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Source file src/net/http/cgi/host.go

     1	// Copyright 2011 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	// This file implements the host side of CGI (being the webserver
     6	// parent process).
     7	
     8	// Package cgi implements CGI (Common Gateway Interface) as specified
     9	// in RFC 3875.
    10	//
    11	// Note that using CGI means starting a new process to handle each
    12	// request, which is typically less efficient than using a
    13	// long-running server. This package is intended primarily for
    14	// compatibility with existing systems.
    15	package cgi
    16	
    17	import (
    18		"bufio"
    19		"fmt"
    20		"io"
    21		"log"
    22		"net"
    23		"net/http"
    24		"os"
    25		"os/exec"
    26		"path/filepath"
    27		"regexp"
    28		"runtime"
    29		"strconv"
    30		"strings"
    31	)
    32	
    33	var trailingPort = regexp.MustCompile(`:([0-9]+)$`)
    34	
    35	var osDefaultInheritEnv = map[string][]string{
    36		"darwin":  {"DYLD_LIBRARY_PATH"},
    37		"freebsd": {"LD_LIBRARY_PATH"},
    38		"hpux":    {"LD_LIBRARY_PATH", "SHLIB_PATH"},
    39		"irix":    {"LD_LIBRARY_PATH", "LD_LIBRARYN32_PATH", "LD_LIBRARY64_PATH"},
    40		"linux":   {"LD_LIBRARY_PATH"},
    41		"openbsd": {"LD_LIBRARY_PATH"},
    42		"solaris": {"LD_LIBRARY_PATH", "LD_LIBRARY_PATH_32", "LD_LIBRARY_PATH_64"},
    43		"windows": {"SystemRoot", "COMSPEC", "PATHEXT", "WINDIR"},
    44	}
    45	
    46	// Handler runs an executable in a subprocess with a CGI environment.
    47	type Handler struct {
    48		Path string // path to the CGI executable
    49		Root string // root URI prefix of handler or empty for "/"
    50	
    51		// Dir specifies the CGI executable's working directory.
    52		// If Dir is empty, the base directory of Path is used.
    53		// If Path has no base directory, the current working
    54		// directory is used.
    55		Dir string
    56	
    57		Env        []string    // extra environment variables to set, if any, as "key=value"
    58		InheritEnv []string    // environment variables to inherit from host, as "key"
    59		Logger     *log.Logger // optional log for errors or nil to use log.Print
    60		Args       []string    // optional arguments to pass to child process
    61		Stderr     io.Writer   // optional stderr for the child process; nil means os.Stderr
    62	
    63		// PathLocationHandler specifies the root http Handler that
    64		// should handle internal redirects when the CGI process
    65		// returns a Location header value starting with a "/", as
    66		// specified in RFC 3875 § 6.3.2. This will likely be
    67		// http.DefaultServeMux.
    68		//
    69		// If nil, a CGI response with a local URI path is instead sent
    70		// back to the client and not redirected internally.
    71		PathLocationHandler http.Handler
    72	}
    73	
    74	func (h *Handler) stderr() io.Writer {
    75		if h.Stderr != nil {
    76			return h.Stderr
    77		}
    78		return os.Stderr
    79	}
    80	
    81	// removeLeadingDuplicates remove leading duplicate in environments.
    82	// It's possible to override environment like following.
    83	//    cgi.Handler{
    84	//      ...
    85	//      Env: []string{"SCRIPT_FILENAME=foo.php"},
    86	//    }
    87	func removeLeadingDuplicates(env []string) (ret []string) {
    88		for i, e := range env {
    89			found := false
    90			if eq := strings.IndexByte(e, '='); eq != -1 {
    91				keq := e[:eq+1] // "key="
    92				for _, e2 := range env[i+1:] {
    93					if strings.HasPrefix(e2, keq) {
    94						found = true
    95						break
    96					}
    97				}
    98			}
    99			if !found {
   100				ret = append(ret, e)
   101			}
   102		}
   103		return
   104	}
   105	
   106	func (h *Handler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
   107		root := h.Root
   108		if root == "" {
   109			root = "/"
   110		}
   111	
   112		if len(req.TransferEncoding) > 0 && req.TransferEncoding[0] == "chunked" {
   113			rw.WriteHeader(http.StatusBadRequest)
   114			rw.Write([]byte("Chunked request bodies are not supported by CGI."))
   115			return
   116		}
   117	
   118		pathInfo := req.URL.Path
   119		if root != "/" && strings.HasPrefix(pathInfo, root) {
   120			pathInfo = pathInfo[len(root):]
   121		}
   122	
   123		port := "80"
   124		if matches := trailingPort.FindStringSubmatch(req.Host); len(matches) != 0 {
   125			port = matches[1]
   126		}
   127	
   128		env := []string{
   129			"SERVER_SOFTWARE=go",
   130			"SERVER_NAME=" + req.Host,
   131			"SERVER_PROTOCOL=HTTP/1.1",
   132			"HTTP_HOST=" + req.Host,
   133			"GATEWAY_INTERFACE=CGI/1.1",
   134			"REQUEST_METHOD=" + req.Method,
   135			"QUERY_STRING=" + req.URL.RawQuery,
   136			"REQUEST_URI=" + req.URL.RequestURI(),
   137			"PATH_INFO=" + pathInfo,
   138			"SCRIPT_NAME=" + root,
   139			"SCRIPT_FILENAME=" + h.Path,
   140			"SERVER_PORT=" + port,
   141		}
   142	
   143		if remoteIP, remotePort, err := net.SplitHostPort(req.RemoteAddr); err == nil {
   144			env = append(env, "REMOTE_ADDR="+remoteIP, "REMOTE_HOST="+remoteIP, "REMOTE_PORT="+remotePort)
   145		} else {
   146			// could not parse ip:port, let's use whole RemoteAddr and leave REMOTE_PORT undefined
   147			env = append(env, "REMOTE_ADDR="+req.RemoteAddr, "REMOTE_HOST="+req.RemoteAddr)
   148		}
   149	
   150		if req.TLS != nil {
   151			env = append(env, "HTTPS=on")
   152		}
   153	
   154		for k, v := range req.Header {
   155			k = strings.Map(upperCaseAndUnderscore, k)
   156			if k == "PROXY" {
   157				// See Issue 16405
   158				continue
   159			}
   160			joinStr := ", "
   161			if k == "COOKIE" {
   162				joinStr = "; "
   163			}
   164			env = append(env, "HTTP_"+k+"="+strings.Join(v, joinStr))
   165		}
   166	
   167		if req.ContentLength > 0 {
   168			env = append(env, fmt.Sprintf("CONTENT_LENGTH=%d", req.ContentLength))
   169		}
   170		if ctype := req.Header.Get("Content-Type"); ctype != "" {
   171			env = append(env, "CONTENT_TYPE="+ctype)
   172		}
   173	
   174		envPath := os.Getenv("PATH")
   175		if envPath == "" {
   176			envPath = "/bin:/usr/bin:/usr/ucb:/usr/bsd:/usr/local/bin"
   177		}
   178		env = append(env, "PATH="+envPath)
   179	
   180		for _, e := range h.InheritEnv {
   181			if v := os.Getenv(e); v != "" {
   182				env = append(env, e+"="+v)
   183			}
   184		}
   185	
   186		for _, e := range osDefaultInheritEnv[runtime.GOOS] {
   187			if v := os.Getenv(e); v != "" {
   188				env = append(env, e+"="+v)
   189			}
   190		}
   191	
   192		if h.Env != nil {
   193			env = append(env, h.Env...)
   194		}
   195	
   196		env = removeLeadingDuplicates(env)
   197	
   198		var cwd, path string
   199		if h.Dir != "" {
   200			path = h.Path
   201			cwd = h.Dir
   202		} else {
   203			cwd, path = filepath.Split(h.Path)
   204		}
   205		if cwd == "" {
   206			cwd = "."
   207		}
   208	
   209		internalError := func(err error) {
   210			rw.WriteHeader(http.StatusInternalServerError)
   211			h.printf("CGI error: %v", err)
   212		}
   213	
   214		cmd := &exec.Cmd{
   215			Path:   path,
   216			Args:   append([]string{h.Path}, h.Args...),
   217			Dir:    cwd,
   218			Env:    env,
   219			Stderr: h.stderr(),
   220		}
   221		if req.ContentLength != 0 {
   222			cmd.Stdin = req.Body
   223		}
   224		stdoutRead, err := cmd.StdoutPipe()
   225		if err != nil {
   226			internalError(err)
   227			return
   228		}
   229	
   230		err = cmd.Start()
   231		if err != nil {
   232			internalError(err)
   233			return
   234		}
   235		if hook := testHookStartProcess; hook != nil {
   236			hook(cmd.Process)
   237		}
   238		defer cmd.Wait()
   239		defer stdoutRead.Close()
   240	
   241		linebody := bufio.NewReaderSize(stdoutRead, 1024)
   242		headers := make(http.Header)
   243		statusCode := 0
   244		headerLines := 0
   245		sawBlankLine := false
   246		for {
   247			line, isPrefix, err := linebody.ReadLine()
   248			if isPrefix {
   249				rw.WriteHeader(http.StatusInternalServerError)
   250				h.printf("cgi: long header line from subprocess.")
   251				return
   252			}
   253			if err == io.EOF {
   254				break
   255			}
   256			if err != nil {
   257				rw.WriteHeader(http.StatusInternalServerError)
   258				h.printf("cgi: error reading headers: %v", err)
   259				return
   260			}
   261			if len(line) == 0 {
   262				sawBlankLine = true
   263				break
   264			}
   265			headerLines++
   266			parts := strings.SplitN(string(line), ":", 2)
   267			if len(parts) < 2 {
   268				h.printf("cgi: bogus header line: %s", string(line))
   269				continue
   270			}
   271			header, val := parts[0], parts[1]
   272			header = strings.TrimSpace(header)
   273			val = strings.TrimSpace(val)
   274			switch {
   275			case header == "Status":
   276				if len(val) < 3 {
   277					h.printf("cgi: bogus status (short): %q", val)
   278					return
   279				}
   280				code, err := strconv.Atoi(val[0:3])
   281				if err != nil {
   282					h.printf("cgi: bogus status: %q", val)
   283					h.printf("cgi: line was %q", line)
   284					return
   285				}
   286				statusCode = code
   287			default:
   288				headers.Add(header, val)
   289			}
   290		}
   291		if headerLines == 0 || !sawBlankLine {
   292			rw.WriteHeader(http.StatusInternalServerError)
   293			h.printf("cgi: no headers")
   294			return
   295		}
   296	
   297		if loc := headers.Get("Location"); loc != "" {
   298			if strings.HasPrefix(loc, "/") && h.PathLocationHandler != nil {
   299				h.handleInternalRedirect(rw, req, loc)
   300				return
   301			}
   302			if statusCode == 0 {
   303				statusCode = http.StatusFound
   304			}
   305		}
   306	
   307		if statusCode == 0 && headers.Get("Content-Type") == "" {
   308			rw.WriteHeader(http.StatusInternalServerError)
   309			h.printf("cgi: missing required Content-Type in headers")
   310			return
   311		}
   312	
   313		if statusCode == 0 {
   314			statusCode = http.StatusOK
   315		}
   316	
   317		// Copy headers to rw's headers, after we've decided not to
   318		// go into handleInternalRedirect, which won't want its rw
   319		// headers to have been touched.
   320		for k, vv := range headers {
   321			for _, v := range vv {
   322				rw.Header().Add(k, v)
   323			}
   324		}
   325	
   326		rw.WriteHeader(statusCode)
   327	
   328		_, err = io.Copy(rw, linebody)
   329		if err != nil {
   330			h.printf("cgi: copy error: %v", err)
   331			// And kill the child CGI process so we don't hang on
   332			// the deferred cmd.Wait above if the error was just
   333			// the client (rw) going away. If it was a read error
   334			// (because the child died itself), then the extra
   335			// kill of an already-dead process is harmless (the PID
   336			// won't be reused until the Wait above).
   337			cmd.Process.Kill()
   338		}
   339	}
   340	
   341	func (h *Handler) printf(format string, v ...interface{}) {
   342		if h.Logger != nil {
   343			h.Logger.Printf(format, v...)
   344		} else {
   345			log.Printf(format, v...)
   346		}
   347	}
   348	
   349	func (h *Handler) handleInternalRedirect(rw http.ResponseWriter, req *http.Request, path string) {
   350		url, err := req.URL.Parse(path)
   351		if err != nil {
   352			rw.WriteHeader(http.StatusInternalServerError)
   353			h.printf("cgi: error resolving local URI path %q: %v", path, err)
   354			return
   355		}
   356		// TODO: RFC 3875 isn't clear if only GET is supported, but it
   357		// suggests so: "Note that any message-body attached to the
   358		// request (such as for a POST request) may not be available
   359		// to the resource that is the target of the redirect."  We
   360		// should do some tests against Apache to see how it handles
   361		// POST, HEAD, etc. Does the internal redirect get the same
   362		// method or just GET? What about incoming headers?
   363		// (e.g. Cookies) Which headers, if any, are copied into the
   364		// second request?
   365		newReq := &http.Request{
   366			Method:     "GET",
   367			URL:        url,
   368			Proto:      "HTTP/1.1",
   369			ProtoMajor: 1,
   370			ProtoMinor: 1,
   371			Header:     make(http.Header),
   372			Host:       url.Host,
   373			RemoteAddr: req.RemoteAddr,
   374			TLS:        req.TLS,
   375		}
   376		h.PathLocationHandler.ServeHTTP(rw, newReq)
   377	}
   378	
   379	func upperCaseAndUnderscore(r rune) rune {
   380		switch {
   381		case r >= 'a' && r <= 'z':
   382			return r - ('a' - 'A')
   383		case r == '-':
   384			return '_'
   385		case r == '=':
   386			// Maybe not part of the CGI 'spec' but would mess up
   387			// the environment in any case, as Go represents the
   388			// environment as a slice of "key=value" strings.
   389			return '_'
   390		}
   391		// TODO: other transformations in spec or practice?
   392		return r
   393	}
   394	
   395	var testHookStartProcess func(*os.Process) // nil except for some tests
   396	

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