OutOfMemoryError when restoring/playing large video — FileVaultManager.decryptToOutput loads entire file into memory

[Dawn-27]

Device: Nothing Phone (A059) — codename Asteroids
Android version: Android 16 (SDK 36)
ROM: AxionOS
App: AxSandbox (com.android.axion.sandbox)

Description:
When trying to restore or play a video stored in the vault, the app
consistently crashes with an OutOfMemoryError. The video's metadata
shows as "0 x 0 • 0 B" and duration "00:00" in the UI, indicating the
decrypted data is never successfully loaded.

This happens on every attempt (restore, play, viewing file info),
suggesting the video is too large for FileVaultManager's current
decryption approach, which appears to buffer the entire file in
memory via ByteArrayOutputStream rather than streaming it to disk.

A restore attempt does create a 0-byte placeholder file at
Download/Vault_Restored/ before crashing, confirming the
process dies mid-write.

Crash log:
07-12 10:54:17.099 25755 25781 E AndroidRuntime: FATAL EXCEPTION: DefaultDispatcher-worker-2
07-12 10:54:17.099 25755 25781 E AndroidRuntime: Process: com.android.axion.sandbox, PID: 25755
07-12 10:54:17.099 25755 25781 E AndroidRuntime: java.lang.OutOfMemoryError: Failed to allocate a 134201360 byte allocation with 93452416 free bytes and 89MB until OOM, target footprint 268435456, growth limit 268435456
at java.util.Arrays.copyOf(Arrays.java:3785)
at java.io.ByteArrayOutputStream.grow(ByteArrayOutputStream.java:120)
at java.io.ByteArrayOutputStream.ensureCapacity(ByteArrayOutputStream.java:95)
at java.io.ByteArrayOutputStream.write(ByteArrayOutputStream.java:156)
at java.io.OutputStream.write(OutputStream.java:127)
at android.security.keystore2.AndroidKeyStoreAuthenticatedAESCipherSpi$BufferAllOutputUntilDoFinalStreamer.update(AndroidKeyStoreAuthenticatedAESCipherSpi.java:385)
at android.security.keystore2.AndroidKeyStoreCipherSpiBase.engineUpdate(AndroidKeyStoreCipherSpiBase.java:434)
at javax.crypto.Cipher.update(Cipher.java:1741)
at com.android.axion.sandbox.io.FileVaultManager.decryptToOutput(FileVaultManager.kt:265)
at com.android.axion.sandbox.io.FileVaultManager.prepareMediaStoreUriLocked(FileVaultManager.kt:378)
at com.android.axion.sandbox.io.FileVaultManager.prepareMediaStoreUri(FileVaultManager.kt:337)
at com.android.axion.sandbox.ui.VaultTabKt$VaultTab$refreshFiles$1.invokeSuspend(VaultTab.kt:91)

This is currently trapping an important personal video file with no
way to recover it. Please consider fixing decryptToOutput to stream
data directly to disk instead of buffering the entire file in memory
(e.g. process in chunks rather than one full ByteArrayOutputStream).

[Dawn-27]

@rmp22 Hey, tagging you since you've contributed to this repo. Ran into
this OOM crash trying to restore a large video from the vault — the
crash log points pretty clearly to FileVaultManager.decryptToOutput
buffering the whole file in memory instead of streaming it. This has
an important personal file trapped with no workaround on my end. Would
really appreciate if you could take a look when you have time — happy
to test a fix or provide more logs if needed. Thanks!

[rmp22]

Thanks for the bug report! It looks like this was caused by a large temporary heap allocation during decryption. Please open a new issue here: https://github.com/AxionAOSP/issue_tracker/issues so we can track the issue easily. ps: already investigating this issue