feat: Integrate service messages (#48)

* feat: Integrate service messages

Each parcel encapsulates exactly one Relaynet _service message_ encrypted. This fixes #42.

The following changes were also necessary:

- Drop `Message.payload`. Its equivalent in a service message is called _content_.
  - `IncomingMessage.content` supersedes the old `Message.payload`.
  - `OutgoingMessage` doesn't have an equivalent to the old `.payload`
- Capture the service message _type_ in the `Message`s. This type is to be used by app developers to determine how to process the `content`; for example, something like `image/png` could be rendered on screen whilst something like `application/json; type=Tweet` could be JSON-deserialised and verified against a schema.
  - `OutgoingMessage.build()` now requires the `type`.
  - `IncomingMessage.type` exposes the `type`.
- Promote the identity certificate from the children of `ThirdPartyEndpoint` to the parent class. This is needed to encrypt messages regardless of whether the endpoint is private or public.

* fix typo

* remove redundant code

lib/build.gradle

@@ -60,7 +60,7 @@ dependencies {
   implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:$kotlinCoroutinesVersion"
 
   // Relaynet
-  api 'tech.relaycorp:relaynet:[1.47.0,2.0.0)'
+  api 'tech.relaycorp:relaynet:[1.47.1,2.0.0)'
   implementation 'tech.relaycorp:poweb:1.5.15'
 
   // Security

lib/src/main/java/tech/relaycorp/relaydroid/endpoint/ThirdPartyEndpoint.kt

@@ -3,11 +3,13 @@ package tech.relaycorp.relaydroid.endpoint
 import tech.relaycorp.relaydroid.Storage
 import tech.relaycorp.relaydroid.storage.persistence.PersistenceException
 import tech.relaycorp.relaynet.RelaynetException
+import tech.relaycorp.relaynet.messages.payloads.ServiceMessage
 import tech.relaycorp.relaynet.wrappers.x509.Certificate
 import tech.relaycorp.relaynet.wrappers.x509.CertificateException
 
 public sealed class ThirdPartyEndpoint(
-    override val address: String
+    override val address: String,
+    public val identityCertificate: Certificate
 ) : Endpoint {
 
     public val thirdPartyAddress: String get() = address
@@ -26,8 +28,8 @@ public class PrivateThirdPartyEndpoint(
     public val firstPartyAddress: String,
     thirdPartyAddress: String,
     public val authorization: Certificate,
-    public val identity: Certificate
-) : ThirdPartyEndpoint(thirdPartyAddress) {
+    identityCertificate: Certificate
+) : ThirdPartyEndpoint(thirdPartyAddress, identityCertificate) {
 
     public companion object {
 
@@ -76,8 +78,8 @@ public class PrivateThirdPartyEndpoint(
 
 public class PublicThirdPartyEndpoint(
     thirdPartyAddress: String,
-    public val certificate: Certificate
-) : ThirdPartyEndpoint(thirdPartyAddress) {
+    identityCertificate: Certificate
+) : ThirdPartyEndpoint(thirdPartyAddress, identityCertificate) {
 
     public companion object {
         @Throws(PersistenceException::class)

lib/src/main/java/tech/relaycorp/relaydroid/messaging/IncomingMessage.kt

@@ -7,24 +7,29 @@ import tech.relaycorp.relaydroid.endpoint.UnknownThirdPartyEndpointException
 import tech.relaycorp.relaydroid.storage.persistence.PersistenceException
 import tech.relaycorp.relaynet.messages.Parcel
 import java.time.ZonedDateTime
+import tech.relaycorp.relaynet.messages.InvalidMessageException
+import tech.relaycorp.relaynet.wrappers.cms.EnvelopedDataException
 
 public class IncomingMessage internal constructor(
     id: MessageId,
-    payload: ByteArray,
+    public val type: String,
+    public val content: ByteArray,
     public val senderEndpoint: ThirdPartyEndpoint,
     public val recipientEndpoint: FirstPartyEndpoint,
     creationDate: ZonedDateTime,
     expiryDate: ZonedDateTime,
     public val ack: suspend () -> Unit
 ) : Message(
-    id, payload, senderEndpoint, recipientEndpoint, creationDate, expiryDate
+    id, senderEndpoint, recipientEndpoint, creationDate, expiryDate
 ) {
 
     internal companion object {
         @Throws(
             UnknownFirstPartyEndpointException::class,
             UnknownThirdPartyEndpointException::class,
-            PersistenceException::class
+            PersistenceException::class,
+            EnvelopedDataException::class,
+            InvalidMessageException::class
         )
         internal suspend fun build(parcel: Parcel, ack: suspend () -> Unit): IncomingMessage {
             val recipientEndpoint = FirstPartyEndpoint.load(parcel.recipientAddress)
@@ -41,9 +46,11 @@ public class IncomingMessage internal constructor(
                     "for first party endpoint ${parcel.recipientAddress}"
             )
 
+            val serviceMessage = parcel.unwrapPayload(recipientEndpoint.keyPair.private)
             return IncomingMessage(
                 id = MessageId(parcel.id),
-                payload = parcel.payload,
+                type = serviceMessage.type,
+                content = serviceMessage.content,
                 senderEndpoint = sender,
                 recipientEndpoint = recipientEndpoint,
                 creationDate = parcel.creationDate,

lib/src/main/java/tech/relaycorp/relaydroid/messaging/Message.kt

@@ -6,7 +6,6 @@ import java.time.ZonedDateTime
 
 public abstract class Message(
     public val id: MessageId,
-    public val payload: ByteArray,
     senderEndpoint: Endpoint,
     recipientEndpoint: Endpoint,
     public val creationDate: ZonedDateTime = ZonedDateTime.now(),

lib/src/main/java/tech/relaycorp/relaydroid/messaging/OutgoingMessage.kt

@@ -10,35 +10,36 @@ import tech.relaycorp.relaynet.messages.Parcel
 import tech.relaycorp.relaynet.ramf.RAMFException
 import tech.relaycorp.relaynet.wrappers.x509.Certificate
 import java.time.ZonedDateTime
+import tech.relaycorp.relaynet.messages.payloads.ServiceMessage
 
 public class OutgoingMessage
 private constructor(
-    payload: ByteArray,
     public val senderEndpoint: FirstPartyEndpoint,
     public val recipientEndpoint: ThirdPartyEndpoint,
     creationDate: ZonedDateTime = ZonedDateTime.now(),
     expiryDate: ZonedDateTime = maxExpiryDate(),
     id: MessageId = MessageId.generate()
 ) : Message(
-    id, payload, senderEndpoint, recipientEndpoint, creationDate, expiryDate
+    id, senderEndpoint, recipientEndpoint, creationDate, expiryDate
 ) {
 
     internal lateinit var parcel: Parcel
         private set
 
     public companion object {
         public suspend fun build(
-            payload: ByteArray,
+            type: String,
+            content: ByteArray,
             senderEndpoint: FirstPartyEndpoint,
             recipientEndpoint: ThirdPartyEndpoint,
             creationDate: ZonedDateTime = ZonedDateTime.now(),
             expiryDate: ZonedDateTime = maxExpiryDate(),
             id: MessageId = MessageId.generate()
         ): OutgoingMessage {
             val message = OutgoingMessage(
-                payload, senderEndpoint, recipientEndpoint, creationDate, expiryDate, id
+                senderEndpoint, recipientEndpoint, creationDate, expiryDate, id
             )
-            message.parcel = message.buildParcel()
+            message.parcel = message.buildParcel(type, content)
             try {
                 message.parcel.validate(null)
             } catch (exp: RAMFException) {
@@ -48,19 +49,25 @@ private constructor(
         }
     }
 
-    private suspend fun buildParcel() = Parcel(
-        recipientAddress = if (recipientEndpoint is PublicThirdPartyEndpoint) {
-            "https://" + recipientEndpoint.address
-        } else {
-            recipientEndpoint.address
-        },
-        payload = payload,
-        senderCertificate = getSenderCertificate(),
-        messageId = id.value,
-        creationDate = creationDate,
-        ttl = ttl,
-        senderCertificateChain = getSenderCertificateChain()
-    )
+    private suspend fun buildParcel(
+        serviceMessageType: String,
+        serviceMessageContent: ByteArray
+    ): Parcel {
+        val serviceMessage = ServiceMessage(serviceMessageType, serviceMessageContent)
+        return Parcel(
+            recipientAddress = if (recipientEndpoint is PublicThirdPartyEndpoint) {
+                "https://" + recipientEndpoint.address
+            } else {
+                recipientEndpoint.address
+            },
+            payload = serviceMessage.encrypt(recipientEndpoint.identityCertificate),
+            senderCertificate = getSenderCertificate(),
+            messageId = id.value,
+            creationDate = creationDate,
+            ttl = ttl,
+            senderCertificateChain = getSenderCertificateChain()
+        )
+    }
 
     private suspend fun getSenderCertificate() =
         when (recipientEndpoint) {

lib/src/main/java/tech/relaycorp/relaydroid/messaging/ReceiveMessages.kt

@@ -1,5 +1,6 @@
 package tech.relaycorp.relaydroid.messaging
 
+import java.util.logging.Level
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.asFlow
 import kotlinx.coroutines.flow.flatMapLatest
@@ -15,12 +16,13 @@ import tech.relaycorp.relaydroid.storage.persistence.PersistenceException
 import tech.relaycorp.relaynet.bindings.pdc.ClientBindingException
 import tech.relaycorp.relaynet.bindings.pdc.NonceSignerException
 import tech.relaycorp.relaynet.bindings.pdc.PDCClient
+import tech.relaycorp.relaynet.bindings.pdc.ParcelCollection
 import tech.relaycorp.relaynet.bindings.pdc.ServerException
 import tech.relaycorp.relaynet.bindings.pdc.Signer
 import tech.relaycorp.relaynet.bindings.pdc.StreamingMode
 import tech.relaycorp.relaynet.messages.InvalidMessageException
 import tech.relaycorp.relaynet.ramf.RAMFException
-import java.util.logging.Level
+import tech.relaycorp.relaynet.wrappers.cms.EnvelopedDataException
 
 internal class ReceiveMessages(
     private val pdcClientBuilder: () -> PDCClient = { PoWebClient.initLocal(Relaynet.POWEB_PORT) }
@@ -69,27 +71,40 @@ internal class ReceiveMessages(
                 val parcel = try {
                     parcelCollection.deserializeAndValidateParcel()
                 } catch (exp: RAMFException) {
-                    logger.log(Level.WARNING, "Malformed incoming parcel", exp)
-                    parcelCollection.ack()
+                    parcelCollection.disregard("Malformed incoming parcel", exp)
                     return@mapNotNull null
                 } catch (exp: InvalidMessageException) {
-                    logger.log(Level.WARNING, "Invalid incoming parcel", exp)
-                    parcelCollection.ack()
+                    parcelCollection.disregard("Invalid incoming parcel", exp)
                     return@mapNotNull null
                 }
                 try {
                     IncomingMessage.build(parcel) { parcelCollection.ack() }
                 } catch (exp: UnknownFirstPartyEndpointException) {
-                    logger.log(Level.WARNING, "Incoming parcel with invalid recipient", exp)
-                    parcelCollection.ack()
+                    parcelCollection.disregard("Incoming parcel with invalid recipient", exp)
                     return@mapNotNull null
                 } catch (exp: UnknownFirstPartyEndpointException) {
-                    logger.log(Level.WARNING, "Incoming parcel issues with invalid sender", exp)
-                    parcelCollection.ack()
+                    parcelCollection.disregard("Incoming parcel issues with invalid sender", exp)
+                    return@mapNotNull null
+                } catch (exp: EnvelopedDataException) {
+                    parcelCollection.disregard(
+                        "Failed to decrypt parcel; sender might have used wrong key",
+                        exp
+                    )
+                    return@mapNotNull null
+                } catch (exp: InvalidMessageException) {
+                    parcelCollection.disregard(
+                        "Incoming parcel did not encapsulate a valid service message",
+                        exp
+                    )
                     return@mapNotNull null
                 }
             }
 }
 
+private suspend fun ParcelCollection.disregard(reason: String, exc: Throwable) {
+    logger.log(Level.WARNING, reason, exc)
+    ack()
+}
+
 public class ReceiveMessagesException(message: String, throwable: Throwable? = null)
     : GatewayException(message, throwable)

lib/src/test/java/tech/relaycorp/relaydroid/endpoint/PrivateThirdPartyEndpointTest.kt

@@ -43,7 +43,7 @@ internal class PrivateThirdPartyEndpointTest {
             assertEquals(firstAddress, firstPartyAddress)
             assertEquals(thirdAddress, address)
             assertEquals(PDACertPath.PRIVATE_ENDPOINT, authorization)
-            assertEquals(PDACertPath.PRIVATE_ENDPOINT, identity)
+            assertEquals(PDACertPath.PRIVATE_ENDPOINT, identityCertificate)
         }
 
         verify(storage.thirdPartyAuthorization).get("${firstAddress}_$thirdAddress")
@@ -93,7 +93,7 @@ internal class PrivateThirdPartyEndpointTest {
         )
         assertEquals(
             PDACertPath.PRIVATE_ENDPOINT,
-            endpoint.identity
+            endpoint.identityCertificate
         )
 
         verify(storage.identityCertificate).get(firstPartyAddress)

lib/src/test/java/tech/relaycorp/relaydroid/endpoint/PublicThirdPartyEndpointTest.kt

@@ -34,7 +34,7 @@ internal class PublicThirdPartyEndpointTest {
 
         with(PublicThirdPartyEndpoint.load(address)!!) {
             assertEquals(address, this.address)
-            assertEquals(PDACertPath.PUBLIC_GW, certificate)
+            assertEquals(PDACertPath.PUBLIC_GW, identityCertificate)
         }
     }
 
@@ -49,7 +49,7 @@ internal class PublicThirdPartyEndpointTest {
     fun import_successful() = runBlockingTest {
         with(PublicThirdPartyEndpoint.import(PDACertPath.PUBLIC_GW)) {
             assertEquals(address, this.address)
-            assertEquals(PDACertPath.PUBLIC_GW, certificate)
+            assertEquals(PDACertPath.PUBLIC_GW, identityCertificate)
         }
 
         verify(storage.publicThirdPartyCertificate).set(

lib/src/test/java/tech/relaycorp/relaydroid/messaging/IncomingMessageTest.kt

@@ -16,6 +16,7 @@ import tech.relaycorp.relaynet.messages.Parcel
 import tech.relaycorp.relaynet.testing.pki.KeyPairSet
 import tech.relaycorp.relaynet.testing.pki.PDACertPath
 import java.util.UUID
+import tech.relaycorp.relaynet.messages.payloads.ServiceMessage
 
 internal class IncomingMessageTest {
 
@@ -35,18 +36,20 @@ internal class IncomingMessageTest {
 
     @Test
     fun buildFromParcel() = runBlockingTest {
+        val serviceMessage = ServiceMessage("the type", "the content".toByteArray())
         val parcel = Parcel(
             recipientAddress = UUID.randomUUID().toString(),
-            payload = "1234".toByteArray(),
-            senderCertificate = PDACertPath.PRIVATE_ENDPOINT
+            payload = serviceMessage.encrypt(PDACertPath.PRIVATE_ENDPOINT),
+            senderCertificate = PDACertPath.PDA
         )
 
         val message = IncomingMessage.build(parcel) {}
 
         verify(Relaynet.storage.identityCertificate).get(eq(parcel.recipientAddress))
 
         assertEquals(PDACertPath.PRIVATE_ENDPOINT, message.recipientEndpoint.identityCertificate)
-        assertArrayEquals(parcel.payload, message.payload)
+        assertEquals(serviceMessage.type, message.type)
+        assertArrayEquals(serviceMessage.content, message.content)
         assertEquals(parcel.id, message.id.value)
         assertSameDateTime(parcel.creationDate, message.creationDate)
         assertSameDateTime(parcel.expiryDate, message.expiryDate)

lib/src/test/java/tech/relaycorp/relaydroid/messaging/MessageTest.kt

@@ -18,6 +18,7 @@ internal class MessageTest {
     fun ttl() = runBlockingTest {
         val creationDate = ZonedDateTime.now()
         val message = OutgoingMessage.build(
+            "the type",
             Random.Default.nextBytes(10),
             senderEndpoint = senderEndpoint,
             recipientEndpoint = recipientEndpoint,

lib/src/test/java/tech/relaycorp/relaydroid/messaging/OutgoingMessageTest.kt

@@ -13,12 +13,14 @@ import tech.relaycorp.relaynet.messages.InvalidMessageException
 import tech.relaycorp.relaynet.ramf.RecipientAddressType
 import tech.relaycorp.relaynet.testing.pki.PDACertPath
 import java.time.ZonedDateTime
+import tech.relaycorp.relaynet.testing.pki.KeyPairSet
 
 internal class OutgoingMessageTest {
 
     @Test(expected = InvalidMessageException::class)
     internal fun buildInvalidMessage() = runBlockingTest {
         OutgoingMessage.build(
+            "the type",
             ByteArray(0),
             FirstPartyEndpointFactory.build(),
             PublicThirdPartyEndpoint("example.org", PDACertPath.PUBLIC_GW),
@@ -27,17 +29,26 @@ internal class OutgoingMessageTest {
     }
 
     @Test
-    internal fun buildForPublicRecipient_checkBaseValues() = runBlockingTest {
+    fun buildForPublicRecipient_checkBaseValues() = runBlockingTest {
         val message = MessageFactory.buildOutgoing(RecipientAddressType.PUBLIC)
         val parcel = message.parcel
 
         assertEquals("https://" + message.recipientEndpoint.address, parcel.recipientAddress)
-        assertArrayEquals(message.payload, parcel.payload)
         assertEquals(message.id.value, parcel.id)
         assertSameDateTime(message.creationDate, parcel.creationDate)
         assertEquals(message.ttl, parcel.ttl)
     }
 
+    @Test
+    fun buildForPublicRecipient_checkServiceMessage() = runBlockingTest {
+        val message = MessageFactory.buildOutgoing(RecipientAddressType.PUBLIC)
+        val parcel = message.parcel
+
+        val serviceMessageDecrypted = parcel.unwrapPayload(KeyPairSet.PUBLIC_GW.private)
+        assertEquals(MessageFactory.serviceMessage.type, serviceMessageDecrypted.type)
+        assertArrayEquals(MessageFactory.serviceMessage.content, serviceMessageDecrypted.content)
+    }
+
     @Test
     internal fun buildForPublicRecipient_checkSenderCertificate() = runBlockingTest {
         val message = MessageFactory.buildOutgoing(RecipientAddressType.PUBLIC)