Objective-C

Verify and Pin the FTPS Server Certificate

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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Objective-C

#import <CkoFtp2.h>

BOOL success = NO;

CkoFtp2 *ftp = [[CkoFtp2 alloc] init];

ftp.Hostname = @"ftp.example.com";
ftp.Username = @"myFtpLogin";

ftp.AuthTls = YES;

//  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.
ftp.Password = @"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.
ftp.RequireSslCertVerify = YES;

//  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.
ftp.TlsPinSet = @"sha256//YLh1dUR9y6Kja30RrAn7JKnbQG/uEtLMkBgFF2Fuihg=";

success = [ftp Connect];
if (success == NO) {
    NSLog(@"%@",ftp.LastErrorText);
    return;
}

//  SslServerCertVerified reports whether the certificate chain was successfully verified.
if (ftp.SslServerCertVerified) {
    NSLog(@"%@",@"The server certificate was verified.");
}

success = [ftp Disconnect];
if (success == NO) {
    NSLog(@"%@",ftp.LastErrorText);
    return;
}