WolfSSL documentation provides different PSK example for C# and C++ client examples are different.
Following URL provides PSK client C++ example. https://github.com/wolfSSL/wolfssl-examples/blob/master/psk/client-psk.c
In C++ PSK client example, "wolfSSL_CTX_set_psk_client_callback" function is used.
Where as C# example does not use this function but tries to read shared key from a certificate file.
https://github.com/wolfSSL/wolfssl/tree/master/wrapper/CSharp/wolfSSL-TLS-Client
In our prototype, we need to modify C# client code to use a 4 bytes key like C++ example.
When the function “CTX_set_psk_client_callback” is used in C# example , it gives System.EntryPointNotFoundException for function.
I am not sure what is the problem with this code. I am using wolfssl C# wrapper solution to compile wolfSSL code.
The code for client is as described
public class WolfTLSClient
{
public static void standard_log(int lvl, StringBuilder msg)
{
Console.WriteLine(msg);
}
private static void clean(IntPtr ssl, IntPtr ctx)
{
wolfssl.free(ssl);
wolfssl.CTX_free(ctx);
wolfssl.Cleanup();
}
public static uint psk_client_callback_function(IntPtr ssl, string hint, IntPtr identity, uint id_max_len, IntPtr key, uint max_sz)
{
wolfssl.log(wolfssl.INFO_LOG, "PSK Client Identity = " + identity);
if (max_sz < 4)
return 0;
byte[] tmp = { 26, 43, 60, 77 };
Marshal.Copy(tmp, 0, key, 4);
return (uint)4;
}
public static void Main(string[] args)
{
int _hostPort = 11111;
string IPAddress = "198.162.0.10";
IntPtr ctx;
IntPtr ssl;
Socket tcp;
StringBuilder buff = new StringBuilder(1024);
StringBuilder reply = new StringBuilder("Hello, this is the wolfSSL C# wrapper");
//example of function used for setting logging
wolfssl.SetLogging(standard_log);
wolfssl.Init();
Console.WriteLine("Calling ctx Init from wolfSSL");
ctx = wolfssl.CTX_new(wolfssl.usev23_client());
if (ctx == IntPtr.Zero)
{
Console.WriteLine("Error in creating ctx structure");
return;
}
Console.WriteLine("Finished init of ctx .... now load in CA");
short minDhKey = 128;
wolfssl.CTX_SetMinDhKey_Sz(ctx, minDhKey);
Console.Write("Setting cipher suite to ");
///* In order to use static PSK build wolfSSL with the preprocessor flag WOLFSSL_STATIC_PSK */
StringBuilder set_cipher = new StringBuilder("ECDHE-ECDSA-AES128-GCM-SHA256");
Console.WriteLine(set_cipher);
if (wolfssl.CTX_set_cipher_list(ctx, set_cipher) != wolfssl.SUCCESS)
{
Console.WriteLine("Failed to set cipher suite");
return;
}
wolfssl.psk_client_delegate psk_cb = new wolfssl.psk_client_delegate(psk_client_callback_function);
wolfssl.CTX_set_psk_client_callback(ctx, psk_cb);
/* set up TCP socket */
tcp = new Socket(AddressFamily.InterNetwork, SocketType.Stream,
ProtocolType.Tcp);
try
{
tcp.Connect(IPAddress, _hostPort);
}
catch (Exception e)
{
Console.WriteLine("tcp.Connect() error " + e.ToString());
wolfssl.CTX_free(ctx);
return;
}
if (!tcp.Connected)
{
Console.WriteLine("tcp.Connect() failed!");
tcp.Close();
wolfssl.CTX_free(ctx);
return;
}
Console.WriteLine("Connected TCP");
ssl = wolfssl.new_ssl(ctx);
if (ssl == IntPtr.Zero)
{
Console.WriteLine("Error in creating ssl object");
wolfssl.CTX_free(ctx);
return;
}
Console.WriteLine("Connection made wolfSSL_connect ");
if (wolfssl.set_fd(ssl, tcp) != wolfssl.SUCCESS)
{
/* get and print out the error */
Console.WriteLine(wolfssl.get_error(ssl));
tcp.Close();
clean(ssl, ctx);
return;
}
if (wolfssl.connect(ssl) != wolfssl.SUCCESS)
{
/* get and print out the error */
Console.WriteLine(wolfssl.get_error(ssl));
tcp.Close();
clean(ssl, ctx);
return;
}
/* print out results of TLS/SSL accept */
Console.WriteLine("SSL version is " + wolfssl.get_version(ssl));
Console.WriteLine("SSL cipher suite is " + wolfssl.get_current_cipher(ssl));
if (wolfssl.write(ssl, reply, reply.Length) != reply.Length)
{
Console.WriteLine("Error in write");
tcp.Close();
clean(ssl, ctx);
return;
}
/* read and print out the message then reply */
if (wolfssl.read(ssl, buff, 1023) < 0)
{
Console.WriteLine("Error in read");
tcp.Close();
clean(ssl, ctx);
return;
}
Console.WriteLine(buff);
wolfssl.shutdown(ssl);
tcp.Close();
clean(ssl, ctx);
}
}
