element-ios/Riot/Modules/Home/Fallback/AuthFallBackViewController.m

/*
 Copyright 2019 New Vector Ltd

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

 http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */

#import "AuthFallBackViewController.h"
#import "Riot-Swift.h"

// Generic method to make a bridge between JS and the WKWebView
NSString *FallBackViewControllerJavascriptSendObjectMessage = @"window.sendObjectMessage = function(parameters) {   \
    var iframe = document.createElement('iframe');                              \
    iframe.setAttribute('src', 'js:' + JSON.stringify(parameters));             \
    \
    document.documentElement.appendChild(iframe);                               \
    iframe.parentNode.removeChild(iframe);                                      \
    iframe = null;                                                              \
};";

// The function the fallback page calls when the registration is complete
NSString *FallBackViewControllerJavascriptOnRegistered = @"window.matrixRegistration.onRegistered = function(homeserverUrl, userId, accessToken) {   \
    sendObjectMessage({                     \
        'action': 'onRegistered',           \
        'homeServer': homeserverUrl,        \
        'userId': userId,                   \
        'accessToken': accessToken          \
    });                                     \
};";

// The function the fallback page calls when the login is complete
NSString *FallBackViewControllerJavascriptOnLogin = @"window.matrixLogin.onLogin = function(response) {   \
    sendObjectMessage({             \
        'action': 'onLogin',        \
        'response': response        \
    });                            \
};";

@interface AuthFallBackViewController ()

@end

@implementation AuthFallBackViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Catch js logs
    [self enableDebug];
    
    // Due to https://developers.googleblog.com/2016/08/modernizing-oauth-interactions-in-native-apps.html, we hack
    // the user agent to bypass the limitation of Google, as a quick fix (a proper solution will be to use the SSO SDK)
    webView.customUserAgent = @"Mozilla/5.0";

    [self clearCookies];
}

- (void)clearCookies
{
    // TODO: it would be better to do that at WKWebView init like below
    // but this code is part of the kit
    // WKWebViewConfiguration *config = [WKWebViewConfiguration new];
    // config.websiteDataStore = [WKWebsiteDataStore nonPersistentDataStore];
    // webView = [[WKWebView alloc] initWithFrame:self.view.frame configuration:config];

    WKWebsiteDataStore *dateStore = [WKWebsiteDataStore defaultDataStore];
    [dateStore fetchDataRecordsOfTypes:[WKWebsiteDataStore allWebsiteDataTypes]
                     completionHandler:^(NSArray<WKWebsiteDataRecord *> * __nonnull records)
     {
         for (WKWebsiteDataRecord *record  in records)
         {
             [[WKWebsiteDataStore defaultDataStore] removeDataOfTypes:record.dataTypes
                                                       forDataRecords:@[record]
                                                    completionHandler:^
              {
                 MXLogDebug(@"[AuthFallBackViewController] clearCookies: Cookies for %@ deleted successfully", record.displayName);
              }];
         }
     }];
}

- (void)showErrorAsAlert:(NSError*)error
{
    NSString *title = [error.userInfo valueForKey:NSLocalizedFailureReasonErrorKey];
    NSString *msg = [error.userInfo valueForKey:NSLocalizedDescriptionKey];
    if (!title)
    {
        if (msg)
        {
            title = msg;
            msg = nil;
        }
        else
        {
            title = [MatrixKitL10n error];
        }
    }

    MXWeakify(self);

    UIAlertController *alert = [UIAlertController alertControllerWithTitle:title message:msg preferredStyle:UIAlertControllerStyleAlert];
    [alert addAction:[UIAlertAction actionWithTitle:[MatrixKitL10n ok]
                                              style:UIAlertActionStyleDefault
                                            handler:^(UIAlertAction * action) {
                                                MXStrongifyAndReturnIfNil(self);

                                                if (self.delegate)
                                                {
                                                    [self.delegate authFallBackViewControllerDidClose:self];
                                                }

                                            }]];

    [self presentViewController:alert animated:YES completion:nil];
}


#pragma mark - WKNavigationDelegate

- (void)webView:(WKWebView *)webView didFinishNavigation:(WKNavigation *)navigation
{
    [super webView:webView didFinishNavigation:navigation];

    // Set up JS <-> iOS bridge
    [webView evaluateJavaScript:FallBackViewControllerJavascriptSendObjectMessage completionHandler:nil];
    [webView evaluateJavaScript:FallBackViewControllerJavascriptOnRegistered completionHandler:nil];
    [webView evaluateJavaScript:FallBackViewControllerJavascriptOnLogin completionHandler:nil];

    // Check connectivity
    if ([AppDelegate theDelegate].isOffline)
    {
        NSError *error = [NSError errorWithDomain:NSURLErrorDomain
                                             code:NSURLErrorNotConnectedToInternet
                                         userInfo:@{
                                                    NSLocalizedDescriptionKey : [VectorL10n networkOfflinePrompt]
                                                    }];
        [self showErrorAsAlert:error];
    }
}

- (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler
{
    NSString *urlString = navigationAction.request.URL.absoluteString;

    // TODO: We should use the WebKit PostMessage API and the
    // `didReceiveScriptMessage` delegate to manage the JS<->Native bridge
    if ([urlString hasPrefix:@"js:"])
    {
        // Listen only to scheme of the JS-WKWebView bridge
        NSString *jsonString = [[[urlString componentsSeparatedByString:@"js:"] lastObject]  stringByReplacingPercentEscapesUsingEncoding:NSASCIIStringEncoding];
        NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];

        NSError *error;
        NSDictionary *parameters = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers
                                                                     error:&error];

        if (!error)
        {
            if ([@"onRegistered" isEqualToString:parameters[@"action"]])
            {
                // Translate the JS registration event to MXLoginResponse
                // We cannot use [MXLoginResponse modelFromJSON:] because of https://github.com/matrix-org/synapse/issues/4756
                // Because of this issue, we cannot get the device_id allocated by the homeserver
                // TODO: Fix it once the homeserver issue is fixed (filed at https://github.com/vector-im/riot-meta/issues/273).
                MXLoginResponse *loginResponse = [MXLoginResponse new];
                loginResponse.homeserver = parameters[@"homeServer"];
                loginResponse.userId = parameters[@"userId"];
                loginResponse.accessToken = parameters[@"accessToken"];

                // Sanity check
                if (self.delegate
                    && loginResponse.homeserver.length && loginResponse.userId.length && loginResponse.accessToken.length)
                {
                    // And inform the client
                    [self.delegate authFallBackViewController:self didLoginWithLoginResponse:loginResponse];
                }
            }
            else if ([@"onLogin" isEqualToString:parameters[@"action"]])
            {
                // Translate the JS login event to MXLoginResponse
                MXLoginResponse *loginResponse;
                MXJSONModelSetMXJSONModel(loginResponse, MXLoginResponse, parameters[@"response"]);

                // Sanity check
                if (self.delegate
                    && loginResponse.homeserver.length && loginResponse.userId.length && loginResponse.accessToken.length)
                {
                    // And inform the client
                    [self.delegate authFallBackViewController:self didLoginWithLoginResponse:loginResponse];
                }
            }
        }
        
        decisionHandler(WKNavigationActionPolicyCancel);
        return;
    }

    decisionHandler(WKNavigationActionPolicyAllow);
}

@end