1package message

2

3import (

4 "fmt"

5 "io"

6 "log/slog"

7 "net/textproto"

8

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

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

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

12)

13

14// From extracts the address in the From-header.

15//

16// An RFC5322 message must have a From header.

17// In theory, multiple addresses may be present. In practice zero or multiple

18// From headers may be present. From returns an error if there is not exactly

19// one address. This address can be used for evaluating a DMARC policy against

20// SPF and DKIM results.

21func From(elog *slog.Logger, strict bool, r io.ReaderAt, p *Part) (raddr smtp.Address, envelope *Envelope, header textproto.MIMEHeader, rerr error) {

22 log := mlog.New("message", elog)

23

24 // ../rfc/7489:1243

25

26 // todo: only allow utf8 if enabled in session/message?

27

28 var err error

29 if p == nil {

30 var pp Part

31 pp, err = Parse(log.Logger, strict, r)

32 if err != nil {

33 // todo: should we continue with p, perhaps headers can be parsed?

34 return raddr, nil, nil, fmt.Errorf("parsing message: %v", err)

35 }

36 p = &pp

37 }

38 header, err = p.Header()

39 if err != nil {

40 return raddr, nil, nil, fmt.Errorf("parsing message header: %v", err)

41 }

42 from := p.Envelope.From

43 if len(from) != 1 {

44 return raddr, nil, nil, fmt.Errorf("from header has %d addresses, need exactly 1 address", len(from))

45 }

46 d, err := dns.ParseDomain(from[0].Host)

47 if err != nil {

48 return raddr, nil, nil, fmt.Errorf("bad domain in from address: %v", err)

49 }

50 lp, err := smtp.ParseLocalpart(from[0].User)

51 if err != nil {

52 return raddr, nil, nil, fmt.Errorf("parsing localpart in from address: %v", err)

53 }

54 addr := smtp.NewAddress(lp, d)

55 return addr, p.Envelope, textproto.MIMEHeader(header), nil

56}

57