PureBasic

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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PureBasic

IncludeFile "CkFtp2.pb"

Procedure ChilkatExample()

    success.i = 0

    ftp.i = CkFtp2::ckCreate()
    If ftp.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkFtp2::setCkHostname(ftp, "ftp.example.com")
    CkFtp2::setCkUsername(ftp, "myFtpLogin")

    CkFtp2::setCkAuthTls(ftp, 1)

    ;  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::setCkPassword(ftp, "myPassword")

    ;  Reject the connection if the server certificate cannot be verified (expired, bad signature,
    ;  untrusted chain, etc.).  The default is 0, which does not reject on verification
    ;  failure -- set 1 for security.
    CkFtp2::setCkRequireSslCertVerify(ftp, 1)

    ;  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::setCkTlsPinSet(ftp, "sha256//YLh1dUR9y6Kja30RrAn7JKnbQG/uEtLMkBgFF2Fuihg=")

    success = CkFtp2::ckConnect(ftp)
    If success = 0
        Debug CkFtp2::ckLastErrorText(ftp)
        CkFtp2::ckDispose(ftp)
        ProcedureReturn
    EndIf

    ;  SslServerCertVerified reports whether the certificate chain was successfully verified.
    If CkFtp2::ckSslServerCertVerified(ftp)
        Debug "The server certificate was verified."
    EndIf

    success = CkFtp2::ckDisconnect(ftp)
    If success = 0
        Debug CkFtp2::ckLastErrorText(ftp)
        CkFtp2::ckDispose(ftp)
        ProcedureReturn
    EndIf



    CkFtp2::ckDispose(ftp)


    ProcedureReturn
EndProcedure