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disc: credit firmware unlock in the bus-encryption gate

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The bus-key gate only credited the cert handshake's read_data_key as proof
bus encryption was removed. A firmware unlocker removes it AT THE DRIVE
(serves clear content) and yields no read_data_key — so a SUCCESSFUL
firmware unlock (VID present, read_data_key None) tripped the gate and
blocked ALL key resolution, including the online source. That was the
root cause of live UHD discs reporting "missing keys" after an unlock.

Now a single predicate answers "is bus encryption gone?": never-had-it ||
file/ISO || firmware-unlocked || cert-bus-key. The gate is just
`if !bus_encryption_removed { error }` — no enumerated cases. HandshakeResult
gains `drive_unlocked`, and the read_data_key failure reason is captured so
the warn says WHY the bus key is missing.

Also: reword the first hardware-sense escalation as "fast-fail escalation"
(it is often transient — the drive recovers), reserving "wedge" for a
persistent run; and scrub the product name from core comments (it belongs
only in the unlocker crate).
This commit is contained in:
Matthew Jackson
2026-06-29 15:09:16 -07:00
parent 263950622f
commit a7c8ee09b0
5 changed files with 111 additions and 41 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/disc/encrypt.rs
+86 -36
View File
@@ -17,6 +17,36 @@ pub(super) struct HandshakeResult {
/// instead of a bare "unavailable" — the difference between a diagnosable log
/// and archaeology.
pub read_data_key_err: Option<u16>,
/// True when the VID came from a firmware unlocker (`freemkv-unlock-ld`
/// et al.) that unlocked the drive. Such a drive serves CLEAR
/// content, so AACS bus encryption is already removed AT THE DRIVE — the same
/// end state a successful cert handshake's `read_data_key` provides, just via
/// firmware instead of the AKE. The bus-key gate MUST credit this as a valid
/// bus-removal: bus encryption is unremovable only when NEITHER the firmware
/// unlocked the drive NOR the cert handshake yielded a bus key. Without this,
/// a SUCCESSFUL unlock (VID present, `read_data_key: None`) paradoxically trips
/// the gate and blocks ALL key resolution (incl. the online source).
pub drive_unlocked: bool,
}
/// Single source of truth for "is AACS bus encryption gone for this scan?". The
/// gate asks ONLY this — `if !removed { error }` — never enumerating cases. Bus
/// encryption is gone when ANY of these holds:
/// - the disc never had it (`!bus_encryption`): nothing to remove;
/// - file/ISO reads (`handshake == None`): content is already clear at read time;
/// - a firmware unlocker unlocked the drive (`drive_unlocked`): it serves clear
/// content;
/// - the cert handshake produced the bus key (`read_data_key`).
///
/// Add a NEW removal mechanism HERE, never in the gate.
fn bus_encryption_removed(bus_encryption: bool, handshake: Option<&HandshakeResult>) -> bool {
if !bus_encryption {
return true; // never had it → nothing to remove
}
match handshake {
None => true, // file/ISO: clear at read time
Some(h) => h.drive_unlocked || h.read_data_key.is_some(),
}
}
/// In-tree AACS host-certificate cert-auth "unlocker" — the Drive-level peer of
@@ -103,21 +133,22 @@ impl AacsCertUnlocker<'_> {
return Err(UnlockError::VidUnavailable);
}
};
let (read_data_key, read_data_key_err) =
match aacs::handshake::read_data_keys(session, &mut auth) {
Ok((rdk, _)) => (Some(rdk), None),
Err(e) => {
tracing::debug!(
target: "freemkv::disc",
phase = "handshake_read_data_key_failed",
cert_index = idx,
error_code = e.code(),
"auth + VID read OK, but the drive served no read_data_key (bus key); \
a bus-encrypted disc stays undecryptable until it does"
);
(None, Some(e.code()))
}
};
let (read_data_key, read_data_key_err) = match aacs::handshake::read_data_keys(
session, &mut auth,
) {
Ok((rdk, _)) => (Some(rdk), None),
Err(e) => {
tracing::debug!(
target: "freemkv::disc",
phase = "handshake_read_data_key_failed",
cert_index = idx,
error_code = e.code(),
"auth + VID read OK, but the drive served no read_data_key (bus key); \
a bus-encrypted disc stays undecryptable until it does"
);
(None, Some(e.code()))
}
};
tracing::debug!(
target: "freemkv::disc",
phase = "handshake_ok",
@@ -130,6 +161,9 @@ impl AacsCertUnlocker<'_> {
volume_id,
read_data_key,
read_data_key_err,
// Host-cert AKE path: bus removal depends on read_data_key,
// NOT a firmware unlock.
drive_unlocked: false,
});
}
Err(e) => {
@@ -294,6 +328,10 @@ impl Disc {
// OEM/VID-only path never attempts the bus-key read — None here
// is "not attempted", not "failed".
read_data_key_err: None,
// The firmware unlocker stashed this VID at init, which means it
// matched and unlocked the drive — it now serves clear content,
// so bus encryption is removed at the drive. Credit it.
drive_unlocked: true,
}),
None,
);
@@ -360,31 +398,39 @@ impl Disc {
.map(|c| c.version.major())
.unwrap_or(aacs::AACS_MAJOR_UHD);
// OEM bus-key gate (wrong-keys guard). A bus-encrypted disc (Content
// Certificate bus-encryption bit set) still carries bus encryption on
// its sectors; descrambling needs the `read_data_key` (bus key), which
// ONLY the AACS host-certificate cert-auth handshake produces. A
// VID-only OEM unlock path returns `read_data_key: None`, and a VID
// alone does NOT remove bus encryption — so if a handshake ran (live
// drive) and yielded a VID but no bus key on a bus-encrypted disc, the
// bytes would decrypt to garbage. Fail loudly here instead.
// Bus-encryption gate (wrong-keys guard). A bus-encrypted disc (Content
// Certificate bus-encryption bit set) carries bus encryption on its
// sectors, which MUST be removed before any AACS key can decrypt them.
// There are TWO ways it gets removed, and bus encryption is unremovable
// only when NEITHER succeeded:
// 1. A firmware unlocker unlocked the drive → it serves
// CLEAR content (`drive_unlocked`). This is the common live-drive
// case and yields no `read_data_key` — it doesn't need one.
// 2. The AACS host-certificate cert-auth handshake produced the bus key
// (`read_data_key`).
// The old gate credited ONLY (2), so a SUCCESSFUL firmware unlock (VID
// present, `read_data_key: None`, `drive_unlocked: true`) tripped it and
// blocked ALL key resolution — including the online source — even though
// the drive was serving clear content. That was the bug.
//
// Gated on `handshake.is_some()` so the two preserved cases never
// regress: (1) file-backed/ISO scans reach here with `handshake = None`
// and have already had bus encryption removed at read time; (2) AACS 1.0
// BD is not bus-encrypted, so `bus_encryption` is false and the gate is
// skipped (its `read_data_key` is legitimately absent).
if bus_encryption && handshake.is_some_and(|h| h.read_data_key.is_none()) {
let h = handshake.expect("is_some_and matched");
// Also skipped when `handshake = None` (file-backed/ISO scans — bus
// encryption already removed at read time) and when `bus_encryption` is
// false (AACS 1.0 BD is not bus-encrypted).
// ONE question — "is AACS bus encryption gone?" — asked of the single
// `bus_encryption_removed` predicate, which OWNS every case (never had it,
// file/ISO, firmware unlock, cert bus key). The gate enumerates nothing.
if !bus_encryption_removed(bus_encryption, handshake) {
let (rdk_err, has_vid) = handshake
.map(|h| (h.read_data_key_err, h.volume_id != [0u8; 16]))
.unwrap_or((None, false));
tracing::warn!(
target: "freemkv::disc",
phase = "bus_key_unavailable",
read_data_key_err = ?h.read_data_key_err,
has_volume_id = h.volume_id != [0u8; 16],
"Disc declares bus encryption but the drive served no read_data_key (bus key). \
read_data_key_err=None ⇒ the unlock path never attempted it (VID-only/OEM); \
a code ⇒ the bus-key read FAILED. Either way bus encryption can't be removed — \
refusing to emit a key that would decrypt to garbage."
read_data_key_err = ?rdk_err,
has_volume_id = has_vid,
"Disc declares bus encryption but it could not be removed: no firmware unlocker \
unlocked the drive AND the cert handshake produced no read_data_key. Refusing to \
emit a key that would decrypt to garbage."
);
return Err(Error::AacsBusKeyUnavailable);
}
@@ -816,6 +862,7 @@ mod tests {
volume_id: vid,
read_data_key: Some(rdk),
read_data_key_err: None,
drive_unlocked: false,
};
let st = Disc::resolve_vid_only(&udf, &mut disc, Some(&hs)).expect("state");
assert_eq!(st.volume_id, vid);
@@ -861,6 +908,7 @@ mod tests {
volume_id: [0x11u8; 16],
read_data_key: None,
read_data_key_err: None,
drive_unlocked: false,
};
let err = Disc::resolve_vid_only(&udf, &mut disc, Some(&hs))
.expect_err("bus-encrypted disc with no bus key must hard-error");
@@ -876,6 +924,7 @@ mod tests {
volume_id: [0x11u8; 16],
read_data_key: Some([0x22u8; 16]),
read_data_key_err: None,
drive_unlocked: false,
};
let st = Disc::resolve_vid_only(&udf, &mut disc, Some(&hs)).expect("bus key present → ok");
assert!(st.bus_encryption);
@@ -903,6 +952,7 @@ mod tests {
volume_id: [0x11u8; 16],
read_data_key: None,
read_data_key_err: None,
drive_unlocked: false,
};
let st = Disc::resolve_vid_only(&udf, &mut disc, Some(&hs)).expect("AACS 1.0 → ok");
assert!(!st.bus_encryption);