Add middleware reverse (#452)

This commit is contained in:
Richard Hillmann 2017-02-09 20:39:48 +01:00 committed by Miek Gieben
parent a7c9fd5d6b
commit 61afc6dbad
9 changed files with 804 additions and 0 deletions

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@ -25,6 +25,7 @@ import (
_ "github.com/miekg/coredns/middleware/metrics"
_ "github.com/miekg/coredns/middleware/pprof"
_ "github.com/miekg/coredns/middleware/proxy"
_ "github.com/miekg/coredns/middleware/reverse"
_ "github.com/miekg/coredns/middleware/rewrite"
_ "github.com/miekg/coredns/middleware/root"
_ "github.com/miekg/coredns/middleware/secondary"

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@ -29,6 +29,7 @@ var directives = []string{
"secondary",
"etcd",
"kubernetes",
"reverse",
"proxy",
"httpprox",
"whoami",

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@ -37,6 +37,7 @@
160:secondary:
170:etcd:
180:kubernetes:
185:reverse:
190:proxy:
200:httpprox:
210:whoami:

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@ -0,0 +1,97 @@
# reverse
The *reverse* middleware allows CoreDNS to respond dynamic to an PTR request and the related A/AAAA request.
## Syntax
~~~
reverse NETWORK.. {
hostname TEMPLATE
[ttl TTL]
[fallthrough]
~~~
* **NETWORK** one or more CIDR formatted networks to respond on.
* `hostname` inject the ip and zone to an template for the hostname. Defaults to "ip-{ip}.{zone[0]}". See below for template.
* `ttl` defaults to 60
* `fallthrough` If zone matches and no record can be generated, pass request to the next middleware.
### Template Syntax
The template for the hostname is used for generating the PTR for an reverse lookup and matching the forward lookup back to an ip.
#### `{ip}`
This symbol is **required** to work.
V4 network replaces the "." with an "-". 10.1.1.1 results in "10-1-1-1"
V6 network removes the ":" and fills the zeros. "ffff::ffff" results in "ffff000000000000000000000000ffff"
#### `{zone[i]}`
This symbol is **optional** to use and can be replaced by a fix zone string.
The zone will be matched by the configured listener on the server block key.
`i` needs to be replaced to the index of the configured listener zones, starting with 0.
`arpa.:53 domain.com.:8053` will resolve `zone{0}` to `arpa.` and `zone{1}` to `domain.com.`
## Examples
~~~
# Serve on port 53
# match arpa. and compute.internal. to resolv reverse and forward lookup
.arpa.:53 compute.internal.:53 {
# proxy unmatched requests
proxy . 8.8.8.8
# answer requests for IPs in this networks
# PTR 1.0.32.10.in-addr.arpa. 3600 ip-10-0-32-1.compute.internal.
# A ip-10-0-32-1.compute.internal. 3600 10.0.32.1
# v6 is also possible
# PTR 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.d.f.ip6.arpa. 3600 ip-fd010000000000000000000000000001.compute.internal.
# AAAA ip-fd010000000000000000000000000001.compute.internal. 3600 fd01::1
reverse 10.32.0.0/16 fd01::/16 {
# template of the ip injection to hostname, zone resolved to compute.internal.
hostname ip-{ip}.{zone[1]}
# set time-to-live of the RR
ttl 3600
# forward unanswered or unmatched requests to proxy
# without this flag, requesting A/AAAA records on compute.internal. will end here
fallthrough
}
# cache with ttl timeout
cache
}
~~~
~~~
# Serve on port 53
# listen only on the specific network
32.10.in-addr.arpa.arpa.:53 arpa.company.org.:53 {
reverse 10.32.0.0/16 {
# template of the ip injection to hostname, zone resolved to arpa.company.org.
hostname "ip-{ip}.v4.{zone[1]}"
# set time-to-live of the RR
ttl 3600
# fallthrough is not required, v4.arpa.company.org. will be only answered here
}
# cidr closer to the ip wins, so we can overwrite the "default"
reverse 10.32.2.0/24 {
# its also possible to set fix domain suffix
hostname ip-{ip}.fix.arpa.company.org.
# set time-to-live of the RR
ttl 3600
}
# cache with ttl timeout
cache
}
~~~

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@ -0,0 +1,123 @@
package reverse
import (
"net"
"regexp"
"bytes"
"strings"
)
type network struct {
IPnet *net.IPNet
Zone string // forward lookup zone
Template string
TTL uint32
RegexMatchIP *regexp.Regexp
Fallthrough bool
}
const hexDigit = "0123456789abcdef"
const templateNameIP = "{ip}"
const regexMatchV4 = "((?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\-){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))"
const regexMatchV6 = "([0-9a-fA-F]{32})"
// For forward lookup
// converts the hostname back to an ip, based on the template
// returns nil if there is no ip found
func (network *network) hostnameToIP(rname string) net.IP {
var matchedIP net.IP
// use precompiled regex by setup
match := network.RegexMatchIP.FindStringSubmatch(rname)
// regex did not matched
if (len(match) != 2) {
return nil
}
if network.IPnet.IP.To4() != nil {
matchedIP = net.ParseIP(strings.Replace(match[1], "-", ".", 4))
} else {
var buf bytes.Buffer
// convert back to an valid ipv6 string with colons
for i := 0; i < 8 * 4; i += 4 {
buf.WriteString(match[1][i:i + 4])
if (i < 28) {
buf.WriteString(":")
}
}
matchedIP = net.ParseIP(buf.String())
}
// No valid ip or it does not belong to this network
if matchedIP == nil || !network.IPnet.Contains(matchedIP) {
return nil
}
return matchedIP
}
// For reverse lookup
// Converts an Ip to an dns compatible hostname and injects it into the template.domain
func (network *network) ipToHostname(ip net.IP) string {
var name string
ipv4 := ip.To4()
if ipv4 != nil {
// replace . to -
name = uitoa(ipv4[0]) + "-" +
uitoa(ipv4[1]) + "-" +
uitoa(ipv4[2]) + "-" +
uitoa(ipv4[3])
} else {
// assume v6
// ensure zeros are present in string
buf := make([]byte, 0, len(ip) * 4)
for i := 0; i < len(ip); i++ {
v := ip[i]
buf = append(buf, hexDigit[v >> 4])
buf = append(buf, hexDigit[v & 0xF])
}
name = string(buf)
}
// inject the converted ip into the fqdn template
return strings.Replace(network.Template, templateNameIP, name, 1)
}
// just the same from net.ip package, but with uint8
func uitoa(val uint8) string {
if val == 0 {
// avoid string allocation
return "0"
}
var buf [20]byte // big enough for 64bit value base 10
i := len(buf) - 1
for val >= 10 {
q := val / 10
buf[i] = byte('0' + val - q * 10)
i--
val = q
}
// val < 10
buf[i] = byte('0' + val)
return string(buf[i:])
}
type networks []network
// implements the sort interface
func (slice networks) Len() int {
return len(slice)
}
// implements the sort interface
// cidr closer to the ip wins (by netmask)
func (slice networks) Less(i, j int) bool {
isize, _ := slice[i].IPnet.Mask.Size()
jsize, _ := slice[j].IPnet.Mask.Size()
return isize > jsize
}
// implements the sort interface
func (slice networks) Swap(i, j int) {
slice[i], slice[j] = slice[j], slice[i]
}

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@ -0,0 +1,135 @@
package reverse
import (
"testing"
"net"
"reflect"
"regexp"
)
// Test converting from hostname to IP and back again to hostname
func TestNetworkConversion(t *testing.T) {
_, net4, _ := net.ParseCIDR("10.1.1.0/24")
_, net6, _ := net.ParseCIDR("fd01::/64")
regexIP4, _ := regexp.Compile("^dns-" + regexMatchV4 + "\\.domain\\.internal\\.$")
regexIP6, _ := regexp.Compile("^dns-" + regexMatchV6 + "\\.domain\\.internal\\.$")
tests := []struct {
network network
resultHost string
resultIP net.IP
}{
{
network{
IPnet:net4,
Template: "dns-{ip}.domain.internal.",
RegexMatchIP:regexIP4,
},
"dns-10-1-1-23.domain.internal.",
net.ParseIP("10.1.1.23"),
},
{
network{
IPnet:net6,
Template: "dns-{ip}.domain.internal.",
RegexMatchIP:regexIP6,
},
"dns-fd01000000000000000000000000a32f.domain.internal.",
net.ParseIP("fd01::a32f"),
},
}
for i, test := range tests {
resultIP := test.network.hostnameToIP(test.resultHost)
if !reflect.DeepEqual(test.resultIP, resultIP) {
t.Fatalf("Test %d expected %v, got %v", i, test.resultIP, resultIP)
}
resultHost := test.network.ipToHostname(test.resultIP)
if !reflect.DeepEqual(test.resultHost, resultHost) {
t.Fatalf("Test %d expected %v, got %v", i, test.resultHost, resultHost)
}
}
}
func TestNetworkHostnameToIP(t *testing.T) {
_, net4, _ := net.ParseCIDR("10.1.1.0/24")
_, net6, _ := net.ParseCIDR("fd01::/64")
regexIP4, _ := regexp.Compile("^dns-" + regexMatchV4 + "\\.domain\\.internal\\.$")
regexIP6, _ := regexp.Compile("^dns-" + regexMatchV6 + "\\.domain\\.internal\\.$")
// Test regex does NOT match
// All this test should return nil
testsNil := []struct {
network network
hostname string
}{
{
network{
IPnet:net4,
RegexMatchIP:regexIP4,
},
// domain does not match
"dns-10-1-1-23.domain.internals.",
},
{
network{
IPnet:net4,
RegexMatchIP:regexIP4,
},
// IP does match / contain in subnet
"dns-200-1-1-23.domain.internals.",
},
{
network{
IPnet:net4,
RegexMatchIP:regexIP4,
},
// template does not match
"dns-10-1-1-23-x.domain.internal.",
},
{
network{
IPnet:net4,
RegexMatchIP:regexIP4,
},
// template does not match
"IP-dns-10-1-1-23.domain.internal.",
},
{
network{
IPnet:net6,
RegexMatchIP:regexIP6,
},
// template does not match
"dnx-fd01000000000000000000000000a32f.domain.internal.",
},
{
network{
IPnet:net6,
RegexMatchIP:regexIP6,
},
// no valid v6 (missing one 0, only 31 chars)
"dns-fd0100000000000000000000000a32f.domain.internal.",
},
{
network{
IPnet:net6,
RegexMatchIP:regexIP6,
},
// IP does match / contain in subnet
"dns-ed01000000000000000000000000a32f.domain.internal.",
},
}
for i, test := range testsNil {
resultIP := test.network.hostnameToIP(test.hostname)
if resultIP != nil {
t.Fatalf("Test %d expected nil, got %v", i, resultIP)
}
}
}

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@ -0,0 +1,114 @@
package reverse
import (
"net"
"github.com/miekg/coredns/request"
"github.com/miekg/coredns/middleware"
"github.com/miekg/coredns/middleware/pkg/dnsutil"
"github.com/miekg/dns"
"golang.org/x/net/context"
)
// Reverse provides dynamic reverse dns and the related forward rr
type Reverse struct {
Next middleware.Handler
Networks networks
}
// ServeDNS implements the middleware.Handler interface.
func (reverse Reverse) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
var rr dns.RR
nextHandler := true
state := request.Request{W: w, Req: r}
m := new(dns.Msg)
m.SetReply(r)
m.Authoritative, m.RecursionAvailable, m.Compress = true, true, true
switch state.QType(){
case dns.TypePTR:
address := dnsutil.ExtractAddressFromReverse(state.Name())
if address == "" {
// Not an reverse lookup, but can still be an pointer for an domain
break
}
ip := net.ParseIP(address)
// loop through the configured networks
for _, n := range reverse.Networks {
if (n.IPnet.Contains(ip)) {
nextHandler = n.Fallthrough
rr = &dns.PTR{
Hdr: dns.RR_Header{Name: state.QName(), Rrtype: dns.TypePTR, Class: dns.ClassINET, Ttl: n.TTL},
Ptr: n.ipToHostname(ip),
}
break
}
}
case dns.TypeA:
for _, n := range reverse.Networks {
if dns.IsSubDomain(n.Zone, state.Name()) {
nextHandler = n.Fallthrough
// skip if requesting an v4 address and network is not v4
if n.IPnet.IP.To4() == nil {
continue
}
result := n.hostnameToIP(state.Name())
if result != nil {
rr = &dns.A{
Hdr: dns.RR_Header{Name: state.QName(), Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: n.TTL},
A: result,
}
break
}
}
}
case dns.TypeAAAA:
for _, n := range reverse.Networks {
if dns.IsSubDomain(n.Zone, state.Name()) {
nextHandler = n.Fallthrough
// Do not use To16 which tries to make v4 in v6
if n.IPnet.IP.To4() != nil {
continue
}
result := n.hostnameToIP(state.Name())
if result != nil {
rr = &dns.AAAA{
Hdr: dns.RR_Header{Name: state.QName(), Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: n.TTL},
AAAA: result,
}
break
}
}
}
}
if rr == nil {
if reverse.Next == nil || !nextHandler {
// could not resolv
w.WriteMsg(m)
return dns.RcodeNameError, nil
}
return reverse.Next.ServeDNS(ctx, w, r)
}
m.Answer = append(m.Answer, rr)
state.SizeAndDo(m)
w.WriteMsg(m)
return dns.RcodeSuccess, nil
}
// Name implements the Handler interface.
func (reverse Reverse) Name() string {
return "reverse"
}

146
middleware/reverse/setup.go Normal file
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@ -0,0 +1,146 @@
package reverse
import (
"net"
"sort"
"strings"
"strconv"
"regexp"
"github.com/miekg/coredns/core/dnsserver"
"github.com/miekg/coredns/middleware"
"github.com/mholt/caddy"
)
func init() {
caddy.RegisterPlugin("reverse", caddy.Plugin{
ServerType: "dns",
Action: setupReverse,
})
}
func setupReverse(c *caddy.Controller) error {
networks, err := reverseParse(c)
if err != nil {
return middleware.Error("reverse", err)
}
dnsserver.GetConfig(c).AddMiddleware(func(next middleware.Handler) middleware.Handler {
return Reverse{Next: next, Networks:networks}
})
return nil
}
func reverseParse(c *caddy.Controller) (networks, error) {
var err error
// normalize zones, validation is almost done by dnsserver
zones := make([]string, len(c.ServerBlockKeys))
for i, str := range c.ServerBlockKeys {
host, _, _ := net.SplitHostPort(str)
zones[i] = strings.ToLower(host)
}
networks := networks{}
for c.Next() {
if c.Val() == "reverse" {
var cidrs []*net.IPNet
// parse all networks
for _, cidr := range c.RemainingArgs() {
if cidr == "{" {
break
}
_, ipnet, err := net.ParseCIDR(cidr)
if err != nil {
return nil, c.Errf("%v needs to be an CIDR formatted Network\n", cidr)
}
cidrs = append(cidrs, ipnet)
}
if len(cidrs) == 0 {
return nil, c.ArgErr()
}
// set defaults
var (
template = "ip-" + templateNameIP + ".{zone[0]}"
ttl = 60
fall = false
)
for c.NextBlock() {
switch c.Val() {
case "hostname":
if !c.NextArg() {
return nil, c.ArgErr()
}
template = c.Val()
case "ttl":
if !c.NextArg() {
return nil, c.ArgErr()
}
ttl, err = strconv.Atoi(c.Val())
if err != nil {
return nil, err
}
case "fallthrough":
fall = true
default:
return nil, c.ArgErr()
}
}
// prepare template
// replace {zone[index]} by the listen zone/domain of this config block
for i, zone := range zones {
template = strings.Replace(template, "{zone[" + string(i + 48) + "]}", zone, 1)
}
if !strings.HasSuffix(template, ".") {
template += "."
}
// extract zone from template
templateZone := strings.SplitAfterN(template, ".", 2)
if len(templateZone) != 2 || templateZone[1] == "" {
return nil, c.Errf("Cannot find domain in template '%v'", template)
}
// Create for each configured network in this stanza
for _, ipnet := range cidrs {
// precompile regex for hostname to ip matching
regexIP := regexMatchV4
if ipnet.IP.To4() == nil {
regexIP = regexMatchV6
}
regex, err := regexp.Compile(
"^" + strings.Replace( // inject ip regex into template
regexp.QuoteMeta(template), // escape dots
regexp.QuoteMeta(templateNameIP),
regexIP,
1, ) + "$")
if err != nil {
// invalid regex
return nil, err
}
networks = append(networks, network{
IPnet: ipnet,
Zone: templateZone[1],
Template: template,
RegexMatchIP: regex,
TTL: uint32(ttl),
Fallthrough: fall,
})
}
}
}
// sort by cidr
sort.Sort(networks)
return networks, nil
}

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@ -0,0 +1,186 @@
package reverse
import (
"testing"
"net"
"reflect"
"regexp"
"github.com/mholt/caddy"
)
func TestSetupParse(t *testing.T) {
_, net4, _ := net.ParseCIDR("10.1.1.0/24")
_, net6, _ := net.ParseCIDR("fd01::/64")
regexIP6, _ := regexp.Compile("^ip-" + regexMatchV6 + "\\.domain\\.com\\.$")
regexIpv4dynamic, _ := regexp.Compile("^dynamic-" + regexMatchV4 + "-intern\\.dynamic\\.domain\\.com\\.$")
regexIpv6dynamic, _ := regexp.Compile("^dynamic-" + regexMatchV6 + "-intern\\.dynamic\\.domain\\.com\\.$")
regexIpv4vpndynamic, _ := regexp.Compile("^dynamic-" + regexMatchV4 + "-vpn\\.dynamic\\.domain\\.com\\.$")
serverBlockKeys := []string{"domain.com.:8053", "dynamic.domain.com.:8053" }
tests := []struct {
inputFileRules string
shouldErr bool
networks networks
}{
{
// with defaults
`reverse fd01::/64`,
false,
networks{network{
IPnet: net6,
Template: "ip-{ip}.domain.com.",
Zone: "domain.com.",
TTL: 60,
RegexMatchIP: regexIP6,
Fallthrough: false,
}},
},
{
`reverse`,
true,
networks{},
},
{
//no cidr
`reverse 10.1.1.1`,
true,
networks{},
},
{
//no cidr
`reverse 10.1.1.0/16 fd00::`,
true,
networks{},
},
{
// invalid key
`reverse 10.1.1.0/24 {
notavailable
}`,
true,
networks{},
},
{
// no domain suffix
`reverse 10.1.1.0/24 {
hostname ip-{ip}.
}`,
true,
networks{},
},
{
// hostname requires an second arg
`reverse 10.1.1.0/24 {
hostname
}`,
true,
networks{},
},
{
// template breaks regex compile
`reverse 10.1.1.0/24 {
hostname ip-{[-x
}`,
true,
networks{},
},
{
// ttl requires an (u)int
`reverse 10.1.1.0/24 {
ttl string
}`,
true,
networks{},
},
{
`reverse fd01::/64 {
hostname dynamic-{ip}-intern.{zone[1]}
ttl 50
}
reverse 10.1.1.0/24 {
hostname dynamic-{ip}-vpn.{zone[1]}
fallthrough
}`,
false,
networks{network{
IPnet: net6,
Template: "dynamic-{ip}-intern.dynamic.domain.com.",
Zone: "dynamic.domain.com.",
TTL: 50,
RegexMatchIP:regexIpv6dynamic,
Fallthrough: false,
}, network{
IPnet: net4,
Template: "dynamic-{ip}-vpn.dynamic.domain.com.",
Zone: "dynamic.domain.com.",
TTL: 60,
RegexMatchIP: regexIpv4vpndynamic,
Fallthrough:true,
}},
},
{
// multiple networks in one stanza
`reverse fd01::/64 10.1.1.0/24 {
hostname dynamic-{ip}-intern.{zone[1]}
ttl 50
fallthrough
}`,
false,
networks{network{
IPnet: net6,
Template: "dynamic-{ip}-intern.dynamic.domain.com.",
Zone: "dynamic.domain.com.",
TTL: 50,
RegexMatchIP:regexIpv6dynamic,
Fallthrough: true,
}, network{
IPnet: net4,
Template: "dynamic-{ip}-intern.dynamic.domain.com.",
Zone: "dynamic.domain.com.",
TTL: 50,
RegexMatchIP: regexIpv4dynamic,
Fallthrough: true,
}},
},
{
// fix domain in template
`reverse fd01::/64 {
hostname dynamic-{ip}-intern.dynamic.domain.com
ttl 300
fallthrough
}`,
false,
networks{network{
IPnet: net6,
Template: "dynamic-{ip}-intern.dynamic.domain.com.",
Zone: "dynamic.domain.com.",
TTL: 300,
RegexMatchIP:regexIpv6dynamic,
Fallthrough: true,
}},
},
}
for i, test := range tests {
c := caddy.NewTestController("dns", test.inputFileRules)
c.ServerBlockKeys = serverBlockKeys
networks, err := reverseParse(c)
if err == nil && test.shouldErr {
t.Fatalf("Test %d expected errors, but got no error", i)
} else if err != nil && !test.shouldErr {
t.Fatalf("Test %d expected no errors, but got '%v'", i, err)
} else {
for j, n := range networks {
reflect.DeepEqual(test.networks[j], n)
if !reflect.DeepEqual(test.networks[j], n) {
t.Fatalf("Test %d/%d expected %v, got %v", i, j, test.networks[j], n)
}
}
}
}
}