485 lines
16 KiB
Go
485 lines
16 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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"fmt"
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"net"
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"net/http"
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"os"
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"sort"
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"strings"
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"time"
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"github.com/AdguardTeam/AdGuardHome/internal/filtering"
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"github.com/AdguardTeam/dnsproxy/proxy"
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"github.com/AdguardTeam/dnsproxy/upstream"
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"github.com/AdguardTeam/golibs/errors"
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"github.com/AdguardTeam/golibs/log"
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"github.com/AdguardTeam/golibs/netutil"
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"github.com/AdguardTeam/golibs/stringutil"
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"github.com/AdguardTeam/golibs/timeutil"
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"github.com/ameshkov/dnscrypt/v2"
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)
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// BlockingMode is an enum of all allowed blocking modes.
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type BlockingMode string
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// Allowed blocking modes.
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const (
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// BlockingModeCustomIP means respond with a custom IP address.
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BlockingModeCustomIP BlockingMode = "custom_ip"
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// BlockingModeDefault is the same as BlockingModeNullIP for
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// Adblock-style rules, but responds with the IP address specified in
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// the rule when blocked by an `/etc/hosts`-style rule.
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BlockingModeDefault BlockingMode = "default"
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// BlockingModeNullIP means respond with a zero IP address: "0.0.0.0"
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// for A requests and "::" for AAAA ones.
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BlockingModeNullIP BlockingMode = "null_ip"
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// BlockingModeNXDOMAIN means respond with the NXDOMAIN code.
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BlockingModeNXDOMAIN BlockingMode = "nxdomain"
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// BlockingModeREFUSED means respond with the REFUSED code.
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BlockingModeREFUSED BlockingMode = "refused"
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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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// FilterHandler is an optional additional filtering callback.
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FilterHandler func(clientAddr net.IP, clientID string, settings *filtering.Settings) `yaml:"-"`
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// GetCustomUpstreamByClient is a callback that returns upstreams
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// configuration based on the client IP address or ClientID. It returns
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// nil if there are no custom upstreams for the client.
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GetCustomUpstreamByClient func(id string) (conf *proxy.UpstreamConfig, err error) `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 filtering features
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BlockingMode BlockingMode `yaml:"blocking_mode"` // mode how to answer filtered requests
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BlockingIPv4 net.IP `yaml:"blocking_ipv4"` // IP address to be returned for a blocked A request
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BlockingIPv6 net.IP `yaml:"blocking_ipv6"` // IP address to be returned for a blocked AAAA request
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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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UpstreamDNSFileName string `yaml:"upstream_dns_file"`
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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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// FastestTimeout replaces the default timeout for dialing IP addresses
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// when FastestAddr is true.
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FastestTimeout timeutil.Duration `yaml:"fastest_timeout"`
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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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// TrustedProxies is the list of IP addresses and CIDR networks to
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// detect proxy servers addresses the DoH requests from which should be
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// handled. The value of nil or an empty slice for this field makes
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// Proxy not trust any address.
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TrustedProxies []string `yaml:"trusted_proxies"`
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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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// CacheOptimistic defines if optimistic cache mechanism should be used.
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CacheOptimistic bool `yaml:"cache_optimistic"`
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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 AD flag in outcoming DNS request
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EnableEDNSClientSubnet bool `yaml:"edns_client_subnet"` // Enable EDNS Client Subnet option
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MaxGoroutines uint32 `yaml:"max_goroutines"` // Max. number of parallel goroutines for processing incoming requests
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// IpsetList is the ipset configuration that allows AdGuard Home to add
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// IP addresses of the specified domain names to an ipset list. Syntax:
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//
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// DOMAIN[,DOMAIN].../IPSET_NAME
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//
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IpsetList []string `yaml:"ipset"`
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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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TLSListenAddrs []*net.TCPAddr `yaml:"-" json:"-"`
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QUICListenAddrs []*net.UDPAddr `yaml:"-" json:"-"`
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// Reject connection if the client uses server name (in SNI) that doesn't match the certificate
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StrictSNICheck bool `yaml:"strict_sni_check" json:"-"`
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// PEM-encoded certificates chain
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CertificateChain string `yaml:"certificate_chain" json:"certificate_chain"`
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// PEM-encoded private key
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PrivateKey string `yaml:"private_key" json:"private_key"`
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CertificatePath string `yaml:"certificate_path" json:"certificate_path"`
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PrivateKeyPath string `yaml:"private_key_path" json:"private_key_path"`
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CertificateChainData []byte `yaml:"-" json:"-"`
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PrivateKeyData []byte `yaml:"-" json:"-"`
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// ServerName is the hostname of the server. Currently, it is only
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// being used for client ID checking.
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ServerName string `yaml:"-" json:"-"`
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cert tls.Certificate
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// DNS names from certificate (SAN) or CN value from Subject
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dnsNames []string
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}
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// DNSCryptConfig is the DNSCrypt server configuration struct.
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type DNSCryptConfig struct {
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UDPListenAddrs []*net.UDPAddr
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TCPListenAddrs []*net.TCPAddr
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ProviderName string
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ResolverCert *dnscrypt.Cert
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Enabled bool
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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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UDPListenAddrs []*net.UDPAddr // UDP listen address
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TCPListenAddrs []*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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DNSCryptConfig
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TLSAllowUnencryptedDoH bool
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// UpstreamTimeout is the timeout for querying upstream servers.
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UpstreamTimeout time.Duration
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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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// ResolveClients signals if the RDNS should resolve clients' addresses.
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ResolveClients bool
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// UsePrivateRDNS defines if the PTR requests for unknown addresses from
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// locally-served networks should be resolved via private PTR resolvers.
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UsePrivateRDNS bool
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// LocalPTRResolvers is a slice of addresses to be used as upstreams for
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// resolving PTR queries for local addresses.
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LocalPTRResolvers []string
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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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UDPListenAddrs: []*net.UDPAddr{{Port: 53}},
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TCPListenAddrs: []*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.UDPListenAddrs,
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TCPListenAddr: s.conf.TCPListenAddrs,
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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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TrustedProxies: s.conf.TrustedProxies,
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CacheMinTTL: s.conf.CacheMinTTL,
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CacheMaxTTL: s.conf.CacheMaxTTL,
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CacheOptimistic: s.conf.CacheOptimistic,
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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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EnableEDNSClientSubnet: s.conf.EnableEDNSClientSubnet,
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MaxGoroutines: int(s.conf.MaxGoroutines),
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}
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if s.conf.CacheSize != 0 {
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proxyConfig.CacheEnabled = true
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proxyConfig.CacheSizeBytes = int(s.conf.CacheSize)
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}
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proxyConfig.UpstreamMode = proxy.UModeLoadBalance
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if s.conf.AllServers {
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proxyConfig.UpstreamMode = proxy.UModeParallel
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} else if s.conf.FastestAddr {
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proxyConfig.UpstreamMode = proxy.UModeFastestAddr
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proxyConfig.FastestPingTimeout = s.conf.FastestTimeout.Duration
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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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if s.conf.DNSCryptConfig.Enabled {
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proxyConfig.DNSCryptUDPListenAddr = s.conf.DNSCryptConfig.UDPListenAddrs
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proxyConfig.DNSCryptTCPListenAddr = s.conf.DNSCryptConfig.TCPListenAddrs
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proxyConfig.DNSCryptProviderName = s.conf.DNSCryptConfig.ProviderName
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proxyConfig.DNSCryptResolverCert = s.conf.DNSCryptConfig.ResolverCert
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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.Error("no default 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.UDPListenAddrs == nil {
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s.conf.UDPListenAddrs = defaultValues.UDPListenAddrs
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}
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if s.conf.TCPListenAddrs == nil {
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s.conf.TCPListenAddrs = defaultValues.TCPListenAddrs
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}
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if len(s.conf.BlockedHosts) == 0 {
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s.conf.BlockedHosts = defaultBlockedHosts
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}
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if s.conf.UpstreamTimeout == 0 {
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s.conf.UpstreamTimeout = DefaultTimeout
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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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// We're setting a customized set of RootCAs
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// The reason is that Go default mechanism of loading TLS roots
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// does not always work properly on some routers so we're
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// loading roots manually and pass it here.
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// See "util.LoadSystemRootCAs"
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upstream.RootCAs = s.conf.TLSv12Roots
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// See util.InitTLSCiphers -- removed unsafe ciphers
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if len(s.conf.TLSCiphers) > 0 {
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upstream.CipherSuites = s.conf.TLSCiphers
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}
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// Load upstreams either from the file, or from the settings
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var upstreams []string
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if s.conf.UpstreamDNSFileName != "" {
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data, err := os.ReadFile(s.conf.UpstreamDNSFileName)
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if err != nil {
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return err
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}
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upstreams = stringutil.SplitTrimmed(string(data), "\n")
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log.Debug("dns: using %d upstream servers from file %s", len(upstreams), s.conf.UpstreamDNSFileName)
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} else {
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upstreams = s.conf.UpstreamDNS
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}
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upstreams = stringutil.FilterOut(upstreams, IsCommentOrEmpty)
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upstreamConfig, err := proxy.ParseUpstreamsConfig(
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upstreams,
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&upstream.Options{
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Bootstrap: s.conf.BootstrapDNS,
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Timeout: s.conf.UpstreamTimeout,
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},
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)
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if err != nil {
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return fmt.Errorf("dns: proxy.ParseUpstreamsConfig: %w", err)
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}
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if len(upstreamConfig.Upstreams) == 0 {
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log.Info("warning: no default upstream servers specified, using %v", defaultDNS)
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var uc *proxy.UpstreamConfig
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uc, err = proxy.ParseUpstreamsConfig(
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defaultDNS,
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&upstream.Options{
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Bootstrap: s.conf.BootstrapDNS,
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Timeout: s.conf.UpstreamTimeout,
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},
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)
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if err != nil {
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return fmt.Errorf("dns: failed to parse default upstreams: %v", err)
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}
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upstreamConfig.Upstreams = uc.Upstreams
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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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s.internalProxy = &proxy.Proxy{
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Config: 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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}
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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 len(s.conf.CertificateChainData) == 0 || len(s.conf.PrivateKeyData) == 0 {
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return nil
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}
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if s.conf.TLSListenAddrs == nil && s.conf.QUICListenAddrs == nil {
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return nil
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}
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if s.conf.TLSListenAddrs != nil {
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proxyConfig.TLSListenAddr = s.conf.TLSListenAddrs
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}
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if s.conf.QUICListenAddrs != nil {
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proxyConfig.QUICListenAddr = s.conf.QUICListenAddrs
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}
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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 fmt.Errorf("failed to parse TLS keypair: %w", err)
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}
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if s.conf.StrictSNICheck {
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var x *x509.Certificate
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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 fmt.Errorf("x509.ParseCertificate(): %w", 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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return nil
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}
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// isInSorted returns true if s is in the sorted slice strs.
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func isInSorted(strs []string, s string) (ok bool) {
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i := sort.SearchStrings(strs, s)
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if i == len(strs) || strs[i] != s {
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return false
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}
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return true
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}
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// isWildcard returns true if host is a wildcard hostname.
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func isWildcard(host string) (ok bool) {
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return len(host) >= 2 && host[0] == '*' && host[1] == '.'
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}
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// matchesDomainWildcard returns true if host matches the domain wildcard
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// pattern pat.
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func matchesDomainWildcard(host, pat string) (ok bool) {
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return isWildcard(pat) && strings.HasSuffix(host, pat[1:])
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}
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// anyNameMatches returns true if sni, the client's SNI value, matches any of
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// the DNS names and patterns from certificate. dnsNames must be sorted.
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func anyNameMatches(dnsNames []string, sni string) (ok bool) {
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if netutil.ValidateDomainName(sni) != nil {
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return false
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}
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if isInSorted(dnsNames, sni) {
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return true
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}
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for _, dn := range dnsNames {
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if matchesDomainWildcard(sni, dn) {
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return true
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}
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}
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return false
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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 && !anyNameMatches(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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