Fixed slot selection in HMAC class to ensure that we are using softtoken instead of TPM slots.

crypto/hmac_nss.cc

Index: crypto/hmac_nss.cc
===================================================================
--- crypto/hmac_nss.cc	(revision 106500)
+++ crypto/hmac_nss.cc	(working copy)
@@ -12,6 +12,10 @@
 #include "crypto/nss_util.h"
 #include "crypto/scoped_nss_types.h"
 
+#if defined(OS_CHROMEOS)
+#include "crypto/nss_util_internal.h"
+#endif
+
 namespace crypto {
 
 struct HMACPlatformData {
@@ -48,7 +52,15 @@
     return false;
   }
 
+#if defined(OS_CHROMEOS)
+  // TODO(zelidrag): http://crosbug.com/21633
+  // For yet unknown reasons, on ChromeOS PK11_GetBestSlot is matching slot from
+  // TPM here on a fresh machine when an account is just created. Need to
+  // investigate what is the underlying cause of this transient behavior.
+  plat_->slot_.reset(GetPublicNSSKeySlot());
+#else
   plat_->slot_.reset(PK11_GetBestSlot(plat_->mechanism_, NULL));

[wtc, 2011/10/22 22:58:23]

Please try
    plat_->slot_.reset(PK11_GetInternalSlot());

If that works, that's my preferred solution.

PK11_GetInternalSlot() returns a slot in the NSS soft token
that does not need the NSS cert/key databases.  Since we
don't need to store the HMAC key persistently on line 74
below, using this slot is enough.

+#endif
   if (!plat_->slot_.get()) {
     NOTREACHED();
     return false;