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/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
*/
package dpapi
import (
"errors"
"runtime"
"unsafe"
"golang.org/x/sys/windows"
)
const (
dpCRYPTPROTECT_UI_FORBIDDEN uint32 = 0x1
dpCRYPTPROTECT_LOCAL_MACHINE uint32 = 0x4
dpCRYPTPROTECT_CRED_SYNC uint32 = 0x8
dpCRYPTPROTECT_AUDIT uint32 = 0x10
dpCRYPTPROTECT_NO_RECOVERY uint32 = 0x20
dpCRYPTPROTECT_VERIFY_PROTECTION uint32 = 0x40
dpCRYPTPROTECT_CRED_REGENERATE uint32 = 0x80
)
type dpBlob struct {
len uint32
data uintptr
}
func bytesToBlob(bytes []byte) *dpBlob {
blob := &dpBlob{}
blob.len = uint32(len(bytes))
if len(bytes) > 0 {
blob.data = uintptr(unsafe.Pointer(&bytes[0]))
}
return blob
}
//sys cryptProtectData(dataIn *dpBlob, name *uint16, optionalEntropy *dpBlob, reserved uintptr, promptStruct uintptr, flags uint32, dataOut *dpBlob) (err error) = crypt32.CryptProtectData
func Encrypt(data []byte, name string) ([]byte, error) {
out := dpBlob{}
err := cryptProtectData(bytesToBlob(data), windows.StringToUTF16Ptr(name), nil, 0, 0, dpCRYPTPROTECT_UI_FORBIDDEN, &out)
if err != nil {
return nil, errors.New("Unable to encrypt DPAPI protected data: " + err.Error())
}
outSlice := *(*[]byte)(unsafe.Pointer(&(struct {
addr uintptr
len int
cap int
}{out.data, int(out.len), int(out.len)})))
ret := make([]byte, len(outSlice))
copy(ret, outSlice)
windows.LocalFree(windows.Handle(out.data))
return ret, nil
}
//sys cryptUnprotectData(dataIn *dpBlob, name **uint16, optionalEntropy *dpBlob, reserved uintptr, promptStruct uintptr, flags uint32, dataOut *dpBlob) (err error) = crypt32.CryptUnprotectData
func Decrypt(data []byte, name string) ([]byte, error) {
out := dpBlob{}
var outName *uint16
utf16Name, err := windows.UTF16PtrFromString(name)
if err != nil {
return nil, err
}
err = cryptUnprotectData(bytesToBlob(data), &outName, nil, 0, 0, dpCRYPTPROTECT_UI_FORBIDDEN, &out)
if err != nil {
return nil, errors.New("Unable to decrypt DPAPI protected data: " + err.Error())
}
outSlice := *(*[]byte)(unsafe.Pointer(&(struct {
addr uintptr
len int
cap int
}{out.data, int(out.len), int(out.len)})))
ret := make([]byte, len(outSlice))
copy(ret, outSlice)
windows.LocalFree(windows.Handle(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("The input name does not match the stored name")
}
return ret, nil
}
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