chore(hardening): tighten security and footprint defaults

crates/audio/src/decode.rs

@@ -21,6 +21,13 @@ use kon_core::types::AudioSamples;
 /// input silently returned `Ok` with whatever had decoded before the
 /// failure — flagged by the 2026-04-22 review (RB-09).
 pub fn decode_audio_file(path: &Path) -> Result<AudioSamples> {
+    decode_audio_file_limited(path, None)
+}
+
+pub fn decode_audio_file_limited(
+    path: &Path,
+    max_duration_secs: Option<f64>,
+) -> Result<AudioSamples> {
     let file = File::open(path)
         .map_err(|e| KonError::AudioDecodeFailed(format!("Cannot open file: {e}")))?;
     let mss = MediaSourceStream::new(Box::new(file), Default::default());
@@ -30,13 +37,48 @@ pub fn decode_audio_file(path: &Path) -> Result<AudioSamples> {
         hint.with_extension(ext);
     }
 
-    decode_media_stream(mss, &hint)
+    decode_media_stream(mss, &hint, max_duration_secs)
+}
+
+pub fn probe_audio_duration_secs(path: &Path) -> Result<Option<f64>> {
+    let file = File::open(path)
+        .map_err(|e| KonError::AudioDecodeFailed(format!("Cannot open file: {e}")))?;
+    let mss = MediaSourceStream::new(Box::new(file), Default::default());
+    let mut hint = Hint::new();
+    if let Some(ext) = path.extension().and_then(|e| e.to_str()) {
+        hint.with_extension(ext);
+    }
+
+    let probed = symphonia::default::get_probe()
+        .format(
+            &hint,
+            mss,
+            &FormatOptions::default(),
+            &MetadataOptions::default(),
+        )
+        .map_err(|e| KonError::AudioDecodeFailed(format!("Unsupported format: {e}")))?;
+    let track = probed
+        .format
+        .default_track()
+        .ok_or_else(|| KonError::AudioDecodeFailed("No audio track found".into()))?;
+    let sample_rate = track
+        .codec_params
+        .sample_rate
+        .ok_or_else(|| KonError::AudioDecodeFailed("Unknown sample rate".into()))?;
+    Ok(track
+        .codec_params
+        .n_frames
+        .map(|frames| frames as f64 / sample_rate as f64))
 }
 
 /// Decode from an already-constructed `MediaSourceStream`. Split out so
 /// tests can inject a custom `MediaSource` (for example, one that
 /// returns a mid-stream I/O error) to verify error propagation.
-fn decode_media_stream(mss: MediaSourceStream, hint: &Hint) -> Result<AudioSamples> {
+fn decode_media_stream(
+    mss: MediaSourceStream,
+    hint: &Hint,
+    max_duration_secs: Option<f64>,
+) -> Result<AudioSamples> {
     let probed = symphonia::default::get_probe()
         .format(
             hint,
@@ -61,6 +103,7 @@ fn decode_media_stream(mss: MediaSourceStream, hint: &Hint) -> Result<AudioSampl
     }
 
     let track_id = track.id;
+    let max_samples = max_duration_secs.map(|secs| (secs * sample_rate as f64).ceil() as usize);
 
     let mut decoder = symphonia::default::get_codecs()
         .make(&track.codec_params, &DecoderOptions::default())
@@ -111,6 +154,15 @@ fn decode_media_stream(mss: MediaSourceStream, hint: &Hint) -> Result<AudioSampl
                 samples.push(sum / channels as f32);
             }
         }
+        if max_samples
+            .map(|limit| samples.len() > limit)
+            .unwrap_or(false)
+        {
+            return Err(KonError::AudioDecodeFailed(format!(
+                "Audio is longer than the {:.0} minute import limit",
+                max_duration_secs.unwrap_or(0.0) / 60.0
+            )));
+        }
     }
 
     if samples.is_empty() {
@@ -222,7 +274,7 @@ mod tests {
         let mut hint = Hint::new();
         hint.with_extension("wav");
 
-        let result = decode_media_stream(mss, &hint);
+        let result = decode_media_stream(mss, &hint, None);
         assert!(
             result.is_err(),
             "mid-stream I/O error must surface, got: {result:?}"