security-review

name	security-review
description	Complete a security review of pending changes on the current branch. Focuses on unsafe code, injection, secrets, memory safety at FFI boundaries, insecure deserialization, path traversal, and supply-chain risk. Use when the user asks to "security review", "security audit", "check for vulns", or before raising a PR.

Security Review Skill

You are conducting a security review of the changes on this branch. The goal is to find real, exploitable issues — not produce a generic checklist.

Step 1 — Determine review scope

1. If the user names a PR, fetch via gh pr diff <n>.
2. Otherwise review branch vs main:

   base=$(git merge-base HEAD main)
   git diff "$base"...HEAD --name-only
   git diff "$base"...HEAD
   

3. If neither produces a diff, fall back to staged changes (git diff --cached).

State the scope in one sentence.

Step 2 — Gather context

• Read each changed file in full — security bugs hide in surrounding context (where input enters, how output is used, what privileges the process holds).
• Read any CLAUDE.md and .env-template to understand secrets handling and trust boundaries.
• Note any new dependencies added to Cargo.toml / Cargo.lock.

Step 3 — Threat focus

Review for the following classes. For each finding, point to a specific line and describe a plausible attacker action. Vague concerns are not findings.

Unsafe code

• unsafe blocks without a // SAFETY: comment that justifies all invariants.
• Raw pointer dereference from untrusted sources (network, file, env).
• transmute between non-trivially-related types.
• FFI boundaries that accept user-controlled sizes or pointers without validation.
• Use-after-free patterns in manual lifetime management.

Injection — command execution

• std::process::Command where any argument is built from user input without allowlisting.
• Shell expansion via sh -c with unsanitised input.

Injection — query/template

• SQL: string concatenation into queries instead of parameterised statements (sqlx, diesel).
• Format strings built from user-controlled data passed to log macros (log injection / log forging).

Deserialisation

• serde deserialising untrusted input into types that execute logic in Deserialize impls.
• bincode / rmp-serde / postcard decoding of untrusted bytes without length limits.
• serde_yaml::from_str with untrusted YAML (YAML merge keys can cause unexpected behaviour).
• std::io::Read without a size cap on untrusted streams (memory exhaustion).

Path traversal & file handling

• std::fs::File::open(user_input) or std::path::Path::join(user_input) without canonicalisation and prefix check.
• Zip/tar extraction using paths from the archive without strip/containment (zip_extract, tar crate).

AuthN / AuthZ

• New endpoints or handlers lacking auth checks present on siblings.
• Authorisation decisions made on client-supplied IDs without ownership verification (IDOR).
• Hardcoded credentials, API keys, or default passwords in source or config.
• Token/session handling: weak generation (rand::random instead of rand::rngs::OsRng), missing expiry.

Secrets & data exposure

• Secrets committed to the repo (high-entropy strings, AKIA*, ghp_*, xoxb-*, PEM blocks).
• Secrets written to logs, error messages, or Display / Debug impls on types that hold credentials.
• Sensitive fields in structs that derive Debug without a custom redacting impl.

Crypto

• MD5 / SHA1 for security purposes (md5 crate, sha1 crate).
• Static IVs, hardcoded keys, ECB mode.
• rand::thread_rng() for security-sensitive tokens — use OsRng.
• TLS verification disabled (danger_accept_invalid_certs, danger_accept_invalid_hostnames).

Integer safety

• Unchecked arithmetic on attacker-controlled values in release mode (overflow wraps silently).
• Casting user-supplied usize to i32 or vice versa without range check.
• Buffer indexing with user-supplied offsets without bounds validation before the index.

Supply chain

• New Cargo.toml dependencies: are they pinned in Cargo.lock? Are they from trusted sources?
• Typosquat-prone names (serdé, actx-web).
• Build scripts (build.rs) — do new deps introduce one? Build scripts run at compile time with full system access.
• cargo audit output: check if any added crate has known CVEs.

Insecure defaults

• Binding to 0.0.0.0 without justification.
• Permissive CORS (*), disabled CSRF.
• debug_assertions-gated checks that should also run in release.

Race conditions & TOCTOU

• File existence check followed by open in separate syscalls.
• Mutex lock dropped early (temporary borrow) before a dependent operation completes.
• Arc<Mutex<_>> held across .await (deadlock risk in async context).

Step 4 — Report

Use CVSS-flavoured severity (Critical / High / Medium / Low / Info), ranked by exploitability in this codebase, not the abstract worst case.

## Security Review: <one-line scope>

### Critical
- **`file.rs:42` — <vuln class>**
  Attack: <what an attacker does, concretely>
  Fix: <one-line remediation>

### High
- ...

### Medium
- ...

### Low / Info
- ...

### Out of scope / accepted
<things you considered but ruled out — terse, only if non-obvious>

### Verdict
<one sentence: safe to ship / fix blockers first / needs broader threat modelling>

Rules:

• Always cite file:line. No findings without a concrete location.
• A "finding" needs a plausible attacker and a plausible impact. If you can't write the Attack line, it's at most an Info note.
• Do NOT pad with generic advice the reader already knows.
• If the diff is security-clean, say so in one line and end with the Verdict.

Step 5 — If invoked from /pr

When the caller is /pr, your output is embedded in the PR body's Security notes section. Keep the report self-contained — anyone reading the PR should understand each finding without running the skill themselves.