닷넷(C#) 코드로 인증서 요청 코드 만드는 방법

인터넷 떠돌다가 본 코드인데,

How to create a certificate request with CertEnroll and .NET (C#)
; https://learn.microsoft.com/en-us/archive/blogs/alejacma/how-to-create-a-certificate-request-with-certenroll-and-net-c

Cipher selection for sslStream in .NET 4.5
; http://stackoverflow.com/questions/22825663/cipher-selection-for-sslstream-in-net-4-5

저도 실습해봤습니다. ^^ C# 프로젝트를 하나 만들고 "CertEnroll 1.0 Type Library" 참조 추가를 한 다음 위의 코드를 거의 그대로 베끼면 됩니다.

using System;
using CERTENROLLLib;
using System.Security.Cryptography.X509Certificates;

namespace ConsoleApp1
{
    class Program
    {
        public static string GenerateRequest(string Subject, StoreLocation Location, string providerName, int KeyLength)
        {
            //code originally came from: http://blogs.msdn.com/b/alejacma/archive/2008/09/05/how-to-create-a-certificate-request-with-certenroll-and-net-c.aspx
            //modified version of it is here: http://stackoverflow.com/questions/16755634/issue-generating-a-csr-in-windows-vista-cx509certificaterequestpkcs10
            //here is the standard for certificates: http://www.ietf.org/rfc/rfc3280.txt


            //the PKCS#10 certificate request (https://learn.microsoft.com/en-us/windows/win32/api/certenroll/nn-certenroll-ix509certificaterequestpkcs10)
            CX509CertificateRequestPkcs10 objPkcs10 = new CX509CertificateRequestPkcs10();

            //assymetric private key that can be used for encryption (https://learn.microsoft.com/en-us/windows/win32/api/certenroll/nn-certenroll-ix509privatekey)
            CX509PrivateKey objPrivateKey = new CX509PrivateKey();

            //access to the general information about a cryptographic provider (https://learn.microsoft.com/en-us/windows/win32/api/certenroll/nn-certenroll-icspinformation)
            CCspInformation objCSP = new CCspInformation();

            //collection on cryptographic providers available: https://learn.microsoft.com/en-us/windows/win32/api/certenroll/nn-certenroll-icspinformation
            CCspInformations objCSPs = new CCspInformations();

            CX500DistinguishedName objDN = new CX500DistinguishedName();

            //top level object that enables installing a certificate response https://learn.microsoft.com/en-us/windows/win32/api/certenroll/nn-certenroll-ix509enrollment
            CX509Enrollment objEnroll = new CX509Enrollment();
            CObjectIds objObjectIds = new CObjectIds();
            CObjectId objObjectId = new CObjectId();
            CObjectId objObjectId2 = new CObjectId();
            CX509ExtensionKeyUsage objExtensionKeyUsage = new CX509ExtensionKeyUsage();
            CX509ExtensionEnhancedKeyUsage objX509ExtensionEnhancedKeyUsage = new CX509ExtensionEnhancedKeyUsage();

            string csr_pem = null;

            //  Initialize the csp object using the desired Cryptograhic Service Provider (CSP)
            objCSPs.AddAvailableCsps();

            //Provide key container name, key length and key spec to the private key object
            objPrivateKey.ProviderName = providerName;
            objPrivateKey.Length = KeyLength;
            objPrivateKey.KeySpec = X509KeySpec.XCN_AT_KEYEXCHANGE; //Must flag as XCN_AT_KEYEXCHANGE to use this certificate for exchanging symmetric keys (needed for most SSL cipher suites)
            objPrivateKey.KeyUsage = X509PrivateKeyUsageFlags.XCN_NCRYPT_ALLOW_ALL_USAGES;
            if (Location == StoreLocation.LocalMachine)
                objPrivateKey.MachineContext = true;
            else
                objPrivateKey.MachineContext = false; //must set this to true if installing to the local machine certificate store

            objPrivateKey.ExportPolicy = X509PrivateKeyExportFlags.XCN_NCRYPT_ALLOW_EXPORT_FLAG;    //must set this if we want to be able to export it later. 
            objPrivateKey.CspInformations = objCSPs;

            //  Create the actual key pair
            objPrivateKey.Create();

            //  Initialize the PKCS#10 certificate request object based on the private key.
            //  Using the context, indicate that this is a user certificate request and don't
            //  provide a template name
            if (Location == StoreLocation.LocalMachine)
                objPkcs10.InitializeFromPrivateKey(X509CertificateEnrollmentContext.ContextMachine, objPrivateKey, "");
            else
                objPkcs10.InitializeFromPrivateKey(X509CertificateEnrollmentContext.ContextUser, objPrivateKey, "");

            //Set hash to sha256
            CObjectId hashobj = new CObjectId();
            hashobj.InitializeFromAlgorithmName(ObjectIdGroupId.XCN_CRYPT_HASH_ALG_OID_GROUP_ID, ObjectIdPublicKeyFlags.XCN_CRYPT_OID_INFO_PUBKEY_ANY, AlgorithmFlags.AlgorithmFlagsNone, "SHA256");
            objPkcs10.HashAlgorithm = hashobj;

            // Key Usage Extension -- we only need digital signature and key encipherment for TLS:
            //  NOTE: in openSSL, I didn't used to request any specific extensions. Instead, I let the CA add them
            objExtensionKeyUsage.InitializeEncode(
                CERTENROLLLib.X509KeyUsageFlags.XCN_CERT_DIGITAL_SIGNATURE_KEY_USAGE |
                CERTENROLLLib.X509KeyUsageFlags.XCN_CERT_KEY_ENCIPHERMENT_KEY_USAGE
            );
            objPkcs10.X509Extensions.Add((CX509Extension)objExtensionKeyUsage);

            // Enhanced Key Usage Extension
            objObjectId.InitializeFromValue("1.3.6.1.5.5.7.3.1"); // OID for Server Authentication usage (see this: http://stackoverflow.com/questions/17477279/client-authentication-1-3-6-1-5-5-7-3-2-oid-in-server-certificates)
            objObjectId2.InitializeFromValue("1.3.6.1.5.5.7.3.2"); // OID for Client Authentication usage (see this: http://stackoverflow.com/questions/17477279/client-authentication-1-3-6-1-5-5-7-3-2-oid-in-server-certificates)
            objObjectIds.Add(objObjectId);
            objObjectIds.Add(objObjectId2);
            objX509ExtensionEnhancedKeyUsage.InitializeEncode(objObjectIds);
            objPkcs10.X509Extensions.Add((CX509Extension)objX509ExtensionEnhancedKeyUsage);

            //  Encode the name in using the Distinguished Name object
            // see here: http://https://learn.microsoft.com/en-us/windows/win32/api/certenroll/ne-certenroll-x500nameflags
            objDN.Encode(Subject, X500NameFlags.XCN_CERT_NAME_STR_SEMICOLON_FLAG);

            // Assign the subject name by using the Distinguished Name object initialized above
            objPkcs10.Subject = objDN;

            //suppress extra attributes:
            objPkcs10.SuppressDefaults = true;

            // Create enrollment request
            // objEnroll.InitializeFromTemplateName(X509CertificateEnrollmentContext.ContextMachine, "WebServer");
            objEnroll.InitializeFromRequest(objPkcs10);
            csr_pem = objEnroll.CreateRequest(EncodingType.XCN_CRYPT_STRING_BASE64);
            csr_pem = "-----BEGIN CERTIFICATE REQUEST-----\r\n" + csr_pem + "-----END CERTIFICATE REQUEST-----";

            return csr_pem;
        }
    }
}

사용을 위한 호출은 이렇게 간단합니다. ^^

static void Main(string[] args)
{
    string txt = GenerateRequest("CN=the10", StoreLocation.CurrentUser, "Microsoft RSA SChannel Cryptographic Provider", 1024);
    Console.WriteLine(txt);
}

출력된 txt 내용은 이렇게 나옵니다.

-----BEGIN CERTIFICATE REQUEST-----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-----END CERTIFICATE REQUEST-----

그러니까 위의 코드는 결국 다음의 글에서 설명한,

2. 웹 사이트에 SSL 을 적용
; https://www.sysnet.pe.kr/2/0/372

1번 단계인 "IIS 관리자에서 인증서 서비스로 보낼 '요청 파일' 준비"를 한 것입니다.

---

실제로 위의 코드가 생산한 CSR 내용으로 인증서를 발급받아 볼까요? ^^ 정식 인증서 업체로는 곤란하니, Windows 서버에 인증서 서비스를 설치한 다음 CA 관리 콘솔을 띄웁니다.

다음 그림에서 보는 것처럼,



CA 서버 명 노드를 마우스 우 클릭해 "All Tasks" / "Submit new request..." 메뉴를 선택하면 파일 선택 대화창이 뜹니다. 그럼, 위의 "-----BEGIN CERTIFICATE REQUEST----- ... -----END CERTIFICATE REQUEST-----" 내용을 파일로 저장한 것을 선택해 줍니다.

선택하자마자, CA 서비스는 해당 인증서 요청을 "Pending Requests"에 보관합니다.



그럼, 위의 인증서에 마우스 우 클릭하고 "All Tasks" / "Issue" 메뉴를 눌러 명시적인 발급을 하면 곧바로 "Pending Requests"에는 사라지고 "Issued Certificates" 영역으로 이동합니다.

결국 다음과 같은 인증서를 확인할 수 있습니다. ^^



정말 잘 되는군요. ^^

(첨부 파일은 이 글의 예제 코드를 포함합니다.)

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참고로, Active Directory가 설치된 Enterprise CA 서비스에 이 글의 CSR 내용을 전달하면 다음과 같은 오류를 만나게 됩니다.



원인은 이렇고,

You may receive a "The request contains no certificate template information" error message when you submit a CSR to an enterprise CA by using the Certification Authority Microsoft Management Console (MMC) snap-in in Windows Server 2003
; https://support.microsoft.com/en-us/help/910249/you-may-receive-a-the-request-contains-no-certificate-template-information-error-message-when-you-submit-a-csr-to-an-enterprise-ca-by-using-the-certification-authority-microsoft-management-console-mmc-snap-in-in-windows-server-2003

따라서, 인증서 템플릿을 반드시 지정해야 합니다.

방법을 찾아보니, CX509Enrollment 객체에 InitializeFromTemplateName 메서드가 제공되는데요. 아마도 "objEnroll.InitializeFromRequest(objPkcs10);" 호출 대신 "objEnroll.InitializeFromTemplateName(X509CertificateEnrollmentContext.ContextMachine, "WebServer");"라는 식으로 호출해야 할 듯!

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[이 글에 대해서 여러분들과 의견을 공유하고 싶습니다. 틀리거나 미흡한 부분 또는 의문 사항이 있으시면 언제든 댓글 남겨주십시오.]

[최초 등록일: 3/21/2017]
[최종 수정일: 6/11/2023]


이 저작물은 크리에이티브 커먼즈 코리아 저작자표시-비영리-변경금지 2.0 대한민국 라이센스에 따라 이용하실 수 있습니다.

by SeongTae Jeong, mailto:techsharer at outlook.com