1 files changed, 377 insertions, 0 deletions
diff --git a/src/net/http/cgi/host.go b/src/net/http/cgi/host.go
new file mode 100644
index 000000000..ec95a972c
--- /dev/null
+++ b/src/net/http/cgi/host.go
@@ -0,0 +1,377 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements the host side of CGI (being the webserver
+// parent process).
+
+// Package cgi implements CGI (Common Gateway Interface) as specified
+// in RFC 3875.
+//
+// Note that using CGI means starting a new process to handle each
+// request, which is typically less efficient than using a
+// long-running server.  This package is intended primarily for
+// compatibility with existing systems.
+package cgi
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"strconv"
+	"strings"
+)
+
+var trailingPort = regexp.MustCompile(`:([0-9]+)$`)
+
+var osDefaultInheritEnv = map[string][]string{
+	"darwin":  {"DYLD_LIBRARY_PATH"},
+	"freebsd": {"LD_LIBRARY_PATH"},
+	"hpux":    {"LD_LIBRARY_PATH", "SHLIB_PATH"},
+	"irix":    {"LD_LIBRARY_PATH", "LD_LIBRARYN32_PATH", "LD_LIBRARY64_PATH"},
+	"linux":   {"LD_LIBRARY_PATH"},
+	"openbsd": {"LD_LIBRARY_PATH"},
+	"solaris": {"LD_LIBRARY_PATH", "LD_LIBRARY_PATH_32", "LD_LIBRARY_PATH_64"},
+	"windows": {"SystemRoot", "COMSPEC", "PATHEXT", "WINDIR"},
+}
+
+// Handler runs an executable in a subprocess with a CGI environment.
+type Handler struct {
+	Path string // path to the CGI executable
+	Root string // root URI prefix of handler or empty for "/"
+
+	// Dir specifies the CGI executable's working directory.
+	// If Dir is empty, the base directory of Path is used.
+	// If Path has no base directory, the current working
+	// directory is used.
+	Dir string
+
+	Env        []string    // extra environment variables to set, if any, as "key=value"
+	InheritEnv []string    // environment variables to inherit from host, as "key"
+	Logger     *log.Logger // optional log for errors or nil to use log.Print
+	Args       []string    // optional arguments to pass to child process
+
+	// PathLocationHandler specifies the root http Handler that
+	// should handle internal redirects when the CGI process
+	// returns a Location header value starting with a "/", as
+	// specified in RFC 3875 § 6.3.2. This will likely be
+	// http.DefaultServeMux.
+	//
+	// If nil, a CGI response with a local URI path is instead sent
+	// back to the client and not redirected internally.
+	PathLocationHandler http.Handler
+}
+
+// removeLeadingDuplicates remove leading duplicate in environments.
+// It's possible to override environment like following.
+//    cgi.Handler{
+//      ...
+//      Env: []string{"SCRIPT_FILENAME=foo.php"},
+//    }
+func removeLeadingDuplicates(env []string) (ret []string) {
+	n := len(env)
+	for i := 0; i < n; i++ {
+		e := env[i]
+		s := strings.SplitN(e, "=", 2)[0]
+		found := false
+		for j := i + 1; j < n; j++ {
+			if s == strings.SplitN(env[j], "=", 2)[0] {
+				found = true
+				break
+			}
+		}
+		if !found {
+			ret = append(ret, e)
+		}
+	}
+	return
+}
+
+func (h *Handler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
+	root := h.Root
+	if root == "" {
+		root = "/"
+	}
+
+	if len(req.TransferEncoding) > 0 && req.TransferEncoding[0] == "chunked" {
+		rw.WriteHeader(http.StatusBadRequest)
+		rw.Write([]byte("Chunked request bodies are not supported by CGI."))
+		return
+	}
+
+	pathInfo := req.URL.Path
+	if root != "/" && strings.HasPrefix(pathInfo, root) {
+		pathInfo = pathInfo[len(root):]
+	}
+
+	port := "80"
+	if matches := trailingPort.FindStringSubmatch(req.Host); len(matches) != 0 {
+		port = matches[1]
+	}
+
+	env := []string{
+		"SERVER_SOFTWARE=go",
+		"SERVER_NAME=" + req.Host,
+		"SERVER_PROTOCOL=HTTP/1.1",
+		"HTTP_HOST=" + req.Host,
+		"GATEWAY_INTERFACE=CGI/1.1",
+		"REQUEST_METHOD=" + req.Method,
+		"QUERY_STRING=" + req.URL.RawQuery,
+		"REQUEST_URI=" + req.URL.RequestURI(),
+		"PATH_INFO=" + pathInfo,
+		"SCRIPT_NAME=" + root,
+		"SCRIPT_FILENAME=" + h.Path,
+		"REMOTE_ADDR=" + req.RemoteAddr,
+		"REMOTE_HOST=" + req.RemoteAddr,
+		"SERVER_PORT=" + port,
+	}
+
+	if req.TLS != nil {
+		env = append(env, "HTTPS=on")
+	}
+
+	for k, v := range req.Header {
+		k = strings.Map(upperCaseAndUnderscore, k)
+		joinStr := ", "
+		if k == "COOKIE" {
+			joinStr = "; "
+		}
+		env = append(env, "HTTP_"+k+"="+strings.Join(v, joinStr))
+	}
+
+	if req.ContentLength > 0 {
+		env = append(env, fmt.Sprintf("CONTENT_LENGTH=%d", req.ContentLength))
+	}
+	if ctype := req.Header.Get("Content-Type"); ctype != "" {
+		env = append(env, "CONTENT_TYPE="+ctype)
+	}
+
+	if h.Env != nil {
+		env = append(env, h.Env...)
+	}
+
+	envPath := os.Getenv("PATH")
+	if envPath == "" {
+		envPath = "/bin:/usr/bin:/usr/ucb:/usr/bsd:/usr/local/bin"
+	}
+	env = append(env, "PATH="+envPath)
+
+	for _, e := range h.InheritEnv {
+		if v := os.Getenv(e); v != "" {
+			env = append(env, e+"="+v)
+		}
+	}
+
+	for _, e := range osDefaultInheritEnv[runtime.GOOS] {
+		if v := os.Getenv(e); v != "" {
+			env = append(env, e+"="+v)
+		}
+	}
+
+	env = removeLeadingDuplicates(env)
+
+	var cwd, path string
+	if h.Dir != "" {
+		path = h.Path
+		cwd = h.Dir
+	} else {
+		cwd, path = filepath.Split(h.Path)
+	}
+	if cwd == "" {
+		cwd = "."
+	}
+
+	internalError := func(err error) {
+		rw.WriteHeader(http.StatusInternalServerError)
+		h.printf("CGI error: %v", err)
+	}
+
+	cmd := &exec.Cmd{
+		Path:   path,
+		Args:   append([]string{h.Path}, h.Args...),
+		Dir:    cwd,
+		Env:    env,
+		Stderr: os.Stderr, // for now
+	}
+	if req.ContentLength != 0 {
+		cmd.Stdin = req.Body
+	}
+	stdoutRead, err := cmd.StdoutPipe()
+	if err != nil {
+		internalError(err)
+		return
+	}
+
+	err = cmd.Start()
+	if err != nil {
+		internalError(err)
+		return
+	}
+	if hook := testHookStartProcess; hook != nil {
+		hook(cmd.Process)
+	}
+	defer cmd.Wait()
+	defer stdoutRead.Close()
+
+	linebody := bufio.NewReaderSize(stdoutRead, 1024)
+	headers := make(http.Header)
+	statusCode := 0
+	headerLines := 0
+	sawBlankLine := false
+	for {
+		line, isPrefix, err := linebody.ReadLine()
+		if isPrefix {
+			rw.WriteHeader(http.StatusInternalServerError)
+			h.printf("cgi: long header line from subprocess.")
+			return
+		}
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			rw.WriteHeader(http.StatusInternalServerError)
+			h.printf("cgi: error reading headers: %v", err)
+			return
+		}
+		if len(line) == 0 {
+			sawBlankLine = true
+			break
+		}
+		headerLines++
+		parts := strings.SplitN(string(line), ":", 2)
+		if len(parts) < 2 {
+			h.printf("cgi: bogus header line: %s", string(line))
+			continue
+		}
+		header, val := parts[0], parts[1]
+		header = strings.TrimSpace(header)
+		val = strings.TrimSpace(val)
+		switch {
+		case header == "Status":
+			if len(val) < 3 {
+				h.printf("cgi: bogus status (short): %q", val)
+				return
+			}
+			code, err := strconv.Atoi(val[0:3])
+			if err != nil {
+				h.printf("cgi: bogus status: %q", val)
+				h.printf("cgi: line was %q", line)
+				return
+			}
+			statusCode = code
+		default:
+			headers.Add(header, val)
+		}
+	}
+	if headerLines == 0 || !sawBlankLine {
+		rw.WriteHeader(http.StatusInternalServerError)
+		h.printf("cgi: no headers")
+		return
+	}
+
+	if loc := headers.Get("Location"); loc != "" {
+		if strings.HasPrefix(loc, "/") && h.PathLocationHandler != nil {
+			h.handleInternalRedirect(rw, req, loc)
+			return
+		}
+		if statusCode == 0 {
+			statusCode = http.StatusFound
+		}
+	}
+
+	if statusCode == 0 && headers.Get("Content-Type") == "" {
+		rw.WriteHeader(http.StatusInternalServerError)
+		h.printf("cgi: missing required Content-Type in headers")
+		return
+	}
+
+	if statusCode == 0 {
+		statusCode = http.StatusOK
+	}
+
+	// Copy headers to rw's headers, after we've decided not to
+	// go into handleInternalRedirect, which won't want its rw
+	// headers to have been touched.
+	for k, vv := range headers {
+		for _, v := range vv {
+			rw.Header().Add(k, v)
+		}
+	}
+
+	rw.WriteHeader(statusCode)
+
+	_, err = io.Copy(rw, linebody)
+	if err != nil {
+		h.printf("cgi: copy error: %v", err)
+		// And kill the child CGI process so we don't hang on
+		// the deferred cmd.Wait above if the error was just
+		// the client (rw) going away. If it was a read error
+		// (because the child died itself), then the extra
+		// kill of an already-dead process is harmless (the PID
+		// won't be reused until the Wait above).
+		cmd.Process.Kill()
+	}
+}
+
+func (h *Handler) printf(format string, v ...interface{}) {
+	if h.Logger != nil {
+		h.Logger.Printf(format, v...)
+	} else {
+		log.Printf(format, v...)
+	}
+}
+
+func (h *Handler) handleInternalRedirect(rw http.ResponseWriter, req *http.Request, path string) {
+	url, err := req.URL.Parse(path)
+	if err != nil {
+		rw.WriteHeader(http.StatusInternalServerError)
+		h.printf("cgi: error resolving local URI path %q: %v", path, err)
+		return
+	}
+	// TODO: RFC 3875 isn't clear if only GET is supported, but it
+	// suggests so: "Note that any message-body attached to the
+	// request (such as for a POST request) may not be available
+	// to the resource that is the target of the redirect."  We
+	// should do some tests against Apache to see how it handles
+	// POST, HEAD, etc. Does the internal redirect get the same
+	// method or just GET? What about incoming headers?
+	// (e.g. Cookies) Which headers, if any, are copied into the
+	// second request?
+	newReq := &http.Request{
+		Method:     "GET",
+		URL:        url,
+		Proto:      "HTTP/1.1",
+		ProtoMajor: 1,
+		ProtoMinor: 1,
+		Header:     make(http.Header),
+		Host:       url.Host,
+		RemoteAddr: req.RemoteAddr,
+		TLS:        req.TLS,
+	}
+	h.PathLocationHandler.ServeHTTP(rw, newReq)
+}
+
+func upperCaseAndUnderscore(r rune) rune {
+	switch {
+	case r >= 'a' && r <= 'z':
+		return r - ('a' - 'A')
+	case r == '-':
+		return '_'
+	case r == '=':
+		// Maybe not part of the CGI 'spec' but would mess up
+		// the environment in any case, as Go represents the
+		// environment as a slice of "key=value" strings.
+		return '_'
+	}
+	// TODO: other transformations in spec or practice?
+	return r
+}
+
+var testHookStartProcess func(*os.Process) // nil except for some tests