[WIP] x509util: parse inner RKP extension

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/cpuguy83/go-md2man/v2 v2.0.2 // indirect
 	github.com/form3tech-oss/jwt-go v3.2.5+incompatible // indirect
 	github.com/fullstorydev/grpcurl v1.8.6
+	github.com/fxamacker/cbor/v2 v2.6.0 // indirect
 	github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b
 	github.com/golang/mock v1.6.0
 	github.com/golang/protobuf v1.5.2

go.sum

@@ -253,6 +253,8 @@ github.com/fullstorydev/grpcurl v1.8.1/go.mod h1:3BWhvHZwNO7iLXaQlojdg5NA6SxUDeP
 github.com/fullstorydev/grpcurl v1.8.2/go.mod h1:YvWNT3xRp2KIRuvCphFodG0fKkMXwaxA9CJgKCcyzUQ=
 github.com/fullstorydev/grpcurl v1.8.6 h1:WylAwnPauJIofYSHqqMTC1eEfUIzqzevXyogBxnQquo=
 github.com/fullstorydev/grpcurl v1.8.6/go.mod h1:WhP7fRQdhxz2TkL97u+TCb505sxfH78W1usyoB3tepw=
+github.com/fxamacker/cbor/v2 v2.6.0 h1:sU6J2usfADwWlYDAFhZBQ6TnLFBHxgesMrQfQgk1tWA=
+github.com/fxamacker/cbor/v2 v2.6.0/go.mod h1:pxXPTn3joSm21Gbwsv0w9OSA2y1HFR9qXEeXQVeNoDQ=
 github.com/getsentry/raven-go v0.2.0 h1:no+xWJRb5ZI7eE8TWgIq1jLulQiIoLG0IfYxv5JYMGs=
 github.com/getsentry/raven-go v0.2.0/go.mod h1:KungGk8q33+aIAZUIVWZDr2OfAEBsO49PX4NzFV5kcQ=
 github.com/ghodss/yaml v1.0.0/go.mod h1:4dBDuWmgqj2HViK6kFavaiC9ZROes6MMH2rRYeMEF04=
@@ -761,6 +763,8 @@ github.com/urfave/cli v1.22.1/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60NtX
 github.com/urfave/cli v1.22.4/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60NtXRu0=
 github.com/urfave/cli v1.22.7 h1:aXiFAgRugfJ27UFDsGJ9DB2FvTC73hlVXFSqq5bo9eU=
 github.com/urfave/cli v1.22.7/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60NtXRu0=
+github.com/x448/float16 v0.8.4 h1:qLwI1I70+NjRFUR3zs1JPUCgaCXSh3SW62uAKT1mSBM=
+github.com/x448/float16 v0.8.4/go.mod h1:14CWIYCyZA/cWjXOioeEpHeN/83MdbZDRQHoFcYsOfg=
 github.com/xanzy/go-gitlab v0.31.0/go.mod h1:sPLojNBn68fMUWSxIJtdVVIP8uSBYqesTfDUseX11Ug=
 github.com/xanzy/ssh-agent v0.2.1/go.mod h1:mLlQY/MoOhWBj+gOGMQkOeiEvkx+8pJSI+0Bx9h2kr4=
 github.com/xi2/xz v0.0.0-20171230120015-48954b6210f8/go.mod h1:HUYIGzjTL3rfEspMxjDjgmT5uz5wzYJKVo23qUhYTos=

x509util/android.go

@@ -23,6 +23,7 @@ import (
 
 	"github.com/google/certificate-transparency-go/asn1"
 	"github.com/google/certificate-transparency-go/x509"
+	"github.com/fxamacker/cbor/v2"
 )
 
 // OIDExtensionAndroidAttestation is the OID value for an X.509 extension that holds
@@ -68,6 +69,12 @@ type AndroidVmComponent struct {
 	AuthorityHash   []byte
 }
 
+// RkpProvisioningInfo describes remotely provisioned key information
+type RkpProvisioningInfo struct {
+	CertsSigned30Days  int64                `cbor:"1,keyasint"`
+	Manufacturer       *string              `cbor:"2,keyasint,omitempty"`
+}
+
 func securityLevelToString(lvl asn1.Enumerated) string {
 	switch lvl {
 	case 0:
@@ -189,6 +196,22 @@ func VmInfoFromCert(cert *x509.Certificate) (*AndroidVmAttestationInfo, error) {
 	return nil, errors.New("no Android VM Attestation extension found")
 }
 
+// RkpInfoFromCert retrieves and parses an Android VM attestation information extension
+// from a certificate, if present.
+func RkpInfoFromCert(cert *x509.Certificate) (*RkpProvisioningInfo, error) {
+	for _, ext := range cert.Extensions {
+		if ext.Id.Equal(OIDExtensionAndroidRkpInfo) {
+			var rkpInfo RkpProvisioningInfo
+			err := cbor.Unmarshal(ext.Value, &rkpInfo)
+			if err != nil {
+				return nil, fmt.Errorf("failed to unmarshal RKP CBOR info: %v", err)
+			}
+			return &rkpInfo, nil
+		}
+	}
+	return nil, errors.New("no Android RKP Attestation extension found")
+}
+
 func showAndroidVmAttestation(result *bytes.Buffer, cert *x509.Certificate) {
 	count, critical := OIDInExtensions(OIDExtensionAndroidVmAttestation, cert.Extensions)
 	if count == 0 {
@@ -214,13 +237,20 @@ func showAndroidVmAttestation(result *bytes.Buffer, cert *x509.Certificate) {
 }
 
 func showAndroidRkpInfo(result *bytes.Buffer, cert *x509.Certificate) {
-	for _, ext := range cert.Extensions {
-		if ext.Id.Equal(OIDExtensionAndroidRkpInfo) {
-			result.WriteString(fmt.Sprintf("            Android RKP Information:"))
-			showCritical(result, ext.Critical)
-			appendHexData(result, ext.Value, 16, "                ")
-			result.WriteString("\n")
-		}
+	count, critical := OIDInExtensions(OIDExtensionAndroidRkpInfo, cert.Extensions)
+	if count == 0 {
+		return
+	}
+	result.WriteString(fmt.Sprintf("            Android RKP Information:"))
+	showCritical(result, critical)
+	rkpInfo, err := RkpInfoFromCert(cert)
+	if err != nil {
+		result.WriteString(fmt.Sprintf("              Failed to CBOR-decode RKP info: (%s)\n", err))
+		return
+	}
+	result.WriteString(fmt.Sprintf("              Certs Signed Last 30d: %d\n", rkpInfo.CertsSigned30Days))
+	if rkpInfo.Manufacturer != nil {
+		result.WriteString(fmt.Sprintf("              Manufacturer: %s\n", *rkpInfo.Manufacturer))
 	}
 }