Security review

Security Review

Attackers send the inputs you didn't imagine. This pass walks the code from the attacker's side of every trust boundary. Work the checklist concretely — for each item either point to the line that handles it or record its absence as a finding.

Step 1: Map the trust boundaries and data flow

List every point where external data enters: HTTP params/body/headers/cookies, CLI args, file contents, env vars, message-queue payloads, third-party API responses, uploaded files. For each, trace where the data GOES — into a query? a shell command? a file path? an HTML response? a deserializer? The dangerous combination is always untrusted-source → sensitive-sink. Find the sinks.

Step 2: Run the vulnerability checklist

For each, find the handling line or log a finding:

1. Injection — the sink test. Every sink gets checked:
   • SQL/NoSQL: parameterized queries / bound params ONLY. Any string-built query with external data = SEC-CRITICAL. ORMs help but raw-query escape hatches don't.
   • OS command: no shelling out with interpolated input; use execFile/subprocess with an arg array and shell=False; never shell=True with user data.
   • Path traversal: user-influenced file paths are resolved and confirmed within an allowed base dir; ../ is neutralized. Never open(base + user_input).
   • Template/HTML: output encoding on by default; find every raw/dangerouslySetInnerHTML/ |safe/v-html sink and confirm the input is trusted or sanitized (XSS).
2. AuthN/AuthZ. Every non-public endpoint checks authentication AND authorization. The frequent hole is authz: authenticated user A can act on user B's resource (IDOR) — confirm ownership/role is checked against the RESOURCE, not just that someone is logged in. Never trust a client-supplied role/ID for access decisions.
3. Secrets exposure. No hardcoded keys/tokens/passwords/connection strings. No secrets in logs, error messages, or client responses. Stack traces and internal paths never reach the client (generic message out, detail to server logs).
4. Unsafe deserialization. No pickle/yaml.load (unsafe loader)/Java native deserialization/eval/Function() on untrusted data. Use safe parsers (JSON, yaml.safe_load).
5. Input validation at the boundary. Type, length, range, format validated where data enters, allowlist over denylist. Unbounded input (huge body, deep JSON, giant upload) is bounded — absence is a DoS vector.
6. SSRF and outbound requests. URLs built from user input for server-side fetches are validated against an allowlist; internal/metadata addresses (169.254.169.254, localhost, RFC1918) are blocked.
7. Crypto and identifiers. No MD5/SHA1 for passwords (use argon2/bcrypt/scrypt); tokens and IDs from a crypto-secure RNG (secrets, crypto.randomBytes), never Math.random/ random.random; TLS verification never disabled.
8. Transport and session. State-changing endpoints protected against CSRF where cookie-based; auth cookies HttpOnly+Secure+SameSite; tokens not in localStorage if XSS is reachable.

Step 3: Adapt to the stack

Layer the ecosystem's specific classes on top:

• Node/TS: prototype pollution (Object.assign/merge from user JSON), child_process misuse, regex catastrophic backtracking (ReDoS), missing helmet.
• Python: yaml.load, subprocess(shell=True), pickle, Jinja2 SSTI, Flask debug=True in prod, assert used for security checks (stripped under -O).
• SQL/Postgres: dynamic SQL in functions, over-broad role grants, RLS assumed but not enabled.
• Run the stack's audit tool as corroboration, not substitute: npm audit, pip-audit, cargo audit, and a SAST pass (semgrep) if available — read findings, don't just paste them.

Step 4: Report by severity, with fixes

Rank findings; each gets file:line, the concrete exploit ("attacker sends ?id=../../etc/passwd → reads arbitrary files"), and the specific fix — not "sanitize input" but "use Path(base).joinpath(name).resolve() and assert it's relative to base".

• CRITICAL: directly exploitable for data breach / RCE / auth bypass. Block delivery.
• HIGH: exploitable under realistic conditions (stored XSS, IDOR on sensitive data). Fix before merge.
• MEDIUM: increases attack surface, not directly exploitable (missing rate limit, verbose errors). Log and schedule.
• LOW/INFO: best-practice gaps, defense-in-depth.

Worked example finding

SEC-CRITICAL  api/reports.js:47  SQL injection
  Code: db.query(`SELECT * FROM reports WHERE owner='${req.query.user}'`)
  Exploit: ?user=' OR '1'='1  → dumps all reports; ?user='; DROP TABLE... → destructive.
  Fix: db.query('SELECT * FROM reports WHERE owner = $1', [req.query.user])
  Plus (SEC-HIGH, same line): no authz — any caller reads any owner's reports. Check
  req.query.user === session.userId (or a role grant) before querying.

Done when

Every external-input boundary has been traced to its sinks; every checklist item is either tied to a handling line or logged as a finding; findings are ranked with file:line, a concrete exploit, and a specific fix; and no CRITICAL finding is left un-flagged. Reporting is sufficient — do not fix beyond the task's scope without saying so (integrity-guardrails rule 7).