From e7926ae9f4e5fa258696551a39295402819280c9 Mon Sep 17 00:00:00 2001
From: dirkf <fieldhouse@gmx.net>
Date: Fri, 28 Jul 2023 06:03:14 +0100
Subject: [utils] Rework decoding of `Content-Encoding`s

* support nested encodings
* support optional `br` encoding, if brotli package is installed
* support optional 'compress' encoding, if ncompress package is installed
* response `Content-Encoding` has only unprocessed encodings, or removed
* response `Content-Length` is decoded length (usable for filesize metadata)
* use zlib for both deflate and gzip decompression
* some elements taken from yt-dlp: thx especially coletdjnz
---
 test/test_http.py    |  16 ++-----
 youtube_dl/compat.py |  14 ++++++
 youtube_dl/utils.py  | 120 ++++++++++++++++++++++++++++++++++++++-------------
 3 files changed, 107 insertions(+), 43 deletions(-)
diff --git a/test/test_http.py b/test/test_http.py
index 89580969d..793bea359 100644
--- a/test/test_http.py
+++ b/test/test_http.py
@@ -461,33 +461,23 @@ class TestHTTP(unittest.TestCase):
                 sanitized_Request(
                     self._test_url('content-encoding'),
                     headers={'ytdl-encoding': encoding}))
-            self.assertEqual(res.headers.get('Content-Encoding'), encoding)
+            # decoded encodings are removed: only check for valid decompressed data
             self.assertEqual(res.read(), b'<html><video src="/vid.mp4" /></html>')
 
     @unittest.skipUnless(brotli, 'brotli support is not installed')
-    @unittest.expectedFailure
     def test_brotli(self):
         self.__test_compression('br')
 
-    @unittest.expectedFailure
     def test_deflate(self):
         self.__test_compression('deflate')
 
-    @unittest.expectedFailure
     def test_gzip(self):
         self.__test_compression('gzip')
 
-    @unittest.expectedFailure  # not yet implemented
     def test_multiple_encodings(self):
         # https://www.rfc-editor.org/rfc/rfc9110.html#section-8.4
-        with FakeYDL() as ydl:
-            for pair in ('gzip,deflate', 'deflate, gzip', 'gzip, gzip', 'deflate, deflate'):
-                res = ydl.urlopen(
-                    sanitized_Request(
-                        self._test_url('content-encoding'),
-                        headers={'ytdl-encoding': pair}))
-                self.assertEqual(res.headers.get('Content-Encoding'), pair)
-                self.assertEqual(res.read(), b'<html><video src="/vid.mp4" /></html>')
+        for pair in ('gzip,deflate', 'deflate, gzip', 'gzip, gzip', 'deflate, deflate'):
+            self.__test_compression(pair)
 
     def test_unsupported_encoding(self):
         # it should return the raw content
diff --git a/youtube_dl/compat.py b/youtube_dl/compat.py
index da6d70ec4..54ad64674 100644
--- a/youtube_dl/compat.py
+++ b/youtube_dl/compat.py
@@ -3200,6 +3200,18 @@ except AttributeError:
     def compat_datetime_timedelta_total_seconds(td):
         return (td.microseconds + (td.seconds + td.days * 24 * 3600) * 10**6) / 10**6
 
+# optional decompression packages
+# PyPi brotli package implements 'br' Content-Encoding
+try:
+    import brotli as compat_brotli
+except ImportError:
+    compat_brotli = None
+# PyPi ncompress package implements 'compress' Content-Encoding
+try:
+    import ncompress as compat_ncompress
+except ImportError:
+    compat_ncompress = None
+
 
 legacy = [
     'compat_HTMLParseError',
@@ -3234,6 +3246,7 @@ __all__ = [
     'compat_Struct',
     'compat_base64_b64decode',
     'compat_basestring',
+    'compat_brotli',
     'compat_casefold',
     'compat_chr',
     'compat_collections_abc',
@@ -3259,6 +3272,7 @@ __all__ = [
     'compat_itertools_zip_longest',
     'compat_kwargs',
     'compat_map',
+    'compat_ncompress',
     'compat_numeric_types',
     'compat_open',
     'compat_ord',
diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index b5475434f..e73291107 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -15,7 +15,6 @@ import email.utils
 import email.header
 import errno
 import functools
-import gzip
 import inspect
 import io
 import itertools
@@ -42,6 +41,7 @@ from .compat import (
     compat_HTMLParseError,
     compat_HTMLParser,
     compat_basestring,
+    compat_brotli as brotli,
     compat_casefold,
     compat_chr,
     compat_collections_abc,
@@ -55,6 +55,7 @@ from .compat import (
     compat_http_client,
     compat_integer_types,
     compat_kwargs,
+    compat_ncompress as ncompress,
     compat_os_name,
     compat_re_Match,
     compat_re_Pattern,
@@ -2638,11 +2639,44 @@ class YoutubeDLHandler(compat_urllib_request.HTTPHandler):
             req)
 
     @staticmethod
-    def deflate(data):
+    def deflate_gz(data):
         try:
-            return zlib.decompress(data, -zlib.MAX_WBITS)
+            # format:zlib,gzip + windowsize:32768
+            return data and zlib.decompress(data, 32 + zlib.MAX_WBITS)
         except zlib.error:
-            return zlib.decompress(data)
+            # raw zlib * windowsize:32768 (RFC 9110: "non-conformant")
+            return zlib.decompress(data, -zlib.MAX_WBITS)
+
+    @staticmethod
+    def gzip(data):
+
+        from gzip import GzipFile
+
+        def _gzip(data):
+            with io.BytesIO(data) as data_buf:
+                gz = GzipFile(fileobj=data_buf, mode='rb')
+                return gz.read()
+
+        try:
+            return _gzip(data)
+        except IOError as original_ioerror:
+            # There may be junk at the end of the file
+            # See http://stackoverflow.com/q/4928560/35070 for details
+            for i in range(1, 1024):
+                try:
+                    return _gzip(data[:-i])
+                except IOError:
+                    continue
+            else:
+                raise original_ioerror
+
+    @staticmethod
+    def brotli(data):
+        return data and brotli.decompress(data)
+
+    @staticmethod
+    def compress(data):
+        return data and ncompress.decompress(data)
 
     def http_request(self, req):
         # According to RFC 3986, URLs can not contain non-ASCII characters, however this is not
@@ -2679,33 +2713,59 @@ class YoutubeDLHandler(compat_urllib_request.HTTPHandler):
 
     def http_response(self, req, resp):
         old_resp = resp
-        # gzip
-        if resp.headers.get('Content-encoding', '') == 'gzip':
-            content = resp.read()
-            gz = gzip.GzipFile(fileobj=io.BytesIO(content), mode='rb')
-            try:
-                uncompressed = io.BytesIO(gz.read())
-            except IOError as original_ioerror:
-                # There may be junk at the end of the file
-                # See http://stackoverflow.com/q/4928560/35070 for details
-                for i in range(1, 1024):
-                    try:
-                        gz = gzip.GzipFile(fileobj=io.BytesIO(content[:-i]), mode='rb')
-                        uncompressed = io.BytesIO(gz.read())
-                    except IOError:
-                        continue
-                    break
-                else:
-                    raise original_ioerror
-            resp = compat_urllib_request.addinfourl(uncompressed, old_resp.headers, old_resp.url, old_resp.code)
-            resp.msg = old_resp.msg
-            del resp.headers['Content-encoding']
-        # deflate
-        if resp.headers.get('Content-encoding', '') == 'deflate':
-            gz = io.BytesIO(self.deflate(resp.read()))
-            resp = compat_urllib_request.addinfourl(gz, old_resp.headers, old_resp.url, old_resp.code)
+
+        # Content-Encoding header lists the encodings in order that they were applied [1].
+        # To decompress, we simply do the reverse.
+        # [1]: https://datatracker.ietf.org/doc/html/rfc9110#name-content-encoding
+        decoded_response = None
+        decoders = {
+            'gzip': self.deflate_gz,
+            'deflate': self.deflate_gz,
+        }
+        if brotli:
+            decoders['br'] = self.brotli
+        if ncompress:
+            decoders['compress'] = self.compress
+        if sys.platform.startswith('java'):
+            # Jython zlib implementation misses gzip
+            decoders['gzip'] = self.gzip
+
+        def encodings(hdrs):
+            # A header field that allows multiple values can have multiple instances [2].
+            # [2]: https://datatracker.ietf.org/doc/html/rfc9110#name-fields
+            for e in reversed(','.join(hdrs).split(',')):
+                if e:
+                    yield e.strip()
+
+        encodings_left = []
+        try:
+            resp.headers.get_all
+            hdrs = resp.headers
+        except AttributeError:
+            # Py2 has no get_all() method: headers are rfc822.Message
+            from email.message import Message
+            hdrs = Message()
+            for k, v in resp.headers.items():
+                hdrs[k] = v
+
+        decoder, decoded_response = True, None
+        for encoding in encodings(hdrs.get_all('Content-Encoding', [])):
+            # "SHOULD consider" x-compress, x-gzip as compress, gzip
+            decoder = decoder and decoders.get(remove_start(encoding, 'x-'))
+            if not decoder:
+                encodings_left.insert(0, encoding)
+                continue
+            decoded_response = decoder(decoded_response or resp.read())
+        if decoded_response is not None:
+            resp = compat_urllib_request.addinfourl(
+                io.BytesIO(decoded_response), old_resp.headers, old_resp.url, old_resp.code)
             resp.msg = old_resp.msg
-            del resp.headers['Content-encoding']
+            del resp.headers['Content-Length']
+            resp.headers['Content-Length'] = '%d' % len(decoded_response)
+        del resp.headers['Content-Encoding']
+        if encodings_left:
+            resp.headers['Content-Encoding'] = ', '.join(encodings_left)
+
         # Percent-encode redirect URL of Location HTTP header to satisfy RFC 3986 (see
         # https://github.com/ytdl-org/youtube-dl/issues/6457).
         if 300 <= resp.code < 400:
-- 
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