Zig

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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const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

    const ftp = try chilkat.Ftp2.init();
    defer ftp.deinit();

    ftp.setHostname("ftp.example.com");
    ftp.setUsername("myFtpLogin");

    ftp.setAuthTls(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.
    ftp.setPassword("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.setRequireSslCertVerify(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.
    ftp.setTlsPinSet("sha256//YLh1dUR9y6Kja30RrAn7JKnbQG/uEtLMkBgFF2Fuihg=");

    ftp.connect() catch {
        std.debug.print("{s}\n", .{try ftp.getLastErrorText(alloc)});
        return;
    };

    // SslServerCertVerified reports whether the certificate chain was successfully verified.
    if (ftp.getSslServerCertVerified()) {
        std.debug.print("The server certificate was verified.\n", .{});
    }

    ftp.disconnect() catch {
        std.debug.print("{s}\n", .{try ftp.getLastErrorText(alloc)});
        return;
    };
}