From 2f809d0330c2dccb9143ba0be6bbb84b66a202ab Mon Sep 17 00:00:00 2001
From: Deepika Rajani <35041528+deepikarajani24@users.noreply.github.com>
Date: Wed, 2 Dec 2020 14:09:22 -0500
Subject: [PATCH] Deepikarajani24 patch 1 (#193)

* tbs.dll to not initialize on start up
so that it's not initialized when tpm support is not required

Changed author to my google.com user

* initialize tbs.dll and proc Tbsi_GetDeviceInfo during probeSystemTPMs

initialization is done in probeSystemTPMs as it's called before openTPM which requires support of the dll
changed author to my google.com user

* tbs.dll to load once

Changed the author to my google.com email

* Tbsi_GetDeviceInfo check to happen once
changed the author of the commit
---
 attest/pcp_windows.go | 4 ++--
 attest/tpm_windows.go | 6 ++++++
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/attest/pcp_windows.go b/attest/pcp_windows.go
index 99bcb6b..bb85ab1 100644
--- a/attest/pcp_windows.go
+++ b/attest/pcp_windows.go
@@ -58,8 +58,8 @@ var (
 	crypt32CertEnumCertificatesInStore = crypt32.MustFindProc("CertEnumCertificatesInStore")
 	crypt32CertCloseStore              = crypt32.MustFindProc("CertCloseStore")
 
-	tbs              = windows.MustLoadDLL("Tbs.dll")
-	tbsGetDeviceInfo = tbs.MustFindProc("Tbsi_GetDeviceInfo")
+	tbs              *windows.DLL
+	tbsGetDeviceInfo *windows.Proc
 )
 
 // Error codes.
diff --git a/attest/tpm_windows.go b/attest/tpm_windows.go
index 31cbab2..d6f28c6 100644
--- a/attest/tpm_windows.go
+++ b/attest/tpm_windows.go
@@ -42,6 +42,12 @@ type windowsTPM struct {
 func (*windowsTPM) isTPMBase() {}
 
 func probeSystemTPMs() ([]probedTPM, error) {
+	// Initialize Tbs.dll here so that it's linked only when TPM support is required.
+	if tbs == nil {
+		tbs = windows.MustLoadDLL("Tbs.dll")
+		tbsGetDeviceInfo = tbs.MustFindProc("Tbsi_GetDeviceInfo")
+	}
+	
 	// Windows systems appear to only support a single abstracted TPM.
 	// If we fail to initialize the Platform Crypto Provider, we assume
 	// a TPM is not present.