adding dedicated error for missing room keys cipher

features/settings/src/main/kotlin/app/dapk/st/settings/SettingsScreen.kt

@@ -156,6 +156,7 @@ internal fun SettingsScreen(viewModel: SettingsViewModel, onSignOut: () -> Unit,
                                 ImportResult.Error.Type.UnexpectedDecryptionOutput -> "Unable to decrypt file, double check your passphrase"
                                 is ImportResult.Error.Type.Unknown -> "${type.cause::class.java.simpleName}: ${type.cause.message}"
                                 ImportResult.Error.Type.UnableToOpenFile -> "Unable to open file"
+                                ImportResult.Error.Type.InvalidFile -> "Unable to process file"
                             }
 
                             Text(text = "Import failed\n$message", textAlign = TextAlign.Center)

matrix/services/crypto/src/main/kotlin/app/dapk/st/matrix/crypto/CryptoService.kt

@@ -184,6 +184,7 @@ sealed interface ImportResult {
             object NoKeysFound : Type
             object UnexpectedDecryptionOutput : Type
             object UnableToOpenFile : Type
+            object InvalidFile : Type
         }
 
     }

matrix/services/crypto/src/main/kotlin/app/dapk/st/matrix/crypto/internal/RoomKeyImporter.kt

@@ -86,21 +86,27 @@ class RoomKeyImporter(
             val line = it.joinToString(separator = "").replace("\n", "")
             val toByteArray = base64.decode(line)
             if (index == 0) {
-                decryptCipher.initialize(toByteArray, password)
-                toByteArray
-                    .copyOfRange(37, toByteArray.size)
-                    .decrypt(decryptCipher)
-                    .also {
-                        if (!it.startsWith("[{")) {
-                            throw ImportException(ImportResult.Error.Type.UnexpectedDecryptionOutput)
-                        }
+                toByteArray.ensureHasCipherPayloadOrThrow()
+                val initializer = toByteArray.copyOfRange(0, 37)
+                decryptCipher.initialize(initializer, password)
+                val content = toByteArray.copyOfRange(37, toByteArray.size)
+                content.decrypt(decryptCipher).also {
+                    if (!it.startsWith("[{")) {
+                        throw ImportException(ImportResult.Error.Type.UnexpectedDecryptionOutput)
                     }
+                }
             } else {
                 toByteArray.decrypt(decryptCipher)
             }
         }
     }
 
+    private fun ByteArray.ensureHasCipherPayloadOrThrow() {
+        if (this.size < 37) {
+            throw ImportException(ImportResult.Error.Type.InvalidFile)
+        }
+    }
+
     private fun Cipher.initialize(payload: ByteArray, passphrase: String) {
         val salt = payload.copyOfRange(1, 1 + 16)
         val iv = payload.copyOfRange(17, 17 + 16)
@@ -176,6 +182,7 @@ private class JsonAccumulator {
                     jsonSegment = withLatest
                     null
                 }
+
                 else -> {
                     val string = withLatest.substring(objectRange)
                     importJson.decodeFromString(ElementMegolmExportObject.serializer(), string).also {
@@ -200,6 +207,7 @@ private class JsonAccumulator {
                     }
                     opens++
                 }
+
                 c == '}' -> {
                     opens--
                     if (opens == 0) {