Create extension function `Context.safeOpenOutputStream`

vector/src/main/java/im/vector/app/core/extensions/Context.kt

@@ -18,6 +18,7 @@ package im.vector.app.core.extensions
 
 import android.content.Context
 import android.graphics.drawable.Drawable
+import android.net.Uri
 import android.text.Spannable
 import android.text.SpannableString
 import android.text.style.ImageSpan
@@ -31,6 +32,7 @@ import androidx.datastore.preferences.core.Preferences
 import dagger.hilt.EntryPoints
 import im.vector.app.core.datastore.dataStoreProvider
 import im.vector.app.core.di.SingletonEntryPoint
+import java.io.OutputStream
 import kotlin.math.roundToInt
 
 fun Context.singletonEntryPoint(): SingletonEntryPoint {
@@ -68,3 +70,10 @@ private fun Float.toAndroidAlpha(): Int {
 }
 
 val Context.dataStoreProvider: (String) -> DataStore<Preferences> by dataStoreProvider()
+
+/**
+ * Open Uri in truncate mode to make sure we don't partially overwrite content when we get passed a Uri to an existing file.
+ */
+fun Context.safeOpenOutputStream(uri: Uri): OutputStream? {
+    return contentResolver.openOutputStream(uri, "wt")
+}

vector/src/main/java/im/vector/app/features/crypto/keys/KeysExporter.kt

@@ -19,6 +19,7 @@ package im.vector.app.features.crypto.keys
 import android.content.Context
 import android.net.Uri
 import im.vector.app.core.dispatchers.CoroutineDispatchers
+import im.vector.app.core.extensions.safeOpenOutputStream
 import kotlinx.coroutines.withContext
 import org.matrix.android.sdk.api.session.Session
 import javax.inject.Inject
@@ -34,7 +35,7 @@ class KeysExporter @Inject constructor(
     suspend fun export(password: String, uri: Uri) {
         withContext(dispatchers.io) {
             val data = session.cryptoService().exportRoomKeys(password)
-            context.contentResolver.openOutputStream(uri, "wt")
+            context.safeOpenOutputStream(uri)
                     ?.use { it.write(data) }
                     ?: throw IllegalStateException("Unable to open file for writing")
             verifyExportedKeysOutputFileSize(uri, expectedSize = data.size.toLong())

vector/src/main/java/im/vector/app/features/crypto/keysbackup/setup/KeysBackupSetupStep3Fragment.kt

@@ -30,6 +30,7 @@ import com.google.android.material.bottomsheet.BottomSheetDialog
 import com.google.android.material.dialog.MaterialAlertDialogBuilder
 import im.vector.app.R
 import im.vector.app.core.extensions.registerStartForActivityResult
+import im.vector.app.core.extensions.safeOpenOutputStream
 import im.vector.app.core.platform.VectorBaseFragment
 import im.vector.app.core.utils.LiveEvent
 import im.vector.app.core.utils.copyToClipboard
@@ -165,7 +166,7 @@ class KeysBackupSetupStep3Fragment @Inject constructor() : VectorBaseFragment<Fr
         lifecycleScope.launch(Dispatchers.Main) {
             Try {
                 withContext(Dispatchers.IO) {
-                    requireContext().contentResolver.openOutputStream(uri, "wt")
+                    requireContext().safeOpenOutputStream(uri)
                             ?.use { os ->
                                 os.write(data.toByteArray())
                                 os.flush()

vector/src/main/java/im/vector/app/features/crypto/recover/BootstrapSaveRecoveryKeyFragment.kt

@@ -29,6 +29,7 @@ import com.airbnb.mvrx.parentFragmentViewModel
 import com.airbnb.mvrx.withState
 import im.vector.app.R
 import im.vector.app.core.extensions.registerStartForActivityResult
+import im.vector.app.core.extensions.safeOpenOutputStream
 import im.vector.app.core.platform.VectorBaseFragment
 import im.vector.app.core.resources.ColorProvider
 import im.vector.app.core.utils.startSharePlainTextIntent
@@ -81,7 +82,7 @@ class BootstrapSaveRecoveryKeyFragment @Inject constructor(
             val uri = activityResult.data?.data ?: return@registerStartForActivityResult
             lifecycleScope.launch(Dispatchers.IO) {
                 try {
-                    sharedViewModel.handle(BootstrapActions.SaveKeyToUri(requireContext().contentResolver!!.openOutputStream(uri, "wt")!!))
+                    sharedViewModel.handle(BootstrapActions.SaveKeyToUri(requireContext().safeOpenOutputStream(uri)!!))
                 } catch (failure: Throwable) {
                     sharedViewModel.handle(BootstrapActions.SaveReqFailed)
                 }

vector/src/main/java/im/vector/app/features/settings/devtools/KeyRequestsFragment.kt

@@ -34,6 +34,7 @@ import com.airbnb.mvrx.withState
 import com.google.android.material.tabs.TabLayoutMediator
 import im.vector.app.R
 import im.vector.app.core.extensions.registerStartForActivityResult
+import im.vector.app.core.extensions.safeOpenOutputStream
 import im.vector.app.core.platform.VectorBaseFragment
 import im.vector.app.core.utils.selectTxtFileToWrite
 import im.vector.app.databinding.FragmentDevtoolKeyrequestsBinding
@@ -106,7 +107,7 @@ class KeyRequestsFragment @Inject constructor() : VectorBaseFragment<FragmentDev
             when (it) {
                 is KeyRequestEvents.SaveAudit -> {
                     tryOrNull {
-                        requireContext().contentResolver?.openOutputStream(it.uri, "wt")
+                        requireContext().safeOpenOutputStream(it.uri)
                                 ?.use { os -> os.write(it.raw.toByteArray()) }
                     }
                 }

vector/src/test/java/im/vector/app/features/crypto/keys/KeysExporterTest.kt

@@ -53,7 +53,7 @@ class KeysExporterTest {
     @Test
     fun `when exporting then writes exported keys to context output stream`() {
         givenFileDescriptorWithSize(size = A_ROOM_KEYS_EXPORT.size.toLong())
-        val outputStream = context.givenOutputStreamFor(A_URI, mode = "wt")
+        val outputStream = context.givenSafeOutputStreamFor(A_URI)
 
         runTest { keysExporter.export(A_PASSWORD, A_URI) }
 
@@ -63,7 +63,7 @@ class KeysExporterTest {
     @Test
     fun `given different file size returned for export when exporting then throws UnexpectedExportKeysFileSizeException`() {
         givenFileDescriptorWithSize(size = 110)
-        context.givenOutputStreamFor(A_URI, mode = "wt")
+        context.givenSafeOutputStreamFor(A_URI)
 
         assertFailsWith<UnexpectedExportKeysFileSizeException> {
             runTest { keysExporter.export(A_PASSWORD, A_URI) }
@@ -72,7 +72,7 @@ class KeysExporterTest {
 
     @Test
     fun `given output stream is unavailable for exporting to when exporting then throws IllegalStateException`() {
-        context.givenMissingOutputStreamFor(A_URI, mode = "wt")
+        context.givenMissingSafeOutputStreamFor(A_URI)
 
         assertFailsWith<IllegalStateException>(message = "Unable to open file for writing") {
             runTest { keysExporter.export(A_PASSWORD, A_URI) }
@@ -82,7 +82,7 @@ class KeysExporterTest {
     @Test
     fun `given exported file is missing after export when exporting then throws IllegalStateException`() {
         context.givenFileDescriptor(A_URI, mode = "r") { null }
-        context.givenOutputStreamFor(A_URI, mode = "wt")
+        context.givenSafeOutputStreamFor(A_URI)
 
         assertFailsWith<IllegalStateException>(message = "Exported file not found") {
             runTest { keysExporter.export(A_PASSWORD, A_URI) }

vector/src/test/java/im/vector/app/test/fakes/FakeContext.kt

@@ -39,13 +39,13 @@ class FakeContext(
         every { contentResolver.openFileDescriptor(uri, mode, null) } returns fileDescriptor
     }
 
-    fun givenOutputStreamFor(uri: Uri, mode: String): OutputStream {
+    fun givenSafeOutputStreamFor(uri: Uri): OutputStream {
         val outputStream = mockk<OutputStream>(relaxed = true)
-        every { contentResolver.openOutputStream(uri, mode) } returns outputStream
+        every { contentResolver.openOutputStream(uri, "wt") } returns outputStream
         return outputStream
     }
 
-    fun givenMissingOutputStreamFor(uri: Uri, mode: String) {
+    fun givenMissingSafeOutputStreamFor(uri: Uri) {
-        every { contentResolver.openOutputStream(uri, mode) } returns null
+        every { contentResolver.openOutputStream(uri, "wt") } returns null
     }
 }