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id_token.go
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/
id_token.go
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/*
Copyright 2018 Continusec Pty Ltd
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 geecert
import (
"crypto/rsa"
"encoding/base64"
"encoding/json"
"errors"
"io/ioutil"
"math/big"
"net/http"
"sync"
"time"
jwt "github.com/dgrijalva/jwt-go"
)
var (
ErrUnexpectedAlgorithm = errors.New("ErrUnexpectedAlgorithm")
ErrMissingKeyID = errors.New("ErrMissingKeyID")
ErrMissingCertificate = errors.New("ErrMissingCertificate")
ErrUnexpectedServerResponse = errors.New("ErrUnexpectedServerResponse")
ErrCertificateNotValid = errors.New("ErrCertificateNotValid")
)
// ensureConfig *must* be called
func (v *OIDCIDTokenValidator) keyFunc(t *jwt.Token) (interface{}, error) {
err := v.ensureHasConfig()
if err != nil {
return nil, err
}
// Ensure that RS256 is used. This might seem overkill to care,
// but since the JWT spec actually allows a None algorithm which
// we definitely don't want, so instead we whitelist what we will allow.
if t.Method.Alg() != "RS256" {
return nil, ErrUnexpectedAlgorithm
}
// Get Key ID
kid, ok := t.Header["kid"]
if !ok {
return nil, ErrMissingKeyID
}
kidS, ok := kid.(string)
if !ok {
return nil, ErrMissingKeyID
}
// Get key from cache
return v.kk.Get(kidS)
}
type keyCache struct {
JWKSURL string
Interval time.Duration
updateLock sync.Mutex
readLock sync.Mutex
keys map[string]*rsa.PublicKey
earliestUpdate time.Time
}
// Looks for the certificate with given ID. If not found, and not recently
// updated, then update the cache
func (cc *keyCache) Get(kid string) (*rsa.PublicKey, error) {
cc.readLock.Lock()
rv, ok := cc.keys[kid]
cc.readLock.Unlock()
if ok {
return rv, nil
}
err := cc.Update()
if err != nil {
return nil, err
}
cc.readLock.Lock()
rv, ok = cc.keys[kid]
cc.readLock.Unlock()
if ok {
return rv, nil
}
return nil, ErrMissingCertificate
}
type jwkResp struct {
Keys []struct {
KID string `json:"kid"`
KTY string `json:"kty"`
Use string `json:"use"`
N string `json:"n"`
E string `json:"e"`
} `json:"keys"`
}
// Updates the cache if past interval.
func (cc *keyCache) Update() error {
cc.updateLock.Lock()
defer cc.updateLock.Unlock()
// Leave early if we've updated recently
if time.Now().Before(cc.earliestUpdate) {
return nil
}
resp, err := http.Get(cc.JWKSURL)
if err != nil {
return err
}
// Always read body, even if not 200 as it can contain info about the err
defer resp.Body.Close()
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
return err
}
// Fail if not OK
if resp.StatusCode != http.StatusOK {
return ErrUnexpectedServerResponse
}
var keys jwkResp
err = json.Unmarshal(body, &keys)
if err != nil {
return ErrUnexpectedServerResponse
}
newKeys := make(map[string]*rsa.PublicKey)
for _, k := range keys.Keys {
if k.Use != "sig" {
continue
}
if k.KTY != "RSA" {
continue
}
eB, err := base64.RawURLEncoding.DecodeString(k.E)
if err != nil {
return ErrUnexpectedServerResponse
}
nB, err := base64.RawURLEncoding.DecodeString(k.N)
if err != nil {
return ErrUnexpectedServerResponse
}
newKeys[k.KID] = &rsa.PublicKey{
N: (&big.Int{}).SetBytes(nB),
E: int((&big.Int{}).SetBytes(eB).Int64()),
}
}
cc.readLock.Lock()
cc.keys = newKeys
cc.readLock.Unlock()
cc.earliestUpdate = time.Now().Add(cc.Interval)
return nil
}