间歇性无法加载文件或程序集/PolicyExceptions

Question

我们会间歇性地从 .NET 3.5 Web 应用程序中收到类似的错误：

Exception:
System.Configuration.ConfigurationErrorsException: Could not load file or assembly 'itextsharp, Version=4.1.2.0, Culture=neutral, PublicKeyToken=8354ae6d2174ddca' or one of its dependencies. Failed to grant permission to execute. (Exception from HRESULT: 0x80131418) (C:\Windows\Microsoft.NET\Framework64\v2.0.50727\Config\web.config line 59) ---> System.IO.FileLoadException: Could not load file or assembly 'itextsharp, Version=4.1.2.0, Culture=neutral, PublicKeyToken=8354ae6d2174ddca' or one of its dependencies. Failed to grant permission to execute. (Exception from HRESULT: 0x80131418) File name: 'itextsharp, Version=4.1.2.0, Culture=neutral, PublicKeyToken=8354ae6d2174ddca' ---> System.Security.Policy.PolicyException: Execution permission cannot be acquired.
   at System.Security.SecurityManager.ResolvePolicy(Evidence evidence, PermissionSet reqdPset, PermissionSet optPset, PermissionSet denyPset, PermissionSet& denied, Boolean checkExecutionPermission)
   at System.Security.SecurityManager.ResolvePolicy(Evidence evidence, PermissionSet reqdPset, PermissionSet optPset, PermissionSet denyPset, PermissionSet& denied, Int32& securitySpecialFlags, Boolean checkExecutionPermission)
   at System.Reflection.Assembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)
   at System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
   at System.Reflection.Assembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
   at System.Reflection.Assembly.Load(String assemblyString)
   at System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective)


   --- End of inner exception stack trace ---
   at System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective)
   at System.Web.Configuration.CompilationSection.LoadAllAssembliesFromAppDomainBinDirectory()
   at System.Web.Configuration.CompilationSection.LoadAssembly(AssemblyInfo ai)
   at System.Web.Configuration.AssemblyInfo.get_AssemblyInternal()
   at System.Web.Compilation.BuildManager.GetReferencedAssemblies(CompilationSection compConfig)
   at System.Web.Compilation.WebDirectoryBatchCompiler..ctor(VirtualDirectory vdir)
   at System.Web.Compilation.BuildManager.BatchCompileWebDirectoryInternal(VirtualDirectory vdir, Boolean ignoreErrors)
   at System.Web.Compilation.BuildManager.CompileWebFile(VirtualPath virtualPath)
   at System.Web.Compilation.BuildManager.GetVPathBuildResultInternal(VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile)
   at System.Web.Compilation.BuildManager.GetVPathBuildResultWithNoAssert(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile)
   at System.Web.Compilation.BuildManager.GetVirtualPathObjectFactory(VirtualPath virtualPath, HttpContext context, Boolean allowCrossApp, Boolean noAssert)
   at System.Web.Compilation.BuildManager.GetCompiledType(String virtualPath)
   at System.Web.Script.Services.WebServiceData.GetWebServiceData(HttpContext context, String virtualPath, Boolean failIfNoData, Boolean pageMethods, Boolean inlineScript)
   at System.Web.Script.Services.RestHandler.CreateHandler(HttpContext context)
   at System.Web.Script.Services.ScriptHandlerFactory.GetHandler(HttpContext context, String requestType, String url, String pathTranslated)
   at System.Web.HttpApplication.MaterializeHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Inner exception:
System.IO.FileLoadException: Could not load file or assembly 'itextsharp, Version=4.1.2.0, Culture=neutral, PublicKeyToken=8354ae6d2174ddca' or one of its dependencies. Failed to grant permission to execute. (Exception from HRESULT: 0x80131418) File name: 'itextsharp, Version=4.1.2.0, Culture=neutral, PublicKeyToken=8354ae6d2174ddca' ---> System.Security.Policy.PolicyException: Execution permission cannot be acquired.
   at System.Security.SecurityManager.ResolvePolicy(Evidence evidence, PermissionSet reqdPset, PermissionSet optPset, PermissionSet denyPset, PermissionSet& denied, Boolean checkExecutionPermission)
   at System.Security.SecurityManager.ResolvePolicy(Evidence evidence, PermissionSet reqdPset, PermissionSet optPset, PermissionSet denyPset, PermissionSet& denied, Int32& securitySpecialFlags, Boolean checkExecutionPermission)
   at System.Reflection.Assembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)
   at System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
   at System.Reflection.Assembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
   at System.Reflection.Assembly.Load(String assemblyString)
   at System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective)

web.config 第 59 行是：

<add assembly="*"/>

当这些发生时，网站将 YSOD 直到我们回收应用程序池。这些站点可能会在此发生之前运行数天/数周，或者可能在一小时内发生两次。我无法确定这与我们系统中的任何特定请求/功能有关。

在这种情况下，它指向 itextsharp，但它随机指向我们的应用程序引用的任何程序集，包括内部和外部。

运行 caspol 验证 DLL 是否具有完全信任权限：

C:\Windows\Microsoft.NET\Framework64\v2.0.50727>caspol -rsg D:\...\bin\itextsharp.dll
Microsoft (R) .NET Framework CasPol 2.0.50727.3053
Copyright (c) Microsoft Corporation.  All rights reserved.

Level = Enterprise

Code Groups:

1.  All code: FullTrust


Level = Machine

Code Groups:

1.  All code: Nothing
   1.1.  Zone - MyComputer: FullTrust


Level = User

Code Groups:

1.  All code: FullTrust

Success

我们的应用程序在三台服务器上运行，其中两台在 Server 2008 Web x64 上，第三台在 Server 2008 R2 Web x64 上运行，都安装了 .NET 3.5，没有安装 .NET 4.0。

问题仅在运行 2008 非 R2 的前两个上出现。

在所有三台服务器上运行 depends.exe 会为非 R2 服务器提供相同的结果：

• 我的 DLL 显示为 x86（编译为 AnyCPU，在 x64 w3wp 中运行），所有其他模块显示为 x64。
• 缺少 IESHIMS.DLL 和 LINKINFO.DLL - 根据 Google 的说法，这两个似乎都是红鲱鱼。

第三台服务器显示相同，除了它没有错过 LINKINFO.DLL

所有服务器都在已被授予必要权限的自定义域帐户下运行 IIS7（R2 为 7.5）：

aspnet_regiis -ga [user]

加载用户配置文件在所有三台服务器上都设置为 false。根据以下内容，我已尝试在其中一台故障服务器上将其设置为 true： IIS7 Failed to grant minimum permission requests

通过运行 processmonitor，我可以看到它现在使用 C:\Users\TEMP\AppData\Local\Temp 目录来存储各种临时文件 - 其他的没有使用任何这样的目录。到目前为止，我会让它以这种方式运行，看看这是否会改变任何东西。但是，鉴于第三台服务器没有出现问题，我对此表示怀疑，但仍然将“加载用户配置文件”设置为相同的值，即 false。

我还尝试在所有三台服务器上运行 Fuslogvw，将绑定失败记录到磁盘。所有三台服务器都报告了相同的 VJSharpCodeProvider 和 CppCodeProvider 绑定错误，但这些似乎也很正常，可以通过在构建期间不定义 DEBUG 和 TRACE 常量来解决。

我们在每台服务器上运行大约 500 个网站（相同，负载平衡），其中 50 个处于中等负载下，但是在高负载和最小负载下都会出现问题。

现在我正在等待错误再次发生，以便我希望看到一种模式并确定“加载用户配置文件”是否可以缓解问题。在此期间任何建议都将非常受欢迎！另外，我不明白缺少“加载用户配置文件”会如何导致这样的问题？更进一步，它看起来如何在 R2 上运行，但在普通 2008 上却不行？

谢谢！

Answer 1

可能是运行时如何定位程序集及其对负载平衡环境的影响的问题。

您可以尝试使用<probing> 元素指定从何处检索程序集。

<configuration>
   <runtime>
      <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
         <probing privatePath="bin;bin2\subbin;bin3"/>
      </assemblyBinding>
   </runtime>
</configuration>

编辑：

试试这个：

<configuration>
   <runtime>
      <disableCachingBindingFailures enabled="1" />
   </runtime>
</configuration>