1// Package webmail implements a webmail client, serving html/js and providing an API for message actions and SSE endpoint for receiving real-time updates.

2package webmail

4// todo: should we be serving the messages/parts on a separate (sub)domain for user-content? to limit damage if the csp rules aren't enough.

6import (

7 "archive/zip"

8 "bytes"

9 "context"

10 "encoding/base64"

11 "encoding/json"

12 "errors"

13 "fmt"

14 "io"

15 "io/fs"

16 "log/slog"

17 "mime"

18 "net/http"

19 "os"

20 "path/filepath"

21 "regexp"

22 "runtime/debug"

23 "strconv"

24 "strings"

25 "time"

27 _ "embed"

29 "golang.org/x/net/html"

31 "github.com/prometheus/client_golang/prometheus"

32 "github.com/prometheus/client_golang/prometheus/promauto"

34 "github.com/mjl-/bstore"

35 "github.com/mjl-/sherpa"

37 "github.com/mjl-/mox/message"

38 "github.com/mjl-/mox/metrics"

39 "github.com/mjl-/mox/mlog"

40 "github.com/mjl-/mox/mox-"

41 "github.com/mjl-/mox/moxio"

42 "github.com/mjl-/mox/store"

43 "github.com/mjl-/mox/webauth"

44 "github.com/mjl-/mox/webops"

45)

47var pkglog = mlog.New("webmail", nil)

49type ctxKey string

51// We pass the request to the sherpa handler so the TLS info can be used for

52// the Received header in submitted messages. Most API calls need just the

53// account name.

54var requestInfoCtxKey ctxKey = "requestInfo"

56type requestInfo struct {

57 Log mlog.Log

58 LoginAddress string

59 Account *store.Account // Nil only for methods Login and LoginPrep.

60 SessionToken store.SessionToken

61 Response http.ResponseWriter

62 Request *http.Request // For Proto and TLS connection state during message submit.

63}

65//go:embed webmail.html

66var webmailHTML []byte

68//go:embed webmail.js

69var webmailJS []byte

71//go:embed msg.html

72var webmailmsgHTML []byte

74//go:embed msg.js

75var webmailmsgJS []byte

77//go:embed text.html

78var webmailtextHTML []byte

80//go:embed text.js

81var webmailtextJS []byte

83var (

84 // Similar between ../webmail/webmail.go:/metricSubmission and ../smtpserver/server.go:/metricSubmission and ../webapisrv/server.go:/metricSubmission

85 metricSubmission = promauto.NewCounterVec(

86 prometheus.CounterOpts{

87 Name: "mox_webmail_submission_total",

88 Help: "Webmail message submission results, known values (those ending with error are server errors): ok, badfrom, messagelimiterror, recipientlimiterror, queueerror, storesenterror.",

89 },

90 []string{

91 "result",

92 },

93 )

94 metricServerErrors = promauto.NewCounterVec(

95 prometheus.CounterOpts{

96 Name: "mox_webmail_errors_total",

97 Help: "Webmail server errors, known values: dkimsign, submit.",

98 },

99 []string{

100 "error",

101 },

102 )

103 metricSSEConnections = promauto.NewGauge(

104 prometheus.GaugeOpts{

105 Name: "mox_webmail_sse_connections",

106 Help: "Number of active webmail SSE connections.",

107 },

108 )

109)

110

111func xcheckf(ctx context.Context, err error, format string, args ...any) {

112 if err == nil {

113 return

114 }

115 msg := fmt.Sprintf(format, args...)

116 errmsg := fmt.Sprintf("%s: %s", msg, err)

117 pkglog.WithContext(ctx).Errorx(msg, err)

118 code := "server:error"

119 if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {

120 code = "user:error"

121 }

122 panic(&sherpa.Error{Code: code, Message: errmsg})

123}

124

125func xcheckuserf(ctx context.Context, err error, format string, args ...any) {

126 if err == nil {

127 return

128 }

129 msg := fmt.Sprintf(format, args...)

130 errmsg := fmt.Sprintf("%s: %s", msg, err)

131 pkglog.WithContext(ctx).Errorx(msg, err)

132 panic(&sherpa.Error{Code: "user:error", Message: errmsg})

133}

134

135func xdbwrite(ctx context.Context, acc *store.Account, fn func(tx *bstore.Tx)) {

136 err := acc.DB.Write(ctx, func(tx *bstore.Tx) error {

137 fn(tx)

138 return nil

139 })

140 xcheckf(ctx, err, "transaction")

141}

142

143func xdbread(ctx context.Context, acc *store.Account, fn func(tx *bstore.Tx)) {

144 err := acc.DB.Read(ctx, func(tx *bstore.Tx) error {

145 fn(tx)

146 return nil

147 })

148 xcheckf(ctx, err, "transaction")

149}

150

151var webmailFile = &mox.WebappFile{

152 HTML: webmailHTML,

153 JS: webmailJS,

154 HTMLPath: filepath.FromSlash("webmail/webmail.html"),

155 JSPath: filepath.FromSlash("webmail/webmail.js"),

156 CustomStem: "webmail",

157}

158

159func customization() (css, js []byte, err error) {

160 if css, err = os.ReadFile(mox.ConfigDirPath("webmail.css")); err != nil && !errors.Is(err, fs.ErrNotExist) {

161 return nil, nil, err

162 }

163 if js, err = os.ReadFile(mox.ConfigDirPath("webmail.js")); err != nil && !errors.Is(err, fs.ErrNotExist) {

164 return nil, nil, err

165 }

166 css = append([]byte("/* Custom CSS by admin from $configdir/webmail.css: */\n"), css...)

167 js = append([]byte("// Custom JS by admin from $configdir/webmail.js:\n"), js...)

168 js = append(js, '\n')

169 return css, js, nil

170}

171

172// Serve HTML content, either from a file, or return the fallback data. If

173// customize is set, css/js is inserted if configured. Caller should already have

174// set the content-type. We use this to return a file from the local file system

175// (during development), or embedded in the binary (when deployed).

176func serveContentFallback(log mlog.Log, w http.ResponseWriter, r *http.Request, path string, fallback []byte, customize bool) {

177 serve := func(mtime time.Time, rd io.ReadSeeker) {

178 if customize {

179 buf, err := io.ReadAll(rd)

180 if err != nil {

181 log.Errorx("reading content to customize", err)

182 http.Error(w, "500 - internal server error - reading content to customize", http.StatusInternalServerError)

183 return

184 }

185 customCSS, customJS, err := customization()

186 if err != nil {

187 log.Errorx("reading customizations", err)

188 http.Error(w, "500 - internal server error - reading customizations", http.StatusInternalServerError)

189 return

190 }

191 buf = bytes.Replace(buf, []byte("/* css placeholder */"), customCSS, 1)

192 buf = bytes.Replace(buf, []byte("/* js placeholder */"), customJS, 1)

193 rd = bytes.NewReader(buf)

194 }

195 http.ServeContent(w, r, "", mtime, rd)

196 }

197

198 f, err := os.Open(path)

199 if err == nil {

200 defer f.Close()

201 st, err := f.Stat()

202 if err == nil {

203 serve(st.ModTime(), f)

204 return

205 }

206 }

207 serve(mox.FallbackMtime(log), bytes.NewReader(fallback))

208}

209

210func init() {

211 mox.NewWebmailHandler = func(maxMsgSize int64, basePath string, isForwarded bool, accountPath string) http.Handler {

212 return http.HandlerFunc(Handler(maxMsgSize, basePath, isForwarded, accountPath))

213 }

214}

215

216// Handler returns a handler for the webmail endpoints, customized for the max

217// message size coming from the listener and cookiePath.

218func Handler(maxMessageSize int64, cookiePath string, isForwarded bool, accountPath string) func(w http.ResponseWriter, r *http.Request) {

219 sh, err := makeSherpaHandler(maxMessageSize, cookiePath, isForwarded)

220 return func(w http.ResponseWriter, r *http.Request) {

221 if err != nil {

222 http.Error(w, "500 - internal server error - cannot handle requests", http.StatusInternalServerError)

223 return

224 }

225 handle(sh, isForwarded, accountPath, w, r)

226 }

227}

228

229func handle(apiHandler http.Handler, isForwarded bool, accountPath string, w http.ResponseWriter, r *http.Request) {

230 ctx := r.Context()

231 log := pkglog.WithContext(ctx).With(slog.String("userauth", ""))

232

233 // Server-sent event connection, for all initial data (list of mailboxes), list of

234 // messages, and all events afterwards. Authenticated through a single use token in

235 // the query string, which it got from a Token API call.

236 if r.URL.Path == "/events" {

237 serveEvents(ctx, log, accountPath, w, r)

238 return

239 }

240

241 defer func() {

242 x := recover()

243 if x == nil {

244 return

245 }

246 err, ok := x.(*sherpa.Error)

247 if !ok {

248 log.WithContext(ctx).Error("handle panic", slog.Any("err", x))

249 debug.PrintStack()

250 metrics.PanicInc(metrics.Webmailhandle)

251 panic(x)

252 }

253 if strings.HasPrefix(err.Code, "user:") {

254 log.Debugx("webmail user error", err)

255 http.Error(w, "400 - bad request - "+err.Message, http.StatusBadRequest)

256 } else {

257 log.Errorx("webmail server error", err)

258 http.Error(w, "500 - internal server error - "+err.Message, http.StatusInternalServerError)

259 }

260 }()

261

262 switch r.URL.Path {

263 case "/":

264 switch r.Method {

265 case "GET", "HEAD":

266 h := w.Header()

267 h.Set("X-Frame-Options", "deny")

268 h.Set("Referrer-Policy", "same-origin")

269 webmailFile.Serve(ctx, log, w, r)

270 default:

271 http.Error(w, "405 - method not allowed - use get", http.StatusMethodNotAllowed)

272 }

273 return

274

275 case "/licenses.txt":

276 switch r.Method {

277 case "GET", "HEAD":

278 h := w.Header()

279 h.Set("Content-Type", "text/plain; charset=utf-8")

280 mox.LicensesWrite(w)

281 default:

282 http.Error(w, "405 - method not allowed - use get", http.StatusMethodNotAllowed)

283 }

284 return

285

286 case "/msg.js", "/text.js":

287 switch r.Method {

288 default:

289 http.Error(w, "405 - method not allowed - use get", http.StatusMethodNotAllowed)

290 return

291 case "GET", "HEAD":

292 }

293

294 path := filepath.Join("webmail", r.URL.Path[1:])

295 var fallback = webmailmsgJS

296 if r.URL.Path == "/text.js" {

297 fallback = webmailtextJS

298 }

299

300 w.Header().Set("Content-Type", "application/javascript; charset=utf-8")

301 serveContentFallback(log, w, r, path, fallback, false)

302 return

303 }

304

305 isAPI := strings.HasPrefix(r.URL.Path, "/api/")

306 // Only allow POST for calls, they will not work cross-domain without CORS.

307 if isAPI && r.URL.Path != "/api/" && r.Method != "POST" {

308 http.Error(w, "405 - method not allowed - use post", http.StatusMethodNotAllowed)

309 return

310 }

311

312 var loginAddress, accName string

313 var sessionToken store.SessionToken

314 // All other URLs, except the login endpoint require some authentication.

315 if r.URL.Path != "/api/LoginPrep" && r.URL.Path != "/api/Login" {

316 var ok bool

317 isExport := r.URL.Path == "/export"

318 requireCSRF := isAPI || isExport

319 accName, sessionToken, loginAddress, ok = webauth.Check(ctx, log, webauth.Accounts, "webmail", isForwarded, w, r, isAPI, requireCSRF, isExport)

320 if !ok {

321 // Response has been written already.

322 return

323 }

324 }

325

326 if isAPI {

327 var acc *store.Account

328 if accName != "" {

329 log = log.With(slog.String("account", accName))

330 var err error

331 acc, err = store.OpenAccount(log, accName)

332 if err != nil {

333 log.Errorx("open account", err)

334 http.Error(w, "500 - internal server error - error opening account", http.StatusInternalServerError)

335 return

336 }

337 defer func() {

338 err := acc.Close()

339 log.Check(err, "closing account")

340 }()

341 }

342 reqInfo := requestInfo{log, loginAddress, acc, sessionToken, w, r}

343 ctx = context.WithValue(ctx, requestInfoCtxKey, reqInfo)

344 apiHandler.ServeHTTP(w, r.WithContext(ctx))

345 return

346 }

347

348 // We are now expecting the following URLs:

349 // .../export

350 // .../msg/<msgid>/{attachments.zip,parsedmessage.js,raw}

351 // .../msg/<msgid>/{,msg}{text,html,htmlexternal}

352 // .../msg/<msgid>/{view,viewtext,download}/<partid>

353

354 if r.URL.Path == "/export" {

355 webops.Export(log, accName, w, r)

356 return

357 }

358

359 if !strings.HasPrefix(r.URL.Path, "/msg/") {

360 http.NotFound(w, r)

361 return

362 }

363

364 t := strings.Split(r.URL.Path[len("/msg/"):], "/")

365 if len(t) < 2 {

366 http.NotFound(w, r)

367 return

368 }

369

370 id, err := strconv.ParseInt(t[0], 10, 64)

371 if err != nil || id == 0 {

372 http.NotFound(w, r)

373 return

374 }

375

376 // Many of the requests need either a message or a parsed part. Make it easy to

377 // fetch/prepare and cleanup. We only do all the work when the request seems legit

378 // (valid HTTP route and method).

379 xprepare := func() (acc *store.Account, moreHeaders []string, m store.Message, msgr *store.MsgReader, p message.Part, cleanup func(), ok bool) {

380 if r.Method != "GET" {

381 http.Error(w, "405 - method not allowed - post required", http.StatusMethodNotAllowed)

382 return

383 }

384

385 defer func() {

386 if ok {

387 return

388 }

389 if msgr != nil {

390 err := msgr.Close()

391 log.Check(err, "closing message reader")

392 msgr = nil

393 }

394 if acc != nil {

395 err := acc.Close()

396 log.Check(err, "closing account")

397 acc = nil

398 }

399 }()

400

401 var err error

402

403 acc, err = store.OpenAccount(log, accName)

404 xcheckf(ctx, err, "open account")

405

406 m = store.Message{ID: id}

407 err = acc.DB.Read(ctx, func(tx *bstore.Tx) error {

408 if err := tx.Get(&m); err != nil {

409 return err

410 }

411 s := store.Settings{ID: 1}

412 if err := tx.Get(&s); err != nil {

413 return fmt.Errorf("get settings for more headers: %v", err)

414 }

415 moreHeaders = s.ShowHeaders

416 return nil

417 })

418 if err == bstore.ErrAbsent || err == nil && m.Expunged {

419 http.NotFound(w, r)

420 return

421 }

422 xcheckf(ctx, err, "get message")

423

424 msgr = acc.MessageReader(m)

425

426 p, err = m.LoadPart(msgr)

427 xcheckf(ctx, err, "load parsed message")

428

429 cleanup = func() {

430 err := msgr.Close()

431 log.Check(err, "closing message reader")

432 err = acc.Close()

433 log.Check(err, "closing account")

434 }

435 ok = true

436 return

437 }

438

439 h := w.Header()

440

441 // We set a Content-Security-Policy header that is as strict as possible, depending

442 // on the type of message/part/html/js. We have to be careful because we are

443 // returning data that is coming in from external places. E.g. HTML could contain

444 // javascripts that we don't want to execute, especially not on our domain. We load

445 // resources in an iframe. The CSP policy starts out with default-src 'none' to

446 // disallow loading anything, then start allowing what is safe, such as inlined

447 // datauri images and inline styles. Data can only be loaded when the request is

448 // coming from the same origin (so other sites cannot include resources

449 // (messages/parts)).

450 //

451 // We want to load resources in sandbox-mode, causing the page to be loaded as from

452 // a different origin. If sameOrigin is set, we have a looser CSP policy:

453 // allow-same-origin is set so resources are loaded as coming from this same

454 // origin. This is needed for the msg* endpoints that render a message, where we

455 // load the message body in a separate iframe again (with stricter CSP again),

456 // which we need to access for its inner height. If allowSelfScript is also set

457 // (for "msgtext"), the CSP leaves out the sandbox entirely.

458 //

459 // If allowExternal is set, we allow loading image, media (audio/video), styles and

460 // fronts from external URLs as well as inline URI's. By default we don't allow any

461 // loading of content, except inlined images (we do that ourselves for images

462 // embedded in the email), and we allow inline styles (which are safely constrained

463 // to an iframe).

464 //

465 // If allowSelfScript is set, inline scripts and scripts from our origin are

466 // allowed. Used to display a message including header. The header is rendered with

467 // javascript, the content is rendered in a separate iframe with a CSP that doesn't

468 // have allowSelfScript.

469 headers := func(sameOrigin, allowExternal, allowSelfScript, allowSelfImg bool) {

470 // allow-popups is needed to make opening links in new tabs work.

471 sb := "sandbox allow-popups allow-popups-to-escape-sandbox; "

472 if sameOrigin && allowSelfScript {

473 // Sandbox with both allow-same-origin and allow-script would not provide security,

474 // and would give warning in console about that.

475 sb = ""

476 } else if sameOrigin {

477 sb = "sandbox allow-popups allow-popups-to-escape-sandbox allow-same-origin; "

478 }

479 script := ""

480 if allowSelfScript {

481 script = "; script-src 'unsafe-inline' 'self'; frame-src 'self'; connect-src 'self'"

482 }

483 var csp string

484 if allowExternal {

485 csp = sb + "frame-ancestors 'self'; default-src 'none'; img-src data: http: https: 'unsafe-inline'; style-src 'unsafe-inline' data: http: https:; font-src data: http: https: 'unsafe-inline'; media-src 'unsafe-inline' data: http: https:" + script

486 } else if allowSelfImg {

487 csp = sb + "frame-ancestors 'self'; default-src 'none'; img-src data: 'self'; style-src 'unsafe-inline'" + script

488 } else {

489 csp = sb + "frame-ancestors 'self'; default-src 'none'; img-src data:; style-src 'unsafe-inline'" + script

490 }

491 h.Set("Content-Security-Policy", csp)

492 h.Set("X-Frame-Options", "sameorigin") // Duplicate with CSP, but better too much than too little.

493 h.Set("X-Content-Type-Options", "nosniff")

494 h.Set("Referrer-Policy", "no-referrer")

495 }

496

497 switch {

498 case len(t) == 2 && t[1] == "attachments.zip":

499 acc, _, m, msgr, p, cleanup, ok := xprepare()

500 if !ok {

501 return

502 }

503 defer cleanup()

504 state := msgState{acc: acc, m: m, msgr: msgr, part: &p}

505 // note: state is cleared by cleanup

506

507 mi, err := messageItem(log, m, &state, nil)

508 xcheckf(ctx, err, "parsing message")

509

510 headers(false, false, false, false)

511 h.Set("Content-Type", "application/zip")

512 h.Set("Cache-Control", "no-store, max-age=0")

513 var subjectSlug string

514 if p.Envelope != nil {

515 s := p.Envelope.Subject

516 s = strings.ToLower(s)

517 s = regexp.MustCompile("[^a-z0-9_.-]").ReplaceAllString(s, "-")

518 s = regexp.MustCompile("--*").ReplaceAllString(s, "-")

519 s = strings.TrimLeft(s, "-")

520 s = strings.TrimRight(s, "-")

521 if s != "" {

522 s = "-" + s

523 }

524 subjectSlug = s

525 }

526 filename := fmt.Sprintf("email-%d-attachments-%s%s.zip", m.ID, m.Received.Format("20060102-150405"), subjectSlug)

527 cd := mime.FormatMediaType("attachment", map[string]string{"filename": filename})

528 h.Set("Content-Disposition", cd)

529

530 zw := zip.NewWriter(w)

531 names := map[string]bool{}

532 for _, a := range mi.Attachments {

533 ap := a.Part

534 _, name, err := ap.DispositionFilename()

535 if err != nil && errors.Is(err, message.ErrParamEncoding) {

536 log.Debugx("parsing disposition header for filename", err)

537 } else {

538 xcheckf(ctx, err, "reading disposition header")

539 }

540 if name != "" {

541 name = filepath.Base(name)

542 }

543 mt := strings.ToLower(ap.MediaType + "/" + ap.MediaSubType)

544 if name == "" || names[name] {

545 ext := filepath.Ext(name)

546 if ext == "" {

547 // Handle just a few basic types.

548 extensions := map[string]string{

549 "text/plain": ".txt",

550 "text/html": ".html",

551 "image/jpeg": ".jpg",

552 "image/png": ".png",

553 "image/gif": ".gif",

554 "application/zip": ".zip",

555 }

556 ext = extensions[mt]

557 if ext == "" {

558 ext = ".bin"

559 }

560 }

561 var stem string

562 if name != "" && strings.HasSuffix(name, ext) {

563 stem = strings.TrimSuffix(name, ext)

564 } else {

565 stem = "attachment"

566 for _, index := range a.Path {

567 stem += fmt.Sprintf("-%d", index)

568 }

569 }

570 name = stem + ext

571 seq := 0

572 for names[name] {

573 seq++

574 name = stem + fmt.Sprintf("-%d", seq) + ext

575 }

576 }

577 names[name] = true

578

579 fh := zip.FileHeader{

580 Name: name,

581 Modified: m.Received,

582 }

583 nodeflate := map[string]bool{

584 "application/x-bzip2": true,

585 "application/zip": true,

586 "application/x-zip-compressed": true,

587 "application/gzip": true,

588 "application/x-gzip": true,

589 "application/vnd.rar": true,

590 "application/x-rar-compressed": true,

591 "application/x-7z-compressed": true,

592 }

593 // Sniff content-type as well for compressed data.

594 buf := make([]byte, 512)

595 n, _ := io.ReadFull(ap.Reader(), buf)

596 var sniffmt string

597 if n > 0 {

598 sniffmt = strings.ToLower(http.DetectContentType(buf[:n]))

599 }

600 deflate := ap.MediaType != "VIDEO" && ap.MediaType != "AUDIO" && (ap.MediaType != "IMAGE" || ap.MediaSubType == "BMP") && !nodeflate[mt] && !nodeflate[sniffmt]

601 if deflate {

602 fh.Method = zip.Deflate

603 }

604 // We cannot return errors anymore: we have already sent an application/zip header.

605 if zf, err := zw.CreateHeader(&fh); err != nil {

606 log.Check(err, "adding to zip file")

607 return

608 } else if _, err := io.Copy(zf, ap.Reader()); err != nil {

609 log.Check(err, "writing to zip file")

610 return

611 }

612 }

613 err = zw.Close()

614 log.Check(err, "final write to zip file")

615

616 // Raw display of a message, as text/plain.

617 case len(t) == 2 && t[1] == "raw":

618 _, _, _, msgr, p, cleanup, ok := xprepare()

619 if !ok {

620 return

621 }

622 defer cleanup()

623

624 // We intentially use text/plain. We certainly don't want to return a format that

625 // browsers or users would think of executing. We do set the charset if available

626 // on the outer part. If present, we assume it may be relevant for other parts. If

627 // not, there is not much we could do better...

628 headers(false, false, false, false)

629 ct := "text/plain"

630 params := map[string]string{}

631 if charset := p.ContentTypeParams["charset"]; charset != "" {

632 params["charset"] = charset

633 }

634 h.Set("Content-Type", mime.FormatMediaType(ct, params))

635 h.Set("Cache-Control", "no-store, max-age=0")

636

637 _, err := io.Copy(w, &moxio.AtReader{R: msgr})

638 log.Check(err, "writing raw")

639

640 case len(t) == 2 && (t[1] == "msgtext" || t[1] == "msghtml" || t[1] == "msghtmlexternal"):

641 // msg.html has a javascript tag with message data, and javascript to render the

642 // message header like the regular webmail.html and to load the message body in a

643 // separate iframe with a separate request with stronger CSP.

644 acc, _, m, msgr, p, cleanup, ok := xprepare()

645 if !ok {

646 return

647 }

648 defer cleanup()

649

650 state := msgState{acc: acc, m: m, msgr: msgr, part: &p}

651 // note: state is cleared by cleanup

652

653 pm, err := parsedMessage(log, m, &state, true, true, true)

654 xcheckf(ctx, err, "getting parsed message")

655 if t[1] == "msgtext" && len(pm.Texts) == 0 || t[1] != "msgtext" && !pm.HasHTML {

656 http.Error(w, "400 - bad request - no such part", http.StatusBadRequest)

657 return

658 }

659

660 sameorigin := true

661 loadExternal := t[1] == "msghtmlexternal"

662 allowSelfScript := true

663 headers(sameorigin, loadExternal, allowSelfScript, false)

664 h.Set("Content-Type", "text/html; charset=utf-8")

665 h.Set("Cache-Control", "no-store, max-age=0")

666

667 path := filepath.FromSlash("webmail/msg.html")

668 fallback := webmailmsgHTML

669 serveContentFallback(log, w, r, path, fallback, true)

670

671 case len(t) == 2 && t[1] == "parsedmessage.js":

672 // Used by msg.html, for the msg* endpoints, for the data needed to show all data

673 // except the message body.

674 // This is js with data inside instead so we can load it synchronously, which we do

675 // to get a "loaded" event after the page was actually loaded.

676

677 acc, moreHeaders, m, msgr, p, cleanup, ok := xprepare()

678 if !ok {

679 return

680 }

681 defer cleanup()

682 state := msgState{acc: acc, m: m, msgr: msgr, part: &p}

683 // note: state is cleared by cleanup

684

685 pm, err := parsedMessage(log, m, &state, true, true, true)

686 xcheckf(ctx, err, "parsing parsedmessage")

687 pmjson, err := json.Marshal(pm)

688 xcheckf(ctx, err, "marshal parsedmessage")

689

690 m.MsgPrefix = nil

691 m.ParsedBuf = nil

692 hl := messageItemMoreHeaders(moreHeaders, pm)

693 mi := MessageItem{m, pm.envelope, pm.attachments, pm.isSigned, pm.isEncrypted, pm.firstLine, false, hl}

694 mijson, err := json.Marshal(mi)

695 xcheckf(ctx, err, "marshal messageitem")

696

697 headers(false, false, false, false)

698 h.Set("Content-Type", "application/javascript; charset=utf-8")

699 h.Set("Cache-Control", "no-store, max-age=0")

700

701 _, err = fmt.Fprintf(w, "window.messageItem = %s;\nwindow.parsedMessage = %s;\n", mijson, pmjson)

702 log.Check(err, "writing parsedmessage.js")

703

704 case len(t) == 2 && t[1] == "text":

705 // Returns text.html whichs loads the message data with a javascript tag and

706 // renders just the text content with the same code as webmail.html. Used by the

707 // iframe in the msgtext endpoint. Not used by the regular webmail viewer, it

708 // renders the text itself, with the same shared js code.

709 acc, _, m, msgr, p, cleanup, ok := xprepare()

710 if !ok {

711 return

712 }

713 defer cleanup()

714

715 state := msgState{acc: acc, m: m, msgr: msgr, part: &p}

716 // note: state is cleared by cleanup

717

718 pm, err := parsedMessage(log, m, &state, true, true, true)

719 xcheckf(ctx, err, "parsing parsedmessage")

720

721 if len(pm.Texts) == 0 {

722 http.Error(w, "400 - bad request - no text part in message", http.StatusBadRequest)

723 return

724 }

725

726 // Needed for inner document height for outer iframe height in separate message view.

727 sameorigin := true

728 allowSelfScript := true

729 allowSelfImg := true

730 headers(sameorigin, false, allowSelfScript, allowSelfImg)

731 h.Set("Content-Type", "text/html; charset=utf-8")

732 h.Set("Cache-Control", "no-store, max-age=0")

733

734 // We typically return the embedded file, but during development it's handy to load

735 // from disk.

736 path := filepath.FromSlash("webmail/text.html")

737 fallback := webmailtextHTML

738 serveContentFallback(log, w, r, path, fallback, true)

739

740 case len(t) == 2 && (t[1] == "html" || t[1] == "htmlexternal"):

741 // Returns the first HTML part, with "cid:" URIs replaced with an inlined datauri

742 // if the referenced Content-ID attachment can be found.

743 _, _, _, _, p, cleanup, ok := xprepare()

744 if !ok {

745 return

746 }

747 defer cleanup()

748

749 setHeaders := func() {

750 // Needed for inner document height for outer iframe height in separate message

751 // view. We only need that when displaying as a separate message on the msghtml*

752 // endpoints. When displaying in the regular webmail, we don't need to know the

753 // inner height so we load it as different origin, which should be safer.

754 sameorigin := r.URL.Query().Get("sameorigin") == "true"

755 allowExternal := strings.HasSuffix(t[1], "external")

756 headers(sameorigin, allowExternal, false, false)

757

758 h.Set("Content-Type", "text/html; charset=utf-8")

759 h.Set("Cache-Control", "no-store, max-age=0")

760 }

761

762 // todo: skip certain html parts? e.g. with content-disposition: attachment?

763 var done bool

764 var usePart func(p *message.Part, parents []*message.Part)

765 usePart = func(p *message.Part, parents []*message.Part) {

766 if done {

767 return

768 }

769 mt := p.MediaType + "/" + p.MediaSubType

770 switch mt {

771 case "TEXT/HTML":

772 done = true

773 err := inlineSanitizeHTML(log, setHeaders, w, p, parents)

774 if err != nil {

775 http.Error(w, "400 - bad request - "+err.Error(), http.StatusBadRequest)

776 }

777 return

778 }

779 parents = append(parents, p)

780 for _, sp := range p.Parts {

781 usePart(&sp, parents)

782 }

783 }

784 usePart(&p, nil)

785

786 if !done {

787 http.Error(w, "400 - bad request - no html part in message", http.StatusBadRequest)

788 }

789

790 case len(t) == 3 && (t[1] == "view" || t[1] == "viewtext" || t[1] == "download"):

791 // View any part, as referenced in the last element path. "0" is the whole message,

792 // 0.0 is the first subpart, etc. "view" returns it with the content-type from the

793 // message (could be dangerous, but we set strict CSP headers), "viewtext" returns

794 // data with a text/plain content-type so the browser will attempt to display it,

795 // and "download" adds a content-disposition header causing the browser the

796 // download the file.

797 _, _, _, _, p, cleanup, ok := xprepare()

798 if !ok {

799 return

800 }

801 defer cleanup()

802

803 paths := strings.Split(t[2], ".")

804 if len(paths) == 0 || paths[0] != "0" {

805 http.NotFound(w, r)

806 return

807 }

808 ap := p

809 for _, e := range paths[1:] {

810 index, err := strconv.ParseInt(e, 10, 32)

811 if err != nil || index < 0 || int(index) >= len(ap.Parts) {

812 http.NotFound(w, r)

813 return

814 }

815 ap = ap.Parts[int(index)]

816 }

817

818 headers(false, false, false, false)

819 var ct string

820 if t[1] == "viewtext" {

821 ct = "text/plain"

822 } else {

823 ct = strings.ToLower(ap.MediaType + "/" + ap.MediaSubType)

824 }

825 h.Set("Content-Type", ct)

826 h.Set("Cache-Control", "no-store, max-age=0")

827 if t[1] == "download" {

828 _, name, err := ap.DispositionFilename()

829 if err != nil && errors.Is(err, message.ErrParamEncoding) {

830 log.Debugx("parsing disposition/filename", err)

831 } else {

832 xcheckf(ctx, err, "reading disposition/filename")

833 }

834 if name == "" {

835 name = "attachment.bin"

836 }

837 cd := mime.FormatMediaType("attachment", map[string]string{"filename": name})

838 h.Set("Content-Disposition", cd)

839 }

840

841 _, err := io.Copy(w, ap.Reader())

842 if err != nil && !moxio.IsClosed(err) {

843 log.Errorx("copying attachment", err)

844 }

845 default:

846 http.NotFound(w, r)

847 }

848}

849

850// inlineSanitizeHTML writes the part as HTML, with "cid:" URIs for html "src"

851// attributes inlined and with potentially dangerous tags removed (javascript). The

852// sanitizing is just a first layer of defense, CSP headers block execution of

853// scripts. If the HTML becomes too large, an error is returned. Before writing

854// HTML, setHeaders is called to write the required headers for content-type and

855// CSP. On error, setHeader is not called, no output is written and the caller

856// should write an error response.

857func inlineSanitizeHTML(log mlog.Log, setHeaders func(), w io.Writer, p *message.Part, parents []*message.Part) error {

858 // Prepare cids if there is a chance we will use them.

859 cids := map[string]*message.Part{}

860 for _, parent := range parents {

861 if parent.MediaType+"/"+parent.MediaSubType == "MULTIPART/RELATED" && p.DecodedSize < 2*1024*1024 {

862 for i, rp := range parent.Parts {

863 if rp.ContentID != "" {

864 cids[strings.ToLower(rp.ContentID)] = &parent.Parts[i]

865 }

866 }

867 }

868 }

869

870 node, err := html.Parse(p.ReaderUTF8OrBinary())

871 if err != nil {

872 return fmt.Errorf("parsing html: %v", err)

873 }

874

875 // We track size, if it becomes too much, we abort and still copy as regular html.

876 var totalSize int64

877 if err := inlineNode(node, cids, &totalSize); err != nil {

878 return fmt.Errorf("inline cid uris in html nodes: %w", err)

879 }

880 sanitizeNode(node)

881 setHeaders()

882 err = html.Render(w, node)

883 log.Check(err, "writing html")

884 return nil

885}

886

887// We inline cid: URIs into data: URIs. If a cid is missing in the

888// multipart/related, we ignore the error and continue with other HTML nodes. It

889// will probably just result in a "broken image". We limit the max size we

890// generate. We only replace "src" attributes that start with "cid:". A cid URI

891// could theoretically occur in many more places, like link href, and css url().

892// That's probably not common though. Let's wait for someone to need it.

893func inlineNode(node *html.Node, cids map[string]*message.Part, totalSize *int64) error {

894 for i, a := range node.Attr {

895 if a.Key != "src" || !caselessPrefix(a.Val, "cid:") || a.Namespace != "" {

896 continue

897 }

898 cid := a.Val[4:]

899 ap := cids["<"+strings.ToLower(cid)+">"]

900 if ap == nil {

901 // Missing cid, can happen with email, no need to stop returning data.

902 continue

903 }

904 *totalSize += ap.DecodedSize

905 if *totalSize >= 10*1024*1024 {

906 return fmt.Errorf("html too large")

907 }

908 var sb strings.Builder

909 if _, err := fmt.Fprintf(&sb, "data:%s;base64,", strings.ToLower(ap.MediaType+"/"+ap.MediaSubType)); err != nil {

910 return fmt.Errorf("writing datauri: %v", err)

911 }

912 w := base64.NewEncoder(base64.StdEncoding, &sb)

913 if _, err := io.Copy(w, ap.Reader()); err != nil {

914 return fmt.Errorf("writing base64 datauri: %v", err)

915 }

916 node.Attr[i].Val = sb.String()

917 }

918 for node = node.FirstChild; node != nil; node = node.NextSibling {

919 if err := inlineNode(node, cids, totalSize); err != nil {

920 return err

921 }

922 }

923 return nil

924}

925

926func caselessPrefix(k, pre string) bool {

927 return len(k) >= len(pre) && strings.EqualFold(k[:len(pre)], pre)

928}

929

930var targetable = map[string]bool{

931 "a": true,

932 "area": true,

933 "form": true,

934 "base": true,

935}

936

937// sanitizeNode removes script elements, on* attributes, javascript: href

938// attributes, adds target="_blank" to all links and to a base tag.

939func sanitizeNode(node *html.Node) {

940 i := 0

941 var haveTarget, haveRel bool

942 for i < len(node.Attr) {

943 a := node.Attr[i]

944 // Remove dangerous attributes.

945 if strings.HasPrefix(a.Key, "on") || a.Key == "href" && caselessPrefix(a.Val, "javascript:") || a.Key == "src" && caselessPrefix(a.Val, "data:text/html") {

946 copy(node.Attr[i:], node.Attr[i+1:])

947 node.Attr = node.Attr[:len(node.Attr)-1]

948 continue

949 }

950 if a.Key == "target" {

951 node.Attr[i].Val = "_blank"

952 haveTarget = true

953 }

954 if a.Key == "rel" && targetable[node.Data] {

955 node.Attr[i].Val = "noopener noreferrer"

956 haveRel = true

957 }

958 i++

959 }

960 // Ensure target attribute is set for elements that can have it.

961 if !haveTarget && node.Type == html.ElementNode && targetable[node.Data] {

962 node.Attr = append(node.Attr, html.Attribute{Key: "target", Val: "_blank"})

963 haveTarget = true

964 }

965 if haveTarget && !haveRel {

966 node.Attr = append(node.Attr, html.Attribute{Key: "rel", Val: "noopener noreferrer"})

967 }

968

969 parent := node

970 node = node.FirstChild

971 var haveBase bool

972 for node != nil {

973 // Set next now, we may remove cur, which clears its NextSibling.

974 cur := node

975 node = node.NextSibling

976

977 // Remove script elements.

978 if cur.Type == html.ElementNode && cur.Data == "script" {

979 parent.RemoveChild(cur)

980 continue

981 }

982 sanitizeNode(cur)

983 }

984 if parent.Type == html.ElementNode && parent.Data == "head" && !haveBase {

985 n := html.Node{Type: html.ElementNode, Data: "base", Attr: []html.Attribute{{Key: "target", Val: "_blank"}, {Key: "rel", Val: "noopener noreferrer"}}}

986 parent.AppendChild(&n)

987 }

988}

989