From c3caa02fe5e48e02a2ff2c0f409317022b05d34f Mon Sep 17 00:00:00 2001 From: Petr Viktorin Date: Fri, 3 Jun 2022 11:43:35 +0200 Subject: [PATCH] 00382: CVE-2015-20107 Make mailcap refuse to match unsafe filenames/types/params (GH-91993) Upstream: https://github.com/python/cpython/issues/68966 Tracker bug: https://bugzilla.redhat.com/show_bug.cgi?id=2075390 --- lib-python/3/mailcap.py | 26 ++++++++++++++++++++++++-- lib-python/3/test/test_mailcap.py | 8 ++++++-- 2 files changed, 30 insertions(+), 4 deletions(-) diff --git a/lib-python/3/mailcap.py b/lib-python/3/mailcap.py index ae416a8..444c640 100644 --- a/lib-python/3/mailcap.py +++ b/lib-python/3/mailcap.py @@ -2,6 +2,7 @@ import os import warnings +import re __all__ = ["getcaps","findmatch"] @@ -13,6 +14,11 @@ def lineno_sort_key(entry): else: return 1, 0 +_find_unsafe = re.compile(r'[^\xa1-\U0010FFFF\w@+=:,./-]').search + +class UnsafeMailcapInput(Warning): + """Warning raised when refusing unsafe input""" + # Part 1: top-level interface. @@ -165,15 +171,22 @@ def findmatch(caps, MIMEtype, key='view', filename="/dev/null", plist=[]): entry to use. """ + if _find_unsafe(filename): + msg = "Refusing to use mailcap with filename %r. Use a safe temporary filename." % (filename,) + warnings.warn(msg, UnsafeMailcapInput) + return None, None entries = lookup(caps, MIMEtype, key) # XXX This code should somehow check for the needsterminal flag. for e in entries: if 'test' in e: test = subst(e['test'], filename, plist) + if test is None: + continue if test and os.system(test) != 0: continue command = subst(e[key], MIMEtype, filename, plist) - return command, e + if command is not None: + return command, e return None, None def lookup(caps, MIMEtype, key=None): @@ -206,6 +219,10 @@ def subst(field, MIMEtype, filename, plist=[]): elif c == 's': res = res + filename elif c == 't': + if _find_unsafe(MIMEtype): + msg = "Refusing to substitute MIME type %r into a shell command." % (MIMEtype,) + warnings.warn(msg, UnsafeMailcapInput) + return None res = res + MIMEtype elif c == '{': start = i @@ -213,7 +230,12 @@ def subst(field, MIMEtype, filename, plist=[]): i = i+1 name = field[start:i] i = i+1 - res = res + findparam(name, plist) + param = findparam(name, plist) + if _find_unsafe(param): + msg = "Refusing to substitute parameter %r (%s) into a shell command" % (param, name) + warnings.warn(msg, UnsafeMailcapInput) + return None + res = res + param # XXX To do: # %n == number of parts if type is multipart/* # %F == list of alternating type and filename for parts diff --git a/lib-python/3/test/test_mailcap.py b/lib-python/3/test/test_mailcap.py index c08423c..920283d 100644 --- a/lib-python/3/test/test_mailcap.py +++ b/lib-python/3/test/test_mailcap.py @@ -121,7 +121,8 @@ class HelperFunctionTest(unittest.TestCase): (["", "audio/*", "foo.txt"], ""), (["echo foo", "audio/*", "foo.txt"], "echo foo"), (["echo %s", "audio/*", "foo.txt"], "echo foo.txt"), - (["echo %t", "audio/*", "foo.txt"], "echo audio/*"), + (["echo %t", "audio/*", "foo.txt"], None), + (["echo %t", "audio/wav", "foo.txt"], "echo audio/wav"), (["echo \\%t", "audio/*", "foo.txt"], "echo %t"), (["echo foo", "audio/*", "foo.txt", plist], "echo foo"), (["echo %{total}", "audio/*", "foo.txt", plist], "echo 3") @@ -205,7 +206,10 @@ class FindmatchTest(unittest.TestCase): ('"An audio fragment"', audio_basic_entry)), ([c, "audio/*"], {"filename": fname}, - ("/usr/local/bin/showaudio audio/*", audio_entry)), + (None, None)), + ([c, "audio/wav"], + {"filename": fname}, + ("/usr/local/bin/showaudio audio/wav", audio_entry)), ([c, "message/external-body"], {"plist": plist}, ("showexternal /dev/null default john python.org /tmp foo bar", message_entry)) -- 2.35.3