feat: add field-level encryption for PII

[kevinrutledge]

Developer

Kevin Rutledge

What changed?

Added AES-256-GCM field-level encryption for PII stored in the Referral, EmailSuppression, and SmsConsent tables. Encrypted fields are stored as base64url ciphertext. Lookup tables (EmailSuppression, SmsConsent) use HMAC-SHA256 blind indexes for exact-match queries without decrypting. Also ran npm audit fix to resolve 18 of 19 dependency vulnerabilities.

New files:

• src/lib/encryption.ts - encrypt(), decrypt(), blindIndex() using Node.js crypto
• test/lib/encryption.test.ts - 13 tests for round-trip, tamper detection, blind index determinism
• test/mocks/encryption.ts - shared passthrough mock for service/action/API tests
• scripts/migrate-encrypt-pii.ts - one-time data migration script for existing rows

Modified:

• prisma/schema.prisma - widened PII columns to VarChar(512), added emailHash/phoneHash columns, updated indexes
• src/services/referral.ts - encrypt on write, decrypt on read for 4 PII fields
• src/services/email-suppression.ts - blind index lookups, encrypted email storage
• src/env.ts - added FIELD_ENCRYPTION_KEY and BLIND_INDEX_KEY env vars

How to test

1. Add encryption keys to .env.local: openssl rand -hex 32 for each of FIELD_ENCRYPTION_KEY and BLIND_INDEX_KEY
2. Run npm test - 237 tests pass (14 new encryption tests)
3. Run npm run build - build succeeds
4. Run npx tsc --noEmit - zero type errors
5. Start dev server, submit a referral form, inspect the referral table - PII fields should contain base64url ciphertext, not plaintext
6. Run npm audit - down to 1 low-severity vulnerability (nodemailer, requires breaking major version)

Checklist

• Code works and is readable
• Tested locally
• Commits follow conventional commits
• Assigned reviewers