Add a kernel subkey signing algorithm key and algorithm fields to firmware preamble.

src/platform/vboot_reference/tests/test_common.c

Index: src/platform/vboot_reference/tests/test_common.c
diff --git a/src/platform/vboot_reference/tests/test_common.c b/src/platform/vboot_reference/tests/test_common.c
index 5c39413fbd491aa37fa5728d6f2fb7306c61dd90..8270c3adca697789bd83b9411a376f70873c14c6 100644
--- a/src/platform/vboot_reference/tests/test_common.c
+++ b/src/platform/vboot_reference/tests/test_common.c
@@ -72,6 +72,12 @@ FirmwareImage* GenerateTestFirmwareImage(int algorithm,
   /* Populate firmware and preamble with dummy data. */
   image->firmware_version = firmware_version;
   image->firmware_len = firmware_len;
+  /* Make the kernel subkey the same as the firmware signing key. */
+  image->kernel_subkey_sign_algorithm = algorithm;
+  image->kernel_subkey_sign_key = (uint8_t*) Malloc(
+      RSAProcessedKeySize(image->kernel_subkey_sign_algorithm));
+  Memcpy(image->kernel_subkey_sign_key, firmware_sign_key,
+         RSAProcessedKeySize(image->kernel_subkey_sign_algorithm));
   image->preamble_signature = image->firmware_signature = NULL;
   Memset(image->preamble, 'P', FIRMWARE_PREAMBLE_SIZE);
   image->firmware_data = Malloc(image->firmware_len);