(PureBasic) 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".

Note: This example requires Chilkat v11.0.0 or greater.

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IncludeFile "CkSocket.pb"
IncludeFile "CkCert.pb"

Procedure ChilkatExample()

    success.i = 0

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

    listenSslSocket.i = CkSocket::ckCreate()
    If listenSslSocket.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

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

    cert.i = CkCert::ckCreate()
    If cert.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; The 1st argument is the file path, the 2nd arg is the 
    ; PFX file's password:
    success = CkCert::ckLoadPfxFile(cert,"chilkat.pfx","test")
    If success = 0
        Debug CkCert::ckLastErrorText(cert)
        CkSocket::ckDispose(listenSslSocket)
        CkCert::ckDispose(cert)
        ProcedureReturn
    EndIf

    ; 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.
    CkSocket::ckAddSslAcceptableClientCaDn(listenSslSocket,"C=SE, O=AddTrust AB, OU=AddTrust External TTP Network, CN=AddTrust External CA Root")
    CkSocket::ckAddSslAcceptableClientCaDn(listenSslSocket,"O=Digital Signature Trust Co., CN=DST Root CA X3")

    ; Use the certificate:
    success = CkSocket::ckInitSslServer(listenSslSocket,cert)
    If success = 0
        Debug CkSocket::ckLastErrorText(listenSslSocket)
        CkSocket::ckDispose(listenSslSocket)
        CkCert::ckDispose(cert)
        ProcedureReturn
    EndIf

    ; Bind and listen on a port:
    myPort.i = 8123
    ; Allow for a max of 5 queued connect requests.
    backLog.i = 5
    success = CkSocket::ckBindAndListen(listenSslSocket,myPort,backLog)
    If success = 0
        Debug CkSocket::ckLastErrorText(listenSslSocket)
        CkSocket::ckDispose(listenSslSocket)
        CkCert::ckDispose(cert)
        ProcedureReturn
    EndIf

    ; 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 
    ; AcceptNext can hang indefinitely during the SSL handshake process. 
    ; Make sure these properties are set to appropriate values before calling AcceptNext.

    ; Set a 10 second max for waiting to read/write.  This is for the SSL/TLS handshake establishment.
    CkSocket::setCkMaxReadIdleMs(listenSslSocket, 10000)
    CkSocket::setCkMaxSendIdleMs(listenSslSocket, 10000)

    ; Accept a single client connection and establish the secure SSL/TLS channel:
    maxWaitMillisec.i = 20000
    clientSock.i = CkSocket::ckCreate()
    If clientSock.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkSocket::ckAcceptNext(listenSslSocket,maxWaitMillisec,clientSock)
    If success = 0
        Debug CkSocket::ckLastErrorText(listenSslSocket)
        CkSocket::ckDispose(listenSslSocket)
        CkCert::ckDispose(cert)
        CkSocket::ckDispose(clientSock)
        ProcedureReturn
    EndIf

    ; The client (in this example) is going to send a "Hello Server! -EOM-" 
    ; message.  Read it:
    receivedMsg.s = CkSocket::ckReceiveUntilMatch(clientSock,"-EOM-")
    If CkSocket::ckLastMethodSuccess(clientSock) = 0
        Debug CkSocket::ckLastErrorText(clientSock)
        CkSocket::ckDispose(listenSslSocket)
        CkCert::ckDispose(cert)
        CkSocket::ckDispose(clientSock)
        ProcedureReturn
    EndIf

    Debug receivedMsg

    ; Send a "Hello Client! -EOM-" message:
    success = CkSocket::ckSendString(clientSock,"Hello Client! -EOM-")
    If success = 0
        Debug CkSocket::ckLastErrorText(clientSock)
        CkSocket::ckDispose(listenSslSocket)
        CkCert::ckDispose(cert)
        CkSocket::ckDispose(clientSock)
        ProcedureReturn
    EndIf

    ; Close the connection with the client
    ; Wait a max of 20 seconds (20000 millsec)
    success = CkSocket::ckClose(clientSock,20000)


    CkSocket::ckDispose(listenSslSocket)
    CkCert::ckDispose(cert)
    CkSocket::ckDispose(clientSock)


    ProcedureReturn
EndProcedure