(.NET Core C#) 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.
Chilkat.Ecc ecc = new Chilkat.Ecc();
Chilkat.Prng prng = new Chilkat.Prng();

Chilkat.PrivateKey privKey = ecc.GenEccKey("secp256r1",prng);
if (ecc.LastMethodSuccess == false) {
    Debug.WriteLine("Failed to generate a new ECDSA private key.");
    return;
}

Chilkat.Csr csr = new Chilkat.Csr();

// Add common CSR fields:
csr.CommonName = "mysubdomain.mydomain.com";
csr.Country = "GB";
csr.State = "Yorks";
csr.Locality = "York";
csr.Company = "Internet Widgits Pty Ltd";
csr.EmailAddress = "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"

string s = "EndEntityClientAuthCertificate_CSRPassthrough/V1";
Chilkat.BinData bdTemp = new Chilkat.BinData();
bdTemp.AppendString(s,"utf-16be");
string s_base64_utf16be = bdTemp.GetEncoded("base64");
// The string should be "AEUA....."
Debug.WriteLine(s_base64_utf16be);

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

Chilkat.Xml xml = new Chilkat.Xml();
xml.Tag = "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.

Chilkat.PublicKey pubKey = privKey.GetPublicKey();
Chilkat.BinData bdPubKeyDer = new Chilkat.BinData();
bdPubKeyDer.AppendEncoded(pubKey.GetEncoded(true,"base64"),"base64");
string ski = bdPubKeyDer.GetHash("sha1","base64");

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
string csrPem = csr.GenCsrPem(privKey);
if (csr.LastMethodSuccess == false) {
    Debug.WriteLine(csr.LastErrorText);

    return;
}

Debug.WriteLine(csrPem);