(Go) Generate a CSR with keyUsage, extKeyUsage, and other Extensions

See more CSR Examples

Demonstrates how to generate a CSR containing a 1.2.840.113549.1.9.14 extensionRequest with the following extensions:

• 1.3.6.1.4.1.311.20.2 enrollCerttypeExtension
• 2.5.29.15 keyUsage
• 2.5.29.37 extKeyUsage
• 2.5.29.14 subjectKeyIdentifier

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

    // This example will generate a secp256r1 ECDSA key for the CSR.
    ecc := chilkat.NewEcc()
    prng := chilkat.NewPrng()

    privKey := ecc.GenEccKey("secp256r1",prng)
    if ecc.LastMethodSuccess() == false {
        fmt.Println("Failed to generate a new ECDSA private key.")
        ecc.DisposeEcc()
        prng.DisposePrng()
        return
    }

    csr := chilkat.NewCsr()

    // Add common CSR fields:
    csr.SetCommonName("mysubdomain.mydomain.com")
    csr.SetCountry("GB")
    csr.SetState("Yorks")
    csr.SetLocality("York")
    csr.SetCompany("Internet Widgits Pty Ltd")
    csr.SetEmailAddress("support@mydomain.com")

    // Add the following 1.2.840.113549.1.9.14 extensionRequest
    // Note: The easiest way to know the content and format of the XML to be added is to examine
    // a pre-existing CSR with the same desired extensionRequest.  You can use Chilkat to
    // get the extensionRequest from an existing CSR. 

    // 
    // Here is a sample extension request:

    // <?xml version="1.0" encoding="utf-8"?>
    // <set>
    //     <sequence>
    //         <sequence>
    //             <oid>1.3.6.1.4.1.311.20.2</oid>
    //             <asnOctets>
    //                 <universal tag="30" constructed="0">AEUAbgBkAEUAbgB0AGkAdAB5AEMAbABpAGUAbgB0AEEAdQB0AGgAQwBlAHIAdABpAGYAaQBjAGEAdABl
    // AF8AQwBTAFIAUABhAHMAcwB0AGgAcgBvAHUAZwBoAC8AVgAx</universal>
    //             </asnOctets>
    //         </sequence>
    //         <sequence>
    //             <oid>2.5.29.15</oid>
    //             <bool>1</bool>
    //             <asnOctets>
    //                 <bits n="3">A0</bits>
    //             </asnOctets>
    //         </sequence>
    //         <sequence>
    //             <oid>2.5.29.37</oid>
    //             <asnOctets>
    //                 <sequence>
    //                     <oid>1.3.6.1.5.5.7.3.3</oid>
    //                 </sequence>
    //             </asnOctets>
    //         </sequence>
    //         <sequence>
    //             <oid>2.5.29.14</oid>
    //             <asnOctets>
    //                 <octets>MCzBMQAViXBz8IDt8LsgmJxJ4Xg=</octets>
    //             </asnOctets>
    //         </sequence>
    //     </sequence>
    // </set>

    // Use this online tool to generate code from sample XML: 
    // Generate Code to Create XML

    // A few notes:
    // The string "AEUAbgBkAEUAbgB0AGkAdAB5AEMAbABpAGUAbgB0AEEAdQB0AGgAQwBlAHIAdABpAGYAaQBjAGEAdABlAF8AQwBTAFIAUABhAHMAcwB0AGgAcgBvAHUAZwBoAC8AVgAx"
    // is the base64 encoding of the utf-16be byte representation of the string "EndEntityClientAuthCertificate_CSRPassthrough/V1"

    s := "EndEntityClientAuthCertificate_CSRPassthrough/V1"
    bdTemp := chilkat.NewBinData()
    bdTemp.AppendString(s,"utf-16be")
    s_base64_utf16be := bdTemp.GetEncoded("base64")
    // The string should be "AEUA....."
    fmt.Println(*s_base64_utf16be)

    // Here's the code to generate the above extension request.

    xml := chilkat.NewXml()
    xml.SetTag("set")
    xml.UpdateChildContent("sequence|sequence|oid","1.3.6.1.4.1.311.20.2")
    xml.UpdateAttrAt("sequence|sequence|asnOctets|universal",true,"tag","30")
    xml.UpdateAttrAt("sequence|sequence|asnOctets|universal",true,"constructed","0")
    xml.UpdateChildContent("sequence|sequence|asnOctets|universal",*s_base64_utf16be)
    xml.UpdateChildContent("sequence|sequence[1]|oid","2.5.29.15")
    xml.UpdateChildContent("sequence|sequence[1]|bool","1")
    xml.UpdateAttrAt("sequence|sequence[1]|asnOctets|bits",true,"n","3")
    // A0 is hex for decimal 160.
    xml.UpdateChildContent("sequence|sequence[1]|asnOctets|bits","A0")
    xml.UpdateChildContent("sequence|sequence[2]|oid","2.5.29.37")
    xml.UpdateChildContent("sequence|sequence[2]|asnOctets|sequence|oid","1.3.6.1.5.5.7.3.3")

    // This is the subjectKeyIdentifier extension.
    // The string "MCzBMQAViXBz8IDt8LsgmJxJ4Xg=" is base64 that decodes to 20 bytes, which is a SHA1 hash.
    // This is simply a hash of the DER of the public key.

    pubKey := privKey.GetPublicKey()
    bdPubKeyDer := chilkat.NewBinData()
    bdPubKeyDer.AppendEncoded(*pubKey.GetEncoded(true,"base64"),"base64")
    ski := bdPubKeyDer.GetHash("sha1","base64")
    pubKey.DisposePublicKey()

    xml.UpdateChildContent("sequence|sequence[3]|oid","2.5.29.14")
    xml.UpdateChildContent("sequence|sequence[3]|asnOctets|octets",*ski)

    // Add the extension request to the CSR
    csr.SetExtensionRequest(xml)

    // Generate the CSR with the extension request
    csrPem := csr.GenCsrPem(privKey)
    if csr.LastMethodSuccess() == false {
        fmt.Println(csr.LastErrorText())
        privKey.DisposePrivateKey()
        ecc.DisposeEcc()
        prng.DisposePrng()
        csr.DisposeCsr()
        bdTemp.DisposeBinData()
        xml.DisposeXml()
        bdPubKeyDer.DisposeBinData()
        return
    }

    fmt.Println(*csrPem)

    privKey.DisposePrivateKey()

    ecc.DisposeEcc()
    prng.DisposePrng()
    csr.DisposeCsr()
    bdTemp.DisposeBinData()
    xml.DisposeXml()
    bdPubKeyDer.DisposeBinData()