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package key
import (
"errors"
"time"
"github.com/coreos/pkg/capnslog"
ptime "github.com/coreos/pkg/timeutil"
"github.com/jonboulle/clockwork"
)
var (
log = capnslog.NewPackageLogger("github.com/coreos/go-oidc", "key")
ErrorPrivateKeysExpired = errors.New("private keys have expired")
)
func NewPrivateKeyRotator(repo PrivateKeySetRepo, ttl time.Duration) *PrivateKeyRotator {
return &PrivateKeyRotator{
repo: repo,
ttl: ttl,
keep: 2,
generateKey: GeneratePrivateKey,
clock: clockwork.NewRealClock(),
}
}
type PrivateKeyRotator struct {
repo PrivateKeySetRepo
generateKey GeneratePrivateKeyFunc
clock clockwork.Clock
keep int
ttl time.Duration
}
func (r *PrivateKeyRotator) expiresAt() time.Time {
return r.clock.Now().UTC().Add(r.ttl)
}
func (r *PrivateKeyRotator) Healthy() error {
pks, err := r.privateKeySet()
if err != nil {
return err
}
if r.clock.Now().After(pks.ExpiresAt()) {
return ErrorPrivateKeysExpired
}
return nil
}
func (r *PrivateKeyRotator) privateKeySet() (*PrivateKeySet, error) {
ks, err := r.repo.Get()
if err != nil {
return nil, err
}
pks, ok := ks.(*PrivateKeySet)
if !ok {
return nil, errors.New("unable to cast to PrivateKeySet")
}
return pks, nil
}
func (r *PrivateKeyRotator) nextRotation() (time.Duration, error) {
pks, err := r.privateKeySet()
if err == ErrorNoKeys {
log.Infof("No keys in private key set; must rotate immediately")
return 0, nil
}
if err != nil {
return 0, err
}
now := r.clock.Now()
// Ideally, we want to rotate after half the TTL has elapsed.
idealRotationTime := pks.ExpiresAt().Add(-r.ttl / 2)
// If we are past the ideal rotation time, rotate immediatly.
return max(0, idealRotationTime.Sub(now)), nil
}
func max(a, b time.Duration) time.Duration {
if a > b {
return a
}
return b
}
func (r *PrivateKeyRotator) Run() chan struct{} {
attempt := func() {
k, err := r.generateKey()
if err != nil {
log.Errorf("Failed generating signing key: %v", err)
return
}
exp := r.expiresAt()
if err := rotatePrivateKeys(r.repo, k, r.keep, exp); err != nil {
log.Errorf("Failed key rotation: %v", err)
return
}
log.Infof("Rotated signing keys: id=%s expiresAt=%s", k.ID(), exp)
}
stop := make(chan struct{})
go func() {
for {
var nextRotation time.Duration
var sleep time.Duration
var err error
for {
if nextRotation, err = r.nextRotation(); err == nil {
break
}
sleep = ptime.ExpBackoff(sleep, time.Minute)
log.Errorf("error getting nextRotation, retrying in %v: %v", sleep, err)
time.Sleep(sleep)
}
log.Infof("will rotate keys in %v", nextRotation)
select {
case <-r.clock.After(nextRotation):
attempt()
case <-stop:
return
}
}
}()
return stop
}
func rotatePrivateKeys(repo PrivateKeySetRepo, k *PrivateKey, keep int, exp time.Time) error {
ks, err := repo.Get()
if err != nil && err != ErrorNoKeys {
return err
}
var keys []*PrivateKey
if ks != nil {
pks, ok := ks.(*PrivateKeySet)
if !ok {
return errors.New("unable to cast to PrivateKeySet")
}
keys = pks.Keys()
}
keys = append([]*PrivateKey{k}, keys...)
if l := len(keys); l > keep {
keys = keys[0:keep]
}
nks := PrivateKeySet{
keys: keys,
ActiveKeyID: k.ID(),
expiresAt: exp,
}
return repo.Set(KeySet(&nks))
}
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