90 lines
2.4 KiB
Go
90 lines
2.4 KiB
Go
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/* SPDX-License-Identifier: MIT
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*
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* Copyright (C) 2019-2021 WireGuard LLC. All Rights Reserved.
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*/
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package conf
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import (
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"crypto/rand"
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"encoding/hex"
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"sync/atomic"
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"unsafe"
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"golang.org/x/sys/windows"
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)
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var encryptedFileSd unsafe.Pointer
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func randomFileName() string {
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var randBytes [32]byte
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_, err := rand.Read(randBytes[:])
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if err != nil {
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panic(err)
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}
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return hex.EncodeToString(randBytes[:]) + ".tmp"
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}
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func writeLockedDownFile(destination string, overwrite bool, contents []byte) error {
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var err error
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sa := &windows.SecurityAttributes{Length: uint32(unsafe.Sizeof(windows.SecurityAttributes{}))}
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sa.SecurityDescriptor = (*windows.SECURITY_DESCRIPTOR)(atomic.LoadPointer(&encryptedFileSd))
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if sa.SecurityDescriptor == nil {
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sa.SecurityDescriptor, err = windows.SecurityDescriptorFromString("O:SYG:SYD:PAI(A;;FA;;;SY)(A;;SD;;;BA)")
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if err != nil {
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return err
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}
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atomic.StorePointer(&encryptedFileSd, unsafe.Pointer(sa.SecurityDescriptor))
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}
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destination16, err := windows.UTF16FromString(destination)
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if err != nil {
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return err
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}
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tmpDestination := randomFileName()
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tmpDestination16, err := windows.UTF16PtrFromString(tmpDestination)
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if err != nil {
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return err
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}
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handle, err := windows.CreateFile(tmpDestination16, windows.GENERIC_WRITE|windows.DELETE, windows.FILE_SHARE_READ, sa, windows.CREATE_ALWAYS, windows.FILE_ATTRIBUTE_NORMAL, 0)
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if err != nil {
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return err
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}
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defer windows.CloseHandle(handle)
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deleteIt := func() {
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yes := byte(1)
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windows.SetFileInformationByHandle(handle, windows.FileDispositionInfo, &yes, 1)
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}
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n, err := windows.Write(handle, contents)
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if err != nil {
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deleteIt()
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return err
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}
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if n != len(contents) {
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deleteIt()
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return windows.ERROR_IO_INCOMPLETE
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}
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fileRenameInfo := &struct {
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replaceIfExists byte
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rootDirectory windows.Handle
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fileNameLength uint32
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fileName [windows.MAX_PATH]uint16
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}{replaceIfExists: func() byte {
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if overwrite {
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return 1
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} else {
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return 0
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}
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}(), fileNameLength: uint32(len(destination16) - 1)}
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if len(destination16) > len(fileRenameInfo.fileName) {
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deleteIt()
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return windows.ERROR_BUFFER_OVERFLOW
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}
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copy(fileRenameInfo.fileName[:], destination16[:])
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err = windows.SetFileInformationByHandle(handle, windows.FileRenameInfo, (*byte)(unsafe.Pointer(fileRenameInfo)), uint32(unsafe.Sizeof(*fileRenameInfo)))
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if err != nil {
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deleteIt()
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return err
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}
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return nil
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}
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