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// Copyright 2020 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
//go:build linux && !gofuzz && cgo && tspi
// +build linux,!gofuzz,cgo,tspi
package attest
import (
"crypto"
"crypto/x509"
"encoding/binary"
"fmt"
"os"
"github.com/google/go-tspi/attestation"
"github.com/google/go-tspi/tspi"
"github.com/google/go-tspi/tspiconst"
)
func init() {
getTPM12Impl = getTPM12
}
func getTPM12() (*TPM, error) {
ctx, err := tspi.NewContext()
if err != nil {
return nil, err
}
if err = ctx.Connect(); err != nil {
return nil, err
}
return &TPM{tpm: &trousersTPM{ctx: ctx}}, nil
}
// trousersTPM interfaces with a TPM 1.2 device via tcsd.
type trousersTPM struct {
ctx *tspi.Context
}
func (*trousersTPM) isTPMBase() {}
func (t *trousersTPM) tpmVersion() TPMVersion {
return TPMVersion12
}
func (t *trousersTPM) close() error {
return t.ctx.Close()
}
func readTPM12VendorAttributes(context *tspi.Context) (TCGVendorID, string, error) {
// TPM 1.2 doesn't seem to store vendor data (other than unique ID)
vendor, err := context.GetCapability(tspiconst.TSS_TPMCAP_PROPERTY, 4, tspiconst.TSS_TPMCAP_PROP_MANUFACTURER)
if err != nil {
return TCGVendorID(0), "", fmt.Errorf("tspi::Context::GetCapability failed: %v", err)
}
if len(vendor) > 4 {
return TCGVendorID(0), "", fmt.Errorf("expecting at most 32-bit VendorID, got %d-bit ID instead", len(vendor)*8)
}
vendorID := TCGVendorID(binary.BigEndian.Uint32(vendor))
return vendorID, vendorID.String(), nil
}
// Info returns information about the TPM.
func (t *trousersTPM) info() (*TPMInfo, error) {
tInfo := TPMInfo{
Version: TPMVersion12,
Interface: TPMInterfaceDaemonManaged,
}
var err error
if tInfo.Manufacturer, tInfo.VendorInfo, err = readTPM12VendorAttributes(t.ctx); err != nil {
return nil, err
}
return &tInfo, nil
}
func readEKCertFromNVRAM12(ctx *tspi.Context) (*x509.Certificate, error) {
ekCert, err := attestation.GetEKCert(ctx)
if err != nil {
return nil, fmt.Errorf("reading EK cert: %v", err)
}
return ParseEKCertificate(ekCert)
}
func (t *trousersTPM) ekCertificates() ([]EK, error) {
cert, err := readEKCertFromNVRAM12(t.ctx)
if err != nil {
return nil, fmt.Errorf("readEKCertFromNVRAM failed: %v", err)
}
return []EK{
{Public: crypto.PublicKey(cert.PublicKey), Certificate: cert},
}, nil
}
func (t *trousersTPM) eks() ([]EK, error) {
return t.ekCertificates()
}
func (t *trousersTPM) newKey(*AK, *KeyConfig) (*Key, error) {
return nil, fmt.Errorf("not implemented")
}
func (t *trousersTPM) loadKey(opaqueBlob []byte) (*Key, error) {
return nil, fmt.Errorf("not implemented")
}
func (t *trousersTPM) loadKeyWithParent(opaqueBlob []byte, parent ParentKeyConfig) (*Key, error) {
return nil, fmt.Errorf("not implemented")
}
func (t *trousersTPM) newAK(opts *AKConfig) (*AK, error) {
pub, blob, err := attestation.CreateAIK(t.ctx)
if err != nil {
return nil, fmt.Errorf("CreateAIK failed: %v", err)
}
return &AK{ak: newTrousersKey12(blob, pub)}, nil
}
func (t *trousersTPM) loadAK(opaqueBlob []byte) (*AK, error) {
sKey, err := deserializeKey(opaqueBlob, TPMVersion12)
if err != nil {
return nil, fmt.Errorf("deserializeKey() failed: %v", err)
}
if sKey.Encoding != keyEncodingEncrypted {
return nil, fmt.Errorf("unsupported key encoding: %x", sKey.Encoding)
}
return &AK{ak: newTrousersKey12(sKey.Blob, sKey.Public)}, nil
}
func (t *trousersTPM) loadAKWithParent(opaqueBlob []byte, parent ParentKeyConfig) (*AK, error) {
return nil, fmt.Errorf("not implemented")
}
// allPCRs12 returns a map of all the PCR values on the TPM
func allPCRs12(ctx *tspi.Context) (map[uint32][]byte, error) {
tpm := ctx.GetTPM()
PCRlist, err := tpm.GetPCRValues()
if err != nil {
return nil, fmt.Errorf("failed to read PCRs: %v", err)
}
PCRs := make(map[uint32][]byte)
for i := 0; i < len(PCRlist); i++ {
PCRs[(uint32)(i)] = PCRlist[i]
}
return PCRs, nil
}
func (t *trousersTPM) pcrs(alg HashAlg) ([]PCR, error) {
if alg != HashSHA1 {
return nil, fmt.Errorf("non-SHA1 algorithm %v is not supported on TPM 1.2", alg)
}
PCRs, err := allPCRs12(t.ctx)
if err != nil {
return nil, fmt.Errorf("failed to read PCRs: %v", err)
}
out := make([]PCR, len(PCRs))
for index, digest := range PCRs {
out[int(index)] = PCR{
Index: int(index),
Digest: digest,
DigestAlg: alg.cryptoHash(),
}
}
return out, nil
}
func (t *trousersTPM) measurementLog() ([]byte, error) {
return os.ReadFile("/sys/kernel/security/tpm0/binary_bios_measurements")
}
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