tailscale: Add tailssh server

protocol/tailscale/tailssh/user_unix.go

@@ -0,0 +1,59 @@
+//go:build with_gvisor && !windows && !android
+
+package tailssh
+
+import (
+	"os"
+	"strconv"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/tailscale/util/osuser"
+)
+
+func resolveLocalUserNative(username string) (*adapter.PlatformUser, error) {
+	sysUser, shell, err := osuser.LookupByUsernameWithShell(username)
+	if err != nil {
+		return nil, err
+	}
+	uid, err := strconv.Atoi(sysUser.Uid)
+	if err != nil {
+		return nil, err
+	}
+	gid, err := strconv.Atoi(sysUser.Gid)
+	if err != nil {
+		return nil, err
+	}
+	var groups []int
+	groupIDs, err := osuser.GetGroupIds(sysUser)
+	if err == nil {
+		groups = make([]int, 0, len(groupIDs))
+		for _, raw := range groupIDs {
+			g, parseErr := strconv.Atoi(raw)
+			if parseErr != nil {
+				continue
+			}
+			groups = append(groups, g)
+		}
+	}
+	if shell == "" {
+		shell = defaultShell()
+	}
+	return &adapter.PlatformUser{
+		Username: sysUser.Username,
+		Uid:      uid,
+		Gid:      gid,
+		HomeDir:  sysUser.HomeDir,
+		Shell:    shell,
+		Groups:   groups,
+	}, nil
+}
+
+func defaultShell() string {
+	for _, shell := range []string{"/bin/zsh", "/bin/bash", "/bin/sh"} {
+		_, err := os.Stat(shell)
+		if err == nil {
+			return shell
+		}
+	}
+	return "/bin/sh"
+}