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

See more ASN.1 Examples

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:

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integer li_rc
integer li_Success
oleobject loo_AsnRoot
oleobject loo_AsnCertReqInfo
oleobject loo_AsnCertSubject
oleobject loo_AsnTemp
oleobject loo_AsnPubKeyInfo
oleobject loo_AsnPubKeyAlgId
oleobject loo_AsnRsaKey
string ls_RsaKeyDerBase64
oleobject loo_AsnAlgId
string ls_CsrBase64
oleobject loo_Pem

li_Success = 0

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

li_Success = 0

// 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.
loo_AsnRoot = create oleobject
li_rc = loo_AsnRoot.ConnectToNewObject("Chilkat.Asn")
if li_rc < 0 then
    destroy loo_AsnRoot
    MessageBox("Error","Connecting to COM object failed")
    return
end if

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

li_Success = loo_AsnRoot.AppendSequence()
li_Success = loo_AsnRoot.AppendSequence()
li_Success = loo_AsnRoot.AppendBits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hex")

// ----------------------------------
// Build the Certificate Request Info
// ----------------------------------
loo_AsnCertReqInfo = loo_AsnRoot.GetSubItem(0)
li_Success = loo_AsnCertReqInfo.AppendInt(0)

// Build the Subject part of the Certificate Request Info
loo_AsnCertSubject = loo_AsnCertReqInfo.AppendSequenceR()

// Add each subject part..
loo_AsnTemp = loo_AsnCertSubject.AppendSetR()
li_Success = loo_AsnTemp.AppendSequence2()
// AppendSequence2 updates the internal reference to the newly appended SEQUENCE.
// The OID and printable string are added to the SEQUENCE.
li_Success = loo_AsnTemp.AppendOid("2.5.4.6")
li_Success = loo_AsnTemp.AppendString("printable","US")
destroy loo_AsnTemp

loo_AsnTemp = loo_AsnCertSubject.AppendSetR()
li_Success = loo_AsnTemp.AppendSequence2()
li_Success = loo_AsnTemp.AppendOid("2.5.4.8")
li_Success = loo_AsnTemp.AppendString("utf8","Utah")
destroy loo_AsnTemp

loo_AsnTemp = loo_AsnCertSubject.AppendSetR()
li_Success = loo_AsnTemp.AppendSequence2()
li_Success = loo_AsnTemp.AppendOid("2.5.4.7")
li_Success = loo_AsnTemp.AppendString("utf8","Lindon")
destroy loo_AsnTemp

loo_AsnTemp = loo_AsnCertSubject.AppendSetR()
li_Success = loo_AsnTemp.AppendSequence2()
li_Success = loo_AsnTemp.AppendOid("2.5.4.10")
li_Success = loo_AsnTemp.AppendString("utf8","DigiCert Inc.")
destroy loo_AsnTemp

loo_AsnTemp = loo_AsnCertSubject.AppendSetR()
li_Success = loo_AsnTemp.AppendSequence2()
li_Success = loo_AsnTemp.AppendOid("2.5.4.11")
li_Success = loo_AsnTemp.AppendString("utf8","DigiCert")
destroy loo_AsnTemp

loo_AsnTemp = loo_AsnCertSubject.AppendSetR()
li_Success = loo_AsnTemp.AppendSequence2()
li_Success = loo_AsnTemp.AppendOid("2.5.4.3")
li_Success = loo_AsnTemp.AppendString("utf8","example.digicert.com")
destroy loo_AsnTemp

destroy loo_AsnCertSubject

// Build the Public Key Info part of the Certificate Request Info
loo_AsnPubKeyInfo = loo_AsnCertReqInfo.AppendSequenceR()

loo_AsnPubKeyAlgId = loo_AsnPubKeyInfo.AppendSequenceR()
li_Success = loo_AsnPubKeyAlgId.AppendOid("1.2.840.113549.1.1.1")
li_Success = loo_AsnPubKeyAlgId.AppendNull()
destroy loo_AsnPubKeyAlgId

// 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..
loo_AsnRsaKey = create oleobject
li_rc = loo_AsnRsaKey.ConnectToNewObject("Chilkat.Asn")

// The RSA modulus is a big integer.
li_Success = loo_AsnRsaKey.AppendBigInt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hex")
li_Success = loo_AsnRsaKey.AppendInt(65537)

ls_RsaKeyDerBase64 = loo_AsnRsaKey.GetEncodedDer("base64")

// Now add the RSA key DER as a BIT STRING.
li_Success = loo_AsnPubKeyInfo.AppendBits(ls_RsaKeyDerBase64,"base64")
destroy loo_AsnPubKeyInfo

// The last part of the certificate request info is an empty context-specific constructed item
// with a tag equal to 0.
li_Success = loo_AsnCertReqInfo.AppendContextConstructed(0)

destroy loo_AsnCertReqInfo

// ----------------------------------
// Finally, add the algorithm identifier, which is the 2nd sub-item under the root.
// ----------------------------------
loo_AsnAlgId = loo_AsnRoot.GetSubItem(1)
li_Success = loo_AsnAlgId.AppendOid("1.2.840.113549.1.1.5")
li_Success = loo_AsnAlgId.AppendNull()
destroy loo_AsnAlgId

// Write the CSR to a DER encoded binary file:
li_Success = loo_AsnRoot.WriteBinaryDer("qa_output/csr.der")
if li_Success <> 1 then
    Write-Debug loo_AsnRoot.LastErrorText
    destroy loo_AsnRoot
    destroy loo_AsnRsaKey
    return
end if

// It is also possible to get the CSR in base64 format:
ls_CsrBase64 = loo_AsnRoot.GetEncodedDer("base64")

Write-Debug "Base64 CSR:"
Write-Debug ls_CsrBase64

// To emit as PEM:
// (Note: The pem.AddItem method was added in Chilkat v9.5.0.59)
loo_Pem = create oleobject
li_rc = loo_Pem.ConnectToNewObject("Chilkat.Pem")

loo_Pem.AddItem("csr","base64",ls_CsrBase64)
Write-Debug "PEM:"
Write-Debug loo_Pem.ToPem()


destroy loo_AsnRoot
destroy loo_AsnRsaKey
destroy loo_Pem