AdGuardHome/dnsforward/config.go

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package dnsforward
import (
"crypto/tls"
"crypto/x509"
"errors"
"fmt"
"net"
"net/http"
"sort"
"github.com/AdguardTeam/golibs/log"
"github.com/joomcode/errorx"
"github.com/AdguardTeam/AdGuardHome/dnsfilter"
"github.com/AdguardTeam/dnsproxy/proxy"
"github.com/AdguardTeam/dnsproxy/upstream"
)
// 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
// --
// Filtering callback function
FilterHandler func(clientAddr string, settings *dnsfilter.RequestFilteringSettings) `yaml:"-"`
// This callback function returns the list of upstream servers for a client specified by IP address
GetUpstreamsByClient func(clientAddr string) []upstream.Upstream `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 string `yaml:"blocking_ipv4"` // IP address to be returned for a blocked A request
BlockingIPv6 string `yaml:"blocking_ipv6"` // IP address to be returned for a blocked AAAA request
BlockingIPAddrv4 net.IP `yaml:"-"`
BlockingIPAddrv6 net.IP `yaml:"-"`
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"`
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
// ECS settings
// --
EnableEDNSClientSubnet bool `yaml:"edns_client_subnet"` // Enable EDNS Client Subnet option
EnableDNSSEC bool `yaml:"enable_dnssec"` // Set DNSSEC flag in outcoming DNS request
// 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
}
// TLSConfig is the TLS configuration for HTTPS, DNS-over-HTTPS, and DNS-over-TLS
type TLSConfig struct {
TLSListenAddr *net.TCPAddr `yaml:"-" json:"-"`
StrictSNICheck bool `yaml:"strict_sni_check" json:"-"` // Reject connection if the client uses server name (in SNI) that doesn't match the certificate
CertificateChain string `yaml:"certificate_chain" json:"certificate_chain"` // PEM-encoded certificates chain
PrivateKey string `yaml:"private_key" json:"private_key"` // PEM-encoded private key
CertificatePath string `yaml:"certificate_path" json:"certificate_path"` // certificate file name
PrivateKeyPath string `yaml:"private_key_path" json:"private_key_path"` // private key file name
CertificateChainData []byte `yaml:"-" json:"-"`
PrivateKeyData []byte `yaml:"-" json:"-"`
cert tls.Certificate // nolint(structcheck) - linter thinks that this field is unused, while TLSConfig is directly included into ServerConfig
dnsNames []string // nolint(structcheck) // DNS names from certificate (SAN) or CN value from Subject
}
// ServerConfig represents server configuration.
// The zero ServerConfig is empty and ready for use.
type ServerConfig struct {
UDPListenAddr *net.UDPAddr // UDP listen address
TCPListenAddr *net.TCPAddr // TCP listen address
Upstreams []upstream.Upstream // Configured upstreams
DomainsReservedUpstreams map[string][]upstream.Upstream // Map of domains and lists of configured upstreams
OnDNSRequest func(d *proxy.DNSContext)
FilteringConfig
TLSConfig
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))
}
// if any of ServerConfig values are zero, then default values from below are used
var defaultValues = ServerConfig{
UDPListenAddr: &net.UDPAddr{Port: 53},
TCPListenAddr: &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.UDPListenAddr,
TCPListenAddr: s.conf.TCPListenAddr,
Ratelimit: int(s.conf.Ratelimit),
RatelimitWhitelist: s.conf.RatelimitWhitelist,
RefuseAny: s.conf.RefuseAny,
CacheEnabled: true,
CacheSizeBytes: int(s.conf.CacheSize),
CacheMinTTL: s.conf.CacheMinTTL,
CacheMaxTTL: s.conf.CacheMaxTTL,
Upstreams: s.conf.Upstreams,
DomainsReservedUpstreams: s.conf.DomainsReservedUpstreams,
BeforeRequestHandler: s.beforeRequestHandler,
RequestHandler: s.handleDNSRequest,
AllServers: s.conf.AllServers,
EnableEDNSClientSubnet: s.conf.EnableEDNSClientSubnet,
FindFastestAddr: s.conf.FastestAddr,
}
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
}
// Validate proxy config
if len(proxyConfig.Upstreams) == 0 {
return proxyConfig, errors.New("no 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.UDPListenAddr == nil {
s.conf.UDPListenAddr = defaultValues.UDPListenAddr
}
if s.conf.TCPListenAddr == nil {
s.conf.TCPListenAddr = defaultValues.TCPListenAddr
}
}
// prepareUpstreamSettings - prepares upstream DNS server settings
func (s *Server) prepareUpstreamSettings() error {
upstreamConfig, err := proxy.ParseUpstreamsConfig(s.conf.UpstreamDNS, s.conf.BootstrapDNS, DefaultTimeout)
if err != nil {
return fmt.Errorf("DNS: proxy.ParseUpstreamsConfig: %s", err)
}
s.conf.Upstreams = upstreamConfig.Upstreams
s.conf.DomainsReservedUpstreams = upstreamConfig.DomainReservedUpstreams
return nil
}
// prepareIntlProxy - initializes DNS proxy that we use for internal DNS queries
func (s *Server) prepareIntlProxy() {
intlProxyConfig := proxy.Config{
CacheEnabled: true,
CacheSizeBytes: 4096,
Upstreams: s.conf.Upstreams,
DomainsReservedUpstreams: s.conf.DomainsReservedUpstreams,
}
s.internalProxy = &proxy.Proxy{Config: intlProxyConfig}
}
// prepareTLS - prepares TLS configuration for the DNS proxy
func (s *Server) prepareTLS(proxyConfig *proxy.Config) error {
if s.conf.TLSListenAddr != nil && len(s.conf.CertificateChainData) != 0 && len(s.conf.PrivateKeyData) != 0 {
proxyConfig.TLSListenAddr = s.conf.TLSListenAddr
var err error
s.conf.cert, err = tls.X509KeyPair(s.conf.CertificateChainData, s.conf.PrivateKeyData)
if err != nil {
return errorx.Decorate(err, "Failed to parse TLS keypair")
}
if s.conf.StrictSNICheck {
x, err := x509.ParseCertificate(s.conf.cert.Certificate[0])
if err != nil {
return errorx.Decorate(err, "x509.ParseCertificate(): %s", 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,
}
}
upstream.RootCAs = s.conf.TLSv12Roots
upstream.CipherSuites = s.conf.TLSCiphers
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
}