package provisioner import ( "encoding/json" "math/rand" "net/http" "regexp" "strconv" "sync" "time" "github.com/pkg/errors" "github.com/smallstep/cli/jose" ) const ( defaultCacheAge = 12 * time.Hour defaultCacheJitter = 1 * time.Hour ) var maxAgeRegex = regexp.MustCompile("max-age=([0-9]*)") type keyStore struct { sync.RWMutex uri string keys jose.JSONWebKeySet timer *time.Timer expiry time.Time } func newKeyStore(uri string) (*keyStore, error) { keys, age, err := getKeysFromJWKsURI(uri) if err != nil { return nil, err } ks := &keyStore{ uri: uri, keys: keys, expiry: getExpirationTime(age), } ks.timer = time.AfterFunc(age, ks.reload) return ks, nil } func (ks *keyStore) Close() { ks.timer.Stop() } func (ks *keyStore) Get(kid string) (keys []jose.JSONWebKey) { ks.RLock() // Force reload if expiration has passed if time.Now().After(ks.expiry) { ks.RUnlock() ks.reload() ks.RLock() } keys = ks.keys.Key(kid) ks.RUnlock() return } func (ks *keyStore) reload() { var next time.Duration keys, age, err := getKeysFromJWKsURI(ks.uri) if err != nil { next = ks.nextReloadDuration(defaultCacheJitter / 2) } else { ks.Lock() ks.keys = keys ks.expiry = time.Now().Round(time.Second).Add(age - 1*time.Minute).UTC() ks.Unlock() next = ks.nextReloadDuration(age) } ks.Lock() ks.timer.Reset(next) ks.Unlock() } func (ks *keyStore) nextReloadDuration(age time.Duration) time.Duration { n := rand.Int63n(int64(defaultCacheJitter)) age -= time.Duration(n) if age < 0 { age = 0 } return age } func getKeysFromJWKsURI(uri string) (jose.JSONWebKeySet, time.Duration, error) { var keys jose.JSONWebKeySet resp, err := http.Get(uri) if err != nil { return keys, 0, errors.Wrapf(err, "failed to connect to %s", uri) } defer resp.Body.Close() if err := json.NewDecoder(resp.Body).Decode(&keys); err != nil { return keys, 0, errors.Wrapf(err, "error reading %s", uri) } return keys, getCacheAge(resp.Header.Get("cache-control")), nil } func getCacheAge(cacheControl string) time.Duration { age := defaultCacheAge if len(cacheControl) > 0 { match := maxAgeRegex.FindAllStringSubmatch(cacheControl, -1) if len(match) > 0 { if len(match[0]) == 2 { maxAge := match[0][1] maxAgeInt, err := strconv.ParseInt(maxAge, 10, 64) if err != nil { return defaultCacheAge } age = time.Duration(maxAgeInt) * time.Second } } } return age } func getExpirationTime(age time.Duration) time.Time { return time.Now().Round(time.Second).Add(age - 1*time.Minute).UTC() }