title: Access Violations with ODP.net under Medium Trust
body: <p>Environment:</p>
  
  <pre><code>Windows Server 2008 R2
  IIS 7.5
  .NET 4.0, Integrated Application Pool
  Oracle Client 11.2.0.2.0
  ODP.net 11.2.0.2.3
  </code></pre>
  
  <p>I have a website that uses ODP.net to connect to our Oracle database, and under "Full Trust", the application works flawlessly. However, when I change the application to use "Medium Trust", I start getting inconsistent NullReferenceExceptions from the application. Most of the time the code works, but every 10 requests or so I get the NullReferenceException. Upon looking in the event log, I see that the NullRefernceException normally corresponds to a w3wp.exe crash.</p>
  
  <pre><code>Faulting application name: w3wp.exe, version: 7.5.7601.17514, time stamp: 0x4ce7afa2
  Faulting module name: OraOps11w.dll, version: 2.112.2.0, time stamp: 0x4cea1904
  Exception code: 0xc0000005
  Fault offset: 0x0000000000024d56
  Faulting process id: 0x3ba4
  Faulting application start time: 0x01ccdf556d68384a
  Faulting application path: c:\windows\system32\inetsrv\w3wp.exe
  Faulting module path: C:\Oracle64\product\11.2.0\client\bin\OraOps11w.dll1
  </code></pre>
  
  <p>Obviously the issue is ODP.NET, but why is it crashing w3wp.exe in "Medium Trust". So, to try to make sure I wasn't doing something wrong in my code, I wrote the simplest of ASP.NET web applications:</p>
  
  <pre><code>protected void Page_Load(object sender, EventArgs e) {
      using(OracleConnection conn = new OracleConnection(GetMyConnectionString())){
          using (OracleCommand cmd = new OracleCommand("select localtimestamp from dual", conn)) {
              conn.Open();
              this.aLiteral.Text = ((DateTime)cmd.ExecuteScalar()).ToLongDateString();
          }            
      }
  }
  </code></pre>
  
  <p>Under "Full Trust" the app works fine. Under "Medium Trust", the app appears to work fine, but when I hook up the IIS Debug Diagnostic Tool to the app's application pool, the app is throwing thousands of these errors:</p>
  
  <pre><code>[1/30/2012 12:50:25 PM] First chance exception - 0xe0434352 caused by thread with  System ID: 14832
  [1/30/2012 12:50:25 PM] Stack Trace
  RetAddr           : Args to Child                                                           : Call Site
  000007fe`f9990845 : 00000000`04af0ed0 00000000`00000001 00000000`00000000 00000001`bfe3a0b8 : KERNELBASE!RaiseException+0x3d
  000007fe`f9993226 : 00000001`bfe3a0b8 00000000`00000000 00000001`bfe3a0b8 00000001`bfe3a0b8 : clr!PreBindAssemblyEx+0x61681
  000007fe`f7a61233 : 00000000`00000000 00000000`00000000 00000001`bfdca3b0 00000000`00000000 : clr!PreBindAssemblyEx+0x64062
  000007fe`f7a61515 : 00000000`ffd5c9b8 00000000`ffd5c9b8 00000000`ffd5c9b8 00000000`00000000 : mscorlib_ni+0x9f1233
  000007fe`f7b0f6e2 : 00000001`bfdca3b0 00000000`00000000 00000000`ffd5c9b8 00000000`ffd5c9b8 : mscorlib_ni+0x9f1515
  000007fe`f9859714 : 00000001`3fb39a28 00000000`00000000 00000000`00000000 00000000`ffd5c9b8 : mscorlib_ni+0xa9f6e2
  000007fe`f9859829 : 00000000`00000000 00000000`00000000 00000000`00000001 00000000`00000000 : clr!LogHelp_LogAssert+0x25a04
  000007fe`f985bb74 : 00000000`0fb2d450 00000000`00000008 000007fe`f7a602e0 00000000`00000000 : clr!LogHelp_LogAssert+0x25b19
  000007fe`f985c39c : 00000000`00000000 00000000`00000000 00001f80`0010000b 0053002b`002b0033 : clr!LogHelp_LogAssert+0x27e64
  000007fe`f9da3ea1 : 00000000`00000000 00000000`0fb2d700 00000000`04af0ed0 00000000`0257ffc0 : clr!LogHelp_LogAssert+0x2868c
  000007fe`f9da42e5 : 00000000`00000000 00000000`0fb2e600 00000000`04af0ed0 00000001`3fb39a28 : clr!GetAssemblyIdentityFromFile+0x2aa81
  000007fe`f9da454d : 00000000`04af0ed0 00000000`00000000 00000001`3fb39a28 00000000`04af0ed0 : clr!GetAssemblyIdentityFromFile+0x2aec5
  000007fe`f9da4aac : 00000000`ffd5c9b8 00000000`00000000 00000000`04af0ed0 00000000`0fb2d630 : clr!GetAssemblyIdentityFromFile+0x2b12d
  000007fe`f9da4b9c : 00000000`0fb2d898 00000000`00000001 00000000`00000000 00000000`00000000 : clr!GetAssemblyIdentityFromFile+0x2b68c
  000007fe`f9c32ecc : 00000000`00000081 00000000`00000000 00000000`00000000 00000000`00000000 : clr!GetAssemblyIdentityFromFile+0x2b77c
  000007fe`f9e97004 : 000007ff`002653f8 00000000`0fb2dda0 000007fe`f6554288 00000000`ffd5c9b8 : clr!CreateAssemblyConfigCookie+0x9f93c
  000007fe`f9ea54e8 : 000007fe`f6554288 00000000`00010400 00000000`00010400 00000000`00000000 : clr!TranslateSecurityAttributes+0x39bb4
  000007fe`f9854b72 : 00000000`04af0ed0 000007fe`f9908c66 000007fe`00000000 00000000`00000000 : clr!TranslateSecurityAttributes+0x48098
  000007fe`f67af41f : 000007ff`001b8140 000007fe`f6554288 00000001`bfdc3360 00000000`0fb2dc08 : clr!LogHelp_LogAssert+0x20e62
  000007fe`f67a38e6 : 00000000`00000000 00000000`00000000 00000000`0fb2dd00 000007fe`f9861052 : System_ni+0x2bf41f
  000007ff`001a5c34 : 000007ff`001b8140 00000000`00000000 00000000`00000000 000007fe`f99de765 : System_ni+0x2b38e6
  000007ff`001a5a12 : 00000001`00000000 000007ff`001b8140 000007ff`001b8140 00000000`0fb2dda0 : 0x7ff`001a5c34
  000007ff`00187109 : 000007ff`00187104 00000000`00000046 00000000`0fb24000 00000000`04af0ed0 : 0x7ff`001a5a12
  000007fe`f73f30c8 : 00000001`3fb398f8 00000001`3fb39990 00000000`00000000 00000000`00000000 : 0x7ff`00187109
  000007fe`f9859714 : 00000000`ffd991a0 00000001`bfdc30d0 00000000`00000000 00000000`00000000 : mscorlib_ni+0x3830c8
  000007fe`f9859829 : 00000000`00000000 00000000`00000000 00000000`00000000 00000000`00000000 : clr!LogHelp_LogAssert+0x25a04
  000007fe`f98598a5 : 00000000`0fb2e038 00000000`00000002 00000000`0fb2e050 00000000`0fb2e248 : clr!LogHelp_LogAssert+0x25b19
  000007fe`f998878a : 00000001`3fb39cd8 00000000`00000000 00000000`0fb2e4b8 00000000`0fb2e2f0 : clr!LogHelp_LogAssert+0x25b95
  000007fe`f99885b1 : 00000001`3fb39cd8 00000000`025800c8 00000000`04af0ed0 00000000`025800c8 : clr!PreBindAssemblyEx+0x595c6
  000007fe`f73e17b1 : 00000001`3fb39990 00000001`bfdc3090 00000001`ffb46070 00000000`00000000 : clr!PreBindAssemblyEx+0x593ed
  000007fe`f73e16fb : 00000001`3fb39990 000007fe`f986200f 00000000`0fb2e558 00000000`00000000 : mscorlib_ni+0x3717b1
  000007fe`f7476e5d : 000007ff`001b2020 00000000`000001be 00000001`3fb39990 00000000`0fb2e8d0 : mscorlib_ni+0x3716fb
  000007fe`f9859714 : 00000001`3fb399b8 000007fe`f9838477 00000000`00000000 00000000`00000000 : mscorlib_ni+0x406e5d
  000007fe`f9859829 : 00000000`00000000 00000000`00000000 000007fe`f7a35cf0 00000000`00000000 : clr!LogHelp_LogAssert+0x25a04
  000007fe`f98598a5 : 00000000`0fb2e8c8 00000000`00000001 00000000`0fb2e8d0 00000000`0fb2eb20 : clr!LogHelp_LogAssert+0x25b19
  000007fe`f9859d88 : 00000000`0fb2eb18 000007fe`f7374860 00000000`0fb2ebb0 000007fe`f713cd7c : clr!LogHelp_LogAssert+0x25b95
  000007fe`f9a198a0 : 00000000`0fb2f380 00000000`0fb2eba0 00000000`0fb2f420 000007fe`f754dea0 : clr!LogHelp_LogAssert+0x26078
  000007fe`f9869402 : 00000000`00000000 00000000`0fb2f380 00000000`04af0ed0 00000000`00000001 : clr!ClrCreateManagedInstance+0x1d00
  000007fe`f9869397 : 00000000`00000000 00000000`770400e0 00000000`0fb2ee60 00000000`00392c70 : clr!LogHelp_LogAssert+0x356f2
  000007fe`f9869304 : 00000000`04af12d0 000007fe`f986a0be ffffffff`fffffffe 00000000`003981f4 : clr!LogHelp_LogAssert+0x35687
  000007fe`f9869604 : 00000000`0fb2f128 00000000`04af0ed0 00000000`00000000 00000000`04af0ed0 : clr!LogHelp_LogAssert+0x355f4
  000007fe`f9c3305a : 00000000`00000000 00000000`02463320 00000000`0257ffc0 000007fe`fd2fb002 : clr!LogHelp_LogAssert+0x358f4
  000007fe`f9869638 : 00000000`00000002 00000000`0fb2f380 00000000`0fb2f380 00000000`04af0ed0 : clr!CreateAssemblyConfigCookie+0x9faca
  000007fe`f9869397 : 00000000`00000000 00000000`04af0ed0 ffffffff`fffffffe 00000000`04af0ed0 : clr!LogHelp_LogAssert+0x35928
  000007fe`f9869304 : 00000000`00000048 00000000`00000001 00000000`00000000 00000000`00000000 : clr!LogHelp_LogAssert+0x35687
  000007fe`f986945b : ffffffff`ffffffff 00000000`04af0ed0 00000000`00000000 00000000`00000000 : clr!LogHelp_LogAssert+0x355f4
  000007fe`f9a196f0 : 00000000`04af0ed0 00000000`0fb2f840 00000000`00000001 00000000`00000000 : clr!LogHelp_LogAssert+0x3574b
  000007fe`f998a7c2 : 00000000`04ac1960 00000000`0fb2f438 00000000`04af0ed0 00000000`00000000 : clr!ClrCreateManagedInstance+0x1b50
  00000000`76e3652d : 00000000`00000000 00000000`00000000 00000000`00000000 00000000`00000000 : clr!PreBindAssemblyEx+0x5b5fe
  00000000`7706c521 : 00000000`00000000 00000000`00000000 00000000`00000000 00000000`00000000 : kernel32!BaseThreadInitThunk+0xd
  00000000`00000000 : 00000000`00000000 00000000`00000000 00000000`00000000 00000000`00000000 : ntdll!RtlUserThreadStart+0x21
  OS Thread Id: 0x39f0 (30)
  Child SP         IP               Call Site
  000000000fb2ced8 000007fefd2fcacd [HelperMethodFrame: 000000000fb2ced8] 
  000000000fb2d020 000007fef7a61233 System.Security.CodeAccessSecurityEngine.ThrowSecurityException(System.Reflection.RuntimeAssembly, System.Security.PermissionSet, System.Security.PermissionSet, System.RuntimeMethodHandleInternal, System.Security.Permissions.SecurityAction, System.Object, System.Security.IPermission)
  000000000fb2d0b0 000007fef7a61515 System.Security.CodeAccessSecurityEngine.CheckHelper(System.Security.PermissionSet, System.Security.PermissionSet, System.Security.CodeAccessPermission, System.Security.PermissionToken, System.RuntimeMethodHandleInternal, System.Object, System.Security.Permissions.SecurityAction, Boolean)
  000000000fb2d120 000007fef7b0f6e2 System.Security.PermissionListSet.CheckDemand(System.Security.CodeAccessPermission, System.Security.PermissionToken, System.RuntimeMethodHandleInternal)
  000000000fb2d518 000007fef9859714 [GCFrame: 000000000fb2d518] 
  000000000fb2d6d0 000007fef9859714 [GCFrame: 000000000fb2d6d0] 
  000000000fb2d828 000007fef9859714 [GCFrame: 000000000fb2d828] 
  000000000fb2d8d8 000007fef9859714 [DebuggerSecurityCodeMarkFrame: 000000000fb2d8d8] 
  000000000fb2d9b8 000007fef9859714 [HelperMethodFrame: 000000000fb2d9b8] System.StubHelpers.StubHelpers.BeginStandalone(IntPtr, IntPtr, Int32)
  000000000fb2dc08 000007fef67af41f [NDirectMethodFrameStandalone: 000000000fb2dc08] Microsoft.Win32.NativeMethods.GetCurrentProcessId()
  000000000fb2dbd0 000007fef67af41f DomainNeutralILStubClass.IL_STUB_PInvoke()
  000000000fb2dc90 000007fef67a38e6 System.Diagnostics.Process.GetCurrentProcess()
  000000000fb2dce0 000007ff001a5c34 Oracle.DataAccess.Client.OracleTuningAgent.GetCurrentVirtualMemorySize()
  000000000fb2dd30 000007ff001a5a12 Oracle.DataAccess.Client.OracleTuningAgent.DoScan()
  000000000fb2dd80 000007ff00187109 Oracle.DataAccess.Client.OracleTuningAgent.TuningFunction()
  000000000fb2de10 000007fef73f30c8 System.Threading.ExecutionContext.runTryCode(System.Object)
  000000000fb2e538 000007fef9859714 [HelperMethodFrame_PROTECTOBJ: 000000000fb2e538] System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode, CleanupCode, System.Object)
  000000000fb2e660 000007fef73e17b1 System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
  000000000fb2e6c0 000007fef73e16fb System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object)
  000000000fb2e710 000007fef7476e5d System.Threading.ThreadHelper.ThreadStart()
  000000000fb2eb68 000007fef9859714 [GCFrame: 000000000fb2eb68] 
  000000000fb2ef50 000007fef9859714 [DebuggerU2MCatchHandlerFrame: 000000000fb2ef50] 
  000000000fb2f128 000007fef9859714 [ContextTransitionFrame: 000000000fb2f128] 
  000000000fb2f310 000007fef9859714 [DebuggerU2MCatchHandlerFrame: 000000000fb2f310]
  </code></pre>
  
  <p>I followed the instructions in the ODP.NET README to add the OraclePermission to the web_mediumtrust.config (32bit and 64bit), but I am still getting the same errors.</p>
  
  <p>Any ideas how to get ODP.NET working correctly with "Medium Trust"?</p>
  
  <p>Here is my web_mediumtrust.config:</p>
  
  <pre><code>&lt;configuration&gt;
    &lt;mscorlib&gt;
      &lt;security&gt;
        &lt;policy&gt;
          &lt;PolicyLevel version="1"&gt;
            &lt;SecurityClasses&gt;
              &lt;SecurityClass Name="AllMembershipCondition" Description="System.Security.Policy.AllMembershipCondition, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="AspNetHostingPermission" Description="System.Web.AspNetHostingPermission, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="DnsPermission" Description="System.Net.DnsPermission, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="EnvironmentPermission" Description="System.Security.Permissions.EnvironmentPermission, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="FileIOPermission" Description="System.Security.Permissions.FileIOPermission, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="FirstMatchCodeGroup" Description="System.Security.Policy.FirstMatchCodeGroup, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="IsolatedStorageFilePermission" Description="System.Security.Permissions.IsolatedStorageFilePermission, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="NamedPermissionSet" Description="System.Security.NamedPermissionSet" /&gt;
              &lt;SecurityClass Name="PrintingPermission" Description="System.Drawing.Printing.PrintingPermission, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" /&gt;
              &lt;SecurityClass Name="SecurityPermission" Description="System.Security.Permissions.SecurityPermission, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="SmtpPermission" Description="System.Net.Mail.SmtpPermission, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="SqlClientPermission" Description="System.Data.SqlClient.SqlClientPermission, System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="StrongNameMembershipCondition" Description="System.Security.Policy.StrongNameMembershipCondition, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="TypeDescriptorPermission" Description="System.Security.Permissions.TypeDescriptorPermission, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="UIPermission" Description="System.Security.Permissions.UIPermission, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="UnionCodeGroup" Description="System.Security.Policy.UnionCodeGroup, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="UrlMembershipCondition" Description="System.Security.Policy.UrlMembershipCondition, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="WebPermission" Description="System.Net.WebPermission, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="ZoneMembershipCondition" Description="System.Security.Policy.ZoneMembershipCondition, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="ReflectionPermission" Description="System.Security.Permissions.ReflectionPermission, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
              &lt;SecurityClass Name="OraclePermission" Description="System.Data.OracleClient.OraclePermission, System.Data.OracleClient, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /&gt;
            &lt;/SecurityClasses&gt;
            &lt;NamedPermissionSets&gt;
              &lt;PermissionSet class="NamedPermissionSet" version="1" Unrestricted="true" Name="FullTrust" Description="Allows full access to all resources" /&gt;
              &lt;PermissionSet class="NamedPermissionSet" version="1" Name="Nothing" Description="Denies all resources, including the right to execute" /&gt;
              &lt;PermissionSet class="NamedPermissionSet" version="1" Name="ASP.Net"&gt;
                &lt;IPermission class="AspNetHostingPermission" version="1" Level="Medium" /&gt;
                &lt;IPermission class="DnsPermission" version="1" Unrestricted="true" /&gt;
                &lt;IPermission class="EnvironmentPermission" version="1" Read="TEMP;TMP;USERNAME;OS;COMPUTERNAME" /&gt;
                &lt;IPermission class="FileIOPermission" version="1" Read="$AppDir$" Write="$AppDir$" Append="$AppDir$" PathDiscovery="$AppDir$" /&gt;
                &lt;IPermission class="IsolatedStorageFilePermission" version="1" Allowed="AssemblyIsolationByUser" UserQuota="9223372036854775807" /&gt;
                &lt;IPermission class="PrintingPermission" version="1" Level="DefaultPrinting" /&gt;
                &lt;IPermission class="SecurityPermission" version="1" Flags="Execution, ControlThread, ControlPrincipal, RemotingConfiguration" /&gt;
                &lt;IPermission class="SmtpPermission" version="1" Access="Connect" /&gt;
                &lt;IPermission class="SqlClientPermission" version="1" Unrestricted="true" /&gt;
                &lt;IPermission class="TypeDescriptorPermission" version="1" Unrestricted="true" /&gt;
                &lt;IPermission class="WebPermission" version="1" Unrestricted="true" /&gt;
                &lt;IPermission class="ReflectionPermission" version="1" Flags="RestrictedMemberAccess" /&gt;
                &lt;IPermission class="OraclePermission" version="1" Unrestricted="true" /&gt;
                &lt;IPermission class="Oracle.DataAccess.Client.OraclePermission, Oracle.DataAccess, Version=4.112.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342" version="1" Unrestricted="true" /&gt;
              &lt;/PermissionSet&gt;
            &lt;/NamedPermissionSets&gt;
            &lt;CodeGroup class="FirstMatchCodeGroup" version="1" PermissionSetName="Nothing"&gt;
              &lt;IMembershipCondition class="AllMembershipCondition" version="1" /&gt;
              &lt;CodeGroup class="UnionCodeGroup" version="1" PermissionSetName="ASP.Net"&gt;
                &lt;IMembershipCondition class="UrlMembershipCondition" version="1" Url="$AppDirUrl$/*" /&gt;
              &lt;/CodeGroup&gt;
              &lt;CodeGroup class="UnionCodeGroup" version="1" PermissionSetName="ASP.Net"&gt;
                &lt;IMembershipCondition class="UrlMembershipCondition" version="1" Url="$CodeGen$/*" /&gt;
              &lt;/CodeGroup&gt;
            &lt;/CodeGroup&gt;
          &lt;/PolicyLevel&gt;
        &lt;/policy&gt;
      &lt;/security&gt;
    &lt;/mscorlib&gt;
  &lt;/configuration&gt;
  </code></pre>