135 lines
3.5 KiB
Go
135 lines
3.5 KiB
Go
package fakedns
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import (
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"context"
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"math"
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"math/big"
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gonet "net"
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"time"
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"github.com/xtls/xray-core/common"
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"github.com/xtls/xray-core/common/cache"
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"github.com/xtls/xray-core/common/net"
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"github.com/xtls/xray-core/features/dns"
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)
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type Holder struct {
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domainToIP cache.Lru
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ipRange *gonet.IPNet
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config *FakeDnsPool
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}
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func (*Holder) Type() interface{} {
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return (*dns.FakeDNSEngine)(nil)
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}
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func (fkdns *Holder) Start() error {
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return fkdns.initializeFromConfig()
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}
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func (fkdns *Holder) Close() error {
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fkdns.domainToIP = nil
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fkdns.ipRange = nil
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return nil
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}
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func NewFakeDNSHolder() (*Holder, error) {
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var fkdns *Holder
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var err error
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if fkdns, err = NewFakeDNSHolderConfigOnly(nil); err != nil {
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return nil, newError("Unable to create Fake Dns Engine").Base(err).AtError()
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}
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err = fkdns.initialize(dns.FakeIPPool, 65535)
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if err != nil {
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return nil, err
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}
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return fkdns, nil
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}
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func NewFakeDNSHolderConfigOnly(conf *FakeDnsPool) (*Holder, error) {
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return &Holder{nil, nil, conf}, nil
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}
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func (fkdns *Holder) initializeFromConfig() error {
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return fkdns.initialize(fkdns.config.IpPool, int(fkdns.config.LruSize))
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}
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func (fkdns *Holder) initialize(ipPoolCidr string, lruSize int) error {
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var ipRange *gonet.IPNet
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var err error
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if _, ipRange, err = gonet.ParseCIDR(ipPoolCidr); err != nil {
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return newError("Unable to parse CIDR for Fake DNS IP assignment").Base(err).AtError()
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}
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ones, bits := ipRange.Mask.Size()
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rooms := bits - ones
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if math.Log2(float64(lruSize)) >= float64(rooms) {
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return newError("LRU size is bigger than subnet size").AtError()
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}
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fkdns.domainToIP = cache.NewLru(lruSize)
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fkdns.ipRange = ipRange
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return nil
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}
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// GetFakeIPForDomain check and generate a fake IP for a domain name
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func (fkdns *Holder) GetFakeIPForDomain(domain string) []net.Address {
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if v, ok := fkdns.domainToIP.Get(domain); ok {
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return []net.Address{v.(net.Address)}
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}
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currentTimeMillis := uint64(time.Now().UnixNano() / 1e6)
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ones, bits := fkdns.ipRange.Mask.Size()
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rooms := bits - ones
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if rooms < 64 {
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currentTimeMillis %= (uint64(1) << rooms)
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}
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bigIntIP := big.NewInt(0).SetBytes(fkdns.ipRange.IP)
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bigIntIP = bigIntIP.Add(bigIntIP, new(big.Int).SetUint64(currentTimeMillis))
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var ip net.Address
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for {
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ip = net.IPAddress(bigIntIP.Bytes())
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// if we run for a long time, we may go back to beginning and start seeing the IP in use
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if _, ok := fkdns.domainToIP.PeekKeyFromValue(ip); !ok {
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break
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}
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bigIntIP = bigIntIP.Add(bigIntIP, big.NewInt(1))
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if !fkdns.ipRange.Contains(bigIntIP.Bytes()) {
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bigIntIP = big.NewInt(0).SetBytes(fkdns.ipRange.IP)
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}
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}
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fkdns.domainToIP.Put(domain, ip)
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return []net.Address{ip}
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}
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// GetDomainFromFakeDNS check if an IP is a fake IP and have corresponding domain name
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func (fkdns *Holder) GetDomainFromFakeDNS(ip net.Address) string {
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if !ip.Family().IsIP() || !fkdns.ipRange.Contains(ip.IP()) {
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return ""
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}
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if k, ok := fkdns.domainToIP.GetKeyFromValue(ip); ok {
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return k.(string)
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}
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newError("A fake ip request to ", ip, ", however there is no matching domain name in fake DNS").AtInfo().WriteToLog()
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return ""
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}
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// GetFakeIPRange return fake IP range from configuration
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func (fkdns *Holder) GetFakeIPRange() *gonet.IPNet {
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return fkdns.ipRange
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}
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func init() {
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common.Must(common.RegisterConfig((*FakeDnsPool)(nil), func(ctx context.Context, config interface{}) (interface{}, error) {
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var f *Holder
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var err error
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if f, err = NewFakeDNSHolderConfigOnly(config.(*FakeDnsPool)); err != nil {
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return nil, err
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}
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return f, nil
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}))
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}
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