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nsec3.go
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nsec3.go
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package main
import (
"fmt"
"sort"
"strings"
"github.com/apex/log"
"github.com/miekg/dns"
"github.com/spf13/viper"
)
func checkNSEC3(cache Cache, origin string) (r Result) {
r.Add(checkNSEC3chain(cache, origin))
r.Add(checkNSEC3Labels(cache, origin))
return
}
// checkNSEC3chain checks if all NSEC3 records in the cache are linked into one chain
// and if all NSEC3 records follow the recommendations of RFC 9276
func checkNSEC3chain(cache Cache, origin string) (r Result) {
// get NSEC3PARAM record (needed to check salt)
var nsec3param *dns.NSEC3PARAM
if _, ok := cache[origin]["NSEC3PARAM"]; ok {
nsec3param = cache[origin]["NSEC3PARAM"][0].(*dns.NSEC3PARAM)
} else {
log.Error("No NSEC3PARAM found.")
r.errors
return
}
// extract all labels with an NSEC3 record
nsec3labels := make([]string, 0)
for l := range cache {
if _, ok := cache[l]["NSEC3"]; ok {
nsec3labels = append(nsec3labels, l)
}
}
sort.Strings(nsec3labels)
// check if chain is fully linked
for i := range nsec3labels {
// only one NSEC3 record per label
if len(cache[nsec3labels[i]]["NSEC3"]) != 1 {
log.Errorf("Label %s does have %d NSEC3 records, expected 1\n", nsec3labels[i], len(cache[nsec3labels[i]]["NSEC3"]))
r.errors
continue
}
// index of next label
nextindex := i 1
if nextindex == len(nsec3labels) {
nextindex = 0
}
nsec3 := cache[nsec3labels[i]]["NSEC3"][0].(*dns.NSEC3)
// check NSEC3 record
r.Add(checkNSEC3rr(nsec3, nsec3param))
// check chain
if nsec3.NextDomain "." origin != nsec3labels[nextindex] {
log.Errorf("NSEC3 record for label %s has %s as next domain. expected %s\n", nsec3labels[i], nsec3.NextDomain, nsec3labels[nextindex])
r.errors
}
}
return
}
// checkNSEC3rr checks if a NSEC3 record follows RFC 9276
func checkNSEC3rr(nsec3 *dns.NSEC3, nsec3param *dns.NSEC3PARAM) (r Result) {
// Hash - only allowed value is SHA-1 == 1
if nsec3.Hash != dns.SHA1 {
log.Errorf("Label %s NSEC3 uses an unknown hash algorithm %d. Defined is only SHA-1 (1).\n", nsec3.Header().Name, nsec3.Hash)
r.errors
}
// Only "no flags" or opt-out are defined
if nsec3.Flags != 0 && nsec3.Flags != 1 {
log.Errorf("Label %s NSEC3 has flag field with value %d, allowed are 0 or 1.\n", nsec3.Header().Name, nsec3.Flags)
r.errors
}
// Opt-Out is not recommended, warning can be disabled through config
if !viper.GetBool(NSEC3_OPTOUTOK) && nsec3.Flags&1 == 1 {
log.Warnf("Label %s NSEC3 is using opt-out, opt-out is not recommended.\n", nsec3.Header().Name)
r.warnings
}
// Iterations are recommended to be set to 0
// Iterations above 10 are considered harmful anf might be treated as bogus
// number of max iterations can be changed in config
if int(nsec3.Iterations) > viper.GetInt(NSEC3_MAXITERATIONS) {
log.Errorf("Label %s has NSEC3 iterations of %d, values above %d are possibly treated as bogus .\n", nsec3.Header().Name, nsec3.Iterations, viper.GetInt(NSEC3_MAXITERATIONS))
r.errors
} else if nsec3.Iterations != 0 {
log.Warnf("Label %s has NSEC3 iterations of %d, recommended is 0.\n", nsec3.Header().Name, nsec3.Iterations)
r.warnings
}
// Salt should not be used
if nsec3.SaltLength > 0 || nsec3.Salt != "" {
log.Warnf("Label %s NSEC3 uses salt. Using salt is not recommended.\n", nsec3.Header().Name)
r.warnings
}
// Salt should be same salt as in NSEC3PARAM
if nsec3.Salt != nsec3param.Salt {
log.Errorf("Label %s NSEC3 salt differs from NSEC3PARAM salt. NSEC3 salt: '%s' NSEC3PARAM salt: '%s'\n", nsec3.Header().Name, nsec3.Salt, nsec3param.Salt)
r.errors
}
// done
return
}
type nsec3entity struct {
hash string
originalowner string
flags uint8
temporary bool
delegation bool
hasds bool
types map[string]bool
}
// checkNSEC3Labels checks if all labels that should have an NSEC3 record have one
// Follow RFC 5155 7.1 to compute all labels that need NSEC3 records
func checkNSEC3Labels(cache Cache, origin string) (r Result) {
/*
Follow RFC 5155 7.1 to compute all labels that need NSEC3 records
Step 1:
Select the hash algorithm and the values for salt and iterations.
Hash algorithm, salt and iterations are given in the nsec3param record
*/
var nsec3param *dns.NSEC3PARAM
if _, ok := cache[origin]["NSEC3PARAM"]; ok {
nsec3param = cache[origin]["NSEC3PARAM"][0].(*dns.NSEC3PARAM)
} else {
log.Error("No NSEC3PARAM found.")
r.errors
return
}
/*
Follow RFC 5155 7.1 to compute all labels that need NSEC3 records
Step 2:
For each unique original owner name in the zone add an NSEC3 RR.
* If Opt-Out is being used, owner names of unsigned delegations
MAY be excluded.
* The owner name of the NSEC3 RR is the hash of the original
owner name, prepended as a single label to the zone name.
* The Next Hashed Owner Name field is left blank for the moment.
* If Opt-Out is being used, set the Opt-Out bit to one.
* For collision detection purposes, optionally keep track of the
original owner name with the NSEC3 RR.
* Additionally, for collision detection purposes, optionally
create an additional NSEC3 RR corresponding to the original
owner name with the asterisk label prepended (i.e., as if a
wildcard existed as a child of this owner name) and keep track
of this original owner name. Mark this NSEC3 RR as temporary.
Step 3:
For each RRSet at the original owner name, set the corresponding
bit in the Type Bit Maps field.
*/
uniqueOriginalOwnerName := getUniqueOriginalOwnerName(cache, origin)
nsec3entities := make(map[string][]nsec3entity, 0)
for _, label := range uniqueOriginalOwnerName {
// Opt-out can only be detected when compared to NSEC3 records in zone
_, hasNS := cache[label]["NS"]
_, hasDS := cache[label]["DS"]
labelhash := dns.HashName(label, nsec3param.Hash, nsec3param.Iterations, nsec3param.Salt)
if _, ok := nsec3entities[labelhash]; !ok {
nsec3entities[labelhash] = make([]nsec3entity, 0)
}
entity := nsec3entity{hash: labelhash, originalowner: label, flags: 0, temporary: false, delegation: hasNS, hasds: hasDS, types: make(map[string]bool, 0)}
// This for loop implements step 3
for t := range cache[label] {
if strings.HasPrefix(t, "RRSIG") {
entity.types["RRSIG"] = true
} else {
entity.types[t] = true
}
}
if _, ok := nsec3entities[labelhash]; !ok {
nsec3entities[labelhash] = make([]nsec3entity, 0)
}
nsec3entities[labelhash] = append(nsec3entities[labelhash], entity)
// add temporary wildcard record, if non exists
wildcardlabel := "*." label
wildcardhash := dns.HashName(wildcardlabel, nsec3param.Hash, nsec3param.Iterations, nsec3param.Salt)
if _, ok := nsec3entities[wildcardhash]; !ok {
nsec3entities[wildcardhash] = make([]nsec3entity, 0)
}
nsec3entities[wildcardhash] = append(nsec3entities[wildcardhash], nsec3entity{hash: wildcardhash, originalowner: wildcardlabel, flags: 0, temporary: true, delegation: false, hasds: false})
}
/*
Follow RFC 5155 7.1 to compute all labels that need NSEC3 records
Step 4:
If the difference in number of labels between the apex and the
original owner name is greater than 1, additional NSEC3 RRs need
to be added for every empty non-terminal between the apex and the
original owner name. This process may generate NSEC3 RRs with
duplicate hashed owner names. Optionally, for collision
detection, track the original owner names of these NSEC3 RRs and
create temporary NSEC3 RRs for wildcard collisions in a similar
fashion to step 1.
*/
originlabels := dns.SplitDomainName(origin)
for _, label := range uniqueOriginalOwnerName {
// add additional nsec3 for empty non terminals
labels := dns.SplitDomainName(label)
// no empty non terminals
if len(labels)-len(originlabels) <= 1 {
continue
}
for i := 1; i < len(labels)-len(originlabels); i {
l := strings.Join(labels[i:], ".")
lh := dns.HashName(l, nsec3param.Hash, nsec3param.Iterations, nsec3param.Salt)
// a record exists at the label, no need to insert empty non terminal
if _, ok := nsec3entities[lh]; ok {
continue
} else {
nsec3entities[lh] = make([]nsec3entity, 0)
}
nsec3entities[lh] = append(nsec3entities[lh], nsec3entity{hash: lh, originalowner: l, flags: 0, temporary: false, delegation: false, hasds: false})
wl := "*." l
wlh := dns.HashName(wl, nsec3param.Hash, nsec3param.Iterations, nsec3param.Salt)
if _, ok := nsec3entities[wlh]; !ok {
nsec3entities[wlh] = make([]nsec3entity, 0)
}
nsec3entities[lh] = append(nsec3entities[wlh], nsec3entity{hash: wlh, originalowner: wl, flags: 0, temporary: true, delegation: false, hasds: false})
}
}
/*
Follow RFC 5155 7.1 to compute all labels that need NSEC3 records
Step 5:
Sort the set of NSEC3 RRs into hash order.
Because we use a map, all records are already combined in hash order
nothing to do
*/
/*
Follow RFC 5155 7.1 to compute all labels that need NSEC3 records
Step 6:
Combine NSEC3 RRs with identical hashed owner names by replacing
them with a single NSEC3 RR with the Type Bit Maps field
consisting of the union of the types represented by the set of
NSEC3 RRs. If the original owner name was tracked, then
collisions may be detected when combining, as all of the matching
NSEC3 RRs should have the same original owner name. Discard any
possible temporary NSEC3 RRs.
We do thingsin order of
- collision detection
- delete all temporary nsec3 data
- combine should be unnecessary, but we do check
*/
for label := range nsec3entities {
// collision detection
if len(nsec3entities[label]) == 1 {
for i := 1; i < len(nsec3entities[label]); i {
if nsec3entities[label][0].originalowner != nsec3entities[label][i].originalowner {
if viper.GetInt("verbose") > 0 {
fmt.Printf("NSEC3 abel %s has a collision, owners: %s %s", label, nsec3entities[label][0].originalowner, nsec3entities[label][i].originalowner)
}
r.errors
}
}
}
// delete all temporary nsec3 data
i := 0
for {
if nsec3entities[label][i].temporary {
nsec3entities[label] = append(nsec3entities[label][:i], nsec3entities[label][i 1:]...)
if len(nsec3entities[label]) == 0 {
break
}
i--
}
i
if i >= len(nsec3entities[label]) {
break
}
}
if len(nsec3entities[label]) == 0 {
delete(nsec3entities, label)
continue
}
// combine should be unnecessary, but we do check
if len(nsec3entities[label]) > 1 {
if viper.GetInt("verbose") > 0 {
fmt.Printf("Label %s originalowner %s has %d nsec3 rr.\n", label, nsec3entities[label][0].originalowner, len(nsec3entities[label]))
}
for i = 1; i < len(nsec3entities[label]); i {
if nsec3entities[label][i].hasds {
nsec3entities[label][0].hasds = true
}
if nsec3entities[label][i].delegation {
nsec3entities[label][0].delegation = true
}
for t := range nsec3entities[label][i].types {
nsec3entities[label][0].types[t] = true
}
}
}
}
/*
Follow RFC 5155 7.1 to compute all labels that need NSEC3 records
Step 7 and 8:
Not needed for our purposes
*/
return
}
func getUniqueOriginalOwnerName(cache Cache, origin string) (uniqueOriginalOwnerName []string) {
// clear text labels which should have an nsec3 record
uniqueOriginalOwnerName = make([]string, 0)
for label := range cache {
// out of zone data should have no nsec records
if !strings.HasSuffix(label, origin) {
continue
}
// origin must have nsec records
if label == origin {
uniqueOriginalOwnerName = append(uniqueOriginalOwnerName, label)
continue
}
/*
ONLY IN ZONE LABELS BELOW
*/
// if the name is a delegation point it has nsec
if _, ok := cache[label]["NS"]; ok {
uniqueOriginalOwnerName = append(uniqueOriginalOwnerName, label)
continue
}
if isDelegated(label, cache, origin) {
// glue, no nsec3
continue
}
// NSEC3 records do not get NSEC records
if _, ok := cache[label]["NSEC3"]; ok {
nsec3only := true
for l := range cache[label] {
if l != "NSEC3" && l != "RRSIGNSEC3" {
nsec3only = false
break
}
}
if nsec3only {
// no nsec3
continue
}
}
uniqueOriginalOwnerName = append(uniqueOriginalOwnerName, label)
continue
}
return
}