Initial QSfera import

Server/vendor/github.com/libregraph/oidc-go/hash.go

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2017-2019 Kopano
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *	http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package oidc
+
+import (
+	"crypto"
+	"encoding/base64"
+	"fmt"
+)
+
+// LeftmostHashBytes defines []bytes with Base64URL encoder via String().
+type LeftmostHashBytes []byte
+
+// LeftmostHash hashes the provided data with the provided hash function and
+// returns the left-most half the hashed bytes.
+func LeftmostHash(data []byte, hash crypto.Hash) LeftmostHashBytes {
+	hasher := hash.New()
+	hasher.Write(data)
+	result := hasher.Sum(nil)
+
+	return LeftmostHashBytes(result[:len(result)/2])
+}
+
+// String returns the Base64URL encoded string of the accociated bytes.
+func (lmhb LeftmostHashBytes) String() string {
+	return base64.RawURLEncoding.EncodeToString(lmhb)
+}
+
+// HashFromSigningMethod returns the matching crypto.Hash for the provided
+// signing alg.
+func HashFromSigningMethod(alg string) (hash crypto.Hash, err error) {
+	switch alg {
+	case "HS256":
+		fallthrough
+	case "RS256":
+		fallthrough
+	case "PS256":
+		fallthrough
+	case "ES256":
+		hash = crypto.SHA256
+
+	case "HS386":
+		fallthrough
+	case "RS384":
+		fallthrough
+	case "PS384":
+		fallthrough
+	case "ES384":
+		hash = crypto.SHA384
+
+	case "HS512":
+		fallthrough
+	case "RS512":
+		fallthrough
+	case "PS512":
+		fallthrough
+	case "ES512":
+		hash = crypto.SHA512
+
+	case "EdDSA":
+		hash = crypto.SHA512
+
+	default:
+		err = fmt.Errorf("Unkown alg %s", alg)
+	}
+
+	if !hash.Available() {
+		err = fmt.Errorf("Hash for %s is not available", alg)
+	}
+
+	return
+}