265 lines
9.9 KiB
Go
265 lines
9.9 KiB
Go
package dnsforward
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import (
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"crypto/tls"
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"crypto/x509"
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"errors"
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"fmt"
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"net"
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"net/http"
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"sort"
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"github.com/AdguardTeam/golibs/log"
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"github.com/joomcode/errorx"
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"github.com/AdguardTeam/AdGuardHome/dnsfilter"
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"github.com/AdguardTeam/dnsproxy/proxy"
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"github.com/AdguardTeam/dnsproxy/upstream"
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)
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// FilteringConfig represents the DNS filtering configuration of AdGuard Home
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// The zero FilteringConfig is empty and ready for use.
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type FilteringConfig struct {
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// Callbacks for other modules
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// --
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// Filtering callback function
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FilterHandler func(clientAddr string, settings *dnsfilter.RequestFilteringSettings) `yaml:"-"`
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// GetCustomUpstreamByClient - a callback function that returns upstreams configuration
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// based on the client IP address. Returns nil if there are no custom upstreams for the client
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GetCustomUpstreamByClient func(clientAddr string) *proxy.UpstreamConfig `yaml:"-"`
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// Protection configuration
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// --
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ProtectionEnabled bool `yaml:"protection_enabled"` // whether or not use any of dnsfilter features
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BlockingMode string `yaml:"blocking_mode"` // mode how to answer filtered requests
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BlockingIPv4 string `yaml:"blocking_ipv4"` // IP address to be returned for a blocked A request
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BlockingIPv6 string `yaml:"blocking_ipv6"` // IP address to be returned for a blocked AAAA request
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BlockingIPAddrv4 net.IP `yaml:"-"`
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BlockingIPAddrv6 net.IP `yaml:"-"`
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BlockedResponseTTL uint32 `yaml:"blocked_response_ttl"` // if 0, then default is used (3600)
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// IP (or domain name) which is used to respond to DNS requests blocked by parental control or safe-browsing
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ParentalBlockHost string `yaml:"parental_block_host"`
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SafeBrowsingBlockHost string `yaml:"safebrowsing_block_host"`
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// Anti-DNS amplification
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// --
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Ratelimit uint32 `yaml:"ratelimit"` // max number of requests per second from a given IP (0 to disable)
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RatelimitWhitelist []string `yaml:"ratelimit_whitelist"` // a list of whitelisted client IP addresses
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RefuseAny bool `yaml:"refuse_any"` // if true, refuse ANY requests
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// Upstream DNS servers configuration
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// --
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UpstreamDNS []string `yaml:"upstream_dns"`
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BootstrapDNS []string `yaml:"bootstrap_dns"` // a list of bootstrap DNS for DoH and DoT (plain DNS only)
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AllServers bool `yaml:"all_servers"` // if true, parallel queries to all configured upstream servers are enabled
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FastestAddr bool `yaml:"fastest_addr"` // use Fastest Address algorithm
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// Access settings
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// --
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AllowedClients []string `yaml:"allowed_clients"` // IP addresses of whitelist clients
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DisallowedClients []string `yaml:"disallowed_clients"` // IP addresses of clients that should be blocked
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BlockedHosts []string `yaml:"blocked_hosts"` // hosts that should be blocked
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// DNS cache settings
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// --
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CacheSize uint32 `yaml:"cache_size"` // DNS cache size (in bytes)
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CacheMinTTL uint32 `yaml:"cache_ttl_min"` // override TTL value (minimum) received from upstream server
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CacheMaxTTL uint32 `yaml:"cache_ttl_max"` // override TTL value (maximum) received from upstream server
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// Other settings
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// --
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BogusNXDomain []string `yaml:"bogus_nxdomain"` // transform responses with these IP addresses to NXDOMAIN
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AAAADisabled bool `yaml:"aaaa_disabled"` // Respond with an empty answer to all AAAA requests
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EnableDNSSEC bool `yaml:"enable_dnssec"` // Set DNSSEC flag in outcoming DNS request
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EnableEDNSClientSubnet bool `yaml:"edns_client_subnet"` // Enable EDNS Client Subnet option
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}
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// TLSConfig is the TLS configuration for HTTPS, DNS-over-HTTPS, and DNS-over-TLS
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type TLSConfig struct {
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TLSListenAddr *net.TCPAddr `yaml:"-" json:"-"`
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StrictSNICheck bool `yaml:"strict_sni_check" json:"-"` // Reject connection if the client uses server name (in SNI) that doesn't match the certificate
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CertificateChain string `yaml:"certificate_chain" json:"certificate_chain"` // PEM-encoded certificates chain
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PrivateKey string `yaml:"private_key" json:"private_key"` // PEM-encoded private key
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CertificatePath string `yaml:"certificate_path" json:"certificate_path"` // certificate file name
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PrivateKeyPath string `yaml:"private_key_path" json:"private_key_path"` // private key file name
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CertificateChainData []byte `yaml:"-" json:"-"`
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PrivateKeyData []byte `yaml:"-" json:"-"`
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cert tls.Certificate // nolint(structcheck) - linter thinks that this field is unused, while TLSConfig is directly included into ServerConfig
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dnsNames []string // nolint(structcheck) // DNS names from certificate (SAN) or CN value from Subject
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}
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// ServerConfig represents server configuration.
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// The zero ServerConfig is empty and ready for use.
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type ServerConfig struct {
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UDPListenAddr *net.UDPAddr // UDP listen address
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TCPListenAddr *net.TCPAddr // TCP listen address
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UpstreamConfig *proxy.UpstreamConfig // Upstream DNS servers config
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OnDNSRequest func(d *proxy.DNSContext)
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FilteringConfig
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TLSConfig
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TLSAllowUnencryptedDOH bool
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TLSv12Roots *x509.CertPool // list of root CAs for TLSv1.2
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TLSCiphers []uint16 // list of TLS ciphers to use
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// Called when the configuration is changed by HTTP request
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ConfigModified func()
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// Register an HTTP handler
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HTTPRegister func(string, string, func(http.ResponseWriter, *http.Request))
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}
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// if any of ServerConfig values are zero, then default values from below are used
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var defaultValues = ServerConfig{
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UDPListenAddr: &net.UDPAddr{Port: 53},
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TCPListenAddr: &net.TCPAddr{Port: 53},
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FilteringConfig: FilteringConfig{BlockedResponseTTL: 3600},
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}
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// createProxyConfig creates and validates configuration for the main proxy
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func (s *Server) createProxyConfig() (proxy.Config, error) {
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proxyConfig := proxy.Config{
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UDPListenAddr: s.conf.UDPListenAddr,
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TCPListenAddr: s.conf.TCPListenAddr,
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Ratelimit: int(s.conf.Ratelimit),
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RatelimitWhitelist: s.conf.RatelimitWhitelist,
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RefuseAny: s.conf.RefuseAny,
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CacheEnabled: true,
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CacheSizeBytes: int(s.conf.CacheSize),
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CacheMinTTL: s.conf.CacheMinTTL,
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CacheMaxTTL: s.conf.CacheMaxTTL,
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UpstreamConfig: s.conf.UpstreamConfig,
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BeforeRequestHandler: s.beforeRequestHandler,
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RequestHandler: s.handleDNSRequest,
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AllServers: s.conf.AllServers,
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EnableEDNSClientSubnet: s.conf.EnableEDNSClientSubnet,
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FindFastestAddr: s.conf.FastestAddr,
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}
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if len(s.conf.BogusNXDomain) > 0 {
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for _, s := range s.conf.BogusNXDomain {
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ip := net.ParseIP(s)
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if ip == nil {
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log.Error("Invalid bogus IP: %s", s)
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} else {
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proxyConfig.BogusNXDomain = append(proxyConfig.BogusNXDomain, ip)
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}
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}
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}
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// TLS settings
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err := s.prepareTLS(&proxyConfig)
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if err != nil {
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return proxyConfig, err
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}
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// Validate proxy config
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if proxyConfig.UpstreamConfig == nil || len(proxyConfig.UpstreamConfig.Upstreams) == 0 {
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return proxyConfig, errors.New("no upstream servers configured")
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}
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return proxyConfig, nil
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}
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// initDefaultSettings initializes default settings if nothing
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// is configured
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func (s *Server) initDefaultSettings() {
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if len(s.conf.UpstreamDNS) == 0 {
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s.conf.UpstreamDNS = defaultDNS
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}
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if len(s.conf.BootstrapDNS) == 0 {
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s.conf.BootstrapDNS = defaultBootstrap
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}
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if len(s.conf.ParentalBlockHost) == 0 {
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s.conf.ParentalBlockHost = parentalBlockHost
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}
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if len(s.conf.SafeBrowsingBlockHost) == 0 {
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s.conf.SafeBrowsingBlockHost = safeBrowsingBlockHost
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}
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if s.conf.UDPListenAddr == nil {
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s.conf.UDPListenAddr = defaultValues.UDPListenAddr
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}
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if s.conf.TCPListenAddr == nil {
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s.conf.TCPListenAddr = defaultValues.TCPListenAddr
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}
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}
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// prepareUpstreamSettings - prepares upstream DNS server settings
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func (s *Server) prepareUpstreamSettings() error {
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upstreamConfig, err := proxy.ParseUpstreamsConfig(s.conf.UpstreamDNS, s.conf.BootstrapDNS, DefaultTimeout)
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if err != nil {
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return fmt.Errorf("DNS: proxy.ParseUpstreamsConfig: %s", err)
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}
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s.conf.UpstreamConfig = &upstreamConfig
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return nil
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}
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// prepareIntlProxy - initializes DNS proxy that we use for internal DNS queries
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func (s *Server) prepareIntlProxy() {
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intlProxyConfig := proxy.Config{
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CacheEnabled: true,
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CacheSizeBytes: 4096,
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UpstreamConfig: s.conf.UpstreamConfig,
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}
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s.internalProxy = &proxy.Proxy{Config: intlProxyConfig}
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}
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// prepareTLS - prepares TLS configuration for the DNS proxy
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func (s *Server) prepareTLS(proxyConfig *proxy.Config) error {
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if s.conf.TLSListenAddr != nil && len(s.conf.CertificateChainData) != 0 && len(s.conf.PrivateKeyData) != 0 {
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proxyConfig.TLSListenAddr = s.conf.TLSListenAddr
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var err error
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s.conf.cert, err = tls.X509KeyPair(s.conf.CertificateChainData, s.conf.PrivateKeyData)
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if err != nil {
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return errorx.Decorate(err, "Failed to parse TLS keypair")
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}
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if s.conf.StrictSNICheck {
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x, err := x509.ParseCertificate(s.conf.cert.Certificate[0])
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if err != nil {
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return errorx.Decorate(err, "x509.ParseCertificate(): %s", err)
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}
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if len(x.DNSNames) != 0 {
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s.conf.dnsNames = x.DNSNames
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log.Debug("DNS: using DNS names from certificate's SAN: %v", x.DNSNames)
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sort.Strings(s.conf.dnsNames)
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} else {
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s.conf.dnsNames = append(s.conf.dnsNames, x.Subject.CommonName)
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log.Debug("DNS: using DNS name from certificate's CN: %s", x.Subject.CommonName)
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}
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}
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proxyConfig.TLSConfig = &tls.Config{
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GetCertificate: s.onGetCertificate,
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MinVersion: tls.VersionTLS12,
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}
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}
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upstream.RootCAs = s.conf.TLSv12Roots
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upstream.CipherSuites = s.conf.TLSCiphers
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return nil
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}
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// Called by 'tls' package when Client Hello is received
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// If the server name (from SNI) supplied by client is incorrect - we terminate the ongoing TLS handshake.
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func (s *Server) onGetCertificate(ch *tls.ClientHelloInfo) (*tls.Certificate, error) {
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if s.conf.StrictSNICheck && !matchDNSName(s.conf.dnsNames, ch.ServerName) {
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log.Info("DNS: TLS: unknown SNI in Client Hello: %s", ch.ServerName)
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return nil, fmt.Errorf("invalid SNI")
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}
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return &s.conf.cert, nil
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}
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