(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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#include <CkEcc.h>
#include <CkPrng.h>
#include <CkPrivateKey.h>
#include <CkCsr.h>
#include <CkBinData.h>
#include <CkXml.h>
#include <CkPublicKey.h>

void ChilkatSample(void)
    {
    // 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.
    CkEcc ecc;
    CkPrng prng;

    CkPrivateKey *privKey = ecc.GenEccKey("secp256r1",prng);
    if (ecc.get_LastMethodSuccess() == false) {
        std::cout << "Failed to generate a new ECDSA private key." << "\r\n";
        return;
    }

    CkCsr csr;

    // Add common CSR fields:
    csr.put_CommonName("mysubdomain.mydomain.com");
    csr.put_Country("GB");
    csr.put_State("Yorks");
    csr.put_Locality("York");
    csr.put_Company("Internet Widgits Pty Ltd");
    csr.put_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"

    const char *s = "EndEntityClientAuthCertificate_CSRPassthrough/V1";
    CkBinData bdTemp;
    bdTemp.AppendString(s,"utf-16be");
    const char *s_base64_utf16be = bdTemp.getEncoded("base64");
    // The string should be "AEUA....."
    std::cout << s_base64_utf16be << "\r\n";

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

    CkXml xml;
    xml.put_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.

    CkPublicKey *pubKey = privKey->GetPublicKey();
    CkBinData bdPubKeyDer;
    bdPubKeyDer.AppendEncoded(pubKey->getEncoded(true,"base64"),"base64");
    const char *ski = bdPubKeyDer.getHash("sha1","base64");
    delete pubKey;

    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
    const char *csrPem = csr.genCsrPem(*privKey);
    if (csr.get_LastMethodSuccess() == false) {
        std::cout << csr.lastErrorText() << "\r\n";
        delete privKey;
        return;
    }

    std::cout << csrPem << "\r\n";

    delete privKey;
    }