forked from letsencrypt/boulder
/
dns.go
275 lines (248 loc) · 7.2 KB
/
dns.go
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// Copyright 2015 ISRG. All rights reserved
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
package core
import (
"fmt"
"math/rand"
"net"
"strings"
"time"
"github.com/letsencrypt/boulder/Godeps/_workspace/src/github.com/miekg/dns"
)
var (
// Private CIDRs to ignore
privateNetworks = []net.IPNet{
// RFC1918
// 10.0.0.0/8
net.IPNet{
IP: []byte{10, 0, 0, 0},
Mask: []byte{255, 0, 0, 0},
},
// 172.16.0.0/12
net.IPNet{
IP: []byte{172, 16, 0, 0},
Mask: []byte{255, 240, 0, 0},
},
// 192.168.0.0/16
net.IPNet{
IP: []byte{192, 168, 0, 0},
Mask: []byte{255, 255, 0, 0},
},
// RFC5735
// 127.0.0.0/8
net.IPNet{
IP: []byte{127, 0, 0, 0},
Mask: []byte{255, 0, 0, 0},
},
// RFC1122 Section 3.2.1.3
// 0.0.0.0/8
net.IPNet{
IP: []byte{0, 0, 0, 0},
Mask: []byte{255, 0, 0, 0},
},
// RFC3927
// 169.254.0.0/16
net.IPNet{
IP: []byte{169, 254, 0, 0},
Mask: []byte{255, 255, 0, 0},
},
// RFC 5736
// 192.0.0.0/24
net.IPNet{
IP: []byte{192, 0, 0, 0},
Mask: []byte{255, 255, 255, 0},
},
// RFC 5737
// 192.0.2.0/24
net.IPNet{
IP: []byte{192, 0, 2, 0},
Mask: []byte{255, 255, 255, 0},
},
// 198.51.100.0/24
net.IPNet{
IP: []byte{192, 51, 100, 0},
Mask: []byte{255, 255, 255, 0},
},
// 203.0.113.0/24
net.IPNet{
IP: []byte{203, 0, 113, 0},
Mask: []byte{255, 255, 255, 0},
},
// RFC 3068
// 192.88.99.0/24
net.IPNet{
IP: []byte{192, 88, 99, 0},
Mask: []byte{255, 255, 255, 0},
},
// RFC 2544
// 192.18.0.0/15
net.IPNet{
IP: []byte{192, 18, 0, 0},
Mask: []byte{255, 254, 0, 0},
},
// RFC 3171
// 224.0.0.0/4
net.IPNet{
IP: []byte{224, 0, 0, 0},
Mask: []byte{240, 0, 0, 0},
},
// RFC 1112
// 240.0.0.0/4
net.IPNet{
IP: []byte{240, 0, 0, 0},
Mask: []byte{240, 0, 0, 0},
},
// RFC 919 Section 7
// 255.255.255.255/32
net.IPNet{
IP: []byte{255, 255, 255, 255},
Mask: []byte{255, 255, 255, 255},
},
// RFC 6598
// 100.64.0.0./10
net.IPNet{
IP: []byte{100, 64, 0, 0},
Mask: []byte{255, 192, 0, 0},
},
}
)
// DNSResolverImpl represents a client that talks to an external resolver
type DNSResolverImpl struct {
DNSClient *dns.Client
Servers []string
allowRestrictedAddresses bool
}
// NewDNSResolverImpl constructs a new DNS resolver object that utilizes the
// provided list of DNS servers for resolution.
func NewDNSResolverImpl(readTimeout time.Duration, servers []string) *DNSResolverImpl {
dnsClient := new(dns.Client)
// Set timeout for underlying net.Conn
dnsClient.ReadTimeout = readTimeout
dnsClient.Net = "tcp"
return &DNSResolverImpl{
DNSClient: dnsClient,
Servers: servers,
allowRestrictedAddresses: false,
}
}
// NewTestDNSResolverImpl constructs a new DNS resolver object that utilizes the
// provided list of DNS servers for resolution and will allow loopback addresses.
// This constructor should *only* be called from tests (unit or integration).
func NewTestDNSResolverImpl(readTimeout time.Duration, servers []string) *DNSResolverImpl {
resolver := NewDNSResolverImpl(readTimeout, servers)
resolver.allowRestrictedAddresses = true
return resolver
}
// ExchangeOne performs a single DNS exchange with a randomly chosen server
// out of the server list, returning the response, time, and error (if any).
// This method sets the DNSSEC OK bit on the message to true before sending
// it to the resolver in case validation isn't the resolvers default behaviour.
func (dnsResolver *DNSResolverImpl) ExchangeOne(hostname string, qtype uint16) (rsp *dns.Msg, rtt time.Duration, err error) {
m := new(dns.Msg)
// Set question type
m.SetQuestion(dns.Fqdn(hostname), qtype)
// Set DNSSEC OK bit for resolver
m.SetEdns0(4096, true)
if len(dnsResolver.Servers) < 1 {
err = fmt.Errorf("Not configured with at least one DNS Server")
return
}
// Randomly pick a server
chosenServer := dnsResolver.Servers[rand.Intn(len(dnsResolver.Servers))]
return dnsResolver.DNSClient.Exchange(m, chosenServer)
}
// LookupTXT sends a DNS query to find all TXT records associated with
// the provided hostname.
func (dnsResolver *DNSResolverImpl) LookupTXT(hostname string) ([]string, time.Duration, error) {
var txt []string
r, rtt, err := dnsResolver.ExchangeOne(hostname, dns.TypeTXT)
if err != nil {
return nil, 0, err
}
if r.Rcode != dns.RcodeSuccess {
err = fmt.Errorf("DNS failure: %d-%s for TXT query", r.Rcode, dns.RcodeToString[r.Rcode])
return nil, 0, err
}
for _, answer := range r.Answer {
if answer.Header().Rrtype == dns.TypeTXT {
if txtRec, ok := answer.(*dns.TXT); ok {
txt = append(txt, strings.Join(txtRec.Txt, ""))
}
}
}
return txt, rtt, err
}
func isPrivateV4(ip net.IP) bool {
for _, net := range privateNetworks {
if net.Contains(ip) {
return true
}
}
return false
}
// LookupHost sends a DNS query to find all A records associated with the provided
// hostname. This method assumes that the external resolver will chase CNAME/DNAME
// aliases and return relevant A records.
func (dnsResolver *DNSResolverImpl) LookupHost(hostname string) ([]net.IP, time.Duration, error) {
var addrs []net.IP
r, rtt, err := dnsResolver.ExchangeOne(hostname, dns.TypeA)
if err != nil {
return addrs, rtt, err
}
if r.Rcode != dns.RcodeSuccess {
err = fmt.Errorf("DNS failure: %d-%s for A query", r.Rcode, dns.RcodeToString[r.Rcode])
return nil, rtt, err
}
for _, answer := range r.Answer {
if answer.Header().Rrtype == dns.TypeA {
if a, ok := answer.(*dns.A); ok && a.A.To4() != nil && (!isPrivateV4(a.A) || dnsResolver.allowRestrictedAddresses) {
addrs = append(addrs, a.A)
}
}
}
return addrs, rtt, nil
}
// LookupCAA sends a DNS query to find all CAA records associated with
// the provided hostname. If the response code from the resolver is
// SERVFAIL an empty slice of CAA records is returned.
func (dnsResolver *DNSResolverImpl) LookupCAA(hostname string) ([]*dns.CAA, time.Duration, error) {
r, rtt, err := dnsResolver.ExchangeOne(hostname, dns.TypeCAA)
if err != nil {
return nil, 0, err
}
// On resolver validation failure, or other server failures, return empty an
// set and no error.
var CAAs []*dns.CAA
if r.Rcode == dns.RcodeServerFailure {
return CAAs, rtt, nil
}
for _, answer := range r.Answer {
if answer.Header().Rrtype == dns.TypeCAA {
if caaR, ok := answer.(*dns.CAA); ok {
CAAs = append(CAAs, caaR)
}
}
}
return CAAs, rtt, nil
}
// LookupMX sends a DNS query to find a MX record associated hostname and returns the
// record target.
func (dnsResolver *DNSResolverImpl) LookupMX(hostname string) ([]string, time.Duration, error) {
r, rtt, err := dnsResolver.ExchangeOne(hostname, dns.TypeMX)
if err != nil {
return nil, 0, err
}
if r.Rcode != dns.RcodeSuccess {
err = fmt.Errorf("DNS failure: %d-%s for MX query", r.Rcode, dns.RcodeToString[r.Rcode])
return nil, rtt, err
}
var results []string
for _, answer := range r.Answer {
if mx, ok := answer.(*dns.MX); ok {
results = append(results, mx.Mx)
}
}
return results, rtt, nil
}