mox/http/webserver.go
Mechiel Lukkien 6706c5c84a
add basic webserver that can do most of what i need
- serve static files, serving index.html or optionally listings for directories
- redirects
- reverse-proxy, forwarding requests to a backend

these are configurable through the config file. a domain and path regexp have to
be configured. path prefixes can be stripped.  configured domains are added to
the autotls allowlist, so acme automatically fetches certificates for them.

all webserver requests now have (access) logging, metrics, rate limiting.
on http errors, the error message prints an encrypted cid for relating with log files.

this also adds a new mechanism for example config files.
2023-02-28 22:19:24 +01:00

385 lines
11 KiB
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package http
import (
"fmt"
htmltemplate "html/template"
"io"
golog "log"
"net"
"net/http"
"net/http/httputil"
"os"
"path/filepath"
"sort"
"strings"
"time"
"github.com/mjl-/mox/config"
"github.com/mjl-/mox/dns"
"github.com/mjl-/mox/mlog"
"github.com/mjl-/mox/mox-"
"github.com/mjl-/mox/moxio"
)
// todo: automatic gzip on responses, if client supports it, and if content looks compressible.
// WebHandle serves an HTTP request by going through the list of WebHandlers,
// check if there is a domain+path match, and running the handler if so.
// WebHandle runs after the built-in handlers for mta-sts, autoconfig, etc.
// If no handler matched, false is returned.
// WebHandle sets w.Name to that of the matching handler.
func WebHandle(w *loggingWriter, r *http.Request) (handled bool) {
log := func() *mlog.Log {
return xlog.WithContext(r.Context())
}
host, _, err := net.SplitHostPort(r.Host)
if err != nil {
// Common, there often is not port.
host = r.Host
}
dom, err := dns.ParseDomain(host)
if err != nil {
log().Debugx("parsing http request domain", err, mlog.Field("host", host))
http.NotFound(w, r)
return true
}
for _, h := range mox.Conf.WebHandlers() {
if h.DNSDomain != dom {
continue
}
loc := h.Path.FindStringIndex(r.URL.Path)
if loc == nil {
continue
}
s := loc[0]
e := loc[1]
path := r.URL.Path[s:e]
if r.TLS == nil && !h.DontRedirectPlainHTTP {
u := *r.URL
u.Scheme = "https"
u.Host = host
w.Handler = h.Name
http.Redirect(w, r, u.String(), http.StatusPermanentRedirect)
return true
}
if h.WebStatic != nil && HandleStatic(h.WebStatic, w, r) {
w.Handler = h.Name
return true
}
if h.WebRedirect != nil && HandleRedirect(h.WebRedirect, w, r) {
w.Handler = h.Name
return true
}
if h.WebForward != nil && HandleForward(h.WebForward, w, r, path) {
w.Handler = h.Name
return true
}
}
return false
}
var lsTemplate = htmltemplate.Must(htmltemplate.New("ls").Parse(`<!doctype html>
<html>
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title>ls</title>
<style>
body, html { padding: 1em; font-size: 16px; }
* { font-size: inherit; font-family: ubuntu, lato, sans-serif; margin: 0; padding: 0; box-sizing: border-box; }
h1 { margin-bottom: 1ex; font-size: 1.2rem; }
table td, table th { padding: .2em .5em; }
table > tbody > tr:nth-child(odd) { background-color: #f8f8f8; }
[title] { text-decoration: underline; text-decoration-style: dotted; }
</style>
</head>
<body>
<h1>ls</h1>
<table>
<thead>
<tr>
<th>Size in MB</th>
<th>Modified (UTC)</th>
<th>Name</th>
</tr>
</thead>
<tbody>
{{ if not .Files }}
<tr><td colspan="3">No files.</td></tr>
{{ end }}
{{ range .Files }}
<tr>
<td title="{{ .Size }} bytes" style="text-align: right">{{ .SizeReadable }}{{ if .SizePad }}<span style="visibility:hidden">.</span>{{ end }}</td>
<td>{{ .Modified }}</td>
<td><a style="display: block" href="{{ .Name }}">{{ .Name }}</a></td>
</tr>
{{ end }}
</tbody>
</table>
</body>
</html>
`))
// HandleStatic serves static files. If a directory is requested and the URL
// path doesn't end with a slash, a response with a redirect to the URL path with trailing
// slash is written. If a directory is requested and an index.html exists, that
// file is returned. Otherwise, for directories with ListFiles configured, a
// directory listing is returned.
func HandleStatic(h *config.WebStatic, w http.ResponseWriter, r *http.Request) (handled bool) {
log := func() *mlog.Log {
return xlog.WithContext(r.Context())
}
recvid := func() string {
cid := mox.CidFromCtx(r.Context())
if cid <= 0 {
return ""
}
return " (requestid " + mox.ReceivedID(cid) + ")"
}
if r.Method != "GET" && r.Method != "HEAD" {
if h.ContinueNotFound {
// Give another handler that is presumbly configured, for the same path, a chance.
// E.g. an app that may generate this file for future requests to pick up.
return false
}
http.Error(w, "405 - method not allowed", http.StatusMethodNotAllowed)
return true
}
var fspath string
if h.StripPrefix != "" {
if !strings.HasPrefix(r.URL.Path, h.StripPrefix) {
if h.ContinueNotFound {
// We haven't handled this request, try a next WebHandler in the list.
return false
}
http.NotFound(w, r)
return true
}
fspath = filepath.Join(h.Root, strings.TrimPrefix(r.URL.Path, h.StripPrefix))
} else {
fspath = filepath.Join(h.Root, r.URL.Path)
}
f, err := os.Open(fspath)
if err != nil {
if os.IsNotExist(err) {
if h.ContinueNotFound {
// We haven't handled this request, try a next WebHandler in the list.
return false
}
http.NotFound(w, r)
return true
} else if os.IsPermission(err) {
http.Error(w, "403 - permission denied", http.StatusForbidden)
return true
}
log().Errorx("open file for static file serving", err, mlog.Field("url", r.URL), mlog.Field("fspath", fspath))
http.Error(w, "500 - internal server error"+recvid(), http.StatusInternalServerError)
return true
}
defer f.Close()
fi, err := f.Stat()
if err != nil {
log().Errorx("stat file for static file serving", err, mlog.Field("url", r.URL), mlog.Field("fspath", fspath))
http.Error(w, "500 - internal server error"+recvid(), http.StatusInternalServerError)
return true
}
if fi.IsDir() && !strings.HasSuffix(r.URL.Path, "/") {
http.Redirect(w, r, r.URL.Path+"/", http.StatusTemporaryRedirect)
return true
}
serveFile := func(name string, mtime time.Time, content *os.File) {
// ServeContent only sets a content-type if not already present in the response headers.
hdr := w.Header()
for k, v := range h.ResponseHeaders {
hdr.Add(k, v)
}
http.ServeContent(w, r, name, mtime, content)
}
if fi.IsDir() {
index, err := os.Open(filepath.Join(fspath, "index.html"))
if err != nil && os.IsPermission(err) || err != nil && os.IsNotExist(err) && !h.ListFiles {
http.Error(w, "403 - permission denied", http.StatusForbidden)
return true
} else if err == nil {
defer index.Close()
var ifi os.FileInfo
ifi, err = index.Stat()
if err == nil {
w.Header().Set("Content-Type", "text/html; charset=utf-8")
serveFile(filepath.Base(fspath), ifi.ModTime(), index)
return true
}
}
if !os.IsNotExist(err) {
log().Errorx("stat for static file serving", err, mlog.Field("url", r.URL), mlog.Field("fspath", fspath))
http.Error(w, "500 - internal server error"+recvid(), http.StatusInternalServerError)
return true
}
type File struct {
Name string
Size int64
SizeReadable string
SizePad bool // Whether the size needs padding because it has no decimal point.
Modified string
}
files := []File{}
if r.URL.Path != "/" {
files = append(files, File{"..", 0, "", false, ""})
}
for {
l, err := f.Readdir(1000)
for _, e := range l {
mb := float64(e.Size()) / (1024 * 1024)
var size string
var sizepad bool
if mb >= 10 {
size = fmt.Sprintf("%d", int64(mb))
sizepad = true
} else {
size = fmt.Sprintf("%.2f", mb)
}
const dateTime = "2006-01-02 15:04:05" // time.DateTime, but only since go1.20.
modified := e.ModTime().UTC().Format(dateTime)
f := File{e.Name(), e.Size(), size, sizepad, modified}
if e.IsDir() {
f.Name += "/"
}
files = append(files, f)
}
if err == io.EOF {
break
} else if err != nil {
log().Errorx("reading directory for file listing", err, mlog.Field("url", r.URL), mlog.Field("fspath", fspath))
http.Error(w, "500 - internal server error"+recvid(), http.StatusInternalServerError)
return true
}
}
sort.Slice(files, func(i, j int) bool {
return files[i].Name < files[j].Name
})
hdr := w.Header()
hdr.Set("Content-Type", "text/html; charset=utf-8")
for k, v := range h.ResponseHeaders {
if !strings.EqualFold(k, "content-type") {
hdr.Add(k, v)
}
}
err = lsTemplate.Execute(w, map[string]any{"Files": files})
if err != nil && !moxio.IsClosed(err) {
log().Errorx("executing directory listing template", err)
}
return true
}
serveFile(fspath, fi.ModTime(), f)
return true
}
// HandleRedirect writes a response with an HTTP redirect.
func HandleRedirect(h *config.WebRedirect, w http.ResponseWriter, r *http.Request) (handled bool) {
var dstpath string
if h.OrigPath == nil {
// No path rewrite necessary.
dstpath = r.URL.Path
} else if !h.OrigPath.MatchString(r.URL.Path) {
http.NotFound(w, r)
return true
} else {
dstpath = h.OrigPath.ReplaceAllString(r.URL.Path, h.ReplacePath)
}
u := *r.URL
u.Opaque = ""
u.RawPath = ""
u.OmitHost = false
if h.URL != nil {
u.Scheme = h.URL.Scheme
u.Host = h.URL.Host
u.ForceQuery = h.URL.ForceQuery
u.RawQuery = h.URL.RawQuery
u.Fragment = h.URL.Fragment
}
if r.URL.RawQuery != "" {
if u.RawQuery != "" {
u.RawQuery += "&"
}
u.RawQuery += r.URL.RawQuery
}
u.Path = dstpath
code := http.StatusPermanentRedirect
if h.StatusCode != 0 {
code = h.StatusCode
}
http.Redirect(w, r, u.String(), code)
return true
}
// HandleForward handles a request by forwarding it to another webserver and
// passing the response on. I.e. a reverse proxy.
func HandleForward(h *config.WebForward, w http.ResponseWriter, r *http.Request, path string) (handled bool) {
log := func() *mlog.Log {
return xlog.WithContext(r.Context())
}
recvid := func() string {
cid := mox.CidFromCtx(r.Context())
if cid <= 0 {
return ""
}
return " (requestid " + mox.ReceivedID(cid) + ")"
}
xr := *r
r = &xr
if h.StripPath {
u := *r.URL
u.Path = r.URL.Path[len(path):]
u.RawPath = ""
r.URL = &u
}
// Remove any forwarded headers passed in by client.
hdr := http.Header{}
for k, vl := range r.Header {
switch k {
case "Forwarded", "X-Forwarded-For", "X-Forwarded-Host", "X-Forwarded-Proto":
continue
}
hdr[k] = vl
}
r.Header = hdr
// Add our own X-Forwarded headers. ReverseProxy will add X-Forwarded-For.
r.Header["X-Forwarded-Host"] = []string{r.Host}
proto := "http"
if r.TLS != nil {
proto = "https"
}
r.Header["X-Forwarded-Proto"] = []string{proto}
// todo: add Forwarded header? is anyone using it?
// ReverseProxy will append any remaining path to the configured target URL.
proxy := httputil.NewSingleHostReverseProxy(h.TargetURL)
proxy.FlushInterval = time.Duration(-1) // Flush after each write.
proxy.ErrorLog = golog.New(mlog.ErrWriter(mlog.New("net/http/httputil").WithContext(r.Context()), mlog.LevelDebug, "reverseproxy error"), "", 0)
proxy.ErrorHandler = func(w http.ResponseWriter, r *http.Request, err error) {
log().Errorx("forwarding request to backend webserver", err, mlog.Field("url", r.URL))
http.Error(w, "502 - bad gateway"+recvid(), http.StatusBadGateway)
}
whdr := w.Header()
for k, v := range h.ResponseHeaders {
whdr.Add(k, v)
}
proxy.ServeHTTP(w, r)
return true
}