java.lang.NullPointerException: getEtag(...) must not be null

[TheLastZombie]

Overview

When trying to access a KeePass database file on a WebDAV server, KeePassVault crashes with the following error:

java.lang.NullPointerException: getEtag(...) must not be null
	at com.ivanovsky.passnotes.data.repository.file.webdav.WebDavClientV2.toRemoteFileMetadata(WebDavClientV2.kt:333)
	at com.ivanovsky.passnotes.data.repository.file.webdav.WebDavClientV2.toRemoteFileMetadata$default(WebDavClientV2.kt:319)
	at com.ivanovsky.passnotes.data.repository.file.webdav.WebDavClientV2.getFileMetadata(WebDavClientV2.kt:158)
	at com.ivanovsky.passnotes.data.repository.file.webdav.WebDavClientV2.getFileMetadata(WebDavClientV2.kt:138)
	at com.ivanovsky.passnotes.data.repository.file.remote.RemoteApiClientAdapter.getFileMetadataOrThrow(RemoteApiClientAdapter.kt:44)
	at com.ivanovsky.passnotes.data.repository.file.remote.RemoteFileSystemProvider.openFileForRead(RemoteFileSystemProvider.java:295)
	at com.ivanovsky.passnotes.data.repository.keepass.KeepassDatabaseRepository.open(KeepassDatabaseRepository.kt:53)
	at com.ivanovsky.passnotes.domain.interactor.unlock.UnlockInteractor$openDatabase$2.invokeSuspend(UnlockInteractor.kt:113)
	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
	at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:108)
	at kotlinx.coroutines.internal.LimitedDispatcher$Worker.run(LimitedDispatcher.kt:115)
	at kotlinx.coroutines.scheduling.TaskImpl.run(Tasks.kt:103)
	at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:584)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:793)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:697)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:684)
	Suppressed: kotlinx.coroutines.internal.DiagnosticCoroutineContextException: [StandaloneCoroutine{Cancelling}@8b5a6ee, Dispatchers.Main.immediate]

How to reproduce

1. Set up a WebDAV server. I've tried copyparty and dufs, the issue occurs with both.
2. Upload a KeePass database to the server.
3. Open KeePassVault and add the database to the list.
4. Enter the database password. When tapping the unlock button, the app crashes with the above message.

Version

1.9.0 (via F-Droid)

Android Version

Android 15 (GrapheneOS)

Device Model

Pixel 8 Pro

[9001]

KeepassVault expects the WebDAV server to provide an ETag, which it uses to ensure that the file contents have (or have not) been altered on the serverside. This makes perfect sense, but according to the WebDAV spec, it is not required that WebDAV servers implement ETag support. It is however strongly recommended.

Most of the synchronization-oriented WebDAV servers do have ETags, such as owncloud, nextcloud and seafile, as this is necessary to keep track of sync state, but many of the smaller lightweight servers do not. Usually the reason is that those servers do not keep track of file contents, and thus don't have a good basis for providing a strong ETag.

So the question is whether @aivanovski made the ETag requirement as a conscious decision. Most WebDAV servers operate at a 1-second precision in the last-modified timestamps, so I can understand the preference of a strong ETag, to be entirely certain of the server state. One approach could be for KeepassVault to generate its own weak ETags when necessary, based on the server's lastmodified header. But again, I understand if there is an apprehension towards this.

I'll quickly mention that copyparty is in a position where strong ETags could be provided, but performance concerns and (until now) a lack of interest has not made this a priority.

[aivanovski]

Hi @9001
Thank you for the detailed explanation. I didn't know that ETag is optional, it should be easy to replace it with last-modified when it is not available.

[aivanovski]

The fix is in version 1.10.0. Build is available in Releases page or will be available later in Google Play and F-Droid. Thanks for reporting this issue. @TheLastZombie