MP4 track timing was numerically unasserted. Every operator in the
PTS-to-ticks, duration, tkhd_dur and ctts chain could be flipped and the
whole suite stayed green, because no test decoded an output file and checked
a concrete number — the existing tests assert box presence and gross
container shape only. That is the crate's worst failure mode: a title muxes
"successfully" with silently wrong A/V sync or total duration, and nothing
above can tell.
The new tests build tracks with known PTS deltas and compare the emitted
stts, ctts and tkhd.duration against computed values.
Also lifted the faststart slack rule out of the match guard into
faststart_fits(). A leftover hole of 1-7 bytes cannot be expressed as any
ISO-BMFF box, since a box header is 8 bytes, so finish() must fall back to
moov-at-end rather than write a free box that lies about its own size. The
condition now has a name and a test instead of being an unexplained
`g == 0 || g >= 8` inside a pattern guard.
Five parsers that take bytes straight off a disc are now swept with
generated input asserting one property: they return Ok or Err and never
panic. That is this crate's own hard rule, and the class seven rounds of
reading is worst at.
Written in-crate rather than with cargo-fuzz, which needs a nightly
toolchain this project does not use, and without proptest or arbitrary,
because one dev-dependency is a deliberate posture and the parsers take
plain byte slices. What is given up is coverage-guided mutation, which is
the real loss. What is gained is determinism: the same seed replays the
same cases anywhere, so a CI failure reproduces locally verbatim.
Three generators, and the second is the one that matters. Pure random
bytes die at the magic check and exercise the entry guards only; prefixing
valid magic is what reaches the parser body; mutating a mostly-zero record
is what reaches the offset and count arithmetic a hostile image would lie
about.
That claim is MEASURED, not asserted. A harness whose cases all bounce off
the entry guards is the fuzzing equivalent of a test that cannot fail, so
one test counts how many generated cases parse to completion: 15,606 of
60,000, about 26%. If a future change to a guard drops that to zero, the
test fails rather than continuing to report a meaningless pass. Two further
tests pin that the three generators produce different bytes and that a seed
replays identically.
1.2M cases across all five targets found nothing. On this evidence that is
a real negative rather than an empty one.
The first version of this file was itself broken in the way this audit
keeps finding: its two meta-tests set FREEMKV_HARNESS_CASES and raced,
because the test harness runs them in parallel and env mutation is unsound
there. The budget is a parameter now, and the environment is read once at
the call site.
Two crate-internal parsers widened from private to pub(crate) so the
harness can reach them. No public API change.
Library-wide review-and-fix pass: tightened AACS keydb/handshake/variant
handling and trailing-partial-unit policy, corrected MPLS mark offset and
added UDF allocation bounds, hardened the mux/codec framing and M2TS paths,
guarded SCSI READ CAPACITY short transfers and unified error mapping, added
overflow guards on untrusted disc input, and made prefetch shutdown
deterministic. Release profile now builds with thin LTO + single codegen unit.
Features:
- Open drive identification via SPC-4 INQUIRY + MMC-6 GET CONFIGURATION
- 141 supported drives with bundled profiles
- MT1959 platform: unlock, calibrate, raw sector reads
- DriveSpeed enum: BD1x-BD12x, DVD1x-DVD16x
- Field names follow SPC-4 §6.4.2 and MMC-6 §5.3.10 standards
- No proprietary fingerprints — open matching by SCSI fields
- Zero config: profiles compiled into binary
Tested on real hardware: HL-DT-ST BD-RE BU40N 1.03
Matthew Jackson