package dnsforward import ( "encoding/json" "fmt" "net/http" "net/netip" "strings" "github.com/AdguardTeam/AdGuardHome/internal/aghalg" "github.com/AdguardTeam/AdGuardHome/internal/aghhttp" "github.com/AdguardTeam/golibs/log" "github.com/AdguardTeam/golibs/stringutil" "github.com/AdguardTeam/urlfilter" "github.com/AdguardTeam/urlfilter/filterlist" "github.com/AdguardTeam/urlfilter/rules" ) // unit is a convenient alias for struct{} type unit = struct{} // accessManager controls IP and client blocking that takes place before all // other processing. An accessManager is safe for concurrent use. type accessManager struct { allowedIPs map[netip.Addr]unit blockedIPs map[netip.Addr]unit allowedClientIDs *stringutil.Set blockedClientIDs *stringutil.Set blockedHostsEng *urlfilter.DNSEngine // TODO(a.garipov): Create a type for a set of IP networks. allowedNets []netip.Prefix blockedNets []netip.Prefix } // processAccessClients is a helper for processing a list of client strings, // which may be an IP address, a CIDR, or a ClientID. func processAccessClients( clientStrs []string, ips map[netip.Addr]unit, nets *[]netip.Prefix, clientIDs *stringutil.Set, ) (err error) { for i, s := range clientStrs { var ip netip.Addr var ipnet netip.Prefix if ip, err = netip.ParseAddr(s); err == nil { ips[ip] = unit{} } else if ipnet, err = netip.ParsePrefix(s); err == nil { *nets = append(*nets, ipnet) } else { err = ValidateClientID(s) if err != nil { return fmt.Errorf("value %q at index %d: bad ip, cidr, or clientid", s, i) } clientIDs.Add(s) } } return nil } // newAccessCtx creates a new accessCtx. func newAccessCtx(allowed, blocked, blockedHosts []string) (a *accessManager, err error) { a = &accessManager{ allowedIPs: map[netip.Addr]unit{}, blockedIPs: map[netip.Addr]unit{}, allowedClientIDs: stringutil.NewSet(), blockedClientIDs: stringutil.NewSet(), } err = processAccessClients(allowed, a.allowedIPs, &a.allowedNets, a.allowedClientIDs) if err != nil { return nil, fmt.Errorf("adding allowed: %w", err) } err = processAccessClients(blocked, a.blockedIPs, &a.blockedNets, a.blockedClientIDs) if err != nil { return nil, fmt.Errorf("adding blocked: %w", err) } b := &strings.Builder{} for _, h := range blockedHosts { stringutil.WriteToBuilder(b, strings.ToLower(h), "\n") } lists := []filterlist.RuleList{ &filterlist.StringRuleList{ ID: int(0), RulesText: b.String(), IgnoreCosmetic: true, }, } rulesStrg, err := filterlist.NewRuleStorage(lists) if err != nil { return nil, fmt.Errorf("adding blocked hosts: %w", err) } a.blockedHostsEng = urlfilter.NewDNSEngine(rulesStrg) return a, nil } // allowlistMode returns true if this *accessCtx is in the allowlist mode. func (a *accessManager) allowlistMode() (ok bool) { return len(a.allowedIPs) != 0 || a.allowedClientIDs.Len() != 0 || len(a.allowedNets) != 0 } // isBlockedClientID returns true if the ClientID should be blocked. func (a *accessManager) isBlockedClientID(id string) (ok bool) { allowlistMode := a.allowlistMode() if id == "" { // In allowlist mode, consider requests without ClientIDs blocked by // default. return allowlistMode } if allowlistMode { return !a.allowedClientIDs.Has(id) } return a.blockedClientIDs.Has(id) } // isBlockedHost returns true if host should be blocked. func (a *accessManager) isBlockedHost(host string, qt rules.RRType) (ok bool) { _, ok = a.blockedHostsEng.MatchRequest(&urlfilter.DNSRequest{ Hostname: host, ClientIP: "0.0.0.0", DNSType: qt, }) return ok } // isBlockedIP returns the status of the IP address blocking as well as the rule // that blocked it. func (a *accessManager) isBlockedIP(ip netip.Addr) (blocked bool, rule string) { blocked = true ips := a.blockedIPs ipnets := a.blockedNets if a.allowlistMode() { // Enable allowlist mode and use the allowlist sets. blocked = false ips = a.allowedIPs ipnets = a.allowedNets } if _, ok := ips[ip]; ok { return blocked, ip.String() } for _, ipnet := range ipnets { if ipnet.Contains(ip) { return blocked, ipnet.String() } } return !blocked, "" } type accessListJSON struct { AllowedClients []string `json:"allowed_clients"` DisallowedClients []string `json:"disallowed_clients"` BlockedHosts []string `json:"blocked_hosts"` } func (s *Server) accessListJSON() (j accessListJSON) { s.serverLock.RLock() defer s.serverLock.RUnlock() return accessListJSON{ AllowedClients: stringutil.CloneSlice(s.conf.AllowedClients), DisallowedClients: stringutil.CloneSlice(s.conf.DisallowedClients), BlockedHosts: stringutil.CloneSlice(s.conf.BlockedHosts), } } func (s *Server) handleAccessList(w http.ResponseWriter, r *http.Request) { _ = aghhttp.WriteJSONResponse(w, r, s.accessListJSON()) } // validateAccessSet checks the internal accessListJSON lists. To search for // duplicates, we cannot compare the new stringutil.Set and []string, because // creating a set for a large array can be an unnecessary algorithmic complexity func validateAccessSet(list *accessListJSON) (err error) { allowed, err := validateStrUniq(list.AllowedClients) if err != nil { return fmt.Errorf("validating allowed clients: %w", err) } disallowed, err := validateStrUniq(list.DisallowedClients) if err != nil { return fmt.Errorf("validating disallowed clients: %w", err) } _, err = validateStrUniq(list.BlockedHosts) if err != nil { return fmt.Errorf("validating blocked hosts: %w", err) } merged := allowed.Merge(disallowed) err = merged.Validate() if err != nil { return fmt.Errorf("items in allowed and disallowed clients intersect: %w", err) } return nil } // validateStrUniq returns an informative error if clients are not unique. func validateStrUniq(clients []string) (uc aghalg.UniqChecker[string], err error) { uc = make(aghalg.UniqChecker[string], len(clients)) for _, c := range clients { uc.Add(c) } return uc, uc.Validate() } func (s *Server) handleAccessSet(w http.ResponseWriter, r *http.Request) { list := &accessListJSON{} err := json.NewDecoder(r.Body).Decode(&list) if err != nil { aghhttp.Error(r, w, http.StatusBadRequest, "decoding request: %s", err) return } err = validateAccessSet(list) if err != nil { aghhttp.Error(r, w, http.StatusBadRequest, err.Error()) return } var a *accessManager a, err = newAccessCtx(list.AllowedClients, list.DisallowedClients, list.BlockedHosts) if err != nil { aghhttp.Error(r, w, http.StatusBadRequest, "creating access ctx: %s", err) return } defer log.Debug( "access: updated lists: %d, %d, %d", len(list.AllowedClients), len(list.DisallowedClients), len(list.BlockedHosts), ) defer s.conf.ConfigModified() s.serverLock.Lock() defer s.serverLock.Unlock() s.conf.AllowedClients = list.AllowedClients s.conf.DisallowedClients = list.DisallowedClients s.conf.BlockedHosts = list.BlockedHosts s.access = a }