175 lines
6.2 KiB
Diff
175 lines
6.2 KiB
Diff
From 9798e9ee85f1ba39c816fa08fd3d6168cc8b29e8 Mon Sep 17 00:00:00 2001
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From: Demi Marie Obenour <demi@invisiblethingslab.com>
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Date: Fri, 9 Apr 2021 13:03:03 -0400
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Subject: [PATCH] Use rpmkeys alone to verify signature
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This avoids having to actually parse the package to check its signature,
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which reduces attack surface. If the output of rpmkeys cannot be
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parsed, we assume the package is corrupt (the most likely cause).
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---
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dnf/rpm/miscutils.py | 126 ++++++++++++++++++++++---------------------
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1 file changed, 66 insertions(+), 60 deletions(-)
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diff --git a/dnf/rpm/miscutils.py b/dnf/rpm/miscutils.py
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index 5f2621c2..9d5b2860 100644
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--- a/dnf/rpm/miscutils.py
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+++ b/dnf/rpm/miscutils.py
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@@ -13,47 +13,84 @@
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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# Copyright 2003 Duke University
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-from __future__ import print_function, absolute_import
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-from __future__ import unicode_literals
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+from __future__ import print_function, absolute_import, unicode_literals
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-import rpm
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import os
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import subprocess
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import logging
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-
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-from dnf.i18n import ucd
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-from dnf.i18n import _
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from shutil import which
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+from dnf.i18n import _
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-logger = logging.getLogger('dnf')
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+_logger = logging.getLogger('dnf')
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+_rpmkeys_binary = None
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+def _find_rpmkeys_binary():
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+ global _rpmkeys_binary
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+ if _rpmkeys_binary is None:
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+ _rpmkeys_binary = which("rpmkeys")
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+ _logger.debug(_('Using rpmkeys executable at %s to verify signatures'),
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+ _rpmkeys_binary)
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+ return _rpmkeys_binary
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-def _verifyPkgUsingRpmkeys(package, installroot, fdno):
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- os.lseek(fdno, 0, os.SEEK_SET)
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- rpmkeys_binary = '/usr/bin/rpmkeys'
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- if not os.path.isfile(rpmkeys_binary):
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- rpmkeys_binary = which("rpmkeys")
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- logger.info(_('Using rpmkeys executable from {path} to verify signature for package: {package}.').format(
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- path=rpmkeys_binary, package=package))
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+def _process_rpm_output(data):
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+ # No signatures or digests = corrupt package.
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+ # There is at least one line for -: and another (empty) entry after the
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+ # last newline.
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+ if len(data) < 3 or data[0] != b'-:' or data[-1]:
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+ return 2
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+ seen_sig, missing_key, not_trusted, not_signed = False, False, False, False
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+ for i in data[1:-1]:
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+ if b': BAD' in i:
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+ return 2
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+ elif i.endswith(b': NOKEY'):
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+ missing_key = True
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+ elif i.endswith(b': NOTTRUSTED'):
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+ not_trusted = True
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+ elif i.endswith(b': NOTFOUND'):
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+ not_signed = True
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+ elif not i.endswith(b': OK'):
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+ return 2
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+ if not_trusted:
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+ return 3
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+ elif missing_key:
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+ return 1
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+ elif not_signed:
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+ return 4
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+ # we still check return code, so this is safe
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+ return 0
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- if not os.path.isfile(rpmkeys_binary):
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- logger.critical(_('Cannot find rpmkeys executable to verify signatures.'))
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- return 0
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+def _verifyPackageUsingRpmkeys(package, installroot):
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+ rpmkeys_binary = _find_rpmkeys_binary()
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+ if rpmkeys_binary is None or not os.path.isfile(rpmkeys_binary):
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+ _logger.critical(_('Cannot find rpmkeys executable to verify signatures.'))
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+ return 2
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- args = ('rpmkeys', '--checksig', '--root', installroot, '--define', '_pkgverify_level all', '-')
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+ # "--define=_pkgverify_level all" enforces signature checking;
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+ # "--define=_pkgverify_flags 0x0" ensures that all signatures and digests
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+ # are checked.
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+ args = ('rpmkeys', '--checksig', '--root', installroot, '--verbose',
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+ '--define=_pkgverify_level all', '--define=_pkgverify_flags 0x0',
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+ '-')
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with subprocess.Popen(
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args=args,
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executable=rpmkeys_binary,
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env={'LC_ALL': 'C'},
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- stdin=fdno,
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stdout=subprocess.PIPE,
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- cwd='/') as p:
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- data, err = p.communicate()
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- if p.returncode != 0 or data != b'-: digests signatures OK\n':
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- return 0
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- else:
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- return 1
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+ cwd='/',
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+ stdin=package) as p:
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+ data = p.communicate()[0]
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+ returncode = p.returncode
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+ if type(returncode) is not int:
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+ raise AssertionError('Popen set return code to non-int')
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+ # rpmkeys can return something other than 0 or 1 in the case of a
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+ # fatal error (OOM, abort() called, SIGSEGV, etc)
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+ if returncode >= 2 or returncode < 0:
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+ return 2
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+ ret = _process_rpm_output(data.split(b'\n'))
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+ if ret:
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+ return ret
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+ return 2 if returncode else 0
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def checkSig(ts, package):
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"""Takes a transaction set and a package, check it's sigs,
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@@ -63,40 +100,9 @@ def checkSig(ts, package):
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return 3 if the key is not trusted
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return 4 if the pkg is not gpg or pgp signed"""
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- value = 4
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- currentflags = ts.setVSFlags(0)
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- fdno = os.open(package, os.O_RDONLY)
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+ fdno = os.open(package, os.O_RDONLY|os.O_NOCTTY|os.O_CLOEXEC)
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try:
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- hdr = ts.hdrFromFdno(fdno)
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- except rpm.error as e:
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- if str(e) == "public key not available":
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- value = 1
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- elif str(e) == "public key not trusted":
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- value = 3
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- elif str(e) == "error reading package header":
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- value = 2
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- else:
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- raise ValueError('Unexpected error value %r from ts.hdrFromFdno when checking signature.' % str(e))
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- else:
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- # checks signature from an hdr
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- string = '%|DSAHEADER?{%{DSAHEADER:pgpsig}}:{%|RSAHEADER?{%{RSAHEADER:pgpsig}}:' \
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- '{%|SIGGPG?{%{SIGGPG:pgpsig}}:{%|SIGPGP?{%{SIGPGP:pgpsig}}:{(none)}|}|}|}|'
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- try:
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- siginfo = hdr.sprintf(string)
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- siginfo = ucd(siginfo)
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-
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- if siginfo == '(none)':
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- value = 4
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- elif "Key ID" in siginfo and _verifyPkgUsingRpmkeys(package, ts.ts.rootDir, fdno):
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- value = 0
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- else:
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- raise ValueError('Unexpected return value %r from hdr.sprintf when checking signature.' % siginfo)
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- except UnicodeDecodeError:
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- pass
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-
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- del hdr
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-
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- os.close(fdno)
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-
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- ts.setVSFlags(currentflags) # put things back like they were before
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+ value = _verifyPackageUsingRpmkeys(fdno, ts.ts.rootDir)
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+ finally:
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+ os.close(fdno)
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return value
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--
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2.35.1
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