, output:

Findings: none

ALLOWLIST verdict: BLOCKED when the content originates from a blocked file path (see file-path block list). This overrides SCRUB RESULT: PASS.

Callers must treat SCRUB RESULT: BLOCKED or ALLOWLIST verdict: BLOCKED as a hard stop — do not proceed with sharing.

Step 6 — User gate

After emitting the SCRUB RESULT block, apply the appropriate gate based on the result. Emit a GATE RESULT line at the end so callers have a machine-readable signal.

BLOCKED (SCRUB RESULT: BLOCKED or ALLOWLIST verdict: BLOCKED):

• Do NOT call AskUserQuestion.
• Output: GATE RESULT: BLOCKED — hard stop. Sharing is not permitted.
• Return immediately. The caller must not proceed.

WARN (MEDIUM findings, no HIGH):

• Call AskUserQuestion with one question:
  • Header: Security warning
  • Question: The security scan found potential issues (see MEDIUM findings above). Are you sure you want to continue?
  • Options: Continue anyway (description: "Proceed despite warnings — review findings first") / Cancel — stop here (description: "Abort sharing; no content will be sent")
• If user selects Cancel: output GATE RESULT: CANCELLED — user declined to proceed. and return.
• If user selects Continue anyway: output GATE RESULT: APPROVED. and return.

PASS with LOW findings only:

• Call AskUserQuestion with one question:
  • Header: Scrub passed
  • Question: Security scan passed with informational notes (see LOW findings above). Continue?
  • Options: Continue (description: "Proceed with sharing") / Cancel (description: "Abort sharing")
• If user selects Cancel: output GATE RESULT: CANCELLED — user declined to proceed. and return.
• If user selects Continue: output GATE RESULT: APPROVED. and return.

PASS with no findings:

• Do NOT call AskUserQuestion.
• Output: GATE RESULT: APPROVED (clean — auto-proceeding).
• Return immediately.