SSH Through a SOCKS Proxy

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Demonstrates connecting to an SSH server through a SOCKS4 or SOCKS5 proxy. Set the SOCKS properties before calling Connect, and set SocksVersion to match the proxy server.

Background: SOCKS is a general-purpose TCP relay, so unlike an HTTP proxy it is designed from the start to carry arbitrary protocols — usually the smoother option for SSH. The version matters: SOCKS4 supports only a username with no password, while SOCKS5 supports full login/password authentication as well as IPv6 and remote DNS resolution. Note this is the inverse of dynamic port forwarding: here a SOCKS proxy is used to reach the SSH server, rather than SSH providing a SOCKS proxy.

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#include <C_CkSsh.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkSsh ssh;
    const char *hostname;
    int port;
    const char *password;

    success = FALSE;

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

    //  Demonstrates connecting to an SSH server through a SOCKS4 or SOCKS5 proxy.

    ssh = CkSsh_Create();

    //  Set the SOCKS proxy properties before connecting.  The hostname may be a domain name or an
    //  IP address.
    CkSsh_putSocksHostname(ssh,"socks.example.com");
    CkSsh_putSocksPort(ssh,1080);
    CkSsh_putSocksUsername(ssh,"mySocksLogin");
    CkSsh_putSocksPassword(ssh,"mySocksPassword");

    //  Set the version to match the proxy server: 4 or 5.
    //  Note: SOCKS4 supports only a username, with no password.  SOCKS5 supports full
    //  login/password authentication.
    CkSsh_putSocksVersion(ssh,5);

    hostname = "ssh.example.com";
    port = 22;
    success = CkSsh_Connect(ssh,hostname,port);
    if (success == FALSE) {
        printf("%s\n",CkSsh_lastErrorText(ssh));
        CkSsh_Dispose(ssh);
        return;
    }

    printf("Connected to the SSH server through the SOCKS proxy.\n");

    //  Normally you would not hard-code the password in source.  You should instead obtain it
    //  from an interactive prompt, environment variable, or a secrets vault.
    password = "mySshPassword";

    success = CkSsh_AuthenticatePw(ssh,"mySshLogin",password);
    if (success == FALSE) {
        printf("%s\n",CkSsh_lastErrorText(ssh));
        CkSsh_Dispose(ssh);
        return;
    }

    //  ... use the SSH connection normally ...

    CkSsh_Disconnect(ssh);


    CkSsh_Dispose(ssh);

    }