Add method to get random bytes from the TPM.

tpm.h

 // Copyright (c) 2009-2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Tpm - class for handling init TPM initialization for Chrome OS
 
 #include <base/lock.h>
 #include <base/logging.h>
 #include <base/scoped_ptr.h>
 #include <chromeos/utility.h>
@@ skipping 50 matching lines @@
   // currently being taken (such as on a separate thread).
   bool IsOwned() const { return is_owned_; }
 
   // Returns whether or not the SRK is available
   bool IsSrkAvailable() const { return is_srk_available_; }
 
   // Runs the TPM initialization sequence.  This may take a long time due to the
   // call to Tspi_TPM_TakeOwnership.
   bool InitializeTpm();
 
+  // Gets random bytes from the TPM
+  //
+  // Parameters
+  //   length - The number of bytes to get
+  //   data (OUT) - The random data from the TPM
+  bool GetRandomData(size_t length, chromeos::Blob* data);
+
  private:
   // Attempts to connect to tcsd
   //
   // Parameters
   //   context_handle (OUT) - The context handle to the session on success
   bool OpenAndConnectTpm(TSS_HCONTEXT* context_handle);
 
   // Returns the maximum simultaneously-loaded RSA key count for the TPM
   // specified by the context handle
   //
@@ skipping 122 matching lines @@
 
   // Indicates if the SRK is available
   bool is_srk_available_;
 
   DISALLOW_COPY_AND_ASSIGN(Tpm);
 };
 
 }  // namespace tpm_init
 
 #endif  // TPM_INIT_TPM_H_