aacs: split no-key resolution reason into E7021 vs E7022
When key resolution had derivation material (device or processing keys) but no Volume ID was available to derive the unit key, surface Error::AacsVidUnavailable instead of the generic NoDiscKey. When there was no usable key material at all, keep NoDiscKey. resolve_keys_classical / resolve_keys_v21 still return a bare Option<ResolvedKeys> (all existing callers unchanged); a new resolve_keys_with_reason wrapper threads the typed ResolveFailure (VidUnavailable | NoMaterial) out. decrypt_with uses it; the ensure_decryptable_keys gate maps a captured AacsVidUnavailable reason to E7021, otherwise E7022. No decryption math, key derivation, or descramble logic changed -- only the reason reported on a resolution failure. Adds ensure_decryptable_aacs_vid_unavailable_vs_no_key proving both branches (device-keys + zero VID -> E7021; no keys -> E7022).
This commit is contained in:
Matthew Jackson
+108
-7
@@ -2048,6 +2048,15 @@ impl Disc {
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let needs_key = matches!(keys, crate::decrypt::DecryptKeys::None);
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if needs_key {
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if self.aacs.is_some() {
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// E7021 vs E7022 split: when key resolution had derivation
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// material (device / processing keys) but no Volume ID to derive
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// the unit key, the captured `aacs_error` is `AacsVidUnavailable`
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// — report THAT (the fix is recovering the VID, not adding keys),
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// not the generic `NoDiscKey`. Any other (or absent) reason →
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// `NoDiscKey` naming the disc by hash, unchanged.
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if matches!(self.aacs_error, Some(Error::AacsVidUnavailable)) {
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return Err(Error::AacsVidUnavailable);
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}
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return Err(Error::NoDiscKey {
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disc_hash: self.aacs_disc_hash(),
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});
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@@ -2267,13 +2276,12 @@ impl Disc {
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// Version dispatch — V10 uses the classical resolver at 48-byte
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// stride; V20/V21 share the 64-byte stride, so try the classical V20
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// paths first and fall back to the 2.1 variant chain.
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let resolved = match version_u8 {
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1 => crate::aacs::resolve_keys_v1(&ctx),
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_ => crate::aacs::resolve_keys_v2(&ctx)
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.or_else(|| crate::aacs::resolve_keys_v21(&ctx)),
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}
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.ok_or(crate::error::Error::AacsKeyRejected)?;
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// paths first and fall back to the 2.1 variant chain. The
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// reason-preserving wrapper threads the no-key cause out so the
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// decrypt gate can report E7021 (had derivation material but no VID)
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// vs E7022 (no usable material) instead of a flat AacsKeyRejected.
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let resolved = crate::aacs::resolve_keys_with_reason(&ctx, version_u8)
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.map_err(|_reason| crate::error::Error::AacsKeyRejected)?;
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if resolved.unit_keys.is_empty() {
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return Err(crate::error::Error::AacsKeyRejected);
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@@ -3995,6 +4003,99 @@ mod tests {
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);
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}
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/// E7021 vs E7022 split (rc.6 WS1). When key resolution HAD derivation
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/// material (device / processing keys) but no Volume ID was available to
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/// derive the unit key, the captured `aacs_error` is `AacsVidUnavailable`
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/// — the gate must surface THAT (E7021), not the generic `NoDiscKey`
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/// (E7022). When there was no usable key material at all, the reason is
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/// absent and the gate keeps `NoDiscKey` (E7022). Both branches proven here.
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#[test]
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fn ensure_decryptable_aacs_vid_unavailable_vs_no_key() {
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// Branch 1 — derivation material present, but no VID: E7021.
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// The resolver classifies a device-keys-but-zero-VID context as
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// `VidUnavailable`; that reason rides on `aacs_error`.
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let supplied = crate::aacs::provider::SuppliedKey {
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device_keys: vec![crate::aacs::DeviceKey {
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key: [0x11; 16],
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node: 1,
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uv: 1,
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u_mask_shift: 0,
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}],
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processing_keys: Vec::new(),
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media_keys: Vec::new(),
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disc_entry: None,
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};
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let provider_refs: [&dyn crate::aacs::KeyProvider; 1] = [&supplied];
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// A minimal but parseable Unit_Key_RO.inf (uk_pos=32, zero unit keys)
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// so resolution proceeds to the path-try logic and fails for lack of a
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// VID — not because the .inf failed to parse.
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let mut uk_ro = vec![0u8; 40];
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uk_ro[0..4].copy_from_slice(&32u32.to_be_bytes()); // uk_pos = 32
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// num_unit_keys = 0 (BE16) at uk_pos -> parses to an empty key file.
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let ctx = crate::aacs::ResolveContext {
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unit_key_ro: &uk_ro,
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content_cert: None,
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volume_id: &[0u8; 16], // the "no VID" sentinel
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providers: &provider_refs,
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mkb: None,
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};
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assert_eq!(
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crate::aacs::resolve_keys_with_reason(&ctx, 2).err(),
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Some(crate::aacs::ResolveFailure::VidUnavailable),
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"device keys + zero VID must classify as VidUnavailable"
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);
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let mut disc_e7021 = make_test_disc(1000, "UHD");
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disc_e7021.encrypted = true;
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disc_e7021.aacs = Some(aacs_with(Vec::new())); // present but no unit keys
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disc_e7021.aacs_error = Some(crate::error::Error::AacsVidUnavailable);
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let err = disc_e7021
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.ensure_decryptable(false)
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.expect_err("AACS disc, material-but-no-VID, !raw must error");
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assert_eq!(
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err.code(),
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crate::error::Error::AacsVidUnavailable.code(),
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"material-but-no-VID must surface E7021 (AacsVidUnavailable), not E7022"
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);
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// Branch 2 — no key material at all: classified NoMaterial, gate E7022.
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let supplied_none = crate::aacs::provider::SuppliedKey {
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device_keys: Vec::new(),
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processing_keys: Vec::new(),
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media_keys: Vec::new(),
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disc_entry: None,
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};
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let provider_refs_none: [&dyn crate::aacs::KeyProvider; 1] = [&supplied_none];
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let ctx_none = crate::aacs::ResolveContext {
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unit_key_ro: &uk_ro,
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content_cert: None,
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volume_id: &[0u8; 16],
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providers: &provider_refs_none,
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mkb: None,
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};
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assert_eq!(
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crate::aacs::resolve_keys_with_reason(&ctx_none, 2).err(),
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Some(crate::aacs::ResolveFailure::NoMaterial),
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"no key material must classify as NoMaterial"
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);
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let mut disc_e7022 = make_test_disc(1000, "UHD");
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disc_e7022.encrypted = true;
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disc_e7022.aacs = Some(aacs_with(Vec::new()));
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disc_e7022.aacs_error = None; // no reason captured → generic no-key
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let err = disc_e7022
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.ensure_decryptable(false)
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.expect_err("AACS disc, no material, !raw must error");
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assert_eq!(
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err.code(),
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crate::error::Error::NoDiscKey {
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disc_hash: String::new()
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}
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.code(),
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"no-material must keep E7022 (NoDiscKey)"
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);
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}
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/// Same AACS-no-key disc under `--raw` (raw=true) must PROCEED — the user
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/// asked for the encrypted image and needs no key.
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#[test]
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