1package message

2

3import (

4 "fmt"

5 "io"

6 "net/textproto"

7

8 "golang.org/x/exp/slog"

9

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

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

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

13)

14

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

16//

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

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

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

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

21// SPF and DKIM results.

22func From(elog *slog.Logger, strict bool, r io.ReaderAt) (raddr smtp.Address, envelope *Envelope, header textproto.MIMEHeader, rerr error) {

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

24

25 // ../rfc/7489:1243

26

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

28

29 p, err := Parse(log.Logger, strict, r)

30 if err != nil {

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

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

33 }

34 header, err = p.Header()

35 if err != nil {

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

37 }

38 from := p.Envelope.From

39 if len(from) != 1 {

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

41 }

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

43 if err != nil {

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

45 }

46 addr := smtp.Address{Localpart: smtp.Localpart(from[0].User), Domain: d}

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

48}

49