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>

chip/g/usb_upgrade.c

@@ -152,11 +152,11 @@ static int try_vendor_command(struct consumer const *consumer, size_t count)
 		queue_advance_head(consumer->queue, count);
 
 		subcommand = (uint16_t *)(cmd_buffer + 1);
-		extension_route_command(be16toh(*subcommand),
-					subcommand + 1,
-					count -
-					sizeof(struct update_frame_header),
-					&response_size);
+		usb_extension_route_command(be16toh(*subcommand),
+					    subcommand + 1,
+					    count -
+					    sizeof(struct update_frame_header),
+					    &response_size);
 
 		QUEUE_ADD_UNITS(&upgrade_to_usb, subcommand + 1, response_size);
 	}

common/extension.c

@@ -10,10 +10,10 @@
 
 #define CPRINTF(format, args...) cprintf(CC_EXTENSION, format, ## args)
 
-uint32_t extension_route_command(uint16_t command_code,
-				 void *buffer,
-				 size_t in_size,
-				 size_t *out_size)
+static uint32_t extension_route_command(uint16_t command_code,
+					void *buffer,
+					size_t in_size,
+					size_t *out_size)
 {
 	struct extension_command *cmd_p;
 	struct extension_command *end_p;
@@ -34,3 +34,43 @@ uint32_t extension_route_command(uint16_t command_code,
 	*out_size = 0;
 	return VENDOR_RC_NO_SUCH_COMMAND;
 }
+
+uint32_t usb_extension_route_command(uint16_t command_code,
+				     void *buffer,
+				     size_t in_size,
+				     size_t *out_size)
+{
+	int is_allowed = 0;
+
+	switch (command_code) {
+#ifdef CR50_DEV
+	case VENDOR_CC_IMMEDIATE_RESET:
+#endif /* defined(CR50_DEV) */
+	case EXTENSION_POST_RESET: /* Always need to be able to reset. */
+		is_allowed = 1;
+		break;
+
+	default:
+		break;
+	}
+
+	if (is_allowed)
+		return extension_route_command(command_code, buffer, in_size,
+					       out_size);
+
+	/* Otherwise, we don't allow this command. */
+	CPRINTF("%s: ignoring vendor cmd %d\n", __func__, command_code);
+	*out_size = 0;
+	return VENDOR_RC_NO_SUCH_COMMAND;
+}
+
+uint32_t tpm_extension_route_command(uint16_t command_code,
+				     void *buffer,
+				     size_t in_size,
+				     size_t *out_size)
+{
+	/*
+	 * TODO(aaboagye): Determine what commands (if any) should be filtered.
+	 */
+	return extension_route_command(command_code, buffer, in_size, out_size);
+}

common/tpm_registers.c

@@ -626,11 +626,11 @@ static void call_extension_command(struct tpm_cmd_header *tpmh,
 		*total_size -= sizeof(struct tpm_cmd_header);
 
 		subcommand_code = be16toh(tpmh->subcommand_code);
-		rc = extension_route_command(subcommand_code,
-					     tpmh + 1,
-					     command_size -
-					     sizeof(struct tpm_cmd_header),
-					     total_size);
+		rc = tpm_extension_route_command(subcommand_code,
+						 tpmh + 1,
+						 command_size -
+						 sizeof(struct tpm_cmd_header),
+						 total_size);
 		/* Add the header size back. */
 		*total_size += sizeof(struct tpm_cmd_header);
 		tpmh->size = htobe32(*total_size);

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 {