Fix / reset cross signing not well supported

CHANGES.md

@@ -26,6 +26,7 @@ Bugfix 🐛:
  - Invalid popup when pressing back (#1635)
  - Simplifies draft management and should fix bunch of draft issues (#952, #683)
  - Very long topic cannot be fully visible (#1957)
+ - Properly detect cross signing keys reset
 
 Translations 🗣:
  -

matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/crypto/DeviceListManager.kt

@@ -359,7 +359,6 @@ internal class DeviceListManager @Inject constructor(private val cryptoStore: IM
                 cryptoStore.storeUserDevices(userId, workingCopy)
             }
 
-            // Handle cross signing keys update
             val masterKey = response.masterKeys?.get(userId)?.toCryptoModel().also {
                 Timber.v("## CRYPTO | CrossSigning : Got keys for $userId : MSK ${it?.unpaddedBase64PublicKey}")
             }

matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/crypto/store/db/RealmCryptoStore.kt

@@ -302,22 +302,42 @@ internal class RealmCryptoStore @Inject constructor(
                             userEntity.crossSigningInfoEntity?.deleteFromRealm()
                             userEntity.crossSigningInfoEntity = null
                         } else {
+                            var shouldResetMyDevicesLocalTrust = false
                             CrossSigningInfoEntity.getOrCreate(realm, userId).let { signingInfo ->
                                 // What should we do if we detect a change of the keys?
                                 val existingMaster = signingInfo.getMasterKey()
                                 if (existingMaster != null && existingMaster.publicKeyBase64 == masterKey.unpaddedBase64PublicKey) {
                                     crossSigningKeysMapper.update(existingMaster, masterKey)
                                 } else {
+                                    Timber.d("## CrossSigning  MSK change for $userId")
                                     val keyEntity = crossSigningKeysMapper.map(masterKey)
                                     signingInfo.setMasterKey(keyEntity)
+                                    if (userId == credentials.userId) {
+                                        shouldResetMyDevicesLocalTrust = true
+                                        // my msk has changed! clear my private key
+                                        // Could we have some race here? e.g I am the one that did change the keys
+                                        // could i get this update to early and clear the private keys?
+                                        // -> initializeCrossSigning is guarding for that by storing all at once
+                                        realm.where<CryptoMetadataEntity>().findFirst()?.apply {
+                                            xSignMasterPrivateKey = null
+                                        }
+                                    }
                                 }
 
                                 val existingSelfSigned = signingInfo.getSelfSignedKey()
                                 if (existingSelfSigned != null && existingSelfSigned.publicKeyBase64 == selfSigningKey.unpaddedBase64PublicKey) {
                                     crossSigningKeysMapper.update(existingSelfSigned, selfSigningKey)
                                 } else {
+                                    Timber.d("## CrossSigning  SSK change for $userId")
                                     val keyEntity = crossSigningKeysMapper.map(selfSigningKey)
                                     signingInfo.setSelfSignedKey(keyEntity)
+                                    if (userId == credentials.userId) {
+                                        shouldResetMyDevicesLocalTrust = true
+                                        // my ssk has changed! clear my private key
+                                        realm.where<CryptoMetadataEntity>().findFirst()?.apply {
+                                            xSignSelfSignedPrivateKey = null
+                                        }
+                                    }
                                 }
 
                                 // Only for me
@@ -326,10 +346,29 @@ internal class RealmCryptoStore @Inject constructor(
                                     if (existingUSK != null && existingUSK.publicKeyBase64 == userSigningKey.unpaddedBase64PublicKey) {
                                         crossSigningKeysMapper.update(existingUSK, userSigningKey)
                                     } else {
+                                        Timber.d("## CrossSigning  USK change for $userId")
                                         val keyEntity = crossSigningKeysMapper.map(userSigningKey)
                                         signingInfo.setUserSignedKey(keyEntity)
+                                        if (userId == credentials.userId) {
+                                            shouldResetMyDevicesLocalTrust = true
+                                            // my usk has changed! clear my private key
+                                            realm.where<CryptoMetadataEntity>().findFirst()?.apply {
+                                                xSignUserPrivateKey = null
+                                            }
+                                        }
                                     }
                                 }
+
+                                // When my cross signing keys are reset, we consider clearing all existing device trust
+                                if (shouldResetMyDevicesLocalTrust) {
+                                    realm.where<UserEntity>()
+                                            .equalTo(UserEntityFields.USER_ID, credentials.userId)
+                                            .findFirst()
+                                            ?.devices?.forEach {
+                                                it?.trustLevelEntity?.crossSignedVerified = false
+                                                it?.trustLevelEntity?.locallyVerified = it.deviceId == credentials.deviceId
+                                            }
+                                }
                                 userEntity.crossSigningInfoEntity = signingInfo
                             }
                         }
@@ -1197,7 +1236,7 @@ internal class RealmCryptoStore @Inject constructor(
                     .findAll()
                     .mapNotNull { entity ->
                         when (entity.type) {
-                            GossipRequestType.KEY -> {
+                            GossipRequestType.KEY    -> {
                                 IncomingRoomKeyRequest(
                                         userId = entity.otherUserId,
                                         deviceId = entity.otherDeviceId,

vector/src/main/java/im/vector/app/features/home/HomeActivity.kt

@@ -138,6 +138,7 @@ class HomeActivity : VectorBaseActivity(), ToolbarConfigurable, UnknownDeviceDet
                 is HomeActivityViewEvents.AskPasswordToInitCrossSigning -> handleAskPasswordToInitCrossSigning(it)
                 is HomeActivityViewEvents.OnNewSession                  -> handleOnNewSession(it)
                 HomeActivityViewEvents.PromptToEnableSessionPush        -> handlePromptToEnablePush()
+                is HomeActivityViewEvents.OnCrossSignedInvalidated      -> handleCrossSigningInvalidated(it)
             }.exhaustive
         }
         homeActivityViewModel.subscribe(this) { renderState(it) }
@@ -182,6 +183,17 @@ class HomeActivity : VectorBaseActivity(), ToolbarConfigurable, UnknownDeviceDet
         }
     }
 
+    private fun handleCrossSigningInvalidated(event: HomeActivityViewEvents.OnCrossSignedInvalidated) {
+        // We need to ask
+        promptSecurityEvent(
+                event.userItem,
+                R.string.crosssigning_verify_this_session,
+                R.string.confirm_your_identity
+        ) {
+            it.navigator.waitSessionVerification(it)
+        }
+    }
+
     private fun handleOnNewSession(event: HomeActivityViewEvents.OnNewSession) {
         // We need to ask
         promptSecurityEvent(

vector/src/main/java/im/vector/app/features/home/HomeActivityViewEvents.kt

@@ -22,5 +22,6 @@ import org.matrix.android.sdk.api.util.MatrixItem
 sealed class HomeActivityViewEvents : VectorViewEvents {
     data class AskPasswordToInitCrossSigning(val userItem: MatrixItem.UserItem?) : HomeActivityViewEvents()
     data class OnNewSession(val userItem: MatrixItem.UserItem?, val waitForIncomingRequest: Boolean = true) : HomeActivityViewEvents()
+    data class OnCrossSignedInvalidated(val userItem: MatrixItem.UserItem?) : HomeActivityViewEvents()
     object PromptToEnableSessionPush : HomeActivityViewEvents()
 }

vector/src/main/java/im/vector/app/features/home/HomeActivityViewModel.kt

@@ -27,6 +27,9 @@ import im.vector.app.core.extensions.exhaustive
 import im.vector.app.core.platform.VectorViewModel
 import im.vector.app.features.login.ReAuthHelper
 import im.vector.app.features.settings.VectorPreferences
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.launch
 import org.matrix.android.sdk.api.MatrixCallback
 import org.matrix.android.sdk.api.NoOpMatrixCallback
 import org.matrix.android.sdk.api.pushrules.RuleIds
@@ -38,9 +41,7 @@ import org.matrix.android.sdk.internal.crypto.model.CryptoDeviceInfo
 import org.matrix.android.sdk.internal.crypto.model.MXUsersDevicesMap
 import org.matrix.android.sdk.internal.crypto.model.rest.UserPasswordAuth
 import org.matrix.android.sdk.rx.asObservable
-import kotlinx.coroutines.Dispatchers
+import org.matrix.android.sdk.rx.rx
-import kotlinx.coroutines.delay
-import kotlinx.coroutines.launch
 import timber.log.Timber
 
 class HomeActivityViewModel @AssistedInject constructor(
@@ -67,11 +68,39 @@ class HomeActivityViewModel @AssistedInject constructor(
     }
 
     private var checkBootstrap = false
+    private var onceTrusted = false
 
     init {
         observeInitialSync()
         mayBeInitializeCrossSigning()
         checkSessionPushIsOn()
+        observeCrossSigningReset()
+    }
+
+    private fun observeCrossSigningReset() {
+        val safeActiveSession = activeSessionHolder.getSafeActiveSession()
+        val crossSigningService = safeActiveSession
+                ?.cryptoService()
+                ?.crossSigningService()
+        onceTrusted = crossSigningService
+                ?.allPrivateKeysKnown() ?: false
+
+        safeActiveSession
+                ?.rx()
+                ?.liveCrossSigningInfo(safeActiveSession.myUserId)
+                ?.subscribe {
+                    val isVerified = it.getOrNull()?.isTrusted() ?: false
+                    if (!isVerified && onceTrusted) {
+                        // cross signing keys have been reset
+                        // Tigger a popup to re-verify
+                        _viewEvents.post(
+                                HomeActivityViewEvents.OnCrossSignedInvalidated(
+                                        safeActiveSession.getUser(safeActiveSession.myUserId)?.toMatrixItem()
+                                )
+                        )
+                    }
+                    onceTrusted = isVerified
+                }?.disposeOnClear()
     }
 
     private fun observeInitialSync() {

vector/src/main/java/im/vector/app/features/home/UnknownDeviceDetectorSharedViewModel.kt

@@ -30,6 +30,8 @@ import im.vector.app.core.platform.EmptyViewEvents
 import im.vector.app.core.platform.VectorViewModel
 import im.vector.app.core.platform.VectorViewModelAction
 import im.vector.app.features.settings.VectorPreferences
+import io.reactivex.Observable
+import io.reactivex.functions.Function3
 import org.matrix.android.sdk.api.NoOpMatrixCallback
 import org.matrix.android.sdk.api.extensions.orFalse
 import org.matrix.android.sdk.api.session.Session
@@ -39,8 +41,6 @@ import org.matrix.android.sdk.api.util.toMatrixItem
 import org.matrix.android.sdk.internal.crypto.model.CryptoDeviceInfo
 import org.matrix.android.sdk.internal.crypto.model.rest.DeviceInfo
 import org.matrix.android.sdk.internal.crypto.store.PrivateKeysInfo
-import io.reactivex.Observable
-import io.reactivex.functions.Function3
 import org.matrix.android.sdk.rx.rx
 import timber.log.Timber
 import java.util.concurrent.TimeUnit