DataFlex

Get TLS Server's SPKI Fingerprint

See more Socket/SSL/TLS Examples

Gets the SPKI fingerprint of a TLS server.

What is Pinning?

Pinning is the process of associating a host with their expected X509 certificate or public key. Once a certificate or public key is known or seen for a host, the certificate or public key is associated or 'pinned' to the host. If more than one certificate or public key is acceptable, then the program holds a pinset. In this case, the advertised identity must match one of the elements in the pinset. A host or service's certificate or public key can be added to an application at development time, or it can be added upon first encountering the certificate or public key. The former - adding at development time - is preferred since preloading the certificate or public key out of band usually means the attacker cannot taint the pin. ..

TLS public key pinning is implemented by (1) making it possible to easily get the SPKI fingerprint of a certificate, and (2) adding the TlsPinSet property to classes that can establish TLS connections.

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoTlsSock
    Boolean iBConnectUsingTls
    Integer iMaxWaitMs
    Variant vCert
    Handle hoCert
    String sTemp1

    Move False To iSuccess

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    Get Create (RefClass(cComChilkatSocket)) To hoTlsSock
    If (Not(IsComObjectCreated(hoTlsSock))) Begin
        Send CreateComObject of hoTlsSock
    End

    // Establish a TLS connection with any remote TLS server.
    // The type of server could be anything: HTTP, IMAP, SMTP, FTP, POP3, etc.
    // as long as it is TLS (i.e. it connects implicitly using TLS).
    Move True To iBConnectUsingTls
    Move 5000 To iMaxWaitMs
    Get ComConnect Of hoTlsSock "imap.gmail.com" 993 iBConnectUsingTls iMaxWaitMs To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTlsSock To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Get the server certificate.
    Get Create (RefClass(cComChilkatCert)) To hoCert
    If (Not(IsComObjectCreated(hoCert))) Begin
        Send CreateComObject of hoCert
    End
    Get pvComObject of hoCert to vCert
    Get ComGetServerCert Of hoTlsSock vCert To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTlsSock To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // The GetSpkiFingerprint method returns the SPKI Fingerprint suitable for use in pinning.
    //  (See RFC 7469.)  An SPKI Fingerprint is defined as the output of a known cryptographic hash
    //  algorithm whose input is the DER-encoded ASN.1 representation of  the Subject Public Key Info
    // (SPKI) of an X.509 certificate.  The first argument specifies the hash algorithm and may be
    // "sha256", "sha384", "sha512", "sha1", "md2", "md5", "haval", "ripemd128", 
    // "ripemd160","ripemd256", or "ripemd320".   
    // The second argument specifies the encoding, and may be "base64", "hex", 
    // or any of the encoding modes specified at http://www.cknotes.com/chilkat-binary-encoding-list/
    // DN = "Distinguished Name"
    Get ComGetSpkiFingerprint Of hoCert "sha256" "base64" To sTemp1
    Showln "SPKI Fingerprint: " sTemp1


End_Procedure