1 files changed, 107 insertions, 0 deletions
diff --git a/conf/dpapi/dpapi_windows.go b/conf/dpapi/dpapi_windows.go
new file mode 100644
index 00000000..03a5d8a3
--- /dev/null
+++ b/conf/dpapi/dpapi_windows.go
@@ -0,0 +1,107 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package dpapi
+
+import (
+	"errors"
+	"golang.org/x/sys/windows"
+	"runtime"
+	"unsafe"
+)
+
+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
+}