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.
- Introduce DrmScheme enum (Css/Aacs10/Aacs20/Aacs21) + drm module with
uniform detect/load dispatch across all four protection schemes.
- Land AACS 2.1 Media Key Variant framework in aacs::variants: chain
derivation, MKB record types 0x82/0x83, bit-0x02 SoftKCD and bit-0x04
online-challenge detection. Aacs21 dispatcher arm wired but commented
out pending validation against a Variant-scheme disc.
- Replace aacs2: bool with AacsVersion enum across ContentCertificate,
UnitKeyFile, ResolvedKeys. resolve_keys splits into _v1/_v2/_v21.
- Delete the libredrive raw-read VID shortcut from do_handshake; the
drive enforces the AGID requirement regardless of firmware-upload
state, so the shortcut spuriously dispatched E7017 instead of
surfacing the real downstream walls.
MattJackson