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[core] Disallow unsafe extensions (CVE-2024-38519)

Browse Source 
Ref: https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-79w7-vh3h-8g4j

Authored by: Grub4K
This commit is contained in:
Simon Sawicki 2024-07-02 00:52:50 +02:00
parent 6aaf96a3d6
commit 5ce582448e
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7 changed files with 179 additions and 12 deletions
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8
README.md
View File

@ -2229,6 +2229,14 @@ ### Differences in default behavior
* `--compat-options 2022`: Same as `--compat-options 2023,playlist-match-filter,no-external-downloader-progress,prefer-legacy-http-handler,manifest-filesize-approx`
* `--compat-options 2023`: Currently does nothing. Use this to enable all future compat options
The following compat options restore vulnerable behavior from before security patches:
* `--compat-options allow-unsafe-ext`: Allow files with any extension (including unsafe ones) to be downloaded ([GHSA-79w7-vh3h-8g4j](<https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-79w7-vh3h-8g4j>))
> :warning: Only use if a valid file download is rejected because its extension is detected as uncommon
>
> **This option can enable remote code execution! Consider [opening an issue](<https://github.com/yt-dlp/yt-dlp/issues/new/choose>) instead!**
### Deprecated options
These are all the deprecated options and the current alternative to achieve the same effect

5
devscripts/changelog_override.json
View File

@ -175,5 +175,10 @@
"when": "e6a22834df1776ec4e486526f6df2bf53cb7e06f",
"short": "[ie/orf:on] Add `prefer_segments_playlist` extractor-arg (#10314)",
"authors": ["seproDev"]
},
{
"action": "add",
"when": "6aaf96a3d6e7d0d426e97e11a2fcf52fda00e733",
"short": "[priority] Security: [[CVE-2024-10123](https://nvd.nist.gov/vuln/detail/CVE-2024-10123)] [Properly sanitize file-extension to prevent file system modification and RCE](https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-79w7-vh3h-8g4j)\n - Unsafe extensions are now blocked from being downloaded"
}
]

31
test/test_utils.py
View File

@ -130,6 +130,7 @@
xpath_text,
xpath_with_ns,
)
from yt_dlp.utils._utils import _UnsafeExtensionError
from yt_dlp.utils.networking import (
HTTPHeaderDict,
escape_rfc3986,
@ -281,6 +282,13 @@ def env(var):
finally:
os.environ['HOME'] = old_home or ''
_uncommon_extensions = [
('exe', 'abc.exe.ext'),
('de', 'abc.de.ext'),
('../.mp4', None),
('..\\.mp4', None),
]
def test_prepend_extension(self):
self.assertEqual(prepend_extension('abc.ext', 'temp'), 'abc.temp.ext')
self.assertEqual(prepend_extension('abc.ext', 'temp', 'ext'), 'abc.temp.ext')
@ -289,6 +297,19 @@ def test_prepend_extension(self):
self.assertEqual(prepend_extension('.abc', 'temp'), '.abc.temp')
self.assertEqual(prepend_extension('.abc.ext', 'temp'), '.abc.temp.ext')
# Test uncommon extensions
self.assertEqual(prepend_extension('abc.ext', 'bin'), 'abc.bin.ext')
for ext, result in self._uncommon_extensions:
with self.assertRaises(_UnsafeExtensionError):
prepend_extension('abc', ext)
if result:
self.assertEqual(prepend_extension('abc.ext', ext, 'ext'), result)
else:
with self.assertRaises(_UnsafeExtensionError):
prepend_extension('abc.ext', ext, 'ext')
with self.assertRaises(_UnsafeExtensionError):
prepend_extension('abc.unexpected_ext', ext, 'ext')
def test_replace_extension(self):
self.assertEqual(replace_extension('abc.ext', 'temp'), 'abc.temp')
self.assertEqual(replace_extension('abc.ext', 'temp', 'ext'), 'abc.temp')
@ -297,6 +318,16 @@ def test_replace_extension(self):
self.assertEqual(replace_extension('.abc', 'temp'), '.abc.temp')
self.assertEqual(replace_extension('.abc.ext', 'temp'), '.abc.temp')
# Test uncommon extensions
self.assertEqual(replace_extension('abc.ext', 'bin'), 'abc.unknown_video')
for ext, _ in self._uncommon_extensions:
with self.assertRaises(_UnsafeExtensionError):
replace_extension('abc', ext)
with self.assertRaises(_UnsafeExtensionError):
replace_extension('abc.ext', ext, 'ext')
with self.assertRaises(_UnsafeExtensionError):
replace_extension('abc.unexpected_ext', ext, 'ext')
def test_subtitles_filename(self):
self.assertEqual(subtitles_filename('abc.ext', 'en', 'vtt'), 'abc.en.vtt')
self.assertEqual(subtitles_filename('abc.ext', 'en', 'vtt', 'ext'), 'abc.en.vtt')

23
yt_dlp/YoutubeDL.py
View File

@ -159,7 +159,7 @@
write_json_file,
write_string,
)
from .utils._utils import _YDLLogger
from .utils._utils import _UnsafeExtensionError, _YDLLogger
from .utils.networking import (
HTTPHeaderDict,
clean_headers,
@ -172,6 +172,20 @@
import ctypes
def _catch_unsafe_extension_error(func):
@functools.wraps(func)
def wrapper(self, *args, **kwargs):
try:
return func(self, *args, **kwargs)
except _UnsafeExtensionError as error:
self.report_error(
f'The extracted extension ({error.extension!r}) is unusual '
'and will be skipped for safety reasons. '
f'If you believe this is an error{bug_reports_message(",")}')
return wrapper
class YoutubeDL:
"""YoutubeDL class.
@ -454,8 +468,9 @@ class YoutubeDL:
Set the value to 'native' to use the native downloader
compat_opts: Compatibility options. See "Differences in default behavior".
The following options do not work when used through the API:
filename, abort-on-error, multistreams, no-live-chat, format-sort
no-clean-infojson, no-playlist-metafiles, no-keep-subs, no-attach-info-json.
filename, abort-on-error, multistreams, no-live-chat,
format-sort, no-clean-infojson, no-playlist-metafiles,
no-keep-subs, no-attach-info-json, allow-unsafe-ext.
Refer __init__.py for their implementation
progress_template: Dictionary of templates for progress outputs.
Allowed keys are 'download', 'postprocess',
@ -1400,6 +1415,7 @@ def evaluate_outtmpl(self, outtmpl, info_dict, *args, **kwargs):
outtmpl, info_dict = self.prepare_outtmpl(outtmpl, info_dict, *args, **kwargs)
return self.escape_outtmpl(outtmpl) % info_dict
@_catch_unsafe_extension_error
def _prepare_filename(self, info_dict, *, outtmpl=None, tmpl_type=None):
assert None in (outtmpl, tmpl_type), 'outtmpl and tmpl_type are mutually exclusive'
if outtmpl is None:
@ -3192,6 +3208,7 @@ def existing_file(self, filepaths, *, default_overwrite=True):
os.remove(file)
return None
@_catch_unsafe_extension_error
def process_info(self, info_dict):
"""Process a single resolved IE result. (Modifies it in-place)"""

8
yt_dlp/__init__.py
View File

@ -64,6 +64,7 @@
write_string,
)
from .utils.networking import std_headers
from .utils._utils import _UnsafeExtensionError
from .YoutubeDL import YoutubeDL
_IN_CLI = False
@ -593,6 +594,13 @@ def report_deprecation(val, old, new=None):
if opts.ap_username is not None and opts.ap_password is None:
opts.ap_password = getpass.getpass('Type TV provider account password and press [Return]: ')
# compat option changes global state destructively; only allow from cli
if 'allow-unsafe-ext' in opts.compat_opts:
warnings.append(
'Using allow-unsafe-ext opens you up to potential attacks. '
'Use with great care!')
_UnsafeExtensionError.sanitize_extension = lambda x: x
return warnings, deprecation_warnings

2
yt_dlp/options.py
View File

@ -474,7 +474,7 @@ def _alias_callback(option, opt_str, value, parser, opts, nargs):
'no-attach-info-json', 'embed-thumbnail-atomicparsley', 'no-external-downloader-progress',
'embed-metadata', 'seperate-video-versions', 'no-clean-infojson', 'no-keep-subs', 'no-certifi',
'no-youtube-channel-redirect', 'no-youtube-unavailable-videos', 'no-youtube-prefer-utc-upload-date',
'prefer-legacy-http-handler', 'manifest-filesize-approx',
'prefer-legacy-http-handler', 'manifest-filesize-approx', 'allow-unsafe-ext',
}, 'aliases': {
'youtube-dl': ['all', '-multistreams', '-playlist-match-filter', '-manifest-filesize-approx'],
'youtube-dlc': ['all', '-no-youtube-channel-redirect', '-no-live-chat', '-playlist-match-filter', '-manifest-filesize-approx'],

114
yt_dlp/utils/_utils.py
View File

@ -2085,17 +2085,20 @@ def parse_duration(s):
(days, 86400), (hours, 3600), (mins, 60), (secs, 1), (ms, 1)))
def prepend_extension(filename, ext, expected_real_ext=None):
def _change_extension(prepend, filename, ext, expected_real_ext=None):
name, real_ext = os.path.splitext(filename)
return (
f'{name}.{ext}{real_ext}'
if not expected_real_ext or real_ext[1:] == expected_real_ext
else f'{filename}.{ext}')
if not expected_real_ext or real_ext[1:] == expected_real_ext:
filename = name
if prepend and real_ext:
_UnsafeExtensionError.sanitize_extension(ext, prepend=True)
return f'{filename}.{ext}{real_ext}'
return f'{filename}.{_UnsafeExtensionError.sanitize_extension(ext)}'
def replace_extension(filename, ext, expected_real_ext=None):
name, real_ext = os.path.splitext(filename)
return f'{name if not expected_real_ext or real_ext[1:] == expected_real_ext else filename}.{ext}'
prepend_extension = functools.partial(_change_extension, True)
replace_extension = functools.partial(_change_extension, False)
def check_executable(exe, args=[]):
@ -5035,6 +5038,101 @@ def items_(self):
KNOWN_EXTENSIONS = (*MEDIA_EXTENSIONS.video, *MEDIA_EXTENSIONS.audio, *MEDIA_EXTENSIONS.manifests)
class _UnsafeExtensionError(Exception):
"""
Mitigation exception for uncommon/malicious file extensions
This should be caught in YoutubeDL.py alongside a warning
Ref: https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-79w7-vh3h-8g4j
"""
ALLOWED_EXTENSIONS = frozenset([
# internal
'description',
'json',
'meta',
'orig',
'part',
'temp',
'uncut',
'unknown_video',
'ytdl',
# video
*MEDIA_EXTENSIONS.video,
'avif',
'ismv',
'm2ts',
'm4s',
'mng',
'mpeg',
'qt',
'swf',
'ts',
'vp9',
'wvm',
# audio
*MEDIA_EXTENSIONS.audio,
'isma',
'mid',
'mpga',
'ra',
# image
*MEDIA_EXTENSIONS.thumbnails,
'bmp',
'gif',
'heic',
'ico',
'jng',
'jpeg',
'jxl',
'svg',
'tif',
'wbmp',
# subtitle
*MEDIA_EXTENSIONS.subtitles,
'dfxp',
'fs',
'ismt',
'sami',
'scc',
'ssa',
'tt',
'ttml',
# others
*MEDIA_EXTENSIONS.manifests,
*MEDIA_EXTENSIONS.storyboards,
'desktop',
'ism',
'm3u',
'sbv',
'url',
'webloc',
'xml',
])
def __init__(self, extension, /):
super().__init__(f'unsafe file extension: {extension!r}')
self.extension = extension
@classmethod
def sanitize_extension(cls, extension, /, *, prepend=False):
if '/' in extension or '\\' in extension:
raise cls(extension)
if not prepend:
_, _, last = extension.rpartition('.')
if last == 'bin':
extension = last = 'unknown_video'
if last.lower() not in cls.ALLOWED_EXTENSIONS:
raise cls(extension)
return extension
class RetryManager:
"""Usage:
for retry in RetryManager(...):