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
The buildserver VM has not been upgraded yet to bullseye, so it is still on
Debian/stretch. The buildserver VM does not need to run `fdroid update`,
`fdroid signindex`, etc. so this new apksigner requirement should not
affect app builds even though they are stuck on Debian/stretch.
The current signing method uses apksigner to sign the JAR so that it
will automatically select algorithms that are compatible with Android
SDK 23, which added the most recent algorithms:
https://developer.android.com/reference/java/security/Signature
This signing method uses then inherits the default signing algothim
settings, since Java and Android both maintain those. That helps
avoid a repeat of being stuck on an old signing algorithm. That means
specifically that this call to apksigner does not specify any of the
algorithms.
The old indexes must be signed by SHA1withRSA otherwise they will no
longer be compatible with old Androids.
apksigner 30.0.0+ is available in Debian/bullseye, Debian/buster-backports,
Ubuntu 21.10, and Ubuntu 20.04 from the fdroid PPA. Here's a quick way to
test:
for f in `ls -1 /opt/android-sdk/build-tools/*/apksigner | sort ` /usr/bin/apksigner; do printf "$f : "; $f sign --v4-signing-enabled false; done
closes#1005
With ~index-v2, the model is changing to offer the plain JSON file for easy
consumption. Then gpgsign will also provide a detached PGP signature for
systems that would rather verify based on PGP signatures than JAR signatures.
!1080closes#969
