Merge pull request #90 from microsoft/removeenc

Don't use encoding/binary

Author: karianna

cng/hkdf.go

@@ -7,7 +7,6 @@
 package cng
 
 import (
-	"encoding/binary"
 	"errors"
 	"hash"
 	"runtime"
@@ -83,7 +82,7 @@ func ExtractHKDF(h func() hash.Hash, secret, salt []byte) ([]byte, error) {
 	if len(blob) < 4 {
 		return nil, errors.New("cng: exported key is corrupted")
 	}
-	cbHashName := binary.BigEndian.Uint32(blob)
+	cbHashName := bigEndianUint32(blob)
 	blob = blob[4:]
 	if len(blob) < int(cbHashName) {
 		return nil, errors.New("cng: exported key is corrupted")
@@ -122,3 +121,8 @@ func ExpandHKDF(h func() hash.Hash, pseudorandomKey, info []byte, keyLength int)
 	}
 	return out, err
 }
+
+func bigEndianUint32(b []byte) uint32 {
+	_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
+	return uint32(b[3]) | uint32(b[2])<<8 | uint32(b[1])<<16 | uint32(b[0])<<24
+}