134 lines
3.5 KiB
Go
134 lines
3.5 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build !ios
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// +build !ios
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package version
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import (
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"bytes"
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"encoding/hex"
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"errors"
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"io"
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"os"
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"path"
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"path/filepath"
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"strings"
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)
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// CmdName returns either the base name of the current binary
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// using os.Executable. If os.Executable fails (it shouldn't), then
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// "cmd" is returned.
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func CmdName() string {
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e, err := os.Executable()
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if err != nil {
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return "cmd"
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}
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// fallbackName, the lowercase basename of the executable, is what we return if
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// we can't find the Go module metadata embedded in the file.
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fallbackName := filepath.Base(strings.TrimSuffix(strings.ToLower(e), ".exe"))
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var ret string
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info, err := findModuleInfo(e)
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if err != nil {
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return fallbackName
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}
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// v is like:
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// "path\ttailscale.com/cmd/tailscale\nmod\ttailscale.com\t(devel)\t\ndep\tgithub.com/apenwarr/fixconsole\tv0.0.0-20191012055117-5a9f6489cc29\th1:muXWUcay7DDy1/hEQWrYlBy+g0EuwT70sBHg65SeUc4=\ndep\tgithub....
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for _, line := range strings.Split(info, "\n") {
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if strings.HasPrefix(line, "path\t") {
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goPkg := strings.TrimPrefix(line, "path\t") // like "tailscale.com/cmd/tailscale"
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ret = path.Base(goPkg) // goPkg is always forward slashes; use path, not filepath
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break
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}
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}
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if ret == "" {
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return fallbackName
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}
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return ret
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}
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// findModuleInfo returns the Go module info from the executable file.
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func findModuleInfo(file string) (s string, err error) {
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f, err := os.Open(file)
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if err != nil {
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return "", err
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}
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defer f.Close()
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// Scan through f until we find infoStart.
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buf := make([]byte, 65536)
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start, err := findOffset(f, buf, infoStart)
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if err != nil {
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return "", err
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}
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start += int64(len(infoStart))
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// Seek to the end of infoStart and scan for infoEnd.
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_, err = f.Seek(start, io.SeekStart)
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if err != nil {
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return "", err
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}
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end, err := findOffset(f, buf, infoEnd)
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if err != nil {
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return "", err
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}
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length := end - start
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// As of Aug 2021, tailscaled's mod info was about 2k.
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if length > int64(len(buf)) {
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return "", errors.New("mod info too large")
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}
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// We have located modinfo. Read it into buf.
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buf = buf[:length]
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_, err = f.Seek(start, io.SeekStart)
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if err != nil {
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return "", err
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}
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_, err = io.ReadFull(f, buf)
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if err != nil {
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return "", err
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}
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return string(buf), nil
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}
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// findOffset finds the absolute offset of needle in f,
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// starting at f's current read position,
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// using temporary buffer buf.
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func findOffset(f *os.File, buf, needle []byte) (int64, error) {
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for {
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// Fill buf and look within it.
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n, err := f.Read(buf)
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if err != nil {
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return -1, err
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}
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i := bytes.Index(buf[:n], needle)
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if i < 0 {
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// Not found. Rewind a little bit in case we happened to end halfway through needle.
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rewind, err := f.Seek(int64(-len(needle)), io.SeekCurrent)
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if err != nil {
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return -1, err
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}
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// If we're at EOF and rewound exactly len(needle) bytes, return io.EOF.
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_, err = f.ReadAt(buf[:1], rewind+int64(len(needle)))
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if err == io.EOF {
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return -1, err
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}
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continue
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}
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// Found! Figure out exactly where.
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cur, err := f.Seek(0, io.SeekCurrent)
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if err != nil {
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return -1, err
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}
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return cur - int64(n) + int64(i), nil
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}
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}
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// These constants are taken from rsc.io/goversion.
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var (
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infoStart, _ = hex.DecodeString("3077af0c9274080241e1c107e6d618e6")
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infoEnd, _ = hex.DecodeString("f932433186182072008242104116d8f2")
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)
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