[ie/generic] Add `key_query` extractor-arg

Authored by: bashonly

README.md

@@ -1779,8 +1779,9 @@ The following extractors use this feature:
 * `approximate_date`: Extract approximate `upload_date` and `timestamp` in flat-playlist. This may cause date-based filters to be slightly off
 
 #### generic
-* `fragment_query`: Passthrough any query in mpd/m3u8 manifest URLs to their fragments if no value is provided, or else apply the query string given as `fragment_query=VALUE`. Does not apply to ffmpeg
+* `fragment_query`: Passthrough any query in mpd/m3u8 manifest URLs to their fragments if no value is provided, or else apply the query string given as `fragment_query=VALUE`. Note that if the stream has an HLS AES-128 key, then the query parameters will be passed to the key URI as well, unless the `key_query` extractor-arg is passed, or unless an external key URI is provided via the `hls_key` extractor-arg. Does not apply to ffmpeg
 * `variant_query`: Passthrough the master m3u8 URL query to its variant playlist URLs if no value is provided, or else apply the query string given as `variant_query=VALUE`
+* `key_query`: Passthrough the master m3u8 URL query to its HLS AES-128 decryption key URI if no value is provided, or else apply the query string given as `key_query=VALUE`. Note that this will have no effect if the key URI is provided via the `hls_key` extractor-arg. Does not apply to ffmpeg
 * `hls_key`: An HLS AES-128 key URI *or* key (as hex), and optionally the IV (as hex), in the form of `(URI|KEY)[,IV]`; e.g. `generic:hls_key=ABCDEF1234567980,0xFEDCBA0987654321`. Passing any of these values will force usage of the native HLS downloader and override the corresponding values found in the m3u8 playlist
 * `is_live`: Bypass live HLS detection and manually set `live_status` - a value of `false` will set `not_live`, any other value (or no value) will set `is_live`
 

yt_dlp/extractor/generic.py

@@ -2167,7 +2167,15 @@ class GenericIE(InfoExtractor):
                 urllib.parse.urlparse(fragment_query).query or fragment_query
                 or urllib.parse.urlparse(manifest_url).query or None)
 
-        hex_or_none = lambda x: x if re.fullmatch(r'(0x)?[\da-f]+', x, re.IGNORECASE) else None
+        key_query = self._configuration_arg('key_query', [None], casesense=True)[0]
+        if key_query is not None:
+            info['extra_param_to_key_url'] = (
+                urllib.parse.urlparse(key_query).query or key_query
+                or urllib.parse.urlparse(manifest_url).query or None)
+
+        def hex_or_none(value):
+            return value if re.fullmatch(r'(0x)?[\da-f]+', value, re.IGNORECASE) else None
+
         info['hls_aes'] = traverse_obj(self._configuration_arg('hls_key', casesense=True), {
             'uri': (0, {url_or_none}), 'key': (0, {hex_or_none}), 'iv': (1, {hex_or_none}),
         }) or None