DPAPI.go

package main

import (
	"log"
	"syscall"
	"unsafe"
)

const (
	CRYPTPROTECT_UI_FORBIDDEN = 0x1
)

var (
	dllcrypt32  = syscall.NewLazyDLL("Crypt32.dll")
	dllkernel32 = syscall.NewLazyDLL("Kernel32.dll")

	procEncryptData = dllcrypt32.NewProc("CryptProtectData")
	procDecryptData = dllcrypt32.NewProc("CryptUnprotectData")
	procLocalFree   = dllkernel32.NewProc("LocalFree")
)

type DATA_BLOB struct {
	cbData uint32
	pbData *byte
}

func NewBlob(d []byte) *DATA_BLOB {
	if len(d) == 0 {
		return &DATA_BLOB{}
	}
	return &DATA_BLOB{
		pbData: &d[0],
		cbData: uint32(len(d)),
	}
}

func (b *DATA_BLOB) ToByteArray() []byte {
	d := make([]byte, b.cbData)
	copy(d, (*[1 << 30]byte)(unsafe.Pointer(b.pbData))[:])
	return d
}

func Encrypt(data []byte) ([]byte, error) {
	var outblob DATA_BLOB
	r, _, err := procEncryptData.Call(uintptr(unsafe.Pointer(NewBlob(data))), 0, 0, 0, 0, CRYPTPROTECT_UI_FORBIDDEN, uintptr(unsafe.Pointer(&outblob)))
	if r == 0 {
		return nil, err
	}
	defer procLocalFree.Call(uintptr(unsafe.Pointer(outblob.pbData)))
	return outblob.ToByteArray(), nil
}

func Decrypt(data []byte) ([]byte, error) {
	var outblob DATA_BLOB
	r, _, err := procDecryptData.Call(uintptr(unsafe.Pointer(NewBlob(data))), 0, 0, 0, 0, CRYPTPROTECT_UI_FORBIDDEN, uintptr(unsafe.Pointer(&outblob)))
	if r == 0 {
		return nil, err
	}
	defer procLocalFree.Call(uintptr(unsafe.Pointer(outblob.pbData)))
	return outblob.ToByteArray(), nil
}

func main() {
	const secret = "Hello World"
	enc, err := Encrypt([]byte(secret))
	if err != nil {
		log.Fatalf("Encrypt failed: %v", err)
	}
	log.Printf("%v", enc)
	dec, err := Decrypt(enc)
	if err != nil {
		log.Fatalf("Decrypt failed: %v", err)
	}
	if string(dec) != secret {
		log.Fatalf("decrypted secret \"%s\" does not match to \"%s\".", dec, secret)
	}
	log.Printf(string(dec))
}