chore: vendor

vendor/github.com/ProtonMail/go-crypto/openpgp/s2k/s2k_cache.go

@@ -0,0 +1,26 @@
+package s2k
+
+// Cache stores keys derived with s2k functions from one passphrase
+// to avoid recomputation if multiple items are encrypted with
+// the same parameters.
+type Cache map[Params][]byte
+
+// GetOrComputeDerivedKey tries to retrieve the key
+// for the given s2k parameters from the cache.
+// If there is no hit, it derives the key with the s2k function from the passphrase,
+// updates the cache, and returns the key.
+func (c *Cache) GetOrComputeDerivedKey(passphrase []byte, params *Params, expectedKeySize int) ([]byte, error) {
+	key, found := (*c)[*params]
+	if !found || len(key) != expectedKeySize {
+		var err error
+		derivedKey := make([]byte, expectedKeySize)
+		s2k, err := params.Function()
+		if err != nil {
+			return nil, err
+		}
+		s2k(derivedKey, passphrase)
+		(*c)[*params] = key
+		return derivedKey, nil
+	}
+	return key, nil
+}