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https://github.com/mjl-/mox.git
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84 lines
2.3 KiB
Go
84 lines
2.3 KiB
Go
package tlsrpt
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import (
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"context"
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"errors"
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"fmt"
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"log/slog"
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"time"
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"github.com/mjl-/mox/dns"
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"github.com/mjl-/mox/mlog"
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"github.com/mjl-/mox/stub"
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)
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var (
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MetricLookup stub.HistogramVec = stub.HistogramVecIgnore{}
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)
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var (
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ErrNoRecord = errors.New("tlsrpt: no tlsrpt dns txt record")
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ErrMultipleRecords = errors.New("tlsrpt: multiple tlsrpt records") // Must be treated as if domain does not implement TLSRPT.
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ErrDNS = errors.New("tlsrpt: temporary error")
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ErrRecordSyntax = errors.New("tlsrpt: record syntax error")
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)
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// Lookup looks up a TLSRPT DNS TXT record for domain at "_smtp._tls.<domain>" and
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// parses it.
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func Lookup(ctx context.Context, elog *slog.Logger, resolver dns.Resolver, domain dns.Domain) (rrecord *Record, rtxt string, rerr error) {
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log := mlog.New("tlsrpt", elog)
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start := time.Now()
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defer func() {
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result := "ok"
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if rerr != nil {
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if errors.Is(rerr, ErrNoRecord) {
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result = "notfound"
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} else if errors.Is(rerr, ErrMultipleRecords) {
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result = "multiple"
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} else if errors.Is(rerr, ErrDNS) {
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result = "temperror"
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} else if errors.Is(rerr, ErrRecordSyntax) {
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result = "malformed"
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} else {
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result = "error"
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}
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}
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MetricLookup.ObserveLabels(float64(time.Since(start))/float64(time.Second), result)
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log.Debugx("tlsrpt lookup result", rerr,
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slog.Any("domain", domain),
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slog.Any("record", rrecord),
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slog.Duration("duration", time.Since(start)))
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}()
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name := "_smtp._tls." + domain.ASCII + "."
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txts, _, err := dns.WithPackage(resolver, "tlsrpt").LookupTXT(ctx, name)
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if dns.IsNotFound(err) {
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return nil, "", ErrNoRecord
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} else if err != nil {
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return nil, "", fmt.Errorf("%w: %s", ErrDNS, err)
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}
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var text string
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var record *Record
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for _, txt := range txts {
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r, istlsrpt, err := ParseRecord(txt)
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if !istlsrpt {
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// This is a loose but probably reasonable interpretation of ../rfc/8460:375 which
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// wants us to discard otherwise valid records that start with e.g. "v=TLSRPTv1 ;"
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// (note the space before the ";") when multiple TXT records were returned.
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continue
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}
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if err != nil {
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return nil, "", fmt.Errorf("parsing record: %w", err)
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}
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if record != nil {
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return nil, "", ErrMultipleRecords
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}
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record = r
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text = txt
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}
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if record == nil {
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return nil, "", ErrNoRecord
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}
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return record, text, nil
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}
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