Add support for flags in the firmware preamble.

The old (v2.0) parser is compatible with new (v2.1) structs.  That is,
this won't break existing firmware or vbutil_firmware.

A new (v2.1) parser parsing an old (v2.0) struct will return 0 for the
flags.

This will be used to support the RO-normal code path in a subsequent CL.

BUG=chromium-os:17304
TEST=added unit tests; make && make runtests

Change-Id: I73bcd8acd3330b0d7d143061b5ef838e6d79cf1a
Reviewed-on: http://gerrit.chromium.org/gerrit/4030
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
Tested-by: Randall Spangler <rspangler@chromium.org>

1 files changed, 23 insertions, 2 deletions

diff --git a/firmware/lib/vboot_common.c b/firmware/lib/vboot_common.c
index 81e2597b..5622d13b 100644
--- a/firmware/lib/vboot_common.c
+++ b/firmware/lib/vboot_common.c
@@ -297,8 +297,8 @@ int VerifyFirmwarePreamble(const VbFirmwarePreambleHeader* preamble,
   const VbSignature* sig = &preamble->preamble_signature;
 
   /* Sanity checks before attempting signature of data */
-  if(size < sizeof(VbFirmwarePreambleHeader)) {
-    VBDEBUG(("Not enough data for preamble header.\n"));
+  if(size < EXPECTED_VBFIRMWAREPREAMBLEHEADER2_0_SIZE) {
+    VBDEBUG(("Not enough data for preamble header 2.0.\n"));
     return VBOOT_PREAMBLE_INVALID;
   }
   if (preamble->header_version_major !=
@@ -348,11 +348,32 @@ int VerifyFirmwarePreamble(const VbFirmwarePreambleHeader* preamble,
     return VBOOT_PREAMBLE_INVALID;
   }
 
+  /* If the preamble header version is at least 2.1, verify we have
+   * space for the added fields from 2.1. */
+  if (preamble->header_version_minor >= 1) {
+    if(size < EXPECTED_VBFIRMWAREPREAMBLEHEADER2_1_SIZE) {
+      VBDEBUG(("Not enough data for preamble header 2.1.\n"));
+      return VBOOT_PREAMBLE_INVALID;
+    }
+  }
+
   /* Success */
   return VBOOT_SUCCESS;
 }
 
 
+uint32_t VbGetFirmwarePreambleFlags(const VbFirmwarePreambleHeader* preamble) {
+  if (preamble->header_version_minor < 1) {
+    /* Old structure; return default flags.  (Note that we don't need
+     * to check header_version_major; if that's not 2 then
+     * VerifyFirmwarePreamble() would have already failed. */
+    return 0;
+  }
+
+  return preamble->flags;
+}
+
+
 int VerifyKernelPreamble(const VbKernelPreambleHeader* preamble,
                          uint64_t size, const RSAPublicKey* key) {