Source file src/pkg/net/http/cgi/child.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 CGI from the perspective of a child
     6	// process.
     7	
     8	package cgi
     9	
    10	import (
    11		"bufio"
    12		"crypto/tls"
    13		"errors"
    14		"fmt"
    15		"io"
    16		"io/ioutil"
    17		"net"
    18		"net/http"
    19		"net/url"
    20		"os"
    21		"strconv"
    22		"strings"
    23	)
    24	
    25	// Request returns the HTTP request as represented in the current
    26	// environment. This assumes the current program is being run
    27	// by a web server in a CGI environment.
    28	// The returned Request's Body is populated, if applicable.
    29	func Request() (*http.Request, error) {
    30		r, err := RequestFromMap(envMap(os.Environ()))
    31		if err != nil {
    32			return nil, err
    33		}
    34		if r.ContentLength > 0 {
    35			r.Body = ioutil.NopCloser(io.LimitReader(os.Stdin, r.ContentLength))
    36		}
    37		return r, nil
    38	}
    39	
    40	func envMap(env []string) map[string]string {
    41		m := make(map[string]string)
    42		for _, kv := range env {
    43			if idx := strings.Index(kv, "="); idx != -1 {
    44				m[kv[:idx]] = kv[idx+1:]
    45			}
    46		}
    47		return m
    48	}
    49	
    50	// RequestFromMap creates an http.Request from CGI variables.
    51	// The returned Request's Body field is not populated.
    52	func RequestFromMap(params map[string]string) (*http.Request, error) {
    53		r := new(http.Request)
    54		r.Method = params["REQUEST_METHOD"]
    55		if r.Method == "" {
    56			return nil, errors.New("cgi: no REQUEST_METHOD in environment")
    57		}
    58	
    59		r.Proto = params["SERVER_PROTOCOL"]
    60		var ok bool
    61		r.ProtoMajor, r.ProtoMinor, ok = http.ParseHTTPVersion(r.Proto)
    62		if !ok {
    63			return nil, errors.New("cgi: invalid SERVER_PROTOCOL version")
    64		}
    65	
    66		r.Close = true
    67		r.Trailer = http.Header{}
    68		r.Header = http.Header{}
    69	
    70		r.Host = params["HTTP_HOST"]
    71	
    72		if lenstr := params["CONTENT_LENGTH"]; lenstr != "" {
    73			clen, err := strconv.ParseInt(lenstr, 10, 64)
    74			if err != nil {
    75				return nil, errors.New("cgi: bad CONTENT_LENGTH in environment: " + lenstr)
    76			}
    77			r.ContentLength = clen
    78		}
    79	
    80		if ct := params["CONTENT_TYPE"]; ct != "" {
    81			r.Header.Set("Content-Type", ct)
    82		}
    83	
    84		// Copy "HTTP_FOO_BAR" variables to "Foo-Bar" Headers
    85		for k, v := range params {
    86			if !strings.HasPrefix(k, "HTTP_") || k == "HTTP_HOST" {
    87				continue
    88			}
    89			r.Header.Add(strings.Replace(k[5:], "_", "-", -1), v)
    90		}
    91	
    92		// TODO: cookies.  parsing them isn't exported, though.
    93	
    94		if r.Host != "" {
    95			// Hostname is provided, so we can reasonably construct a URL,
    96			// even if we have to assume 'http' for the scheme.
    97			rawurl := "http://" + r.Host + params["REQUEST_URI"]
    98			url, err := url.Parse(rawurl)
    99			if err != nil {
   100				return nil, errors.New("cgi: failed to parse host and REQUEST_URI into a URL: " + rawurl)
   101			}
   102			r.URL = url
   103		}
   104		// Fallback logic if we don't have a Host header or the URL
   105		// failed to parse
   106		if r.URL == nil {
   107			uriStr := params["REQUEST_URI"]
   108			url, err := url.Parse(uriStr)
   109			if err != nil {
   110				return nil, errors.New("cgi: failed to parse REQUEST_URI into a URL: " + uriStr)
   111			}
   112			r.URL = url
   113		}
   114	
   115		// There's apparently a de-facto standard for this.
   116		// http://docstore.mik.ua/orelly/linux/cgi/ch03_02.htm#ch03-35636
   117		if s := params["HTTPS"]; s == "on" || s == "ON" || s == "1" {
   118			r.TLS = &tls.ConnectionState{HandshakeComplete: true}
   119		}
   120	
   121		// Request.RemoteAddr has its port set by Go's standard http
   122		// server, so we do here too. We don't have one, though, so we
   123		// use a dummy one.
   124		r.RemoteAddr = net.JoinHostPort(params["REMOTE_ADDR"], "0")
   125	
   126		return r, nil
   127	}
   128	
   129	// Serve executes the provided Handler on the currently active CGI
   130	// request, if any. If there's no current CGI environment
   131	// an error is returned. The provided handler may be nil to use
   132	// http.DefaultServeMux.
   133	func Serve(handler http.Handler) error {
   134		req, err := Request()
   135		if err != nil {
   136			return err
   137		}
   138		if handler == nil {
   139			handler = http.DefaultServeMux
   140		}
   141		rw := &response{
   142			req:    req,
   143			header: make(http.Header),
   144			bufw:   bufio.NewWriter(os.Stdout),
   145		}
   146		handler.ServeHTTP(rw, req)
   147		rw.Write(nil) // make sure a response is sent
   148		if err = rw.bufw.Flush(); err != nil {
   149			return err
   150		}
   151		return nil
   152	}
   153	
   154	type response struct {
   155		req        *http.Request
   156		header     http.Header
   157		bufw       *bufio.Writer
   158		headerSent bool
   159	}
   160	
   161	func (r *response) Flush() {
   162		r.bufw.Flush()
   163	}
   164	
   165	func (r *response) Header() http.Header {
   166		return r.header
   167	}
   168	
   169	func (r *response) Write(p []byte) (n int, err error) {
   170		if !r.headerSent {
   171			r.WriteHeader(http.StatusOK)
   172		}
   173		return r.bufw.Write(p)
   174	}
   175	
   176	func (r *response) WriteHeader(code int) {
   177		if r.headerSent {
   178			// Note: explicitly using Stderr, as Stdout is our HTTP output.
   179			fmt.Fprintf(os.Stderr, "CGI attempted to write header twice on request for %s", r.req.URL)
   180			return
   181		}
   182		r.headerSent = true
   183		fmt.Fprintf(r.bufw, "Status: %d %s\r\n", code, http.StatusText(code))
   184	
   185		// Set a default Content-Type
   186		if _, hasType := r.header["Content-Type"]; !hasType {
   187			r.header.Add("Content-Type", "text/html; charset=utf-8")
   188		}
   189	
   190		r.header.Write(r.bufw)
   191		r.bufw.WriteString("\r\n")
   192		r.bufw.Flush()
   193	}