Validate default homeserver config before loading the app

Implements the process described here: https://github.com/vector-im/riot-web/issues/9290#issuecomment-481966910

The expectation is that later layers (like the react-sdk) will make use of the `validated_discovery_config` option instead of interpreting the config themselves.

We intentionally block the UI from loading here to avoid races between discovery and the app loading.

README.md

@@ -109,25 +109,29 @@ You can configure the app by copying `config.sample.json` to
 
 For a good example, see https://riot.im/develop/config.json.
 
-1. `default_server_name` sets the default server name to use for authentication.
-   This will trigger Riot to ask
-   `https://<server_name>/.well-known/matrix/client` for the homeserver and
-   identity server URLs to use. This is the recommended approach for setting a
-   default server. However, it is also possible to use the following to directly
-   configure each of the URLs:
-   * `default_hs_url` sets the default homeserver URL.
-   * `default_is_url` sets the default identity server URL (this is the server used
-      for verifying third party identifiers like email addresses). If this is blank,
-      registering with an email address, adding an email address to your account,
-      or inviting users via email address will not work.  Matrix identity servers are
-      very simple web services which map third party identifiers (currently only email
-      addresses) to matrix IDs: see http://matrix.org/docs/spec/identity_service/unstable.html
-      for more details.  Currently the only public matrix identity servers are https://matrix.org
-      and https://vector.im.  In the future, identity servers will be decentralised.
-   * Riot will report an error if you accidentally configure both `default_server_name` _and_ `default_hs_url` since it's unclear which should take priority.
+1. `default_server_config` sets the default homeserver and identity server URL for
+   Riot to use. The object is the same as returned by [https://<server_name>/.well-known/matrix/client](https://matrix.org/docs/spec/client_server/latest.html#get-well-known-matrix-client),
+   with added support for a `server_name` under the `m.homeserver` section to display
+   a custom homeserver name. Alternatively, the config can contain a `default_server_name`
+   instead which is where Riot will go to get that same object - see the `.well-known`
+   link above for more information.
+   * *Note*: The URLs can also be individually specified as `default_hs_url` and 
+     `default_is_url`, however these are deprecated. They are maintained for backwards
+     compatibility with older configurations. `default_is_url` is respected only
+     if `default_hs_url` is used.
+   * The identity server is used for verifying third party identifiers like emails
+     and phone numbers. It is not used to store your password or account information.
+     If not provided, the identity server defaults to vector.im unless `disable_identity_server`
+     is set to true in the config. Currently the only two public identity servers
+     are https://matrix.org and https://vector.im, however in future identity servers
+     will be decentralised.
+   * Riot will fail to load if a mix of `default_server_config`, `default_server_name`, or
+     `default_hs_url` is specified. When multiple sources are specified, it is unclear
+     which should take priority and therefore the application cannot continue.
 1. `features`: Lookup of optional features that may be `enable`d, `disable`d, or exposed to the user
    in the `labs` section of settings.  The available optional experimental features vary from
-   release to release.
+   release to release. Some of the available features are described in the Labs Feature section
+   of this README.
 1. `brand`: String to pass to your homeserver when configuring email notifications, to let the
    homeserver know what email template to use when talking to you.
 1. `branding`: Configures various branding and logo details, such as:

config.sample.json

@@ -1,6 +1,14 @@
 {
-    "default_hs_url": "https://matrix.org",
-    "default_is_url": "https://vector.im",
+    "default_server_config": {
+        "m.homeserver": {
+            "base_url": "https://matrix.org",
+            "server_name": "matrix.org"
+        },
+        "m.identity_server": {
+            "base_url": "https://vector.im"
+        }
+    },
+    "disable_identity_server": false,
     "disable_custom_urls": false,
     "disable_guests": false,
     "disable_login_language_selector": false,

src/i18n/strings/en_EN.json

@@ -1,4 +1,7 @@
 {
+    "Unexpected error preparing the app. See console for details.": "Unexpected error preparing the app. See console for details.",
+    "Invalid configuration: can only specify one of default_server_config, default_server_name, or default_hs_url.": "Invalid configuration: can only specify one of default_server_config, default_server_name, or default_hs_url.",
+    "Unexpected error resolving homeserver configuration": "Unexpected error resolving homeserver configuration",
     "Riot Desktop on %(platformName)s": "Riot Desktop on %(platformName)s",
     "Unknown device": "Unknown device",
     "%(appName)s via %(browserName)s on %(osName)s": "%(appName)s via %(browserName)s on %(osName)s",
@@ -15,7 +18,5 @@
     "Need help?": "Need help?",
     "Chat with Riot Bot": "Chat with Riot Bot",
     "Explore rooms": "Explore rooms",
-    "Room Directory": "Room Directory",
-    "Search the room directory": "Search the room directory",
-    "Get started with some tips from Riot Bot!": "Get started with some tips from Riot Bot!"
+    "Room Directory": "Room Directory"
 }

src/vector/index.js

@@ -45,6 +45,8 @@ import VectorConferenceHandler from 'matrix-react-sdk/lib/VectorConferenceHandle
 import Promise from 'bluebird';
 import request from 'browser-request';
 import * as languageHandler from 'matrix-react-sdk/lib/languageHandler';
+import {_t, _td} from 'matrix-react-sdk/lib/languageHandler';
+import {AutoDiscovery} from "matrix-js-sdk/lib/autodiscovery";
 
 import url from 'url';
 
@@ -341,13 +343,15 @@ async function loadApp() {
         const platform = PlatformPeg.get();
         platform.startUpdater();
 
+        // Don't bother loading the app until the config is verified
+        verifyServerConfig().then((newConfig) => {
             const MatrixChat = sdk.getComponent('structures.MatrixChat');
             window.matrixChat = ReactDOM.render(
                 <MatrixChat
                     onNewScreen={onNewScreen}
                     makeRegistrationUrl={makeRegistrationUrl}
                     ConferenceHandler={VectorConferenceHandler}
-                config={configJson}
+                    config={newConfig}
                     realQueryParams={params}
                     startingFragmentQueryParams={fragparts.params}
                     enableGuest={!configJson.disable_guests}
@@ -357,6 +361,19 @@ async function loadApp() {
                 />,
                 document.getElementById('matrixchat'),
             );
+        }).catch(err => {
+            console.error(err);
+
+            const errorMessage = err.translatedMessage
+                || _t("Unexpected error preparing the app. See console for details.");
+
+            // Like the compatibility page, AWOOOOOGA at the user
+            const GenericErrorPage = sdk.getComponent("structures.GenericErrorPage");
+            window.matrixChat = ReactDOM.render(
+                <GenericErrorPage message={errorMessage} />,
+                document.getElementById('matrixchat'),
+            );
+        });
     } else {
         console.error("Browser is missing required features.");
         // take to a different landing page to AWOOOOOGA at the user
@@ -428,4 +445,141 @@ async function loadLanguage() {
     }
 }
 
+async function verifyServerConfig() {
+    console.log("Verifying homeserver configuration");
+
+    // Errors which can be returned by .well-known lookups. If autodiscovery fails for unexpected reasons,
+    // the last thing we want is "missing-translation|en:Your error here". The actual strings are also defined
+    // in the react-sdk, so we don't need them here.
+    const discoveryErrors = [
+        "Invalid homeserver discovery response",
+        "Failed to get autodiscovery configuration from server",
+        "Invalid base_url for m.homeserver",
+        "Homeserver URL does not appear to be a valid Matrix homeserver",
+        "Invalid identity server discovery response",
+        "Invalid base_url for m.identity_server",
+        "Identity server URL does not appear to be a valid identity server",
+        "General failure",
+    ];
+
+    const config = SdkConfig.get();
+    let wkConfig = config['default_server_config']; // overwritten later under some conditions
+    const serverName = config['default_server_name'];
+    const hsUrl = config['default_hs_url'];
+    const isUrl = config['default_is_url'];
+
+    const incompatibleOptions = [wkConfig, serverName, hsUrl].filter(i => !!i);
+    if (incompatibleOptions.length > 1) {
+        throw newTranslatableError(_td(
+            "Invalid configuration: can only specify one of default_server_config, default_server_name, " +
+            "or default_hs_url.",
+        ));
+    }
+
+    if (hsUrl) {
+        console.log("Config uses a default_hs_url - constructing a default_server_config using this information");
+
+        wkConfig = {
+            "m.homeserver": {
+                "base_url": hsUrl,
+            },
+        };
+        if (isUrl) {
+            wkConfig["m.identity_server"] = {
+                "base_url": isUrl,
+            };
+        }
+    }
+
+    let result = null;
+
+    if (wkConfig) {
+        console.log("Config uses a default_server_config - validating object");
+        result = await AutoDiscovery.fromDiscoveryConfig(wkConfig);
+    }
+
+    if (serverName) {
+        console.log("Config uses a default_server_name - doing .well-known lookup");
+        result = await AutoDiscovery.findClientConfig(serverName);
+    }
+
+    if (!result || !result["m.homeserver"]) {
+        // This shouldn't happen without major misconfiguration, so we'll log a bit of information
+        // in the log so we can find this bit of codee but otherwise tell teh user "it broke".
+        console.error("Ended up in a state of not knowing which homeserver to connect to.");
+        throw newTranslatableError(_td("Unexpected error resolving homeserver configuration"));
+    }
+
+    const hsResult = result['m.homeserver'];
+    if (hsResult.state !== AutoDiscovery.SUCCESS) {
+        if (discoveryErrors.indexOf(hsResult.error) !== -1) {
+            throw newTranslatableError(hsResult.error);
+        }
+        throw newTranslatableError(_td("Unexpected error resolving homeserver configuration"));
+    }
+
+    const isResult = result['m.identity_server'];
+    let preferredIdentityUrl = "https://vector.im";
+    if (isResult && isResult.state === AutoDiscovery.SUCCESS) {
+        preferredIdentityUrl = isResult["base_url"];
+    } else if (isResult && isResult.state !== AutoDiscovery.PROMPT) {
+        console.error("Error determining preferred identity server URL:", isResult);
+        throw newTranslatableError(_td("Unexpected error resolving homeserver configuration"));
+    }
+
+    const preferredHomeserverUrl = hsResult["base_url"];
+    let preferredHomeserverName = serverName ? serverName : hsResult["server_name"];
+
+    const url = new URL(preferredHomeserverUrl);
+    if (!preferredHomeserverName) preferredHomeserverName = url.hostname;
+
+    // It should have been set by now, so check it
+    if (!preferredHomeserverName) {
+        console.error("Failed to parse homeserver name from homeserver URL");
+        throw newTranslatableError(_td("Unexpected error resolving homeserver configuration"));
+    }
+
+    const isServerNameDifferentFromUrl = url.hostname !== preferredHomeserverName;
+
+    console.log("Using homeserver config:", {
+        isServerNameDifferentFromUrl,
+        preferredHomeserverName,
+        preferredHomeserverUrl,
+        preferredIdentityUrl,
+    });
+
+    // Build our own discovery result for distribution within the app
+    const configResult = {
+        "m.homeserver": {
+            "base_url": preferredHomeserverUrl,
+            "server_name": preferredHomeserverName,
+            "server_name_different": isServerNameDifferentFromUrl,
+        },
+        "m.identity_server": {
+            "base_url": preferredIdentityUrl,
+            "enabled": !SdkConfig.get()['disable_identity_server'],
+        },
+    };
+
+    // Copy over any other keys that may be of interest
+    for (const key of Object.keys(result)) {
+        if (key === "m.homeserver" || key === "m.identity_server") continue;
+        configResult[key] = JSON.parse(JSON.stringify(result[key])); // deep clone
+    }
+
+    // Add the newly built config to the actual config for use by the app
+    console.log("Updating SdkConfig with validated discovery information");
+    SdkConfig.add({"validated_discovery_config": configResult});
+
+    return SdkConfig.get();
+}
+
+// Helper function to provide English errors in logs, but present translated
+// errors to users.
+function newTranslatableError(message) {
+    const error = new Error(message);
+    error.translatedMessage = _t(message);
+    return error;
+}
+
 loadApp();