forked from TrueCloudLab/certificates
135 lines
2.7 KiB
Go
135 lines
2.7 KiB
Go
package provisioner
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import (
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"encoding/json"
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"math/rand"
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"net/http"
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"regexp"
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"strconv"
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"sync"
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"time"
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"github.com/pkg/errors"
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"github.com/smallstep/cli/jose"
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)
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const (
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defaultCacheAge = 12 * time.Hour
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defaultCacheJitter = 1 * time.Hour
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)
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var maxAgeRegex = regexp.MustCompile("max-age=([0-9]*)")
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type keyStore struct {
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sync.RWMutex
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uri string
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keySet jose.JSONWebKeySet
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timer *time.Timer
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expiry time.Time
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jitter time.Duration
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}
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func newKeyStore(uri string) (*keyStore, error) {
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keys, age, err := getKeysFromJWKsURI(uri)
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if err != nil {
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return nil, err
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}
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ks := &keyStore{
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uri: uri,
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keySet: keys,
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expiry: getExpirationTime(age),
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jitter: getCacheJitter(age),
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}
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next := ks.nextReloadDuration(age)
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ks.timer = time.AfterFunc(next, ks.reload)
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return ks, nil
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}
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func (ks *keyStore) Close() {
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ks.timer.Stop()
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}
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func (ks *keyStore) Get(kid string) (keys []jose.JSONWebKey) {
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ks.RLock()
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// Force reload if expiration has passed
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if time.Now().After(ks.expiry) {
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ks.RUnlock()
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ks.reload()
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ks.RLock()
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}
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keys = ks.keySet.Key(kid)
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ks.RUnlock()
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return
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}
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func (ks *keyStore) reload() {
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var next time.Duration
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keys, age, err := getKeysFromJWKsURI(ks.uri)
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if err != nil {
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next = ks.nextReloadDuration(ks.jitter / 2)
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} else {
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ks.Lock()
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ks.keySet = keys
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ks.expiry = getExpirationTime(age)
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ks.jitter = getCacheJitter(age)
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next = ks.nextReloadDuration(age)
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ks.Unlock()
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}
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ks.Lock()
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ks.timer.Reset(next)
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ks.Unlock()
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}
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func (ks *keyStore) nextReloadDuration(age time.Duration) time.Duration {
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n := rand.Int63n(int64(ks.jitter))
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age -= time.Duration(n)
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if age < 0 {
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age = 0
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}
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return age
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}
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func getKeysFromJWKsURI(uri string) (jose.JSONWebKeySet, time.Duration, error) {
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var keys jose.JSONWebKeySet
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resp, err := http.Get(uri)
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if err != nil {
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return keys, 0, errors.Wrapf(err, "failed to connect to %s", uri)
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}
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defer resp.Body.Close()
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if err := json.NewDecoder(resp.Body).Decode(&keys); err != nil {
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return keys, 0, errors.Wrapf(err, "error reading %s", uri)
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}
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return keys, getCacheAge(resp.Header.Get("cache-control")), nil
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}
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func getCacheAge(cacheControl string) time.Duration {
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age := defaultCacheAge
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if len(cacheControl) > 0 {
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match := maxAgeRegex.FindAllStringSubmatch(cacheControl, -1)
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if len(match) > 0 {
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if len(match[0]) == 2 {
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maxAge := match[0][1]
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maxAgeInt, err := strconv.ParseInt(maxAge, 10, 64)
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if err != nil {
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return defaultCacheAge
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}
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age = time.Duration(maxAgeInt) * time.Second
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}
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}
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}
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return age
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}
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func getCacheJitter(age time.Duration) time.Duration {
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switch {
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case age > time.Hour:
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return defaultCacheJitter
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default:
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return age / 3
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}
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}
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func getExpirationTime(age time.Duration) time.Time {
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return time.Now().Truncate(time.Second).Add(age)
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}
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