Verify and Pin the FTPS Server Certificate

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Demonstrates the certificate-verification properties RequireSslCertVerify, TlsPinSet, and the read-only SslServerCertVerified.

Background: By default a TLS connection is not rejected merely because certificate-chain verification fails, so RequireSslCertVerify = true is the important hardening step — it makes an expired, unsigned, or untrusted certificate abort the connection. TlsPinSet adds public-key pinning on top: the handshake fails unless the server's SPKI fingerprint matches one you configured, defending against a mis-issued certificate that would otherwise validate. Pinning supplements verification rather than replacing it. SslServerCertVerified reports the outcome.

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#include <C_CkFtp2.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkFtp2 ftp;

    success = FALSE;

    ftp = CkFtp2_Create();

    CkFtp2_putHostname(ftp,"ftp.example.com");
    CkFtp2_putUsername(ftp,"myFtpLogin");

    CkFtp2_putAuthTls(ftp,TRUE);

    //  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.
    CkFtp2_putPassword(ftp,"myPassword");

    //  Reject the connection if the server certificate cannot be verified (expired, bad signature,
    //  untrusted chain, etc.).  The default is FALSE, which does not reject on verification
    //  failure -- set TRUE for security.
    CkFtp2_putRequireSslCertVerify(ftp,TRUE);

    //  Optionally pin the server's public key.  If none of the configured SPKI fingerprints matches,
    //  the TLS handshake fails.  Pinning supplements normal verification; it does not replace it.
    CkFtp2_putTlsPinSet(ftp,"sha256//YLh1dUR9y6Kja30RrAn7JKnbQG/uEtLMkBgFF2Fuihg=");

    success = CkFtp2_Connect(ftp);
    if (success == FALSE) {
        printf("%s\n",CkFtp2_lastErrorText(ftp));
        CkFtp2_Dispose(ftp);
        return;
    }

    //  SslServerCertVerified reports whether the certificate chain was successfully verified.
    if (CkFtp2_getSslServerCertVerified(ftp)) {
        printf("The server certificate was verified.\n");
    }

    success = CkFtp2_Disconnect(ftp);
    if (success == FALSE) {
        printf("%s\n",CkFtp2_lastErrorText(ftp));
        CkFtp2_Dispose(ftp);
        return;
    }



    CkFtp2_Dispose(ftp);

    }