mirror of
https://github.com/mjl-/mox.git
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360 lines
10 KiB
Go
360 lines
10 KiB
Go
package dsn
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import (
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"bufio"
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"fmt"
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"io"
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"net/textproto"
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"strconv"
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"strings"
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"time"
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"github.com/mjl-/mox/dns"
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"github.com/mjl-/mox/message"
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"github.com/mjl-/mox/smtp"
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)
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// Parse reads a DSN message.
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//
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// A DSN is a multipart internet mail message with 2 or 3 parts: human-readable
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// text, machine-parsable text, and optional original message or headers.
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//
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// The first return value is the machine-parsed DSN message. The second value is
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// the entire MIME multipart message. Use its Parts field to access the
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// human-readable text and optional original message/headers.
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func Parse(r io.ReaderAt) (*Message, *message.Part, error) {
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// DSNs can mix and match subtypes with and without utf-8. ../rfc/6533:441
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part, err := message.Parse(r)
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if err != nil {
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return nil, nil, fmt.Errorf("parsing message: %v", err)
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}
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if part.MediaType != "MULTIPART" || part.MediaSubType != "REPORT" {
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return nil, nil, fmt.Errorf(`message has content-type %q, must have "message/report"`, strings.ToLower(part.MediaType+"/"+part.MediaSubType))
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}
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err = part.Walk(nil)
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if err != nil {
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return nil, nil, fmt.Errorf("parsing message parts: %v", err)
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}
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nparts := len(part.Parts)
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if nparts != 2 && nparts != 3 {
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return nil, nil, fmt.Errorf("invalid dsn, got %d multipart parts, 2 or 3 required", nparts)
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}
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p0 := part.Parts[0]
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if !(p0.MediaType == "" && p0.MediaSubType == "") && !(p0.MediaType == "TEXT" && p0.MediaSubType == "PLAIN") {
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return nil, nil, fmt.Errorf(`invalid dsn, first part has content-type %q, must have "text/plain"`, strings.ToLower(p0.MediaType+"/"+p0.MediaSubType))
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}
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p1 := part.Parts[1]
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var m *Message
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if !(p1.MediaType == "MESSAGE" && (p1.MediaSubType == "DELIVERY-STATUS" || p1.MediaSubType == "GLOBAL-DELIVERY-STATUS")) {
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return nil, nil, fmt.Errorf(`invalid dsn, second part has content-type %q, must have "message/delivery-status" or "message/global-delivery-status"`, strings.ToLower(p1.MediaType+"/"+p1.MediaSubType))
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}
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utf8 := p1.MediaSubType == "GLOBAL-DELIVERY-STATUS"
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m, err = Decode(p1.Reader(), utf8)
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if err != nil {
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return nil, nil, fmt.Errorf("parsing dsn delivery-status part: %v", err)
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}
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addressPath := func(a message.Address) (smtp.Path, error) {
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d, err := dns.ParseDomain(a.Host)
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if err != nil {
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return smtp.Path{}, fmt.Errorf("parsing domain: %v", err)
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}
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return smtp.Path{Localpart: smtp.Localpart(a.User), IPDomain: dns.IPDomain{Domain: d}}, nil
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}
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if len(part.Envelope.From) == 1 {
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m.From, err = addressPath(part.Envelope.From[0])
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if err != nil {
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return nil, nil, fmt.Errorf("parsing From-header: %v", err)
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}
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}
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if len(part.Envelope.To) == 1 {
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m.To, err = addressPath(part.Envelope.To[0])
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if err != nil {
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return nil, nil, fmt.Errorf("parsing To-header: %v", err)
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}
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}
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m.Subject = part.Envelope.Subject
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buf, err := io.ReadAll(p0.Reader())
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if err != nil {
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return nil, nil, fmt.Errorf("reading human-readable text part: %v", err)
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}
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m.TextBody = strings.ReplaceAll(string(buf), "\r\n", "\n")
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if nparts == 2 {
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return m, &part, nil
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}
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p2 := part.Parts[2]
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ct := strings.ToLower(p2.MediaType + "/" + p2.MediaSubType)
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switch ct {
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case "text/rfc822-headers":
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case "message/global-headers":
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case "message/rfc822":
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case "message/global":
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default:
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return nil, nil, fmt.Errorf("invalid content-type %q for optional third part with original message/headers", ct)
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}
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return m, &part, nil
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}
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// Decode parses the (global) delivery-status part of a DSN.
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//
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// utf8 indicates if UTF-8 is allowed for this message, if used by the media
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// subtype of the message parts.
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func Decode(r io.Reader, utf8 bool) (*Message, error) {
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m := Message{SMTPUTF8: utf8}
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// We are using textproto.Reader to read mime headers. It requires a header section ending in \r\n.
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// ../rfc/3464:486
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b := bufio.NewReader(io.MultiReader(r, strings.NewReader("\r\n")))
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mr := textproto.NewReader(b)
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// Read per-message lines.
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// ../rfc/3464:1522 ../rfc/6533:366
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msgh, err := mr.ReadMIMEHeader()
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if err != nil {
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return nil, fmt.Errorf("reading per-message lines: %v", err)
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}
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for k, l := range msgh {
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if len(l) != 1 {
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return nil, fmt.Errorf("multiple values for %q: %v", k, l)
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}
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v := l[0]
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// note: headers are in canonical form, as parsed by textproto.
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switch k {
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case "Original-Envelope-Id":
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m.OriginalEnvelopeID = v
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case "Reporting-Mta":
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mta, err := parseMTA(v, utf8)
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if err != nil {
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return nil, fmt.Errorf("parsing reporting-mta: %v", err)
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}
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m.ReportingMTA = mta
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case "Dsn-Gateway":
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mta, err := parseMTA(v, utf8)
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if err != nil {
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return nil, fmt.Errorf("parsing dsn-gateway: %v", err)
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}
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m.DSNGateway = mta
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case "Received-From-Mta":
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mta, err := parseMTA(v, utf8)
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if err != nil {
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return nil, fmt.Errorf("parsing received-from-mta: %v", err)
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}
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d, err := dns.ParseDomain(mta)
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if err != nil {
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return nil, fmt.Errorf("parsing received-from-mta domain %q: %v", mta, err)
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}
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m.ReceivedFromMTA = smtp.Ehlo{Name: dns.IPDomain{Domain: d}}
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case "Arrival-Date":
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tm, err := parseDateTime(v)
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if err != nil {
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return nil, fmt.Errorf("parsing arrival-date: %v", err)
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}
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m.ArrivalDate = tm
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default:
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// We'll assume it is an extension field, we'll ignore it for now.
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}
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}
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m.MessageHeader = msgh
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required := []string{"Reporting-Mta"}
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for _, req := range required {
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if _, ok := msgh[req]; !ok {
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return nil, fmt.Errorf("missing required recipient field %q", req)
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}
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}
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rh, err := parseRecipientHeader(mr, utf8)
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if err != nil {
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return nil, fmt.Errorf("reading per-recipient header: %v", err)
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}
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m.Recipients = []Recipient{rh}
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for {
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if _, err := b.Peek(1); err == io.EOF {
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break
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}
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rh, err := parseRecipientHeader(mr, utf8)
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if err != nil {
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return nil, fmt.Errorf("reading another per-recipient header: %v", err)
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}
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m.Recipients = append(m.Recipients, rh)
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}
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return &m, nil
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}
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// ../rfc/3464:1530 ../rfc/6533:370
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func parseRecipientHeader(mr *textproto.Reader, utf8 bool) (Recipient, error) {
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var r Recipient
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h, err := mr.ReadMIMEHeader()
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if err != nil {
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return Recipient{}, err
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}
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for k, l := range h {
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if len(l) != 1 {
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return Recipient{}, fmt.Errorf("multiple values for %q: %v", k, l)
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}
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v := l[0]
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// note: headers are in canonical form, as parsed by textproto.
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var err error
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switch k {
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case "Original-Recipient":
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r.OriginalRecipient, err = parseAddress(v, utf8)
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case "Final-Recipient":
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r.FinalRecipient, err = parseAddress(v, utf8)
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case "Action":
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a := Action(strings.ToLower(v))
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actions := []Action{Failed, Delayed, Delivered, Relayed, Expanded}
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var ok bool
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for _, x := range actions {
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if a == x {
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ok = true
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break
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}
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}
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if !ok {
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err = fmt.Errorf("unrecognized action %q", v)
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}
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case "Status":
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// todo: parse the enhanced status code?
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r.Status = v
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case "Remote-Mta":
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r.RemoteMTA = NameIP{Name: v}
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case "Diagnostic-Code":
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// ../rfc/3464:518
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t := strings.SplitN(v, ";", 2)
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dt := strings.TrimSpace(t[0])
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if strings.ToLower(dt) != "smtp" {
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err = fmt.Errorf("unknown diagnostic-type %q, expected smtp", dt)
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} else if len(t) != 2 {
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err = fmt.Errorf("missing semicolon to separate diagnostic-type from code")
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} else {
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r.DiagnosticCode = strings.TrimSpace(t[1])
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}
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case "Last-Attempt-Date":
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r.LastAttemptDate, err = parseDateTime(v)
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case "Final-Log-Id":
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r.FinalLogID = v
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case "Will-Retry-Until":
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tm, err := parseDateTime(v)
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if err == nil {
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r.WillRetryUntil = &tm
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}
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default:
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// todo future: parse localized diagnostic text field?
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// We'll assume it is an extension field, we'll ignore it for now.
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}
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if err != nil {
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return Recipient{}, fmt.Errorf("parsing field %q %q: %v", k, v, err)
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}
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}
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required := []string{"Final-Recipient", "Action", "Status"}
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for _, req := range required {
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if _, ok := h[req]; !ok {
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return Recipient{}, fmt.Errorf("missing required recipient field %q", req)
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}
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}
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r.Header = h
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return r, nil
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}
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// ../rfc/3464:525
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func parseMTA(s string, utf8 bool) (string, error) {
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s = removeComments(s)
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t := strings.SplitN(s, ";", 2)
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if len(t) != 2 {
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return "", fmt.Errorf("missing semicolon that splits type and name")
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}
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k := strings.TrimSpace(t[0])
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if !strings.EqualFold(k, "dns") {
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return "", fmt.Errorf("unknown type %q, expected dns", k)
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}
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return strings.TrimSpace(t[1]), nil
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}
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func parseDateTime(s string) (time.Time, error) {
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s = removeComments(s)
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return time.Parse(message.RFC5322Z, s)
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}
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func parseAddress(s string, utf8 bool) (smtp.Path, error) {
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s = removeComments(s)
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t := strings.SplitN(s, ";", 2)
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// ../rfc/3464:513 ../rfc/6533:250
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addrType := strings.ToLower(strings.TrimSpace(t[0]))
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if len(t) != 2 {
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return smtp.Path{}, fmt.Errorf("missing semicolon that splits address type and address")
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} else if addrType == "utf-8" {
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if !utf8 {
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return smtp.Path{}, fmt.Errorf("utf-8 address type for non-utf-8 dsn")
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}
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} else if addrType != "rfc822" {
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return smtp.Path{}, fmt.Errorf("unrecognized address type %q, expected rfc822", addrType)
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}
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s = strings.TrimSpace(t[1])
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if !utf8 {
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for _, c := range s {
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if c > 0x7f {
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return smtp.Path{}, fmt.Errorf("non-ascii without utf-8 enabled")
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}
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}
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}
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// todo: more proper parser
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t = strings.SplitN(s, "@", 2)
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if len(t) != 2 || t[0] == "" || t[1] == "" {
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return smtp.Path{}, fmt.Errorf("invalid email address")
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}
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d, err := dns.ParseDomain(t[1])
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if err != nil {
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return smtp.Path{}, fmt.Errorf("parsing domain: %v", err)
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}
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var lp string
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var esc string
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for _, c := range t[0] {
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if esc == "" && c == '\\' || esc == `\` && (c == 'x' || c == 'X') || esc == `\x` && c == '{' {
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if c == 'X' {
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c = 'x'
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}
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esc += string(c)
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} else if strings.HasPrefix(esc, `\x{`) {
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if c == '}' {
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c, err := strconv.ParseInt(esc[3:], 16, 32)
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if err != nil {
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return smtp.Path{}, fmt.Errorf("parsing localpart with hexpoint: %v", err)
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}
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lp += string(rune(c))
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esc = ""
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} else {
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esc += string(c)
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}
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} else {
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lp += string(c)
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}
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}
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if esc != "" {
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return smtp.Path{}, fmt.Errorf("parsing localpart: unfinished embedded unicode char")
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}
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p := smtp.Path{Localpart: smtp.Localpart(lp), IPDomain: dns.IPDomain{Domain: d}}
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return p, nil
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}
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func removeComments(s string) string {
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n := 0
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r := ""
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for _, c := range s {
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if c == '(' {
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n++
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} else if c == ')' && n > 0 {
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n--
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} else if n == 0 {
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r += string(c)
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}
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}
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return r
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}
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