AdGuardHome/dnsfilter/dnsfilter.go

615 lines
15 KiB
Go

package dnsfilter
import (
"bytes"
"fmt"
"io/ioutil"
"net"
"net/http"
"os"
"runtime"
"strings"
"sync"
"github.com/AdguardTeam/dnsproxy/upstream"
"github.com/AdguardTeam/golibs/cache"
"github.com/AdguardTeam/golibs/log"
"github.com/AdguardTeam/urlfilter"
"github.com/miekg/dns"
)
// ServiceEntry - blocked service array element
type ServiceEntry struct {
Name string
Rules []*urlfilter.NetworkRule
}
// RequestFilteringSettings is custom filtering settings
type RequestFilteringSettings struct {
FilteringEnabled bool
SafeSearchEnabled bool
SafeBrowsingEnabled bool
ParentalEnabled bool
ServicesRules []ServiceEntry
}
// RewriteEntry is a rewrite array element
type RewriteEntry struct {
Domain string `yaml:"domain"`
Answer string `yaml:"answer"` // IP address or canonical name
}
// Config allows you to configure DNS filtering with New() or just change variables directly.
type Config struct {
ParentalSensitivity int `yaml:"parental_sensitivity"` // must be either 3, 10, 13 or 17
ParentalEnabled bool `yaml:"parental_enabled"`
SafeSearchEnabled bool `yaml:"safesearch_enabled"`
SafeBrowsingEnabled bool `yaml:"safebrowsing_enabled"`
ResolverAddress string `yaml:"-"` // DNS server address
SafeBrowsingCacheSize uint `yaml:"safebrowsing_cache_size"` // (in bytes)
SafeSearchCacheSize uint `yaml:"safesearch_cache_size"` // (in bytes)
ParentalCacheSize uint `yaml:"parental_cache_size"` // (in bytes)
CacheTime uint `yaml:"cache_time"` // Element's TTL (in minutes)
Rewrites []RewriteEntry `yaml:"rewrites"`
// Called when the configuration is changed by HTTP request
ConfigModified func() `yaml:"-"`
// Register an HTTP handler
HTTPRegister func(string, string, func(http.ResponseWriter, *http.Request)) `yaml:"-"`
}
// LookupStats store stats collected during safebrowsing or parental checks
type LookupStats struct {
Requests uint64 // number of HTTP requests that were sent
CacheHits uint64 // number of lookups that didn't need HTTP requests
Pending int64 // number of currently pending HTTP requests
PendingMax int64 // maximum number of pending HTTP requests
}
// Stats store LookupStats for safebrowsing, parental and safesearch
type Stats struct {
Safebrowsing LookupStats
Parental LookupStats
Safesearch LookupStats
}
// Parameters to pass to filters-initializer goroutine
type filtersInitializerParams struct {
filters map[int]string
}
// Dnsfilter holds added rules and performs hostname matches against the rules
type Dnsfilter struct {
rulesStorage *urlfilter.RuleStorage
filteringEngine *urlfilter.DNSEngine
engineLock sync.RWMutex
parentalServer string // access via methods
safeBrowsingServer string // access via methods
parentalUpstream upstream.Upstream
safeBrowsingUpstream upstream.Upstream
Config // for direct access by library users, even a = assignment
confLock sync.RWMutex
// Channel for passing data to filters-initializer goroutine
filtersInitializerChan chan filtersInitializerParams
filtersInitializerLock sync.Mutex
}
// Filter represents a filter list
type Filter struct {
ID int64 // auto-assigned when filter is added (see nextFilterID)
Data []byte `yaml:"-"` // List of rules divided by '\n'
FilePath string `yaml:"-"` // Path to a filtering rules file
}
// Reason holds an enum detailing why it was filtered or not filtered
type Reason int
const (
// reasons for not filtering
// NotFilteredNotFound - host was not find in any checks, default value for result
NotFilteredNotFound Reason = iota
// NotFilteredWhiteList - the host is explicitly whitelisted
NotFilteredWhiteList
// NotFilteredError - there was a transitive error during check
NotFilteredError
// reasons for filtering
// FilteredBlackList - the host was matched to be advertising host
FilteredBlackList
// FilteredSafeBrowsing - the host was matched to be malicious/phishing
FilteredSafeBrowsing
// FilteredParental - the host was matched to be outside of parental control settings
FilteredParental
// FilteredInvalid - the request was invalid and was not processed
FilteredInvalid
// FilteredSafeSearch - the host was replaced with safesearch variant
FilteredSafeSearch
// FilteredBlockedService - the host is blocked by "blocked services" settings
FilteredBlockedService
// ReasonRewrite - rewrite rule was applied
ReasonRewrite
)
var reasonNames = []string{
"NotFilteredNotFound",
"NotFilteredWhiteList",
"NotFilteredError",
"FilteredBlackList",
"FilteredSafeBrowsing",
"FilteredParental",
"FilteredInvalid",
"FilteredSafeSearch",
"FilteredBlockedService",
"Rewrite",
}
func (r Reason) String() string {
if uint(r) >= uint(len(reasonNames)) {
return ""
}
return reasonNames[r]
}
// GetConfig - get configuration
func (d *Dnsfilter) GetConfig() RequestFilteringSettings {
c := RequestFilteringSettings{}
// d.confLock.RLock()
c.SafeSearchEnabled = d.Config.SafeSearchEnabled
c.SafeBrowsingEnabled = d.Config.SafeBrowsingEnabled
c.ParentalEnabled = d.Config.ParentalEnabled
// d.confLock.RUnlock()
return c
}
// WriteDiskConfig - write configuration
func (d *Dnsfilter) WriteDiskConfig(c *Config) {
*c = d.Config
}
// SetFilters - set new filters (synchronously or asynchronously)
// When filters are set asynchronously, the old filters continue working until the new filters are ready.
// In this case the caller must ensure that the old filter files are intact.
func (d *Dnsfilter) SetFilters(filters map[int]string, async bool) error {
if async {
params := filtersInitializerParams{
filters: filters,
}
d.filtersInitializerLock.Lock() // prevent multiple writers from adding more than 1 task
// remove all pending tasks
stop := false
for !stop {
select {
case <-d.filtersInitializerChan:
//
default:
stop = true
}
}
d.filtersInitializerChan <- params
d.filtersInitializerLock.Unlock()
return nil
}
err := d.initFiltering(filters)
if err != nil {
log.Error("Can't initialize filtering subsystem: %s", err)
return err
}
return nil
}
// Starts initializing new filters by signal from channel
func (d *Dnsfilter) filtersInitializer() {
for {
params := <-d.filtersInitializerChan
err := d.initFiltering(params.filters)
if err != nil {
log.Error("Can't initialize filtering subsystem: %s", err)
continue
}
}
}
// Close - close the object
func (d *Dnsfilter) Close() {
if d.rulesStorage != nil {
d.rulesStorage.Close()
}
}
type dnsFilterContext struct {
stats Stats
safebrowsingCache cache.Cache
parentalCache cache.Cache
safeSearchCache cache.Cache
}
var gctx dnsFilterContext // global dnsfilter context
// Result holds state of hostname check
type Result struct {
IsFiltered bool `json:",omitempty"` // True if the host name is filtered
Reason Reason `json:",omitempty"` // Reason for blocking / unblocking
Rule string `json:",omitempty"` // Original rule text
IP net.IP `json:",omitempty"` // Not nil only in the case of a hosts file syntax
FilterID int64 `json:",omitempty"` // Filter ID the rule belongs to
// for ReasonRewrite:
CanonName string `json:",omitempty"` // CNAME value
IPList []net.IP `json:",omitempty"` // list of IP addresses
// for FilteredBlockedService:
ServiceName string `json:",omitempty"` // Name of the blocked service
}
// Matched can be used to see if any match at all was found, no matter filtered or not
func (r Reason) Matched() bool {
return r != NotFilteredNotFound
}
// CheckHost tries to match host against rules, then safebrowsing and parental if they are enabled
func (d *Dnsfilter) CheckHost(host string, qtype uint16, setts *RequestFilteringSettings) (Result, error) {
// sometimes DNS clients will try to resolve ".", which is a request to get root servers
if host == "" {
return Result{Reason: NotFilteredNotFound}, nil
}
host = strings.ToLower(host)
// prevent recursion
if host == d.parentalServer || host == d.safeBrowsingServer {
return Result{}, nil
}
var result Result
var err error
result = d.processRewrites(host, qtype)
if result.Reason == ReasonRewrite {
return result, nil
}
// try filter lists first
if setts.FilteringEnabled {
result, err = d.matchHost(host, qtype)
if err != nil {
return result, err
}
if result.Reason.Matched() {
return result, nil
}
}
if len(setts.ServicesRules) != 0 {
result = matchBlockedServicesRules(host, setts.ServicesRules)
if result.Reason.Matched() {
return result, nil
}
}
if setts.SafeSearchEnabled {
result, err = d.checkSafeSearch(host)
if err != nil {
log.Info("SafeSearch: failed: %v", err)
return Result{}, nil
}
if result.Reason.Matched() {
return result, nil
}
}
if setts.SafeBrowsingEnabled {
result, err = d.checkSafeBrowsing(host)
if err != nil {
log.Info("SafeBrowsing: failed: %v", err)
return Result{}, nil
}
if result.Reason.Matched() {
return result, nil
}
}
if setts.ParentalEnabled {
result, err = d.checkParental(host)
if err != nil {
log.Printf("Parental: failed: %v", err)
return Result{}, nil
}
if result.Reason.Matched() {
return result, nil
}
}
return Result{}, nil
}
// Process rewrites table
// . Find CNAME for a domain name
// . if found, set domain name to canonical name
// . Find A or AAAA record for a domain name
// . if found, return IP addresses
func (d *Dnsfilter) processRewrites(host string, qtype uint16) Result {
var res Result
d.confLock.RLock()
defer d.confLock.RUnlock()
for _, r := range d.Rewrites {
if r.Domain != host {
continue
}
ip := net.ParseIP(r.Answer)
if ip == nil {
log.Debug("Rewrite: CNAME for %s is %s", host, r.Answer)
host = r.Answer
res.CanonName = r.Answer
res.Reason = ReasonRewrite
break
}
}
for _, r := range d.Rewrites {
if r.Domain != host {
continue
}
ip := net.ParseIP(r.Answer)
if ip == nil {
continue
}
ip4 := ip.To4()
if qtype == dns.TypeA && ip4 != nil {
res.IPList = append(res.IPList, ip4)
log.Debug("Rewrite: A for %s is %s", host, ip4)
} else if qtype == dns.TypeAAAA && ip4 == nil {
res.IPList = append(res.IPList, ip)
log.Debug("Rewrite: AAAA for %s is %s", host, ip)
}
}
if len(res.IPList) != 0 {
res.Reason = ReasonRewrite
}
return res
}
func matchBlockedServicesRules(host string, svcs []ServiceEntry) Result {
req := urlfilter.NewRequestForHostname(host)
res := Result{}
for _, s := range svcs {
for _, rule := range s.Rules {
if rule.Match(req) {
res.Reason = FilteredBlockedService
res.IsFiltered = true
res.ServiceName = s.Name
res.Rule = rule.Text()
log.Debug("Blocked Services: matched rule: %s host: %s service: %s",
res.Rule, host, s.Name)
return res
}
}
}
return res
}
//
// Adding rule and matching against the rules
//
// Return TRUE if file exists
func fileExists(fn string) bool {
_, err := os.Stat(fn)
if err != nil {
return false
}
return true
}
// Initialize urlfilter objects
func (d *Dnsfilter) initFiltering(filters map[int]string) error {
listArray := []urlfilter.RuleList{}
for id, dataOrFilePath := range filters {
var list urlfilter.RuleList
if id == 0 {
list = &urlfilter.StringRuleList{
ID: 0,
RulesText: dataOrFilePath,
IgnoreCosmetic: true,
}
} else if !fileExists(dataOrFilePath) {
list = &urlfilter.StringRuleList{
ID: id,
IgnoreCosmetic: true,
}
} else if runtime.GOOS == "windows" {
// On Windows we don't pass a file to urlfilter because
// it's difficult to update this file while it's being used.
data, err := ioutil.ReadFile(dataOrFilePath)
if err != nil {
return fmt.Errorf("ioutil.ReadFile(): %s: %s", dataOrFilePath, err)
}
list = &urlfilter.StringRuleList{
ID: id,
RulesText: string(data),
IgnoreCosmetic: true,
}
} else {
var err error
list, err = urlfilter.NewFileRuleList(id, dataOrFilePath, true)
if err != nil {
return fmt.Errorf("urlfilter.NewFileRuleList(): %s: %s", dataOrFilePath, err)
}
}
listArray = append(listArray, list)
}
rulesStorage, err := urlfilter.NewRuleStorage(listArray)
if err != nil {
return fmt.Errorf("urlfilter.NewRuleStorage(): %s", err)
}
filteringEngine := urlfilter.NewDNSEngine(rulesStorage)
d.engineLock.Lock()
if d.rulesStorage != nil {
d.rulesStorage.Close()
}
d.rulesStorage = rulesStorage
d.filteringEngine = filteringEngine
d.engineLock.Unlock()
log.Debug("initialized filtering engine")
return nil
}
// matchHost is a low-level way to check only if hostname is filtered by rules, skipping expensive safebrowsing and parental lookups
func (d *Dnsfilter) matchHost(host string, qtype uint16) (Result, error) {
d.engineLock.RLock()
defer d.engineLock.RUnlock()
if d.filteringEngine == nil {
return Result{}, nil
}
rules, ok := d.filteringEngine.Match(host)
if !ok {
return Result{}, nil
}
log.Tracef("%d rules matched for host '%s'", len(rules), host)
for _, rule := range rules {
log.Tracef("Found rule for host '%s': '%s' list_id: %d",
host, rule.Text(), rule.GetFilterListID())
res := Result{}
res.Reason = FilteredBlackList
res.IsFiltered = true
res.FilterID = int64(rule.GetFilterListID())
res.Rule = rule.Text()
if netRule, ok := rule.(*urlfilter.NetworkRule); ok {
if netRule.Whitelist {
res.Reason = NotFilteredWhiteList
res.IsFiltered = false
}
return res, nil
} else if hostRule, ok := rule.(*urlfilter.HostRule); ok {
if qtype == dns.TypeA && hostRule.IP.To4() != nil {
// either IPv4 or IPv4-mapped IPv6 address
res.IP = hostRule.IP.To4()
return res, nil
} else if qtype == dns.TypeAAAA {
ip4 := hostRule.IP.To4()
if ip4 == nil {
res.IP = hostRule.IP
return res, nil
}
if bytes.Equal(ip4, []byte{0, 0, 0, 0}) {
// send IP="::" response for a rule "0.0.0.0 blockdomain"
res.IP = net.IPv6zero
return res, nil
}
}
continue
} else {
log.Tracef("Rule type is unsupported: '%s' list_id: %d",
rule.Text(), rule.GetFilterListID())
}
}
return Result{}, nil
}
// New creates properly initialized DNS Filter that is ready to be used
func New(c *Config, filters map[int]string) *Dnsfilter {
if c != nil {
cacheConf := cache.Config{
EnableLRU: true,
}
// initialize objects only once
if gctx.safebrowsingCache == nil {
cacheConf.MaxSize = c.SafeBrowsingCacheSize
gctx.safebrowsingCache = cache.New(cacheConf)
}
if gctx.safeSearchCache == nil {
cacheConf.MaxSize = c.SafeSearchCacheSize
gctx.safeSearchCache = cache.New(cacheConf)
}
if gctx.parentalCache == nil {
cacheConf.MaxSize = c.ParentalCacheSize
gctx.parentalCache = cache.New(cacheConf)
}
}
d := new(Dnsfilter)
err := d.initSecurityServices()
if err != nil {
log.Error("dnsfilter: initialize services: %s", err)
return nil
}
if c != nil {
d.Config = *c
}
if filters != nil {
err := d.initFiltering(filters)
if err != nil {
log.Error("Can't initialize filtering subsystem: %s", err)
d.Close()
return nil
}
}
d.filtersInitializerChan = make(chan filtersInitializerParams, 1)
go d.filtersInitializer()
if d.Config.HTTPRegister != nil { // for tests
d.registerSecurityHandlers()
d.registerRewritesHandlers()
}
return d
}
//
// stats
//
// GetStats return dns filtering stats since startup
func (d *Dnsfilter) GetStats() Stats {
return gctx.stats
}