craft-media: DeckCraft's two Ogg fixes (#810)

Packet byte ranges are checked against the source before a buffer is
sized for them (deckcraft 51d19baa), and packets after the last known
granule count towards the Opus duration (deckcraft 9d36b593). Each test
failed before its fix.

crates/media/src/ogg/mod.rs

@@ -708,6 +708,11 @@ fn find_capture(src: &(impl ByteSource + ?Sized), from: u64, len: u64, recovery:
 
 /// The first `max` bytes of a packet's parts.
 fn read_parts(src: &(impl ByteSource + ?Sized), parts: &[(u64, u32)], max: usize) -> Result<Vec<u8>> {
+    // Ranges come from a scan of some source; check them against this one before sizing a buffer.
+    let len = src.len();
+    if parts.iter().any(|&(o, n)| o.checked_add(u64::from(n)).is_none_or(|end| end > len)) {
+        return Err(Error::Invalid("packet range lies outside the source".into()));
+    }
     let mut v = Vec::with_capacity(parts.iter().map(|p| p.1 as usize).sum::<usize>().min(max));
     for &(o, n) in parts {
         let a = v.len();
@@ -797,6 +802,8 @@ impl OpusTiming {
                     c = c.saturating_add(i64::from(durations[k]));
                     ends[k] = Some(c);
                 }
+                // the total counts these packets too
+                cursor = Some(c);
                 break;
             }
             let Some(g) = stream.packets[j].granule else { break };

crates/media/src/ogg/tests.rs

@@ -696,3 +696,34 @@ fn crc_update_continues_across_any_split() {
         assert_eq!(crc32_update(crc32_bitwise(0, a), b), whole, "cut {cut} (reference head)");
     }
 }
+
+#[test]
+fn read_packet_checks_its_ranges_against_the_source_before_allocating() {
+    let f = opus_file(10, 312, 500);
+    let o = open(&f[..]).unwrap();
+    let s = o.stream_of(Codec::Opus).unwrap();
+    // The last packet lies past the end of a source cut short: an error, not a read of missing bytes.
+    let short = &f[..f.len() / 2];
+    assert!(matches!(o.read_packet(short, s, 9), Err(Error::Invalid(_))));
+}
+
+#[test]
+fn opus_timing_includes_packets_after_the_last_known_granule() {
+    let f = opus_file(6, 312, 0);
+    let o = open(&f[..]).unwrap();
+    let mut stream = o.streams[0].clone();
+    // Missing granules on complete-packet pages are non-conforming. The recovery fallback still
+    // assigns their packet positions; the total must include the same samples.
+    stream.packets.last_mut().unwrap().granule = None;
+    let timing = OpusTiming::of(&stream, 312);
+    assert_eq!(timing.starts, vec![-312, 648, 1608, 2568, 3528, 4488]);
+    assert_eq!(timing.total, 6 * 960 - 312);
+
+    // With no usable granule, every complete packet still contributes its TOC duration.
+    for packet in &mut stream.packets {
+        packet.granule = None;
+    }
+    let timing = OpusTiming::of(&stream, 312);
+    assert_eq!(timing.starts, vec![-312, 648, 1608, 2568, 3528, 4488]);
+    assert_eq!(timing.total, 6 * 960 - 312);
+}