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jarsigner: allow weak signatures

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openjdk-11 11.0.17 in Debian unstable fails to verify weak signatures:

jarsigner -verbose -strict -verify tests/signindex/guardianproject.jar

         131 Fri Dec 02 20:10:00 CET 2016 META-INF/MANIFEST.MF
         252 Fri Dec 02 20:10:04 CET 2016 META-INF/1.SF
        2299 Fri Dec 02 20:10:04 CET 2016 META-INF/1.RSA
           0 Fri Dec 02 20:09:58 CET 2016 META-INF/
 m  ?  48743 Fri Dec 02 20:09:58 CET 2016 index.xml

  s = signature was verified
  m = entry is listed in manifest
  k = at least one certificate was found in keystore
  ? = unsigned entry

- Signed by "EMAILADDRESS=root@guardianproject.info, CN=guardianproject.info, O=Guardian Project, OU=FDroid Repo, L=New York, ST=New York, C=US"
    Digest algorithm: SHA1 (disabled)
    Signature algorithm: SHA1withRSA (disabled), 4096-bit key

WARNING: The jar will be treated as unsigned, because it is signed with a weak algorithm that is now disabled by the security property:

  jdk.jar.disabledAlgorithms=MD2, MD5, RSA keySize < 1024, DSA keySize < 1024, SHA1 denyAfter 2019-01-01, include jdk.disabled.namedCurves
This commit is contained in:
Jochen Sprickerhof 2022-10-29 22:09:07 +02:00
parent d4b6e95c4e
commit 1bb963d768
No known key found for this signature in database
GPG key ID: 5BFFDCC258E69433
5 changed files with 64 additions and 84 deletions
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89
fdroidserver/common.py
View file

@ -3416,13 +3416,27 @@ def verify_apks(signed_apk, unsigned_apk, tmp_dir, v1_only=None):
return None
def verify_jar_signature(jar):
def verify_deprecated_jar_signature(jar):
"""Verify the signature of a given JAR file.
jarsigner is very shitty: unsigned JARs pass as "verified"! So
this has to turn on -strict then check for result 4, since this
does not expect the signature to be from a CA-signed certificate.
Also used to verify the signature on an archived APK, supporting deprecated
algorithms.
F-Droid aims to keep every single binary that it ever published. Therefore,
it needs to be able to verify APK signatures that include deprecated/removed
algorithms. For example, jarsigner treats an MD5 signature as unsigned.
jarsigner passes unsigned APKs as "verified"! So this has to turn
on -strict then check for result 4.
Just to be safe, this never reuses the file, and locks down the
file permissions while in use. That should prevent a bad actor
from changing the settings during operation.
Raises
------
VerificationException
@ -3430,15 +3444,30 @@ def verify_jar_signature(jar):
"""
error = _('JAR signature failed to verify: {path}').format(path=jar)
_java_security = os.path.join(os.getcwd(), '.java.security')
if os.path.exists(_java_security):
os.remove(_java_security)
with open(_java_security, 'w') as fp:
fp.write('jdk.jar.disabledAlgorithms=MD2, RSA keySize < 1024')
os.chmod(_java_security, 0o400)
try:
output = subprocess.check_output([config['jarsigner'], '-strict', '-verify', jar],
stderr=subprocess.STDOUT)
cmd = [
config['jarsigner'],
'-J-Djava.security.properties=' + _java_security,
'-strict', '-verify', jar
]
output = subprocess.check_output(cmd, stderr=subprocess.STDOUT)
raise VerificationException(error + '\n' + output.decode('utf-8'))
except subprocess.CalledProcessError as e:
if e.returncode == 4:
logging.debug(_('JAR signature verified: {path}').format(path=jar))
else:
raise VerificationException(error + '\n' + e.output.decode('utf-8')) from e
finally:
if os.path.exists(_java_security):
os.chmod(_java_security, 0o600)
os.remove(_java_security)
def verify_apk_signature(apk, min_sdk_version=None):
@ -3471,63 +3500,13 @@ def verify_apk_signature(apk, min_sdk_version=None):
config['jarsigner_warning_displayed'] = True
logging.warning(_("Using Java's jarsigner, not recommended for verifying APKs! Use apksigner"))
try:
verify_jar_signature(apk)
verify_deprecated_jar_signature(apk)
return True
except Exception as e:
logging.error(e)
return False
def verify_old_apk_signature(apk):
"""Verify the signature on an archived APK, supporting deprecated algorithms.
F-Droid aims to keep every single binary that it ever published. Therefore,
it needs to be able to verify APK signatures that include deprecated/removed
algorithms. For example, jarsigner treats an MD5 signature as unsigned.
jarsigner passes unsigned APKs as "verified"! So this has to turn
on -strict then check for result 4.
Just to be safe, this never reuses the file, and locks down the
file permissions while in use. That should prevent a bad actor
from changing the settings during operation.
Returns
-------
Boolean
whether the APK was verified
"""
_java_security = os.path.join(os.getcwd(), '.java.security')
if os.path.exists(_java_security):
os.remove(_java_security)
with open(_java_security, 'w') as fp:
fp.write('jdk.jar.disabledAlgorithms=MD2, RSA keySize < 1024')
os.chmod(_java_security, 0o400)
try:
cmd = [
config['jarsigner'],
'-J-Djava.security.properties=' + _java_security,
'-strict', '-verify', apk
]
output = subprocess.check_output(cmd, stderr=subprocess.STDOUT)
except subprocess.CalledProcessError as e:
if e.returncode != 4:
output = e.output
else:
logging.debug(_('JAR signature verified: {path}').format(path=apk))
return True
finally:
if os.path.exists(_java_security):
os.chmod(_java_security, 0o600)
os.remove(_java_security)
logging.error(_('Old APK signature failed to verify: {path}').format(path=apk)
+ '\n' + output.decode('utf-8'))
return False
apk_badchars = re.compile('''[/ :;'"]''')
@ -3749,7 +3728,7 @@ def load_stats_fdroid_signing_key_fingerprints():
if not os.path.isfile(jar_file):
return {}
try:
verify_jar_signature(jar_file)
verify_deprecated_jar_signature(jar_file)
except VerificationException as e:
raise FDroidException("Signature validation of '{}' failed! "
"Please run publish again to rebuild this file.".format(jar_file)) from e