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914 lines (784 loc) · 19 KB
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package gost
import (
"bufio"
"bytes"
"context"
"crypto/tls"
"errors"
"fmt"
"io"
"io/ioutil"
"net"
"net/http"
"net/url"
"strings"
"sync"
"time"
"github.com/go-log/log"
"github.com/miekg/dns"
)
var (
// DefaultResolverTimeout is the default timeout for name resolution.
DefaultResolverTimeout = 5 * time.Second
)
type nameServerOptions struct {
timeout time.Duration
chain *Chain
}
// NameServerOption allows a common way to set name server options.
type NameServerOption func(*nameServerOptions)
// TimeoutNameServerOption sets the timeout for name server.
func TimeoutNameServerOption(timeout time.Duration) NameServerOption {
return func(opts *nameServerOptions) {
opts.timeout = timeout
}
}
// ChainNameServerOption sets the chain for name server.
func ChainNameServerOption(chain *Chain) NameServerOption {
return func(opts *nameServerOptions) {
opts.chain = chain
}
}
// NameServer is a name server.
// Currently supported protocol: TCP, UDP and TLS.
type NameServer struct {
Addr string
Protocol string
Hostname string // for TLS handshake verification
exchanger Exchanger
options nameServerOptions
}
// Init initializes the name server.
func (ns *NameServer) Init(opts ...NameServerOption) error {
for _, opt := range opts {
opt(&ns.options)
}
options := []ExchangerOption{
TimeoutExchangerOption(ns.options.timeout),
}
protocol := strings.ToLower(ns.Protocol)
switch protocol {
case "tcp", "tcp-chain":
if protocol == "tcp-chain" {
options = append(options, ChainExchangerOption(ns.options.chain))
}
ns.exchanger = NewDNSTCPExchanger(ns.Addr, options...)
case "tls", "tls-chain":
if protocol == "tls-chain" {
options = append(options, ChainExchangerOption(ns.options.chain))
}
cfg := &tls.Config{
ServerName: ns.Hostname,
}
if cfg.ServerName == "" {
cfg.InsecureSkipVerify = true
}
ns.exchanger = NewDoTExchanger(ns.Addr, cfg, options...)
case "https", "https-chain":
if protocol == "https-chain" {
options = append(options, ChainExchangerOption(ns.options.chain))
}
u, err := url.Parse(ns.Addr)
if err != nil {
return err
}
u.Scheme = "https"
cfg := &tls.Config{ServerName: ns.Hostname}
if cfg.ServerName == "" {
cfg.InsecureSkipVerify = true
}
ns.exchanger = NewDoHExchanger(u, cfg, options...)
case "udp", "udp-chain":
fallthrough
default:
if protocol == "udp-chain" {
options = append(options, ChainExchangerOption(ns.options.chain))
}
ns.exchanger = NewDNSExchanger(ns.Addr, options...)
}
return nil
}
func (ns *NameServer) String() string {
addr := ns.Addr
prot := ns.Protocol
if prot == "" {
prot = "udp"
}
return fmt.Sprintf("%s/%s", addr, prot)
}
type resolverOptions struct {
chain *Chain
timeout time.Duration
ttl time.Duration
prefer string
srcIP net.IP
}
// ResolverOption allows a common way to set Resolver options.
type ResolverOption func(*resolverOptions)
// ChainResolverOption sets the chain for Resolver.
func ChainResolverOption(chain *Chain) ResolverOption {
return func(opts *resolverOptions) {
opts.chain = chain
}
}
// TimeoutResolverOption sets the timeout for Resolver.
func TimeoutResolverOption(timeout time.Duration) ResolverOption {
return func(opts *resolverOptions) {
opts.timeout = timeout
}
}
// TTLResolverOption sets the timeout for Resolver.
func TTLResolverOption(ttl time.Duration) ResolverOption {
return func(opts *resolverOptions) {
opts.ttl = ttl
}
}
// PreferResolverOption sets the prefer for Resolver.
func PreferResolverOption(prefer string) ResolverOption {
return func(opts *resolverOptions) {
opts.prefer = prefer
}
}
// SrcIPResolverOption sets the source IP for Resolver.
func SrcIPResolverOption(ip net.IP) ResolverOption {
return func(opts *resolverOptions) {
opts.srcIP = ip
}
}
// Resolver is a name resolver for domain name.
// It contains a list of name servers.
type Resolver interface {
// Init initializes the Resolver instance.
Init(opts ...ResolverOption) error
// Resolve returns a slice of that host's IPv4 and IPv6 addresses.
Resolve(host string) ([]net.IP, error)
// Exchange performs a synchronous query,
// It sends the message query and waits for a reply.
Exchange(ctx context.Context, query []byte) (reply []byte, err error)
}
// ReloadResolver is resolover that support live reloading.
type ReloadResolver interface {
Resolver
Reloader
Stoppable
}
type resolver struct {
servers []NameServer
ttl time.Duration
timeout time.Duration
period time.Duration
domain string
cache *resolverCache
stopped chan struct{}
mux sync.RWMutex
prefer string // ipv4 or ipv6
srcIP net.IP // for edns0 subnet option
options resolverOptions
}
// NewResolver create a new Resolver with the given name servers and resolution timeout.
func NewResolver(ttl time.Duration, servers ...NameServer) ReloadResolver {
r := newResolver(ttl, servers...)
return r
}
func newResolver(ttl time.Duration, servers ...NameServer) *resolver {
return &resolver{
servers: servers,
cache: newResolverCache(ttl),
stopped: make(chan struct{}),
}
}
func (r *resolver) Init(opts ...ResolverOption) error {
if r == nil {
return nil
}
r.mux.Lock()
defer r.mux.Unlock()
for _, opt := range opts {
opt(&r.options)
}
timeout := r.timeout
if r.options.timeout != 0 {
timeout = r.options.timeout
}
if timeout <= 0 {
timeout = DefaultResolverTimeout
}
if r.options.ttl != 0 {
r.ttl = r.options.ttl
}
if r.options.prefer != "" {
r.prefer = r.options.prefer
}
if r.options.srcIP != nil {
r.srcIP = r.options.srcIP
}
var nss []NameServer
for _, ns := range r.servers {
if err := ns.Init( // init all name servers
ChainNameServerOption(r.options.chain),
TimeoutNameServerOption(timeout),
); err != nil {
continue // ignore invalid name servers
}
nss = append(nss, ns)
}
r.servers = nss
return nil
}
func (r *resolver) copyServers() []NameServer {
r.mux.RLock()
defer r.mux.RUnlock()
servers := make([]NameServer, len(r.servers))
for i := range r.servers {
servers[i] = r.servers[i]
}
return servers
}
func (r *resolver) Resolve(host string) (ips []net.IP, err error) {
r.mux.RLock()
domain := r.domain
r.mux.RUnlock()
if ip := net.ParseIP(host); ip != nil {
return []net.IP{ip}, nil
}
if !strings.Contains(host, ".") && domain != "" {
host = host + "." + domain
}
ctx := context.Background()
for _, ns := range r.copyServers() {
ips, err = r.resolve(ctx, ns.exchanger, host)
if err != nil {
log.Logf("[resolver] %s via %s : %s", host, ns.String(), err)
continue
}
if Debug {
log.Logf("[resolver] %s via %s %v", host, ns.String(), ips)
}
if len(ips) > 0 {
break
}
}
return
}
func (r *resolver) resolve(ctx context.Context, ex Exchanger, host string) (ips []net.IP, err error) {
if ex == nil {
return
}
r.mux.RLock()
prefer := r.prefer
r.mux.RUnlock()
if prefer == "ipv6" { // prefer ipv6
mq := &dns.Msg{}
mq.SetQuestion(dns.Fqdn(host), dns.TypeAAAA)
ips, err = r.resolveIPs(ctx, ex, mq)
if err != nil || len(ips) > 0 {
return
}
}
mq := &dns.Msg{}
mq.SetQuestion(dns.Fqdn(host), dns.TypeA)
return r.resolveIPs(ctx, ex, mq)
}
func (r *resolver) resolveIPs(ctx context.Context, ex Exchanger, mq *dns.Msg) (ips []net.IP, err error) {
key := newResolverCacheKey(&mq.Question[0])
mr := r.cache.loadCache(key)
if mr == nil {
r.addSubnetOpt(mq)
mr, err = r.exchangeMsg(ctx, ex, mq)
if err != nil {
return
}
r.cache.storeCache(key, mr, r.TTL())
}
for _, ans := range mr.Answer {
if ar, _ := ans.(*dns.AAAA); ar != nil {
ips = append(ips, ar.AAAA)
}
if ar, _ := ans.(*dns.A); ar != nil {
ips = append(ips, ar.A)
}
}
return
}
func (r *resolver) addSubnetOpt(m *dns.Msg) {
if m == nil || r.srcIP == nil {
return
}
opt := new(dns.OPT)
opt.Hdr.Name = "."
opt.Hdr.Rrtype = dns.TypeOPT
e := new(dns.EDNS0_SUBNET)
e.Code = dns.EDNS0SUBNET
if ip := r.srcIP.To4(); ip != nil {
e.Family = 1
e.SourceNetmask = 32
e.Address = ip.To4()
} else {
e.Family = 2
e.SourceNetmask = 128
e.Address = r.srcIP
}
opt.Option = append(opt.Option, e)
m.Extra = append(m.Extra, opt)
}
func (r *resolver) Exchange(ctx context.Context, query []byte) (reply []byte, err error) {
mq := &dns.Msg{}
if err = mq.Unpack(query); err != nil {
return
}
if len(mq.Question) == 0 {
return nil, errors.New("empty question")
}
var mr *dns.Msg
// Only cache for single question.
if len(mq.Question) == 1 {
key := newResolverCacheKey(&mq.Question[0])
mr = r.cache.loadCache(key)
if mr != nil {
log.Logf("[dns] exchange message %d (cached): %s", mq.Id, mq.Question[0].String())
mr.Id = mq.Id
return mr.Pack()
}
defer func() {
if mr != nil {
r.cache.storeCache(key, mr, r.TTL())
}
}()
}
r.addSubnetOpt(mq)
for _, ns := range r.copyServers() {
log.Logf("[dns] exchange message %d via %s: %s", mq.Id, ns.String(), mq.Question[0].String())
mr, err = r.exchangeMsg(ctx, ns.exchanger, mq)
if err == nil {
break
}
log.Logf("[dns] exchange message %d via %s: %s", mq.Id, ns.String(), err)
}
if err != nil {
return
}
return mr.Pack()
}
func (r *resolver) exchangeMsg(ctx context.Context, ex Exchanger, mq *dns.Msg) (mr *dns.Msg, err error) {
query, err := mq.Pack()
if err != nil {
return
}
reply, err := ex.Exchange(ctx, query)
if err != nil {
return
}
mr = &dns.Msg{}
err = mr.Unpack(reply)
return
}
func (r *resolver) TTL() time.Duration {
r.mux.RLock()
defer r.mux.RUnlock()
return r.ttl
}
func (r *resolver) Reload(rd io.Reader) error {
var ttl, timeout, period time.Duration
var domain, prefer string
var srcIP net.IP
var nss []NameServer
if rd == nil || r.Stopped() {
return nil
}
scanner := bufio.NewScanner(rd)
for scanner.Scan() {
line := scanner.Text()
ss := splitLine(line)
if len(ss) == 0 {
continue
}
switch ss[0] {
case "timeout": // timeout option
if len(ss) > 1 {
timeout, _ = time.ParseDuration(ss[1])
}
case "ttl": // ttl option
if len(ss) > 1 {
ttl, _ = time.ParseDuration(ss[1])
}
case "reload": // reload option
if len(ss) > 1 {
period, _ = time.ParseDuration(ss[1])
}
case "domain":
if len(ss) > 1 {
domain = ss[1]
}
case "search", "sortlist", "options": // we don't support these features in /etc/resolv.conf
case "prefer":
if len(ss) > 1 {
prefer = strings.ToLower(ss[1])
}
case "ip":
if len(ss) > 1 {
srcIP = net.ParseIP(ss[1])
}
case "nameserver": // nameserver option, compatible with /etc/resolv.conf
if len(ss) <= 1 {
break
}
ss = ss[1:]
fallthrough
default:
var ns NameServer
switch len(ss) {
case 0:
break
case 1:
ns.Addr = ss[0]
case 2:
ns.Addr = ss[0]
ns.Protocol = ss[1]
default:
ns.Addr = ss[0]
ns.Protocol = ss[1]
ns.Hostname = ss[2]
}
if strings.HasPrefix(ns.Addr, "https") && ns.Protocol == "" {
ns.Protocol = "https"
}
nss = append(nss, ns)
}
}
if err := scanner.Err(); err != nil {
return err
}
r.mux.Lock()
r.ttl = ttl
r.timeout = timeout
r.domain = domain
r.period = period
r.prefer = prefer
r.srcIP = srcIP
r.servers = nss
r.mux.Unlock()
r.Init()
return nil
}
func (r *resolver) Period() time.Duration {
if r.Stopped() {
return -1
}
r.mux.RLock()
defer r.mux.RUnlock()
return r.period
}
// Stop stops reloading.
func (r *resolver) Stop() {
select {
case <-r.stopped:
default:
close(r.stopped)
}
}
// Stopped checks whether the reloader is stopped.
func (r *resolver) Stopped() bool {
select {
case <-r.stopped:
return true
default:
return false
}
}
func (r *resolver) String() string {
if r == nil {
return ""
}
r.mux.RLock()
defer r.mux.RUnlock()
b := &bytes.Buffer{}
fmt.Fprintf(b, "TTL %v\n", r.ttl)
fmt.Fprintf(b, "Reload %v\n", r.period)
fmt.Fprintf(b, "Domain %v\n", r.domain)
for i := range r.servers {
fmt.Fprintln(b, r.servers[i])
}
return b.String()
}
type resolverCacheKey string
// newResolverCacheKey generates resolver cache key from question of dns query.
func newResolverCacheKey(q *dns.Question) resolverCacheKey {
if q == nil {
return ""
}
key := fmt.Sprintf("%s%s.%s", q.Name, dns.Class(q.Qclass).String(), dns.Type(q.Qtype).String())
return resolverCacheKey(key)
}
type resolverCacheItem struct {
mr *dns.Msg
ts int64
ttl time.Duration
}
type resolverCache struct {
m sync.Map
}
func newResolverCache(ttl time.Duration) *resolverCache {
return &resolverCache{}
}
func (rc *resolverCache) loadCache(key resolverCacheKey) *dns.Msg {
v, ok := rc.m.Load(key)
if !ok {
return nil
}
item, ok := v.(*resolverCacheItem)
if !ok {
return nil
}
elapsed := time.Since(time.Unix(item.ts, 0))
if item.ttl > 0 && elapsed > item.ttl {
rc.m.Delete(key)
return nil
}
for _, rr := range item.mr.Answer {
if elapsed > time.Duration(rr.Header().Ttl)*time.Second {
rc.m.Delete(key)
return nil
}
}
if Debug {
log.Logf("[resolver] cache hit %s", key)
}
return item.mr.Copy()
}
func (rc *resolverCache) storeCache(key resolverCacheKey, mr *dns.Msg, ttl time.Duration) {
if key == "" || mr == nil || ttl < 0 {
return
}
rc.m.Store(key, &resolverCacheItem{
mr: mr.Copy(),
ts: time.Now().Unix(),
ttl: ttl,
})
if Debug {
log.Logf("[resolver] cache store %s", key)
}
}
// Exchanger is an interface for DNS synchronous query.
type Exchanger interface {
Exchange(ctx context.Context, query []byte) ([]byte, error)
}
type exchangerOptions struct {
chain *Chain
timeout time.Duration
}
// ExchangerOption allows a common way to set Exchanger options.
type ExchangerOption func(opts *exchangerOptions)
// ChainExchangerOption sets the chain for Exchanger.
func ChainExchangerOption(chain *Chain) ExchangerOption {
return func(opts *exchangerOptions) {
opts.chain = chain
}
}
// TimeoutExchangerOption sets the timeout for Exchanger.
func TimeoutExchangerOption(timeout time.Duration) ExchangerOption {
return func(opts *exchangerOptions) {
opts.timeout = timeout
}
}
type dnsExchanger struct {
addr string
options exchangerOptions
}
// NewDNSExchanger creates a DNS over UDP Exchanger
func NewDNSExchanger(addr string, opts ...ExchangerOption) Exchanger {
var options exchangerOptions
for _, opt := range opts {
opt(&options)
}
if _, port, _ := net.SplitHostPort(addr); port == "" {
addr = net.JoinHostPort(addr, "53")
}
return &dnsExchanger{
addr: addr,
options: options,
}
}
func (ex *dnsExchanger) Exchange(ctx context.Context, query []byte) ([]byte, error) {
t := time.Now()
c, err := ex.options.chain.DialContext(ctx,
"udp", ex.addr,
TimeoutChainOption(ex.options.timeout),
)
if err != nil {
return nil, err
}
c.SetDeadline(time.Now().Add(ex.options.timeout - time.Since(t)))
defer c.Close()
conn := &dns.Conn{
Conn: c,
}
if _, err = conn.Write(query); err != nil {
return nil, err
}
mr, err := conn.ReadMsg()
if err != nil {
return nil, err
}
return mr.Pack()
}
type dnsTCPExchanger struct {
addr string
options exchangerOptions
}
// NewDNSTCPExchanger creates a DNS over TCP Exchanger
func NewDNSTCPExchanger(addr string, opts ...ExchangerOption) Exchanger {
var options exchangerOptions
for _, opt := range opts {
opt(&options)
}
if _, port, _ := net.SplitHostPort(addr); port == "" {
addr = net.JoinHostPort(addr, "53")
}
return &dnsTCPExchanger{
addr: addr,
options: options,
}
}
func (ex *dnsTCPExchanger) Exchange(ctx context.Context, query []byte) ([]byte, error) {
t := time.Now()
c, err := ex.options.chain.DialContext(ctx,
"tcp", ex.addr,
TimeoutChainOption(ex.options.timeout),
)
if err != nil {
return nil, err
}
c.SetDeadline(time.Now().Add(ex.options.timeout - time.Since(t)))
defer c.Close()
conn := &dns.Conn{
Conn: c,
}
if _, err = conn.Write(query); err != nil {
return nil, err
}
mr, err := conn.ReadMsg()
if err != nil {
return nil, err
}
return mr.Pack()
}
type dotExchanger struct {
addr string
tlsConfig *tls.Config
options exchangerOptions
}
// NewDoTExchanger creates a DNS over TLS Exchanger
func NewDoTExchanger(addr string, tlsConfig *tls.Config, opts ...ExchangerOption) Exchanger {
var options exchangerOptions
for _, opt := range opts {
opt(&options)
}
if _, port, _ := net.SplitHostPort(addr); port == "" {
addr = net.JoinHostPort(addr, "53")
}
if tlsConfig == nil {
tlsConfig = &tls.Config{
InsecureSkipVerify: true,
}
}
return &dotExchanger{
addr: addr,
tlsConfig: tlsConfig,
options: options,
}
}
func (ex *dotExchanger) dial(ctx context.Context, network, address string) (conn net.Conn, err error) {
conn, err = ex.options.chain.DialContext(ctx,
network, address,
TimeoutChainOption(ex.options.timeout),
)
if err != nil {
return
}
conn = tls.Client(conn, ex.tlsConfig)
return
}
func (ex *dotExchanger) Exchange(ctx context.Context, query []byte) ([]byte, error) {
t := time.Now()
c, err := ex.dial(ctx, "tcp", ex.addr)
if err != nil {
return nil, err
}
c.SetDeadline(time.Now().Add(ex.options.timeout - time.Since(t)))
defer c.Close()
conn := &dns.Conn{
Conn: c,
}
if _, err = conn.Write(query); err != nil {
return nil, err
}
mr, err := conn.ReadMsg()
if err != nil {
return nil, err
}
return mr.Pack()
}
type dohExchanger struct {
endpoint *url.URL
client *http.Client
options exchangerOptions
}
// NewDoHExchanger creates a DNS over HTTPS Exchanger
func NewDoHExchanger(urlStr *url.URL, tlsConfig *tls.Config, opts ...ExchangerOption) Exchanger {
var options exchangerOptions
for _, opt := range opts {
opt(&options)
}
ex := &dohExchanger{
endpoint: urlStr,
options: options,
}
ex.client = &http.Client{
Timeout: options.timeout,
Transport: &http.Transport{
// Proxy: ProxyFromEnvironment,
TLSClientConfig: tlsConfig,
ForceAttemptHTTP2: true,
MaxIdleConns: 100,
IdleConnTimeout: 90 * time.Second,
TLSHandshakeTimeout: options.timeout,
ExpectContinueTimeout: 1 * time.Second,
DialContext: ex.dialContext,
},
}
return ex
}
func (ex *dohExchanger) dialContext(ctx context.Context, network, address string) (net.Conn, error) {
return ex.options.chain.DialContext(ctx,
network, address,
TimeoutChainOption(ex.options.timeout),
)
}
func (ex *dohExchanger) Exchange(ctx context.Context, query []byte) ([]byte, error) {
req, err := http.NewRequestWithContext(ctx, "POST", ex.endpoint.String(), bytes.NewBuffer(query))
if err != nil {
return nil, fmt.Errorf("failed to create an HTTPS request: %s", err)
}
// req.Header.Add("Content-Type", "application/dns-udpwireformat")
req.Header.Add("Content-Type", "application/dns-message")
req.Host = ex.endpoint.Hostname()
client := ex.client
if client == nil {
client = http.DefaultClient
}
resp, err := client.Do(req)
if err != nil {
return nil, fmt.Errorf("failed to perform an HTTPS request: %s", err)
}
// Check response status code
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return nil, fmt.Errorf("returned status code %d", resp.StatusCode)
}
// Read wireformat response from the body
buf, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, fmt.Errorf("failed to read the response body: %s", err)
}
return buf, nil
}