Add dependencies/vendor (whatsapp)

vendor/go.mau.fi/whatsmeow/util/hkdfutil/hkdf.go

@@ -0,0 +1,28 @@
+// Copyright (c) 2021 Tulir Asokan
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+// Package hkdfutil contains a simple wrapper for golang.org/x/crypto/hkdf that reads a specified number of bytes.
+package hkdfutil
+
+import (
+	"crypto/sha256"
+	"fmt"
+
+	"golang.org/x/crypto/hkdf"
+)
+
+func SHA256(key, salt, info []byte, length uint8) []byte {
+	data := make([]byte, length)
+	h := hkdf.New(sha256.New, key, salt, info)
+	n, err := h.Read(data)
+	if err != nil {
+		// Length is limited to 255 by being uint8, so these errors can't actually happen
+		panic(fmt.Errorf("failed to expand key: %w", err))
+	} else if uint8(n) != length {
+		panic(fmt.Errorf("didn't read enough bytes (got %d, wanted %d)", n, length))
+	}
+	return data
+}