pq/libfreemkv
1
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

aacs: target real AACS 2.1 Variant MKB records (0x2d/0x2f/0x0c)

Browse Source 
The Media Key Variant scheme is detected and parsed via the actual MKB
record types found on a real variant disc:
  - 0x2d  Encrypted Media Key Variant Data (C)
  - 0x2f  Variant Key Data table (65,535 x 16)
  - 0x0c  variant cvalues (one per 0x04 subset-difference slot)

Replaces the earlier placeholder 0x82/0x83 record types, which were a
guess and appear on no real MKB. is_variant_mkb, the record finders, and
the subset-difference cvalue source (now 0x0c, falling back to 0x07/0x05)
are updated accordingly, along with the V20->V21 upgrade detection in
resolve_keys_v2 and its fixtures.

The variant chain still halts at variants_for_uv (the VARIANTS[uv] /
Nonce sub-field offsets need a covering key to confirm end-to-end
against the 0x86 verify), so a best-effort offset is never silently
trusted. All 27 variant tests pass on Rust 1.86.
This commit is contained in:
Matthew Jackson
2026-07-03 13:25:01 -07:00
parent 61b6070f03
commit eb23ab4586
2 changed files with 108 additions and 79 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/aacs/keys.rs
+6 -5
View File
@@ -9,8 +9,9 @@ use super::types::DeviceKey;
///
/// The content cert byte distinguishes V10 (`0x00`) from V20 (`0x01`). V21
/// cannot be detected from the cert alone — a V21 disc carries a V20 cert
/// and is upgraded to `V21` only after the MKB walk turns up record types
/// `0x82` / `0x83` (Media Key Variant Data and Variant Number).
/// and is upgraded to `V21` only after the MKB walk turns up the real Variant
/// records `0x2d` / `0x2f` (Encrypted Media Key Variant Data and the Variant
/// Key Data table).
///
/// Key-storage stride in `Unit_Key_RO.inf` is 48 bytes for V10 and 64
/// bytes for V20 / V21.
@@ -1103,7 +1104,7 @@ pub fn resolve_keys_v1(ctx: &ResolveContext<'_>) -> Option<ResolvedKeys> {
/// AACS 2.0 key resolution. Parses `Unit_Key_RO.inf` with 64-byte
/// stride. Tries paths 1 → 4 in order. When paths 3/4 succeed against
/// an MKB carrying Variant records (`0x82` / `0x83`), the result's
/// an MKB carrying Variant records (`0x2d` / `0x2f`), the result's
/// `version` is upgraded to [`AacsVersion::V21`] — derivation still
/// runs through the classical V2 path; the V21-specific Variant chain
/// is wired separately via [`resolve_keys_v21`].
@@ -2595,9 +2596,9 @@ mod tests {
}),
};
// MKB with a 0x83 variant record makes is_variant_mkb true.
// MKB with a 0x2f variant record makes is_variant_mkb true.
let mut mkb = vec![0x10, 0x00, 0x00, 0x08, 0, 0, 0, 1];
mkb.extend_from_slice(&[0x83, 0x00, 0x00, 0x14]);
mkb.extend_from_slice(&[0x2f, 0x00, 0x00, 0x14]);
mkb.extend_from_slice(&[0x55; 16]);
let providers: &[&dyn super::super::KeyProvider] = &[&keydb];