Implement SharedMemory::NewAnonymousReadOnly(contents).

base/memory/shared_memory.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_MEMORY_SHARED_MEMORY_H_
 #define BASE_MEMORY_SHARED_MEMORY_H_
 
 #include "build/build_config.h"
 
 #include <string>
 
 #if defined(OS_POSIX)
 #include <stdio.h>
 #include <sys/types.h>
 #include <semaphore.h>
 #endif
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/process/process_handle.h"
 
 #if defined(OS_POSIX)
 #include "base/file_descriptor_posix.h"
 #endif
 
 namespace base {
 
 class FilePath;
 
@@ skipping 43 matching lines @@
 
 #if defined(OS_WIN)
   // Similar to the default constructor, except that this allows for
   // calling Lock() to acquire the named mutex before either Create or Open
   // are called on Windows.
   explicit SharedMemory(const std::wstring& name);
 #endif
 
   // Create a new SharedMemory object from an existing, open
   // shared memory file.
+  //
+  // WARNING: This does not reduce the OS-level permissions on the handle; it
+  // only affects how the SharedMemory will be mmapped.  TODO(jln,jyasskin):
+  // remove this overload or DCHECK that read_only matches the permissions of
+  // the handle.
   SharedMemory(SharedMemoryHandle handle, bool read_only);
 
   // Create a new SharedMemory object from an existing, open
   // shared memory file that was created by a remote process and not shared
   // to the current process.
   SharedMemory(SharedMemoryHandle handle, bool read_only,
                ProcessHandle process);
 
   // Closes any open files.
   ~SharedMemory();
 
   // Return true iff the given handle is valid (i.e. not the distingished
   // invalid value; NULL for a HANDLE and -1 for a file descriptor)
   static bool IsHandleValid(const SharedMemoryHandle& handle);
 
   // Returns invalid handle (see comment above for exact definition).
   static SharedMemoryHandle NULLHandle();
 
   // Closes a shared memory handle.
   static void CloseHandle(const SharedMemoryHandle& handle);
 
   // Returns the maximum number of handles that can be open at once per process.
   static size_t GetHandleLimit();
 
+  // Returns a new, read-only, unmapped SharedMemory with |contents| written
+  // into it.  Use this to send data to untrusted processes.  Returns NULL if
+  // creation fails.
+  static scoped_ptr<SharedMemory> NewAnonymousReadOnly(StringPiece contents);
+
   // Creates a shared memory object as described by the options struct.
   // Returns true on success and false on failure.
   bool Create(const SharedMemoryCreateOptions& options);
 
   // Creates and maps an anonymous shared memory segment of size size.
   // Returns true on success and false on failure.
   bool CreateAndMapAnonymous(size_t size);
 
   // Creates an anonymous shared memory segment of size size.
   // Returns true on success and false on failure.
@@ skipping 155 matching lines @@
   }
 
  private:
   SharedMemory* shared_memory_;
   DISALLOW_COPY_AND_ASSIGN(SharedMemoryAutoLock);
 };
 
 }  // namespace base
 
 #endif  // BASE_MEMORY_SHARED_MEMORY_H_