package dnsforward import ( "crypto/tls" "crypto/x509" "errors" "fmt" "net" "net/http" "os" "sort" "github.com/AdguardTeam/AdGuardHome/internal/aghstrings" "github.com/AdguardTeam/AdGuardHome/internal/dnsfilter" "github.com/AdguardTeam/dnsproxy/proxy" "github.com/AdguardTeam/dnsproxy/upstream" "github.com/AdguardTeam/golibs/log" "github.com/ameshkov/dnscrypt/v2" ) // 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 *dnsfilter.FilteringSettings) `yaml:"-"` // GetCustomUpstreamByClient - a callback function that returns upstreams configuration // based on the client IP address. Returns nil if there are no custom upstreams for the client // // TODO(e.burkov): Replace argument type with net.IP. GetCustomUpstreamByClient func(clientAddr string) *proxy.UpstreamConfig `yaml:"-"` // Protection configuration // -- ProtectionEnabled bool `yaml:"protection_enabled"` // whether or not use any of dnsfilter features BlockingMode string `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 // 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 // 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 // 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 DNSSEC 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 // IPSET configuration - 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 client ID 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 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 // 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, CacheMinTTL: s.conf.CacheMinTTL, CacheMaxTTL: s.conf.CacheMaxTTL, 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 } if len(s.conf.BogusNXDomain) > 0 { for _, s := range s.conf.BogusNXDomain { ip := net.ParseIP(s) if ip == nil { log.Error("Invalid bogus IP: %s", s) } else { proxyConfig.BogusNXDomain = append(proxyConfig.BogusNXDomain, ip) } } } // 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.New("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 } } // 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 } d := string(data) for len(d) != 0 { s := aghstrings.SplitNext(&d, '\n') upstreams = append(upstreams, s) } log.Debug("dns: using %d upstream servers from file %s", len(upstreams), s.conf.UpstreamDNSFileName) } else { upstreams = s.conf.UpstreamDNS } upstreams = aghstrings.FilterOut(upstreams, aghstrings.IsCommentOrEmpty) upstreamConfig, err := proxy.ParseUpstreamsConfig( upstreams, upstream.Options{ Bootstrap: s.conf.BootstrapDNS, Timeout: DefaultTimeout, }, ) 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: DefaultTimeout, }, ) 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, MinVersion: tls.VersionTLS12, } return nil } // 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 && !matchDNSName(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 }