rpc/crypto: fix validator field marshalling in getvalidators RPC server

Problem: wrong `PublicKey` field json marshalling of result.Validator

Solution: add marshaller to publickey (crypto)

pkg/crypto/keys/publickey.go

@@ -6,6 +6,7 @@ import (
 	"crypto/elliptic"
 	"crypto/x509"
 	"encoding/hex"
+	"encoding/json"
 	"fmt"
 	"math/big"
 
@@ -274,3 +275,28 @@ func (p *PublicKey) String() string {
 	by := hex.EncodeToString(p.Y.Bytes())
 	return fmt.Sprintf("%s%s", bx, by)
 }
+
+// MarshalJSON implements the json.Marshaler interface.
+func (p PublicKey) MarshalJSON() ([]byte, error) {
+	return json.Marshal(hex.EncodeToString(p.Bytes()))
+}
+
+// UnmarshalJSON implements json.Unmarshaler interface.
+func (p *PublicKey) UnmarshalJSON(data []byte) error {
+	l := len(data)
+	if l < 2 || data[0] != '"' || data[l-1] != '"' {
+		return errors.New("wrong format")
+	}
+
+	bytes := make([]byte, l-2)
+	_, err := hex.Decode(bytes, data[1:l-1])
+	if err != nil {
+		return err
+	}
+	err = p.DecodeBytes(bytes)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}

pkg/crypto/keys/publickey_test.go

@@ -2,6 +2,7 @@ package keys
 
 import (
 	"encoding/hex"
+	"encoding/json"
 	"math/rand"
 	"sort"
 	"testing"
@@ -143,3 +144,45 @@ func getPubKey(t *testing.T) *PublicKey {
 	require.NoError(t, err)
 	return pubKey
 }
+
+func TestMarshallJSON(t *testing.T) {
+	str := "03b209fd4f53a7170ea4444e0cb0a6bb6a53c2bd016926989cf85f9b0fba17a70c"
+	pubKey, err := NewPublicKeyFromString(str)
+	require.NoError(t, err)
+
+	bytes, err := json.Marshal(&pubKey)
+	require.NoError(t, err)
+	require.Equal(t, []byte(`"`+str+`"`), bytes)
+}
+
+func TestUnmarshallJSON(t *testing.T) {
+	str := "03b209fd4f53a7170ea4444e0cb0a6bb6a53c2bd016926989cf85f9b0fba17a70c"
+	expected, err := NewPublicKeyFromString(str)
+	require.NoError(t, err)
+
+	actual := &PublicKey{}
+	err = json.Unmarshal([]byte(`"`+str+`"`), actual)
+	require.NoError(t, err)
+	require.Equal(t, expected, actual)
+}
+
+func TestUnmarshallJSONBadCompresed(t *testing.T) {
+	str := `"02ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"`
+	actual := &PublicKey{}
+	err := json.Unmarshal([]byte(str), actual)
+	require.Error(t, err)
+}
+
+func TestUnmarshallJSONNotAHex(t *testing.T) {
+	str := `"04Tb17d1f2e12c4247f8bce6e563a440f277037d812deb33a0f4a13945d898c2964fe342e2fe1a7f9b8ee7eb4a7c0f9e162bce33576b315ececbb6406837bf51f5"`
+	actual := &PublicKey{}
+	err := json.Unmarshal([]byte(str), actual)
+	require.Error(t, err)
+}
+
+func TestUnmarshallJSONBadFormat(t *testing.T) {
+	str := "046b17d1f2e12c4247f8bce6e563a440f277037d812deb33a0f4a13945d898c2964fe342e2fe1a7f9b8ee7eb4a7c0f9e162bce33576b315ececbb6406837bf51f5"
+	actual := &PublicKey{}
+	err := json.Unmarshal([]byte(str), actual)
+	require.Error(t, err)
+}