g: extension: Add a whitelist for vendor commands.

The USB FW upgrade endpoint should really only accept vendor commands
required to perform the firmware update.  This commit adds a whitelist
that is checked whenever a vendor command is received over this
endpoint.

The allowed commands over USB are the following:

 - EXTENSION_POST_RESET
 - VENDOR_CC_IMMEDIATE_RESET (only for dev images)

There is also functionality to have a whitelist for vendor commands that
come over the TPM interface.

BUG=chrome-os-partner:62815
BRANCH=None
TEST=Flash Cr50 with image containing this change.  Verify that an
upgrade over USB to newer image works.
TEST=Try using usb_updater to send a vendor command that's not in the
whitelist.  Verify that the vendor command is dropped.

Change-Id: I71f8ba090a1cc6c9e7c30ce0dd3c25259e8f292f
Signed-off-by: Aseda Aboagye <aaboagye@google.com>
Reviewed-on: https://chromium-review.googlesource.com/443447
Commit-Ready: Aseda Aboagye <aaboagye@chromium.org>
Tested-by: Aseda Aboagye <aaboagye@chromium.org>
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>

1 files changed, 13 insertions, 5 deletions

diff --git a/include/extension.h b/include/extension.h
index 3b960f5439..28a0dc7d06 100644
--- a/include/extension.h
+++ b/include/extension.h
@@ -26,8 +26,12 @@ typedef enum vendor_cmd_rc (*extension_handler)(enum vendor_cmd_cc code,
 						size_t command_size,
 						size_t *response_size);
 
-/*
+/**
  * Find handler for an extension command.
+ *
+ * Use the interface specific function call in order to check the policies for
+ * handling the commands on that interface.
+ *
  * @param command_code Code associated with a extension command handler.
  * @param buffer       Data to be processd by the handler, the same space
  *                     is used for data returned by the handler.
@@ -36,10 +40,14 @@ typedef enum vendor_cmd_rc (*extension_handler)(enum vendor_cmd_cc code,
  *                     data returned by the handler. A single byte return
  *                     usually indicates an error and contains the error code.
  */
-uint32_t extension_route_command(uint16_t command_code,
-				 void *buffer,
-				 size_t command_size,
-				 size_t *size);
+uint32_t usb_extension_route_command(uint16_t command_code,
+				     void *buffer,
+				     size_t command_size,
+				     size_t *size);
+uint32_t tpm_extension_route_command(uint16_t command_code,
+				     void *buffer,
+				     size_t command_size,
+				     size_t *size);
 
 /* Pointer table */
 struct extension_command {