[PATCH 1/1] SecurityPkg/AuthVariableLib: Check SHA-256 OID with ContentInfo present

["Jan Bobek" <jbobek@nvidia.com>]

Based on whether the DER-encoded ContentInfo structure is present in
authenticated SetVariable payload or not, the SHA-256 OID can be
located at different places.

UEFI specification explicitly states the driver shall support both
cases, but the old code assumed ContentInfo was not present and
incorrectly rejected authenticated variable updates when it were
present.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Signed-off-by: Jan Bobek <jbobek@nvidia.com>
---
 .../Library/AuthVariableLib/AuthService.c      | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/SecurityPkg/Library/AuthVariableLib/AuthService.c b/SecurityPkg/Library/AuthVariableLib/AuthService.c
index 054ee4d1d988..de8baccab410 100644
--- a/SecurityPkg/Library/AuthVariableLib/AuthService.c
+++ b/SecurityPkg/Library/AuthVariableLib/AuthService.c
@@ -1933,15 +1933,19 @@ VerifyTimeBasedPayload (
   //            .... }
   //    The DigestAlgorithmIdentifiers can be used to determine the hash algorithm
   //    in VARIABLE_AUTHENTICATION_2 descriptor.
-  //    This field has the fixed offset (+13) and be calculated based on two bytes of length encoding.
+  //    This field has the fixed offset (+13) or (+32) based on whether the DER-encoded
+  //    ContentInfo structure is present or not, and can be calculated based on two
+  //    bytes of length encoding.
   //
   if ((Attributes & EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS) != 0) {
-    if (SigDataSize >= (13 + sizeof (mSha256OidValue))) {
-      if (((*(SigData + 1) & TWO_BYTE_ENCODE) != TWO_BYTE_ENCODE) ||
-          (CompareMem (SigData + 13, &mSha256OidValue, sizeof (mSha256OidValue)) != 0))
-      {
-        return EFI_SECURITY_VIOLATION;
-      }
+    if (  (  (SigDataSize >= (13 + sizeof (mSha256OidValue)))
+          && (  ((*(SigData + 1) & TWO_BYTE_ENCODE) != TWO_BYTE_ENCODE)
+             || (CompareMem (SigData + 13, &mSha256OidValue, sizeof (mSha256OidValue)) != 0)))
+       && (  (SigDataSize >= (32 + sizeof (mSha256OidValue)))
+          && (  ((*(SigData + 20) & TWO_BYTE_ENCODE) != TWO_BYTE_ENCODE)
+             || (CompareMem (SigData + 32, &mSha256OidValue, sizeof (mSha256OidValue)) != 0))))
+    {
+      return EFI_SECURITY_VIOLATION;
     }
   }
 
-- 
2.30.2