AdGuardHome/internal/dnsforward/dnsforward.go

790 lines
22 KiB
Go

// Package dnsforward contains a DNS forwarding server.
package dnsforward
import (
"fmt"
"net"
"net/http"
"net/netip"
"runtime"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/AdguardTeam/AdGuardHome/internal/aghalg"
"github.com/AdguardTeam/AdGuardHome/internal/aghnet"
"github.com/AdguardTeam/AdGuardHome/internal/client"
"github.com/AdguardTeam/AdGuardHome/internal/dhcpd"
"github.com/AdguardTeam/AdGuardHome/internal/filtering"
"github.com/AdguardTeam/AdGuardHome/internal/querylog"
"github.com/AdguardTeam/AdGuardHome/internal/rdns"
"github.com/AdguardTeam/AdGuardHome/internal/stats"
"github.com/AdguardTeam/dnsproxy/proxy"
"github.com/AdguardTeam/dnsproxy/upstream"
"github.com/AdguardTeam/golibs/cache"
"github.com/AdguardTeam/golibs/errors"
"github.com/AdguardTeam/golibs/log"
"github.com/AdguardTeam/golibs/netutil"
"github.com/AdguardTeam/golibs/stringutil"
"github.com/miekg/dns"
)
// DefaultTimeout is the default upstream timeout
const DefaultTimeout = 10 * time.Second
// defaultClientIDCacheCount is the default count of items in the LRU ClientID
// cache. The assumption here is that there won't be more than this many
// requests between the BeforeRequestHandler stage and the actual processing.
const defaultClientIDCacheCount = 1024
var defaultDNS = []string{
"https://dns10.quad9.net/dns-query",
}
var defaultBootstrap = []string{"9.9.9.10", "149.112.112.10", "2620:fe::10", "2620:fe::fe:10"}
// Often requested by all kinds of DNS probes
var defaultBlockedHosts = []string{"version.bind", "id.server", "hostname.bind"}
var webRegistered bool
// hostToIPTable is a convenient type alias for tables of host names to an IP
// address.
//
// TODO(e.burkov): Use the [DHCP] interface instead.
type hostToIPTable = map[string]netip.Addr
// ipToHostTable is a convenient type alias for tables of IP addresses to their
// host names. For example, for use with PTR queries.
//
// TODO(e.burkov): Use the [DHCP] interface instead.
type ipToHostTable = map[netip.Addr]string
// DHCP is an interface for accessing DHCP lease data needed in this package.
type DHCP interface {
// HostByIP returns the hostname of the DHCP client with the given IP
// address. The address will be netip.Addr{} if there is no such client,
// due to an assumption that a DHCP client must always have an IP address.
HostByIP(ip netip.Addr) (host string)
// IPByHost returns the IP address of the DHCP client with the given
// hostname. The hostname will be an empty string if there is no such
// client, due to an assumption that a DHCP client must always have a
// hostname, either set by the client or assigned automatically.
IPByHost(host string) (ip netip.Addr)
// Enabled returns true if DHCP provides information about clients.
Enabled() (ok bool)
}
// Server is the main way to start a DNS server.
//
// Example:
//
// s := dnsforward.Server{}
// err := s.Start(nil) // will start a DNS server listening on default port 53, in a goroutine
// err := s.Reconfigure(ServerConfig{UDPListenAddr: &net.UDPAddr{Port: 53535}}) // will reconfigure running DNS server to listen on UDP port 53535
// err := s.Stop() // will stop listening on port 53535 and cancel all goroutines
// err := s.Start(nil) // will start listening again, on port 53535, in a goroutine
//
// The zero Server is empty and ready for use.
type Server struct {
dnsProxy *proxy.Proxy // DNS proxy instance
dnsFilter *filtering.DNSFilter // DNS filter instance
dhcpServer dhcpd.Interface // DHCP server instance (optional)
queryLog querylog.QueryLog // Query log instance
stats stats.Interface
access *accessManager
// localDomainSuffix is the suffix used to detect internal hosts. It
// must be a valid domain name plus dots on each side.
localDomainSuffix string
ipset ipsetCtx
privateNets netutil.SubnetSet
// addrProc, if not nil, is used to process clients' IP addresses with rDNS,
// WHOIS, etc.
addrProc client.AddressProcessor
// localResolvers is a DNS proxy instance used to resolve PTR records for
// addresses considered private as per the [privateNets].
//
// TODO(e.burkov): Remove once the local resolvers logic moved to dnsproxy.
localResolvers *proxy.Proxy
sysResolvers aghnet.SystemResolvers
// recDetector is a cache for recursive requests. It is used to detect
// and prevent recursive requests only for private upstreams.
//
// See https://github.com/adguardTeam/adGuardHome/issues/3185#issuecomment-851048135.
recDetector *recursionDetector
// dns64Pref is the NAT64 prefix used for DNS64 response mapping. The major
// part of DNS64 happens inside the [proxy] package, but there still are
// some places where response mapping is needed (e.g. DHCP).
dns64Pref netip.Prefix
// anonymizer masks the client's IP addresses if needed.
anonymizer *aghnet.IPMut
tableHostToIP hostToIPTable
tableHostToIPLock sync.Mutex
tableIPToHost ipToHostTable
tableIPToHostLock sync.Mutex
// clientIDCache is a temporary storage for ClientIDs that were extracted
// during the BeforeRequestHandler stage.
clientIDCache cache.Cache
// DNS proxy instance for internal usage
// We don't Start() it and so no listen port is required.
internalProxy *proxy.Proxy
isRunning bool
// protectionUpdateInProgress is used to make sure that only one goroutine
// updating the protection configuration after a pause is running at a time.
protectionUpdateInProgress atomic.Bool
conf ServerConfig
// serverLock protects Server.
serverLock sync.RWMutex
}
// defaultLocalDomainSuffix is the default suffix used to detect internal hosts
// when no suffix is provided.
//
// See the documentation for Server.localDomainSuffix.
const defaultLocalDomainSuffix = "lan"
// DNSCreateParams are parameters to create a new server.
type DNSCreateParams struct {
DNSFilter *filtering.DNSFilter
Stats stats.Interface
QueryLog querylog.QueryLog
DHCPServer dhcpd.Interface
PrivateNets netutil.SubnetSet
Anonymizer *aghnet.IPMut
LocalDomain string
}
const (
// recursionTTL is the time recursive request is cached for.
recursionTTL = 1 * time.Second
// cachedRecurrentReqNum is the maximum number of cached recurrent
// requests.
cachedRecurrentReqNum = 1000
)
// NewServer creates a new instance of the dnsforward.Server
// Note: this function must be called only once
//
// TODO(a.garipov): How many constructors and initializers does this thing have?
// Refactor!
func NewServer(p DNSCreateParams) (s *Server, err error) {
var localDomainSuffix string
if p.LocalDomain == "" {
localDomainSuffix = defaultLocalDomainSuffix
} else {
err = netutil.ValidateDomainName(p.LocalDomain)
if err != nil {
return nil, fmt.Errorf("local domain: %w", err)
}
localDomainSuffix = p.LocalDomain
}
if p.Anonymizer == nil {
p.Anonymizer = aghnet.NewIPMut(nil)
}
s = &Server{
dnsFilter: p.DNSFilter,
stats: p.Stats,
queryLog: p.QueryLog,
privateNets: p.PrivateNets,
localDomainSuffix: localDomainSuffix,
recDetector: newRecursionDetector(recursionTTL, cachedRecurrentReqNum),
clientIDCache: cache.New(cache.Config{
EnableLRU: true,
MaxCount: defaultClientIDCacheCount,
}),
anonymizer: p.Anonymizer,
}
// TODO(e.burkov): Enable the refresher after the actual implementation
// passes the public testing.
s.sysResolvers, err = aghnet.NewSystemResolvers(nil)
if err != nil {
return nil, fmt.Errorf("initializing system resolvers: %w", err)
}
if p.DHCPServer != nil {
s.dhcpServer = p.DHCPServer
s.dhcpServer.SetOnLeaseChanged(s.onDHCPLeaseChanged)
s.onDHCPLeaseChanged(dhcpd.LeaseChangedAdded)
}
if runtime.GOARCH == "mips" || runtime.GOARCH == "mipsle" {
// Use plain DNS on MIPS, encryption is too slow
defaultDNS = defaultBootstrap
}
return s, nil
}
// Close gracefully closes the server. It is safe for concurrent use.
//
// TODO(e.burkov): A better approach would be making Stop method waiting for all
// its workers finished. But it would require the upstream.Upstream to have the
// Close method to prevent from hanging while waiting for unresponsive server to
// respond.
func (s *Server) Close() {
s.serverLock.Lock()
defer s.serverLock.Unlock()
s.dnsFilter = nil
s.stats = nil
s.queryLog = nil
s.dnsProxy = nil
if err := s.ipset.close(); err != nil {
log.Error("dnsforward: closing ipset: %s", err)
}
}
// WriteDiskConfig - write configuration
func (s *Server) WriteDiskConfig(c *FilteringConfig) {
s.serverLock.RLock()
defer s.serverLock.RUnlock()
sc := s.conf.FilteringConfig
*c = sc
c.RatelimitWhitelist = stringutil.CloneSlice(sc.RatelimitWhitelist)
c.BootstrapDNS = stringutil.CloneSlice(sc.BootstrapDNS)
c.AllowedClients = stringutil.CloneSlice(sc.AllowedClients)
c.DisallowedClients = stringutil.CloneSlice(sc.DisallowedClients)
c.BlockedHosts = stringutil.CloneSlice(sc.BlockedHosts)
c.TrustedProxies = stringutil.CloneSlice(sc.TrustedProxies)
c.UpstreamDNS = stringutil.CloneSlice(sc.UpstreamDNS)
}
// LocalPTRResolvers returns the current local PTR resolver configuration.
func (s *Server) LocalPTRResolvers() (localPTRResolvers []string) {
s.serverLock.RLock()
defer s.serverLock.RUnlock()
return stringutil.CloneSlice(s.conf.LocalPTRResolvers)
}
// AddrProcConfig returns the current address processing configuration. Only
// fields c.UsePrivateRDNS, c.UseRDNS, and c.UseWHOIS are filled.
func (s *Server) AddrProcConfig() (c *client.DefaultAddrProcConfig) {
s.serverLock.RLock()
defer s.serverLock.RUnlock()
return &client.DefaultAddrProcConfig{
UsePrivateRDNS: s.conf.UsePrivateRDNS,
UseRDNS: s.conf.AddrProcConf.UseRDNS,
UseWHOIS: s.conf.AddrProcConf.UseWHOIS,
}
}
// Resolve - get IP addresses by host name from an upstream server.
// No request/response filtering is performed.
// Query log and Stats are not updated.
// This method may be called before Start().
func (s *Server) Resolve(host string) ([]net.IPAddr, error) {
s.serverLock.RLock()
defer s.serverLock.RUnlock()
return s.internalProxy.LookupIPAddr(host)
}
const (
// ErrRDNSNoData is returned by [RDNSExchanger.Exchange] when the answer
// section of response is either NODATA or has no PTR records.
ErrRDNSNoData errors.Error = "no ptr data in response"
// ErrRDNSFailed is returned by [RDNSExchanger.Exchange] if the received
// response is not a NOERROR or NXDOMAIN.
ErrRDNSFailed errors.Error = "failed to resolve ptr"
)
// type check
var _ rdns.Exchanger = (*Server)(nil)
// Exchange implements the [rdns.Exchanger] interface for *Server.
func (s *Server) Exchange(ip netip.Addr) (host string, err error) {
s.serverLock.RLock()
defer s.serverLock.RUnlock()
arpa, err := netutil.IPToReversedAddr(ip.AsSlice())
if err != nil {
return "", fmt.Errorf("reversing ip: %w", err)
}
arpa = dns.Fqdn(arpa)
req := &dns.Msg{
MsgHdr: dns.MsgHdr{
Id: dns.Id(),
RecursionDesired: true,
},
Compress: true,
Question: []dns.Question{{
Name: arpa,
Qtype: dns.TypePTR,
Qclass: dns.ClassINET,
}},
}
dctx := &proxy.DNSContext{
Proto: "udp",
Req: req,
StartTime: time.Now(),
}
var resolver *proxy.Proxy
if s.privateNets.Contains(ip.AsSlice()) {
if !s.conf.UsePrivateRDNS {
return "", nil
}
resolver = s.localResolvers
s.recDetector.add(*req)
} else {
resolver = s.internalProxy
}
if err = resolver.Resolve(dctx); err != nil {
return "", err
}
return hostFromPTR(dctx.Res)
}
// hostFromPTR returns domain name from the PTR response or error.
func hostFromPTR(resp *dns.Msg) (host string, err error) {
// Distinguish between NODATA response and a failed request.
if resp.Rcode != dns.RcodeSuccess && resp.Rcode != dns.RcodeNameError {
return "", fmt.Errorf(
"received %s response: %w",
dns.RcodeToString[resp.Rcode],
ErrRDNSFailed,
)
}
for _, ans := range resp.Answer {
ptr, ok := ans.(*dns.PTR)
if ok {
return strings.TrimSuffix(ptr.Ptr, "."), nil
}
}
return "", ErrRDNSNoData
}
// Start starts the DNS server.
func (s *Server) Start() error {
s.serverLock.Lock()
defer s.serverLock.Unlock()
return s.startLocked()
}
// startLocked starts the DNS server without locking. For internal use only.
func (s *Server) startLocked() error {
err := s.dnsProxy.Start()
if err == nil {
s.isRunning = true
}
return err
}
// defaultLocalTimeout is the default timeout for resolving addresses from
// locally-served networks. It is assumed that local resolvers should work much
// faster than ordinary upstreams.
const defaultLocalTimeout = 1 * time.Second
// collectDNSIPAddrs returns IP addresses the server is listening on without
// port numbers. For internal use only.
func (s *Server) collectDNSIPAddrs() (addrs []string, err error) {
addrs = make([]string, len(s.conf.TCPListenAddrs)+len(s.conf.UDPListenAddrs))
var i int
var ip net.IP
for _, addr := range s.conf.TCPListenAddrs {
if addr == nil {
continue
}
if ip = addr.IP; ip.IsUnspecified() {
return aghnet.CollectAllIfacesAddrs()
}
addrs[i] = ip.String()
i++
}
for _, addr := range s.conf.UDPListenAddrs {
if addr == nil {
continue
}
if ip = addr.IP; ip.IsUnspecified() {
return aghnet.CollectAllIfacesAddrs()
}
addrs[i] = ip.String()
i++
}
return addrs[:i], nil
}
func (s *Server) filterOurDNSAddrs(addrs []string) (filtered []string, err error) {
var ourAddrs []string
ourAddrs, err = s.collectDNSIPAddrs()
if err != nil {
return nil, err
}
ourAddrsSet := stringutil.NewSet(ourAddrs...)
// TODO(e.burkov): The approach of subtracting sets of strings is not
// really applicable here since in case of listening on all network
// interfaces we should check the whole interface's network to cut off
// all the loopback addresses as well.
return stringutil.FilterOut(addrs, ourAddrsSet.Has), nil
}
// setupLocalResolvers initializes the resolvers for local addresses. For
// internal use only.
func (s *Server) setupLocalResolvers() (err error) {
bootstraps := s.conf.BootstrapDNS
resolvers := s.conf.LocalPTRResolvers
if len(resolvers) == 0 {
resolvers = s.sysResolvers.Get()
bootstraps = nil
} else {
resolvers = stringutil.FilterOut(resolvers, IsCommentOrEmpty)
}
resolvers, err = s.filterOurDNSAddrs(resolvers)
if err != nil {
return err
}
log.Debug("dnsforward: upstreams to resolve ptr for local addresses: %v", resolvers)
uc, err := s.prepareUpstreamConfig(resolvers, nil, &upstream.Options{
Bootstrap: bootstraps,
Timeout: defaultLocalTimeout,
// TODO(e.burkov): Should we verify server's certificates?
PreferIPv6: s.conf.BootstrapPreferIPv6,
})
if err != nil {
return fmt.Errorf("parsing private upstreams: %w", err)
}
s.localResolvers = &proxy.Proxy{
Config: proxy.Config{
UpstreamConfig: uc,
},
}
if s.conf.UsePrivateRDNS &&
// Only set the upstream config if there are any upstreams. It's safe
// to put nil into [proxy.Config.PrivateRDNSUpstreamConfig].
len(uc.Upstreams)+len(uc.DomainReservedUpstreams)+len(uc.SpecifiedDomainUpstreams) > 0 {
s.dnsProxy.PrivateRDNSUpstreamConfig = uc
}
return nil
}
// Prepare initializes parameters of s using data from conf. conf must not be
// nil.
func (s *Server) Prepare(conf *ServerConfig) (err error) {
s.conf = *conf
err = validateBlockingMode(s.conf.BlockingMode, s.conf.BlockingIPv4, s.conf.BlockingIPv6)
if err != nil {
return fmt.Errorf("checking blocking mode: %w", err)
}
s.initDefaultSettings()
err = s.prepareIpsetListSettings()
if err != nil {
// Don't wrap the error, because it's informative enough as is.
return fmt.Errorf("preparing ipset settings: %w", err)
}
err = s.prepareUpstreamSettings()
if err != nil {
// Don't wrap the error, because it's informative enough as is.
return err
}
var proxyConfig proxy.Config
proxyConfig, err = s.createProxyConfig()
if err != nil {
return fmt.Errorf("preparing proxy: %w", err)
}
s.setupDNS64()
err = s.prepareInternalProxy()
if err != nil {
return fmt.Errorf("preparing internal proxy: %w", err)
}
s.access, err = newAccessCtx(
s.conf.AllowedClients,
s.conf.DisallowedClients,
s.conf.BlockedHosts,
)
if err != nil {
return fmt.Errorf("preparing access: %w", err)
}
// Set the proxy here because [setupLocalResolvers] sets its values.
//
// TODO(e.burkov): Remove once the local resolvers logic moved to dnsproxy.
s.dnsProxy = &proxy.Proxy{Config: proxyConfig}
err = s.setupLocalResolvers()
if err != nil {
return fmt.Errorf("setting up resolvers: %w", err)
}
s.recDetector.clear()
s.setupAddrProc()
s.registerHandlers()
return nil
}
// setupAddrProc initializes the address processor. For internal use only.
func (s *Server) setupAddrProc() {
// TODO(a.garipov): This is a crutch for tests; remove.
if s.conf.AddrProcConf == nil {
s.conf.AddrProcConf = &client.DefaultAddrProcConfig{}
}
if s.conf.AddrProcConf.AddressUpdater == nil {
s.addrProc = client.EmptyAddrProc{}
} else {
c := s.conf.AddrProcConf
c.DialContext = s.DialContext
c.PrivateSubnets = s.privateNets
c.UsePrivateRDNS = s.conf.UsePrivateRDNS
s.addrProc = client.NewDefaultAddrProc(s.conf.AddrProcConf)
// Clear the initial addresses to not resolve them again.
//
// TODO(a.garipov): Consider ways of removing this once more client
// logic is moved to package client.
c.InitialAddresses = nil
}
}
// validateBlockingMode returns an error if the blocking mode data aren't valid.
func validateBlockingMode(mode BlockingMode, blockingIPv4, blockingIPv6 net.IP) (err error) {
switch mode {
case
BlockingModeDefault,
BlockingModeNXDOMAIN,
BlockingModeREFUSED,
BlockingModeNullIP:
return nil
case BlockingModeCustomIP:
if blockingIPv4 == nil {
return fmt.Errorf("blocking_ipv4 must be set when blocking_mode is custom_ip")
} else if blockingIPv6 == nil {
return fmt.Errorf("blocking_ipv6 must be set when blocking_mode is custom_ip")
}
return nil
default:
return fmt.Errorf("bad blocking mode %q", mode)
}
}
// prepareInternalProxy initializes the DNS proxy that is used for internal DNS
// queries, such as public clients PTR resolving and updater hostname resolving.
func (s *Server) prepareInternalProxy() (err error) {
srvConf := s.conf
conf := &proxy.Config{
CacheEnabled: true,
CacheSizeBytes: 4096,
UpstreamConfig: srvConf.UpstreamConfig,
MaxGoroutines: int(s.conf.MaxGoroutines),
}
setProxyUpstreamMode(
conf,
srvConf.AllServers,
srvConf.FastestAddr,
srvConf.FastestTimeout.Duration,
)
// TODO(a.garipov): Make a proper constructor for proxy.Proxy.
p := &proxy.Proxy{
Config: *conf,
}
err = p.Init()
if err != nil {
return err
}
s.internalProxy = p
return nil
}
// Stop stops the DNS server.
func (s *Server) Stop() error {
s.serverLock.Lock()
defer s.serverLock.Unlock()
return s.stopLocked()
}
// stopLocked stops the DNS server without locking. For internal use only.
func (s *Server) stopLocked() (err error) {
// TODO(e.burkov, a.garipov): Return critical errors, not just log them.
// This will require filtering all the non-critical errors in
// [upstream.Upstream] implementations.
if s.dnsProxy != nil {
err = s.dnsProxy.Stop()
if err != nil {
log.Error("dnsforward: closing primary resolvers: %s", err)
}
}
if upsConf := s.internalProxy.UpstreamConfig; upsConf != nil {
err = upsConf.Close()
if err != nil {
log.Error("dnsforward: closing internal resolvers: %s", err)
}
}
if upsConf := s.localResolvers.UpstreamConfig; upsConf != nil {
err = upsConf.Close()
if err != nil {
log.Error("dnsforward: closing local resolvers: %s", err)
}
}
s.isRunning = false
return nil
}
// IsRunning returns true if the DNS server is running.
func (s *Server) IsRunning() bool {
s.serverLock.RLock()
defer s.serverLock.RUnlock()
return s.isRunning
}
// srvClosedErr is returned when the method can't complete without inaccessible
// data from the closing server.
const srvClosedErr errors.Error = "server is closed"
// proxy returns a pointer to the current DNS proxy instance. If p is nil, the
// server is closing.
//
// See https://github.com/AdguardTeam/AdGuardHome/issues/3655.
func (s *Server) proxy() (p *proxy.Proxy) {
s.serverLock.RLock()
defer s.serverLock.RUnlock()
return s.dnsProxy
}
// Reconfigure applies the new configuration to the DNS server.
func (s *Server) Reconfigure(conf *ServerConfig) error {
s.serverLock.Lock()
defer s.serverLock.Unlock()
log.Info("dnsforward: starting reconfiguring server")
defer log.Info("dnsforward: finished reconfiguring server")
err := s.stopLocked()
if err != nil {
return fmt.Errorf("could not reconfigure the server: %w", err)
}
// It seems that net.Listener.Close() doesn't close file descriptors right away.
// We wait for some time and hope that this fd will be closed.
time.Sleep(100 * time.Millisecond)
// TODO(a.garipov): This whole piece of API is weird and needs to be remade.
if conf == nil {
conf = &s.conf
} else {
closeErr := s.addrProc.Close()
if closeErr != nil {
log.Error("dnsforward: closing address processor: %s", closeErr)
}
}
err = s.Prepare(conf)
if err != nil {
return fmt.Errorf("could not reconfigure the server: %w", err)
}
err = s.startLocked()
if err != nil {
return fmt.Errorf("could not reconfigure the server: %w", err)
}
return nil
}
// ServeHTTP is a HTTP handler method we use to provide DNS-over-HTTPS.
func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
if prx := s.proxy(); prx != nil {
prx.ServeHTTP(w, r)
}
}
// IsBlockedClient returns true if the client is blocked by the current access
// settings.
func (s *Server) IsBlockedClient(ip netip.Addr, clientID string) (blocked bool, rule string) {
s.serverLock.RLock()
defer s.serverLock.RUnlock()
blockedByIP := false
if ip != (netip.Addr{}) {
blockedByIP, rule = s.access.isBlockedIP(ip)
}
allowlistMode := s.access.allowlistMode()
blockedByClientID := s.access.isBlockedClientID(clientID)
// Allow if at least one of the checks allows in allowlist mode, but block
// if at least one of the checks blocks in blocklist mode.
if allowlistMode && blockedByIP && blockedByClientID {
log.Debug("dnsforward: client %v (id %q) is not in access allowlist", ip, clientID)
// Return now without substituting the empty rule for the
// clientID because the rule can't be empty here.
return true, rule
} else if !allowlistMode && (blockedByIP || blockedByClientID) {
log.Debug("dnsforward: client %v (id %q) is in access blocklist", ip, clientID)
blocked = true
}
return blocked, aghalg.Coalesce(rule, clientID)
}