Use correct URL for SSO connection (#1178)

CHANGES.md

@@ -43,6 +43,7 @@ Bugfix 🐛:
  - RiotX now uses as many threads as it needs to do work and send messages (#1221)
  - Fix issue with media path (#1227)
  - Add user to direct chat by user id (#1065)
+ - Use correct URL for SSO connection (#1178)
 
 Translations 🗣:
  -

matrix-sdk-android/src/main/java/im/vector/matrix/android/api/auth/Constants.kt

@@ -27,3 +27,11 @@ const val LOGIN_FALLBACK_PATH = "/_matrix/static/client/login/"
  * Not documented
  */
 const val REGISTER_FALLBACK_PATH = "/_matrix/static/client/register/"
+
+/**
+ * Path to use when the client want to connect using SSO
+ * Ref: https://matrix.org/docs/spec/client_server/latest#sso-client-login
+ */
+const val SSO_FALLBACK_PATH = "/_matrix/client/r0/login/sso/redirect"
+
+const val SSO_REDIRECT_URL_PARAM = "redirectUrl"

vector/src/main/java/im/vector/riotx/features/login/LoginWebFragment.kt

@@ -33,9 +33,12 @@ import androidx.appcompat.app.AlertDialog
 import com.airbnb.mvrx.activityViewModel
 import im.vector.matrix.android.api.auth.LOGIN_FALLBACK_PATH
 import im.vector.matrix.android.api.auth.REGISTER_FALLBACK_PATH
+import im.vector.matrix.android.api.auth.SSO_FALLBACK_PATH
+import im.vector.matrix.android.api.auth.SSO_REDIRECT_URL_PARAM
 import im.vector.matrix.android.api.auth.data.Credentials
 import im.vector.matrix.android.internal.di.MoshiProvider
 import im.vector.riotx.R
+import im.vector.riotx.core.extensions.appendParamToUrl
 import im.vector.riotx.core.utils.AssetReader
 import im.vector.riotx.features.signout.soft.SoftLogoutAction
 import im.vector.riotx.features.signout.soft.SoftLogoutViewModel
@@ -125,10 +128,20 @@ class LoginWebFragment @Inject constructor(
         val url = buildString {
             append(state.homeServerUrl?.trim { it == '/' })
             if (state.signMode == SignMode.SignIn) {
-                append(LOGIN_FALLBACK_PATH)
+                if (state.loginMode == LoginMode.Sso) {
+                    append(SSO_FALLBACK_PATH)
+                    // We do not want to deal with the result, so let the fallback login page to handle it for us
+                    appendParamToUrl(SSO_REDIRECT_URL_PARAM,
+                            buildString {
+                                append(state.homeServerUrl?.trim { it == '/' })
+                                append(LOGIN_FALLBACK_PATH)
+                            })
+                } else {
+                    append(LOGIN_FALLBACK_PATH)
+                }
                 state.deviceId?.takeIf { it.isNotBlank() }?.let {
                     // But https://github.com/matrix-org/synapse/issues/5755
-                    append("?device_id=$it")
+                    appendParamToUrl("device_id", it)
                 }
             } else {
                 // MODE_REGISTER