SecurityPkg/DxeImageVerificationLib: reject CertStack.CertNumber==0 per DBX (CVE...

In case the signers' certificate stack, retrieved from the PE/COFF image's
Authenticode blob, has zero elements (=there are zero signer certificates),
then we should consider the image forbidden by DBX, not accepted by DBX.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Chao Zhang <chao.b.zhang@intel.com>
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>

diff --git a/SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c b/SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c
index 74dbffa1227f657db50004feba97e61d32c1ac5b..5dcd6efed534668acf0c402c35afeee095ae3147 100644 (file)
--- a/SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c
+++ b/SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c
@@ -1326,7 +1326,7 @@ IsForbiddenByDbx (
   //       UINT8  Certn[];\r
   //\r
   Pkcs7GetSigners (AuthData, AuthDataSize, &CertBuffer, &BufferLength, &TrustedCert, &TrustedCertLength);\r
-  if ((BufferLength == 0) || (CertBuffer == NULL)) {\r
+  if ((BufferLength == 0) || (CertBuffer == NULL) || (*CertBuffer) == 0) {\r
     IsForbidden = TRUE;\r
     goto Done;\r
   }\r