X.509 certificate management in .NET

1. X.509 certificate management in .NET -Vamsi sri Harsha Vidala

2. Introduction • A public key certificate is digitally signed document that is commonly used for authentication and secure exchange of information on open networks. • A certificate securely binds a public key to the entity that holds the corresponding private key. • Certificates are digitally signed by the issuing certification authority (CA). They create a trust relationship between two unknown entities.

3. Overview of X.509 certificates Entities involved in X.509 certificate management. • Subjects and End Entities. • Certification Authority(CA). • Registration Authority(RA).

4. Certificate Management Operations Certificate Repository Cert. publish End Entity “Out-of-Band” loading Initial Registration/ Certification. Key Pair recovery. Key Pair Update. Certificate Update. Revocation Request. Cert. “USERS” Cert. Mgmt Entities RA Cert. publish “Out-of-Band” publication CA Cert. publish Cross-certification. Cross- Certificate Update. CA-2

5. Certificate Management Operations • CA establishment. • End entity initialization. • Certification: • Initial registration/Certification. • Key pair Update. • Certificate Update. • CA Key pair update. • Cross-certification Request. • Cross-certificate Update.

6. Operations(contd.) • Certificate/CRLdiscovery operations. • Certificate Publication • CRL Publication • Recovery operations • Key-pair recovery • PSE operations

7. Implementation in ASP.NET

8. Note: The most widely accepted format for certificates is defined by the ITU-T X.509 version 3 international standards. The certificates are encoded using OSI ASN.1 DER. Formats for X.509 Certificate

9. Primary Fields in X.509 certificate

10. .NET Certificate Management Tools

11. Using X.509 Certificates in .NET application • Create and manage X.509 Certificate • Sign a SOAP Message Using an X.509 Certificate • Verify Digital Signatures of SOAP Messages Signed by an X.509 Certificate

12. STEP I Create and manage X.509 Certificate

13. Obtain X.509 Certificate • Purchase a certificate from a certificate authority, such as VeriSign, Inc • Set up our own certificate service and have a certificate authority sign the certificates • Set up our own certificate service and do not have the certificates signed Note: Whichever approach we take, the recipient of the SOAP request containing the X.509 certificate must trust the X.509 certificate.

14. Creating and configuring X.509 Certificate • Create certificate using makecert.exe cmd>makecert -n "CN=TempCA" -r -sv TempCA.pvk TempCA.cer • Import the created certificate using MMC in to the certificate store Import the certificate TempCA.cer using MMC in to "Trusted Root Certificate Authorities" folder • Export the created certificate to outside world by creating and distributing pfx file using pvk2pfx tool cmd>pvk2pfx -pvk TempCA.pvk -spc TempCA.cer • Define access permission for X.509 certificate cmd>winhttpcertcfg -g -c LOCAL_MACHINE\MY -s TempCA -a ASPNET

15. Make certificates accessible to application • Specify the certificate store that application uses to obtain X.509 certificates <configuration> <microsoft.web.services2> <security> <x509 storeLocation="CurrentUser" /> </security> </microsoft.web.services2> </configuration> • Specify the account under which application is running read access to the file containing the private key associated with the X.509 certificate. <processModel enable="true|false"userName="username"  password="password" />

16. Default accessibility for certificates Default Locations of certificate store: Usage of private key:

17. STEP II Sign a SOAP Message Using an X.509 Certificate

18. Config file settings for using X.509 certificates • <policyDocumentxmlns="http://schemas.microsoft.com/wse/2003/06/Policy"> • <mappings xmlns:wse="http://schemas.microsoft.com/wse/2003/06/Policy"> • <endpoint uri="http://www.cohowinery.com/SaleWidgets.asmx"> • <defaultOperation> • <request policy="#policy-c0a22319-6b89-49ff-9b82-bdbac5f04618" /> • <response policy="#policy-c0a22319-6b89-49ff-9b82-bdbac5f04618" /> • <fault policy="#policy-c0a22319-6b89-49ff-9b82-bdbac5f04618" /> • </defaultOperation> • </endpoint> • </mappings> • <policies • … • </policies> • </policyDocument>

19. Config file settings for using X.509 certificates • <policies xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd"> • <wsp:Policy wsu:Id="policy-c0a22319-6b89-49ff-9b82-bdbac5f04618" • xmlns:wsp="http://schemas.xmlsoap.org/ws/2002/12/policy" • xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/03/addressing" > • <wssp:Integrity wsp:Usage="wsp:Required"xmlns:wssp="http://schemas.xmlsoap.org/ws/2002/12/secext"> • <wssp:TokenInfo> • <SecurityToken xmlns="http://schemas.xmlsoap.org/ws/2002/12/secext"> • <wssp:TokenType> • http://schemas.xmlsoap.org/ws/2003/12/kerberos/Kerberosv5ST • </wssp:TokenType> • <wssp:TokenIssuer>COHOWINERY</wssp:TokenIssuer> • <wssp:Claims> • <wssp:ServiceName>host/computer1@cohowinery.com</wssp:ServiceName> • </wssp:Claims> • </SecurityToken> • </wssp:TokenInfo> • <wssp:MessageParts Dialect="http://schemas.xmlsoap.org/2002/12/wsse#part"> • wsp:Body() wsp:Header(wsa:To) wsp:Header(wsa:Action) wsp:Header(wsa:MessageID) wsp:Header(wsa:From) • </wssp:MessageParts> • </wssp:Integrity> • </policies>

20. Retrieve certificate from store • public X509SecurityToken GetSecurityToken() • { • X509SecurityToken securityToken = null; • X509CertificateStore store = X509CertificateStore.CurrentUserStore( X509CertificateStore.MyStore); • bool open = store.OpenRead(); • try • { • byte[] certHash = {0x98, 0xec, 0x08, 0x4b, 0xa5, 0x7a, 0x6c, 0x2f, 0x39, 0x26, 0xb3, 0x0a, 0x58, 0xbf, 0x65, 0x25, 0x61, 0xc5, 0x64, 0x59}; • X509CertificateCollection certs = store.FindCertificateByHash(certHash); • Microsoft.Web.Services2.Security.X509.X509Certificate cert = • ((Microsoft.Web.Services2.Security.X509.X509Certificate) certs[0]); • if (cert == null) • … • else if (!cert.SupportsDigitalSignature || (cert.Key == null)) • … • else • { • securityToken = new X509SecurityToken(cert); • } • } • finally • { • if (store != null) • store.Close(); • } • return securityToken; • }

21. Code for signing SOAP messages • Call GetSecurityToken() to retrieve certificate X509SecurityToken signatureToken = GetSecurityToken(); • Get the SoapContext method for the SOAP request made to the Web service. Service1 svc = new Service1(); SoapContext requestContext = svc.RequestSoapContext; • Add the client's X.509 certificate to the SOAP header.requestContext.Security.Tokens.Add(signatureToken); • Create a new instance of the MessageSignature class by using the X.509 certificate just added to the SOAP header. MessageSignature sig = new MessageSignature(signatureToken); • Add the digital signature to the SOAP header. RequestContext.Security.Elements.Add(sig); • Specify the TTL for the SOAP message requestContext.Security.Timestamp.TtlInSeconds = 60; • Call the Web service. svc.sayHello();

22. STEP III Verify Digital Signatures of SOAP Messages Signed by an X.509 Certificate

23. Configure application to validate digital signatures for incoming SOAP messages • Export and Import the CA certificate chain • Add a reference to the Microsoft.Web.Services2 assembly • When the SOAP message recipient is a Web service client, this configuration entry is not required. Else configure web.config as below: • <configuration> • <system.web> • <webServices> • <soapExtensionTypes> • <add type="Microsoft.Web.Services2.WebServicesExtension, • Microsoft.Web.Services2,Version=2.0.0.0, Culture=neutral, • PublicKeyToken=31bf3856ad364e35" • priority="1" group="0"/> • </soapExtensionTypes> • </webServices> • </system.web> • </configuration>

24. Code to verify if SOAP Body is signed public string CheckSOAPBody() { SoapContext requestContext = RequestSoapContext.Current; // Verify that a SOAP request was received. if (requestContext == null) { throw new ApplicationException("Either a non-SOAP " + "request was received or WSE is not properly " + "installed for the Web application hosting the " + "Web service."); } // Check if the Soap Message is Signed. if (!IsMessageSigned(requestContext)) { throw new ApplicationException("The request is not signed."); } return "sucess"; }

25. Code to verify digital signature of SOAP request private bool IsMessageSigned(SoapContext context) { foreach (ISecurityElement element in context.Security.Elements) { if (element is MessageSignature) { // The given context contains a Signature element. MessageSignature sig = element as MessageSignature; if ((sig.SignatureOptions & SignatureOptions.IncludeSoapBody) != 0) { // The SOAP Body is signed. return true; } } } return false; }

26. References http://www.ietf.org/rfc/rfc2510.txt http://msdn.microsoft.com/en-us/library/system.security.cryptography.x509certificates.x509certificate(VS.71).aspx http://msdn.microsoft.com/en-us/library/ms820022.aspx http://support.microsoft.com/kb/315588 http://msdn.microsoft.com/en-us/library/ms819944.aspx http://www.codeproject.com/KB/cpp/X509Certificate.aspx http://www.codeproject.com/KB/WCF/Senthil.aspx