Add comments to clarify mPubKeyStore buffer MemCopy. There is no memory overflow...

[mirror_edk2.git] / SecurityPkg / VariableAuthenticated / RuntimeDxe / AuthService.c

diff --git a/SecurityPkg/VariableAuthenticated/RuntimeDxe/AuthService.c b/SecurityPkg/VariableAuthenticated/RuntimeDxe/AuthService.c
index 49d7648f66557f11a1071791529b1fc5be201100..566c5e29a7866cc4248f01fc56df13fed3e08816 100644 (file)
--- a/SecurityPkg/VariableAuthenticated/RuntimeDxe/AuthService.c
+++ b/SecurityPkg/VariableAuthenticated/RuntimeDxe/AuthService.c
@@ -7,6 +7,10 @@
   This external input must be validated carefully to avoid security issue like\r
   buffer overflow, integer overflow.\r
   Variable attribute should also be checked to avoid authentication bypass.\r
+     The whole SMM authentication variable design relies on the integrity of flash part and SMM.\r
+  which is assumed to be protected by platform.  All variable code and metadata in flash/SMM Memory\r
+  may not be modified without authorization. If platform fails to protect these resources, \r
+  the authentication service provided in this driver will be broken, and the behavior is undefined.\r
 \r
   ProcessVarWithPk(), ProcessVarWithKek() and ProcessVariable() are the function to do\r
   variable authentication.\r
@@ -251,6 +255,10 @@ AutenticatedVariableServiceInitialize (
     DataSize  = DataSizeOfVariable (Variable.CurrPtr);\r
     Data      = GetVariableDataPtr (Variable.CurrPtr);\r
     ASSERT ((DataSize != 0) && (Data != NULL));\r
+    //\r
+    // "AuthVarKeyDatabase" is an internal variable. Its DataSize is always ensured not to exceed mPubKeyStore buffer size(See definition before) \r
+    //  Therefore, there is no memory overflow in underlying CopyMem.\r
+    //\r
     CopyMem (mPubKeyStore, (UINT8 *) Data, DataSize);\r
     mPubKeyNumber = (UINT32) (DataSize / EFI_CERT_TYPE_RSA2048_SIZE);\r
   }\r
@@ -564,6 +572,10 @@ AddPubKeyInStore (
       DataSize  = DataSizeOfVariable (Variable.CurrPtr);\r
       Data      = GetVariableDataPtr (Variable.CurrPtr);\r
       ASSERT ((DataSize != 0) && (Data != NULL));\r
+      //\r
+      // "AuthVarKeyDatabase" is an internal used variable. Its DataSize is always ensured not to exceed mPubKeyStore buffer size(See definition before) \r
+      //  Therefore, there is no memory overflow in underlying CopyMem.\r
+      //\r
       CopyMem (mPubKeyStore, (UINT8 *) Data, DataSize);\r
       mPubKeyNumber = (UINT32) (DataSize / EFI_CERT_TYPE_RSA2048_SIZE);\r
 \r