Fix subfolders in encrypted folders by daniele-verducci · Pull Request #17608 · nextcloud/android

daniele-verducci · 2026-09-10T16:58:22Z

How to repro:

create encrypted folder
create encrypted subfolder inside the one just created
app crashes

How to repro 2:

enter encrypted folder
enter encrypted subfolder inside the previous one
app crashes

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github-actions · 2026-09-10T17:05:41Z

APK file: https://github.com/nextcloud/android/actions/runs/34505348733/artifacts/10163844801
To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.
(please click on link to get QR code displayed)

github-actions · 2026-09-10T17:29:03Z

master-IT test failed: https://www.kaminsky.me/nc-dev/android-integrationTests/17608-IT-master-17-26

github-actions · 2026-09-14T08:13:30Z

📱 QA build


Download	app-qa-debug.apk (76M)
QR code	Open the QR code for this download
Commit	`3d34758`
Version	`17608`
Available until	7 days after this build

The QA build installs alongside a released Nextcloud app, so you can keep
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Downloading the file requires a GitHub account, so open this link on the
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codecov · 2026-09-14T08:31:46Z

Codecov Report

❌ Patch coverage is 7.14286% with 13 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../java/com/nextcloud/utils/e2ee/E2EEKeyInspector.kt	0.00%	12 Missing ⚠️
...va/com/owncloud/android/utils/EncryptionUtilsV2.kt	0.00%	0 Missing and 1 partial ⚠️

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alperozturk96

Could you please share the crash-log and explain your approach?

alperozturk96 · 2026-09-14T09:57:16Z


        return try {
-            EncryptionUtils.decryptStringAsymmetricV2(user.encryptedMetadataKey, privateKey)
+            EncryptionUtils.decryptStringAsymmetricV2(user.decryptedMetadataKey, privateKey)


Why we are trying to decrypt the decrypted metadata key here?

I see, this doesn't make sense. The result is not used, so I believe this call in the previous code was used to throw an exception if the key isn't valid. Is it a correct interpretation?

In that case, maybe I can get directly the key with retrieveTopMostMetadataKey(). It should throw an exception as well.
But then should I verify the key in any way?

alperozturk96 · 2026-09-14T09:58:51Z

-        val metadataFile = EncryptionUtils.deserializeJSON(
-            serializedMetadata,
-            object : TypeToken<EncryptedFolderMetadataFile>() {}
+    private fun decryptsMetadataV2(ocFile: OCFile, privateKey: String, client: OwnCloudClient): Boolean {


Previously GetMetadataRemoteOperation was already given the metadata why now we need to retrieveTopMostMetadata and also eventually call decryptFolderMetadataFile ?

GetMetadataRemoteOperation retrieves the metadata for the current folder, but I saw with the debugger that the users array is present only if the folder is the root encrypted folder. If we are in a subfolder, it's not. I think this isn't a server bug because it's working in the web version (checked the calls and the answer is the same, just in XML instead of JSON, so they must be keeping the root encrypted folder's key and using it for the subfolders, I believe)

daniele-verducci · 2026-09-14T10:10:46Z

Could you please share the crash-log and explain your approach?

Hey Alper, here's the crashlog:


2026-09-14 12:06:21.801  4737-4737  AndroidRuntime          com.nextcloud.client                 E  FATAL EXCEPTION: main
                                                                                                    Process: com.nextcloud.client, PID: 4737
                                                                                                    java.lang.NullPointerException: Attempt to invoke interface method 'java.util.Iterator java.lang.Iterable.iterator()' on a null object reference
                                                                                                    	at com.nextcloud.utils.e2ee.E2EEKeyInspector.decryptsMetadataV2(E2EEKeyInspector.kt:117)
                                                                                                    	at com.nextcloud.utils.e2ee.E2EEKeyInspector.access$decryptsMetadataV2(E2EEKeyInspector.kt:33)
                                                                                                    	at com.nextcloud.utils.e2ee.E2EEKeyInspector$canDecryptFolderMetadata$2.invokeSuspend(E2EEKeyInspector.kt:105)
                                                                                                    	at com.nextcloud.utils.e2ee.E2EEKeyInspector$canDecryptFolderMetadata$2.invoke(E2EEKeyInspector.kt:8)
                                                                                                    	at com.nextcloud.utils.e2ee.E2EEKeyInspector$canDecryptFolderMetadata$2.invoke(E2EEKeyInspector.kt:4)
                                                                                                    	at kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatched(Undispatched.kt:66)
                                                                                                    	at kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn(Undispatched.kt:43)
                                                                                                    	at kotlinx.coroutines.BuildersKt__Builders_commonKt.withContext(Builders.common.kt:497)
                                                                                                    	at kotlinx.coroutines.BuildersKt.withContext(dex-id-4119e2f2b95ce035797d115b10131393af91e27e:1)
                                                                                                    	at com.nextcloud.utils.e2ee.E2EEKeyInspector.canDecryptFolderMetadata(E2EEKeyInspector.kt:86)
                                                                                                    	at com.nextcloud.utils.e2ee.E2EEActionResolver$checkFolderMetadataKey$2.invokeSuspend(E2EEActionResolver.kt:44)
                                                                                                    	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:34)
                                                                                                    	at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:100)
                                                                                                    	at kotlinx.coroutines.internal.LimitedDispatcher$Worker.run(LimitedDispatcher.kt:124)
                                                                                                    	at kotlinx.coroutines.scheduling.TaskImpl.run(Tasks.kt:89)
                                                                                                    	at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:586)
                                                                                                    	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:798)
                                                                                                    	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:717)
                                                                                                    	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:704)
                                                                                                    	Suppressed: kotlinx.coroutines.internal.DiagnosticCoroutineContextException: [StandaloneCoroutine{Cancelling}@5e01fcc, Dispatchers.Main.immediate]

This happens when opening a subfolder on an encrypted folder. The crash is caused by the users array being empty/null (the user is used to retrieve the key).
I checked on the web watching the requests and I saw the users array being empty there as well, so I figured out they are using the parent encrypted folder's key.
I then replaced the piece of code that obtains the user array from the current folder with one that retrieves the topmost encrypted folder (that always has the users array populated) and uses its key.

I can say it works, but I'm not sure it's the correct fix. What do you think about it?

daniele-verducci · 2026-09-14T11:10:27Z

@alperozturk96 Can you check last commit? Could it be a solution?

github-actions · 2026-09-14T11:25:49Z

blue-Light-Screenshot test failed, but no output was generated. Maybe a preliminary stage failed.

Signed-off-by: daniele-verducci <daniele.verducci@nextcloud.com>

…etrieval function) Signed-off-by: daniele-verducci <daniele.verducci@nextcloud.com> Signed-off-by: daniele-verducci <daniele.verducci@nextcloud.com>

Signed-off-by: daniele-verducci <daniele.verducci@nextcloud.com>

This reverts commit 7bdb3c3. Signed-off-by: daniele-verducci <daniele.verducci@nextcloud.com>

Signed-off-by: daniele-verducci <daniele.verducci@nextcloud.com>

alperozturk96 · 2026-09-15T09:54:11Z

        return try {
-            EncryptionUtils.decryptStringAsymmetricV2(user.encryptedMetadataKey, privateKey)
-            true
+            val metadataKey = EncryptionUtilsV2().retrieveTopMostMetadataKey(


I saw this comment in the master. @tobiasKaminsky I think using retrieveTopMostMetadataKey directly here is okay. What do you think?

// we are in a subfolder, decrypt information is in top most encrypted folder

github-actions · 2026-09-15T10:54:15Z

Codacy

SpotBugs

Category	Base	New
Bad practice	32	32
Correctness	58	58
Dodgy code	186	186
Experimental	1	1
Malicious code vulnerability	2	2
Multithreaded correctness	26	26
Performance	37	37
Security	19	19
Total	361	361

daniele-verducci added the 1. to develop label Sep 10, 2026

daniele-verducci force-pushed the fix/internal-105265 branch from 5da4dab to 531efbc Compare September 14, 2026 08:02

daniele-verducci added 3. to review and removed 1. to develop labels Sep 14, 2026

daniele-verducci requested review from alperozturk96 and tobiasKaminsky and removed request for alperozturk96 September 14, 2026 08:04

alperozturk96 force-pushed the fix/internal-105265 branch from 531efbc to 0f71ff1 Compare September 14, 2026 09:43

alperozturk96 reviewed Sep 14, 2026

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daniele-verducci force-pushed the fix/internal-105265 branch from 0f71ff1 to 7bdb3c3 Compare September 14, 2026 11:08

daniele-verducci requested a review from alperozturk96 September 14, 2026 11:08

daniele-verducci added 5 commits September 15, 2026 11:45

Fix subfolders in encrypted folders

b4ec7cf

Signed-off-by: daniele-verducci <daniele.verducci@nextcloud.com>

Better fix subfolders in encrypted folders (using existing metadata r…

def4dc8

…etrieval function) Signed-off-by: daniele-verducci <daniele.verducci@nextcloud.com> Signed-off-by: daniele-verducci <daniele.verducci@nextcloud.com>

Proposal to fix metadata key check

2af829d

Signed-off-by: daniele-verducci <daniele.verducci@nextcloud.com>

Revert "Updated android-library"

be8cf44

This reverts commit 7bdb3c3. Signed-off-by: daniele-verducci <daniele.verducci@nextcloud.com>

Rebased

3d34758

Signed-off-by: daniele-verducci <daniele.verducci@nextcloud.com>

daniele-verducci force-pushed the fix/internal-105265 branch from 7bdb3c3 to 3d34758 Compare September 15, 2026 09:49

alperozturk96 reviewed Sep 15, 2026

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