sql-security

SQL Security

Use this when a project ships SQL through host code (MoonBit / TS / Rust / Go) and wants a cheap line of defence against the two recurring sources of SQL-domain incidents:

1. SQL injection: a string template that interpolates a value into a SQL fragment instead of binding it through a placeholder.
2. Secrets in queries: a hardcoded token or connection string that leaks into git history. Handled by secretlint, not this skill — see "Companion: secretlint" below.

sql-injection-scan.mjs

node scripts/sql-injection-scan.mjs your-project/src

The scanner walks the directory, ignores generated files (db/gen/, sqlc_*.mbt, *.test.mbt, _build/, dist/, target/), and flags:

• template-interp: a backtick string literal that starts with a SQL keyword (SELECT, INSERT INTO, WHERE, AND (, ...) AND contains a ${...} placeholder. Example: `WHERE c.vector_id IN (${placeholders})`.
• string-concat: a quoted SQL string adjacent to a + and an identifier. Example: "SELECT * FROM " + table.

The keyword match is case-sensitive on purpose — from / where / join appear constantly in English prose and would generate hundreds of false positives if matched case-insensitively.

The scanner exits 1 on findings — every hit deserves a manual review even if it turns out to be safe.

Limitations — a clean scan is NOT proof of safety

The scanner reads one line at a time. Its template-literal rule requires the opening backtick, the ${...} placeholder, and the closing backtick to all sit on a single physical line. Consequences:

• Multi-line template literals are silently missed. A query whose backtick opens on one line and whose ${value} lands on a continuation line (a common formatting style) produces zero findings and exit 0, even though it is a genuine injection. Example the scanner does NOT catch:

  const sql = `
    SELECT id FROM users
    WHERE name = ${name}   // <-- real injection, not flagged
  `;
  

• Exit 0 means "no single-line hits found," never "safe." When reviewing for SQL injection, also read any multi-line or programmatically-assembled SQL by hand; do not treat a clean scan as a pass. Fold a multi-line query onto one line if you want the scanner to see it.

This is a deliberate cost/coverage trade-off (zero-dep, no parser), not a bug — but it is a blind spot you must compensate for in review.

Reading the findings

A finding does not automatically mean injection. Many legitimate cases exist:

• Internal placeholder expansion: building ?,?,?,...,? for an IN clause from a server-derived count. The interpolated value is ?, never user input. Annotate with the opt-out comment so future scans can ignore it.
• FTS5 / vector queries that sqlc cannot parse: dynamic clause builders that interpolate column lists or ? counts. User input still passes through .bind(...).
• Inline migration scripts building DDL at deploy time.

The scanner is intentionally noisy because the cost of missing one real SQLi is much higher than the cost of triaging a list of 5 false positives.

Opt-out marker

To silence a known-safe line, add a comment with the marker sql-security: ok either on the same line or on the line above:

// sql-security: ok (placeholders is server-derived `?` count, values bind separately)
const sql = `WHERE c.vector_id IN (${placeholders})`;

The scanner accepts // (TS / MoonBit / Rust / Go) and # (Python / shell) comment markers.

Companion: secretlint

For credential leakage (the other half of "SQL security"), use secretlint. Recommended setup for a pkfire-managed repo's pre-push hook:

pnpm add -D secretlint @secretlint/secretlint-rule-preset-recommend

Then run on pre-push:

pnpm exec secretlint --secretlintignore .gitignore "**/*"

This is per-repo and complements any user-global secretlint configuration. The mizchi/skills/pkfire skill has a ready-made recipe at assets/recipes/14-secretlint-pre-push.pkl for projects using pkfire hooks.

When to invoke

• pre-push: cheap, runs once before sending code to the remote.
• pre-commit: optional. secretlint here can be slow on large diffs; sql-injection-scan is cheap enough.
• PR review: paste the scanner output into the review checklist.

Not in scope

• Stored XSS / template injection: these go through frontend / templating layers, not SQL.
• Authz bypasses: row-level access checks are app logic, not a SQL concern.
• DoS via expensive query: covered by sql-plan-audit (look for new SCAN entries) and rate limiting at the edge.

Engine extensibility

The scanner regex is engine-agnostic. The SQL-keyword set works for SQLite / Postgres / MySQL out of the box. Add RETURNING / OVERLAPS / LIMIT OFFSET if a Postgres-heavy project needs broader coverage.

Requirements

• Node 20 or newer.

Files

• scripts/sql-injection-scan.mjs — zero-dep text scanner.