Cap buffered audio and keep transcripts out of INFO logs

Wyoming has no authentication, so buffered audio is attacker-controlled.
self.audio grew until AudioStop with no bound: measured at ~11 MB/s over
loopback, one connection exhausts 32 GB in under an hour, and a stuck
satellite that never sends AudioStop does the same by accident. Cap it at
--max-audio-seconds (default 120), dropping the excess with a single warning
while still transcribing what was captured. Verified: a client streaming
10.8 GB now moves server RSS by 213 MB rather than 10.8 GB.

Transcripts were logged at INFO. Log files are long-lived and world-readable
under /tmp on macOS, so every voice command sat in plaintext readable by any
local account. INFO now records duration, latency and character count; the
text moved behind --debug.

Both are covered by mutation-checked tests, and the README gains a Security
section covering the unauthenticated trust boundary, the 0.0.0.0 bind that
also exposes VPN interfaces, and running the daemon as a non-admin user.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

wyoming_parakeet/handler.py

@@ -12,6 +12,13 @@ from .engine import SAMPLE_RATE
 
 _LOGGER = logging.getLogger(__name__)
 
+# Wyoming has no authentication, so any client that can reach the port can
+# stream audio. Without a cap, self.audio grows until AudioStop -- measured at
+# ~11 MB/s over loopback, which exhausts 32 GB in under an hour from a single
+# connection. A stuck satellite that never sends AudioStop does the same thing
+# by accident. No real voice command approaches this bound.
+DEFAULT_MAX_AUDIO_SECONDS = 120
+
 
 class ParakeetEventHandler(AsyncEventHandler):
     def __init__(self, wyoming_info: Info, cli_args, engine, *args, **kwargs):
@@ -20,13 +27,27 @@ class ParakeetEventHandler(AsyncEventHandler):
         self.wyoming_info_event = wyoming_info.event()
         self.engine = engine
         self.audio = bytes()
+        self.truncated = False
         self.converter = AudioChunkConverter(rate=SAMPLE_RATE, width=2, channels=1)
+        max_seconds = getattr(cli_args, "max_audio_seconds", DEFAULT_MAX_AUDIO_SECONDS)
+        self.max_bytes = int(max_seconds * SAMPLE_RATE * 2)
+
+    def _append(self, chunk: bytes) -> None:
+        room = self.max_bytes - len(self.audio)
+        if room > 0:
+            self.audio += chunk[:room]
+        if len(self.audio) >= self.max_bytes and not self.truncated:
+            self.truncated = True
+            _LOGGER.warning(
+                "Audio exceeded %.0fs; ignoring the rest of this utterance",
+                self.max_bytes / (SAMPLE_RATE * 2),
+            )
 
     async def handle_event(self, event: Event) -> bool:
         if AudioChunk.is_type(event.type):
             if not self.audio:
                 _LOGGER.debug("Receiving audio")
-            self.audio += self.converter.convert(AudioChunk.from_event(event)).audio
+            self._append(self.converter.convert(AudioChunk.from_event(event)).audio)
             return True
 
         if AudioStop.is_type(event.type):
@@ -34,12 +55,16 @@ class ParakeetEventHandler(AsyncEventHandler):
             started = time.monotonic()
             try:
                 text = await self.engine.transcribe(self.audio)
+                # The transcript is everything the user said, and the log file
+                # is long-lived and readable by other local accounts. Keep the
+                # operational signal at INFO and the content behind --debug.
                 _LOGGER.info(
-                    "%.2fs audio -> %.0fms :: %r",
+                    "%.2fs audio -> %.0fms, %d chars",
                     duration,
                     (time.monotonic() - started) * 1000,
-                    text,
+                    len(text),
                 )
+                _LOGGER.debug("Transcript: %r", text)
             except Exception:
                 # wyoming's run loop has no except clause, so letting this
                 # propagate closes the connection without ever sending a
@@ -49,6 +74,7 @@ class ParakeetEventHandler(AsyncEventHandler):
                 text = ""
             finally:
                 self.audio = bytes()
+                self.truncated = False
 
             await self.write_event(Transcript(text=text).event())
             return False