forked from minio/minio
/
jwks.go
137 lines (118 loc) · 3.01 KB
/
jwks.go
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/*
* Minio Cloud Storage, (C) 2018 Minio, 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.
*/
package validator
import (
"crypto"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rsa"
"encoding/base64"
"encoding/binary"
"errors"
"fmt"
"math/big"
"strings"
)
// JWKS - https://tools.ietf.org/html/rfc7517
type JWKS struct {
Keys []*JWKS `json:"keys,omitempty"`
Kty string `json:"kty"`
Use string `json:"use,omitempty"`
Kid string `json:"kid,omitempty"`
Alg string `json:"alg,omitempty"`
Crv string `json:"crv,omitempty"`
X string `json:"x,omitempty"`
Y string `json:"y,omitempty"`
D string `json:"d,omitempty"`
N string `json:"n,omitempty"`
E string `json:"e,omitempty"`
K string `json:"k,omitempty"`
}
func safeDecode(str string) ([]byte, error) {
lenMod4 := len(str) % 4
if lenMod4 > 0 {
str = str + strings.Repeat("=", 4-lenMod4)
}
return base64.URLEncoding.DecodeString(str)
}
var (
errMalformedJWKRSAKey = errors.New("malformed JWK RSA key")
errMalformedJWKECKey = errors.New("malformed JWK EC key")
)
// DecodePublicKey - decodes JSON Web Key (JWK) as public key
func (key *JWKS) DecodePublicKey() (crypto.PublicKey, error) {
switch key.Kty {
case "RSA":
if key.N == "" || key.E == "" {
return nil, errMalformedJWKRSAKey
}
// decode exponent
data, err := safeDecode(key.E)
if err != nil {
return nil, errMalformedJWKRSAKey
}
if len(data) < 4 {
ndata := make([]byte, 4)
copy(ndata[4-len(data):], data)
data = ndata
}
pubKey := &rsa.PublicKey{
N: &big.Int{},
E: int(binary.BigEndian.Uint32(data[:])),
}
data, err = safeDecode(key.N)
if err != nil {
return nil, errMalformedJWKRSAKey
}
pubKey.N.SetBytes(data)
return pubKey, nil
case "EC":
if key.Crv == "" || key.X == "" || key.Y == "" {
return nil, errMalformedJWKECKey
}
var curve elliptic.Curve
switch key.Crv {
case "P-224":
curve = elliptic.P224()
case "P-256":
curve = elliptic.P256()
case "P-384":
curve = elliptic.P384()
case "P-521":
curve = elliptic.P521()
default:
return nil, fmt.Errorf("Unknown curve type: %s", key.Crv)
}
pubKey := &ecdsa.PublicKey{
Curve: curve,
X: &big.Int{},
Y: &big.Int{},
}
data, err := safeDecode(key.X)
if err != nil {
return nil, errMalformedJWKECKey
}
pubKey.X.SetBytes(data)
data, err = safeDecode(key.Y)
if err != nil {
return nil, errMalformedJWKECKey
}
pubKey.Y.SetBytes(data)
return pubKey, nil
default:
return nil, fmt.Errorf("Unknown JWK key type %s", key.Kty)
}
}