Fix/dapp message signing (#1750)

* Wrap polkadot signing message in bytes tag if not wrapped already

* Code style

common/src/main/java/io/novafoundation/nova/common/utils/KotlinExt.kt

@@ -142,6 +142,18 @@ fun ByteArray.startsWith(prefix: ByteArray): Boolean {
     return true
 }
 
+fun ByteArray.endsWith(suffix: ByteArray): Boolean {
+    if (suffix.size > size) return false
+
+    val offset = size - suffix.size
+
+    suffix.forEachIndexed { index, byte ->
+        if (get(offset + index) != byte) return false
+    }
+
+    return true
+}
+
 fun ByteArray.windowed(windowSize: Int): List<ByteArray> {
     require(windowSize > 0) {
         "Window size should be positive"

common/src/test/java/io/novafoundation/nova/common/utils/KotlinExtTest.kt

@@ -0,0 +1,29 @@
+package io.novafoundation.nova.common.utils
+
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class KotlinExtTest {
+
+    @Test
+    fun `endsWith should return false for suffix bigger than content`() {
+        assertFalse(byteArrayOf(0, 1).endsWith(byteArrayOf(0, 1, 2)))
+    }
+
+    @Test
+    fun `endsWith should return true for suffix equal to the content`() {
+        assertTrue(byteArrayOf(0, 1, 2).endsWith(byteArrayOf(0, 1, 2)))
+    }
+
+    @Test
+    fun `endsWith should return true for correct suffix`() {
+        assertTrue(byteArrayOf(0, 1, 2).endsWith(byteArrayOf(1, 2)))
+    }
+
+    @Test
+    fun `endsWith should return true for incorrect suffix`() {
+        assertFalse(byteArrayOf(0, 1, 2, 3).endsWith(byteArrayOf(1, 2)))
+        assertFalse(byteArrayOf(0, 1, 2, 3).endsWith(byteArrayOf(2)))
+    }
+}

feature-external-sign-impl/src/main/java/io/novafoundation/nova/feature_external_sign_impl/domain/sign/polkadot/PolkadotExternalSignInteractor.kt

@@ -5,8 +5,10 @@ import io.novafoundation.nova.common.address.AddressIconGenerator
 import io.novafoundation.nova.common.address.AddressModel
 import io.novafoundation.nova.common.utils.asHexString
 import io.novafoundation.nova.common.utils.bigIntegerFromHex
+import io.novafoundation.nova.common.utils.endsWith
 import io.novafoundation.nova.common.utils.intFromHex
 import io.novafoundation.nova.common.utils.singleReplaySharedFlow
+import io.novafoundation.nova.common.utils.startsWith
 import io.novafoundation.nova.common.validation.EmptyValidationSystem
 import io.novafoundation.nova.feature_account_api.data.extrinsic.ExtrinsicService
 import io.novafoundation.nova.feature_account_api.data.mappers.mapChainToUi
@@ -49,7 +51,6 @@ import io.novasama.substrate_sdk_android.runtime.extrinsic.Nonce
 import io.novasama.substrate_sdk_android.runtime.extrinsic.signer.SendableExtrinsic
 import io.novasama.substrate_sdk_android.runtime.extrinsic.signer.SignerPayloadRaw
 import io.novasama.substrate_sdk_android.runtime.extrinsic.signer.fromHex
-import io.novasama.substrate_sdk_android.runtime.extrinsic.signer.fromUtf8
 import io.novasama.substrate_sdk_android.wsrpc.request.runtime.chain.RuntimeVersion
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.Flow
@@ -178,11 +179,7 @@ class PolkadotExternalSignInteractor(
         val accountId = signBytesPayload.address.anyAddressToAccountId()
 
         val signer = resolveWalletSigner()
-        val payload = runCatching {
-            SignerPayloadRaw.fromHex(signBytesPayload.data, accountId)
-        }.getOrElse {
-            SignerPayloadRaw.fromUtf8(signBytesPayload.data, accountId)
-        }
+        val payload = SignerPayloadRaw.fromUnsafeString(signBytesPayload.data, accountId)
 
         val signature = signer.signRaw(payload).asHexString()
         return SignedResult(signature, modifiedTransaction = null)
@@ -244,6 +241,26 @@ class PolkadotExternalSignInteractor(
         )
     }
 
+    private fun SignerPayloadRaw.Companion.fromUnsafeString(data: String, signer: AccountId): SignerPayloadRaw {
+        val unsafeMessage = decodeSigningMessage(data)
+        val safeMessage = protectSigningMessage(unsafeMessage)
+
+        return SignerPayloadRaw(safeMessage, signer)
+    }
+
+    private fun decodeSigningMessage(data: String): ByteArray {
+        return kotlin.runCatching { data.fromHex() }.getOrElse { data.encodeToByteArray() }
+    }
+
+    private fun protectSigningMessage(message: ByteArray): ByteArray {
+        val prefix = "<Bytes>".encodeToByteArray()
+        val suffix = "</Bytes>".encodeToByteArray()
+
+        if (message.startsWith(prefix) && message.endsWith(suffix)) return message
+
+        return prefix + message + suffix
+    }
+
     private suspend fun PolkadotSignPayload.Json.actualMetadataHash(chain: Chain, signer: NovaSigner): ActualMetadataHash {
         // If a dapp haven't declared a permission to modify extrinsic - return whatever metadataHash present in payload
         if (withSignedTransaction != true) {