input-validation-hardening

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name: input-validation-hardening description: Process for tightening input validation, canonicalization, and safe parsing to prevent injection and logic abuse.

Use this skill when asked to validate inputs, harden request parsing, or prevent injection/abuse.

Step-by-step process

1. Inventory inputs
   • HTTP params/body/headers, file uploads, message payloads, env vars, CLI args
2. Define schemas
   • Prefer typed schemas (DTOs) and allow-lists
   • Enforce length, charset, ranges, and required fields
3. Canonicalize early
   • Normalize encoding, trim, and apply consistent parsing (dates, IDs, enums)
4. Validate before use
   • Reject unknown fields if possible
   • Ensure IDs map to authorized resources (ownership/tenant checks)
5. Protect sinks
   • Parameterize DB queries
   • Avoid dynamic execution (eval, shell, template injection)
6. Add tests
   • Boundary tests (min/max), malformed inputs, and common payloads

Output

• Proposed schema(s)
• Where to enforce validation (middleware/controller boundary)
• Tests added/updated

Repo integration (optional)

Related prompts:

• validate-input-handling.prompt.md
• scan-for-insecure-apis.prompt.md