build-apks using keystore(2048bit keysize SHA256withDSA sigalg) is not supported?

[sdsd08013]

Describe the bug
I tried to generate apks from abb and failed.

I'm not sure but I think it's caused by lack of minSdkVersion attribute part of splitApkManifest.
https://github.com/google/bundletool/blob/master/src/main/java/com/android/tools/build/bundletool/splitters/ModuleSplitter.java#L129
https://github.com/google/bundletool/blob/master/src/main/java/com/android/tools/build/bundletool/model/ModuleSplit.java#L266
https://android.googlesource.com/platform/tools/apksig/+/refs/heads/master/src/main/java/com/android/apksig/internal/apk/v1/V1SchemeSigner.java#124

Bundletool version(s) affected
Version: 0.12.0

Stacktrace

[BT:0.12.0] Error: Failed to write APK file '/var/folders/z0/r46_v2n94ts8j__q3txlqtkr0000gn/T/2973773764400014628/splits/base-xxhdpi.apk'.
java.io.UncheckedIOException: Failed to write APK file '/var/folders/z0/r46_v2n94ts8j__q3txlqtkr0000gn/T/2973773764400014628/splits/base-xxhdpi.apk'.
	at com.android.tools.build.bundletool.io.ConcurrencyUtils.waitFor(ConcurrencyUtils.java:55)
	at com.android.tools.build.bundletool.io.ConcurrencyUtils.waitForAll(ConcurrencyUtils.java:42)
	at java.util.function.Function.lambda$andThen$1(Function.java:88)
	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:570)
	at com.android.tools.build.bundletool.io.ApkSerializerManager.serializeApks(ApkSerializerManager.java:181)
	at com.android.tools.build.bundletool.io.ApkSerializerManager.populateApkSetBuilder(ApkSerializerManager.java:101)
	at com.android.tools.build.bundletool.commands.BuildApksManager.executeWithZip(BuildApksManager.java:233)
	at com.android.tools.build.bundletool.commands.BuildApksManager.execute(BuildApksManager.java:117)
	at com.android.tools.build.bundletool.commands.BuildApksCommand.execute(BuildApksCommand.java:532)
	at com.android.tools.build.bundletool.BundleToolMain.main(BundleToolMain.java:74)
	at com.android.tools.build.bundletool.BundleToolMain.main(BundleToolMain.java:46)
Caused by: java.io.IOException: Failed to generate v1 signature
	at com.android.tools.build.apkzlib.sign.SigningExtension.onOutputZipReadyForUpdate(SigningExtension.java:287)
	at com.android.tools.build.apkzlib.sign.SigningExtension.access$200(SigningExtension.java:57)
	at com.android.tools.build.apkzlib.sign.SigningExtension$1.lambda$beforeUpdate$2(SigningExtension.java:156)
	at com.android.tools.build.apkzlib.zip.ZFile.notify(ZFile.java:2269)
	at com.android.tools.build.apkzlib.zip.ZFile.update(ZFile.java:1002)
	at com.android.tools.build.apkzlib.zip.ZFile.close(ZFile.java:1335)
	at com.android.tools.build.bundletool.io.ApkSerializerHelper.writeToZipFile(ApkSerializerHelper.java:196)
	at com.android.tools.build.bundletool.io.ApkSerializerHelper.writeToZipFile(ApkSerializerHelper.java:139)
	at com.android.tools.build.bundletool.io.SplitApkSerializer.writeToDisk(SplitApkSerializer.java:75)
	at com.android.tools.build.bundletool.io.SplitApkSerializer.writeSplitToDisk(SplitApkSerializer.java:53)
	at com.android.tools.build.bundletool.io.ApkSetBuilderFactory$ApkSetArchiveBuilder.addSplitApk(ApkSetBuilderFactory.java:105)
	at com.android.tools.build.bundletool.io.ApkSerializerManager$ApkSerializer.serialize(ApkSerializerManager.java:377)
	at com.android.tools.build.bundletool.io.ApkSerializerManager.lambda$null$3(ApkSerializerManager.java:185)
	at com.google.common.util.concurrent.TrustedListenableFutureTask$TrustedFutureInterruptibleTask.runInterruptibly(TrustedListenableFutureTask.java:117)
	at com.google.common.util.concurrent.InterruptibleTask.run(InterruptibleTask.java:38)
	at com.google.common.util.concurrent.TrustedListenableFutureTask.run(TrustedListenableFutureTask.java:77)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.security.InvalidKeyException: Failed to sign using signer "CERT"
	at com.android.apksig.internal.apk.v1.V1SchemeSigner.signManifest(V1SchemeSigner.java:295)
	at com.android.apksig.internal.apk.v1.V1SchemeSigner.sign(V1SchemeSigner.java:256)
	at com.android.apksig.DefaultApkSignerEngine.outputJarEntries(DefaultApkSignerEngine.java:424)
	at com.android.tools.build.apkzlib.sign.SigningExtension.onOutputZipReadyForUpdate(SigningExtension.java:285)
	... 18 more
Caused by: java.security.InvalidKeyException: Failed to sign using SHA1withDSA
	at com.android.apksig.internal.apk.v1.V1SchemeSigner.generateSignatureBlock(V1SchemeSigner.java:519)
	at com.android.apksig.internal.apk.v1.V1SchemeSigner.signManifest(V1SchemeSigner.java:293)
	... 21 more
Caused by: java.security.InvalidKeyException: The security strength of SHA-1 digest algorithm is not sufficient for this key size
	at sun.security.provider.DSA.checkKey(DSA.java:111)
	at sun.security.provider.DSA.engineInitSign(DSA.java:143)
	at java.security.Signature$Delegate.init(Signature.java:1155)
	at java.security.Signature$Delegate.chooseProvider(Signature.java:1115)
	at java.security.Signature$Delegate.engineInitSign(Signature.java:1179)
	at java.security.Signature.initSign(Signature.java:530)
	at com.android.apksig.internal.apk.v1.V1SchemeSigner.generateSignatureBlock(V1SchemeSigner.java:515)

To Reproduce

1. create baz.keystore.

• keyalg DSA
• keysize 2048

2. execute bellow command line.

bundletool build-apks \                               
             --bundle=foo.aab \
             --output=bar.apks \
             --ks=baz.keystore \
             --ks-pass=pass:foo \
             --ks-key-alias=bar \
             --key-pass=pass:foo \
             --connected-device

Known workaround
use SHA256withDSA keystore (keysize 1024bit length)
use SHA256withRSA keystore

Environment:
OS: macOS Mojave 10.14.3
connected-device: Pixel3 API28

[plecesne]

This is a restriction of the JDK which doesn't allow using SHA-1 with 2048 bit keys: https://github.com/JetBrains/jdk8u_jdk/blob/master/src/share/classes/sun/security/provider/DSA.java#L111-L112

Using SHA-1 is unfortunately required due to the minSdkVersion your app uses because otherwise some devices your app targets wouldn't be able to install the app.

You thus have the options to either use a 1024 bit key, up the minSdkVersion to 21(?), or use an RSA key (not sure in which Android version support for SHA-256 was added nor if JDK has any such restriction as well, you'll have to test).

Hope that helps.

[sdsd08013]

Thanks for replying.

This specification(bundletool does not support signing apk using SHA256withDSA 2048 bit length keystore) is documented anywhere or commonly known?(I didnt know about this...)

[plecesne]

Bundletool supports it. It's a limitation of the JDK you are using. https://www.java.com/en/configure_crypto.html may be helpful to change the requirements of your JDK.

We could possibly do the signing with a different cryptographic provider, but I'm not sure we would do developers a favour by doing so.