8000 [3.7] gh-97612: Fix shell injection in get-remote-certificate.py (#97613) by vstinner · Pull Request #97634 · python/cpython · GitHub
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[3.7] gh-97612: Fix shell injection in get-remote-certificate.py (#97613) #97634

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Merged
merged 1 commit into from
Oct 5, 2022
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[3.7] gh-97612: Fix shell injection in get-remote-certificate.py (#97613) #97634

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gh-97612: Fix shell injection in get-remote-certificate.py (#97613) 
Fix a shell code injection vulnerability in the
get-remote-certificate.py example script. The script no longer uses a
shell to run "openssl" commands. Issue reported and initial fix by
Caleb Shortt.

Remove the Windows code path to send "quit" on stdin to the "openssl
s_client" command: use DEVNULL on all platforms instead.

Co-authored-by: Caleb Shortt <caleb@rgauge.com>
(cherry picked from commit 83a0f44)
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@vstinner @calebshortt
vstinner and calebshortt committed < 8000 relative-time datetime="2022-09-28T23:20:38Z" class="no-wrap">Sep 28, 2022
commit aeb5324b048adb1add52aca5918ee25c276e7fd4
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Security/2022-09-28-12-10-57.gh-issue-97612.y6NvOQ.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix a shell code injection vulnerability in the ``get-remote-certificate.py``
example script. The script no longer uses a shell to run ``openssl`` commands.
Issue reported and initial fix by Caleb Shortt. Patch by Victor Stinner.
26 changes: 7 additions & 19 deletions Tools/scripts/get-remote-certificate.py
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4138
Original file line number Diff line number Diff line change
Expand Up @@ -15,8 +15,8 @@
def fetch_server_certificate (host, port):

def subproc(cmd):
from subprocess import Popen, PIPE, STDOUT
proc = Popen(cmd, stdout=PIPE, stderr=STDOUT, shell=True)
from subprocess import Popen, PIPE, STDOUT, DEVNULL
proc = Popen(cmd, stdout=PIPE, stderr=STDOUT, stdin=DEVNULL)
status = proc.wait()
output = proc.stdout.read()
return status, output
Expand All @@ -34,8 +34,8 @@ def strip_to_x509_cert(certfile_contents, outfile=None):
fp.close()
try:
tn2 = (outfile or tempfile.mktemp())
status, output = subproc(r'openssl x509 -in "%s" -out "%s"' %
(tn, tn2))
cmd = ['openssl', 'x509', '-in', tn, '-out', tn2]
status, output = subproc(cmd)
if status != 0:
raise RuntimeError('OpenSSL x509 failed with status %s and '
'output: %r' % (status, output))
Expand All @@ -47,21 +47,9 @@ def strip_to_x509_cert(certfile_contents, outfile=None):
finally:
os.unlink(tn)

if sys.platform.startswith("win"):
tfile = tempfile.mktemp()
fp = open(tfile, "w")
fp.write("quit\n")
fp.close()
try:
status, output = subproc(
'openssl s_client -connect "%s:%s" -showcerts < "%s"' %
(host, port, tfile))
finally:
os.unlink(tfile)
else:
status, output = subproc(
'openssl s_client -connect "%s:%s" -showcerts < /dev/null' %
(host, port))
cmd = ['openssl', 's_client', '-connect', '%s:%s' % (host, port), '-showcerts']
status, output = subproc(cmd)

if status != 0:
raise RuntimeError('OpenSSL connect failed with status %s and '
'output: %r' % (status, output))
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