Two coherent additions to the AACS resolver:
KeyProvider abstraction (provider.rs) — key material comes from pluggable
backends; KeyDb implements it (device/processing keys, host certs,
disc-by-hash / disc-by-vid lookup) plus orphan-DK parsing. ResolveContext
takes a provider array. Adds the SD-tree PK walker
(derive_media_key_from_pk_walked) and a `probe` module (km_verifies MK
oracle, mkb_* record parsers) used for offline key verification. Cvalue
record selection prefers 0x05, falls back to 0x07.
External-UK key source — the second, mutually-exclusive key source for the
keyserver path. ScanOptions/InputOptions gain `unit_key`; when set,
resolve_encryption_static skips keydb entirely and uses the caller-supplied
Unit Key directly (KeySource::ExternalUk). Disc::read_aacs_inputs exposes a
disc's Unit_Key_RO.inf + MKB so a caller can fetch the UK out-of-band; the
library makes no network call itself.
CHANGELOG: redact test-disc title in historical notes.
MattJackson
8d54a3c64e