AOSP KeyMint only includes the attestation extension (OID
1.3.6.1.4.1.11129.2.1.17) when ATTESTATION_CHALLENGE is present.
Without a challenge, generateKey produces a plain self-signed cert.
Our code unconditionally added the extension, which behavioral
probes detect by generating a key without a challenge and checking
for the OID.
Fixes both the Rust native-certgen and BouncyCastle paths.
Also skips AAID computation when no challenge is provided,
matching keystore2 security_level.rs:457 behavior.
Leaf cert Subject CN used "KeyStore" (capital S) but AOSP
KeyGenParameterSpec uses "Keystore" (lowercase s). Fixed in both
the Rust native certgen and BouncyCastle paths.
Replicate keystore2's security_level.rs parameter validation for
software-generated keys: reject CREATION_DATETIME (output-only tag,
ResponseCode 20) and device ID attestation tags (CANNOT_ATTEST_IDS
-66) that real keystore2 blocks before they reach the HAL.
Also fix createErrorReply parcel write order, AIDL protocol expects
exception_code, message, error_code but we had message and error_code
swapped, causing malformed replies for positive error codes.
DuckDetector flagged two issues:
1. Oversized challenge accepted, 256-byte attestation challenge should
return INVALID_INPUT_LENGTH (-21) like real KeyMint. Added early check
in handleGenerateKey before any path decision.
2. Issuer/subject chain mismatch, rcgen's HashMap loses DN attribute
ordering and converts PrintableString to UTF8String, producing
different DER bytes. Replaced rcgen with manual DER assembly that
injects raw keybox issuer_dn_der bytes directly.
Verified on device: TX_ID 315 rejects 256-byte challenge, TX_ID 501
generates valid 4-cert chain with correct issuer linkage.
Remove ENCRYPT/VERIFY from KeyUsage mapping to match Kotlin behavior.
Document BasicConstraints and SKI suppression via rcgen NoCa default.
Fix rotating log off-by-one that kept one extra backup file. Handle
BMPString (UTF-16BE) and VisibleString in X.500 DN parser.
Builds v3 leaf certificate with attestation extension and KeyUsage,
signs with keybox private key via rcgen 0.13.2. Assembles full chain
(leaf + keybox intermediates + root). Supports EC and RSA keybox
signing keys. Uses rcgen's signed_by() with a synthesized issuer
Certificate, no manual DER fallback needed.
Enginex0