72 lines
1.6 KiB
Go
72 lines
1.6 KiB
Go
package acme
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import (
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"crypto/rand"
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"encoding/base64"
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"errors"
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"sync"
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"time"
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)
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const nonceLifetime = 10 * time.Minute
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// NonceStore is a thread-safe single-use nonce store with expiry.
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// Nonces are short-lived per RFC 8555 §7.2.
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type NonceStore struct {
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nonces map[string]time.Time
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issued int
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mu sync.Mutex
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}
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// NewNonceStore creates a new nonce store.
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func NewNonceStore() *NonceStore {
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return &NonceStore{
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nonces: make(map[string]time.Time),
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}
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}
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// Issue generates, stores, and returns a new base64url-encoded nonce.
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func (s *NonceStore) Issue() (string, error) {
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b := make([]byte, 16)
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if _, err := rand.Read(b); err != nil {
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return "", err
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}
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nonce := base64.RawURLEncoding.EncodeToString(b)
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s.mu.Lock()
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defer s.mu.Unlock()
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s.nonces[nonce] = time.Now().Add(nonceLifetime)
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s.issued++
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// Purge expired nonces every 100 issues to bound memory.
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if s.issued%100 == 0 {
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s.purgeExpiredLocked()
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}
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return nonce, nil
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}
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// Consume validates that the nonce exists and has not expired, then removes it.
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// Returns an error if the nonce is unknown, expired, or already consumed.
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func (s *NonceStore) Consume(nonce string) error {
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s.mu.Lock()
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defer s.mu.Unlock()
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exp, ok := s.nonces[nonce]
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if !ok {
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return errors.New("unknown or already-consumed nonce")
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}
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delete(s.nonces, nonce)
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if time.Now().After(exp) {
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return errors.New("nonce expired")
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}
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return nil
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}
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// purgeExpiredLocked removes all expired nonces. Caller must hold s.mu.
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func (s *NonceStore) purgeExpiredLocked() {
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now := time.Now()
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for n, exp := range s.nonces {
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if now.After(exp) {
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delete(s.nonces, n)
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}
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}
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}
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