553 lines
14 KiB
Go
553 lines
14 KiB
Go
package dnsforward
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import (
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"encoding/json"
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"fmt"
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"net"
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"net/http"
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"strconv"
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"strings"
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"github.com/AdguardTeam/dnsproxy/proxy"
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"github.com/AdguardTeam/dnsproxy/upstream"
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"github.com/AdguardTeam/golibs/log"
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"github.com/AdguardTeam/golibs/utils"
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"github.com/miekg/dns"
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)
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func httpError(r *http.Request, w http.ResponseWriter, code int, format string, args ...interface{}) {
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text := fmt.Sprintf(format, args...)
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log.Info("dns: %s %s: %s", r.Method, r.URL, text)
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http.Error(w, text, code)
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}
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type dnsConfig struct {
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Upstreams *[]string `json:"upstream_dns"`
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UpstreamsFile *string `json:"upstream_dns_file"`
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Bootstraps *[]string `json:"bootstrap_dns"`
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ProtectionEnabled *bool `json:"protection_enabled"`
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RateLimit *uint32 `json:"ratelimit"`
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BlockingMode *string `json:"blocking_mode"`
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BlockingIPv4 net.IP `json:"blocking_ipv4"`
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BlockingIPv6 net.IP `json:"blocking_ipv6"`
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EDNSCSEnabled *bool `json:"edns_cs_enabled"`
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DNSSECEnabled *bool `json:"dnssec_enabled"`
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DisableIPv6 *bool `json:"disable_ipv6"`
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UpstreamMode *string `json:"upstream_mode"`
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CacheSize *uint32 `json:"cache_size"`
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CacheMinTTL *uint32 `json:"cache_ttl_min"`
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CacheMaxTTL *uint32 `json:"cache_ttl_max"`
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}
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func (s *Server) getDNSConfig() dnsConfig {
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s.RLock()
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upstreams := stringArrayDup(s.conf.UpstreamDNS)
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upstreamFile := s.conf.UpstreamDNSFileName
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bootstraps := stringArrayDup(s.conf.BootstrapDNS)
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protectionEnabled := s.conf.ProtectionEnabled
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blockingMode := s.conf.BlockingMode
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BlockingIPv4 := s.conf.BlockingIPv4
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BlockingIPv6 := s.conf.BlockingIPv6
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Ratelimit := s.conf.Ratelimit
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EnableEDNSClientSubnet := s.conf.EnableEDNSClientSubnet
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EnableDNSSEC := s.conf.EnableDNSSEC
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AAAADisabled := s.conf.AAAADisabled
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CacheSize := s.conf.CacheSize
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CacheMinTTL := s.conf.CacheMinTTL
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CacheMaxTTL := s.conf.CacheMaxTTL
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var upstreamMode string
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if s.conf.FastestAddr {
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upstreamMode = "fastest_addr"
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} else if s.conf.AllServers {
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upstreamMode = "parallel"
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}
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s.RUnlock()
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return dnsConfig{
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Upstreams: &upstreams,
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UpstreamsFile: &upstreamFile,
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Bootstraps: &bootstraps,
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ProtectionEnabled: &protectionEnabled,
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BlockingMode: &blockingMode,
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BlockingIPv4: BlockingIPv4,
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BlockingIPv6: BlockingIPv6,
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RateLimit: &Ratelimit,
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EDNSCSEnabled: &EnableEDNSClientSubnet,
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DNSSECEnabled: &EnableDNSSEC,
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DisableIPv6: &AAAADisabled,
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CacheSize: &CacheSize,
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CacheMinTTL: &CacheMinTTL,
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CacheMaxTTL: &CacheMaxTTL,
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UpstreamMode: &upstreamMode,
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}
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}
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func (s *Server) handleGetConfig(w http.ResponseWriter, r *http.Request) {
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resp := s.getDNSConfig()
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w.Header().Set("Content-Type", "application/json")
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enc := json.NewEncoder(w)
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if err := enc.Encode(resp); err != nil {
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httpError(r, w, http.StatusInternalServerError, "json.Encoder: %s", err)
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return
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}
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}
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func (req *dnsConfig) checkBlockingMode() bool {
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if req.BlockingMode == nil {
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return true
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}
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bm := *req.BlockingMode
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if bm == "custom_ip" {
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if req.BlockingIPv4.To4() == nil {
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return false
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}
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return req.BlockingIPv6 != nil
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}
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for _, valid := range []string{
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"default",
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"refused",
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"nxdomain",
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"null_ip",
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} {
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if bm == valid {
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return true
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}
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}
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return false
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}
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func (req *dnsConfig) checkUpstreamsMode() bool {
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if req.UpstreamMode == nil {
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return true
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}
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for _, valid := range []string{
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"",
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"fastest_addr",
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"parallel",
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} {
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if *req.UpstreamMode == valid {
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return true
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}
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}
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return false
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}
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func (req *dnsConfig) checkBootstrap() (string, error) {
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if req.Bootstraps == nil {
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return "", nil
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}
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for _, boot := range *req.Bootstraps {
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if boot == "" {
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return boot, fmt.Errorf("invalid bootstrap server address: empty")
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}
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if _, err := upstream.NewResolver(boot, upstream.Options{Timeout: 0}); err != nil {
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return boot, fmt.Errorf("invalid bootstrap server address: %w", err)
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}
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}
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return "", nil
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}
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func (req *dnsConfig) checkCacheTTL() bool {
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if req.CacheMinTTL == nil && req.CacheMaxTTL == nil {
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return true
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}
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var min, max uint32
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if req.CacheMinTTL != nil {
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min = *req.CacheMinTTL
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}
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if req.CacheMaxTTL != nil {
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max = *req.CacheMaxTTL
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}
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return min <= max
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}
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func (s *Server) handleSetConfig(w http.ResponseWriter, r *http.Request) {
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req := dnsConfig{}
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dec := json.NewDecoder(r.Body)
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if err := dec.Decode(&req); err != nil {
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httpError(r, w, http.StatusBadRequest, "json Encode: %s", err)
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return
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}
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if req.Upstreams != nil {
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if err := ValidateUpstreams(*req.Upstreams); err != nil {
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httpError(r, w, http.StatusBadRequest, "wrong upstreams specification: %s", err)
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return
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}
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}
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if errBoot, err := req.checkBootstrap(); err != nil {
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httpError(r, w, http.StatusBadRequest, "%s can not be used as bootstrap dns cause: %s", errBoot, err)
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return
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}
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if !req.checkBlockingMode() {
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httpError(r, w, http.StatusBadRequest, "blocking_mode: incorrect value")
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return
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}
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if !req.checkUpstreamsMode() {
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httpError(r, w, http.StatusBadRequest, "upstream_mode: incorrect value")
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return
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}
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if !req.checkCacheTTL() {
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httpError(r, w, http.StatusBadRequest, "cache_ttl_min must be less or equal than cache_ttl_max")
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return
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}
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if s.setConfig(req) {
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if err := s.Reconfigure(nil); err != nil {
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httpError(r, w, http.StatusInternalServerError, "%s", err)
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return
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}
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}
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}
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func (s *Server) setConfig(dc dnsConfig) (restart bool) {
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s.Lock()
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if dc.Upstreams != nil {
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s.conf.UpstreamDNS = *dc.Upstreams
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restart = true
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}
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if dc.UpstreamsFile != nil {
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s.conf.UpstreamDNSFileName = *dc.UpstreamsFile
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restart = true
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}
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if dc.Bootstraps != nil {
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s.conf.BootstrapDNS = *dc.Bootstraps
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restart = true
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}
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if dc.ProtectionEnabled != nil {
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s.conf.ProtectionEnabled = *dc.ProtectionEnabled
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}
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if dc.BlockingMode != nil {
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s.conf.BlockingMode = *dc.BlockingMode
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if *dc.BlockingMode == "custom_ip" {
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s.conf.BlockingIPv4 = dc.BlockingIPv4.To4()
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s.conf.BlockingIPv6 = dc.BlockingIPv6.To16()
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}
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}
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if dc.RateLimit != nil {
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if s.conf.Ratelimit != *dc.RateLimit {
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restart = true
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}
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s.conf.Ratelimit = *dc.RateLimit
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}
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if dc.EDNSCSEnabled != nil {
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s.conf.EnableEDNSClientSubnet = *dc.EDNSCSEnabled
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restart = true
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}
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if dc.DNSSECEnabled != nil {
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s.conf.EnableDNSSEC = *dc.DNSSECEnabled
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}
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if dc.DisableIPv6 != nil {
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s.conf.AAAADisabled = *dc.DisableIPv6
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}
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if dc.CacheSize != nil {
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s.conf.CacheSize = *dc.CacheSize
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restart = true
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}
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if dc.CacheMinTTL != nil {
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s.conf.CacheMinTTL = *dc.CacheMinTTL
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restart = true
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}
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if dc.CacheMaxTTL != nil {
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s.conf.CacheMaxTTL = *dc.CacheMaxTTL
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restart = true
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}
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if dc.UpstreamMode != nil {
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switch *dc.UpstreamMode {
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case "parallel":
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s.conf.AllServers = true
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s.conf.FastestAddr = false
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case "fastest_addr":
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s.conf.AllServers = false
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s.conf.FastestAddr = true
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default:
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s.conf.AllServers = false
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s.conf.FastestAddr = false
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}
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}
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s.Unlock()
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s.conf.ConfigModified()
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return restart
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}
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type upstreamJSON struct {
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Upstreams []string `json:"upstream_dns"` // Upstreams
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BootstrapDNS []string `json:"bootstrap_dns"` // Bootstrap DNS
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}
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// ValidateUpstreams validates each upstream and returns an error if any upstream is invalid or if there are no default upstreams specified
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func ValidateUpstreams(upstreams []string) error {
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// No need to validate comments
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upstreams = filterOutComments(upstreams)
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// Consider this case valid because defaultDNS will be used
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if len(upstreams) == 0 {
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return nil
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}
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_, err := proxy.ParseUpstreamsConfig(upstreams,
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upstream.Options{
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Bootstrap: []string{},
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Timeout: DefaultTimeout,
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},
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)
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if err != nil {
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return err
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}
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var defaultUpstreamFound bool
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for _, u := range upstreams {
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d, err := validateUpstream(u)
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if err != nil {
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return err
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}
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// Check this flag until default upstream will not be found
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if !defaultUpstreamFound {
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defaultUpstreamFound = d
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}
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}
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// Return error if there are no default upstreams
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if !defaultUpstreamFound {
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return fmt.Errorf("no default upstreams specified")
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}
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return nil
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}
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var protocols = []string{"tls://", "https://", "tcp://", "sdns://", "quic://"}
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func validateUpstream(u string) (bool, error) {
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// Check if user tries to specify upstream for domain
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u, defaultUpstream, err := separateUpstream(u)
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if err != nil {
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return defaultUpstream, err
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}
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// The special server address '#' means "use the default servers"
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if u == "#" && !defaultUpstream {
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return defaultUpstream, nil
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}
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// Check if the upstream has a valid protocol prefix
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for _, proto := range protocols {
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if strings.HasPrefix(u, proto) {
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return defaultUpstream, nil
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}
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}
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// Return error if the upstream contains '://' without any valid protocol
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if strings.Contains(u, "://") {
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return defaultUpstream, fmt.Errorf("wrong protocol")
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}
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// Check if upstream is valid plain DNS
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return defaultUpstream, checkPlainDNS(u)
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}
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// separateUpstream returns upstream without specified domains and a bool flag that indicates if no domains were specified
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// error will be returned if upstream per domain specification is invalid
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func separateUpstream(upstream string) (string, bool, error) {
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defaultUpstream := true
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if strings.HasPrefix(upstream, "[/") {
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defaultUpstream = false
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// split domains and upstream string
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domainsAndUpstream := strings.Split(strings.TrimPrefix(upstream, "[/"), "/]")
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if len(domainsAndUpstream) != 2 {
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return "", defaultUpstream, fmt.Errorf("wrong dns upstream per domain specification: %s", upstream)
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}
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// split domains list and validate each one
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for _, host := range strings.Split(domainsAndUpstream[0], "/") {
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if host != "" {
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if err := utils.IsValidHostname(host); err != nil {
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return "", defaultUpstream, err
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}
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}
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}
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upstream = domainsAndUpstream[1]
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}
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return upstream, defaultUpstream, nil
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}
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// checkPlainDNS checks if host is plain DNS
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func checkPlainDNS(upstream string) error {
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// Check if host is ip without port
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if net.ParseIP(upstream) != nil {
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return nil
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}
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// Check if host is ip with port
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ip, port, err := net.SplitHostPort(upstream)
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if err != nil {
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return err
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}
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if net.ParseIP(ip) == nil {
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return fmt.Errorf("%s is not a valid IP", ip)
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}
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_, err = strconv.ParseInt(port, 0, 64)
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if err != nil {
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return fmt.Errorf("%s is not a valid port: %w", port, err)
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}
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return nil
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}
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func (s *Server) handleTestUpstreamDNS(w http.ResponseWriter, r *http.Request) {
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req := upstreamJSON{}
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err := json.NewDecoder(r.Body).Decode(&req)
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if err != nil {
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httpError(r, w, http.StatusBadRequest, "Failed to read request body: %s", err)
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return
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}
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result := map[string]string{}
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for _, host := range req.Upstreams {
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err = checkDNS(host, req.BootstrapDNS)
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if err != nil {
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log.Info("%v", err)
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result[host] = err.Error()
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} else {
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result[host] = "OK"
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}
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}
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jsonVal, err := json.Marshal(result)
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if err != nil {
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httpError(r, w, http.StatusInternalServerError, "Unable to marshal status json: %s", err)
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return
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}
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w.Header().Set("Content-Type", "application/json")
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_, err = w.Write(jsonVal)
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if err != nil {
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httpError(r, w, http.StatusInternalServerError, "Couldn't write body: %s", err)
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return
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}
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}
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func checkDNS(input string, bootstrap []string) error {
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if !isUpstream(input) {
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return nil
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}
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// separate upstream from domains list
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input, defaultUpstream, err := separateUpstream(input)
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if err != nil {
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return fmt.Errorf("wrong upstream format: %w", err)
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}
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// No need to check this DNS server
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if !defaultUpstream {
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return nil
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}
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if _, err := validateUpstream(input); err != nil {
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return fmt.Errorf("wrong upstream format: %w", err)
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}
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if len(bootstrap) == 0 {
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bootstrap = defaultBootstrap
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}
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log.Debug("checking if dns %s works...", input)
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u, err := upstream.AddressToUpstream(input, upstream.Options{Bootstrap: bootstrap, Timeout: DefaultTimeout})
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if err != nil {
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return fmt.Errorf("failed to choose upstream for %s: %w", input, err)
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}
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req := dns.Msg{}
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req.Id = dns.Id()
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req.RecursionDesired = true
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req.Question = []dns.Question{
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{Name: "google-public-dns-a.google.com.", Qtype: dns.TypeA, Qclass: dns.ClassINET},
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}
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reply, err := u.Exchange(&req)
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if err != nil {
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return fmt.Errorf("couldn't communicate with dns server %s: %w", input, err)
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}
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if len(reply.Answer) != 1 {
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return fmt.Errorf("dns server %s returned wrong answer", input)
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}
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if t, ok := reply.Answer[0].(*dns.A); ok {
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if !net.IPv4(8, 8, 8, 8).Equal(t.A) {
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return fmt.Errorf("dns server %s returned wrong answer: %v", input, t.A)
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}
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}
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log.Debug("dns %s works OK", input)
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return nil
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}
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// Control flow:
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// web
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// -> dnsforward.handleDOH -> dnsforward.ServeHTTP
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// -> proxy.ServeHTTP -> proxy.handleDNSRequest
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// -> dnsforward.handleDNSRequest
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func (s *Server) handleDOH(w http.ResponseWriter, r *http.Request) {
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if !s.conf.TLSAllowUnencryptedDOH && r.TLS == nil {
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httpError(r, w, http.StatusNotFound, "Not Found")
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return
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}
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if !s.IsRunning() {
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httpError(r, w, http.StatusInternalServerError, "dns server is not running")
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return
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}
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s.ServeHTTP(w, r)
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}
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func (s *Server) registerHandlers() {
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s.conf.HTTPRegister(http.MethodGet, "/control/dns_info", s.handleGetConfig)
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s.conf.HTTPRegister(http.MethodPost, "/control/dns_config", s.handleSetConfig)
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s.conf.HTTPRegister(http.MethodPost, "/control/test_upstream_dns", s.handleTestUpstreamDNS)
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s.conf.HTTPRegister(http.MethodGet, "/control/access/list", s.handleAccessList)
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s.conf.HTTPRegister(http.MethodPost, "/control/access/set", s.handleAccessSet)
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// Register both versions, with and without the trailing slash, to
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// prevent a 301 Moved Permanently redirect when clients request the
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// path without the trailing slash. Those redirects break some clients.
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//
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|
// See go doc net/http.ServeMux.
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//
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// See also https://github.com/AdguardTeam/AdGuardHome/issues/2628.
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s.conf.HTTPRegister("", "/dns-query", s.handleDOH)
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s.conf.HTTPRegister("", "/dns-query/", s.handleDOH)
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}
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