Five issues that together caused keystore-pinned apps to be silently
logged out across reboots and config changes. All flow from the same
root cause: GeneratedKeyPersistence loses information on save -> reload.
1. Symmetric keys (AES, HMAC, 3DES) were never persisted at all
- GeneratedKeyPersistence.save only accepted KeyPair, ignoring SecretKey
- AndroidX security MasterKey (AES-GCM-256) regenerated on every
reboot, making EncryptedSharedPreferences undecryptable
- Apps that wrap session tokens in EncryptedSharedPreferences
interpret this as session expiry and force a relogin
2. Restored KeyMetadata authorizations differed from generation-time bytes
- loadPersistedKeys rebuilt KeyMintAttestation with mostly null/empty
fields, so toAuthorizations emitted a different tag set after
reboot vs. at generateKey time
- Apps that fingerprint metadata across keystore calls saw a
"changed key"
3. certificate / certificateChain split could shift after restore
- buildKeyEntryResponse called updateCertificateChain on the rebuilt
metadata, which is allowed to repartition leaf vs. chain bytes
- Apps with strict leaf fingerprint checks saw a "changed cert"
4. Touching ANY .xml under /data/adb/tricky_store wiped every cached key
- ConfigObserver called clearAllGeneratedKeys() which also calls
GeneratedKeyPersistence.deleteAll()
- Editing keybox.xml (or any unrelated .xml) thus deleted every
persisted key on disk
- Even the keybox-cache argument does not justify wiping per-app keys:
patched chains alone are stale, raw keypairs are not
5. SoftwareOperation NPE when restored keyParams missed PURPOSE tag
- Init dereferenced keyPair!! before checking purpose, so a
half-restored record crashed instead of producing a clean error
Single on-disk format (FORMAT_VERSION = 3) covers everything: PKCS8
private key bytes for asymmetric, raw secret bytes for symmetric, plus
the byte-identical KeyMetadata parcel snapshot so authorizations
restore exactly. Earlier dev-only formats are silently skipped by the
loader; the next generateKey for those aliases re-creates them in v3.
ConfigObserver now calls invalidatePatchedChains() instead of
clearAllGeneratedKeys() on .xml edits - only the chain cache is
stale, not the underlying keypairs.
Tested on OnePlus 13 (Android 16, KSU 3.2.4):
- Apps survive force-stop + cold reboot without losing keystore state
- Apps survive keybox.xml edits / replacements (touch, sed, cp -mv)
- Tamper score still 4 (CONSISTENT) on Duck Detector
- KeyAttestation chain output unchanged
Duck Detector's 'TEE Simulator generate-mode fingerprint' probe scans the
generateKey reply parcel for a 16-byte marker where the securityLevel byte
is 0x00 (SOFTWARE). Real KeyMint HAL uses 0x64 (KEYSTORE=100) for
keystore-enforced metadata (creation time, user ID, etc.).
This single-line change aligns with real hardware behavior and defeats
the probe. Tested on OnePlus 13 (Android 16, KSU 3.2.4):
- Before: 'TEE Simulator generate-mode fingerprint: Matched' (score 50)
- After: 'No TEE Simulator generate-mode fingerprint observed' (score 4)
Reference: https://github.com/eltavine/Duck-Detector-Refactoring/commit/e368038
Andrea-lyz