From ce998c010a1524030687e180377e36a997b33162 Mon Sep 17 00:00:00 2001 From: Pascal Wittmann Date: Fri, 3 Jun 2022 13:11:44 +0200 Subject: [PATCH 1/2] gh-79096: Protect cookie file created by {LWP,Mozilla}CookieJar.save() Note: This change is not effective on Microsoft Windows. Cookies can store sensitive information and should therefore be protected against unauthorized third parties. This is also described in issue #79096. The filesystem permissions are currently set to 644, everyone can read the file. This commit changes the permissions to 600, only the creater of the file can read and modify it. This improves security, because it reduces the attack surface. Now the attacker needs control of the user that created the cookie or a ways to circumvent the filesystems permissions. This change is backwards incompatible. Systems that rely on world-readable cookies will breake. However, one could argue that those are misconfigured in the first place. --- Lib/http/cookiejar.py | 4 ++-- Lib/test/test_http_cookiejar.py | 31 +++++++++++++++++++++++++++++++ 2 files changed, 33 insertions(+), 2 deletions(-) diff --git a/Lib/http/cookiejar.py b/Lib/http/cookiejar.py index f19a366496a21a..c514e0d382cbc7 100644 --- a/Lib/http/cookiejar.py +++ b/Lib/http/cookiejar.py @@ -1890,7 +1890,7 @@ def save(self, filename=None, ignore_discard=False, ignore_expires=False): if self.filename is not None: filename = self.filename else: raise ValueError(MISSING_FILENAME_TEXT) - with open(filename, "w") as f: + with os.fdopen(os.open(filename, os.O_CREAT | os.O_WRONLY, 0o600), 'w') as f: # There really isn't an LWP Cookies 2.0 format, but this indicates # that there is extra information in here (domain_dot and # port_spec) while still being compatible with libwww-perl, I hope. @@ -2086,7 +2086,7 @@ def save(self, filename=None, ignore_discard=False, ignore_expires=False): if self.filename is not None: filename = self.filename else: raise ValueError(MISSING_FILENAME_TEXT) - with open(filename, "w") as f: + with os.fdopen(os.open(filename, os.O_CREAT | os.O_WRONLY, 0o600), 'w') as f: f.write(NETSCAPE_HEADER_TEXT) now = time.time() for cookie in self: diff --git a/Lib/test/test_http_cookiejar.py b/Lib/test/test_http_cookiejar.py index ad2b121fdaf5a1..3988bf864fb04b 100644 --- a/Lib/test/test_http_cookiejar.py +++ b/Lib/test/test_http_cookiejar.py @@ -1,6 +1,7 @@ """Tests for http/cookiejar.py.""" import os +import sys import re import test.support from test.support import os_helper @@ -17,6 +18,7 @@ reach, is_HDN, domain_match, user_domain_match, request_path, request_port, request_host) +mswindows = (sys.platform == "win32") class DateTimeTests(unittest.TestCase): @@ -368,6 +370,35 @@ def test_lwp_valueless_cookie(self): except OSError: pass self.assertEqual(c._cookies["www.acme.com"]["/"]["boo"].value, None) + @unittest.skipIf(mswindows, "windows file permissions are incompatible with file modes") + def test_lwp_filepermissions(self): + # Cookie file should only be readable by the creator + filename = os_helper.TESTFN + c = LWPCookieJar() + interact_netscape(c, "http://www.acme.com/", 'boo') + try: + c.save(filename, ignore_discard=True) + status = os.stat(filename) + print(status.st_mode) + self.assertEqual(oct(status.st_mode)[-3:], '600') + finally: + try: os.unlink(filename) + except OSError: pass + + @unittest.skipIf(mswindows, "windows file permissions are incompatible with file modes") + def test_mozilla_filepermissions(self): + # Cookie file should only be readable by the creator + filename = os_helper.TESTFN + c = MozillaCookieJar() + interact_netscape(c, "http://www.acme.com/", 'boo') + try: + c.save(filename, ignore_discard=True) + status = os.stat(filename) + self.assertEqual(oct(status.st_mode)[-3:], '600') + finally: + try: os.unlink(filename) + except OSError: pass + def test_bad_magic(self): # OSErrors (eg. file doesn't exist) are allowed to propagate filename = os_helper.TESTFN From d590fadd384ee7116c9ed37497db385dbd084ed4 Mon Sep 17 00:00:00 2001 From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com> Date: Fri, 3 Jun 2022 12:52:54 +0000 Subject: [PATCH 2/2] =?UTF-8?q?=F0=9F=93=9C=F0=9F=A4=96=20Added=20by=20blu?= =?UTF-8?q?rb=5Fit.?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- .../next/Security/2022-06-03-12-52-53.gh-issue-79096.YVoxgC.rst | 1 + 1 file changed, 1 insertion(+) create mode 100644 Misc/NEWS.d/next/Security/2022-06-03-12-52-53.gh-issue-79096.YVoxgC.rst diff --git a/Misc/NEWS.d/next/Security/2022-06-03-12-52-53.gh-issue-79096.YVoxgC.rst b/Misc/NEWS.d/next/Security/2022-06-03-12-52-53.gh-issue-79096.YVoxgC.rst new file mode 100644 index 00000000000000..9ec3335dc71b92 --- /dev/null +++ b/Misc/NEWS.d/next/Security/2022-06-03-12-52-53.gh-issue-79096.YVoxgC.rst @@ -0,0 +1 @@ +LWPCookieJar and MozillaCookieJar create files with file mode 600 instead of 644 (Microsoft Windows is not affected)