GCDAsyncSocket startTLS does not work

Question

I am able to connect to the desired socket with IP and port.

- (void)socket:(GCDAsyncSocket *)sender didConnectToHost:(NSString *)host port:(UInt16)port {

    [sender startTLS:nil];

    if(self.createTCPSocketHelperDelegate && @selector(returnConnectedTCPSocket:forNASWithMacAddress:))
    {
        [self.createTCPSocketHelperDelegate returnConnectedTCPSocket:sender forNASWithMacAddress:_macAddress];
    }
}

I am sending TLS settings dictionary nil for as it uses default settings. It gives me the error as follows

Error Domain=kCFStreamErrorDomainSSL Code=-9806 "The operation couldn’t be completed. (kCFStreamErrorDomainSSL error -9806.)" UserInfo=0x17d92420 {NSLocalizedRecoverySuggestion=Error code definition can be found in Apple's SecureTransport.h}

I couldn't get what's wrong going on there. Please help me to provide some sample code which connect to SSL server and use TCP/TLS protocol.

Help would be appreciated. Thank you in advance. :)

Ashish · Accepted Answer · 2016-03-23 08:39:37Z

I got the issue. Basically I couldn't complete SSL handshake, I found the way as follows:

Initialize GCDAsyncSocket socket and connect to IP and Port as follows,

NSError *error;

_gcdAsyncTCPSocket  = [[GCDAsyncSocket alloc] initWithDelegate:self
                                                 delegateQueue:dispatch_get_main_queue()];

_gcdAsyncTCPSocket.delegate = self;

_ipAddress = ipAddress;

_tcpPortNumber = portNumber;

if(![_gcdAsyncTCPSocket connectToHost:ipAddress onPort:portNumber withTimeout:30 error:&error])
{
    if(self.createTCPSocketHelperDelegate && @selector(failedToCreateTCPSocket))
    {
        [self.createTCPSocketHelperDelegate failedToCreateTCPSocket];
    }
}else {

    NSMutableDictionary *settings = [[NSMutableDictionary alloc] init];

    [settings setObject:[NSNumber numberWithBool:YES]
                 forKey:GCDAsyncSocketManuallyEvaluateTrust];

    [_gcdAsyncTCPSocket startTLS:settings];
}

When you set GCDAsyncSocketManuallyEvaluateTrust it gives a call to delegate method

- (void)socket:(GCDAsyncSocket *)sock didReceiveTrust:(SecTrustRef)trust completionHandler:(void (^)(BOOL shouldTrustPeer))completionHandler

In which I have evaluate the server's self signed certificate with the local certificate. If its equal then completionHandler(YES) otherwise completionHandler(NO) as follows:

- (void)socket:(GCDAsyncSocket *)sock didReceiveTrust:(SecTrustRef)trust completionHandler:(void (^)(BOOL shouldTrustPeer))completionHandler {
NSLog(@"didReceiveTrust");

//server certificate
SecCertificateRef serverCertificate = SecTrustGetCertificateAtIndex(trust, 0);
CFDataRef serverCertificateData = SecCertificateCopyData(serverCertificate);

const UInt8* const serverData = CFDataGetBytePtr(serverCertificateData);
const CFIndex serverDataSize = CFDataGetLength(serverCertificateData);
NSData* cert1 = [NSData dataWithBytes:serverData length:(NSUInteger)serverDataSize];


//local certificate
NSString *localCertFilePath = [[NSBundle mainBundle] pathForResource:@"LocalCertificate" ofType:@"cer"];
NSData *localCertData = [NSData dataWithContentsOfFile:localCertFilePath];
CFDataRef myCertData = (__bridge CFDataRef)localCertData;


const UInt8* const localData = CFDataGetBytePtr(myCertData);
const CFIndex localDataSize = CFDataGetLength(myCertData);
NSData* cert2 = [NSData dataWithBytes:localData length:(NSUInteger)localDataSize];


if (cert1 == nil || cert2 == nil) {
    NSLog(@"Certificate NULL");
    completionHandler(NO);
    return;
}


const BOOL equal = [cert1 isEqualToData:cert2];

if (equal) {

    NSLog(@"Certificate match");
    completionHandler(YES);

}else{

    NSLog(@"Certificate not match");
    completionHandler(NO);
}
}

If certificates matches completionHandler(YES) it will call delegate

- (void)socketDidSecure:(GCDAsyncSocket *)sock {

NSLog(@"socketDidSecure");

_uploadSocket = sock;

//Do your stuff after this
}

Hope it will help someone to deal with SSL and GCDAsyncSocket. Happy coding!!

Thanks for this detailed answer. Is having a local certificate absolutely necessary? Is there another route where comparison with a saved local certificate isn't necessary?
Having a local cert to compare to is only necessary if you have a self-signed cert on the server. The question doesn't ask about self-signed certs so I don't think this answer is relevant.

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