Add a --subkey switch to kernel signing utility.

src/platform/vboot_reference/vkernel/kernel_image.c

 /* Copyright (c) 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.
  *
  * Functions for generating and manipulating a verified boot kernel image.
  * (Userland portion)
  */
 #include "kernel_image.h"
 
 #include <fcntl.h>
@@ skipping 304 matching lines @@
   if (st.overrun || st.remaining_len != 0) {  /* Underrun or Overrun. */
     debug("GetKernelBlob() failed.\n");
     Free(kernel_blob);
     return NULL;
   }
   return kernel_blob;
 }
 
 int WriteKernelImage(const char* output_file,
                      const KernelImage* image,
-                     int is_only_vblock) {
+                     int is_only_vblock,
+                     int is_subkey_out) {
   int fd;
   int success = 1;
-  uint8_t* kernel_blob;
+  uint8_t* kernel_blob = NULL;
+  uint8_t* subkey_out_buf = NULL;
+  uint8_t* subkey_header = NULL;
   uint64_t blob_len;
 
   if (!image)
     return 0;
   if (-1 == (fd = creat(output_file, S_IRWXU))) {
     debug("Couldn't open file for writing kernel image: %s\n",
             output_file);
     return 0;
   }
+  if (is_subkey_out) {
+    blob_len = GetKernelHeaderLen(image) +
+        siglen_map[image->firmware_sign_algorithm];
+    subkey_out_buf = (uint8_t*) Malloc(blob_len);
+    subkey_header = GetKernelHeaderBlob(image);
+    Memcpy(subkey_out_buf, subkey_header, GetKernelHeaderLen(image));
+    Memcpy(subkey_out_buf + GetKernelHeaderLen(image),
+           image->kernel_key_signature,
+           siglen_map[image->firmware_sign_algorithm]);
+    if (blob_len != write(fd, subkey_out_buf, blob_len)) {
+      debug("Couldn't write Kernel Subkey header to file: %s\n",
+            output_file);
+      success = 0;
+    }
+    Free(subkey_header);
+    Free(subkey_out_buf);
+    close(fd);
+    return success;
+  }
+
   kernel_blob = GetKernelBlob(image, &blob_len);
   if (!kernel_blob) {
     debug("Couldn't create kernel blob from KernelImage.\n");
     return 0;
   }
   if (!is_only_vblock) {
     if (blob_len != write(fd, kernel_blob, blob_len)) {
       debug("Couldn't write Kernel Image to file: %s\n",
             output_file);
       success = 0;
@@ skipping 375 matching lines @@
   // Clean up and return the blob.
 done3:
   Free(bootloader_buf);
 done2:
   Free(config_buf);
 done1:
   Free(kernel_buf);
 done0:
   return blob;
 }