mirror of
https://github.com/mjl-/mox.git
synced 2024-12-26 08:23:48 +03:00
87 lines
2.8 KiB
Go
87 lines
2.8 KiB
Go
// Package iprev checks if an IP has a reverse DNS name configured and that the
|
|
// reverse DNS name resolves back to the IP (RFC 8601, Section 3).
|
|
package iprev
|
|
|
|
import (
|
|
"context"
|
|
"errors"
|
|
"fmt"
|
|
"log/slog"
|
|
"net"
|
|
"time"
|
|
|
|
"github.com/mjl-/mox/dns"
|
|
"github.com/mjl-/mox/mlog"
|
|
"github.com/mjl-/mox/stub"
|
|
)
|
|
|
|
var xlog = mlog.New("iprev", nil)
|
|
|
|
var (
|
|
MetricIPRev stub.HistogramVec = stub.HistogramVecIgnore{}
|
|
)
|
|
|
|
// Lookup errors.
|
|
var (
|
|
ErrNoRecord = errors.New("iprev: no reverse dns record")
|
|
ErrDNS = errors.New("iprev: dns lookup") // Temporary error.
|
|
)
|
|
|
|
// ../rfc/8601:1082
|
|
|
|
// Status is the result of a lookup.
|
|
type Status string
|
|
|
|
const (
|
|
StatusPass Status = "pass" // Reverse and forward lookup results were in agreement.
|
|
StatusFail Status = "fail" // Reverse and forward lookup results were not in agreement, but at least the reverse name does exist.
|
|
StatusTemperror Status = "temperror" // Temporary error, e.g. DNS timeout.
|
|
StatusPermerror Status = "permerror" // Permanent error and later retry is unlikely to succeed. E.g. no PTR record.
|
|
)
|
|
|
|
// Lookup checks whether an IP has a proper reverse & forward
|
|
// DNS configuration. I.e. that it is explicitly associated with its domain name.
|
|
//
|
|
// A PTR lookup is done on the IP, resulting in zero or more names. These names are
|
|
// forward resolved (A or AAAA) until the original IP address is found. The first
|
|
// matching name is returned as "name". All names, matching or not, are returned as
|
|
// "names".
|
|
//
|
|
// If a temporary error occurred, rerr is set.
|
|
func Lookup(ctx context.Context, resolver dns.Resolver, ip net.IP) (rstatus Status, name string, names []string, authentic bool, rerr error) {
|
|
log := xlog.WithContext(ctx)
|
|
start := time.Now()
|
|
defer func() {
|
|
MetricIPRev.ObserveLabels(float64(time.Since(start))/float64(time.Second), string(rstatus))
|
|
log.Debugx("iprev lookup result", rerr,
|
|
slog.Any("ip", ip),
|
|
slog.Any("status", rstatus),
|
|
slog.Duration("duration", time.Since(start)))
|
|
}()
|
|
|
|
revNames, result, revErr := dns.WithPackage(resolver, "iprev").LookupAddr(ctx, ip.String())
|
|
if dns.IsNotFound(revErr) {
|
|
return StatusPermerror, "", nil, result.Authentic, ErrNoRecord
|
|
} else if revErr != nil {
|
|
return StatusTemperror, "", nil, result.Authentic, fmt.Errorf("%w: %s", ErrDNS, revErr)
|
|
}
|
|
|
|
var lastErr error
|
|
authentic = result.Authentic
|
|
for _, rname := range revNames {
|
|
ips, result, err := dns.WithPackage(resolver, "iprev").LookupIP(ctx, "ip", rname)
|
|
authentic = authentic && result.Authentic
|
|
for _, fwdIP := range ips {
|
|
if ip.Equal(fwdIP) {
|
|
return StatusPass, rname, revNames, authentic, nil
|
|
}
|
|
}
|
|
if err != nil && !dns.IsNotFound(err) {
|
|
lastErr = err
|
|
}
|
|
}
|
|
if lastErr != nil {
|
|
return StatusTemperror, "", revNames, authentic, fmt.Errorf("%w: %s", ErrDNS, lastErr)
|
|
}
|
|
return StatusFail, "", revNames, authentic, nil
|
|
}
|