Subversion Repositories openrisc

// 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

        }

        defer cmd.Wait()

        defer stdoutRead.Close()

        linebody := bufio.NewReaderSize(stdoutRead, 1024)

        headers := make(http.Header)

        statusCode := 0

        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 {

                        break

                }

                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 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 {

                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)

        }

}

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

}