Allow users to trust self-signed certificates (#160)

* Implement CERT-Store

* Trust user-added certificates

* Improve code readability

* Implement saving self-signed certs to storage

* Create interface for TrustedCertificatesStore

* Remove unused code

* Make datasource implementation internal

* Bump app version to 29 (0.4.0)

---------

Co-authored-by: fz72 <fz72@gmx.de>

app/build.gradle.kts

@@ -16,8 +16,8 @@ plugins {
 android {
     defaultConfig {
         applicationId = "gq.kirmanak.mealient"
-        versionCode = 28
-        versionName = "0.3.13"
+        versionCode = 29
+        versionName = "0.4.0"
         testInstrumentationRunner = "gq.kirmanak.mealient.MealientTestRunner"
         testInstrumentationRunnerArguments += mapOf("clearPackageData" to "true")
         resourceConfigurations += listOf("en", "es", "ru", "fr", "nl", "pt", "de")

app/src/main/java/gq/kirmanak/mealient/ui/baseurl/BaseURLFragment.kt

@@ -2,6 +2,7 @@ package gq.kirmanak.mealient.ui.baseurl
 
 import android.os.Bundle
 import android.view.View
+import androidx.appcompat.app.AlertDialog
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.activityViewModels
 import androidx.fragment.app.viewModels
@@ -11,13 +12,16 @@ import by.kirich1409.viewbindingdelegate.viewBinding
 import dagger.hilt.android.AndroidEntryPoint
 import gq.kirmanak.mealient.R
 import gq.kirmanak.mealient.databinding.FragmentBaseUrlBinding
+import gq.kirmanak.mealient.datasource.CertificateCombinedException
 import gq.kirmanak.mealient.datasource.NetworkError
 import gq.kirmanak.mealient.extensions.checkIfInputIsEmpty
+import gq.kirmanak.mealient.extensions.collectWhenResumed
 import gq.kirmanak.mealient.logging.Logger
 import gq.kirmanak.mealient.ui.CheckableMenuItem
 import gq.kirmanak.mealient.ui.OperationUiState
 import gq.kirmanak.mealient.ui.activity.MainActivityViewModel
 import gq.kirmanak.mealient.ui.baseurl.BaseURLFragmentDirections.Companion.actionBaseURLFragmentToRecipesListFragment
+import java.security.cert.X509Certificate
 import javax.inject.Inject
 
 @AndroidEntryPoint
@@ -36,6 +40,7 @@ class BaseURLFragment : Fragment(R.layout.fragment_base_url) {
         logger.v { "onViewCreated() called with: view = $view, savedInstanceState = $savedInstanceState" }
         binding.button.setOnClickListener(::onProceedClick)
         viewModel.uiState.observe(viewLifecycleOwner, ::onUiStateChange)
+        collectWhenResumed(viewModel.invalidCertificatesFlow, ::onInvalidCertificate)
         activityViewModel.updateUiState {
             it.copy(
                 navigationVisible = !args.isOnboarding,
@@ -45,8 +50,35 @@ class BaseURLFragment : Fragment(R.layout.fragment_base_url) {
         }
     }
 
+    private fun onInvalidCertificate(certificate: X509Certificate) {
+        logger.v { "onInvalidCertificate() called with: certificate = $certificate" }
+        val dialogMessage = getString(
+            R.string.fragment_base_url_invalid_certificate_message,
+            certificate.issuerDN.toString(),
+            certificate.subjectDN.toString(),
+            certificate.notBefore.toString(),
+            certificate.notAfter.toString(),
+        )
+        val dialog = AlertDialog.Builder(requireContext())
+            .setTitle(R.string.fragment_base_url_invalid_certificate_title)
+            .setMessage(dialogMessage)
+            .setPositiveButton(R.string.fragment_base_url_invalid_certificate_accept) { _, _ ->
+                viewModel.acceptInvalidCertificate(certificate)
+                saveEnteredUrl()
+            }.setNegativeButton(R.string.fragment_base_url_invalid_certificate_deny) { _, _ ->
+                // Do nothing, let the user enter another address or try again
+            }
+            .create()
+        dialog.show()
+    }
+
     private fun onProceedClick(view: View) {
         logger.v { "onProceedClick() called with: view = $view" }
+        saveEnteredUrl()
+    }
+
+    private fun saveEnteredUrl() {
+        logger.v { "saveEnteredUrl() called" }
         val url = binding.urlInput.checkIfInputIsEmpty(
             inputLayout = binding.urlInputLayout,
             lifecycleOwner = viewLifecycleOwner,
@@ -69,6 +101,8 @@ class BaseURLFragment : Fragment(R.layout.fragment_base_url) {
                 val cause = exception.cause?.message ?: exception.message
                 getString(R.string.fragment_base_url_malformed_url, cause)
             }
+
+            is CertificateCombinedException -> getString(R.string.fragment_base_url_invalid_certificate_title)
             null -> null
             else -> getString(R.string.fragment_base_url_unknown_error)
         }

app/src/main/java/gq/kirmanak/mealient/ui/baseurl/BaseURLViewModel.kt

@@ -8,11 +8,16 @@ import dagger.hilt.android.lifecycle.HiltViewModel
 import gq.kirmanak.mealient.data.auth.AuthRepo
 import gq.kirmanak.mealient.data.baseurl.ServerInfoRepo
 import gq.kirmanak.mealient.data.recipes.RecipeRepo
+import gq.kirmanak.mealient.datasource.CertificateCombinedException
 import gq.kirmanak.mealient.datasource.NetworkError
+import gq.kirmanak.mealient.datasource.TrustedCertificatesStore
+import gq.kirmanak.mealient.datasource.findCauseAsInstanceOf
 import gq.kirmanak.mealient.logging.Logger
-import gq.kirmanak.mealient.shopping_lists.repo.ShoppingListsRepo
 import gq.kirmanak.mealient.ui.OperationUiState
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.flow.receiveAsFlow
 import kotlinx.coroutines.launch
+import java.security.cert.X509Certificate
 import javax.inject.Inject
 
 @HiltViewModel
@@ -21,12 +26,15 @@ class BaseURLViewModel @Inject constructor(
     private val authRepo: AuthRepo,
     private val recipeRepo: RecipeRepo,
     private val logger: Logger,
-    private val shoppingListsRepo: ShoppingListsRepo,
+    private val trustedCertificatesStore: TrustedCertificatesStore,
 ) : ViewModel() {
 
     private val _uiState = MutableLiveData<OperationUiState<Unit>>(OperationUiState.Initial())
     val uiState: LiveData<OperationUiState<Unit>> get() = _uiState
 
+    private val invalidCertificatesChannel = Channel<X509Certificate>(Channel.UNLIMITED)
+    val invalidCertificatesFlow = invalidCertificatesChannel.receiveAsFlow()
+
     fun saveBaseUrl(baseURL: String) {
         logger.v { "saveBaseUrl() called with: baseURL = $baseURL" }
         _uiState.value = OperationUiState.Progress()
@@ -49,7 +57,11 @@ class BaseURLViewModel @Inject constructor(
 
         val result: Result<Unit> = serverInfoRepo.tryBaseURL(url).recoverCatching {
             logger.e(it) { "checkBaseURL: trying to recover, had prefix = $hasPrefix" }
-            if (hasPrefix || it is NetworkError.NotMealie) {
+            val certificateError = it.findCauseAsInstanceOf<CertificateCombinedException>()
+            if (certificateError != null) {
+                invalidCertificatesChannel.send(certificateError.serverCert)
+                throw certificateError
+            } else if (hasPrefix || it is NetworkError.NotMealie) {
                 throw it
             } else {
                 val unencryptedUrl = url.replace("https", "http")
@@ -66,4 +78,8 @@ class BaseURLViewModel @Inject constructor(
         _uiState.value = OperationUiState.fromResult(result)
     }
 
+    fun acceptInvalidCertificate(certificate: X509Certificate) {
+        logger.v { "acceptInvalidCertificate() called with: certificate = $certificate" }
+        trustedCertificatesStore.addTrustedCertificate(certificate)
+    }
 }

app/src/main/res/values/strings.xml

@@ -17,6 +17,10 @@
 	<string name="fragment_base_url_malformed_url">Check URL format: %s</string>
 	<string name="fragment_base_url_save">Proceed</string>
 	<string name="fragment_base_url_unknown_error" translatable="false">@string/fragment_authentication_unknown_error</string>
+	<string name="fragment_base_url_invalid_certificate_title">The identity of the server could not be verified</string>
+	<string name="fragment_base_url_invalid_certificate_message">Do you trust this certificate?\n\nCertificate Information:\nIssuer: %1$s\nSubject: %2$s\nValid From: %3$s\nValid Until: %4$s</string>
+	<string name="fragment_base_url_invalid_certificate_accept">Trust</string>
+	<string name="fragment_base_url_invalid_certificate_deny">No</string>
 	<string name="menu_navigation_drawer_login">Login</string>
 	<string name="fragment_disclaimer_button_okay">Okay</string>
 	<string name="view_holder_recipe_instructions_step">Step: %d</string>

app/src/test/java/gq/kirmanak/mealient/ui/baseurl/BaseURLViewModelTest.kt

@@ -5,7 +5,7 @@ import gq.kirmanak.mealient.data.auth.AuthRepo
 import gq.kirmanak.mealient.data.baseurl.ServerInfoRepo
 import gq.kirmanak.mealient.data.recipes.RecipeRepo
 import gq.kirmanak.mealient.datasource.NetworkError
-import gq.kirmanak.mealient.shopping_lists.repo.ShoppingListsRepo
+import gq.kirmanak.mealient.datasource.TrustedCertificatesStore
 import gq.kirmanak.mealient.test.AuthImplTestData.TEST_BASE_URL
 import gq.kirmanak.mealient.test.BaseUnitTest
 import gq.kirmanak.mealient.ui.OperationUiState
@@ -33,7 +33,7 @@ class BaseURLViewModelTest : BaseUnitTest() {
     lateinit var recipeRepo: RecipeRepo
 
     @MockK(relaxUnitFun = true)
-    lateinit var shoppingListsRepo: ShoppingListsRepo
+    lateinit var trustedCertificatesStore: TrustedCertificatesStore
 
     lateinit var subject: BaseURLViewModel
 
@@ -45,7 +45,7 @@ class BaseURLViewModelTest : BaseUnitTest() {
             authRepo = authRepo,
             recipeRepo = recipeRepo,
             logger = logger,
-            shoppingListsRepo = shoppingListsRepo,
+            trustedCertificatesStore = trustedCertificatesStore,
         )
     }