聊聊 Git 的三种传输协议及实现

➜  .git git:(master) cat info/refs21f45f60fa582d085497fb2d3bb50163e59891ee	refs/heads/historyef8021acf4c29eb35e3084b7dc543c173d67ad2a	refs/heads/master

// From: https://gitee.com/kesin/go-git-protocols/blob/master/http-dumb/git-http-dumb.go
// Usage: ./http-dumb -repo=/xxx/xxx/xxx/ -port=8881
func main() {	repo := flag.String("repo", "/Users/zoker/Tmp/repositories", "Specify a repositories root dir.")	port := flag.String("port", "8881", "Specify a port to start process.")	flag.Parse()
	http.Handle("/", http.FileServer(http.Dir(*repo)))	fmt.Printf("Dumb http server start at port %s on dir %s \n", *port, *repo)	_ = http.ListenAndServe(fmt.Sprintf(":%s", *port), nil)}

# 请求体GET http://git.oschina.net/kesin/getingblog.git/info/refs?service=git-upload-pack HTTP/1.1Host: git.oschina.netUser-Agent: git/2.24.3 (Apple Git-128)Accept-Encoding: deflate, gzipProxy-Connection: Keep-AlivePragma: no-cache
# Gitee 响应HTTP/1.1 200 OKCache-Control: no-cache, max-age=0, must-revalidateConnection: keep-aliveContent-Type: application/x-git-upload-pack-advertisementExpires: Fri, 01 Jan 1980 00:00:00 GMTPragma: no-cacheServer: nginxX-Frame-Options: DENYX-Gitee-Server: Brzox/3.2.3X-Request-Id: 96e0af82-dffe-4352-9fa5-92f652ed39c7Transfer-Encoding: chunked
001e# service=git-upload-pack0000010fca6ce400113082241c1f45daa513fabacc66a20d HEADmulti_ack thin-pack side-band side-band-64k ofs-delta shallow deepen-since deepen-not deepen-relative no-progress include-tag multi_ack_detailed no-done symref=HEAD:refs/heads/testbody object-format=sha1 agent=git/2.29.2003c351bad7fdb498c9634442f0c3f60396e8b92f4fb refs/heads/dev004092ad3c48e627782980f82b0a8b05a1a5221d8b74 refs/heads/dev-pro0040ae747d0a0094af3d27ee86c33e645139728b2a9a refs/heads/develop0000

--[no-]strictDo not try <directory>/.git/ if <directory> is no Git directory.
--timeout=<n>Interrupt transfer after <n> seconds of inactivity.
--stateless-rpcPerform only a single read-write cycle with stdin and stdout. This fits with the HTTP POST request processingmodel where a program may read the request, write a response, and must exit.
--advertise-refsOnly the initial ref advertisement is output, and the program exits immediately. This fits with the HTTP GETrequest model, where no request content is received but a response must be produced.
<directory>The repository to sync from.

➜  .git git:(master) git upload-pack --stateless-rpc --advertise-refs .010aef8021acf4c29eb35e3084b7dc543c173d67ad2a HEADmulti_ack thin-pack side-band side-band-64k ofs-delta shallow deepen-since deepen-not deepen-relative no-progress include-tag multi_ack_detailed no-done symref=HEAD:refs/heads/master agent=git/2.24.3.(Apple.Git-128)003fef8021acf4c29eb35e3084b7dc543c173d67ad2a refs/heads/master0000%

// 支持 upload-pack 和 receive-pack 两种操作引用发现的处理func handleRefs(w http.ResponseWriter, r *http.Request) {	vars := mux.Vars(r)	repoName := vars["repo"]	repoPath := fmt.Sprintf("%s%s", *repoRoot, repoName)	service := r.FormValue("service")	pFirst := fmt.Sprintf("# service=%s\n", service) // 本示例仅处理 protocol v1
	handleRefsHeader(&w, service) // Headers 处理
	cmdRefs := exec.Command("git", service[4:], "--stateless-rpc", "--advertise-refs", repoPath)	refsBytes, _ := cmdRefs.Output() // 获取 pkt-line 数据	responseBody := fmt.Sprintf("%04x# service=%s\n0000%s", len(pFirst)+4, service, string(refsBytes)) // 拼接 Body
	_, _ = w.Write([]byte(responseBody))}
// 按照要求设置 Headersfunc handleRefsHeader(w *http.ResponseWriter, service string) {	cType := fmt.Sprintf("application/x-%s-advertisement", service)	(*w).Header().Add("Content-Type", cType)	(*w).Header().Set("Expires", "Fri, 01 Jan 1980 00:00:00 GMT")	(*w).Header().Set("Pragma", "no-cache")	(*w).Header().Set("Cache-Control", "no-cache, max-age=0, must-revalidate")}

POST http://gitee.com/kesin/bigRepo/git-upload-pack HTTP/1.1Host: gitee.comUser-Agent: git/2.24.3 (Apple Git-128)Accept-Encoding: deflate, gzipProxy-Connection: Keep-AliveContent-Type: application/x-git-upload-pack-requestAccept: application/x-git-upload-pack-resultContent-Length: 443
00b4want bee4d57e3adaddf355315edf2c046db33aa299e8 multi_ack_detailed no-done side-band-64k thin-pack include-tag ofs-delta deepen-since deepen-not agent=git/2.24.3.(Apple.Git-128)00000032have 82a8768e7fd48f76772628d5a55475c51ea4fa2f0032have 4f7a2ea0920751a5501debbbc1debc403b46d7a00032have 7c141974a30bd218d4257d4292890a9008d301110032have f6bb00364bd5000a45185b9b16c028f485e842db0032have 47b7bd17fcb7de646cf49a26efb43c7b708498f30009done

   // https://github.com/git/git/blob/master/Documentation/technical/http-protocol.txt#L474   C: POST $GIT_URL/git-receive-pack HTTP/1.0   C: Content-Type: application/x-git-receive-pack-request   C:   C: ....0a53e9ddeaddad63ad106860237bbf53411d11a7 441b40d833fdfa93eb2908e52742248faf0ee993 refs/heads/maint\0 report-status   C: 0000   C: PACK....

func processPack(w http.ResponseWriter, r *http.Request) {	vars := mux.Vars(r)	repoName := vars["repo"]	// request repo not end with .git is supported with upload-pack	repoPath := fmt.Sprintf("%s%s", *repoRoot, repoName)	service := vars["service"]
	handlePackHeader(&w, service)
	// 启动一个进程，通过标准输入输出进行数据交换	cmdPack := exec.Command("git", service[4:], "--stateless-rpc", repoPath)	cmdStdin, err := cmdPack.StdinPipe()	cmdStdout, err := cmdPack.StdoutPipe()	_ = cmdPack.Start()
	// 客户端和服务端数据交换	go func() {		_, _ = io.Copy(cmdStdin, r.Body)		_ = cmdStdin.Close()	}()	_, _ = io.Copy(w, cmdStdout)	_ = cmdPack.Wait() // wait for std complete}

003egit-upload-pack /project.git\0host=myserver.com\0\0version=1\0

➜  hello git:(master) ✗ git upload-pack .010234d8ed9a9f73d2cac9f50a8c8c03e4643990a2bf HEADmulti_ack thin-pack side-band side-band-64k ofs-delta shallow deepen-since deepen-not deepen-relative no-progress include-tag multi_ack_detailed symref=HEAD:refs/heads/master agent=git/2.24.3.(Apple.Git-128)003f34d8ed9a9f73d2cac9f50a8c8c03e4643990a2bf refs/heads/master0000

// error-line     =  PKT-LINE("ERR" SP explanation-text)func exitSession(conn net.Conn, err error) {	errStr := fmt.Sprintf("ERR %s", err.Error())	pktData := fmt.Sprintf("%04x%s", len(errStr)+4, errStr)	_, _ = conn.Write([]byte(pktData))	_ = conn.Close()}

func handleRequest(conn net.Conn) {    //处理首次客户端发来的数据，拿到 action 以及 仓库信息    service, repo, err := parseData(conn) 
    // 仅支持 Push 和 Fetch 操作    if service != "git-upload-pack" && service != "git-receive-pack" {		exitSession(conn, errors.New("Not allowed command. \n"))	}	repoPath := fmt.Sprintf("%s%s", *repoRoot, repo)
	cmdPack := exec.Command("git", service[4:], repoPath)	cmdStdin, err := cmdPack.StdinPipe()	cmdStdout, err := cmdPack.StdoutPipe()	_ = cmdPack.Start()
    // 客户端服务端数据交换	go func() { _, _ = io.Copy(cmdStdin, conn) }()	_, _ = io.Copy(conn, cmdStdout)	err = cmdPack.Wait()}

ssh user@example.com "git-upload-pack '/project.git'"

func main() {	// init host key and public key authentication	var hostOption ssh.Option	hostOption = ssh.HostKeyFile(*hostKeyPath)	keyHandler := func(ctx ssh.Context, key ssh.PublicKey) bool {		// replace your public key auth logic here		pubKeyStr := gossh.MarshalAuthorizedKey(key)		return true // set false to use password authentication	}	keyOption := ssh.PublicKeyAuth(keyHandler)
	// password validate authentication	pwdHandler := func(ctx ssh.Context, password string) bool {		// replace your own password auth logic here		if ctx.User() == "zoker" && password == "zoker" {			return true		}		return false	}	pwdOption := ssh.PasswordAuth(pwdHandler)
	// process ssh session pack	ssh.Handle(func(s ssh.Session) {		handlePack(s) // 处理请求	})
	addr := fmt.Sprintf(":%s", *port)	log.Printf("Starting ssh server on port %s \n", *port)	log.Fatal(ssh.ListenAndServe(addr, nil, hostOption, pwdOption, keyOption))}
func handlePack(s ssh.Session) {	args := s.Command()	service := args[0]	repoName := args[1]    // allowed command	if service != "git-upload-pack" && service != "git-receive-pack" {		exitSession(s, errors.New("Not allowed command. \n"))	}
	repoPath := fmt.Sprintf("%s%s", *repoRoot, repoName)    // 启动标准输入输出进行数据交换，下面的处理是否似曾相识？没错，Git 协议也是同样的处理方式	cmdPack := exec.Command("git", service[4:], repoPath)	cmdStdin, err := cmdPack.StdinPipe()	cmdStdout, err := cmdPack.StdoutPipe()	_ = cmdPack.Start()	go func() { _, _ = io.Copy(cmdStdin, s) }()	_, _ = io.Copy(s, cmdStdout)	_ = cmdPack.Wait()}