(Objective-C) Accept TLS Connection with Client Authentication

Demonstrates how to accept a TLS connection requiring client authentication. This is the case where the TLS client sends a certificate. It is also known as "Two-Way SSL".

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#import <CkoSocket.h>
#import <CkoCert.h>
#import <NSString.h>

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

CkoSocket *listenSslSocket = [[CkoSocket alloc] init];

// An SSL/TLS server needs a digital certificate.  This example loads it from a PFX file.
// Note: This is the server's certificate.

CkoCert *cert = [[CkoCert alloc] init];
// The 1st argument is the file path, the 2nd arg is the 
// PFX file's password:
BOOL success = [cert LoadPfxFile: @"chilkat.pfx" password: @"test"];
if (success != YES) {
    NSLog(@"%@",cert.LastErrorText);
    return;
}

// To accept client client certificates in the TLS handshake,
// we must indicate a list of acceptable client certificate root CA DN's
// that are allowed.  (DN is an acronym for Distinguished Name.)
// Call AddSslAcceptableClientCaDn once for each acceptable CA DN.
// Here are a few examples so you can see the general format of a DN.
[listenSslSocket AddSslAcceptableClientCaDn: @"C=SE, O=AddTrust AB, OU=AddTrust External TTP Network, CN=AddTrust External CA Root"];
[listenSslSocket AddSslAcceptableClientCaDn: @"O=Digital Signature Trust Co., CN=DST Root CA X3"];

// Use the certificate:
success = [listenSslSocket InitSslServer: cert];
if (success != YES) {
    NSLog(@"%@",listenSslSocket.LastErrorText);
    return;
}

// Bind and listen on a port:
int myPort = 8123;
// Allow for a max of 5 queued connect requests.
int backLog = 5;
success = [listenSslSocket BindAndListen: [NSNumber numberWithInt: myPort] backlog: [NSNumber numberWithInt: backLog]];
if (success != YES) {
    NSLog(@"%@",listenSslSocket.LastErrorText);
    return;
}

// If accepting an SSL/TLS connection, the SSL handshake is part of the connection
// establishment process. This involves a few back-and-forth messages between the 
// client and server to establish algorithms and a shared key to create the secure 
// channel. The sending and receiving of these messages are governed by the 
// MaxReadIdleMs and MaxSendIdleMs properties. If these properties are set to 0 
// (and this is the default unless changed by your application), then the 
// AcceptNextConnection can hang indefinitely during the SSL handshake process. 
// Make sure these properties are set to appropriate values before calling AcceptNextConnection.

// Set a 10 second max for waiting to read/write.  This is for the SSL/TLS handshake establishment.
listenSslSocket.MaxReadIdleMs = [NSNumber numberWithInt:10000];
listenSslSocket.MaxSendIdleMs = [NSNumber numberWithInt:10000];

// Accept a single client connection and establish the secure SSL/TLS channel:
CkoSocket *clientSock = 0;
int maxWaitMillisec = 20000;
clientSock = [listenSslSocket AcceptNextConnection: [NSNumber numberWithInt: maxWaitMillisec]];
if (listenSslSocket.LastMethodSuccess == NO) {
    NSLog(@"%@",listenSslSocket.LastErrorText);
    return;
}

// The client (in this example) is going to send a "Hello Server! -EOM-" 
// message.  Read it:
NSString *receivedMsg = [clientSock ReceiveUntilMatch: @"-EOM-"];
if (clientSock.LastMethodSuccess != YES) {
    NSLog(@"%@",clientSock.LastErrorText);
    return;
}

NSLog(@"%@",receivedMsg);

// Send a "Hello Client! -EOM-" message:
success = [clientSock SendString: @"Hello Client! -EOM-"];
if (success != YES) {
    NSLog(@"%@",clientSock.LastErrorText);
    return;
}

// Close the connection with the client
// Wait a max of 20 seconds (20000 millsec)
success = [clientSock Close: [NSNumber numberWithInt: 20000]];