## Summary
- Adds `ENCRYPTION_KEY` (primary) and `FALLBACK_ENCRYPTION_KEY`
(decrypt-only fallback for rotation) env vars to twenty-server, with
backward-compatible fallback to `APP_SECRET` when `ENCRYPTION_KEY` is
unset.
- Introduces a versioned ciphertext envelope `enc:v2:<keyId>:<base64>`
using AES-256-GCM with HKDF-SHA256 derived per-context keys. The 8-hex
`keyId` fingerprint lets every row identify which physical key encrypted
it, so rotation routes directly to primary or fallback without trial
decryption; GCM's auth tag gives true integrity (legacy CTR has none).
- Migrates `ConnectedAccountTokenEncryptionService` to the new envelope
and plumbs `workspaceId` through every caller, so per-workspace HKDF
context binds each row to its tenant.
The remaining encryption sites (`jwt-key-manager`, `config-storage`,
`postgres-credentials`, `application-variable`, TOTP) stay on the legacy
unprefixed CTR path and will be migrated in follow-up PRs. The
operator-facing rotation runbook is out of scope here.
### Format details
`enc:v{N}:{keyId}:{base64}` — `N=2` is the only version produced by new
writes (`v1` exists for backward-compatible decryption of existing
connected-account rows). `keyId =
sha256(rawKey).slice(0,4).toString('hex')`. The CHECK constraint on
`core.connectedAccount.{accessToken,refreshToken}` is relaxed from `LIKE
'enc:v1:%'` to `LIKE 'enc:v_:%'` so both versions pass.
### Key resolution
| `ENCRYPTION_KEY` | `FALLBACK_ENCRYPTION_KEY` | `APP_SECRET` | Encrypt
with | Decrypt try order |
|---|---|---|---|---|
| set | set | (any) | `ENCRYPTION_KEY` | match `keyId` → primary →
fallback |
| set | unset | (any) | `ENCRYPTION_KEY` | match `keyId` → primary |
| unset | set | set | `APP_SECRET` | match `keyId` → `APP_SECRET` →
fallback |
| unset | unset | set | `APP_SECRET` | match `keyId` → `APP_SECRET` |
| unset | unset | unset | startup error | n/a |
## Test plan
- [x] `npx nx typecheck twenty-server` — clean
- [x] `npx jest
'secret-encryption|connected-account-token-encryption|connected-account-refresh-tokens|encrypt-connected-account-tokens|connection-provider-oauth-flow'`
— 87 tests pass
- [x] New `secret-encryption.service.versioned.spec.ts` covers: key
resolution table (no-key error, APP_SECRET fallback, ENCRYPTION_KEY
precedence), v2 round-trip with/without workspaceId, GCM tamper
rejection, workspaceId-mismatch rejection, keyId-based primary→fallback
routing, missing-key error names the fingerprint, v1 legacy decryption,
no-prefix legacy decryption, malformed envelope rejection.
- [x] Updated `connected-account-token-encryption.service.spec.ts`
covers workspaceId binding and HKDF context isolation.
- [x] Updated slow instance command spec verifies workspaceId is
threaded through encryption and the relaxed `enc:v_:%` LIKE pattern
matches both v1 and v2.
- [ ] Manual E2E: connect a Gmail account on a freshly deployed instance
with `APP_SECRET` only → confirm `core.connectedAccount.accessToken` is
`enc:v2:<keyId>:<base64>`.
- [ ] Manual E2E: rotate — set `ENCRYPTION_KEY=<new>` and
`FALLBACK_ENCRYPTION_KEY=<old APP_SECRET>`, restart, confirm
pre-rotation rows still decrypt and new rows carry the new `keyId`.
- [ ] Manual E2E: missing key — set `ENCRYPTION_KEY=<new>` without the
fallback, confirm decrypt error names the old `keyId` so the operator
can identify the missing key.
