Observed an abnormal Keymaster attestation structure on certain Android 11 devices where the `softwareEnforced` and `teeEnforced` authorization lists were swapped in order. This is a deviation from the documented specification and the behavior seen on most devices.
This non-compliance caused parsing failures, as the code expected the `teeEnforced` list to be at a fixed index (7). On the affected devices, this index contained the `softwareEnforced` list, which critically lacks the `TAG_ROOT_OF_TRUST` needed for successful validation and patching.
This commit introduces a defensive normalization step to handle this device-specific anomaly gracefully:
1. Before parsing, the code now inspects the ASN.1 sequence at the expected `softwareEnforced` index (6).
2. It checks for the presence of the `TAG_ROOT_OF_TRUST`, which can only exist in the TEE-enforced list.
3. If the tag is found, the code concludes the lists are swapped and corrects the `allFields` array in-place by swapping the elements at indices 6 and 7.
By normalizing the data structure at the beginning, the rest of the parsing and patching logic can proceed without modification, ensuring correct operation on both compliant and non-compliant devices.
JingMatrix
d60ad8fe47