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package sign
import (
"fmt"
"io"
"os"
"path/filepath"
"time"
"github.com/coredns/coredns/plugin/file"
"github.com/coredns/coredns/plugin/file/tree"
clog "github.com/coredns/coredns/plugin/pkg/log"
"github.com/miekg/dns"
)
var log = clog.NewWithPlugin("sign")
// Signer holds the data needed to sign a zone file.
type Signer struct {
keys []Pair
origin string
dbfile string
directory string
jitterIncep time.Duration
jitterExpir time.Duration
signedfile string
stop chan struct{}
}
// Sign signs a zone file according to the parameters in s.
func (s *Signer) Sign(now time.Time) (*file.Zone, error) {
rd, err := os.Open(s.dbfile)
if err != nil {
return nil, err
}
z, err := Parse(rd, s.origin, s.dbfile)
if err != nil {
return nil, err
}
mttl := z.Apex.SOA.Minttl
ttl := z.Apex.SOA.Header().Ttl
inception, expiration := lifetime(now, s.jitterIncep, s.jitterExpir)
z.Apex.SOA.Serial = uint32(now.Unix())
for _, pair := range s.keys {
pair.Public.Header().Ttl = ttl // set TTL on key so it matches the RRSIG.
z.Insert(pair.Public)
z.Insert(pair.Public.ToDS(dns.SHA1).ToCDS())
z.Insert(pair.Public.ToDS(dns.SHA256).ToCDS())
z.Insert(pair.Public.ToCDNSKEY())
}
names := names(s.origin, z)
ln := len(names)
for _, pair := range s.keys {
rrsig, err := pair.signRRs([]dns.RR{z.Apex.SOA}, s.origin, ttl, inception, expiration)
if err != nil {
return nil, err
}
z.Insert(rrsig)
// NS apex may not be set if RR's have been discarded because the origin doesn't match.
if len(z.Apex.NS) > 0 {
rrsig, err = pair.signRRs(z.Apex.NS, s.origin, ttl, inception, expiration)
if err != nil {
return nil, err
}
z.Insert(rrsig)
}
}
// We are walking the tree in the same direction, so names[] can be used here to indicated the next element.
i := 1
err = z.AuthWalk(func(e *tree.Elem, zrrs map[uint16][]dns.RR, auth bool) error {
if !auth {
return nil
}
if e.Name() == s.origin {
nsec := NSEC(e.Name(), names[(ln+i)%ln], mttl, append(e.Types(), dns.TypeNS, dns.TypeSOA, dns.TypeRRSIG, dns.TypeNSEC))
z.Insert(nsec)
} else {
nsec := NSEC(e.Name(), names[(ln+i)%ln], mttl, append(e.Types(), dns.TypeRRSIG, dns.TypeNSEC))
z.Insert(nsec)
}
for t, rrs := range zrrs {
// RRSIGs are not signed and NS records are not signed because we are never authoratiative for them.
// The zone's apex nameservers records are not kept in this tree and are signed separately.
if t == dns.TypeRRSIG || t == dns.TypeNS {
continue
}
for _, pair := range s.keys {
rrsig, err := pair.signRRs(rrs, s.origin, rrs[0].Header().Ttl, inception, expiration)
if err != nil {
return err
}
e.Insert(rrsig)
}
}
i++
return nil
})
return z, err
}
// resign checks if the signed zone exists, or needs resigning.
func (s *Signer) resign() error {
signedfile := filepath.Join(s.directory, s.signedfile)
rd, err := os.Open(signedfile)
if err != nil && os.IsNotExist(err) {
return err
}
now := time.Now().UTC()
return resign(rd, now)
}
// resign will scan rd and check the signature on the SOA record. We will resign on the basis
// of 2 conditions:
// * either the inception is more than 6 days ago, or
// * we only have 1 week left on the signature
//
// All SOA signatures will be checked. If the SOA isn't found in the first 100
// records, we will resign the zone.
func resign(rd io.Reader, now time.Time) (why error) {
zp := dns.NewZoneParser(rd, ".", "resign")
zp.SetIncludeAllowed(true)
i := 0
for rr, ok := zp.Next(); ok; rr, ok = zp.Next() {
if err := zp.Err(); err != nil {
return err
}
switch x := rr.(type) {
case *dns.RRSIG:
if x.TypeCovered != dns.TypeSOA {
continue
}
incep, _ := time.Parse("20060102150405", dns.TimeToString(x.Inception))
// If too long ago, resign.
if now.Sub(incep) >= 0 && now.Sub(incep) > durationResignDays {
return fmt.Errorf("inception %q was more than: %s ago from %s: %s", incep.Format(timeFmt), durationResignDays, now.Format(timeFmt), now.Sub(incep))
}
// Inception hasn't even start yet.
if now.Sub(incep) < 0 {
return fmt.Errorf("inception %q date is in the future: %s", incep.Format(timeFmt), now.Sub(incep))
}
expire, _ := time.Parse("20060102150405", dns.TimeToString(x.Expiration))
if expire.Sub(now) < durationExpireDays {
return fmt.Errorf("expiration %q is less than: %s away from %s: %s", expire.Format(timeFmt), durationExpireDays, now.Format(timeFmt), expire.Sub(now))
}
}
i++
if i > 100 {
// 100 is a random number. A SOA record should be the first in the zonefile, but RFC 1035 doesn't actually mandate this. So it could
// be 3rd or even later. The number 100 looks crazy high enough that it will catch all weird zones, but not high enough to keep the CPU
// busy with parsing all the time.
return fmt.Errorf("no SOA RRSIG found in first 100 records")
}
}
return nil
}
func signAndLog(s *Signer, why error) {
now := time.Now().UTC()
z, err := s.Sign(now)
log.Infof("Signing %q because %s", s.origin, why)
if err != nil {
log.Warningf("Error signing %q with key tags %q in %s: %s, next: %s", s.origin, keyTag(s.keys), time.Since(now), err, now.Add(durationRefreshHours).Format(timeFmt))
return
}
if err := s.write(z); err != nil {
log.Warningf("Error signing %q: failed to move zone file into place: %s", s.origin, err)
return
}
log.Infof("Successfully signed zone %q in %q with key tags %q and %d SOA serial, elapsed %f, next: %s", s.origin, filepath.Join(s.directory, s.signedfile), keyTag(s.keys), z.Apex.SOA.Serial, time.Since(now).Seconds(), now.Add(durationRefreshHours).Format(timeFmt))
}
// refresh checks every val if some zones need to be resigned.
func (s *Signer) refresh(val time.Duration) {
tick := time.NewTicker(val)
defer tick.Stop()
for {
select {
case <-s.stop:
return
case <-tick.C:
why := s.resign()
if why == nil {
continue
}
signAndLog(s, why)
}
}
}
func lifetime(now time.Time, jitterInception, jitterExpiration time.Duration) (uint32, uint32) {
incep := uint32(now.Add(durationSignatureInceptionHours).Add(jitterInception).Unix())
expir := uint32(now.Add(durationSignatureExpireDays).Add(jitterExpiration).Unix())
return incep, expir
}
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