Implement the context-completion check I've had sitting half done.

Contexts/ClientContext.cs

@@ -11,7 +11,6 @@ namespace NSspi.Contexts
 {
     public class ClientContext : Context
     {
-        private bool complete;
         private ContextAttrib requestedAttribs;
         private ContextAttrib finalAttribs;
         private string serverPrinc;
@@ -19,8 +18,6 @@ namespace NSspi.Contexts
         public ClientContext( ClientCredential cred, string serverPrinc, ContextAttrib requestedAttribs )
             : base( cred )
         {
-            this.complete = false;
-
             this.serverPrinc = serverPrinc;
             this.requestedAttribs = requestedAttribs;
         }
@@ -112,12 +109,12 @@ namespace NSspi.Contexts
 
             if ( status == SecurityStatus.OK )
             {
-                this.complete = true;
+                this.Initialized = true;
                 outToken = null;
             }
             else if ( status == SecurityStatus.ContinueNeeded )
             {
-                this.complete = false;
+                this.Initialized = false;
 
                 outToken = new byte[outTokenBuffer.Length];
                 Array.Copy( outTokenBuffer.Buffer, outToken, outToken.Length );

Contexts/Context.cs

@@ -22,12 +22,18 @@ namespace NSspi.Contexts
             this.ContextHandle = new SafeContextHandle();
 
             this.disposed = false;
+            this.Initialized = false;
         }
 
         ~Context()
         {
             Dispose( false );
         }
+        
+        /// <summary>
+        /// Whether or not the context is fully formed.
+        /// </summary>
+        public bool Initialized { get; protected set; }
 
         protected Credential Credential { get; private set; }
 
@@ -85,7 +91,7 @@ namespace NSspi.Contexts
         public byte[] Encrypt( byte[] input )
         {
             // The message is encrypted in place in the buffer we provide to Win32 EncryptMessage
-            SecPkgContext_Sizes sizes = QueryBufferSizes();
+            SecPkgContext_Sizes sizes;
 
             SecureBuffer trailerBuffer;
             SecureBuffer dataBuffer;
@@ -95,6 +101,13 @@ namespace NSspi.Contexts
             SecurityStatus status = SecurityStatus.InvalidHandle;
             byte[] result;
 
+            if ( this.Initialized == false )
+            {
+                throw new InvalidOperationException( "The context is not fully formed." );
+            }
+
+            sizes = QueryBufferSizes();
+
             trailerBuffer = new SecureBuffer( new byte[sizes.SecurityTrailer], BufferType.Token );
             dataBuffer = new SecureBuffer( new byte[input.Length], BufferType.Data );
             paddingBuffer = new SecureBuffer( new byte[sizes.BlockSize], BufferType.Padding );
@@ -148,7 +161,7 @@ namespace NSspi.Contexts
 
         public byte[] Decrypt( byte[] input )
         {
-            SecPkgContext_Sizes sizes = QueryBufferSizes();
+            SecPkgContext_Sizes sizes;
 
             SecureBuffer trailerBuffer;
             SecureBuffer dataBuffer;
@@ -164,6 +177,13 @@ namespace NSspi.Contexts
             int dataLength;
             int paddingLength;
 
+            if ( this.Initialized == false )
+            {
+                throw new InvalidOperationException( "The context is not fully formed." );
+            }
+
+            sizes = QueryBufferSizes();
+
             // This check is required, but not sufficient. We could be stricter.
             if( input.Length < 2 + 4 + 2 + sizes.SecurityTrailer )
             {
@@ -238,7 +258,7 @@ namespace NSspi.Contexts
             return result;
         }
 
-        internal SecPkgContext_Sizes QueryBufferSizes()
+        private SecPkgContext_Sizes QueryBufferSizes()
         {
             SecPkgContext_Sizes sizes = new SecPkgContext_Sizes();
             SecurityStatus status = SecurityStatus.InternalError;
@@ -280,7 +300,7 @@ namespace NSspi.Contexts
             return sizes;
         }
 
-        internal string QueryContextString(ContextQueryAttrib attrib)
+        private string QueryContextString(ContextQueryAttrib attrib)
         {
             SecPkgContext_String stringAttrib;
             SecurityStatus status = SecurityStatus.InternalError;

Contexts/ServerContext.cs

@@ -12,13 +12,11 @@ namespace NSspi.Contexts
     {
         private ContextAttrib requestedAttribs;
         private ContextAttrib finalAttribs;
-        private bool complete;
-
+        
         public ServerContext(ServerCredential cred, ContextAttrib requestedAttribs) : base ( cred )
         {
             this.requestedAttribs = requestedAttribs;
             this.finalAttribs = ContextAttrib.Zero;
-
         }
 
         public SecurityStatus AcceptToken( byte[] clientToken, out byte[] nextToken )
@@ -72,7 +70,7 @@ namespace NSspi.Contexts
             if ( status == SecurityStatus.OK )
             {
                 nextToken = null;
-                this.complete = true;
+                this.Initialized = true;
 
                 if ( outBuffer.Length != 0 )
                 {
@@ -86,7 +84,7 @@ namespace NSspi.Contexts
             }
             else if ( status == SecurityStatus.ContinueNeeded )
             {
-                this.complete = false;
+                this.Initialized = false;
 
                 nextToken = new byte[outBuffer.Length];
                 Array.Copy( outBuffer.Buffer, nextToken, nextToken.Length );