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// 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"
"bytes"
"exec"
"fmt"
"http"
"io"
"log"
"os"
"path/filepath"
"regexp"
"strconv"
"strings"
)
var trailingPort = regexp.MustCompile(`:([0-9]+)$`)
// 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 "/"
Env []string // extra environment variables to set, if any
Logger *log.Logger // optional log for errors or nil to use log.Print
Args []string // optional arguments to pass to child process
}
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,
"HTTP_HOST=" + req.Host,
"GATEWAY_INTERFACE=CGI/1.1",
"REQUEST_METHOD=" + req.Method,
"QUERY_STRING=" + req.URL.RawQuery,
"REQUEST_URI=" + req.URL.RawPath,
"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")
}
if len(req.Cookie) > 0 {
b := new(bytes.Buffer)
for idx, c := range req.Cookie {
if idx > 0 {
b.Write([]byte("; "))
}
fmt.Fprintf(b, "%s=%s", c.Name, c.Value)
}
env = append(env, "HTTP_COOKIE="+b.String())
}
for k, v := range req.Header {
k = strings.Map(upperCaseAndUnderscore, k)
env = append(env, "HTTP_"+k+"="+strings.Join(v, ", "))
}
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...)
}
cwd, pathBase := filepath.Split(h.Path)
if cwd == "" {
cwd = "."
}
args := []string{h.Path}
args = append(args, h.Args...)
cmd, err := exec.Run(
pathBase,
args,
env,
cwd,
exec.Pipe, // stdin
exec.Pipe, // stdout
exec.PassThrough, // stderr (for now)
)
if err != nil {
rw.WriteHeader(http.StatusInternalServerError)
h.printf("CGI error: %v", err)
return
}
defer func() {
cmd.Stdin.Close()
cmd.Stdout.Close()
cmd.Wait(0) // no zombies
}()
if req.ContentLength != 0 {
go io.Copy(cmd.Stdin, req.Body)
}
linebody, _ := bufio.NewReaderSize(cmd.Stdout, 1024)
headers := rw.Header()
statusCode := http.StatusOK
for {
line, isPrefix, err := linebody.ReadLine()
if isPrefix {
rw.WriteHeader(http.StatusInternalServerError)
h.printf("CGI: long header line from subprocess.")
return
}
if err == os.EOF {
break
}
if err != nil {
rw.WriteHeader(http.StatusInternalServerError)
h.printf("CGI: error reading headers: %v", err)
return
}
if len(line) == 0 {
break
}
parts := strings.Split(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)
}
}
rw.WriteHeader(statusCode)
_, err = io.Copy(rw, linebody)
if err != nil {
h.printf("CGI: copy error: %v", err)
}
}
func (h *Handler) printf(format string, v ...interface{}) {
if h.Logger != nil {
h.Logger.Printf(format, v...)
} else {
log.Printf(format, v...)
}
}
func upperCaseAndUnderscore(rune int) int {
switch {
case rune >= 'a' && rune <= 'z':
return rune - ('a' - 'A')
case rune == '-':
return '_'
case rune == '=':
// 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 rune
}
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