add certificate validation

command_set.go

@@ -154,6 +154,22 @@ func (cs *CommandSet) Unpair(index uint8) error {
 	return cs.checkOK(resp, err)
 }
 
+func (cs *CommandSet) Identify() ([]byte, error) {
+	challenge := make([]byte, 32)
+	if _, err := rand.Read(challenge); err != nil {
+		return nil, err
+	}
+
+	cmd := NewCommandIdentify(challenge)
+	resp, err := cs.sc.Send(cmd)
+
+	if err = cs.checkOK(resp, err); err != nil {
+		return nil, err
+	}
+
+	return types.VerifyIdentity(challenge, resp.Data)
+}
+
 func (cs *CommandSet) OpenSecureChannel() error {
 	if cs.ApplicationInfo == nil {
 		return errors.New("cannot open secure channel without setting PairingInfo")

commands.go

@@ -16,6 +16,7 @@ const (
 	InsMutuallyAuthenticate = 0x11
 	InsPair                 = 0x12
 	InsUnpair               = 0x13
+	InsIdentify             = 0x14
 	InsGetStatus            = 0xF2
 	InsGenerateKey          = 0xD4
 	InsRemoveKey            = 0xD3
@@ -53,6 +54,7 @@ const (
 	P1ExportKeyDeriveAndMakeCurrent = 0x02
 	P2ExportKeyPrivateAndPublic     = 0x00
 	P2ExportKeyPublicOnly           = 0x01
+	P2ExportKeyExtendedPublic       = 0x02
 	P1LoadKeySeed                   = 0x03
 
 	SwNoAvailablePairingSlots = 0x6A84
@@ -98,6 +100,16 @@ func NewCommandUnpair(index uint8) *apdu.Command {
 	)
 }
 
+func NewCommandIdentify(challenge []byte) *apdu.Command {
+	return apdu.NewCommand(
+		globalplatform.ClaGp,
+		InsIdentify,
+		0,
+		0,
+		challenge,
+	)
+}
+
 func NewCommandOpenSecureChannel(pairingIndex uint8, pubKey []byte) *apdu.Command {
 	return apdu.NewCommand(
 		globalplatform.ClaGp,
@@ -247,13 +259,14 @@ func NewCommandDeriveKey(pathStr string) (*apdu.Command, error) {
 
 // Export a key
 //
-//		@param {p1}
+//	 @param {p1}
 //			0x00: current key - returns the key that is currently loaded and ready for signing. Does not use derivation path
 //			0x01: derive - returns derived key
 //			0x02: derive and make current - returns derived key and also sets it to the current key
 //	 @param {p2}
 //			0x00: return public and private key pair
 //			0x01: return only the public key
+//			0x02: return extended public key
 //	 @param {pathStr}
 //			Derivation path of format "m/x/x/x/x/x", e.g. "m/44'/0'/0'/0/0"
 func NewCommandExportKey(p1 uint8, p2 uint8, pathStr string) (*apdu.Command, error) {
@@ -334,7 +347,7 @@ func NewCommandSign(data []byte, p1 uint8, pathStr string) (*apdu.Command, error
 		globalplatform.ClaGp,
 		InsSign,
 		p1,
-		0,
+		1,
 		data,
 	), nil
 }

types/certificate.go

@@ -0,0 +1,82 @@
+package types
+
+import (
+	"crypto/sha256"
+	"errors"
+
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/status-im/keycard-go/apdu"
+)
+
+type Certificate struct {
+	identPub  []byte
+	signature *Signature
+}
+
+var (
+	TagCertificate = uint8(0x8A)
+)
+
+func ParseCertificate(data []byte) (*Certificate, error) {
+	if len(data) != 98 {
+		return nil, errors.New("certificate must be 98 byte long")
+	}
+
+	identPub := data[0:33]
+	sigData := data[33:97]
+	msg := sha256.Sum256(identPub)
+
+	sig, err := ParseRecoverableSignature(msg[:], sigData)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Certificate{
+		identPub:  identPub,
+		signature: sig,
+	}, nil
+}
+
+func VerifyIdentity(challenge []byte, tlvData []byte) ([]byte, error) {
+	template, err := apdu.FindTag(tlvData, apdu.Tag{TagSignatureTemplate})
+	if err != nil {
+		return nil, err
+	}
+
+	certData, err := apdu.FindTag(template, apdu.Tag{TagCertificate})
+	if err != nil {
+		return nil, err
+	}
+
+	cert, err := ParseCertificate(certData)
+	if err != nil {
+		return nil, err
+	}
+
+	r, s, err := DERSignatureToRS(template)
+	if err != nil {
+		return nil, err
+	}
+
+	sig := append(r, s...)
+
+	if !crypto.VerifySignature(cert.identPub, challenge, sig) {
+		return nil, errors.New("invalid signature")
+	}
+
+	return compressPublicKey(cert.signature.pubKey), nil
+}
+
+func compressPublicKey(pubKey []byte) []byte {
+	if len(pubKey) == 33 {
+		return pubKey
+	}
+
+	if (pubKey[63] & 1) == 1 {
+		pubKey[0] = 3
+	} else {
+		pubKey[0] = 2
+	}
+
+	return pubKey[0:33]
+}

types/signature.go

@@ -2,6 +2,7 @@ package types
 
 import (
 	"bytes"
+	"errors"
 
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/status-im/keycard-go/apdu"
@@ -9,6 +10,7 @@ import (
 
 var (
 	TagSignatureTemplate = uint8(0xA0)
+	TagRawSignature      = uint8(0x80)
 )
 
 type Signature struct {
@@ -19,42 +21,61 @@ type Signature struct {
 }
 
 func ParseSignature(message, resp []byte) (*Signature, error) {
-	pubKey, err := apdu.FindTag(resp, apdu.Tag{TagSignatureTemplate}, apdu.Tag{0x80})
+	// check for old template first because TagRawSignature matches the pubkey tag
+	template, err := apdu.FindTag(resp, apdu.Tag{TagSignatureTemplate})
+	if err == nil {
+		return parseLegacySignature(message, template)
+	}
+
+	sig, err := apdu.FindTag(resp, apdu.Tag{TagRawSignature})
+
 	if err != nil {
 		return nil, err
 	}
 
-	r, err := apdu.FindTagN(resp, 0, apdu.Tag{TagSignatureTemplate}, apdu.Tag{0x30}, apdu.Tag{0x02})
-	if err != nil {
-		return nil, err
+	return ParseRecoverableSignature(message, sig)
+}
+
+func ParseRecoverableSignature(message, sig []byte) (*Signature, error) {
+	if len(sig) != 65 {
+		return nil, errors.New("invalid signature")
 	}
 
-	if len(r) > 32 {
-		r = r[len(r)-32:]
-	}
-
-	s, err := apdu.FindTagN(resp, 1, apdu.Tag{TagSignatureTemplate}, apdu.Tag{0x30}, apdu.Tag{0x02})
-	if err != nil {
-		return nil, err
-	}
-
-	if len(s) > 32 {
-		s = s[len(s)-32:]
-	}
-
-	v, err := calculateV(message, pubKey, r, s)
+	pubKey, err := crypto.Ecrecover(message, sig)
 	if err != nil {
 		return nil, err
 	}
 
 	return &Signature{
 		pubKey: pubKey,
-		r:      r,
-		s:      s,
-		v:      v,
+		r:      sig[0:32],
+		s:      sig[32:64],
+		v:      sig[64],
 	}, nil
 }
 
+func DERSignatureToRS(tlv []byte) ([]byte, []byte, error) {
+	r, err := apdu.FindTagN(tlv, 0, apdu.Tag{0x30}, apdu.Tag{0x02})
+	if err != nil {
+		return nil, nil, err
+	}
+
+	if len(r) > 32 {
+		r = r[len(r)-32:]
+	}
+
+	s, err := apdu.FindTagN(tlv, 1, apdu.Tag{0x30}, apdu.Tag{0x02})
+	if err != nil {
+		return nil, nil, err
+	}
+
+	if len(s) > 32 {
+		s = s[len(s)-32:]
+	}
+
+	return r, s, nil
+}
+
 func (s *Signature) PubKey() []byte {
 	return s.pubKey
 }
@@ -71,9 +92,33 @@ func (s *Signature) V() byte {
 	return s.v
 }
 
+func parseLegacySignature(message, template []byte) (*Signature, error) {
+	pubKey, err := apdu.FindTag(template, apdu.Tag{0x80})
+	if err != nil {
+		return nil, err
+	}
+
+	r, s, err := DERSignatureToRS(template)
+	if err != nil {
+		return nil, err
+	}
+
+	v, err := calculateV(message, pubKey, r, s)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Signature{
+		pubKey: pubKey,
+		r:      r,
+		s:      s,
+		v:      v,
+	}, nil
+}
+
 func calculateV(message, pubKey, r, s []byte) (v byte, err error) {
 	rs := append(r, s...)
-	for i := 0; i < 2; i++ {
+	for i := 0; i < 4; i++ {
 		v = byte(i)
 		sig := append(rs, v)
 		rec, err := crypto.Ecrecover(message, sig)