1package smtpclient

3import (

4 "bufio"

5 "context"

6 "crypto/ed25519"

7 cryptorand "crypto/rand"

8 "crypto/sha1"

9 "crypto/sha256"

10 "crypto/tls"

11 "crypto/x509"

12 "encoding/base64"

13 "errors"

14 "fmt"

15 "hash"

16 "io"

17 "log/slog"

18 "math/big"

19 "net"

20 "reflect"

21 "strings"

22 "testing"

23 "time"

25 "github.com/mjl-/mox/dns"

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

27 "github.com/mjl-/mox/sasl"

28 "github.com/mjl-/mox/scram"

29 "github.com/mjl-/mox/smtp"

30)

32var zerohost dns.Domain

33var localhost = dns.Domain{ASCII: "localhost"}

35func TestClient(t *testing.T) {

36 ctx := context.Background()

37 log := mlog.New("smtpclient", nil)

39 mlog.SetConfig(map[string]slog.Level{"": mlog.LevelTrace})

40 defer mlog.SetConfig(map[string]slog.Level{"": mlog.LevelDebug})

42 type options struct {

43 // Server behaviour.

44 pipelining bool

45 ecodes bool

46 maxSize int

47 starttls bool

48 eightbitmime bool

49 smtputf8 bool

50 requiretls bool

51 ehlo bool

52 auths []string // Allowed mechanisms.

54 nodeliver bool // For server, whether client will attempt a delivery.

56 // Client behaviour.

57 tlsMode TLSMode

58 tlsPKIX bool

59 roots *x509.CertPool

60 tlsHostname dns.Domain

61 need8bitmime bool

62 needsmtputf8 bool

63 needsrequiretls bool

64 recipients []string // If nil, mjl@mox.example is used.

65 resps []Response // Checked only if non-nil.

66 }

68 // Make fake cert, and make it trusted.

69 cert := fakeCert(t, false)

70 roots := x509.NewCertPool()

71 roots.AddCert(cert.Leaf)

72 tlsConfig := tls.Config{

73 Certificates: []tls.Certificate{cert},

74 }

76 cleanupResp := func(resps []Response) []Response {

77 for i, r := range resps {

78 resps[i] = Response{Code: r.Code, Secode: r.Secode}

79 }

80 return resps

81 }

83 test := func(msg string, opts options, auth func(l []string, cs *tls.ConnectionState) (sasl.Client, error), expClientErr, expDeliverErr, expServerErr error) {

84 t.Helper()

86 if opts.tlsMode == "" {

87 opts.tlsMode = TLSOpportunistic

88 }

90 clientConn, serverConn := net.Pipe()

91 defer serverConn.Close()

93 result := make(chan error, 2)

95 go func() {

96 defer func() {

97 x := recover()

98 if x != nil && x != "stop" {

99 panic(x)

100 }

101 }()

102 fail := func(format string, args ...any) {

103 err := fmt.Errorf("server: %w", fmt.Errorf(format, args...))

104 log.Errorx("failure", err)

105 if err != nil && expServerErr != nil && (errors.Is(err, expServerErr) || errors.As(err, reflect.New(reflect.ValueOf(expServerErr).Type()).Interface())) {

106 err = nil

107 }

108 result <- err

109 panic("stop")

110 }

111

112 br := bufio.NewReader(serverConn)

113 readline := func(prefix string) string {

114 s, err := br.ReadString('\n')

115 if err != nil {

116 fail("expected command: %v", err)

117 }

118 if !strings.HasPrefix(strings.ToLower(s), strings.ToLower(prefix)) {

119 fail("expected command %q, got: %s", prefix, s)

120 }

121 s = s[len(prefix):]

122 return strings.TrimSuffix(s, "\r\n")

123 }

124 writeline := func(s string) {

125 fmt.Fprintf(serverConn, "%s\r\n", s)

126 }

127

128 haveTLS := false

129

130 ehlo := true // Initially we expect EHLO.

131 var hello func()

132 hello = func() {

133 if !ehlo {

134 readline("HELO")

135 writeline("250 mox.example")

136 return

137 }

138

139 readline("EHLO")

140

141 if !opts.ehlo {

142 // Client will try again with HELO.

143 writeline("500 bad syntax")

144 ehlo = false

145 hello()

146 return

147 }

148

149 writeline("250-mox.example")

150 if opts.pipelining {

151 writeline("250-PIPELINING")

152 }

153 if opts.maxSize > 0 {

154 writeline(fmt.Sprintf("250-SIZE %d", opts.maxSize))

155 }

156 if opts.ecodes {

157 writeline("250-ENHANCEDSTATUSCODES")

158 }

159 if opts.starttls && !haveTLS {

160 writeline("250-STARTTLS")

161 }

162 if opts.eightbitmime {

163 writeline("250-8BITMIME")

164 }

165 if opts.smtputf8 {

166 writeline("250-SMTPUTF8")

167 }

168 if opts.requiretls && haveTLS {

169 writeline("250-REQUIRETLS")

170 }

171 if opts.auths != nil {

172 writeline("250-AUTH " + strings.Join(opts.auths, " "))

173 }

174 writeline("250-LIMITS MAILMAX=10 RCPTMAX=100 RCPTDOMAINMAX=1")

175 writeline("250 UNKNOWN") // To be ignored.

176 }

177

178 writeline("220 mox.example ESMTP test")

179

180 hello()

181

182 if opts.starttls {

183 readline("STARTTLS")

184 writeline("220 go")

185 tlsConn := tls.Server(serverConn, &tlsConfig)

186 nctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)

187 defer cancel()

188 err := tlsConn.HandshakeContext(nctx)

189 if err != nil {

190 fail("tls handshake: %w", err)

191 }

192 serverConn = tlsConn

193 br = bufio.NewReader(serverConn)

194

195 haveTLS = true

196 hello()

197 }

198

199 if opts.auths != nil {

200 more := readline("AUTH ")

201 t := strings.SplitN(more, " ", 2)

202 switch t[0] {

203 case "PLAIN":

204 writeline("235 2.7.0 auth ok")

205 case "CRAM-MD5":

206 writeline("334 " + base64.StdEncoding.EncodeToString([]byte("<123.1234@host>")))

207 readline("") // Proof

208 writeline("235 2.7.0 auth ok")

209 case "SCRAM-SHA-256-PLUS", "SCRAM-SHA-256", "SCRAM-SHA-1-PLUS", "SCRAM-SHA-1":

210 // Cannot fake/hardcode scram interactions.

211 var h func() hash.Hash

212 salt := scram.MakeRandom()

213 var iterations int

214 switch t[0] {

215 case "SCRAM-SHA-1-PLUS", "SCRAM-SHA-1":

216 h = sha1.New

217 iterations = 2 * 4096

218 case "SCRAM-SHA-256-PLUS", "SCRAM-SHA-256":

219 h = sha256.New

220 iterations = 4096

221 default:

222 panic("missing case for scram")

223 }

224 var cs *tls.ConnectionState

225 if strings.HasSuffix(t[0], "-PLUS") {

226 if !haveTLS {

227 writeline("501 scram plus without tls not possible")

228 readline("QUIT")

229 writeline("221 ok")

230 result <- nil

231 return

232 }

233 xcs := serverConn.(*tls.Conn).ConnectionState()

234 cs = &xcs

235 }

236 saltedPassword := scram.SaltPassword(h, "test", salt, iterations)

237

238 clientFirst, err := base64.StdEncoding.DecodeString(t[1])

239 if err != nil {

240 fail("bad base64: %w", err)

241 }

242 s, err := scram.NewServer(h, clientFirst, cs, cs != nil)

243 if err != nil {

244 fail("scram new server: %w", err)

245 }

246 serverFirst, err := s.ServerFirst(iterations, salt)

247 if err != nil {

248 fail("scram server first: %w", err)

249 }

250 writeline("334 " + base64.StdEncoding.EncodeToString([]byte(serverFirst)))

251

252 xclientFinal := readline("")

253 clientFinal, err := base64.StdEncoding.DecodeString(xclientFinal)

254 if err != nil {

255 fail("bad base64: %w", err)

256 }

257 serverFinal, err := s.Finish([]byte(clientFinal), saltedPassword)

258 if err != nil {

259 fail("scram finish: %w", err)

260 }

261 writeline("334 " + base64.StdEncoding.EncodeToString([]byte(serverFinal)))

262 readline("")

263 writeline("235 2.7.0 auth ok")

264 default:

265 writeline("501 unknown mechanism")

266 }

267 }

268

269 if expClientErr == nil && !opts.nodeliver {

270 readline("MAIL FROM:")

271 writeline("250 ok")

272 n := len(opts.recipients)

273 if n == 0 {

274 n = 1

275 }

276 for i := 0; i < n; i++ {

277 readline("RCPT TO:")

278 resp := "250 ok"

279 if i < len(opts.resps) {

280 resp = fmt.Sprintf("%d maybe", opts.resps[i].Code)

281 }

282 writeline(resp)

283 }

284 readline("DATA")

285 writeline("354 continue")

286 reader := smtp.NewDataReader(br)

287 io.Copy(io.Discard, reader)

288 writeline("250 ok")

289

290 if expDeliverErr == nil {

291 readline("RSET")

292 writeline("250 ok")

293

294 readline("MAIL FROM:")

295 writeline("250 ok")

296 for i := 0; i < n; i++ {

297 readline("RCPT TO:")

298 resp := "250 ok"

299 if i < len(opts.resps) {

300 resp = fmt.Sprintf("%d maybe", opts.resps[i].Code)

301 }

302 writeline(resp)

303 }

304 readline("DATA")

305 writeline("354 continue")

306 reader = smtp.NewDataReader(br)

307 io.Copy(io.Discard, reader)

308 writeline("250 ok")

309 }

310 }

311

312 readline("QUIT")

313 writeline("221 ok")

314 result <- nil

315 }()

316

317 // todo: should abort tests more properly. on client failures, we may be left with hanging test.

318 go func() {

319 defer func() {

320 x := recover()

321 if x != nil && x != "stop" {

322 panic(x)

323 }

324 }()

325 fail := func(format string, args ...any) {

326 err := fmt.Errorf("client: %w", fmt.Errorf(format, args...))

327 log.Errorx("failure", err)

328 result <- err

329 panic("stop")

330 }

331 client, err := New(ctx, log.Logger, clientConn, opts.tlsMode, opts.tlsPKIX, localhost, opts.tlsHostname, Opts{Auth: auth, RootCAs: opts.roots})

332 if (err == nil) != (expClientErr == nil) || err != nil && !errors.As(err, reflect.New(reflect.ValueOf(expClientErr).Type()).Interface()) && !errors.Is(err, expClientErr) {

333 fail("new client: got err %v, expected %#v", err, expClientErr)

334 }

335 if err != nil {

336 result <- nil

337 return

338 }

339 rcptTo := opts.recipients

340 if len(rcptTo) == 0 {

341 rcptTo = []string{"mjl@mox.example"}

342 }

343 resps, err := client.DeliverMultiple(ctx, "postmaster@mox.example", rcptTo, int64(len(msg)), strings.NewReader(msg), opts.need8bitmime, opts.needsmtputf8, opts.needsrequiretls)

344 if (err == nil) != (expDeliverErr == nil) || err != nil && !errors.Is(err, expDeliverErr) && !reflect.DeepEqual(err, expDeliverErr) {

345 fail("first deliver: got err %#v (%s), expected %#v (%s)", err, err, expDeliverErr, expDeliverErr)

346 } else if opts.resps != nil && !reflect.DeepEqual(cleanupResp(resps), opts.resps) {

347 fail("first deliver: got resps %v, expected %v", resps, opts.resps)

348 }

349 if err == nil {

350 err = client.Reset()

351 if err != nil {

352 fail("reset: %v", err)

353 }

354 resps, err = client.DeliverMultiple(ctx, "postmaster@mox.example", rcptTo, int64(len(msg)), strings.NewReader(msg), opts.need8bitmime, opts.needsmtputf8, opts.needsrequiretls)

355 if (err == nil) != (expDeliverErr == nil) || err != nil && !errors.Is(err, expDeliverErr) && !reflect.DeepEqual(err, expDeliverErr) {

356 fail("second deliver: got err %#v (%s), expected %#v (%s)", err, err, expDeliverErr, expDeliverErr)

357 } else if opts.resps != nil && !reflect.DeepEqual(cleanupResp(resps), opts.resps) {

358 fail("second: got resps %v, expected %v", resps, opts.resps)

359 }

360 }

361 err = client.Close()

362 if err != nil {

363 fail("close client: %v", err)

364 }

365 result <- nil

366 }()

367

368 var errs []error

369 for i := 0; i < 2; i++ {

370 err := <-result

371 if err != nil {

372 errs = append(errs, err)

373 }

374 }

375 if errs != nil {

376 t.Fatalf("%v", errs)

377 }

378 }

379

380 msg := strings.ReplaceAll(`From: <postmaster@mox.example>

381To: <mjl@mox.example>

382Subject: test

383

384test

385`, "\n", "\r\n")

386

387 allopts := options{

388 pipelining: true,

389 ecodes: true,

390 maxSize: 512,

391 eightbitmime: true,

392 smtputf8: true,

393 starttls: true,

394 ehlo: true,

395 requiretls: true,

396

397 tlsMode: TLSRequiredStartTLS,

398 tlsPKIX: true,

399 roots: roots,

400 tlsHostname: dns.Domain{ASCII: "mox.example"},

401 need8bitmime: true,

402 needsmtputf8: true,

403 needsrequiretls: true,

404 }

405

406 test(msg, options{}, nil, nil, nil, nil)

407 test(msg, allopts, nil, nil, nil, nil)

408 test(msg, options{ehlo: true, eightbitmime: true}, nil, nil, nil, nil)

409 test(msg, options{ehlo: true, eightbitmime: false, need8bitmime: true, nodeliver: true}, nil, nil, Err8bitmimeUnsupported, nil)

410 test(msg, options{ehlo: true, smtputf8: false, needsmtputf8: true, nodeliver: true}, nil, nil, ErrSMTPUTF8Unsupported, nil)

411

412 // Server TLS handshake is a net.OpError with "remote error" as text.

413 test(msg, options{ehlo: true, starttls: true, tlsMode: TLSRequiredStartTLS, tlsPKIX: true, tlsHostname: dns.Domain{ASCII: "mismatch.example"}, nodeliver: true}, nil, ErrTLS, nil, &net.OpError{})

414

415 test(msg, options{ehlo: true, maxSize: len(msg) - 1, nodeliver: true}, nil, nil, ErrSize, nil)

416

417 // Multiple recipients, not pipelined.

418 multi1 := options{

419 ehlo: true,

420 pipelining: true,

421 ecodes: true,

422 recipients: []string{"mjl@mox.example", "mjl2@mox.example", "mjl3@mox.example"},

423 resps: []Response{

424 {Code: smtp.C250Completed},

425 {Code: smtp.C250Completed},

426 {Code: smtp.C250Completed},

427 },

428 }

429 test(msg, multi1, nil, nil, nil, nil)

430 multi1.pipelining = true

431 test(msg, multi1, nil, nil, nil, nil)

432

433 // Multiple recipients with 452 and other error, not pipelined

434 multi2 := options{

435 ehlo: true,

436 ecodes: true,

437 recipients: []string{"xmjl@mox.example", "xmjl2@mox.example", "xmjl3@mox.example"},

438 resps: []Response{

439 {Code: smtp.C250Completed},

440 {Code: smtp.C554TransactionFailed}, // Will continue when not pipelined.

441 {Code: smtp.C452StorageFull}, // Will stop sending further recipients.

442 },

443 }

444 test(msg, multi2, nil, nil, nil, nil)

445 multi2.pipelining = true

446 test(msg, multi2, nil, nil, nil, nil)

447 multi2.pipelining = false

448 multi2.resps[2].Code = smtp.C552MailboxFull

449 test(msg, multi2, nil, nil, nil, nil)

450 multi2.pipelining = true

451 test(msg, multi2, nil, nil, nil, nil)

452

453 // Single recipient with error and pipelining is an error.

454 multi3 := options{

455 ehlo: true,

456 pipelining: true,

457 ecodes: true,

458 recipients: []string{"xmjl@mox.example"},

459 resps: []Response{{Code: smtp.C452StorageFull}},

460 }

461 test(msg, multi3, nil, nil, Error{Code: smtp.C452StorageFull, Command: "rcptto", Line: "452 maybe"}, nil)

462

463 authPlain := func(l []string, cs *tls.ConnectionState) (sasl.Client, error) {

464 return sasl.NewClientPlain("test", "test"), nil

465 }

466 test(msg, options{ehlo: true, auths: []string{"PLAIN"}}, authPlain, nil, nil, nil)

467

468 authCRAMMD5 := func(l []string, cs *tls.ConnectionState) (sasl.Client, error) {

469 return sasl.NewClientCRAMMD5("test", "test"), nil

470 }

471 test(msg, options{ehlo: true, auths: []string{"CRAM-MD5"}}, authCRAMMD5, nil, nil, nil)

472

473 // todo: add tests for failing authentication, also at various stages in SCRAM

474

475 authSCRAMSHA1 := func(l []string, cs *tls.ConnectionState) (sasl.Client, error) {

476 return sasl.NewClientSCRAMSHA1("test", "test", false), nil

477 }

478 test(msg, options{ehlo: true, auths: []string{"SCRAM-SHA-1"}}, authSCRAMSHA1, nil, nil, nil)

479

480 authSCRAMSHA1PLUS := func(l []string, cs *tls.ConnectionState) (sasl.Client, error) {

481 return sasl.NewClientSCRAMSHA1PLUS("test", "test", *cs), nil

482 }

483 test(msg, options{ehlo: true, starttls: true, auths: []string{"SCRAM-SHA-1-PLUS"}}, authSCRAMSHA1PLUS, nil, nil, nil)

484

485 authSCRAMSHA256 := func(l []string, cs *tls.ConnectionState) (sasl.Client, error) {

486 return sasl.NewClientSCRAMSHA256("test", "test", false), nil

487 }

488 test(msg, options{ehlo: true, auths: []string{"SCRAM-SHA-256"}}, authSCRAMSHA256, nil, nil, nil)

489

490 authSCRAMSHA256PLUS := func(l []string, cs *tls.ConnectionState) (sasl.Client, error) {

491 return sasl.NewClientSCRAMSHA256PLUS("test", "test", *cs), nil

492 }

493 test(msg, options{ehlo: true, starttls: true, auths: []string{"SCRAM-SHA-256-PLUS"}}, authSCRAMSHA256PLUS, nil, nil, nil)

494

495 test(msg, options{ehlo: true, requiretls: false, needsrequiretls: true, nodeliver: true}, nil, nil, ErrRequireTLSUnsupported, nil)

496

497 // Set an expired certificate. For non-strict TLS, we should still accept it.

498 // ../rfc/7435:424

499 cert = fakeCert(t, true)

500 roots = x509.NewCertPool()

501 roots.AddCert(cert.Leaf)

502 tlsConfig = tls.Config{

503 Certificates: []tls.Certificate{cert},

504 }

505 test(msg, options{ehlo: true, starttls: true, roots: roots}, nil, nil, nil, nil)

506

507 // Again with empty cert pool so it isn't trusted in any way.

508 roots = x509.NewCertPool()

509 tlsConfig = tls.Config{

510 Certificates: []tls.Certificate{cert},

511 }

512 test(msg, options{ehlo: true, starttls: true, roots: roots}, nil, nil, nil, nil)

513}

514

515func TestErrors(t *testing.T) {

516 ctx := context.Background()

517 log := mlog.New("smtpclient", nil)

518

519 // Invalid greeting.

520 run(t, func(s xserver) {

521 s.writeline("bogus") // Invalid, should be "220 <hostname>".

522 }, func(conn net.Conn) {

523 _, err := New(ctx, log.Logger, conn, TLSOpportunistic, false, localhost, zerohost, Opts{})

524 var xerr Error

525 if err == nil || !errors.Is(err, ErrProtocol) || !errors.As(err, &xerr) || xerr.Permanent {

526 panic(fmt.Errorf("got %#v, expected ErrProtocol without Permanent", err))

527 }

528 })

529

530 // Server just closes connection.

531 run(t, func(s xserver) {

532 s.conn.Close()

533 }, func(conn net.Conn) {

534 _, err := New(ctx, log.Logger, conn, TLSOpportunistic, false, localhost, zerohost, Opts{})

535 var xerr Error

536 if err == nil || !errors.Is(err, io.ErrUnexpectedEOF) || !errors.As(err, &xerr) || xerr.Permanent {

537 panic(fmt.Errorf("got %#v (%v), expected ErrUnexpectedEOF without Permanent", err, err))

538 }

539 })

540

541 // Server does not want to speak SMTP.

542 run(t, func(s xserver) {

543 s.writeline("521 not accepting connections")

544 }, func(conn net.Conn) {

545 _, err := New(ctx, log.Logger, conn, TLSOpportunistic, false, localhost, zerohost, Opts{})

546 var xerr Error

547 if err == nil || !errors.Is(err, ErrStatus) || !errors.As(err, &xerr) || !xerr.Permanent {

548 panic(fmt.Errorf("got %#v, expected ErrStatus with Permanent", err))

549 }

550 })

551

552 // Server has invalid code in greeting.

553 run(t, func(s xserver) {

554 s.writeline("2200 mox.example") // Invalid, too many digits.

555 }, func(conn net.Conn) {

556 _, err := New(ctx, log.Logger, conn, TLSOpportunistic, false, localhost, zerohost, Opts{})

557 var xerr Error

558 if err == nil || !errors.Is(err, ErrProtocol) || !errors.As(err, &xerr) || xerr.Permanent {

559 panic(fmt.Errorf("got %#v, expected ErrProtocol without Permanent", err))

560 }

561 })

562

563 // Server sends multiline response, but with different codes.

564 run(t, func(s xserver) {

565 s.writeline("220 mox.example")

566 s.readline("EHLO")

567 s.writeline("250-mox.example")

568 s.writeline("500 different code") // Invalid.

569 }, func(conn net.Conn) {

570 _, err := New(ctx, log.Logger, conn, TLSOpportunistic, false, localhost, zerohost, Opts{})

571 var xerr Error

572 if err == nil || !errors.Is(err, ErrProtocol) || !errors.As(err, &xerr) || xerr.Permanent {

573 panic(fmt.Errorf("got %#v, expected ErrProtocol without Permanent", err))

574 }

575 })

576

577 // Server permanently refuses MAIL FROM.

578 run(t, func(s xserver) {

579 s.writeline("220 mox.example")

580 s.readline("EHLO")

581 s.writeline("250-mox.example")

582 s.writeline("250 ENHANCEDSTATUSCODES")

583 s.readline("MAIL FROM:")

584 s.writeline("550 5.7.0 not allowed")

585 }, func(conn net.Conn) {

586 c, err := New(ctx, log.Logger, conn, TLSOpportunistic, false, localhost, zerohost, Opts{})

587 if err != nil {

588 panic(err)

589 }

590 msg := ""

591 err = c.Deliver(ctx, "postmaster@other.example", "mjl@mox.example", int64(len(msg)), strings.NewReader(msg), false, false, false)

592 var xerr Error

593 if err == nil || !errors.Is(err, ErrStatus) || !errors.As(err, &xerr) || !xerr.Permanent {

594 panic(fmt.Errorf("got %#v, expected ErrStatus with Permanent", err))

595 }

596 })

597

598 // Server temporarily refuses MAIL FROM.

599 run(t, func(s xserver) {

600 s.writeline("220 mox.example")

601 s.readline("EHLO")

602 s.writeline("250 mox.example")

603 s.readline("MAIL FROM:")

604 s.writeline("451 bad sender")

605 }, func(conn net.Conn) {

606 c, err := New(ctx, log.Logger, conn, TLSOpportunistic, false, localhost, zerohost, Opts{})

607 if err != nil {

608 panic(err)

609 }

610 msg := ""

611 err = c.Deliver(ctx, "postmaster@other.example", "mjl@mox.example", int64(len(msg)), strings.NewReader(msg), false, false, false)

612 var xerr Error

613 if err == nil || !errors.Is(err, ErrStatus) || !errors.As(err, &xerr) || xerr.Permanent {

614 panic(fmt.Errorf("got %#v, expected ErrStatus with not-Permanent", err))

615 }

616 })

617

618 // Server temporarily refuses RCPT TO.

619 run(t, func(s xserver) {

620 s.writeline("220 mox.example")

621 s.readline("EHLO")

622 s.writeline("250 mox.example")

623 s.readline("MAIL FROM:")

624 s.writeline("250 ok")

625 s.readline("RCPT TO:")

626 s.writeline("451")

627 }, func(conn net.Conn) {

628 c, err := New(ctx, log.Logger, conn, TLSOpportunistic, false, localhost, zerohost, Opts{})

629 if err != nil {

630 panic(err)

631 }

632 msg := ""

633 err = c.Deliver(ctx, "postmaster@other.example", "mjl@mox.example", int64(len(msg)), strings.NewReader(msg), false, false, false)

634 var xerr Error

635 if err == nil || !errors.Is(err, ErrStatus) || !errors.As(err, &xerr) || xerr.Permanent {

636 panic(fmt.Errorf("got %#v, expected ErrStatus with not-Permanent", err))

637 }

638 })

639

640 // Server permanently refuses DATA.

641 run(t, func(s xserver) {

642 s.writeline("220 mox.example")

643 s.readline("EHLO")

644 s.writeline("250 mox.example")

645 s.readline("MAIL FROM:")

646 s.writeline("250 ok")

647 s.readline("RCPT TO:")

648 s.writeline("250 ok")

649 s.readline("DATA")

650 s.writeline("550 no!")

651 }, func(conn net.Conn) {

652 c, err := New(ctx, log.Logger, conn, TLSOpportunistic, false, localhost, zerohost, Opts{})

653 if err != nil {

654 panic(err)

655 }

656 msg := ""

657 err = c.Deliver(ctx, "postmaster@other.example", "mjl@mox.example", int64(len(msg)), strings.NewReader(msg), false, false, false)

658 var xerr Error

659 if err == nil || !errors.Is(err, ErrStatus) || !errors.As(err, &xerr) || !xerr.Permanent {

660 panic(fmt.Errorf("got %#v, expected ErrStatus with Permanent", err))

661 }

662 })

663

664 // TLS is required, so we attempt it regardless of whether it is advertised.

665 run(t, func(s xserver) {

666 s.writeline("220 mox.example")

667 s.readline("EHLO")

668 s.writeline("250 mox.example")

669 s.readline("STARTTLS")

670 s.writeline("502 command not implemented")

671 }, func(conn net.Conn) {

672 _, err := New(ctx, log.Logger, conn, TLSRequiredStartTLS, true, localhost, dns.Domain{ASCII: "mox.example"}, Opts{})

673 var xerr Error

674 if err == nil || !errors.Is(err, ErrTLS) || !errors.As(err, &xerr) || !xerr.Permanent {

675 panic(fmt.Errorf("got %#v, expected ErrTLS with Permanent", err))

676 }

677 })

678

679 // If TLS is available, but we don't want to use it, client should skip it.

680 run(t, func(s xserver) {

681 s.writeline("220 mox.example")

682 s.readline("EHLO")

683 s.writeline("250-mox.example")

684 s.writeline("250 STARTTLS")

685 s.readline("MAIL FROM:")

686 s.writeline("451 enough")

687 }, func(conn net.Conn) {

688 c, err := New(ctx, log.Logger, conn, TLSSkip, false, localhost, dns.Domain{ASCII: "mox.example"}, Opts{})

689 if err != nil {

690 panic(err)

691 }

692 msg := ""

693 err = c.Deliver(ctx, "postmaster@other.example", "mjl@mox.example", int64(len(msg)), strings.NewReader(msg), false, false, false)

694 var xerr Error

695 if err == nil || !errors.Is(err, ErrStatus) || !errors.As(err, &xerr) || xerr.Permanent {

696 panic(fmt.Errorf("got %#v, expected ErrStatus with non-Permanent", err))

697 }

698 })

699

700 // A transaction is aborted. If we try another one, we should send a RSET.

701 run(t, func(s xserver) {

702 s.writeline("220 mox.example")

703 s.readline("EHLO")

704 s.writeline("250 mox.example")

705 s.readline("MAIL FROM:")

706 s.writeline("250 ok")

707 s.readline("RCPT TO:")

708 s.writeline("451 not now")

709 s.readline("RSET")

710 s.writeline("250 ok")

711 s.readline("MAIL FROM:")

712 s.writeline("250 ok")

713 s.readline("RCPT TO:")

714 s.writeline("250 ok")

715 s.readline("DATA")

716 s.writeline("550 not now")

717 }, func(conn net.Conn) {

718 c, err := New(ctx, log.Logger, conn, TLSOpportunistic, false, localhost, zerohost, Opts{})

719 if err != nil {

720 panic(err)

721 }

722

723 msg := ""

724 err = c.Deliver(ctx, "postmaster@other.example", "mjl@mox.example", int64(len(msg)), strings.NewReader(msg), false, false, false)

725 var xerr Error

726 if err == nil || !errors.Is(err, ErrStatus) || !errors.As(err, &xerr) || xerr.Permanent {

727 panic(fmt.Errorf("got %#v, expected ErrStatus with non-Permanent", err))

728 }

729

730 // Another delivery.

731 err = c.Deliver(ctx, "postmaster@other.example", "mjl@mox.example", int64(len(msg)), strings.NewReader(msg), false, false, false)

732 if err == nil || !errors.Is(err, ErrStatus) || !errors.As(err, &xerr) || !xerr.Permanent {

733 panic(fmt.Errorf("got %#v, expected ErrStatus with Permanent", err))

734 }

735 })

736

737 // Remote closes connection after 550 response to MAIL FROM in pipelined

738 // connection. Should result in permanent error, not temporary read error.

739 // E.g. outlook.com that has your IP blocklisted.

740 run(t, func(s xserver) {

741 s.writeline("220 mox.example")

742 s.readline("EHLO")

743 s.writeline("250-mox.example")

744 s.writeline("250 PIPELINING")

745 s.readline("MAIL FROM:")

746 s.writeline("550 ok")

747 }, func(conn net.Conn) {

748 c, err := New(ctx, log.Logger, conn, TLSOpportunistic, false, localhost, zerohost, Opts{})

749 if err != nil {

750 panic(err)

751 }

752

753 msg := ""

754 err = c.Deliver(ctx, "postmaster@other.example", "mjl@mox.example", int64(len(msg)), strings.NewReader(msg), false, false, false)

755 var xerr Error

756 if err == nil || !errors.Is(err, ErrStatus) || !errors.As(err, &xerr) || !xerr.Permanent {

757 panic(fmt.Errorf("got %#v, expected ErrStatus with Permanent", err))

758 }

759 })

760

761 // Remote closes connection after 554 response to RCPT TO in pipelined

762 // connection. Should result in permanent error, not temporary read error.

763 // E.g. icloud.com that has your IP blocklisted.

764 run(t, func(s xserver) {

765 s.writeline("220 mox.example")

766 s.readline("EHLO")

767 s.writeline("250-mox.example")

768 s.writeline("250-ENHANCEDSTATUSCODES")

769 s.writeline("250 PIPELINING")

770 s.readline("MAIL FROM:")

771 s.writeline("250 2.1.0 ok")

772 s.readline("RCPT TO:")

773 s.writeline("554 5.7.0 Blocked")

774 }, func(conn net.Conn) {

775 c, err := New(ctx, log.Logger, conn, TLSOpportunistic, false, localhost, zerohost, Opts{})

776 if err != nil {

777 panic(err)

778 }

779

780 msg := ""

781 err = c.Deliver(ctx, "postmaster@other.example", "mjl@mox.example", int64(len(msg)), strings.NewReader(msg), false, false, false)

782 var xerr Error

783 if err == nil || !errors.Is(err, ErrStatus) || !errors.As(err, &xerr) || !xerr.Permanent {

784 panic(fmt.Errorf("got %#v, expected ErrStatus with Permanent", err))

785 }

786 })

787

788 // If we try multiple recipients and first is 452, it is an error and a

789 // non-pipelined deliver will be aborted.

790 run(t, func(s xserver) {

791 s.writeline("220 mox.example")

792 s.readline("EHLO")

793 s.writeline("250 mox.example")

794 s.readline("MAIL FROM:")

795 s.writeline("250 ok")

796 s.readline("RCPT TO:")

797 s.writeline("451 not now")

798 s.readline("RCPT TO:")

799 s.writeline("451 not now")

800 s.readline("QUIT")

801 s.writeline("250 ok")

802 }, func(conn net.Conn) {

803 c, err := New(ctx, log.Logger, conn, TLSOpportunistic, false, localhost, zerohost, Opts{})

804 if err != nil {

805 panic(err)

806 }

807

808 msg := ""

809 _, err = c.DeliverMultiple(ctx, "postmaster@other.example", []string{"mjl@mox.example", "mjl@mox.example"}, int64(len(msg)), strings.NewReader(msg), false, false, false)

810 var xerr Error

811 if err == nil || !errors.Is(err, errNoRecipients) || !errors.As(err, &xerr) || xerr.Permanent {

812 panic(fmt.Errorf("got %#v (%s) expected errNoRecipients with non-Permanent", err, err))

813 }

814 c.Close()

815 })

816

817 // If we try multiple recipients and first is 452, it is an error and a pipelined

818 // deliver will abort an allowed DATA.

819 run(t, func(s xserver) {

820 s.writeline("220 mox.example")

821 s.readline("EHLO")

822 s.writeline("250-mox.example")

823 s.writeline("250 PIPELINING")

824 s.readline("MAIL FROM:")

825 s.writeline("250 ok")

826 s.readline("RCPT TO:")

827 s.writeline("451 not now")

828 s.readline("RCPT TO:")

829 s.writeline("451 not now")

830 s.readline("DATA")

831 s.writeline("354 ok")

832 s.readline(".")

833 s.writeline("503 no recipient")

834 s.readline("QUIT")

835 s.writeline("250 ok")

836 }, func(conn net.Conn) {

837 c, err := New(ctx, log.Logger, conn, TLSOpportunistic, false, localhost, zerohost, Opts{})

838 if err != nil {

839 panic(err)

840 }

841

842 msg := ""

843 _, err = c.DeliverMultiple(ctx, "postmaster@other.example", []string{"mjl@mox.example", "mjl@mox.example"}, int64(len(msg)), strings.NewReader(msg), false, false, false)

844 var xerr Error

845 if err == nil || !errors.Is(err, errNoRecipientsPipelined) || !errors.As(err, &xerr) || xerr.Permanent {

846 panic(fmt.Errorf("got %#v (%s), expected errNoRecipientsPipelined with non-Permanent", err, err))

847 }

848 c.Close()

849 })

850}

851

852type xserver struct {

853 conn net.Conn

854 br *bufio.Reader

855}

856

857func (s xserver) check(err error, msg string) {

858 if err != nil {

859 panic(fmt.Errorf("%s: %w", msg, err))

860 }

861}

862

863func (s xserver) errorf(format string, args ...any) {

864 panic(fmt.Errorf(format, args...))

865}

866

867func (s xserver) writeline(line string) {

868 _, err := fmt.Fprintf(s.conn, "%s\r\n", line)

869 s.check(err, "write")

870}

871

872func (s xserver) readline(prefix string) {

873 line, err := s.br.ReadString('\n')

874 s.check(err, "reading command")

875 if !strings.HasPrefix(strings.ToLower(line), strings.ToLower(prefix)) {

876 s.errorf("expected command %q, got: %s", prefix, line)

877 }

878}

879

880func run(t *testing.T, server func(s xserver), client func(conn net.Conn)) {

881 t.Helper()

882

883 result := make(chan error, 2)

884 clientConn, serverConn := net.Pipe()

885 go func() {

886 defer func() {

887 serverConn.Close()

888 x := recover()

889 if x != nil {

890 result <- fmt.Errorf("server: %v", x)

891 } else {

892 result <- nil

893 }

894 }()

895 server(xserver{serverConn, bufio.NewReader(serverConn)})

896 }()

897 go func() {

898 defer func() {

899 clientConn.Close()

900 x := recover()

901 if x != nil {

902 result <- fmt.Errorf("client: %v", x)

903 } else {

904 result <- nil

905 }

906 }()

907 client(clientConn)

908 }()

909 var errs []error

910 for i := 0; i < 2; i++ {

911 err := <-result

912 if err != nil {

913 errs = append(errs, err)

914 }

915 }

916 if errs != nil {

917 t.Fatalf("errors: %v", errs)

918 }

919}

920

921func TestLimits(t *testing.T) {

922 check := func(s string, expLimits map[string]string, expMailMax, expRcptMax, expRcptDomainMax int) {

923 t.Helper()

924 limits, mailmax, rcptMax, rcptDomainMax := parseLimits([]byte(s))

925 if !reflect.DeepEqual(limits, expLimits) || mailmax != expMailMax || rcptMax != expRcptMax || rcptDomainMax != expRcptDomainMax {

926 t.Errorf("bad limits, got %v %d %d %d, expected %v %d %d %d, for %q", limits, mailmax, rcptMax, rcptDomainMax, expLimits, expMailMax, expRcptMax, expRcptDomainMax, s)

927 }

928 }

929 check(" unknown=a=b -_1oK=xY", map[string]string{"UNKNOWN": "a=b", "-_1OK": "xY"}, 0, 0, 0)

930 check(" MAILMAX=123 OTHER=ignored RCPTDOMAINMAX=1 RCPTMAX=321", map[string]string{"MAILMAX": "123", "OTHER": "ignored", "RCPTDOMAINMAX": "1", "RCPTMAX": "321"}, 123, 321, 1)

931 check(" MAILMAX=invalid", map[string]string{"MAILMAX": "invalid"}, 0, 0, 0)

932 check(" invalid syntax", nil, 0, 0, 0)

933 check(" DUP=1 DUP=2", nil, 0, 0, 0)

934}

935

936// Just a cert that appears valid. SMTP client will not verify anything about it

937// (that is opportunistic TLS for you, "better some than none"). Let's enjoy this

938// one moment where it makes life easier.

939func fakeCert(t *testing.T, expired bool) tls.Certificate {

940 notAfter := time.Now()

941 if expired {

942 notAfter = notAfter.Add(-time.Hour)