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package keyfile
import (
"crypto"
"fmt"
"io"
"github.com/google/go-tpm/tpm2"
"github.com/google/go-tpm/tpm2/transport"
)
// TPMKeySigner implements the crypto.Signer interface for TPMKey
// It allows passing callbacks for TPM, ownerAuth and user auth.
type TPMKeySigner struct {
key *TPMKey
ownerAuth func() ([]byte, error)
tpm func() transport.TPMCloser
auth func(*TPMKey) ([]byte, error)
}
var _ crypto.Signer = &TPMKeySigner{}
// Returns the crypto.PublicKey
func (t *TPMKeySigner) Public() crypto.PublicKey {
pk, err := t.key.PublicKey()
// This shouldn't happen!
if err != nil {
panic(fmt.Errorf("failed producing public: %v", err))
}
return pk
}
// Sign implementation
func (t *TPMKeySigner) Sign(_ io.Reader, digest []byte, opts crypto.SignerOpts) ([]byte, error) {
var digestalg tpm2.TPMAlgID
auth := []byte("")
if t.key.HasAuth() {
p, err := t.auth(t.key)
if err != nil {
return nil, err
}
auth = p
}
switch opts.HashFunc() {
case crypto.SHA256:
digestalg = tpm2.TPMAlgSHA256
case crypto.SHA384:
digestalg = tpm2.TPMAlgSHA384
case crypto.SHA512:
digestalg = tpm2.TPMAlgSHA512
default:
return nil, fmt.Errorf("%s is not a supported hashing algorithm", opts.HashFunc())
}
ownerauth, err := t.ownerAuth()
if err != nil {
return nil, err
}
sess := NewTPMSession(t.tpm())
sess.SetTPM(t.tpm())
return SignASN1(sess, t.key, ownerauth, auth, digest, digestalg)
}
func NewTPMKeySigner(k *TPMKey, ownerAuth func() ([]byte, error), tpm func() transport.TPMCloser, auth func(*TPMKey) ([]byte, error)) *TPMKeySigner {
return &TPMKeySigner{
key: k,
ownerAuth: ownerAuth,
tpm: tpm,
auth: auth,
}
}
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