_DigestClient.cs source code in C# .NET

Source code for the .NET framework in C#

                        

Code:

/ FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / fx / src / Net / System / Net / _DigestClient.cs / 1 / _DigestClient.cs

                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Net { 
    using System.Net.Sockets; 
    using System.Collections;
    using System.Text; 
    using System.Security.Cryptography;
    using System.Security.Permissions;
    using System.Globalization;
 
    internal class DigestClient : ISessionAuthenticationModule {
 
        internal const string AuthType = "Digest"; 
        internal static string Signature = AuthType.ToLower(CultureInfo.InvariantCulture);
        internal static int SignatureSize = Signature.Length; 

        private static PrefixLookup challengeCache = new PrefixLookup();
        private static readonly char[] singleSpaceArray = new char[]{' '};
 
        // [....]: make sure WDigest fixes these bugs before we
        // enable this code ("Windows OS" Product Studio database): 
        // 
        // 921024   1   Wdigest should support MD5, at least for explicit (non-default) credentials.
        // 762116   2   WDigest should ignore directives that do not have a value 
        // 762115   3   WDigest should allow an application to retrieve the parsed domain directive
        //
        private static bool _WDigestAvailable;
 
        static DigestClient() {
            _WDigestAvailable = SSPIWrapper.GetVerifyPackageInfo(GlobalSSPI.SSPIAuth, NegotiationInfoClass.WDigest)!=null; 
        } 

        public Authorization Authenticate(string challenge, WebRequest webRequest, ICredentials credentials) { 
            GlobalLog.Print("DigestClient::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("DigestClient::DoAuthenticate() challenge:[" + ValidationHelper.ToString(challenge) + "] webRequest#" + ValidationHelper.HashString(webRequest) + " credentials#" + ValidationHelper.HashString(credentials) + " preAuthenticate:" + preAuthenticate.ToString()); 
 
            GlobalLog.Assert(credentials != null, "DigestClient::DoAuthenticate()|credentials == null");
            if (credentials==null) { 
                return null;
            }

            HttpWebRequest httpWebRequest = webRequest as HttpWebRequest; 
            GlobalLog.Assert(httpWebRequest != null, "DigestClient::DoAuthenticate()|httpWebRequest == null");
            GlobalLog.Assert(httpWebRequest.ChallengedUri != null, "DigestClient::DoAuthenticate()|httpWebRequest.ChallengedUri == null"); 
 
            // If it's default credentials, we support them on XP and up through WDigest.
 

            NetworkCredential NC = credentials.GetCredential(httpWebRequest.ChallengedUri, DigestClient.Signature);
            GlobalLog.Print("DigestClient::DoAuthenticate() GetCredential() returns:" + ValidationHelper.ToString(NC));
 
            if (NC is SystemNetworkCredential) {
                if (WDigestAvailable) { 
                    return XPDoAuthenticate(challenge, httpWebRequest, credentials, preAuthenticate); 
                }
                else { 
                    return null;
                }
            }
 
            HttpDigestChallenge digestChallenge;
            if (!preAuthenticate) { 
                int index = AuthenticationManager.FindSubstringNotInQuotes(challenge, Signature); 
                if (index < 0) {
                    return null; 
                }
                digestChallenge = HttpDigest.Interpret(challenge, index, httpWebRequest);
            }
            else { 
                GlobalLog.Print("DigestClient::DoAuthenticate() looking up digestChallenge for prefix:" + httpWebRequest.ChallengedUri.AbsoluteUri);
                digestChallenge = challengeCache.Lookup(httpWebRequest.ChallengedUri.AbsoluteUri) as HttpDigestChallenge; 
            } 
            if (digestChallenge==null) {
                return null; 
            }

            bool supported = CheckQOP(digestChallenge);
            if (!supported) { 
                throw new NotSupportedException(SR.GetString(SR.net_QOPNotSupportedException, digestChallenge.QualityOfProtection));
            } 
 
            if (preAuthenticate) {
                GlobalLog.Print("DigestClient::DoAuthenticate() retrieved digestChallenge#" + ValidationHelper.HashString(digestChallenge) + " digestChallenge for prefix:" + httpWebRequest.ChallengedUri.AbsoluteUri); 
                digestChallenge = digestChallenge.CopyAndIncrementNonce();
                digestChallenge.SetFromRequest(httpWebRequest);
            }
 
            if (NC==null) {
                return null; 
            } 

            ICredentialPolicy policy = AuthenticationManager.CredentialPolicy; 
            if (policy != null && !policy.ShouldSendCredential(httpWebRequest.ChallengedUri, httpWebRequest, NC, this))
                return null;

            Authorization digestResponse = HttpDigest.Authenticate(digestChallenge, NC); 
            if (!preAuthenticate && digestResponse!=null) {
                // add this to the cache of challenges so we can preauthenticate 
                string[] prefixes = digestChallenge.Domain==null ? 
                        new string[]{httpWebRequest.ChallengedUri.GetParts(UriComponents.SchemeAndServer, UriFormat.UriEscaped)}
                        : digestChallenge.Domain.Split(singleSpaceArray); 

                // If Domain property is not set we associate Digest only with the server Uri namespace (used to do with whole server)
                digestResponse.ProtectionRealm = digestChallenge.Domain==null ? null: prefixes;
 
                for (int i=0; i=0) { 
                    // find the next occurence of "auth"
                    index = challenge.QualityOfProtection.IndexOf(HttpDigest.SupportedQuality, index);
                    if (index<0) {
                        return false; 
                    }
                    // if it's a whole word we're done 
                    if ((index==0 || HttpDigest.ValidSeparator.IndexOf(challenge.QualityOfProtection[index - 1])>=0) && 
                        (index+HttpDigest.SupportedQuality.Length==challenge.QualityOfProtection.Length || HttpDigest.ValidSeparator.IndexOf(challenge.QualityOfProtection[index + HttpDigest.SupportedQuality.Length])>=0) ) {
                        break; 
                    }
                    index += HttpDigest.SupportedQuality.Length;
                }
            } 
            return true;
        } 
 
        public bool Update(string challenge, WebRequest webRequest) {
            GlobalLog.Print("DigestClient::Update(): [" + challenge + "]"); 
            HttpWebRequest httpWebRequest = webRequest as HttpWebRequest;

            GlobalLog.Assert(httpWebRequest!=null, "DigestClient::Update()|httpWebRequest == null");
            GlobalLog.Assert(httpWebRequest.ChallengedUri != null, "DigestClient::Update()|httpWebRequest.ChallengedUri == null"); 

            // make sure WDigest fixes these bugs before we enable this code ("Windows OS"): 
            // 921024   1   WDigest should support MD5, at least for explicit (non-default) credentials. 
            // 762116   2   WDigest should ignore directives that do not have a value
            // 762115   3   WDigest should allow an application to retrieve the parsed domain directive 
            if (httpWebRequest.CurrentAuthenticationState.GetSecurityContext(this) != null) {
                return XPUpdate(challenge, httpWebRequest);
            }
 
            // here's how we know if the handshake is complete when we get the response back,
            // (keeping in mind that we need to support stale credentials): 
            // !40X - complete & success 
            // 40X & stale=false - complete & failure
            // 40X & stale=true - !complete 

            if (httpWebRequest.ResponseStatusCode!=httpWebRequest.CurrentAuthenticationState.StatusCodeMatch) {
                GlobalLog.Print("DigestClient::Update(): no status code match. returning true");
                return true; 
            }
 
            int index = challenge==null ? -1 : AuthenticationManager.FindSubstringNotInQuotes(challenge, Signature); 
            if (index < 0) {
                GlobalLog.Print("DigestClient::Update(): no challenge. returning true"); 
                return true;
            }

            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); 
            }

            HttpDigestChallenge digestChallenge = HttpDigest.Interpret(challenge, index, httpWebRequest);
            if (digestChallenge==null) { 
                GlobalLog.Print("DigestClient::Update(): not a valid digest challenge. returning true");
                return true; 
            } 

            GlobalLog.Print("DigestClient::Update(): returning digestChallenge.Stale:" + digestChallenge.Stale.ToString()); 
            return !digestChallenge.Stale;
        }

        public bool CanUseDefaultCredentials { 
            get {
                return WDigestAvailable; 
            } 
        }
 
        internal static bool WDigestAvailable {
            get {
                return _WDigestAvailable;
            } 
        }
 
        public void ClearSession(WebRequest webRequest) { 
            HttpWebRequest httpWebRequest = webRequest as HttpWebRequest;
            GlobalLog.Assert(httpWebRequest != null, "NtlmClient::ClearSession()|httpWebRequest == null"); 
            // when we're using WDigest.dll we need to keep the NTAuthentication instance around, since it's in the
            // challengeCache so remove the reference in the AuthenticationState to avoid closing it in ClearSession
#if WDIGEST_PREAUTH
            httpWebRequest.CurrentAuthenticationState.SetSecurityContext(null, this); 
#else
            httpWebRequest.CurrentAuthenticationState.ClearSession(); 
#endif 
        }
 

        // On Windows XP and up, WDigest.dll supports the Digest authentication scheme (in addition to
        // support for HTTP client sides, it also supports HTTP server side and SASL) through SSPI.
 
        private Authorization XPDoAuthenticate(string challenge, HttpWebRequest httpWebRequest, ICredentials credentials, bool preAuthenticate) {
            GlobalLog.Print("DigestClient::XPDoAuthenticate() challenge:[" + ValidationHelper.ToString(challenge) + "] httpWebRequest#" + ValidationHelper.HashString(httpWebRequest) + " credentials#" + ValidationHelper.HashString(credentials) + " preAuthenticate:" + preAuthenticate.ToString()); 
 
            NTAuthentication authSession = null;
            string incoming = null; 
            int index;

            if (!preAuthenticate) {
                index = AuthenticationManager.FindSubstringNotInQuotes(challenge, Signature); 
                if (index < 0) {
                    return null; 
                } 
                authSession = httpWebRequest.CurrentAuthenticationState.GetSecurityContext(this);
                GlobalLog.Print("DigestClient::XPDoAuthenticate() key:" + ValidationHelper.HashString(httpWebRequest.CurrentAuthenticationState) + " retrieved authSession:" + ValidationHelper.HashString(authSession)); 
                incoming = RefineDigestChallenge(challenge, index);
            }
            else {
#if WDIGEST_PREAUTH 
                GlobalLog.Print("DigestClient::XPDoAuthenticate() looking up digestChallenge for prefix:" + httpWebRequest.ChallengedUri.AbsoluteUri);
                authSession = challengeCache.Lookup(httpWebRequest.ChallengedUri.AbsoluteUri) as NTAuthentication; 
                if (authSession==null) { 
                    return null;
                } 
#else
                GlobalLog.Print("DigestClient::XPDoAuthenticate() looking up digestChallenge for prefix:" + httpWebRequest.ChallengedUri.AbsoluteUri);
                HttpDigestChallenge digestChallenge = challengeCache.Lookup(httpWebRequest.ChallengedUri.AbsoluteUri) as HttpDigestChallenge;
                if (digestChallenge==null) { 
                    return null;
                } 
 
                GlobalLog.Print("DigestClient::XPDoAuthenticate() retrieved digestChallenge#" + ValidationHelper.HashString(digestChallenge) + " digestChallenge for prefix:" + httpWebRequest.ChallengedUri.AbsoluteUri);
                digestChallenge = digestChallenge.CopyAndIncrementNonce(); 
                digestChallenge.SetFromRequest(httpWebRequest);
                incoming = digestChallenge.ToBlob();
#endif
            } 

            string rawUri = null; 
#if WDIGEST_PREAUTH 
            if (authSession==null || preAuthenticate) {
                // need rawUri for the call to MakeSignature 
#else
            if (authSession==null) {
#endif
                UriComponents uriParts = 0; 
                if (httpWebRequest.CurrentMethod.ConnectRequest) {
                    uriParts = UriComponents.HostAndPort; 
                } 
                else if (httpWebRequest.UsesProxySemantics) {
                    uriParts = UriComponents.HttpRequestUrl; 
                }
                else {
                    uriParts = UriComponents.PathAndQuery;
                } 
                // here we use Address instead of ChallengedUri. This is because the
                // Digest hash is generated using the uri as it is present on the wire 
                rawUri = httpWebRequest.Address.GetParts(uriParts, UriFormat.UriEscaped); 
                GlobalLog.Print("DigestClient::XPDoAuthenticate() rawUri:" + ValidationHelper.ToString(rawUri));
            } 

            if (authSession==null) {
                NetworkCredential NC = credentials.GetCredential(httpWebRequest.ChallengedUri, Signature);
                GlobalLog.Print("DigestClient::XPDoAuthenticate() 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; 

                authSession = 
                    new NTAuthentication( 
                        NegotiationInfoClass.WDigest,
                        NC, 
                        rawUri,
                        httpWebRequest);

                GlobalLog.Print("DigestClient::XPDoAuthenticate() setting SecurityContext for:" + ValidationHelper.HashString(httpWebRequest.CurrentAuthenticationState) + " to authSession:" + ValidationHelper.HashString(authSession)); 
                httpWebRequest.CurrentAuthenticationState.SetSecurityContext(authSession, this);
            } 
 
            SecurityStatus statusCode;
            string clientResponse; 

            GlobalLog.Print("DigestClient::XPDoAuthenticate() incoming:" + ValidationHelper.ToString(incoming));

#if WDIGEST_PREAUTH 
            clientResponse = authSession.GetOutgoingDigestBlob(incoming, httpWebRequest.CurrentMethod.Name, rawUri, null, preAuthenticate, true, out statusCode);
#else 
            clientResponse = authSession.GetOutgoingDigestBlob(incoming, httpWebRequest.CurrentMethod.Name, rawUri, null, false, true, out statusCode); 
#endif
            GlobalLog.Print("DigestClient::XPDoAuthenticate() GetOutgoingDigestBlob(" + incoming + ") returns:" + ValidationHelper.ToString(clientResponse)); 

            Authorization digestResponse = new Authorization(AuthType + " " + clientResponse, authSession.IsCompleted, string.Empty, authSession.IsMutualAuthFlag);

            if (!preAuthenticate) { 
                // add this to the cache of challenges so we can preauthenticate
                // use this DCR when avaialble to do this without calling HttpDigest.Interpret(): 
                // 762115   3   WDigest should allow an application to retrieve the parsed domain directive 
                HttpDigestChallenge digestChallenge = HttpDigest.Interpret(incoming, -1, httpWebRequest);
 
                string[] prefixes = digestChallenge.Domain==null ?
                        new string[]{httpWebRequest.ChallengedUri.GetParts(UriComponents.SchemeAndServer, UriFormat.UriEscaped)}
                        : digestChallenge.Domain.Split(singleSpaceArray);
 
                // If Domain property is not set we associate Digest only with the server Uri namespace (used to do with whole server)
                digestResponse.ProtectionRealm = digestChallenge.Domain==null ? null: prefixes; 
 
                for (int i=0; i= challenge.Length)
                throw new ArgumentOutOfRangeException("challenge", challenge); 

            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) { 
                incoming = challenge.Substring(blobBegin); 
            }
            else 
            {
                throw new ArgumentOutOfRangeException("challenge", challenge);
            }
 
            // now make sure there's nothing at the end of the challenge that is not part of the digest challenge
            // this would happen if I have a Digest challenge followed by another challenge like ",NTLM,Negotiate" 
            // use this DCR when avaialble to do this without parsing: 
            // 762116   2   WDigest should ignore directives that do not have a value
            int startingPoint = 0; 
            int start = startingPoint;
            int offset;
            bool valid = true;
            string name, value; 
            HttpDigestChallenge digestChallenge = new HttpDigestChallenge();
            for (;;) { 
                offset = start; 
                index = AuthenticationManager.SplitNoQuotes(incoming, ref offset);
                GlobalLog.Print("DigestClient::XPDoAuthenticate() SplitNoQuotes() returning index:" + index + " offset:" + offset); 
                if (offset<0) {
                    break;
                }
                name = incoming.Substring(start, offset-start); 
                if (index<0) {
                    value = HttpDigest.unquote(incoming.Substring(offset+1)); 
                } 
                else {
                    value = HttpDigest.unquote(incoming.Substring(offset+1, index-offset-1)); 
                }
                valid = digestChallenge.defineAttribute(name, value);
                GlobalLog.Print("DigestClient::XPDoAuthenticate() defineAttribute(" + name + ", " + value + ") returns " + valid);
                if (index<0 || !valid) { 
                    break;
                } 
                start = ++index; 
            }
            GlobalLog.Print("DigestClient::XPDoAuthenticate() start:" + start + " offset:" + offset + " index:" + index + " valid:" + valid + " incoming.Length:" + incoming.Length + " incoming:" + incoming); 
            if ((!valid || offset<0) && start0;
            }
            else if (name.Equals(HttpDigest.DA_realm)) {
                Realm = value; 
            }
            else if (name.Equals(HttpDigest.DA_domain)) { 
                Domain = value; 
            }
            else if (name.Equals(HttpDigest.DA_response)) { 
            }
            else if (name.Equals(HttpDigest.DA_stale)) {
                Stale = value.ToLower(CultureInfo.InvariantCulture).Equals("true");
            } 
            else if (name.Equals(HttpDigest.DA_uri)) {
                Uri = value; 
            } 
            else if (name.Equals(HttpDigest.DA_charset)) {
                Charset = value; 
            }
            else if (name.Equals(HttpDigest.DA_cipher)) {
                // ignore
            } 
            else if (name.Equals(HttpDigest.DA_username)) {
                // ignore 
            } 
            else {
                // 
                // the token is not recognized, this usually
                // happens when there are multiple challenges
                //
                return false; 
            }
            return true; 
        } 

        internal string ToBlob() { 
            StringBuilder stringBuilder = new StringBuilder();
            stringBuilder.Append(HttpDigest.pair(HttpDigest.DA_realm, Realm, true));
            if (Algorithm!=null) {
                stringBuilder.Append(","); 
                stringBuilder.Append(HttpDigest.pair(HttpDigest.DA_algorithm, Algorithm, true));
            } 
            if (Charset!=null) { 
                stringBuilder.Append(",");
                stringBuilder.Append(HttpDigest.pair(HttpDigest.DA_charset, Charset, false)); 
            }
            if (Nonce!=null) {
                stringBuilder.Append(",");
                stringBuilder.Append(HttpDigest.pair(HttpDigest.DA_nonce, Nonce, true)); 
            }
            if (Uri!=null) { 
                stringBuilder.Append(","); 
                stringBuilder.Append(HttpDigest.pair(HttpDigest.DA_uri, Uri, true));
            } 
            if (ClientNonce!=null) {
                stringBuilder.Append(",");
                stringBuilder.Append(HttpDigest.pair(HttpDigest.DA_cnonce, ClientNonce, true));
            } 
            if (NonceCount>0) {
                stringBuilder.Append(","); 
                stringBuilder.Append(HttpDigest.pair(HttpDigest.DA_nc, NonceCount.ToString("x8", NumberFormatInfo.InvariantInfo), true)); 
            }
            if (QualityOfProtection!=null) { 
                stringBuilder.Append(",");
                stringBuilder.Append(HttpDigest.pair(HttpDigest.DA_qop, QualityOfProtection, true));
            }
            if (Opaque!=null) { 
                stringBuilder.Append(",");
                stringBuilder.Append(HttpDigest.pair(HttpDigest.DA_opaque, Opaque, true)); 
            } 
            if (Domain!=null) {
                stringBuilder.Append(","); 
                stringBuilder.Append(HttpDigest.pair(HttpDigest.DA_domain, Domain, true));
            }
            if (Stale) {
                stringBuilder.Append(","); 
                stringBuilder.Append(HttpDigest.pair(HttpDigest.DA_stale, "true", true));
            } 
            return stringBuilder.ToString(); 
        }
 
    }


    internal static class HttpDigest { 
        //
        // these are the tokens defined by Digest 
        // http://www.ietf.org/rfc/rfc2831.txt 
        //
        internal const string DA_algorithm  = "algorithm"; 
        internal const string DA_cnonce     = "cnonce"; // client-nonce
        internal const string DA_domain     = "domain";
        internal const string DA_nc         = "nc"; // nonce-count
        internal const string DA_nonce      = "nonce"; 
        internal const string DA_opaque     = "opaque";
        internal const string DA_qop        = "qop"; // quality-of-protection 
        internal const string DA_realm      = "realm"; 
        internal const string DA_response   = "response";
        internal const string DA_stale      = "stale"; 
        internal const string DA_uri        = "uri";
        internal const string DA_username   = "username";
        internal const string DA_charset    = "charset";
        internal const string DA_cipher     = "cipher"; 

        internal const string SupportedQuality = "auth"; 
        internal const string ValidSeparator = ", \"\'\t\r\n"; 

        // 
        // consider internally caching the nonces sent to us by a server so that
        // we can correctly send out nonce counts for subsequent requests

        // 
        // used to create a random nonce
        // 
        private static readonly RNGCryptoServiceProvider RandomGenerator = new RNGCryptoServiceProvider(); 
        //
        // this method parses the challenge and breaks it into the 
        // fundamental pieces that Digest defines and understands
        //
        internal static HttpDigestChallenge Interpret(string challenge, int startingPoint, HttpWebRequest httpWebRequest) {
            HttpDigestChallenge digestChallenge = new HttpDigestChallenge(); 
            digestChallenge.SetFromRequest(httpWebRequest);
            // 
            // define the part of the challenge we really care about 
            //
            startingPoint = startingPoint==-1 ? 0 : startingPoint + DigestClient.SignatureSize; 

            bool valid;
            int start, offset, index;
            string name, value; 

            // forst time parse looking for a charset="utf-8" directive 
            // not too bad, IIS 6.0, by default, sends this as the first directive. 
            // if the server does not send this we'll end up parsing twice.
            start = startingPoint; 
            for (;;) {
                offset = start;
                index = AuthenticationManager.SplitNoQuotes(challenge, ref offset);
                if (offset<0) { 
                    break;
                } 
                name = challenge.Substring(start, offset-start); 
                if (string.Compare(name, DA_charset, StringComparison.OrdinalIgnoreCase)==0) {
                    if (index<0) { 
                        value = unquote(challenge.Substring(offset+1));
                    }
                    else {
                        value = unquote(challenge.Substring(offset+1, index-offset-1)); 
                    }
                    GlobalLog.Print("HttpDigest::Interpret() server provided a hint to use [" + value + "] encoding"); 
                    if (string.Compare(value, "utf-8", StringComparison.OrdinalIgnoreCase)==0) { 
                        digestChallenge.UTF8Charset = true;
                        break; 
                    }
                }
                if (index<0) {
                    break; 
                }
                start = ++index; 
            } 

            // this time go through the directives, parse them and call defineAttribute() 
            start = startingPoint;
            for (;;) {
                offset = start;
                index = AuthenticationManager.SplitNoQuotes(challenge, ref offset); 
                GlobalLog.Print("HttpDigest::Interpret() SplitNoQuotes() returning index:" + index.ToString() + " offset:" + offset.ToString());
                if (offset<0) { 
                    break; 
                }
                name = challenge.Substring(start, offset-start); 
                if (index<0) {
                    value = unquote(challenge.Substring(offset+1));
                }
                else { 
                    value = unquote(challenge.Substring(offset+1, index-offset-1));
                } 
                if (digestChallenge.UTF8Charset) { 
                    bool isAscii = true;
                    for (int i=0; i(char)0x7F) {
                            isAscii = false;
                            break;
                        } 
                    }
                    if (!isAscii) { 
                        GlobalLog.Print("HttpDigest::Interpret() UTF8 decoding required value:[" + value + "]"); 
                        byte[] bytes = new byte[value.Length];
                        for (int i=0; i(char)0x7F) { 
                    GlobalLog.Print("HttpDigest::DetectCharset() found non ASCII character:[" + ((int)rawString[i]).ToString() + "] at offset i:[" + i.ToString() + "] charset:[" + charset.ToString() + "]");
                    // the only way we can tell if we can use default ANSI encoding is see 
                    // in the encode/decode process there is no loss of information. 
                    byte[] bytes = Encoding.Default.GetBytes(rawString);
                    string rawCopy = Encoding.Default.GetString(bytes); 
                    charset = string.Compare(rawString, rawCopy, StringComparison.Ordinal)==0 ? Charset.ANSI : Charset.UTF8;
                    break;
                }
            } 
            GlobalLog.Print("HttpDigest::DetectCharset() rawString:[" + rawString + "] has charset:[" + charset.ToString() + "]");
            return charset; 
        } 

#if TRAVE 
        private static string Chars(string rawString) {
            string returnString = "[";
            for (int i=0; i0) { 
                    returnString += ",";
                } 
                returnString += ((int)rawString[i]).ToString(); 
            }
            return returnString + "]"; 
        }
#endif // #if TRAVE

        // 
        //
 
 
        internal static Authorization Authenticate(HttpDigestChallenge digestChallenge, NetworkCredential NC) {
 
            string username = NC.InternalGetUserName();
            if (ValidationHelper.IsBlankString(username)) {
                return null;
            } 
            string password = NC.InternalGetPassword();
 
            if (digestChallenge.QopPresent) { 
                if (digestChallenge.ClientNonce==null || digestChallenge.Stale) {
                    GlobalLog.Print("HttpDigest::Authenticate() QopPresent:True, need new nonce. digestChallenge.ClientNonce:" + ValidationHelper.ToString(digestChallenge.ClientNonce) + " digestChallenge.Stale:" + digestChallenge.Stale.ToString()); 
                    digestChallenge.ClientNonce = createNonce(32);
                    digestChallenge.NonceCount = 1;
                }
                else { 
                    GlobalLog.Print("HttpDigest::Authenticate() QopPresent:True, reusing nonce. digestChallenge.NonceCount:" + digestChallenge.NonceCount.ToString());
                    digestChallenge.NonceCount++; 
                } 
            }
 
            StringBuilder authorization = new StringBuilder();

            //
            // look at username & password, if it's not ASCII we need to attempt some 
            // kind of encoding because we need to calculate the hash on byte[]
            // 
            Charset usernameCharset = DetectCharset(username); 
            if (!digestChallenge.UTF8Charset && usernameCharset==Charset.UTF8) {
                GlobalLog.Print("HttpDigest::Authenticate() can't authenticate with UNICODE username. failing auth."); 
                return null;
            }
            Charset passwordCharset = DetectCharset(password);
            if (!digestChallenge.UTF8Charset && passwordCharset==Charset.UTF8) { 
                GlobalLog.Print("HttpDigest::Authenticate() can't authenticate with UNICODE password. failing auth.");
                return null; 
            } 
            if (digestChallenge.UTF8Charset) {
                // on the wire always use UTF8 when the server supports it 
                authorization.Append(pair(DA_charset, "utf-8", false));
                authorization.Append(",");
                if (usernameCharset==Charset.UTF8) {
                    username = CharsetEncode(username, Charset.UTF8); 
                    authorization.Append(pair(DA_username, username, true));
                    authorization.Append(","); 
                } 
                else {
                    authorization.Append(pair(DA_username, CharsetEncode(username, Charset.UTF8), true)); 
                    authorization.Append(",");
                    username = CharsetEncode(username, usernameCharset);
                }
            } 
            else {
                // otherwise UTF8 is not required 
                username = CharsetEncode(username, usernameCharset); 
                authorization.Append(pair(DA_username, username, true));
                authorization.Append(","); 
            }

            password = CharsetEncode(password, passwordCharset);
 
            // no special encoding for the realm since we're just going to echo it back (encoding must have happened on the server).
            authorization.Append(pair(DA_realm, digestChallenge.Realm, true)); 
            authorization.Append(","); 
            authorization.Append(pair(DA_nonce, digestChallenge.Nonce, true));
            authorization.Append(","); 
            authorization.Append(pair(DA_uri, digestChallenge.Uri, true));

            if (digestChallenge.QopPresent) {
                if (digestChallenge.Algorithm!=null) { 
                    // consider: should we default to "MD5" here? IE does
                    authorization.Append(","); 
                    authorization.Append(pair(DA_algorithm, digestChallenge.Algorithm, true)); // IE sends quotes - IIS needs them 
                }
                authorization.Append(","); 
                authorization.Append(pair(DA_cnonce, digestChallenge.ClientNonce, true));
                authorization.Append(",");
                authorization.Append(pair(DA_nc, digestChallenge.NonceCount.ToString("x8", NumberFormatInfo.InvariantInfo), false));
                // RAID#47397 
                // send only the QualityOfProtection we're using
                // since we support only "auth" that's what we will send out 
                authorization.Append(","); 
                authorization.Append(pair(DA_qop, SupportedQuality, true)); // IE sends quotes - IIS needs them
            } 

            // warning: this must be computed here
            string responseValue = HttpDigest.responseValue(digestChallenge, username, password);
            if (responseValue==null) { 
                return null;
            } 
 
            authorization.Append(",");
            authorization.Append(pair(DA_response, responseValue, true)); // IE sends quotes - IIS needs them 

            if (digestChallenge.Opaque!=null) {
                authorization.Append(",");
                authorization.Append(pair(DA_opaque, digestChallenge.Opaque, true)); 
            }
 
            GlobalLog.Print("HttpDigest::Authenticate() digestChallenge.Stale:" + digestChallenge.Stale.ToString()); 

            // completion is decided in Update() 
            Authorization finalAuthorization = new Authorization(DigestClient.AuthType + " " + authorization.ToString(), false);

            return finalAuthorization;
        } 

        internal static string unquote(string quotedString) { 
            return quotedString.Trim().Trim("\"".ToCharArray()); 
        }
 
        // Returns the string consisting of  followed by
        // an equal sign, followed by the  in double-quotes
        internal static string pair(string name, string value, bool quote) {
            if (quote) { 
                return name + "=\"" + value + "\"";
            } 
            return name + "=" + value; 
        }
 
        //
        // this method computes the response-value according to the
        // rules described in RFC2831 section 2.1.2.1
        // 
        private static string responseValue(HttpDigestChallenge challenge, string username, string password) {
            string secretString = computeSecret(challenge, username, password); 
            if (secretString == null) { 
                return null;
            } 

            // we assume auth here, since it's the only one we support, the check happened earlier
            string dataString = challenge.Method + ":" + challenge.Uri;
            if (dataString == null) { 
                return null;
            } 
 
            string secret = hashString(secretString, challenge.MD5provider);
            string hexMD2 = hashString(dataString, challenge.MD5provider); 

            string data =
                challenge.Nonce + ":" +
                    (challenge.QopPresent ? 
                        challenge.NonceCount.ToString("x8", NumberFormatInfo.InvariantInfo) + ":" +
                        challenge.ClientNonce + ":" + 
                        SupportedQuality + ":" + // challenge.QualityOfProtection + ":" + 
                        hexMD2
                        : 
                        hexMD2);

            return hashString(secret + ":" + data, challenge.MD5provider);
        } 

        private static string computeSecret(HttpDigestChallenge challenge, string username, string password) { 
            if (challenge.Algorithm==null || string.Compare(challenge.Algorithm, "md5" ,StringComparison.OrdinalIgnoreCase)==0) { 
                return username + ":" + challenge.Realm + ":" + password;
            } 
            else if (string.Compare(challenge.Algorithm, "md5-sess" ,StringComparison.OrdinalIgnoreCase)==0) {
                return hashString(username + ":" + challenge.Realm + ":" + password, challenge.MD5provider) + ":" + challenge.Nonce + ":" + challenge.ClientNonce;
            }
            throw new NotSupportedException(SR.GetString(SR.net_HashAlgorithmNotSupportedException, challenge.Algorithm)); 
        }
 
        private static string hashString(string myString, MD5CryptoServiceProvider MD5provider) { 
            GlobalLog.Enter("HttpDigest::hashString", "[" + myString.Length.ToString() + ":" + myString + "]");
            byte[] encodedBytes = new byte[myString.Length]; 
            for (int i=0; i>4]; 
                wa[dp++] = Uri.HexLowerChars[rawbytes[i]&0x0F];
            } 

            return new string(wa);
        }
 
        /* returns a random nonce of given length */
        private static string createNonce(int length) { 
            // we'd need less (half of that), but this makes the code much simpler 
            int bytesNeeded = length;
            byte[] randomBytes = new byte[bytesNeeded]; 
            char[] digits = new char[length];
            RandomGenerator.GetBytes(randomBytes);
            for (int i=0; i

                        

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