Fix named pipe security on Windows 7

src/shared/Communication.cpp

 #include <Windows.h>
 #include <Lmcons.h>
 #include <Sddl.h>
 #include <aclapi.h>
 #include <strsafe.h>
 
 #include "AutoHandle.h"
 #include "Communication.h"
 #include "Utils.h"
 
@@ skipping 79 matching lines @@
               &allAppContainersSid);
       std::tr1::shared_ptr<SID> sharedAllAppContainersSid(static_cast<SID*>(allAppContainersSid), FreeSid); // Just to simplify cleanup
 
       explicitAccess[1].grfAccessPermissions = STANDARD_RIGHTS_ALL | SPECIFIC_RIGHTS_ALL;
       explicitAccess[1].grfAccessMode = SET_ACCESS;
       explicitAccess[1].grfInheritance= NO_INHERITANCE;
       explicitAccess[1].Trustee.TrusteeForm = TRUSTEE_IS_SID;
       explicitAccess[1].Trustee.TrusteeType = TRUSTEE_IS_GROUP;
       explicitAccess[1].Trustee.ptstrName = static_cast<LPWSTR>(allAppContainersSid);
 
+      // Will be released later
       PACL acl = 0;
-      // acl has to be released after this
       if (SetEntriesInAcl(2, explicitAccess, 0, &acl) != ERROR_SUCCESS)
         return std::auto_ptr<SECURITY_DESCRIPTOR>(0);
 
-      // This only references the acl, not copies it
+      // NOTE: This only references the acl, not copies it. 
+      // DO NOT release the ACL before it's actually used
       if (!SetSecurityDescriptorDacl(securityDescriptor.get(), TRUE, acl, FALSE))
         return std::auto_ptr<SECURITY_DESCRIPTOR>(0);
     }
 
-    // Create a dummy security descriptor with low integrirty preset and copy its SACL into ours
+    // Create a dummy security descriptor with low integrirty preset and refference its SACL in ours

[Felix Dahlke, 2014/07/16 14:40:03]

s/refference/reference/

[Oleksandr, 2014/07/17 17:32:48]

Um. Refference is meant to be a verb here. 
On 2014/07/16 14:40:03, Felix H. Dahlke wrote:

[Felix Dahlke, 2014/07/18 12:40:57]

But it's still one f too many! :)

[Oleksandr, 2014/07/18 12:48:34]

Oh. Totally missread your correction. 
On 2014/07/18 12:40:57, Felix H. Dahlke wrote:

     LPCWSTR accessControlEntry = L"S:(ML;;NW;;;LW)";
     PSECURITY_DESCRIPTOR dummySecurityDescriptorLow;
     ConvertStringSecurityDescriptorToSecurityDescriptorW(accessControlEntry, SDDL_REVISION_1, &dummySecurityDescriptorLow, 0);
     std::tr1::shared_ptr<SECURITY_DESCRIPTOR> sharedDummySecurityDescriptor(static_cast<SECURITY_DESCRIPTOR*>(dummySecurityDescriptorLow), LocalFree); // Just to simplify cleanup
-    BOOL saclPresent = FALSE;
-    BOOL saclDefaulted = FALSE;
-    PACL sacl;
-    GetSecurityDescriptorSacl(dummySecurityDescriptorLow, &saclPresent, &sacl, &saclDefaulted);
-    if (saclPresent)
+
+    DWORD sdSize, saclSize, daclSize, ownerSize, primaryGroupSize;

[Felix Dahlke, 2014/07/16 14:40:03]

Shouldn't we initialise all the sizes to 0 here? Should be garbage currently.

+    MakeAbsoluteSD(dummySecurityDescriptorLow, 0, &sdSize, 0, &daclSize, 0, &saclSize, 0, &ownerSize, 0, &primaryGroupSize);
+    if ((saclSize == 0) || (sdSize == 0))

[Felix Dahlke, 2014/07/16 14:40:03]

Redundant parentheses around both comparisons.

     {
-      if (!SetSecurityDescriptorSacl(securityDescriptor.get(), TRUE, sacl, FALSE))
-      {
         DWORD err = GetLastError();

[Felix Dahlke, 2014/07/16 14:40:03]

Unused variable.

         return std::auto_ptr<SECURITY_DESCRIPTOR>(0);
-      }
+    }
+    // Will be released later
+    PACL sacl = (PACL) new byte[saclSize];

[Felix Dahlke, 2014/07/16 14:40:03]

I'd actually find malloc more intuitive here. byte is not a standard type. Also,
C++-style cast please :)

Same below.

+    std::auto_ptr<SECURITY_DESCRIPTOR> absoluteDummySecurityDescriptorLow((SECURITY_DESCRIPTOR*) new byte[sdSize]);
+    daclSize = 0;
+    ownerSize = 0;
+    primaryGroupSize = 0;
+    BOOL res = MakeAbsoluteSD(dummySecurityDescriptorLow, absoluteDummySecurityDescriptorLow.get(), &sdSize, 0, &daclSize, sacl, &saclSize, 0, &ownerSize, 0, &primaryGroupSize);
+    if ((res == 0) || (absoluteDummySecurityDescriptorLow.get() == 0) || (saclSize == 0))

[Felix Dahlke, 2014/07/16 14:40:03]

Redundant parentheses here as well.

Also, !res would be more intuitive here IMO.

+    {
+        DWORD err = GetLastError();

[Felix Dahlke, 2014/07/16 14:40:03]

Also unused.

+        return std::auto_ptr<SECURITY_DESCRIPTOR>(0);
+    }
+
+    // NOTE: This only references the acl, not copies it. 
+    // DO NOT release the ACL before it's actually used
+    if (!SetSecurityDescriptorSacl(securityDescriptor.get(), TRUE, sacl, FALSE))
+    {
+      DWORD err = GetLastError();
+      return std::auto_ptr<SECURITY_DESCRIPTOR>(0);
     }
 
     return securityDescriptor;
   }
 }
 
-  // Releases the DACL structure in the provided security descriptor
-  void ReleaseDacl(PSECURITY_DESCRIPTOR securityDescriptor)
-  {
-    BOOL aclPresent = FALSE;
-    BOOL aclDefaulted = FALSE;
-    PACL acl;
-    GetSecurityDescriptorDacl(securityDescriptor, &aclPresent, &acl, &aclDefaulted);
-    if (aclPresent)
-    {
-      LocalFree(acl);
-    }
-  }
 const std::wstring Communication::pipeName = L"\\\\.\\pipe\\adblockplusengine_" + GetUserName();
 
 void Communication::InputBuffer::CheckType(Communication::ValueType expectedType)
 {
   if (!hasType)
     ReadBinary(currentType);
 
   if (currentType != expectedType)
   {
     // Make sure we don't attempt to read the type again
@@ skipping 21 matching lines @@
 Communication::PipeBusyError::PipeBusyError()
   : std::runtime_error("Timeout while trying to connect to a named pipe, pipe is busy")
 {
 }
 
 Communication::PipeDisconnectedError::PipeDisconnectedError()
   : std::runtime_error("Pipe disconnected")
 {
 }
 
+void FreeAbsoluteSecurityDescriptor(SECURITY_DESCRIPTOR* securityDescriptor)
+{
+  BOOL aclPresent = FALSE;
+  BOOL aclDefaulted = FALSE;
+  PACL acl = 0;
+  GetSecurityDescriptorDacl(securityDescriptor, &aclPresent, &acl, &aclDefaulted);
+  if (aclPresent)
+  {
+    LocalFree(acl);
+  }
+  aclPresent = FALSE;
+  aclDefaulted = false;

[Felix Dahlke, 2014/07/16 14:40:03]

Should also be that Windows FALSE macro for consistency.

+  acl = 0;
+  GetSecurityDescriptorSacl(securityDescriptor, &aclPresent, &acl, &aclDefaulted);
+  if (aclPresent)
+  {
+    delete acl;

[Felix Dahlke, 2014/07/16 14:40:03]

You need to use delete[], since it was allocated using new[]. Same below.

+  }
+  delete securityDescriptor;
+}
+
 Communication::Pipe::Pipe(const std::wstring& pipeName, Communication::Pipe::Mode mode)
 {
   pipe = INVALID_HANDLE_VALUE;
   if (mode == MODE_CREATE)
   {
     SECURITY_ATTRIBUTES securityAttributes = {};
     securityAttributes.nLength = sizeof(SECURITY_ATTRIBUTES);
     securityAttributes.bInheritHandle = TRUE;
 
     std::tr1::shared_ptr<SECURITY_DESCRIPTOR> sharedSecurityDescriptor; // Just to simplify cleanup
-  
     AutoHandle token;
     OpenProcessToken(GetCurrentProcess(), TOKEN_READ, token);
     
     if (IsWindowsVistaOrLater())
     {
       std::auto_ptr<SID> logonSid = GetLogonSid(token);
       // Create a SECURITY_DESCRIPTOR that has both Low Integrity and allows access to all AppContainers
       // This is needed since IE likes to jump out of Enhanced Protected Mode for specific pages (bing.com)
-
-      // ATTENTION: DACL in the returned securityDescriptor has to be manually released by ReleaseDacl
       std::auto_ptr<SECURITY_DESCRIPTOR> securityDescriptor = CreateSecurityDescriptor(logonSid.get());
 
       securityAttributes.lpSecurityDescriptor = securityDescriptor.release();
-      sharedSecurityDescriptor.reset(static_cast<SECURITY_DESCRIPTOR*>(securityAttributes.lpSecurityDescriptor));
+      sharedSecurityDescriptor.reset(static_cast<SECURITY_DESCRIPTOR*>(securityAttributes.lpSecurityDescriptor), FreeAbsoluteSecurityDescriptor);
     }
     pipe = CreateNamedPipeW(pipeName.c_str(),  PIPE_ACCESS_DUPLEX, PIPE_TYPE_MESSAGE | PIPE_READMODE_MESSAGE | PIPE_WAIT,
       PIPE_UNLIMITED_INSTANCES, bufferSize, bufferSize, 0, &securityAttributes);
-
-    if (IsWindowsVistaOrLater())
-    {
-      ReleaseDacl(securityAttributes.lpSecurityDescriptor);
-    }
   }
   else
   {
     pipe = CreateFileW(pipeName.c_str(), GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, 0, 0);
     if (pipe == INVALID_HANDLE_VALUE && GetLastError() == ERROR_PIPE_BUSY)
     {
       if (!WaitNamedPipeW(pipeName.c_str(), 10000))
         throw PipeBusyError();
 
       pipe = CreateFileW(pipeName.c_str(), GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, 0, 0);
@@ skipping 49 matching lines @@
   return Communication::InputBuffer(stream.str());
 }
 
 void Communication::Pipe::WriteMessage(Communication::OutputBuffer& message)
 {
   DWORD bytesWritten;
   std::string data = message.Get();
   if (!WriteFile(pipe, data.c_str(), static_cast<DWORD>(data.length()), &bytesWritten, 0))
     throw std::runtime_error("Failed to write to pipe");
 }