internal/adapters/audio/ffmpeg_test.go

@@ -58,3 +58,22 @@ func TestFFmpegToWAV_MissingBinaryIsAnError(t *testing.T) {
 	require.Error(t, err)
 	assert.False(t, errors.Is(err, context.Canceled))
 }
+
+func TestFFmpegToWAV_RestrictsWhatTheFileMayMakeFFmpegOpen(t *testing.T) {
+	rec := filepath.Join(t.TempDir(), "argv")
+	bin := stub(t, `printf '%s\n' "$@" > `+rec+`
+for a; do last="$a"; done
+printf data > "$last"`)
+
+	err := (&audio.FFmpeg{Bin: bin}).ToWAV(context.Background(), "/spool/in", filepath.Join(t.TempDir(), "o.wav"))
+
+	require.NoError(t, err)
+	args := argvOf(t, rec)
+	pw, fw, in := indexOf(args, "-protocol_whitelist"), indexOf(args, "-format_whitelist"), indexOf(args, "-i")
+	require.GreaterOrEqual(t, pw, 0, "argv: %v", args)
+	require.GreaterOrEqual(t, fw, 0, "argv: %v", args)
+	assert.Equal(t, "file,pipe", args[pw+1])
+	assert.Equal(t, audio.AllowedDemuxers, args[fw+1])
+	assert.Less(t, pw, in, "input options must come BEFORE -i or ffmpeg applies them to the output")
+	assert.Less(t, fw, in)
+}

internal/adapters/audio/ffprobe_test.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 
@@ -127,3 +128,59 @@ func TestFFprobeProbe_StopsWhenTheContextIsCancelled(t *testing.T) {
 	assert.Less(t, time.Since(start), 5*time.Second)
 	assert.False(t, errors.Is(err, uploads.ErrUnreadable), "a timeout is not a verdict on the file")
 }
+
+// argvStub records the arguments it was called with into a file and then behaves as
+// a successful ffprobe, so a test can assert exactly what the process was asked.
+func argvStub(t *testing.T) (bin, argvFile string) {
+	t.Helper()
+	argvFile = filepath.Join(t.TempDir(), "argv")
+	bin = stub(t, `printf '%s\n' "$@" > `+argvFile+`
+echo '{"streams":[{"codec_type":"audio"}],"format":{"duration":"1"}}'`)
+	return bin, argvFile
+}
+
+func argvOf(t *testing.T, file string) []string {
+	t.Helper()
+	raw, err := os.ReadFile(file)
+	require.NoError(t, err)
+	return strings.Split(strings.TrimSpace(string(raw)), "\n")
+}
+
+func indexOf(args []string, want string) int {
+	for i, a := range args {
+		if a == want {
+			return i
+		}
+	}
+	return -1
+}
+
+func TestFFprobeProbe_RestrictsWhatTheFileMayMakeFFmpegOpen(t *testing.T) {
+	// The input is attacker-supplied. ffmpeg can be told by a file's CONTENT to open
+	// other files or URLs (HLS and concat playlists); recent versions refuse by
+	// default, but that is version luck. Pin it: local files and pipes only, and
+	// only the demuxers real audio recordings use.
+	bin, argvFile := argvStub(t)
+
+	_, err := (&audio.FFprobe{Bin: bin}).Probe(context.Background(), "/spool/upload-1")
+
+	require.NoError(t, err)
+	args := argvOf(t, argvFile)
+	pw := indexOf(args, "-protocol_whitelist")
+	require.GreaterOrEqual(t, pw, 0, "argv: %v", args)
+	assert.Equal(t, "file,pipe", args[pw+1])
+	fw := indexOf(args, "-format_whitelist")
+	require.GreaterOrEqual(t, fw, 0, "argv: %v", args)
+	assert.Equal(t, audio.AllowedDemuxers, args[fw+1])
+	assert.Equal(t, "/spool/upload-1", args[len(args)-1], "the path stays the last argument")
+}
+
+func TestAllowedDemuxers_ExcludeThePlaylistFormats(t *testing.T) {
+	for _, bad := range []string{"concat", "hls", "applehttp", "dash", "rtsp", "sdp", "image2"} {
+		assert.NotContains(t, strings.Split(audio.AllowedDemuxers, ","), bad,
+			"%s can make ffmpeg open other files or URLs named inside the upload", bad)
+	}
+	for _, good := range []string{"wav", "mov", "mp4", "m4a", "mp3", "ogg", "matroska", "flac"} {
+		assert.Contains(t, strings.Split(audio.AllowedDemuxers, ","), good)
+	}
+}