package dnsforward import ( "crypto/tls" "crypto/x509" "fmt" "net" "net/http" "os" "sort" "strings" "time" "github.com/AdguardTeam/AdGuardHome/internal/aghtls" "github.com/AdguardTeam/AdGuardHome/internal/filtering" "github.com/AdguardTeam/dnsproxy/proxy" "github.com/AdguardTeam/dnsproxy/upstream" "github.com/AdguardTeam/golibs/errors" "github.com/AdguardTeam/golibs/log" "github.com/AdguardTeam/golibs/netutil" "github.com/AdguardTeam/golibs/stringutil" "github.com/AdguardTeam/golibs/timeutil" "github.com/ameshkov/dnscrypt/v2" ) // BlockingMode is an enum of all allowed blocking modes. type BlockingMode string // Allowed blocking modes. const ( // BlockingModeCustomIP means respond with a custom IP address. BlockingModeCustomIP BlockingMode = "custom_ip" // BlockingModeDefault is the same as BlockingModeNullIP for // Adblock-style rules, but responds with the IP address specified in // the rule when blocked by an `/etc/hosts`-style rule. BlockingModeDefault BlockingMode = "default" // BlockingModeNullIP means respond with a zero IP address: "0.0.0.0" // for A requests and "::" for AAAA ones. BlockingModeNullIP BlockingMode = "null_ip" // BlockingModeNXDOMAIN means respond with the NXDOMAIN code. BlockingModeNXDOMAIN BlockingMode = "nxdomain" // BlockingModeREFUSED means respond with the REFUSED code. BlockingModeREFUSED BlockingMode = "refused" ) // FilteringConfig represents the DNS filtering configuration of AdGuard Home // The zero FilteringConfig is empty and ready for use. type FilteringConfig struct { // Callbacks for other modules // -- // FilterHandler is an optional additional filtering callback. FilterHandler func(clientAddr net.IP, clientID string, settings *filtering.Settings) `yaml:"-"` // GetCustomUpstreamByClient is a callback that returns upstreams // configuration based on the client IP address or ClientID. It returns // nil if there are no custom upstreams for the client. GetCustomUpstreamByClient func(id string) (conf *proxy.UpstreamConfig, err error) `yaml:"-"` // Protection configuration // -- ProtectionEnabled bool `yaml:"protection_enabled"` // whether or not use any of filtering features BlockingMode BlockingMode `yaml:"blocking_mode"` // mode how to answer filtered requests BlockingIPv4 net.IP `yaml:"blocking_ipv4"` // IP address to be returned for a blocked A request BlockingIPv6 net.IP `yaml:"blocking_ipv6"` // IP address to be returned for a blocked AAAA request BlockedResponseTTL uint32 `yaml:"blocked_response_ttl"` // if 0, then default is used (3600) // IP (or domain name) which is used to respond to DNS requests blocked by parental control or safe-browsing ParentalBlockHost string `yaml:"parental_block_host"` SafeBrowsingBlockHost string `yaml:"safebrowsing_block_host"` // Anti-DNS amplification // -- Ratelimit uint32 `yaml:"ratelimit"` // max number of requests per second from a given IP (0 to disable) RatelimitWhitelist []string `yaml:"ratelimit_whitelist"` // a list of whitelisted client IP addresses RefuseAny bool `yaml:"refuse_any"` // if true, refuse ANY requests // Upstream DNS servers configuration // -- UpstreamDNS []string `yaml:"upstream_dns"` UpstreamDNSFileName string `yaml:"upstream_dns_file"` BootstrapDNS []string `yaml:"bootstrap_dns"` // a list of bootstrap DNS for DoH and DoT (plain DNS only) AllServers bool `yaml:"all_servers"` // if true, parallel queries to all configured upstream servers are enabled FastestAddr bool `yaml:"fastest_addr"` // use Fastest Address algorithm // FastestTimeout replaces the default timeout for dialing IP addresses // when FastestAddr is true. FastestTimeout timeutil.Duration `yaml:"fastest_timeout"` // Access settings // -- AllowedClients []string `yaml:"allowed_clients"` // IP addresses of whitelist clients DisallowedClients []string `yaml:"disallowed_clients"` // IP addresses of clients that should be blocked BlockedHosts []string `yaml:"blocked_hosts"` // hosts that should be blocked // TrustedProxies is the list of IP addresses and CIDR networks to detect // proxy servers addresses the DoH requests from which should be handled. // The value of nil or an empty slice for this field makes Proxy not trust // any address. TrustedProxies []string `yaml:"trusted_proxies"` // DNS cache settings // -- CacheSize uint32 `yaml:"cache_size"` // DNS cache size (in bytes) CacheMinTTL uint32 `yaml:"cache_ttl_min"` // override TTL value (minimum) received from upstream server CacheMaxTTL uint32 `yaml:"cache_ttl_max"` // override TTL value (maximum) received from upstream server // CacheOptimistic defines if optimistic cache mechanism should be used. CacheOptimistic bool `yaml:"cache_optimistic"` // Other settings // -- BogusNXDomain []string `yaml:"bogus_nxdomain"` // transform responses with these IP addresses to NXDOMAIN AAAADisabled bool `yaml:"aaaa_disabled"` // Respond with an empty answer to all AAAA requests EnableDNSSEC bool `yaml:"enable_dnssec"` // Set AD flag in outcoming DNS request EnableEDNSClientSubnet bool `yaml:"edns_client_subnet"` // Enable EDNS Client Subnet option MaxGoroutines uint32 `yaml:"max_goroutines"` // Max. number of parallel goroutines for processing incoming requests // IpsetList is the ipset configuration that allows AdGuard Home to add // IP addresses of the specified domain names to an ipset list. Syntax: // // DOMAIN[,DOMAIN].../IPSET_NAME // IpsetList []string `yaml:"ipset"` } // TLSConfig is the TLS configuration for HTTPS, DNS-over-HTTPS, and DNS-over-TLS type TLSConfig struct { TLSListenAddrs []*net.TCPAddr `yaml:"-" json:"-"` QUICListenAddrs []*net.UDPAddr `yaml:"-" json:"-"` // Reject connection if the client uses server name (in SNI) that doesn't match the certificate StrictSNICheck bool `yaml:"strict_sni_check" json:"-"` // PEM-encoded certificates chain CertificateChain string `yaml:"certificate_chain" json:"certificate_chain"` // PEM-encoded private key PrivateKey string `yaml:"private_key" json:"private_key"` CertificatePath string `yaml:"certificate_path" json:"certificate_path"` PrivateKeyPath string `yaml:"private_key_path" json:"private_key_path"` CertificateChainData []byte `yaml:"-" json:"-"` PrivateKeyData []byte `yaml:"-" json:"-"` // ServerName is the hostname of the server. Currently, it is only being // used for ClientID checking. ServerName string `yaml:"-" json:"-"` cert tls.Certificate // DNS names from certificate (SAN) or CN value from Subject dnsNames []string } // DNSCryptConfig is the DNSCrypt server configuration struct. type DNSCryptConfig struct { UDPListenAddrs []*net.UDPAddr TCPListenAddrs []*net.TCPAddr ProviderName string ResolverCert *dnscrypt.Cert Enabled bool } // ServerConfig represents server configuration. // The zero ServerConfig is empty and ready for use. type ServerConfig struct { UDPListenAddrs []*net.UDPAddr // UDP listen address TCPListenAddrs []*net.TCPAddr // TCP listen address UpstreamConfig *proxy.UpstreamConfig // Upstream DNS servers config OnDNSRequest func(d *proxy.DNSContext) FilteringConfig TLSConfig DNSCryptConfig TLSAllowUnencryptedDoH bool // UpstreamTimeout is the timeout for querying upstream servers. UpstreamTimeout time.Duration TLSv12Roots *x509.CertPool // list of root CAs for TLSv1.2 TLSCiphers []uint16 // list of TLS ciphers to use // Called when the configuration is changed by HTTP request ConfigModified func() // Register an HTTP handler HTTPRegister func(string, string, func(http.ResponseWriter, *http.Request)) // ResolveClients signals if the RDNS should resolve clients' addresses. ResolveClients bool // UsePrivateRDNS defines if the PTR requests for unknown addresses from // locally-served networks should be resolved via private PTR resolvers. UsePrivateRDNS bool // LocalPTRResolvers is a slice of addresses to be used as upstreams for // resolving PTR queries for local addresses. LocalPTRResolvers []string } // if any of ServerConfig values are zero, then default values from below are used var defaultValues = ServerConfig{ UDPListenAddrs: []*net.UDPAddr{{Port: 53}}, TCPListenAddrs: []*net.TCPAddr{{Port: 53}}, FilteringConfig: FilteringConfig{BlockedResponseTTL: 3600}, } // createProxyConfig creates and validates configuration for the main proxy func (s *Server) createProxyConfig() (proxy.Config, error) { proxyConfig := proxy.Config{ UDPListenAddr: s.conf.UDPListenAddrs, TCPListenAddr: s.conf.TCPListenAddrs, Ratelimit: int(s.conf.Ratelimit), RatelimitWhitelist: s.conf.RatelimitWhitelist, RefuseAny: s.conf.RefuseAny, TrustedProxies: s.conf.TrustedProxies, CacheMinTTL: s.conf.CacheMinTTL, CacheMaxTTL: s.conf.CacheMaxTTL, CacheOptimistic: s.conf.CacheOptimistic, UpstreamConfig: s.conf.UpstreamConfig, BeforeRequestHandler: s.beforeRequestHandler, RequestHandler: s.handleDNSRequest, EnableEDNSClientSubnet: s.conf.EnableEDNSClientSubnet, MaxGoroutines: int(s.conf.MaxGoroutines), } if s.conf.CacheSize != 0 { proxyConfig.CacheEnabled = true proxyConfig.CacheSizeBytes = int(s.conf.CacheSize) } proxyConfig.UpstreamMode = proxy.UModeLoadBalance if s.conf.AllServers { proxyConfig.UpstreamMode = proxy.UModeParallel } else if s.conf.FastestAddr { proxyConfig.UpstreamMode = proxy.UModeFastestAddr proxyConfig.FastestPingTimeout = s.conf.FastestTimeout.Duration } for i, s := range s.conf.BogusNXDomain { subnet, err := netutil.ParseSubnet(s) if err != nil { log.Error("subnet at index %d: %s", i, err) continue } proxyConfig.BogusNXDomain = append(proxyConfig.BogusNXDomain, subnet) } // TLS settings err := s.prepareTLS(&proxyConfig) if err != nil { return proxyConfig, err } if s.conf.DNSCryptConfig.Enabled { proxyConfig.DNSCryptUDPListenAddr = s.conf.DNSCryptConfig.UDPListenAddrs proxyConfig.DNSCryptTCPListenAddr = s.conf.DNSCryptConfig.TCPListenAddrs proxyConfig.DNSCryptProviderName = s.conf.DNSCryptConfig.ProviderName proxyConfig.DNSCryptResolverCert = s.conf.DNSCryptConfig.ResolverCert } // Validate proxy config if proxyConfig.UpstreamConfig == nil || len(proxyConfig.UpstreamConfig.Upstreams) == 0 { return proxyConfig, errors.Error("no default upstream servers configured") } return proxyConfig, nil } // initDefaultSettings initializes default settings if nothing // is configured func (s *Server) initDefaultSettings() { if len(s.conf.UpstreamDNS) == 0 { s.conf.UpstreamDNS = defaultDNS } if len(s.conf.BootstrapDNS) == 0 { s.conf.BootstrapDNS = defaultBootstrap } if len(s.conf.ParentalBlockHost) == 0 { s.conf.ParentalBlockHost = parentalBlockHost } if len(s.conf.SafeBrowsingBlockHost) == 0 { s.conf.SafeBrowsingBlockHost = safeBrowsingBlockHost } if s.conf.UDPListenAddrs == nil { s.conf.UDPListenAddrs = defaultValues.UDPListenAddrs } if s.conf.TCPListenAddrs == nil { s.conf.TCPListenAddrs = defaultValues.TCPListenAddrs } if len(s.conf.BlockedHosts) == 0 { s.conf.BlockedHosts = defaultBlockedHosts } if s.conf.UpstreamTimeout == 0 { s.conf.UpstreamTimeout = DefaultTimeout } } // prepareUpstreamSettings - prepares upstream DNS server settings func (s *Server) prepareUpstreamSettings() error { // We're setting a customized set of RootCAs // The reason is that Go default mechanism of loading TLS roots // does not always work properly on some routers so we're // loading roots manually and pass it here. // See "util.LoadSystemRootCAs" upstream.RootCAs = s.conf.TLSv12Roots // See util.InitTLSCiphers -- removed unsafe ciphers if len(s.conf.TLSCiphers) > 0 { upstream.CipherSuites = s.conf.TLSCiphers } // Load upstreams either from the file, or from the settings var upstreams []string if s.conf.UpstreamDNSFileName != "" { data, err := os.ReadFile(s.conf.UpstreamDNSFileName) if err != nil { return err } upstreams = stringutil.SplitTrimmed(string(data), "\n") log.Debug("dns: using %d upstream servers from file %s", len(upstreams), s.conf.UpstreamDNSFileName) } else { upstreams = s.conf.UpstreamDNS } upstreams = stringutil.FilterOut(upstreams, IsCommentOrEmpty) upstreamConfig, err := proxy.ParseUpstreamsConfig( upstreams, &upstream.Options{ Bootstrap: s.conf.BootstrapDNS, Timeout: s.conf.UpstreamTimeout, }, ) if err != nil { return fmt.Errorf("dns: proxy.ParseUpstreamsConfig: %w", err) } if len(upstreamConfig.Upstreams) == 0 { log.Info("warning: no default upstream servers specified, using %v", defaultDNS) var uc *proxy.UpstreamConfig uc, err = proxy.ParseUpstreamsConfig( defaultDNS, &upstream.Options{ Bootstrap: s.conf.BootstrapDNS, Timeout: s.conf.UpstreamTimeout, }, ) if err != nil { return fmt.Errorf("dns: failed to parse default upstreams: %v", err) } upstreamConfig.Upstreams = uc.Upstreams } s.conf.UpstreamConfig = upstreamConfig return nil } // prepareIntlProxy - initializes DNS proxy that we use for internal DNS queries func (s *Server) prepareIntlProxy() { s.internalProxy = &proxy.Proxy{ Config: proxy.Config{ CacheEnabled: true, CacheSizeBytes: 4096, UpstreamConfig: s.conf.UpstreamConfig, }, } } // prepareTLS - prepares TLS configuration for the DNS proxy func (s *Server) prepareTLS(proxyConfig *proxy.Config) error { if len(s.conf.CertificateChainData) == 0 || len(s.conf.PrivateKeyData) == 0 { return nil } if s.conf.TLSListenAddrs == nil && s.conf.QUICListenAddrs == nil { return nil } if s.conf.TLSListenAddrs != nil { proxyConfig.TLSListenAddr = s.conf.TLSListenAddrs } if s.conf.QUICListenAddrs != nil { proxyConfig.QUICListenAddr = s.conf.QUICListenAddrs } var err error s.conf.cert, err = tls.X509KeyPair(s.conf.CertificateChainData, s.conf.PrivateKeyData) if err != nil { return fmt.Errorf("failed to parse TLS keypair: %w", err) } if s.conf.StrictSNICheck { var x *x509.Certificate x, err = x509.ParseCertificate(s.conf.cert.Certificate[0]) if err != nil { return fmt.Errorf("x509.ParseCertificate(): %w", err) } if len(x.DNSNames) != 0 { s.conf.dnsNames = x.DNSNames log.Debug("dns: using DNS names from certificate's SAN: %v", x.DNSNames) sort.Strings(s.conf.dnsNames) } else { s.conf.dnsNames = append(s.conf.dnsNames, x.Subject.CommonName) log.Debug("dns: using DNS name from certificate's CN: %s", x.Subject.CommonName) } } proxyConfig.TLSConfig = &tls.Config{ GetCertificate: s.onGetCertificate, CipherSuites: aghtls.SaferCipherSuites(), MinVersion: tls.VersionTLS12, } return nil } // isInSorted returns true if s is in the sorted slice strs. func isInSorted(strs []string, s string) (ok bool) { i := sort.SearchStrings(strs, s) if i == len(strs) || strs[i] != s { return false } return true } // isWildcard returns true if host is a wildcard hostname. func isWildcard(host string) (ok bool) { return len(host) >= 2 && host[0] == '*' && host[1] == '.' } // matchesDomainWildcard returns true if host matches the domain wildcard // pattern pat. func matchesDomainWildcard(host, pat string) (ok bool) { return isWildcard(pat) && strings.HasSuffix(host, pat[1:]) } // anyNameMatches returns true if sni, the client's SNI value, matches any of // the DNS names and patterns from certificate. dnsNames must be sorted. func anyNameMatches(dnsNames []string, sni string) (ok bool) { if netutil.ValidateDomainName(sni) != nil { return false } if isInSorted(dnsNames, sni) { return true } for _, dn := range dnsNames { if matchesDomainWildcard(sni, dn) { return true } } return false } // Called by 'tls' package when Client Hello is received // If the server name (from SNI) supplied by client is incorrect - we terminate the ongoing TLS handshake. func (s *Server) onGetCertificate(ch *tls.ClientHelloInfo) (*tls.Certificate, error) { if s.conf.StrictSNICheck && !anyNameMatches(s.conf.dnsNames, ch.ServerName) { log.Info("dns: tls: unknown SNI in Client Hello: %s", ch.ServerName) return nil, fmt.Errorf("invalid SNI") } return &s.conf.cert, nil }