Matthew Jackson
d4a0f5b786
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).
95 lines
4.1 KiB
Rust
95 lines
4.1 KiB
Rust
//! AACS decryption — Volume Unique Key lookup and title key derivation.
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//!
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//! Two paths:
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//! 1. VUK lookup: disc_hash → KEYDB.cfg → VUK (fast, 99% of discs)
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//! 2. Full handshake: device_keys + MKB → Media Key → + Volume ID → VUK (fallback)
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//!
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//! KEYDB.cfg format:
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//! | DK | DEVICE_KEY 0x... | DEVICE_NODE 0x... | KEY_UV 0x... | KEY_U_MASK_SHIFT 0x...
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//! | PK | 0x...
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//! | HC | HOST_PRIV_KEY 0x... | HOST_CERT 0x...
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//! | HC2 | HOST_PRIV_KEY 0x... | HOST_CERT 0x...
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//! 0x<disc_hash> = <title> | D | <date> | M | 0x<media_key> | I | 0x<disc_id> | V | 0x<vuk> | U | <unit_keys>
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//!
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//! The VUK decrypts title keys from AACS/Unit_Key_RO.inf on disc.
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//! Title keys decrypt m2ts stream content (AES-128-CBC).
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pub mod decrypt;
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pub mod handshake;
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pub mod keydb;
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pub mod keys;
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pub mod provider;
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pub mod variants;
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// Explicit re-exports — only items needed by external consumers and sibling crate modules.
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// AES primitives (aes_ecb_encrypt, aes_ecb_decrypt, aes_cbc_decrypt) are pub(crate) in decrypt.rs.
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pub use decrypt::{
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ALIGNED_UNIT_LEN, ALIGNED_UNIT_SECTORS, UnitKeyResult, decrypt_bus, decrypt_unit,
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decrypt_unit_full, decrypt_unit_try_keys, is_aacs_scrambled, is_unit_aligned, ts_packet_total,
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ts_sync_count, unit_key_validates,
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};
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pub use keydb::{DeviceKey, DiscEntry, HostCert, KeyDb};
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pub use keys::probe;
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pub use keys::{
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AacsVersion, ContentCert, MKB_20_CATEGORY_C, MKB_21_CATEGORY_C, MKB_TYPE_3_RECORDABLE,
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MKB_TYPE_4_PRERECORDED, MKB_TYPE_10_CLASS_II, MkbType, ResolveContext, ResolveFailure,
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ResolvedKeys, UnitKeyFile, decrypt_unit_key, derive_media_key_and_pk_from_dk,
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derive_media_key_from_dk, derive_media_key_from_pk, derive_vuk, disc_hash, disc_hash_hex,
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mkb_content_len, mkb_is_uhd, mkb_type, mkb_type_raw, mkb_version, parse_content_cert,
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parse_unit_key_ro, read_mkb_from_drive, recover_dk_position, resolve_keys_v1, resolve_keys_v2,
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resolve_keys_v21, resolve_keys_with_reason, trim_mkb,
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};
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pub use provider::KeyProvider;
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pub use variants::{
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KEY_CORRECTION_DATA_PLACEHOLDER, MediaKeyVariantError, MkbRecord, ProcessingKeyMatch,
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derive_media_key_variant, is_variant_mkb, variant_nonce, walk_mkb, walk_processing_key,
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};
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#[cfg(test)]
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mod tests {
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//! Re-export surface guards. The module's public API is the set of
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//! `pub use` items above. A regression that drops or renames an export
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//! (the class of bug that shipped in 0.31.0 by silently changing a
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//! surface) breaks compilation of these references, so they act as a
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//! compile-time contract for the crate's AACS surface.
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use super::*;
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#[test]
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fn aligned_unit_len_is_three_2048_byte_sectors() {
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// ALIGNED_UNIT_LEN is the AACS aligned-unit size: 3 × 2048 = 6144.
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// Re-exported from decrypt; pin the value here so the public constant
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// and the spec stay in lockstep.
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assert_eq!(ALIGNED_UNIT_LEN, 6144);
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assert_eq!(ALIGNED_UNIT_LEN, 3 * 2048);
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}
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#[test]
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fn version_strides_are_reexported_and_distinct() {
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// The three AACS generations are part of the public surface, and the
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// V10 (48) vs V20/V21 (64) stride distinction is the load-bearing
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// difference. Confirm the enum re-export is usable and the variants
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// are distinct values.
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assert_ne!(AacsVersion::V10, AacsVersion::V20);
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assert_ne!(AacsVersion::V20, AacsVersion::V21);
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}
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#[test]
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fn key_correction_data_placeholder_is_all_zero() {
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// The variant chain refuses to run against this all-zero placeholder
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// KCD; the public constant must therefore be exactly 16 zero bytes.
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assert_eq!(KEY_CORRECTION_DATA_PLACEHOLDER, [0u8; 16]);
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}
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#[test]
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fn public_helpers_are_callable_through_the_facade() {
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// Touch a representative function from each re-export group so a
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// dropped/renamed export fails to compile. These are smoke calls, not
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// behavioural assertions (behaviour is covered in each module).
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let _ = is_aacs_scrambled(&[0u8; ALIGNED_UNIT_LEN]);
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let _ = mkb_content_len(&[]);
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let _ = is_variant_mkb(&walk_mkb(&[]));
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let _ = disc_hash_hex(&disc_hash(b"x"));
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}
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}
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