paths: remove wasm file, no-op stubs, make OS-specific funcs consistent

Some OS-specific funcs were defined in init. Another used build tags
and required all other OSes to stub it out. Another one could just be in
the portable file.

Simplify it a bit, removing a file and some stubs in the process.

Updates #5794

Change-Id: I51df8772cc60a9335ac4c1dc0ab59b8a0d236961
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

paths/paths.go

@@ -45,7 +45,14 @@ func DefaultTailscaledSocket() string {
 	return "tailscaled.sock"
 }
 
-var stateFileFunc func() string
+// Overridden in init by OS-specific files.
+var (
+	stateFileFunc func() string
+
+	// ensureStateDirPerms applies a restrictive ACL/chmod
+	// to the provided directory.
+	ensureStateDirPerms = func(string) error { return nil }
+)
 
 // DefaultTailscaledStateFile returns the default path to the
 // tailscaled state file, or the empty string if there's no reasonable
@@ -67,6 +74,16 @@ func MkStateDir(dirPath string) error {
 	if err := os.MkdirAll(dirPath, 0700); err != nil {
 		return err
 	}
-
 	return ensureStateDirPerms(dirPath)
 }
+
+// LegacyStateFilePath returns the legacy path to the state file when
+// it was stored under the current user's %LocalAppData%.
+//
+// It is only called on Windows.
+func LegacyStateFilePath() string {
+	if runtime.GOOS == "windows" {
+		return filepath.Join(os.Getenv("LocalAppData"), "Tailscale", "server-state.conf")
+	}
+	return ""
+}

paths/paths_unix.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build !windows && !js && !wasip1
+//go:build !windows && !wasm && !plan9
 
 package paths
 
@@ -17,6 +17,7 @@ import (
 
 func init() {
 	stateFileFunc = stateFileUnix
+	ensureStateDirPerms = ensureStateDirPermsUnix
 }
 
 func statePath() string {
@@ -65,7 +66,7 @@ func xdgDataHome() string {
 	return filepath.Join(os.Getenv("HOME"), ".local/share")
 }
 
-func ensureStateDirPerms(dir string) error {
+func ensureStateDirPermsUnix(dir string) error {
 	if filepath.Base(dir) != "tailscale" {
 		return nil
 	}
@@ -83,8 +84,3 @@ func ensureStateDirPerms(dir string) error {
 	}
 	return os.Chmod(dir, perm)
 }
-
-// LegacyStateFilePath is not applicable to UNIX; it is just stubbed out.
-func LegacyStateFilePath() string {
-	return ""
-}

paths/paths_wasm.go

@@ -1,10 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-package paths
-
-func ensureStateDirPerms(dirPath string) error {
-	return nil
-}
-
-func LegacyStateFilePath() string { return "" }

paths/paths_windows.go

@@ -12,7 +12,11 @@ import (
 	"tailscale.com/util/winutil"
 )
 
-// ensureStateDirPerms applies a restrictive ACL to the directory specified by dirPath.
+func init() {
+	ensureStateDirPerms = ensureStateDirPermsWindows
+}
+
+// ensureStateDirPermsWindows applies a restrictive ACL to the directory specified by dirPath.
 // It sets the following security attributes on the directory:
 // Owner: The user for the current process;
 // Primary Group: The primary group for the current process;
@@ -26,7 +30,7 @@ import (
 //
 //	However, any directories and/or files created within this
 //	directory *do* inherit the ACL that we are setting.
-func ensureStateDirPerms(dirPath string) error {
+func ensureStateDirPermsWindows(dirPath string) error {
 	fi, err := os.Stat(dirPath)
 	if err != nil {
 		return err
@@ -94,9 +98,3 @@ func ensureStateDirPerms(dirPath string) error {
 	return windows.SetNamedSecurityInfo(dirPath, windows.SE_FILE_OBJECT, flags,
 		sids.User, sids.PrimaryGroup, dacl, nil)
 }
-
-// LegacyStateFilePath returns the legacy path to the state file when it was stored under the
-// current user's %LocalAppData%.
-func LegacyStateFilePath() string {
-	return filepath.Join(os.Getenv("LocalAppData"), "Tailscale", "server-state.conf")
-}