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/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2019-2020 WireGuard LLC. All Rights Reserved.
*/
package dpapi
import (
"errors"
"runtime"
"unsafe"
"fmt"
"golang.org/x/sys/windows"
)
func bytesToBlob(bytes []byte) *windows.DataBlob {
blob := &windows.DataBlob{Size: uint32(len(bytes))}
if len(bytes) > 0 {
blob.Data = &bytes[0]
}
return blob
}
func Encrypt(data []byte, name string) ([]byte, error) {
out := windows.DataBlob{}
err := windows.CryptProtectData(bytesToBlob(data), windows.StringToUTF16Ptr(name), nil, 0, nil, windows.CRYPTPROTECT_UI_FORBIDDEN, &out)
if err != nil {
return nil, fmt.Errorf("unable to encrypt DPAPI protected data: %w", err)
}
outSlice := *(*[]byte)(unsafe.Pointer(&(struct {
addr *byte
len int
cap int
}{out.Data, int(out.Size), int(out.Size)})))
ret := make([]byte, len(outSlice))
copy(ret, outSlice)
windows.LocalFree(windows.Handle(unsafe.Pointer(out.Data)))
return ret, nil
}
func Decrypt(data []byte, name string) ([]byte, error) {
out := windows.DataBlob{}
var outName *uint16
utf16Name, err := windows.UTF16PtrFromString(name)
if err != nil {
return nil, err
}
err = windows.CryptUnprotectData(bytesToBlob(data), &outName, nil, 0, nil, windows.CRYPTPROTECT_UI_FORBIDDEN, &out)
if err != nil {
return nil, fmt.Errorf("unable to decrypt DPAPI protected data: %w", err)
}
outSlice := *(*[]byte)(unsafe.Pointer(&(struct {
addr *byte
len int
cap int
}{out.Data, int(out.Size), int(out.Size)})))
ret := make([]byte, len(outSlice))
copy(ret, outSlice)
windows.LocalFree(windows.Handle(unsafe.Pointer(out.Data)))
// Note: this ridiculous open-coded strcmp is not constant time.
different := false
a := outName
b := utf16Name
for {
if *a != *b {
different = true
break
}
if *a == 0 || *b == 0 {
break
}
a = (*uint16)(unsafe.Pointer(uintptr(unsafe.Pointer(a)) + 2))
b = (*uint16)(unsafe.Pointer(uintptr(unsafe.Pointer(b)) + 2))
}
runtime.KeepAlive(utf16Name)
windows.LocalFree(windows.Handle(unsafe.Pointer(outName)))
if different {
return nil, errors.New("input name does not match the stored name")
}
return ret, nil
}
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