_KerberosClient.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Net / System / Net / _KerberosClient.cs / 1305376 / _KerberosClient.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Net { 
    using System.Collections; 
    using System.Net.Sockets;
    using System.Security.Authentication.ExtendedProtection; 
    using System.Security.Permissions;
    using System.Globalization;

    internal class KerberosClient : ISessionAuthenticationModule { 

        internal const string AuthType = "Kerberos"; 
        internal static string Signature = AuthType.ToLower(CultureInfo.InvariantCulture); 
        internal static int SignatureSize = Signature.Length;
 
        // we can't work on non-NT platforms, so we shut off with an exception
        // NOTE this exception IS caught internally.
        internal KerberosClient() {
            if (!ComNetOS.IsWin2K) { 
                throw new PlatformNotSupportedException(SR.GetString(SR.Win2000Required));
            } 
        } 

        public Authorization Authenticate(string challenge, WebRequest webRequest, ICredentials credentials) { 
            GlobalLog.Print("KerberosClient::Authenticate() challenge:[" + ValidationHelper.ToString(challenge) + "] webRequest#" + ValidationHelper.HashString(webRequest) + " credentials#" + ValidationHelper.HashString(credentials) + " calling DoAuthenticate()");
            return DoAuthenticate(challenge, webRequest, credentials, false);
        }
 

        private Authorization DoAuthenticate(string challenge, WebRequest webRequest, ICredentials credentials, bool preAuthenticate) { 
            GlobalLog.Print("KerberosClient::DoAuthenticate() challenge:[" + ValidationHelper.ToString(challenge) + "] webRequest#" + ValidationHelper.HashString(webRequest) + " credentials#" + ValidationHelper.HashString(credentials) + " preAuthenticate:" + preAuthenticate.ToString()); 

            GlobalLog.Assert(credentials != null, "KerberosClient::DoAuthenticate()|credentials == null"); 
            if (credentials == null) {
                return null;
            }
 
            HttpWebRequest httpWebRequest = webRequest as HttpWebRequest;
 
            GlobalLog.Assert(httpWebRequest != null, "KerberosClient::DoAuthenticate()|httpWebRequest == null"); 
            GlobalLog.Assert(httpWebRequest.ChallengedUri != null, "KerberosClient::DoAuthenticate()|httpWebRequest.ChallengedUri == null");
 
            NTAuthentication authSession = null;
            string incoming = null;

            if (!preAuthenticate) { 
                int index = AuthenticationManager.FindSubstringNotInQuotes(challenge, Signature);
                if (index < 0) { 
                    return null; 
                }
 
                int blobBegin = index + SignatureSize;

                //
                // there may be multiple challenges. If the next character after the 
                // package name is not a comma then it is challenge data
                // 
                if (challenge.Length > blobBegin && challenge[blobBegin] != ',') { 
                    ++blobBegin;
                } 
                else {
                    index = -1;
                }
 
                if (index >= 0 && challenge.Length > blobBegin)
                { 
                    // Strip other modules information in case of multiple challenges 
                    // i.e do not take ", NTLM" as part of the following Negotiate blob
                    // Negotiate TlRMTVNTUAACAAAADgAOADgAAAA1wo ... MAbwBmAHQALgBjAG8AbQAAAAAA,NTLM 
                    index = challenge.IndexOf(',', blobBegin);
                    if (index != -1)
                        incoming = challenge.Substring(blobBegin, index - blobBegin);
                    else 
                        incoming = challenge.Substring(blobBegin);
                } 
 
                authSession = httpWebRequest.CurrentAuthenticationState.GetSecurityContext(this);
                GlobalLog.Print("KerberosClient::DoAuthenticate() key:" + ValidationHelper.HashString(httpWebRequest.CurrentAuthenticationState) + " retrieved authSession:" + ValidationHelper.HashString(authSession)); 
            }

            if (authSession==null) {
                NetworkCredential NC = credentials.GetCredential(httpWebRequest.ChallengedUri, Signature); 
                GlobalLog.Print("KerberosClient::DoAuthenticate() GetCredential() returns:" + ValidationHelper.ToString(NC));
 
                if (NC == null || (!(NC is SystemNetworkCredential) && NC.InternalGetUserName().Length == 0)) 
                {
                    return null; 
                }

                ICredentialPolicy policy = AuthenticationManager.CredentialPolicy;
                if (policy != null && !policy.ShouldSendCredential(httpWebRequest.ChallengedUri, httpWebRequest, NC, this)) 
                    return null;
 
                string spn = httpWebRequest.CurrentAuthenticationState.GetComputeSpn(httpWebRequest); 
                GlobalLog.Print("KerberosClient::Authenticate() ChallengedSpn:" + ValidationHelper.ToString(spn));
 
                ChannelBinding binding = null;
                if (httpWebRequest.CurrentAuthenticationState.TransportContext != null)
                {
                    binding = httpWebRequest.CurrentAuthenticationState.TransportContext.GetChannelBinding(ChannelBindingKind.Endpoint); 
                }
 
                authSession = 
                    new NTAuthentication(
                        AuthType, 
                        NC,
                        spn,
                        httpWebRequest,
                        binding); 

 
                GlobalLog.Print("KerberosClient::DoAuthenticate() setting SecurityContext for:" + ValidationHelper.HashString(httpWebRequest.CurrentAuthenticationState) + " to authSession:" + ValidationHelper.HashString(authSession)); 
                httpWebRequest.CurrentAuthenticationState.SetSecurityContext(authSession, this);
            } 

            string clientResponse = authSession.GetOutgoingBlob(incoming);
            if (clientResponse==null) {
                return null; 
            }
 
            return new Authorization(AuthType + " " + clientResponse, authSession.IsCompleted, string.Empty, authSession.IsMutualAuthFlag); 
        }
 
        public bool CanPreAuthenticate {
            get {
                return true;
            } 
        }
 
        public Authorization PreAuthenticate(WebRequest webRequest, ICredentials credentials) { 
            GlobalLog.Print("KerberosClient::PreAuthenticate() webRequest#" + ValidationHelper.HashString(webRequest) + " credentials#" + ValidationHelper.HashString(credentials) + " calling DoAuthenticate()");
            return DoAuthenticate(null, webRequest, credentials, true); 
        }

        public string AuthenticationType {
            get { 
                return AuthType;
            } 
        } 

        // 
        // called when getting the final blob on the 200 OK from the server
        //
        public bool Update(string challenge, WebRequest webRequest) {
            GlobalLog.Print("KerberosClient::Update(): " + challenge); 

            HttpWebRequest httpWebRequest = webRequest as HttpWebRequest; 
 
            GlobalLog.Assert(httpWebRequest != null, "KerberosClient::Update()|httpWebRequest == null");
            GlobalLog.Assert(httpWebRequest.ChallengedUri != null, "KerberosClient::Update()|httpWebRequest.ChallengedUri == null"); 

            //
            // try to retrieve the state of the ongoing handshake
            // 
            NTAuthentication authSession = httpWebRequest.CurrentAuthenticationState.GetSecurityContext(this);
            GlobalLog.Print("KerberosClient::Update() key:" + ValidationHelper.HashString(httpWebRequest.CurrentAuthenticationState) + " retrieved authSession:" + ValidationHelper.HashString(authSession)); 
 
            if (authSession==null) {
                GlobalLog.Print("KerberosClient::Update() null session returning true"); 
                return true;
            }

            GlobalLog.Print("KerberosClient::Update() authSession.IsCompleted:" + authSession.IsCompleted.ToString()); 

            if (httpWebRequest.CurrentAuthenticationState.StatusCodeMatch==httpWebRequest.ResponseStatusCode) { 
                GlobalLog.Print("KerberosClient::Update() still handshaking (based on status code) returning false"); 
                return false;
            } 

            //
            // the whole point here is to to close the Security Context (this will complete the authentication handshake
            // with server authentication for schemese that support it such as Kerberos) 
            //
            int index = challenge==null ? -1 : AuthenticationManager.FindSubstringNotInQuotes(challenge, Signature); 
            if (index>=0) { 
                int blobBegin = index + SignatureSize;
                string incoming = null; 

                //
                // there may be multiple challenges. If the next character after the
                // package name is not a comma then it is challenge data 
                //
                if (challenge.Length > blobBegin && challenge[blobBegin] != ',') { 
                    ++blobBegin; 
                } else {
                    index = -1; 
                }
                if (index >= 0 && challenge.Length > blobBegin) {
                    incoming = challenge.Substring(blobBegin);
                } 
                GlobalLog.Print("KerberosClient::Update() closing security context using last incoming blob:[" + ValidationHelper.ToString(incoming) + "]");
                string clientResponse = authSession.GetOutgoingBlob(incoming); 
                httpWebRequest.CurrentAuthenticationState.Authorization.MutuallyAuthenticated = authSession.IsMutualAuthFlag; 
                GlobalLog.Print("KerberosClient::Update() GetOutgoingBlob() returns clientResponse:[" + ValidationHelper.ToString(clientResponse) + "] IsCompleted:" + authSession.IsCompleted.ToString());
            } 

            // Extract the CBT we used and cache it for future requests that want to do preauth
            httpWebRequest.ServicePoint.SetCachedChannelBinding(httpWebRequest.ChallengedUri, authSession.ChannelBinding);
 
            GlobalLog.Print("KerberosClient::Update() session removed and ConnectionGroup released returning true");
            ClearSession(httpWebRequest); 
            return true; 
        }
 
        public void ClearSession(WebRequest webRequest) {
            HttpWebRequest httpWebRequest = webRequest as HttpWebRequest;
            GlobalLog.Assert(httpWebRequest != null, "KerberosClient::ClearSession()|httpWebRequest == null");
            httpWebRequest.CurrentAuthenticationState.ClearSession(); 
        }
 
        public bool CanUseDefaultCredentials { 
            get {
                return true; 
            }
        }

    }; // class KerberosClient 

 
} // namespace System.Net 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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