Fix for CVE-2021-28861
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Lumir Balhar
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1fa182b4cb
commit
cd4147361f
3 changed files with 155 additions and 1 deletions
130
00386-cve-2021-28861.patch
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130
00386-cve-2021-28861.patch
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: "Miss Islington (bot)"
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<31488909+miss-islington@users.noreply.github.com>
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Date: Wed, 22 Jun 2022 15:05:00 -0700
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Subject: [PATCH] 00386: CVE-2021-28861
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Fix an open redirection vulnerability in the `http.server` module when
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an URI path starts with `//` that could produce a 301 Location header
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with a misleading target. Vulnerability discovered, and logic fix
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proposed, by Hamza Avvan (@hamzaavvan).
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Test and comments authored by Gregory P. Smith [Google].
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(cherry picked from commit 4abab6b603dd38bec1168e9a37c40a48ec89508e)
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Upstream: https://github.com/python/cpython/pull/93879
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Tracking bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2120642
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Co-authored-by: Gregory P. Smith <greg@krypto.org>
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---
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Lib/http/server.py | 7 +++
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Lib/test/test_httpservers.py | 53 ++++++++++++++++++-
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...2-06-15-20-09-23.gh-issue-87389.QVaC3f.rst | 3 ++
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3 files changed, 61 insertions(+), 2 deletions(-)
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create mode 100644 Misc/NEWS.d/next/Security/2022-06-15-20-09-23.gh-issue-87389.QVaC3f.rst
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diff --git a/Lib/http/server.py b/Lib/http/server.py
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index 60a4dadf03..ce05be13d3 100644
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--- a/Lib/http/server.py
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+++ b/Lib/http/server.py
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@@ -323,6 +323,13 @@ class BaseHTTPRequestHandler(socketserver.StreamRequestHandler):
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return False
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self.command, self.path, self.request_version = command, path, version
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+ # gh-87389: The purpose of replacing '//' with '/' is to protect
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+ # against open redirect attacks possibly triggered if the path starts
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+ # with '//' because http clients treat //path as an absolute URI
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+ # without scheme (similar to http://path) rather than a path.
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+ if self.path.startswith('//'):
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+ self.path = '/' + self.path.lstrip('/') # Reduce to a single /
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+
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# Examine the headers and look for a Connection directive.
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try:
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self.headers = http.client.parse_headers(self.rfile,
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diff --git a/Lib/test/test_httpservers.py b/Lib/test/test_httpservers.py
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index 66e937e04b..5a0a7c3f74 100644
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--- a/Lib/test/test_httpservers.py
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+++ b/Lib/test/test_httpservers.py
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@@ -324,7 +324,7 @@ class SimpleHTTPServerTestCase(BaseTestCase):
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pass
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def setUp(self):
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- BaseTestCase.setUp(self)
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+ super().setUp()
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self.cwd = os.getcwd()
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basetempdir = tempfile.gettempdir()
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os.chdir(basetempdir)
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@@ -343,7 +343,7 @@ class SimpleHTTPServerTestCase(BaseTestCase):
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except:
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pass
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finally:
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- BaseTestCase.tearDown(self)
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+ super().tearDown()
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def check_status_and_reason(self, response, status, data=None):
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def close_conn():
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@@ -399,6 +399,55 @@ class SimpleHTTPServerTestCase(BaseTestCase):
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self.check_status_and_reason(response, HTTPStatus.OK,
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data=support.TESTFN_UNDECODABLE)
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+ def test_get_dir_redirect_location_domain_injection_bug(self):
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+ """Ensure //evil.co/..%2f../../X does not put //evil.co/ in Location.
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+
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+ //netloc/ in a Location header is a redirect to a new host.
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+ https://github.com/python/cpython/issues/87389
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+
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+ This checks that a path resolving to a directory on our server cannot
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+ resolve into a redirect to another server.
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+ """
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+ os.mkdir(os.path.join(self.tempdir, 'existing_directory'))
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+ url = f'/python.org/..%2f..%2f..%2f..%2f..%2f../%0a%0d/../{self.tempdir_name}/existing_directory'
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+ expected_location = f'{url}/' # /python.org.../ single slash single prefix, trailing slash
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+ # Canonicalizes to /tmp/tempdir_name/existing_directory which does
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+ # exist and is a dir, triggering the 301 redirect logic.
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+ response = self.request(url)
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+ self.check_status_and_reason(response, HTTPStatus.MOVED_PERMANENTLY)
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+ location = response.getheader('Location')
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+ self.assertEqual(location, expected_location, msg='non-attack failed!')
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+
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+ # //python.org... multi-slash prefix, no trailing slash
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+ attack_url = f'/{url}'
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+ response = self.request(attack_url)
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+ self.check_status_and_reason(response, HTTPStatus.MOVED_PERMANENTLY)
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+ location = response.getheader('Location')
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+ self.assertFalse(location.startswith('//'), msg=location)
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+ self.assertEqual(location, expected_location,
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+ msg='Expected Location header to start with a single / and '
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+ 'end with a / as this is a directory redirect.')
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+
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+ # ///python.org... triple-slash prefix, no trailing slash
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+ attack3_url = f'//{url}'
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+ response = self.request(attack3_url)
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+ self.check_status_and_reason(response, HTTPStatus.MOVED_PERMANENTLY)
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+ self.assertEqual(response.getheader('Location'), expected_location)
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+
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+ # If the second word in the http request (Request-URI for the http
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+ # method) is a full URI, we don't worry about it, as that'll be parsed
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+ # and reassembled as a full URI within BaseHTTPRequestHandler.send_head
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+ # so no errant scheme-less //netloc//evil.co/ domain mixup can happen.
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+ attack_scheme_netloc_2slash_url = f'https://pypi.org/{url}'
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+ expected_scheme_netloc_location = f'{attack_scheme_netloc_2slash_url}/'
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+ response = self.request(attack_scheme_netloc_2slash_url)
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+ self.check_status_and_reason(response, HTTPStatus.MOVED_PERMANENTLY)
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+ location = response.getheader('Location')
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+ # We're just ensuring that the scheme and domain make it through, if
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+ # there are or aren't multiple slashes at the start of the path that
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+ # follows that isn't important in this Location: header.
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+ self.assertTrue(location.startswith('https://pypi.org/'), msg=location)
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+
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def test_get(self):
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#constructs the path relative to the root directory of the HTTPServer
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response = self.request(self.base_url + '/test')
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diff --git a/Misc/NEWS.d/next/Security/2022-06-15-20-09-23.gh-issue-87389.QVaC3f.rst b/Misc/NEWS.d/next/Security/2022-06-15-20-09-23.gh-issue-87389.QVaC3f.rst
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new file mode 100644
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index 0000000000..029d437190
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--- /dev/null
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+++ b/Misc/NEWS.d/next/Security/2022-06-15-20-09-23.gh-issue-87389.QVaC3f.rst
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@@ -0,0 +1,3 @@
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+:mod:`http.server`: Fix an open redirection vulnerability in the HTTP server
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+when an URI path starts with ``//``. Vulnerability discovered, and initial
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+fix proposed, by Hamza Avvan.
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@ -77,3 +77,9 @@ addFilter(r'\bpython3(\.\d+)?\.(src|spec): (E|W): specfile-error\s+$')
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# SPELLING ERRORS
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addFilter(r'spelling-error .* en_US (bytecode|pyc|filename|tkinter|namespaces|pytest) ')
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# These bundled provides are declared twice, as they're bundled twice
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# separately in pip and setuptools.
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addFilter(r'useless-provides bundled\(python3dist\(packaging\)\)')
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addFilter(r'useless-provides bundled\(python3dist\(setuptools\)\)')
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addFilter(r'useless-provides bundled\(python3dist\(six\)\)')
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@ -17,7 +17,7 @@ URL: https://www.python.org/
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#global prerel ...
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%global upstream_version %{general_version}%{?prerel}
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Version: %{general_version}%{?prerel:~%{prerel}}
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Release: 10%{?dist}
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Release: 11%{?dist}
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License: Python
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@ -497,6 +497,20 @@ Patch378: 00378-support-expat-2-4-5.patch
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# Tracker bug: https://bugzilla.redhat.com/show_bug.cgi?id=2075390
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Patch382: 00382-cve-2015-20107.patch
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# 00386 # 0e4bced7d3cd0f94ebfbcc209e10dbf81607b073
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# CVE-2021-28861
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#
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# Fix an open redirection vulnerability in the `http.server` module when
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# an URI path starts with `//` that could produce a 301 Location header
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# with a misleading target. Vulnerability discovered, and logic fix
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# proposed, by Hamza Avvan (@hamzaavvan).
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#
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# Test and comments authored by Gregory P. Smith [Google].
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#
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# Upstream: https://github.com/python/cpython/pull/93879
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# Tracking bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2120642
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Patch386: 00386-cve-2021-28861.patch
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# (New patches go here ^^^)
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#
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# When adding new patches to "python" and "python3" in Fedora, EL, etc.,
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@ -1687,6 +1701,10 @@ CheckPython optimized
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# ======================================================
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%changelog
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* Wed Sep 14 2022 Lumír Balhar <lbalhar@redhat.com> - 3.6.15-11
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- Fix for CVE-2021-28861
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Resolves: rhbz#2120785
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* Wed Jul 20 2022 Charalampos Stratakis <cstratak@redhat.com> - 3.6.15-10
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- Fix test_tarfile on ppc64le
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Resolves: rhbz#2109120
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