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client.go
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client.go
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package retryabledns
import (
"bytes"
"encoding/gob"
"encoding/json"
"errors"
"fmt"
"math/rand"
"net"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/miekg/dns"
"github.com/projectdiscovery/iputil"
"github.com/projectdiscovery/retryabledns/doh"
"github.com/projectdiscovery/retryabledns/hostsfile"
"github.com/projectdiscovery/retryablehttp-go"
)
var internalRangeCheckerInstance *internalRangeChecker
func init() {
rand.Seed(time.Now().UnixNano())
var err error
internalRangeCheckerInstance, err = newInternalRangeChecker()
if err != nil {
fmt.Printf("could not initialize range checker: %s\n", err)
}
}
// Client is a DNS resolver client to resolve hostnames.
type Client struct {
resolvers []Resolver
options Options
serversIndex uint32
TCPFallback bool
udpClient *dns.Client
tcpClient *dns.Client
dohClient *doh.Client
dotClient *dns.Client
knownHosts map[string][]string
}
// New creates a new dns client
func New(baseResolvers []string, maxRetries int) *Client {
return NewWithOptions(Options{BaseResolvers: baseResolvers, MaxRetries: maxRetries})
}
// New creates a new dns client with options
func NewWithOptions(options Options) *Client {
parsedBaseResolvers := parseResolvers(deduplicate(options.BaseResolvers))
var knownHosts map[string][]string
if options.Hostsfile {
knownHosts, _ = hostsfile.ParseDefault()
}
httpOptions := retryablehttp.DefaultOptionsSingle
httpOptions.Timeout = options.Timeout
client := Client{
options: options,
resolvers: parsedBaseResolvers,
udpClient: &dns.Client{Net: "", Timeout: options.Timeout},
tcpClient: &dns.Client{Net: TCP.String(), Timeout: options.Timeout},
dohClient: doh.NewWithOptions(
doh.Options{
HttpClient: retryablehttp.NewClient(httpOptions),
},
),
dotClient: &dns.Client{Net: "tcp-tls", Timeout: options.Timeout},
knownHosts: knownHosts,
}
return &client
}
// ResolveWithSyscall attempts to resolve the host through system calls
func (c *Client) ResolveWithSyscall(host string) (*DNSData, error) {
ips, err := net.LookupIP(host)
if err != nil {
return nil, err
}
var d DNSData
d.Host = host
for _, ip := range ips {
if ipv4 := ip.To4(); ipv4 != nil {
d.A = append(d.A, ip.String())
} else if ipv6 := ip.To16(); ipv6 != nil {
d.AAAA = append(d.AAAA, ip.String())
}
}
return &d, nil
}
// Resolve is the underlying resolve function that actually resolves a host
// and gets the ip records for that host.
func (c *Client) Resolve(host string) (*DNSData, error) {
return c.Query(host, dns.TypeA)
}
// Do sends a provided dns request and return the raw native response
func (c *Client) Do(msg *dns.Msg) (*dns.Msg, error) {
var resp *dns.Msg
var err error
for i := 0; i < c.options.MaxRetries; i++ {
index := atomic.AddUint32(&c.serversIndex, 1)
resolver := c.resolvers[index%uint32(len(c.resolvers))]
switch r := resolver.(type) {
case *NetworkResolver:
switch r.Protocol {
case TCP:
resp, _, err = c.tcpClient.Exchange(msg, resolver.String())
case UDP:
resp, _, err = c.udpClient.Exchange(msg, resolver.String())
case DOT:
resp, _, err = c.dotClient.Exchange(msg, resolver.String())
}
case *DohResolver:
method := doh.MethodPost
if r.Protocol == GET {
method = doh.MethodGet
}
resp, err = c.dohClient.QueryWithDOHMsg(method, doh.Resolver{URL: r.URL}, msg)
}
if err != nil || resp == nil {
continue
}
if resp.Rcode != dns.RcodeSuccess {
continue
}
// In case we get a non empty answer stop retrying
return resp, nil
}
return resp, errors.New("could not resolve, max retries exceeded")
}
// Query sends a provided dns request and return enriched response
func (c *Client) Query(host string, requestType uint16) (*DNSData, error) {
return c.QueryMultiple(host, []uint16{requestType})
}
// A helper function
func (c *Client) A(host string) (*DNSData, error) {
return c.QueryMultiple(host, []uint16{dns.TypeA})
}
// AAAA helper function
func (c *Client) AAAA(host string) (*DNSData, error) {
return c.QueryMultiple(host, []uint16{dns.TypeAAAA})
}
// MX helper function
func (c *Client) MX(host string) (*DNSData, error) {
return c.QueryMultiple(host, []uint16{dns.TypeMX})
}
// CNAME helper function
func (c *Client) CNAME(host string) (*DNSData, error) {
return c.QueryMultiple(host, []uint16{dns.TypeCNAME})
}
// SOA helper function
func (c *Client) SOA(host string) (*DNSData, error) {
return c.QueryMultiple(host, []uint16{dns.TypeSOA})
}
// TXT helper function
func (c *Client) TXT(host string) (*DNSData, error) {
return c.QueryMultiple(host, []uint16{dns.TypeTXT})
}
// PTR helper function
func (c *Client) PTR(host string) (*DNSData, error) {
return c.QueryMultiple(host, []uint16{dns.TypePTR})
}
// NS helper function
func (c *Client) NS(host string) (*DNSData, error) {
return c.QueryMultiple(host, []uint16{dns.TypeNS})
}
// QueryMultiple sends a provided dns request and return the data
func (c *Client) QueryMultiple(host string, requestTypes []uint16) (*DNSData, error) {
var (
dnsdata DNSData
err error
)
// integrate data with known hosts in case
if c.options.Hostsfile {
if ips, ok := c.knownHosts[host]; ok {
for _, ip := range ips {
if iputil.IsIPv4(ip) {
dnsdata.A = append(dnsdata.A, ip)
} else if iputil.IsIPv6(ip) {
dnsdata.AAAA = append(dnsdata.AAAA, ip)
}
}
}
}
msg := &dns.Msg{}
msg.Id = dns.Id()
msg.RecursionDesired = true
msg.Question = make([]dns.Question, 1)
for _, requestType := range requestTypes {
name := dns.Fqdn(host)
// In case of PTR adjust the domain name
if requestType == dns.TypePTR {
var err error
if net.ParseIP(host) != nil {
name, err = dns.ReverseAddr(host)
if err != nil {
return nil, err
}
}
}
question := dns.Question{
Name: name,
Qtype: requestType,
Qclass: dns.ClassINET,
}
msg.Question[0] = question
// Enable Extension Mechanisms for DNS for all messages
msg.SetEdns0(4096, false)
var resp *dns.Msg
for i := 0; i < c.options.MaxRetries; i++ {
index := atomic.AddUint32(&c.serversIndex, 1)
resolver := c.resolvers[index%uint32(len(c.resolvers))]
switch r := resolver.(type) {
case *NetworkResolver:
switch r.Protocol {
case TCP:
resp, _, err = c.tcpClient.Exchange(msg, resolver.String())
case UDP:
resp, _, err = c.udpClient.Exchange(msg, resolver.String())
case DOT:
resp, _, err = c.dotClient.Exchange(msg, resolver.String())
}
case *DohResolver:
method := doh.MethodPost
if r.Protocol == GET {
method = doh.MethodGet
}
resp, err = c.dohClient.QueryWithDOHMsg(method, doh.Resolver{URL: r.URL}, msg)
}
if err != nil || resp == nil {
continue
}
// https://github.com/projectdiscovery/retryabledns/issues/25
if resp.Truncated && c.TCPFallback {
resp, _, _ = c.tcpClient.Exchange(msg, resolver.String())
}
err = dnsdata.ParseFromMsg(resp)
// populate anyway basic info
dnsdata.Host = host
dnsdata.StatusCode = dns.RcodeToString[resp.Rcode]
dnsdata.StatusCodeRaw = resp.Rcode
dnsdata.Timestamp = time.Now()
dnsdata.Raw += resp.String()
dnsdata.Resolver = append(dnsdata.Resolver, resolver.String())
if err != nil || !dnsdata.contains() {
continue
}
dnsdata.dedupe()
// stop on success
if resp.Rcode == dns.RcodeSuccess {
break
}
}
}
return &dnsdata, err
}
// QueryParallel sends a provided dns request to multiple resolvers in parallel
func (c *Client) QueryParallel(host string, requestType uint16, resolvers []string) ([]*DNSData, error) {
msg := dns.Msg{}
msg.SetQuestion(dns.CanonicalName(host), requestType)
var dnsdatas []*DNSData
var wg sync.WaitGroup
for _, resolver := range resolvers {
var dnsdata DNSData
dnsdatas = append(dnsdatas, &dnsdata)
wg.Add(1)
go func(resolver string, dnsdata *DNSData) {
defer wg.Done()
resp, err := dns.Exchange(msg.Copy(), resolver)
if err != nil {
return
}
err = dnsdata.ParseFromMsg(resp)
if err != nil {
return
}
dnsdata.Host = host
dnsdata.StatusCode = dns.RcodeToString[resp.Rcode]
dnsdata.StatusCodeRaw = resp.Rcode
dnsdata.Timestamp = time.Now()
dnsdata.Resolver = append(dnsdata.Resolver, resolver)
dnsdata.RawResp = resp
dnsdata.Raw = resp.String()
dnsdata.dedupe()
}(resolver, &dnsdata)
}
wg.Wait()
return dnsdatas, nil
}
// QueryMultiple sends a provided dns request and return the data
func (c *Client) Trace(host string, requestType uint16, maxrecursion int) (*TraceData, error) {
var tracedata TraceData
host = dns.CanonicalName(host)
msg := dns.Msg{}
msg.SetQuestion(host, requestType)
servers := RootDNSServersIPv4
seenNS := make(map[string]struct{})
for i := 1; i < maxrecursion; i++ {
msg.SetQuestion(host, requestType)
dnsdatas, err := c.QueryParallel(host, requestType, servers)
if err != nil {
return nil, err
}
for _, server := range servers {
seenNS[server] = struct{}{}
}
if len(dnsdatas) == 0 {
return &tracedata, nil
}
for _, dnsdata := range dnsdatas {
if dnsdata != nil && len(dnsdata.Resolver) > 0 {
tracedata.DNSData = append(tracedata.DNSData, dnsdata)
}
}
var newNSResolvers []string
var nextCname string
for _, d := range dnsdatas {
// Add ns records as new resolvers
for _, ns := range d.NS {
ips, err := net.LookupIP(ns)
if err != nil {
continue
}
for _, ip := range ips {
if ip.To4() != nil {
newNSResolvers = append(newNSResolvers, net.JoinHostPort(ip.String(), "53"))
}
}
}
// Follow CNAME - should happen at the final step of the trace
for _, cname := range d.CNAME {
if nextCname == "" {
nextCname = cname
break
}
}
}
newNSResolvers = deduplicate(newNSResolvers)
// if we have no new resolvers => return
if len(newNSResolvers) == 0 {
break
}
// Pick a random server
randomServer := newNSResolvers[rand.Intn(len(newNSResolvers))]
// If we pick the same resolver and we are not following any new cname => return
if _, ok := seenNS[randomServer]; ok && nextCname == "" {
break
}
servers = []string{randomServer}
// follow cname if any
if nextCname != "" {
host = nextCname
}
}
return &tracedata, nil
}
// DNSData is the data for a DNS request response
type DNSData struct {
Host string `json:"host,omitempty"`
TTL int `json:"ttl,omitempty"`
Resolver []string `json:"resolver,omitempty"`
A []string `json:"a,omitempty"`
AAAA []string `json:"aaaa,omitempty"`
CNAME []string `json:"cname,omitempty"`
MX []string `json:"mx,omitempty"`
PTR []string `json:"ptr,omitempty"`
SOA []string `json:"soa,omitempty"`
NS []string `json:"ns,omitempty"`
TXT []string `json:"txt,omitempty"`
Raw string `json:"raw,omitempty"`
Internal bool `json:"internal,omitempty"`
StatusCode string `json:"status_code,omitempty"`
StatusCodeRaw int `json:"status_code_raw,omitempty"`
TraceData *TraceData `json:"trace,omitempty"`
RawResp *dns.Msg `json:"raw_resp,omitempty"`
Timestamp time.Time `json:"timestamp,omitempty"`
}
// CheckInternalIPs when set to true returns if DNS response IPs
// belong to internal IP ranges.
var CheckInternalIPs = false
// ParseFromMsg and enrich data
func (d *DNSData) ParseFromMsg(msg *dns.Msg) error {
allRecords := append(msg.Answer, msg.Extra...)
allRecords = append(allRecords, msg.Ns...)
for _, record := range allRecords {
switch recordType := record.(type) {
case *dns.A:
if CheckInternalIPs && internalRangeCheckerInstance != nil && internalRangeCheckerInstance.ContainsIPv4(recordType.A) {
d.Internal = true
}
d.A = append(d.A, trimChars(recordType.A.String()))
case *dns.NS:
d.NS = append(d.NS, trimChars(recordType.Ns))
case *dns.CNAME:
d.CNAME = append(d.CNAME, trimChars(recordType.Target))
case *dns.SOA:
d.SOA = append(d.SOA, trimChars(recordType.Ns))
d.SOA = append(d.SOA, trimChars(recordType.Mbox))
case *dns.PTR:
d.PTR = append(d.PTR, trimChars(recordType.Ptr))
case *dns.MX:
d.MX = append(d.MX, trimChars(recordType.Mx))
case *dns.TXT:
for _, txt := range recordType.Txt {
d.TXT = append(d.TXT, trimChars(txt))
}
case *dns.AAAA:
if CheckInternalIPs && internalRangeCheckerInstance.ContainsIPv6(recordType.AAAA) {
d.Internal = true
}
d.AAAA = append(d.AAAA, trimChars(recordType.AAAA.String()))
}
}
return nil
}
func (d *DNSData) contains() bool {
return len(d.A) > 0 || len(d.AAAA) > 0 || len(d.CNAME) > 0 || len(d.MX) > 0 || len(d.NS) > 0 || len(d.PTR) > 0 || len(d.TXT) > 0 || len(d.SOA) > 0
}
// JSON returns the object as json string
func (d *DNSData) JSON() (string, error) {
b, err := json.Marshal(&d)
return string(b), err
}
func trimChars(s string) string {
return strings.TrimRight(s, ".")
}
func (d *DNSData) dedupe() {
d.Resolver = deduplicate(d.Resolver)
d.A = deduplicate(d.A)
d.AAAA = deduplicate(d.AAAA)
d.CNAME = deduplicate(d.CNAME)
d.MX = deduplicate(d.MX)
d.PTR = deduplicate(d.PTR)
d.SOA = deduplicate(d.SOA)
d.NS = deduplicate(d.NS)
d.TXT = deduplicate(d.TXT)
}
// Marshal encodes the dnsdata to a binary representation
func (d *DNSData) Marshal() ([]byte, error) {
var b bytes.Buffer
enc := gob.NewEncoder(&b)
err := enc.Encode(d)
if err != nil {
return nil, err
}
return b.Bytes(), nil
}
// Unmarshal decodes the dnsdata from a binary representation
func (d *DNSData) Unmarshal(b []byte) error {
dec := gob.NewDecoder(bytes.NewBuffer(b))
return dec.Decode(&d)
}
// deduplicate returns a new slice with duplicates values removed.
func deduplicate(s []string) []string {
if len(s) < 2 {
return s
}
var results []string
seen := make(map[string]struct{})
for _, val := range s {
if _, ok := seen[val]; !ok {
results = append(results, val)
seen[val] = struct{}{}
}
}
return results
}
// TraceData contains the trace information for a dns query
type TraceData struct {
Host string `json:"host,omitempty"`
DNSData []*DNSData `json:"chain,omitempty"`
}