Merge pull request jetheredge#156 from AlexCuse/master

Changes to Mutex Code for Lower-Trust Environments
buddydvd · Feb 23, 2012 · 93a0efc · 93a0efc
2 parents fb91998 + fb6dbe6
commit 93a0efc
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Showing 3 changed files with 66 additions and 15 deletions.
diff --git a/SquishIt.Framework/Base/BundleBase.cs b/SquishIt.Framework/Base/BundleBase.cs
@@ -2,7 +2,6 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
-using System.Threading;
 using System.Web;
 using SquishIt.Framework.Minifiers;
 using SquishIt.Framework.Resolvers;
@@ -41,13 +40,6 @@ protected IMinifier<T> Minifier
             set { minifier = value; }
         }
 
-        private IFilePathMutexProvider mutexProvider;
-        protected IFilePathMutexProvider MutexProvider
-        {
-            get { return mutexProvider ?? (mutexProvider = FilePathMutexProvider.Instance); }
-            set { mutexProvider = value; }
-        }
-
         protected string HashKeyName { get; set; }
         private bool ShouldRenderOnlyIfOutputFileIsMissing { get; set; }
         internal List<string> DependentFiles = new List<string>();
@@ -404,9 +396,7 @@ private string RenderRelease(string key, string renderTo, IRenderer renderer)
             string content;
             if (!bundleCache.TryGetValue(key, out content))
             {
-                var renderMutex = MutexProvider.GetMutexForPath(renderTo);
-                renderMutex.WaitOne();
-                try
+                using(new CriticalRenderingSection(renderTo))
                 {
                     if (!bundleCache.TryGetValue(key, out content))
                     {
@@ -498,10 +488,6 @@ private string RenderRelease(string key, string renderTo, IRenderer renderer)
                         content += String.Concat(GetFilesForRemote(remoteAssetPaths, bundleState), renderedTag);
                     }
                 }
-                finally
-                {
-                    renderMutex.ReleaseMutex();
-                }
                 bundleCache.Add(key, content, DependentFiles);
             }
 

diff --git a/SquishIt.Framework/SquishIt.Framework.csproj b/SquishIt.Framework/SquishIt.Framework.csproj
@@ -88,6 +88,7 @@
     <Compile Include="Base\BundleState.cs" />
     <Compile Include="Base\IBundle.cs" />
     <Compile Include="Coffee\CoffeescriptCompiler.cs" />
+    <Compile Include="Utilities\CriticalRenderingSection.cs" />
     <Compile Include="Extensions.cs" />
     <Compile Include="IBundleCache.cs" />
     <Compile Include="Minifiers\IMinifier.cs" />

diff --git a/SquishIt.Framework/Utilities/CriticalRenderingSection.cs b/SquishIt.Framework/Utilities/CriticalRenderingSection.cs
@@ -0,0 +1,64 @@
+using System;
+using System.Threading;
+using System.Web;
+namespace SquishIt.Framework.Utilities 
+{
+    public class CriticalRenderingSection : IDisposable {
+        // this feels a bit like IDisposable abuse but allows us to code BundleBase in a more mutex-agnostic fashion
+        // probably acceptable alternative for try .. finally though
+        private IFilePathMutexProvider mutexProvider;
+        protected IFilePathMutexProvider MutexProvider 
+        {
+            get { return mutexProvider ?? (mutexProvider = FilePathMutexProvider.Instance); }
+            set { mutexProvider = value; }
+        }
+
+        Mutex mutex;
+        public CriticalRenderingSection(string path) 
+        {
+            if (IsHighOrUnrestrictedTrust) 
+            {
+                mutex = MutexProvider.GetMutexForPath(path);
+                mutex.WaitOne();
+            }
+        }
+
+        public void Dispose() 
+        {
+            if (IsHighOrUnrestrictedTrust) 
+            {
+                mutex.ReleaseMutex();
+            }
+        }
+
+        bool IsHighOrUnrestrictedTrust 
+        {
+            get { return trustLevel == AspNetHostingPermissionLevel.High || trustLevel == AspNetHostingPermissionLevel.Unrestricted; }
+        }
+
+        AspNetHostingPermissionLevel trustLevel = GetCurrentTrustLevel();
+
+        static AspNetHostingPermissionLevel GetCurrentTrustLevel() 
+        {
+            var lastTrustedLevel = AspNetHostingPermissionLevel.None;
+
+            foreach (AspNetHostingPermissionLevel level in new[] {
+                AspNetHostingPermissionLevel.Minimal,
+                AspNetHostingPermissionLevel.Low,
+                AspNetHostingPermissionLevel.Medium,
+                AspNetHostingPermissionLevel.High,
+                AspNetHostingPermissionLevel.Unrestricted }) 
+            {
+                try {
+                    new AspNetHostingPermission(level).Demand();
+                    lastTrustedLevel = level;
+                }
+                catch (System.Security.SecurityException) {
+                    break;
+                }
+            }
+
+            return lastTrustedLevel;
+        }
+    }
+}