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ipn/ipnserver, util/winutil: update workaround for os/user.LookupId f…
…ailures on Windows to reject SIDs from deleted/invalid security principals. Our current workaround made the user check too lax, thus allowing deleted users. This patch adds a helper function to winutil that checks that the uid's SID represents a valid Windows security principal. Now if `lookupUserFromID` determines that the SID is invalid, we simply propagate the error. Updates #869 Signed-off-by: Aaron Klotz <aaron@tailscale.com>
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// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved. | ||
// Use of this source code is governed by a BSD-style | ||
// license that can be found in the LICENSE file. | ||
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//go:build windows | ||
// +build windows | ||
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package winutil | ||
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import ( | ||
"log" | ||
"syscall" | ||
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"golang.org/x/sys/windows" | ||
"golang.org/x/sys/windows/registry" | ||
) | ||
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const regBase = `SOFTWARE\Tailscale IPN` | ||
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// GetDesktopPID searches the PID of the process that's running the | ||
// currently active desktop and whether it was found. | ||
// Usually the PID will be for explorer.exe. | ||
func GetDesktopPID() (pid uint32, ok bool) { | ||
hwnd := windows.GetShellWindow() | ||
if hwnd == 0 { | ||
return 0, false | ||
} | ||
windows.GetWindowThreadProcessId(hwnd, &pid) | ||
return pid, pid != 0 | ||
} | ||
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func getRegString(name, defval string) string { | ||
key, err := registry.OpenKey(registry.LOCAL_MACHINE, RegBase, registry.READ) | ||
if err != nil { | ||
log.Printf("registry.OpenKey(%v): %v", RegBase, err) | ||
return defval | ||
} | ||
defer key.Close() | ||
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val, _, err := key.GetStringValue(name) | ||
if err != nil { | ||
if err != registry.ErrNotExist { | ||
log.Printf("registry.GetStringValue(%v): %v", name, err) | ||
} | ||
return defval | ||
} | ||
return val | ||
} | ||
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func getRegInteger(name string, defval uint64) uint64 { | ||
key, err := registry.OpenKey(registry.LOCAL_MACHINE, RegBase, registry.READ) | ||
if err != nil { | ||
log.Printf("registry.OpenKey(%v): %v", RegBase, err) | ||
return defval | ||
} | ||
defer key.Close() | ||
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val, _, err := key.GetIntegerValue(name) | ||
if err != nil { | ||
if err != registry.ErrNotExist { | ||
log.Printf("registry.GetIntegerValue(%v): %v", name, err) | ||
} | ||
return defval | ||
} | ||
return val | ||
} | ||
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var ( | ||
kernel32 = syscall.NewLazyDLL("kernel32.dll") | ||
procWTSGetActiveConsoleSessionId = kernel32.NewProc("WTSGetActiveConsoleSessionId") | ||
) | ||
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// TODO(crawshaw): replace with x/sys/windows... one day. | ||
// https://go-review.googlesource.com/c/sys/+/331909 | ||
func WTSGetActiveConsoleSessionId() uint32 { | ||
r1, _, _ := procWTSGetActiveConsoleSessionId.Call() | ||
return uint32(r1) | ||
} | ||
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func isSIDValidPrincipal(uid string) bool { | ||
usid, err := syscall.StringToSid(uid) | ||
if err != nil { | ||
return false | ||
} | ||
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_, _, accType, err := usid.LookupAccount("") | ||
if err != nil { | ||
return false | ||
} | ||
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switch accType { | ||
case syscall.SidTypeUser, syscall.SidTypeGroup, syscall.SidTypeDomain, syscall.SidTypeAlias, syscall.SidTypeWellKnownGroup, syscall.SidTypeComputer: | ||
return true | ||
default: | ||
// Reject deleted users, invalid SIDs, unknown SIDs, mandatory label SIDs, etc. | ||
return false | ||
} | ||
} |