Signal-iOS/src/Network/WebSockets/TSSocketManager.m

//
//  TSSocketManager.m
//  TextSecureiOS
//
//  Created by Frederic Jacobs on 17/05/14.
//  Copyright (c) 2014 Open Whisper Systems. All rights reserved.
//

#import "SubProtocol.pb.h"

#import "TSAccountManager.h"
#import "TSConstants.h"
#import "TSMessagesManager.h"
#import "TSSocketManager.h"
#import "TSStorageManager+keyingMaterial.h"

#import "OWSWebsocketSecurityPolicy.h"
#import "Cryptography.h"

#define kWebSocketHeartBeat 30
#define kWebSocketReconnectTry 5
#define kBackgroundConnectTimer 25
#define kBackgroundConnectKeepAlive 15

NSString *const SocketOpenedNotification     = @"SocketOpenedNotification";
NSString *const SocketClosedNotification     = @"SocketClosedNotification";
NSString *const SocketConnectingNotification = @"SocketConnectingNotification";

@interface TSSocketManager ()
@property (nonatomic, retain) NSTimer *pingTimer;
@property (nonatomic, retain) NSTimer *reconnectTimer;


@property (nonatomic, retain) SRWebSocket *websocket;
@property (nonatomic) SocketStatus status;

@property (nonatomic) UIBackgroundTaskIdentifier fetchingTaskIdentifier;

@property BOOL didConnectBg;
@property BOOL didRetreiveMessageBg;
@property BOOL shouldDownloadMessage;

@property (nonatomic, retain) NSTimer *backgroundKeepAliveTimer;
@property (nonatomic, retain) NSTimer *backgroundConnectTimer;

@end

@implementation TSSocketManager

- (instancetype)init {
    self = [super init];

    if (self) {
        self.websocket = nil;
        [self addObserver:self forKeyPath:@"status" options:0 context:kSocketStatusObservationContext];
    }

    return self;
}

+ (instancetype)sharedManager {
    static TSSocketManager *sharedMyManager = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
      sharedMyManager                        = [[self alloc] init];
      sharedMyManager.fetchingTaskIdentifier = UIBackgroundTaskInvalid;
      sharedMyManager.didConnectBg           = NO;
      sharedMyManager.shouldDownloadMessage  = NO;
      sharedMyManager.didRetreiveMessageBg   = NO;
    });
    return sharedMyManager;
}

#pragma mark - Manage Socket

+ (void)becomeActive {
    TSSocketManager *sharedInstance = [self sharedManager];
    SRWebSocket *socket             = [sharedInstance websocket];

    if (socket) {
        switch ([socket readyState]) {
            case SR_OPEN:
                DDLogVerbose(@"WebSocket already open on connection request");
                sharedInstance.status = kSocketStatusOpen;
                return;
            case SR_CONNECTING:
                DDLogVerbose(@"WebSocket is already connecting");
                sharedInstance.status = kSocketStatusConnecting;
                return;
            default:
                [socket close];
                sharedInstance.status = kSocketStatusClosed;
                socket.delegate       = nil;
                socket                = nil;
                break;
        }
    }

    NSString *webSocketConnect =
        [textSecureWebSocketAPI stringByAppendingString:[[self sharedManager] webSocketAuthenticationString]];
    NSURL *webSocketConnectURL   = [NSURL URLWithString:webSocketConnect];
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:webSocketConnectURL];

    socket          = [[SRWebSocket alloc] initWithURLRequest:request securityPolicy:[OWSWebsocketSecurityPolicy sharedPolicy]];
    socket.delegate = [self sharedManager];

    [[self sharedManager] setWebsocket:socket];
    [socket open];
}

+ (void)resignActivity {
    SRWebSocket *socket = [[self sharedManager] websocket];
    [socket close];
}

#pragma mark - Delegate methods

- (void)webSocketDidOpen:(SRWebSocket *)webSocket {
    self.pingTimer = [NSTimer timerWithTimeInterval:kWebSocketHeartBeat
                                             target:self
                                           selector:@selector(webSocketHeartBeat)
                                           userInfo:nil
                                            repeats:YES];

    // Additionally, we want the ping timer to work in the background too.
    [[NSRunLoop mainRunLoop] addTimer:self.pingTimer forMode:NSDefaultRunLoopMode];

    self.status = kSocketStatusOpen;
    [self.reconnectTimer invalidate];
    self.reconnectTimer = nil;
    self.didConnectBg   = YES;
}

- (void)webSocket:(SRWebSocket *)webSocket didFailWithError:(NSError *)error {
    DDLogError(@"Error connecting to socket %@", error);

    [self.pingTimer invalidate];
    self.status = kSocketStatusClosed;
    [self scheduleRetry];
}

- (void)webSocket:(SRWebSocket *)webSocket didReceiveMessage:(NSData *)data {
    WebSocketMessage *wsMessage = [WebSocketMessage parseFromData:data];
    self.didRetreiveMessageBg   = YES;

    if (wsMessage.type == WebSocketMessageTypeRequest) {
        [self processWebSocketRequestMessage:wsMessage.request];
    } else if (wsMessage.type == WebSocketMessageTypeResponse) {
        [self processWebSocketResponseMessage:wsMessage.response];
    } else {
        DDLogWarn(@"Got a WebSocketMessage of unknown type");
    }
}

- (void)processWebSocketRequestMessage:(WebSocketRequestMessage *)message {
    DDLogInfo(@"Got message with verb: %@ and path: %@", message.verb, message.path);

    [self sendWebSocketMessageAcknowledgement:message];
    [self keepAliveBackground];

    if ([message.path isEqualToString:@"/api/v1/message"] && [message.verb isEqualToString:@"PUT"]) {
        NSData *decryptedPayload =
            [Cryptography decryptAppleMessagePayload:message.body withSignalingKey:TSStorageManager.signalingKey];

        if (!decryptedPayload) {
            DDLogWarn(@"Failed to decrypt incoming payload or bad HMAC");
            return;
        }

        OWSSignalServiceProtosEnvelope *envelope = [OWSSignalServiceProtosEnvelope parseFromData:decryptedPayload];

        [[TSMessagesManager sharedManager] handleReceivedEnvelope:envelope];
    } else {
        DDLogWarn(@"Unsupported WebSocket Request");
    }
}

- (void)keepAliveBackground {
    [self.backgroundConnectTimer invalidate];

    if (self.fetchingTaskIdentifier) {
        [self.backgroundKeepAliveTimer invalidate];

        self.backgroundKeepAliveTimer = [NSTimer timerWithTimeInterval:kBackgroundConnectKeepAlive
                                                                target:self
                                                              selector:@selector(backgroundTimeExpired)
                                                              userInfo:nil
                                                               repeats:NO];
        // Additionally, we want the reconnect timer to work in the background too.
        [[NSRunLoop mainRunLoop] addTimer:self.backgroundKeepAliveTimer forMode:NSDefaultRunLoopMode];
    }
}

- (void)processWebSocketResponseMessage:(WebSocketResponseMessage *)message {
    DDLogWarn(@"Client should not receive WebSocket Respond messages");
}

- (void)sendWebSocketMessageAcknowledgement:(WebSocketRequestMessage *)request {
    WebSocketResponseMessageBuilder *response = [WebSocketResponseMessage builder];
    [response setStatus:200];
    [response setMessage:@"OK"];
    [response setId:request.id];

    WebSocketMessageBuilder *message = [WebSocketMessage builder];
    [message setResponse:response.build];
    [message setType:WebSocketMessageTypeResponse];

    @try {
        [self.websocket send:message.build.data];
    } @catch (NSException *exception) {
        DDLogWarn(@"Caught exception while trying to write on the socket %@", exception.debugDescription);
    }
}

- (void)webSocket:(SRWebSocket *)webSocket
 didCloseWithCode:(NSInteger)code
           reason:(NSString *)reason
         wasClean:(BOOL)wasClean {
    [self.pingTimer invalidate];
    self.status = kSocketStatusClosed;

    if (!wasClean && [UIApplication sharedApplication].applicationState == UIApplicationStateActive) {
        [self scheduleRetry];
    }
}

- (void)webSocketHeartBeat {
    NSError *error;

    [self.websocket sendPing:nil error:&error];
    if (error) {
        DDLogWarn(@"Error in websocket heartbeat: %@", error.localizedDescription);
    }
}

- (NSString *)webSocketAuthenticationString {
    return [NSString
        stringWithFormat:@"?login=%@&password=%@",
                         [[TSStorageManager localNumber] stringByReplacingOccurrencesOfString:@"+" withString:@"%2B"],
                         [TSStorageManager serverAuthToken]];
}

- (void)scheduleRetry {
    if (![self.reconnectTimer isValid]) {
        self.reconnectTimer = [NSTimer timerWithTimeInterval:kWebSocketReconnectTry
                                                      target:[self class]
                                                    selector:@selector(becomeActive)
                                                    userInfo:nil
                                                     repeats:YES];
        // Additionally, we want the reconnect timer to work in the background too.
        [[NSRunLoop mainRunLoop] addTimer:self.reconnectTimer forMode:NSDefaultRunLoopMode];
    } else {
        DDLogWarn(@"Not scheduling retry, valid timer");
    }
}

#pragma mark - Background Connect

+ (void)becomeActiveFromForeground {
    TSSocketManager *sharedInstance = [self sharedManager];

    if (sharedInstance.fetchingTaskIdentifier != UIBackgroundTaskInvalid) {
        [sharedInstance closeBackgroundTask];
    }

    [self becomeActive];
}

+ (void)becomeActiveFromBackgroundExpectMessage:(BOOL)expected {
    TSSocketManager *sharedInstance = [TSSocketManager sharedManager];

    if (sharedInstance.fetchingTaskIdentifier == UIBackgroundTaskInvalid) {
        sharedInstance.backgroundConnectTimer = [NSTimer timerWithTimeInterval:kBackgroundConnectTimer
                                                                        target:sharedInstance
                                                                      selector:@selector(backgroundConnectTimerExpired)
                                                                      userInfo:nil
                                                                       repeats:NO];
        NSRunLoop *loop = [NSRunLoop mainRunLoop];
        [loop addTimer:[TSSocketManager sharedManager].backgroundConnectTimer forMode:NSDefaultRunLoopMode];

        [sharedInstance.backgroundKeepAliveTimer invalidate];
        sharedInstance.didConnectBg          = NO;
        sharedInstance.didRetreiveMessageBg  = NO;
        sharedInstance.shouldDownloadMessage = expected;
        sharedInstance.fetchingTaskIdentifier =
            [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
              [TSSocketManager resignActivity];
              [[TSSocketManager sharedManager] closeBackgroundTask];
            }];

        [self becomeActive];
    } else {
        DDLogWarn(@"Got called to become active in the background but there was already a background task running.");
    }
}

- (void)backgroundConnectTimerExpired {
    [self backgroundTimeExpired];
}

- (void)backgroundTimeExpired {
    [[self class] resignActivity];
    [self closeBackgroundTask];
}

- (void)closeBackgroundTask {
    [self.backgroundKeepAliveTimer invalidate];
    [self.backgroundConnectTimer invalidate];

    /*
     If VOIP Push worked, we should just have to check if message was retreived and if not, alert the user.
     But we have to rely on the server for the fallback in failed cases since background push is unreliable.
     https://devforums.apple.com/message/1135227

     if ((self.shouldDownloadMessage && !self.didRetreiveMessageBg) || !self.didConnectBg) {
     [self backgroundConnectTimedOut];
     }

     */

    [[UIApplication sharedApplication] endBackgroundTask:self.fetchingTaskIdentifier];
    self.fetchingTaskIdentifier = UIBackgroundTaskInvalid;
}

- (void)backgroundConnectTimedOut {
    UILocalNotification *notification = [[UILocalNotification alloc] init];
    notification.alertBody            = NSLocalizedString(@"APN_FETCHED_FAILED", nil);
    notification.soundName            = @"NewMessage.aifc";
    [[UIApplication sharedApplication] presentLocalNotificationNow:notification];
}

#pragma mark UI Delegates

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context {
    if (context == kSocketStatusObservationContext) {
        [self notifyStatusChange];
    } else {
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
}

- (void)notifyStatusChange {
    switch (self.status) {
        case kSocketStatusOpen:
            [[NSNotificationCenter defaultCenter] postNotificationName:SocketOpenedNotification object:self];
            break;
        case kSocketStatusClosed:
            [[NSNotificationCenter defaultCenter] postNotificationName:SocketClosedNotification object:self];
            break;
        case kSocketStatusConnecting:
            [[NSNotificationCenter defaultCenter] postNotificationName:SocketConnectingNotification object:self];
            break;
        default:
            break;
    }
}

+ (void)sendNotification {
    [[self sharedManager] notifyStatusChange];
}

@end