Lua

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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Lua

local chilkat = require("chilkat")

local ftp = chilkat.Ftp2.new()

ftp.hostname = "ftp.example.com"
ftp.username = "myFtpLogin"

ftp.auth_tls = 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.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.require_ssl_cert_verify = 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.tls_pin_set = "sha256//YLh1dUR9y6Kja30RrAn7JKnbQG/uEtLMkBgFF2Fuihg="

local success = ftp:connect()
if not success then
    print(ftp.last_error_text)
    return
end

-- SslServerCertVerified reports whether the certificate chain was successfully verified.
if ftp.ssl_server_cert_verified then
    print("The server certificate was verified.")
end

success = ftp:disconnect()
if not success then
    print(ftp.last_error_text)
    return
end