mirror of
https://github.com/freemkv/libfreemkv.git
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Matthew Jackson
6e14fc0c0c
Security - Remove the unsafe Vec::set_len over recycled sector buffers — UB reachable from safe code (GHSA-j8ww-f5fg-9pmh, low). Uses Vec::resize; pooling unchanged. CI / tooling - clippy on stable with the MSRV single-sourced from Cargo.toml; cargo-deny dependency-audit gate with first-party git sources allowed (#15); audience-based comment-guard (#17). Docs - README (keydb ownership, BD-J parser count), drive-access transport/reset notes, mux timeline module-doc links.
101 lines
4.7 KiB
Markdown
101 lines
4.7 KiB
Markdown
# `aacs::inf` — notes
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## `UnitKeyFile`'s hand-written `Debug`
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Redacting `Debug`, per the policy `aacs::types` documents: this struct holds
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the disc's ENCRYPTED CPS unit keys — exactly the material a keydb entry stores
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— plus the disc hash they are looked up by. A derived `Debug` printed every key
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byte verbatim, so any `{:?}` (a downstream crate, an `assert_eq!` failure
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message, a future `tracing::debug!` in this module) leaked them. Only
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non-secret shape is printed. Guarded by `unit_key_file_debug_is_redacted`.
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The disc hash is the public keydb lookup key, printed as hex the same way
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`DiscEntry` prints its own — never as raw bytes.
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## `parse_vtkf`
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Layout — AACS "HD DVD and DVD Pre-recorded Book" Table 3-8, a fixed
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2480-byte file, verified byte-exact against real discs (Freedom `VTKF090`,
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Dukes of Hazzard `VTKF000`):
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```text
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[0x00..0x0C] magic "DVD_HD_V_TKF"
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[0x0C..0x10] BE32 HD_VTKF_SIZE (2480)
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[0x10..0x1C] associated playlist name ("VPLST%%%.XPL")
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[0x1C..0x80] reserved
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[0x80..] 64 entries × 36 bytes:
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BIFO (1) | reserved (3) | ENCRYPTED title key (16) | binding MAC (16)
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BIFO bit 7 (AV_FLG) set = this slot holds a title key
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(pre-recorded discs fill the binding MAC with 0xFF)
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[0x9A0..2480] 16-byte TKF MAC (CMAC keyed by Kvu — NOT a key)
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```
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The slot index (1-based) is the CPS unit number, so an absent slot is
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SKIPPED (not a terminator) — collapsing gaps would renumber later keys and
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hand the wrong title key to CPS unit N+1. The title→CPS mapping is
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playlist-driven (`VPLST%%%.XPL`) and owned by the HD DVD enumerator, so
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`title_cps_unit` is left empty here.
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The prior parser used a 32-byte stride (a 12-byte pad instead of the 16-byte
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binding MAC). That reads entry #1 correctly but drifts +4 bytes per entry
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after it, so it only decrypted single-CPS-unit discs; every multi-key VTKF
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(real multi-CPS-unit HD-DVD titles) yielded garbage keys for CPS unit ≥2.
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## `synth_vtkf` test helper
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Build a synthetic `VTKF%%%.AACS` matching the real on-disc layout (AACS
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HD DVD Book Table 3-8, verified against Freedom `VTKF090` and Dukes
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`VTKF000`): magic, BE32 size, playlist name, reserved to 0x80, then 64
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entry slots of 36 bytes (the first `keys.len()` present with `AV_FLG`
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set, the rest empty), a reserved gap, and the 16-byte trailing TKF MAC.
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## `unit_key_file_debug_is_redacted` test
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`UnitKeyFile` holds the disc's ENCRYPTED CPS unit keys. A derived `Debug`
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printed every byte; the hand-written impl must not. Sentinel key byte
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0xD5 = decimal 213 (a derived `Debug` renders `[u8; 16]` in decimal), the
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same probe `aacs::types::redaction_tests` uses. Mutation guard: putting
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`#[derive(Debug)]` back fails this.
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## `read_mkb_from_drive_returns_the_concatenated_pack_payload` test
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`read_mkb_from_drive` is the in-drive MKB source: every AACS derivation
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downstream (`mkb_find_mk_dv`, the subset-difference walk, the whole
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Media Key ladder) consumes exactly what it returns. An empty return is
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not a benign "no MKB" — it is a total read failure reported as success,
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and every derivation then fails with a key-not-found code that points
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the operator at their keydb rather than at the drive.
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This pins the CONTENT: the concatenated payload of all packs, in pack
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order, byte for byte.
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## `read_mkb_from_drive_issues_the_exact_mmc_cdb_for_each_pack` test
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The CDB is what the drive actually acts on, and every byte of it is
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load-bearing: a wrong format code returns a different disc structure
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entirely, and a wrong allocation length truncates the pack. The existing
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test above pins the opcode, the format code and the pack number; this
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pins the WHOLE 12-byte CDB, so no field can drift unnoticed.
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Expected layout (MMC-6 READ DISC STRUCTURE, AACS MKB format):
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`[0]` opcode, `[1]` media type 0x01, `[2..6]` address = pack number
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(BE32), `[6]` layer 0, `[7]` format 0x83, `[8..10]` allocation length
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BE16 = 32772 = `0x80 0x04`, `[10..12]` reserved/control.
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## `read_mkb_from_drive_accepts_a_full_size_pack` test
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A pack payload filling the FULL 32768-byte window must come back whole.
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The `len > 0 && len <= 32768` bound is what stands between a maximal
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pack and a silently dropped one, and the small payloads used elsewhere
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in this module never reach it.
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## `read_mkb_from_drive_ignores_a_pack_declaring_more_than_the_buffer_holds` test
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A drive that DECLARES more payload than it returned must not be
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believed. The BE16 length in the response header is drive-supplied data:
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a firmware bug, a short transfer, or a hostile device can put a value in
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it that runs past the 32772-byte buffer. Copying `len` bytes on that word
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alone panics the rip thread mid-scan.
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Both the first-pack read and the per-pack loop carry the same bound, so
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both are exercised here: the over-declared pack contributes nothing and
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the honest pack still comes through.
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