From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=209.132.183.28; helo=mx1.redhat.com; envelope-from=lersek@redhat.com; receiver=edk2-devel@lists.01.org Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id CB0B221F3C1B9 for ; Tue, 10 Oct 2017 06:21:33 -0700 (PDT) Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 11A60E0759; Tue, 10 Oct 2017 13:25:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 11A60E0759 Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=lersek@redhat.com Received: from lacos-laptop-7.usersys.redhat.com (ovpn-120-87.rdu2.redhat.com [10.10.120.87]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1547B6C429; Tue, 10 Oct 2017 13:24:58 +0000 (UTC) From: Laszlo Ersek To: edk2-devel-01 Cc: Eric Dong , Jiewen Yao , Star Zeng Date: Tue, 10 Oct 2017 15:24:43 +0200 Message-Id: <20171010132443.11383-1-lersek@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Tue, 10 Oct 2017 13:25:01 +0000 (UTC) Subject: [PATCH] MdeModulePkg/Variable/RuntimeDxe: delete & lock MOR in the absence of SMM X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 10 Oct 2017 13:21:34 -0000 VariableRuntimeDxe deletes and locks the MorLock variable in MorLockInit(), with the argument that any protection provided by MorLock can be circumvented if MorLock can be overwritten by unprivileged code (i.e., outside of SMM). Extend the argument and the logic to the MOR variable, which is supposed to be protected by MorLock. This change was suggested by Star; it is inspired by earlier VariableSmm commit fda8f631edbb ("MdeModulePkg/Variable/RuntimeDxe: delete and lock OS-created MOR variable", 2017-10-03). Cc: Eric Dong Cc: Jiewen Yao Cc: Star Zeng Suggested-by: Star Zeng Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Laszlo Ersek --- Notes: Repo: https://github.com/lersek/edk2.git Branch: del_and_lock_mor_without_smm MdeModulePkg/Universal/Variable/RuntimeDxe/TcgMorLockDxe.c | 24 ++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/MdeModulePkg/Universal/Variable/RuntimeDxe/TcgMorLockDxe.c b/MdeModulePkg/Universal/Variable/RuntimeDxe/TcgMorLockDxe.c index 7142e2da2073..1610c7aa0706 100644 --- a/MdeModulePkg/Universal/Variable/RuntimeDxe/TcgMorLockDxe.c +++ b/MdeModulePkg/Universal/Variable/RuntimeDxe/TcgMorLockDxe.c @@ -69,29 +69,53 @@ EFI_STATUS MorLockInit ( VOID ) { // // Always clear variable to report unsupported to OS. // The reason is that the DXE version is not proper to provide *protection*. // BIOS should use SMM version variable driver to provide such capability. // VariableServiceSetVariable ( MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME, &gEfiMemoryOverwriteRequestControlLockGuid, EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS, 0, NULL ); // // Need set this variable to be read-only to prevent other module set it. // VariableLockRequestToLock (&mVariableLock, MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME, &gEfiMemoryOverwriteRequestControlLockGuid); + + // + // The MOR variable can effectively improve platform security only when the + // MorLock variable protects the MOR variable. In turn MorLock cannot be made + // secure without SMM support in the platform firmware (see above). + // + // Thus, delete the MOR variable, should it exist for any reason (some OSes + // are known to create MOR unintentionally, in an attempt to set it), then + // also lock the MOR variable, in order to prevent other modules from + // creating it. + // + VariableServiceSetVariable ( + MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME, + &gEfiMemoryOverwriteControlDataGuid, + 0, // Attributes + 0, // DataSize + NULL // Data + ); + VariableLockRequestToLock ( + &mVariableLock, + MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME, + &gEfiMemoryOverwriteControlDataGuid + ); + return EFI_SUCCESS; } /** Delayed initialization for MOR Control Lock at EndOfDxe. This function performs any operations queued by MorLockInit(). **/ -- 2.14.1.3.gb7cf6e02401b