470 lines
12 KiB
Go
470 lines
12 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/upstream"
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"github.com/AdguardTeam/golibs/jsonutil"
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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 dnsConfigJSON struct {
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Upstreams []string `json:"upstream_dns"`
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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 string `json:"blocking_ipv4"`
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BlockingIPv6 string `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) handleGetConfig(w http.ResponseWriter, r *http.Request) {
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resp := dnsConfigJSON{}
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s.RLock()
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resp.Upstreams = stringArrayDup(s.conf.UpstreamDNS)
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resp.Bootstraps = stringArrayDup(s.conf.BootstrapDNS)
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resp.ProtectionEnabled = s.conf.ProtectionEnabled
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resp.BlockingMode = s.conf.BlockingMode
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resp.BlockingIPv4 = s.conf.BlockingIPv4
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resp.BlockingIPv6 = s.conf.BlockingIPv6
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resp.RateLimit = s.conf.Ratelimit
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resp.EDNSCSEnabled = s.conf.EnableEDNSClientSubnet
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resp.DNSSECEnabled = s.conf.EnableDNSSEC
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resp.DisableIPv6 = s.conf.AAAADisabled
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resp.CacheSize = s.conf.CacheSize
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resp.CacheMinTTL = s.conf.CacheMinTTL
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resp.CacheMaxTTL = s.conf.CacheMaxTTL
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if s.conf.FastestAddr {
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resp.UpstreamMode = "fastest_addr"
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} else if s.conf.AllServers {
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resp.UpstreamMode = "parallel"
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}
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s.RUnlock()
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js, err := json.Marshal(resp)
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if err != nil {
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httpError(r, w, http.StatusInternalServerError, "json.Marshal: %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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_, _ = w.Write(js)
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}
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func checkBlockingMode(req dnsConfigJSON) bool {
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bm := req.BlockingMode
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if !(bm == "default" || bm == "refused" || bm == "nxdomain" || bm == "null_ip" || bm == "custom_ip") {
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return false
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}
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if bm == "custom_ip" {
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ip := net.ParseIP(req.BlockingIPv4)
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if ip == nil || ip.To4() == nil {
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return false
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}
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ip = net.ParseIP(req.BlockingIPv6)
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if ip == nil {
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return false
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}
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}
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return true
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}
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// Validate bootstrap server address
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func checkBootstrap(addr string) error {
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if addr == "" { // additional check is required because NewResolver() allows empty address
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return fmt.Errorf("invalid bootstrap server address: empty")
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}
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_, err := upstream.NewResolver(addr, 0)
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if err != nil {
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return fmt.Errorf("invalid bootstrap server address: %s", err)
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}
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return nil
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}
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// nolint(gocyclo) - we need to check each JSON field separately
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func (s *Server) handleSetConfig(w http.ResponseWriter, r *http.Request) {
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req := dnsConfigJSON{}
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js, err := jsonutil.DecodeObject(&req, r.Body)
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if err != nil {
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httpError(r, w, http.StatusBadRequest, "json.Decode: %s", err)
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return
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}
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if js.Exists("upstream_dns") {
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if len(req.Upstreams) != 0 {
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err = ValidateUpstreams(req.Upstreams)
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if 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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}
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if js.Exists("bootstrap_dns") {
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for _, boot := range req.Bootstraps {
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if err := checkBootstrap(boot); err != nil {
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httpError(r, w, http.StatusBadRequest, "%s can not be used as bootstrap dns cause: %s", boot, err)
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return
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}
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}
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}
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if js.Exists("blocking_mode") && !checkBlockingMode(req) {
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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 js.Exists("upstream_mode") &&
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!(req.UpstreamMode == "" || req.UpstreamMode == "fastest_addr" || req.UpstreamMode == "parallel") {
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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.CacheMinTTL > req.CacheMaxTTL {
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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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restart := false
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s.Lock()
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if js.Exists("upstream_dns") {
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s.conf.UpstreamDNS = req.Upstreams
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restart = true
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}
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if js.Exists("bootstrap_dns") {
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s.conf.BootstrapDNS = req.Bootstraps
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restart = true
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}
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if js.Exists("protection_enabled") {
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s.conf.ProtectionEnabled = req.ProtectionEnabled
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}
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if js.Exists("blocking_mode") {
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s.conf.BlockingMode = req.BlockingMode
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if req.BlockingMode == "custom_ip" {
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if js.Exists("blocking_ipv4") {
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s.conf.BlockingIPv4 = req.BlockingIPv4
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s.conf.BlockingIPAddrv4 = net.ParseIP(req.BlockingIPv4)
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}
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if js.Exists("blocking_ipv6") {
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s.conf.BlockingIPv6 = req.BlockingIPv6
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s.conf.BlockingIPAddrv6 = net.ParseIP(req.BlockingIPv6)
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}
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}
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}
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if js.Exists("ratelimit") {
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if s.conf.Ratelimit != req.RateLimit {
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restart = true
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}
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s.conf.Ratelimit = req.RateLimit
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}
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if js.Exists("edns_cs_enabled") {
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s.conf.EnableEDNSClientSubnet = req.EDNSCSEnabled
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restart = true
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}
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if js.Exists("dnssec_enabled") {
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s.conf.EnableDNSSEC = req.DNSSECEnabled
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}
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if js.Exists("disable_ipv6") {
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s.conf.AAAADisabled = req.DisableIPv6
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}
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if js.Exists("cache_size") {
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s.conf.CacheSize = req.CacheSize
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restart = true
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}
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if js.Exists("cache_ttl_min") {
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s.conf.CacheMinTTL = req.CacheMinTTL
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restart = true
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}
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if js.Exists("cache_ttl_max") {
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s.conf.CacheMaxTTL = req.CacheMaxTTL
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restart = true
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}
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if js.Exists("upstream_mode") {
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s.conf.FastestAddr = false
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s.conf.AllServers = false
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switch req.UpstreamMode {
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case "":
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//
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case "parallel":
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s.conf.AllServers = true
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case "fastest_addr":
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s.conf.FastestAddr = true
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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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if restart {
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err = s.Reconfigure(nil)
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if 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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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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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://"}
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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: %s", 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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if len(req.Upstreams) == 0 {
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httpError(r, w, http.StatusBadRequest, "No servers specified")
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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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// 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: %s", err)
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}
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// No need to check this DNS server
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if input == "#" || !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: %s", 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: %s", 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: %s", 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("GET", "/control/dns_info", s.handleGetConfig)
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s.conf.HTTPRegister("POST", "/control/dns_config", s.handleSetConfig)
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s.conf.HTTPRegister("POST", "/control/test_upstream_dns", s.handleTestUpstreamDNS)
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s.conf.HTTPRegister("GET", "/control/access/list", s.handleAccessList)
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s.conf.HTTPRegister("POST", "/control/access/set", s.handleAccessSet)
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s.conf.HTTPRegister("", "/dns-query", s.handleDOH)
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}
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