From 8e46c60ee4395f5b69aef3f088ac587b1cb202b5 Mon Sep 17 00:00:00 2001
From: Krishap-s <krishap.s.sreenivasan@gmail.com>
Date: Thu, 14 Mar 2024 10:15:58 +0530
Subject: [PATCH] Add support for AMD EK certificates

---
 attest/tpm.go           | 19 +++++++++++++++++++
 attest/tpm_test.go      | 29 +++++++++++++++++++++++++++--
 attest/tpm_windows.go   |  3 +++
 attest/wrapped_tpm20.go |  3 +++
 4 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/attest/tpm.go b/attest/tpm.go
index 31217728..51f06542 100644
--- a/attest/tpm.go
+++ b/attest/tpm.go
@@ -268,6 +268,25 @@ func intelEKURL(ekPub *rsa.PublicKey) string {
 	return intelEKCertServiceURL + url.QueryEscape(base64.URLEncoding.EncodeToString(pubHash.Sum(nil)))
 }
 
+const (
+	manufacturerAMD     = "AMD"
+	amdEKCertServiceURL = "https://ftpm.amd.com/pki/aia/"
+)
+
+func amdEKURL(ekPub *rsa.PublicKey) string {
+	pubHash := sha256.New()
+	pubHash.Write([]byte{0x00, 0x00, 0x22, 0x22})
+	exp := ekPub.E
+	if exp == 0 {
+		exp = int(0x00010001)
+	}
+	expBytes := make([]byte, 4)
+	binary.BigEndian.PutUint32(expBytes, uint32(ekPub.E))
+	pubHash.Write(expBytes)
+	pubHash.Write(ekPub.N.Bytes())
+	return amdEKCertServiceURL + url.QueryEscape(fmt.Sprintf("%X", pubHash.Sum(nil)[0:16]))
+}
+
 func readEKCertFromNVRAM20(tpm io.ReadWriter, nvramCertIndex tpmutil.Handle) (*x509.Certificate, error) {
 	// By passing nvramCertIndex as our auth handle we're using the NV index
 	// itself as the auth hierarchy, which is the same approach
diff --git a/attest/tpm_test.go b/attest/tpm_test.go
index 1a385631..3c85b9e2 100644
--- a/attest/tpm_test.go
+++ b/attest/tpm_test.go
@@ -16,7 +16,7 @@ import (
 //
 // This is the public key from the EK cert that's used for testing tpm2-tools:
 // https://github.com/tpm2-software/tpm2-tools/blob/master/test/integration/tests/getekcertificate.sh
-var testRSAKey = mustParseRSAKey(`-----BEGIN PUBLIC KEY-----
+var testIntelRSAKey = mustParseRSAKey(`-----BEGIN PUBLIC KEY-----
 MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAwyDi8kSoYBqs8+AdJsZl
 JJk1Vi3h2hl+nn8HbEaWE8+2U+mOwsOG/B0TPyyMbMM4tzLwsgi9g4qHej5bvD4d
 QIToNcfIkGocBbTS0w/b68HbrZUPprFlvUtqhkYDFGFkwMT1nUiQEe8fko3upukA
@@ -26,6 +26,23 @@ pE3GeajzKTjdgZfina6Dn1tMoPXeJ8lSLCPFThws5XhZUlEYvURwsYGA7veK5CZ7
 zQIDAQAB
 -----END PUBLIC KEY-----`)
 
+// Created by downloading the binary PEM data from 
+// https://ftpm.amd.com/pki/aia/D027B3CE6A9B6B56846D2B9935884A88
+// extracting its public key, and formatting it to PEM using
+//
+//	openssl x509 -in ekcert.crt -pubkey
+//
+// This public key is from the EK cert from a real AMD fTPM platform
+var testAMDRSAKey = mustParseRSAKey(`-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAo8ID3MRLZQWgq2WIK1qT
+e2HQxzZgiDWn6Tzw6uQOoXI1iyO9pxIailRxll2NeK1lRVP/dEKCV+mGwv75T+y2
+MmzpFhUY/O5RtEG8TiocDw6WkHRAJ9A9h1OMP+vD3mPClNoA9/ssB36/0ScmVtYR
+0gRkL+cZkAT6qro7xz4eRKLt8KfX6OG/Y9kCfJsKDCtYbc4OavHSf11VgbBLtxm7
+jSVE+pnO+x/om6qwACjZbU4qrq4PUbAxD1S9dJ2cZzKaYSsCA8wMIho0umYa3jGv
+eptunXDcE993BlsUGjLNbXC4aWVEtgo9yu98gKqhYGFEx7Mtk5NYOvWoNvcUBe2L
+2QIDAQAB
+-----END PUBLIC KEY-----`)
+
 func mustParseRSAKey(data string) *rsa.PublicKey {
 	pub, err := parseRSAKey(data)
 	if err != nil {
@@ -51,8 +68,16 @@ func parseRSAKey(data string) (*rsa.PublicKey, error) {
 
 func TestIntelEKURL(t *testing.T) {
 	want := "https://ekop.intel.com/ekcertservice/WVEG2rRwkQ7m3RpXlUphgo6Y2HLxl18h6ZZkkOAdnBE%3D"
-	got := intelEKURL(testRSAKey)
+	got := intelEKURL(testIntelRSAKey)
 	if got != want {
 		t.Fatalf("intelEKURL(), got=%q, want=%q", got, want)
 	}
 }
+
+func TestAMDEKURL(t *testing.T) {
+	want:= "https://ftpm.amd.com/pki/aia/D027B3CE6A9B6B56846D2B9935884A88"
+	got := amdEKURL(testAMDRSAKey)
+	if got != want {
+		t.Fatalf("amdEKURL(), got=%q, want=%q",got,want)
+	}
+}
diff --git a/attest/tpm_windows.go b/attest/tpm_windows.go
index ccaf1eeb..a3a45793 100644
--- a/attest/tpm_windows.go
+++ b/attest/tpm_windows.go
@@ -190,6 +190,9 @@ func (t *windowsTPM) eks() ([]EK, error) {
 	if i.Manufacturer.String() == manufacturerIntel {
 		ek.CertificateURL = intelEKURL(pub)
 	}
+	if i.Manufacturer.String() == manufacturerAMD {
+		ek.CertificateURL = amdEKURL(pub)
+	}
 	return []EK{ek}, nil
 }
 
diff --git a/attest/wrapped_tpm20.go b/attest/wrapped_tpm20.go
index 1468c1bd..5495d24c 100644
--- a/attest/wrapped_tpm20.go
+++ b/attest/wrapped_tpm20.go
@@ -225,6 +225,9 @@ func (t *wrappedTPM20) eks() ([]EK, error) {
 	if i.Manufacturer.String() == manufacturerIntel {
 		certificateURL = intelEKURL(ekPub)
 	}
+	if i.Manufacturer.String() == manufacturerAMD {
+		certificateURL = amdEKURL(ekPub)
+	}
 	return []EK{
 		{
 			Public:         ekPub,