(DataFlex) Using the ASN.1 API to Create a Certificate Request (CSR)

Note: This example requires Chilkat v9.5.0.50 or greater.

This example demonstrates how to use the Chilkat ASN.1 API to create a certificate signing request. The purpose of this example is to show, in general, how to use the ASN.1 methods to create an ASN.1 document and save to DER. There may be more concise ways of creating a CSR rather than using the lower-level ASN.1 methods presented here. The hope is that this example will enable developers to create many different kinds of ASN.1 structures/documents for which no other means exist.

This example will create ASN.1 having this structure and content:

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

Use ChilkatAx-win32.pkg

Procedure Test
    Handle hoChilkatGlob
    Boolean iSuccess
    Handle hoAsnRoot
    Variant vAsnCertReqInfo
    Handle hoAsnCertReqInfo
    Variant vAsnCertSubject
    Handle hoAsnCertSubject
    Variant vAsnTemp
    Handle hoAsnTemp
    Variant vAsnPubKeyInfo
    Handle hoAsnPubKeyInfo
    Variant vAsnPubKeyAlgId
    Handle hoAsnPubKeyAlgId
    Handle hoAsnRsaKey
    String sRsaKeyDerBase64
    Variant vAsnAlgId
    Handle hoAsnAlgId
    String sCsrBase64
    Handle hoPem
    String sTemp1

    // Starting in v9.5.0.49, all Chilkat classes can be unlocked at once at the beginning of a program
    // by calling UnlockBundle.  It requires a Bundle unlock code.
    Get Create (RefClass(cComChilkatGlobal)) To hoChilkatGlob
    If (Not(IsComObjectCreated(hoChilkatGlob))) Begin
        Send CreateComObject of hoChilkatGlob
    End
    Get ComUnlockBundle Of hoChilkatGlob "Anything for 30-day trial." To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoChilkatGlob To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // A new ASN.1 object is automatically a SEQUENCE.
    // Given that the CSR's root item is a SEQUENCE, we can use
    // this as the root of our CSR.
    Get Create (RefClass(cComChilkatAsn)) To hoAsnRoot
    If (Not(IsComObjectCreated(hoAsnRoot))) Begin
        Send CreateComObject of hoAsnRoot
    End

    // Beneath the root, we have a SEQUENCE (the certificate request info), 
    // another SEQUENCE (the algorithm identifier), and a BITSTRING (this signature data)

    Get ComAppendSequence Of hoAsnRoot To iSuccess
    Get ComAppendSequence Of hoAsnRoot To iSuccess
    Get ComAppendBits Of hoAsnRoot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hex" To iSuccess

    // ----------------------------------
    // Build the Certificate Request Info
    // ----------------------------------
    Get ComGetSubItem Of hoAsnRoot 0 To vAsnCertReqInfo
    If (IsComObject(vAsnCertReqInfo)) Begin
        Get Create (RefClass(cComChilkatAsn)) To hoAsnCertReqInfo
        Set pvComObject Of hoAsnCertReqInfo To vAsnCertReqInfo
    End
    Get ComAppendInt Of hoAsnCertReqInfo 0 To iSuccess

    // Build the Subject part of the Certificate Request Info
    Get ComAppendSequenceR Of hoAsnCertReqInfo To vAsnCertSubject
    If (IsComObject(vAsnCertSubject)) Begin
        Get Create (RefClass(cComChilkatAsn)) To hoAsnCertSubject
        Set pvComObject Of hoAsnCertSubject To vAsnCertSubject
    End

    // Add each subject part..
    Get ComAppendSetR Of hoAsnCertSubject To vAsnTemp
    If (IsComObject(vAsnTemp)) Begin
        Get Create (RefClass(cComChilkatAsn)) To hoAsnTemp
        Set pvComObject Of hoAsnTemp To vAsnTemp
    End
    Get ComAppendSequence2 Of hoAsnTemp To iSuccess
    // AppendSequence2 updates the internal reference to the newly appended SEQUENCE.
    // The OID and printable string are added to the SEQUENCE.
    Get ComAppendOid Of hoAsnTemp "2.5.4.6" To iSuccess
    Get ComAppendString Of hoAsnTemp "printable" "US" To iSuccess
    Send Destroy of hoAsnTemp

    Get ComAppendSetR Of hoAsnCertSubject To vAsnTemp
    If (IsComObject(vAsnTemp)) Begin
        Get Create (RefClass(cComChilkatAsn)) To hoAsnTemp
        Set pvComObject Of hoAsnTemp To vAsnTemp
    End
    Get ComAppendSequence2 Of hoAsnTemp To iSuccess
    Get ComAppendOid Of hoAsnTemp "2.5.4.8" To iSuccess
    Get ComAppendString Of hoAsnTemp "utf8" "Utah" To iSuccess
    Send Destroy of hoAsnTemp

    Get ComAppendSetR Of hoAsnCertSubject To vAsnTemp
    If (IsComObject(vAsnTemp)) Begin
        Get Create (RefClass(cComChilkatAsn)) To hoAsnTemp
        Set pvComObject Of hoAsnTemp To vAsnTemp
    End
    Get ComAppendSequence2 Of hoAsnTemp To iSuccess
    Get ComAppendOid Of hoAsnTemp "2.5.4.7" To iSuccess
    Get ComAppendString Of hoAsnTemp "utf8" "Lindon" To iSuccess
    Send Destroy of hoAsnTemp

    Get ComAppendSetR Of hoAsnCertSubject To vAsnTemp
    If (IsComObject(vAsnTemp)) Begin
        Get Create (RefClass(cComChilkatAsn)) To hoAsnTemp
        Set pvComObject Of hoAsnTemp To vAsnTemp
    End
    Get ComAppendSequence2 Of hoAsnTemp To iSuccess
    Get ComAppendOid Of hoAsnTemp "2.5.4.10" To iSuccess
    Get ComAppendString Of hoAsnTemp "utf8" "DigiCert Inc." To iSuccess
    Send Destroy of hoAsnTemp

    Get ComAppendSetR Of hoAsnCertSubject To vAsnTemp
    If (IsComObject(vAsnTemp)) Begin
        Get Create (RefClass(cComChilkatAsn)) To hoAsnTemp
        Set pvComObject Of hoAsnTemp To vAsnTemp
    End
    Get ComAppendSequence2 Of hoAsnTemp To iSuccess
    Get ComAppendOid Of hoAsnTemp "2.5.4.11" To iSuccess
    Get ComAppendString Of hoAsnTemp "utf8" "DigiCert" To iSuccess
    Send Destroy of hoAsnTemp

    Get ComAppendSetR Of hoAsnCertSubject To vAsnTemp
    If (IsComObject(vAsnTemp)) Begin
        Get Create (RefClass(cComChilkatAsn)) To hoAsnTemp
        Set pvComObject Of hoAsnTemp To vAsnTemp
    End
    Get ComAppendSequence2 Of hoAsnTemp To iSuccess
    Get ComAppendOid Of hoAsnTemp "2.5.4.3" To iSuccess
    Get ComAppendString Of hoAsnTemp "utf8" "example.digicert.com" To iSuccess
    Send Destroy of hoAsnTemp

    Send Destroy of hoAsnCertSubject

    // Build the Public Key Info part of the Certificate Request Info
    Get ComAppendSequenceR Of hoAsnCertReqInfo To vAsnPubKeyInfo
    If (IsComObject(vAsnPubKeyInfo)) Begin
        Get Create (RefClass(cComChilkatAsn)) To hoAsnPubKeyInfo
        Set pvComObject Of hoAsnPubKeyInfo To vAsnPubKeyInfo
    End

    Get ComAppendSequenceR Of hoAsnPubKeyInfo To vAsnPubKeyAlgId
    If (IsComObject(vAsnPubKeyAlgId)) Begin
        Get Create (RefClass(cComChilkatAsn)) To hoAsnPubKeyAlgId
        Set pvComObject Of hoAsnPubKeyAlgId To vAsnPubKeyAlgId
    End
    Get ComAppendOid Of hoAsnPubKeyAlgId "1.2.840.113549.1.1.1" To iSuccess
    Get ComAppendNull Of hoAsnPubKeyAlgId To iSuccess
    Send Destroy of hoAsnPubKeyAlgId

    // The public key itself is a BIT STRING, but the bit string is composed of ASN.1
    // for the RSA public key.  We'll first build the RSA ASN.1 for the public key
    // (containing the 2048 bit modulus and exponent), and encoded it to DER, and then add
    // the DER bytes as a BIT STRING (as a sub-item of asnPubKeyInfo)

    // This is already a SEQUENCE..
    Get Create (RefClass(cComChilkatAsn)) To hoAsnRsaKey
    If (Not(IsComObjectCreated(hoAsnRsaKey))) Begin
        Send CreateComObject of hoAsnRsaKey
    End

    // The RSA modulus is a big integer.
    Get ComAppendBigInt Of hoAsnRsaKey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hex" To iSuccess
    Get ComAppendInt Of hoAsnRsaKey 65537 To iSuccess

    Get ComGetEncodedDer Of hoAsnRsaKey "base64" To sRsaKeyDerBase64

    // Now add the RSA key DER as a BIT STRING.
    Get ComAppendBits Of hoAsnPubKeyInfo sRsaKeyDerBase64 "base64" To iSuccess
    Send Destroy of hoAsnPubKeyInfo

    // The last part of the certificate request info is an empty context-specific constructed item
    // with a tag equal to 0.
    Get ComAppendContextConstructed Of hoAsnCertReqInfo 0 To iSuccess

    Send Destroy of hoAsnCertReqInfo

    // ----------------------------------
    // Finally, add the algorithm identifier, which is the 2nd sub-item under the root.
    // ----------------------------------
    Get ComGetSubItem Of hoAsnRoot 1 To vAsnAlgId
    If (IsComObject(vAsnAlgId)) Begin
        Get Create (RefClass(cComChilkatAsn)) To hoAsnAlgId
        Set pvComObject Of hoAsnAlgId To vAsnAlgId
    End
    Get ComAppendOid Of hoAsnAlgId "1.2.840.113549.1.1.5" To iSuccess
    Get ComAppendNull Of hoAsnAlgId To iSuccess
    Send Destroy of hoAsnAlgId

    // Write the CSR to a DER encoded binary file:
    Get ComWriteBinaryDer Of hoAsnRoot "qa_output/csr.der" To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoAsnRoot To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // It is also possible to get the CSR in base64 format:
    Get ComGetEncodedDer Of hoAsnRoot "base64" To sCsrBase64

    Showln "Base64 CSR:"
    Showln sCsrBase64

    // To emit as PEM:
    // (Note: The pem.AddItem method was added in Chilkat v9.5.0.59)
    Get Create (RefClass(cComChilkatPem)) To hoPem
    If (Not(IsComObjectCreated(hoPem))) Begin
        Send CreateComObject of hoPem
    End
    Get ComAddItem Of hoPem "csr" "base64" sCsrBase64 To iSuccess
    Showln "PEM:"
    Get ComToPem Of hoPem To sTemp1
    Showln sTemp1


End_Procedure