dnscrypt-proxy/dnscrypt-proxy/plugins.go

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package main
import (
"errors"
"net"
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"sync"
"github.com/jedisct1/dlog"
"github.com/miekg/dns"
)
type PluginsAction int
const (
PluginsActionNone = 0
PluginsActionForward = 1
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PluginsActionDrop = 2
PluginsActionReject = 3
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PluginsActionSynth = 4
)
type PluginsGlobals struct {
sync.RWMutex
queryPlugins *[]Plugin
responsePlugins *[]Plugin
}
type PluginsState struct {
sessionData map[string]interface{}
action PluginsAction
originalMaxPayloadSize int
maxPayloadSize int
clientProto string
clientAddr *net.Addr
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synthResponse *dns.Msg
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dnssec bool
cacheSize int
cacheNegTTL uint32
cacheMinTTL uint32
cacheMaxTTL uint32
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}
func InitPluginsGlobals(pluginsGlobals *PluginsGlobals, proxy *Proxy) error {
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queryPlugins := &[]Plugin{}
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if len(proxy.queryLogFile) != 0 {
*queryPlugins = append(*queryPlugins, Plugin(new(PluginQueryLog)))
}
if len(proxy.blockNameFile) != 0 {
*queryPlugins = append(*queryPlugins, Plugin(new(PluginBlockName)))
}
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if proxy.pluginBlockIPv6 {
*queryPlugins = append(*queryPlugins, Plugin(new(PluginBlockIPv6)))
}
*queryPlugins = append(*queryPlugins, Plugin(new(PluginGetSetPayloadSize)))
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if proxy.cache {
*queryPlugins = append(*queryPlugins, Plugin(new(PluginCache)))
}
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if len(proxy.forwardFile) != 0 {
*queryPlugins = append(*queryPlugins, Plugin(new(PluginForward)))
}
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responsePlugins := &[]Plugin{}
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if proxy.cache {
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*responsePlugins = append(*responsePlugins, Plugin(new(PluginCacheResponse)))
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}
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for _, plugin := range *queryPlugins {
if err := plugin.Init(proxy); err != nil {
return err
}
}
for _, plugin := range *responsePlugins {
if err := plugin.Init(proxy); err != nil {
return err
}
}
(*pluginsGlobals).queryPlugins = queryPlugins
(*pluginsGlobals).responsePlugins = responsePlugins
return nil
}
type Plugin interface {
Name() string
Description() string
Init(proxy *Proxy) error
Drop() error
Reload() error
Eval(pluginsState *PluginsState, msg *dns.Msg) error
}
func NewPluginsState(proxy *Proxy, clientProto string, clientAddr *net.Addr) PluginsState {
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return PluginsState{
action: PluginsActionForward,
maxPayloadSize: MaxDNSUDPPacketSize - ResponseOverhead,
clientProto: clientProto,
clientAddr: clientAddr,
cacheSize: proxy.cacheSize,
cacheNegTTL: proxy.cacheNegTTL,
cacheMinTTL: proxy.cacheMinTTL,
cacheMaxTTL: proxy.cacheMaxTTL,
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}
}
func (pluginsState *PluginsState) ApplyQueryPlugins(pluginsGlobals *PluginsGlobals, packet []byte) ([]byte, error) {
if len(*pluginsGlobals.queryPlugins) == 0 {
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return packet, nil
}
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pluginsState.action = PluginsActionForward
msg := dns.Msg{}
if err := msg.Unpack(packet); err != nil {
return packet, err
}
if len(msg.Question) > 1 {
return packet, errors.New("Unexpected number of questions")
}
pluginsGlobals.RLock()
for _, plugin := range *pluginsGlobals.queryPlugins {
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if ret := plugin.Eval(pluginsState, &msg); ret != nil {
pluginsGlobals.RUnlock()
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pluginsState.action = PluginsActionDrop
return packet, ret
}
if pluginsState.action == PluginsActionReject {
synth, err := RefusedResponseFromMessage(&msg)
if err != nil {
return nil, err
}
pluginsState.synthResponse = synth
}
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if pluginsState.action != PluginsActionForward {
break
}
}
pluginsGlobals.RUnlock()
packet2, err := msg.PackBuffer(packet)
if err != nil {
return packet, err
}
return packet2, nil
}
func (pluginsState *PluginsState) ApplyResponsePlugins(pluginsGlobals *PluginsGlobals, packet []byte) ([]byte, error) {
if len(*pluginsGlobals.responsePlugins) == 0 {
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return packet, nil
}
pluginsState.action = PluginsActionForward
msg := dns.Msg{}
if err := msg.Unpack(packet); err != nil {
return packet, err
}
pluginsGlobals.RLock()
for _, plugin := range *pluginsGlobals.responsePlugins {
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if ret := plugin.Eval(pluginsState, &msg); ret != nil {
pluginsGlobals.RUnlock()
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pluginsState.action = PluginsActionDrop
return packet, ret
}
if pluginsState.action == PluginsActionReject {
synth, err := RefusedResponseFromMessage(&msg)
if err != nil {
return nil, err
}
dlog.Infof("Blocking [%s]", synth.Question[0].Name)
pluginsState.synthResponse = synth
}
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if pluginsState.action != PluginsActionForward {
break
}
}
pluginsGlobals.RUnlock()
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packet2, err := msg.PackBuffer(packet)
if err != nil {
return packet, err
}
return packet2, nil
}