AdGuardHome/dnsfilter/dnsfilter.go

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package dnsfilter
import (
"bufio"
"bytes"
"context"
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"crypto/sha256"
"encoding/binary"
"encoding/gob"
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"encoding/json"
"fmt"
"io/ioutil"
"net"
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"net/http"
"os"
"runtime"
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"strings"
"sync"
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"sync/atomic"
"time"
"github.com/joomcode/errorx"
"github.com/AdguardTeam/dnsproxy/upstream"
"github.com/AdguardTeam/golibs/cache"
"github.com/AdguardTeam/golibs/log"
"github.com/AdguardTeam/urlfilter"
"github.com/bluele/gcache"
"github.com/miekg/dns"
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"golang.org/x/net/publicsuffix"
)
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const defaultHTTPTimeout = 5 * time.Minute
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const defaultHTTPMaxIdleConnections = 100
const defaultSafebrowsingServer = "sb.adtidy.org"
const defaultSafebrowsingURL = "%s://%s/safebrowsing-lookup-hash.html?prefixes=%s"
const defaultParentalServer = "pctrl.adguard.com"
const defaultParentalURL = "%s://%s/check-parental-control-hash?prefixes=%s&sensitivity=%d"
const defaultParentalSensitivity = 13 // use "TEEN" by default
const maxDialCacheSize = 2 // the number of host names for safebrowsing and parental control
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// ServiceEntry - blocked service array element
type ServiceEntry struct {
Name string
Rules []*urlfilter.NetworkRule
}
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// RequestFilteringSettings is custom filtering settings
type RequestFilteringSettings struct {
FilteringEnabled bool
SafeSearchEnabled bool
SafeBrowsingEnabled bool
ParentalEnabled bool
ServicesRules []ServiceEntry
}
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// RewriteEntry is a rewrite array element
type RewriteEntry struct {
Domain string `yaml:"domain"`
Answer string `yaml:"answer"` // IP address or canonical name
}
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// 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"`
UsePlainHTTP bool `yaml:"-"` // use plain HTTP for requests to parental and safe browsing servers
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)
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Rewrites []RewriteEntry `yaml:"rewrites"`
// Called when the configuration is changed by HTTP request
ConfigModified func() `yaml:"-"`
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// Register an HTTP handler
HTTPRegister func(string, string, func(http.ResponseWriter, *http.Request)) `yaml:"-"`
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}
// LookupStats store stats collected during safebrowsing or parental checks
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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
}
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// Stats store LookupStats for safebrowsing, parental and safesearch
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type Stats struct {
Safebrowsing LookupStats
Parental LookupStats
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Safesearch LookupStats
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}
// Parameters to pass to filters-initializer goroutine
type filtersInitializerParams struct {
filters map[int]string
}
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// Dnsfilter holds added rules and performs hostname matches against the rules
type Dnsfilter struct {
rulesStorage *urlfilter.RuleStorage
filteringEngine *urlfilter.DNSEngine
engineLock sync.RWMutex
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// HTTP lookups for safebrowsing and parental
client http.Client // handle for http client -- single instance as recommended by docs
transport *http.Transport // handle for http transport used by http client
parentalServer string // access via methods
safeBrowsingServer string // access via methods
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
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}
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// 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
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type Reason int
const (
// reasons for not filtering
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// 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
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// reasons for filtering
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// 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
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// ReasonRewrite - rewrite rule was applied
ReasonRewrite
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)
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
}
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// 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,
}
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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 != nil && d.transport != nil {
d.transport.CloseIdleConnections()
}
if d.rulesStorage != nil {
d.rulesStorage.Close()
}
}
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type dnsFilterContext struct {
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stats Stats
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dialCache gcache.Cache // "host" -> "IP" cache for safebrowsing and parental control servers
safebrowsingCache cache.Cache
parentalCache cache.Cache
safeSearchCache cache.Cache
}
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var gctx dnsFilterContext // global dnsfilter context
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// Result holds state of hostname check
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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
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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
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// 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
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}
// Matched can be used to see if any match at all was found, no matter filtered or not
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func (r Reason) Matched() bool {
return r != NotFilteredNotFound
}
// CheckHost tries to match host against rules, then safebrowsing and parental if they are enabled
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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
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if host == "" {
return Result{Reason: NotFilteredNotFound}, nil
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}
host = strings.ToLower(host)
// prevent recursion
if host == d.parentalServer || host == d.safeBrowsingServer {
return Result{}, nil
}
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var result Result
var err error
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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
}
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}
if len(setts.ServicesRules) != 0 {
result = matchBlockedServicesRules(host, setts.ServicesRules)
if result.Reason.Matched() {
return result, nil
}
}
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// check safeSearch if no match
if setts.SafeSearchEnabled {
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result, err = d.checkSafeSearch(host)
if err != nil {
log.Printf("Failed to safesearch HTTP lookup, ignoring check: %v", err)
return Result{}, nil
}
if result.Reason.Matched() {
return result, nil
}
}
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// check safebrowsing if no match
if setts.SafeBrowsingEnabled {
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result, err = d.checkSafeBrowsing(host)
if err != nil {
// failed to do HTTP lookup -- treat it as if we got empty response, but don't save cache
log.Printf("Failed to do safebrowsing HTTP lookup, ignoring check: %v", err)
return Result{}, nil
}
if result.Reason.Matched() {
return result, nil
}
}
// check parental if no match
if setts.ParentalEnabled {
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result, err = d.checkParental(host)
if err != nil {
// failed to do HTTP lookup -- treat it as if we got empty response, but don't save cache
log.Printf("Failed to do parental HTTP lookup, ignoring check: %v", err)
return Result{}, nil
}
if result.Reason.Matched() {
return result, nil
}
}
// nothing matched, return nothing
return Result{}, nil
}
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// 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()
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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
}
/*
expire byte[4]
res Result
*/
func (d *Dnsfilter) setCacheResult(cache cache.Cache, host string, res Result) {
var buf bytes.Buffer
expire := uint(time.Now().Unix()) + d.Config.CacheTime*60
var exp []byte
exp = make([]byte, 4)
binary.BigEndian.PutUint32(exp, uint32(expire))
_, _ = buf.Write(exp)
enc := gob.NewEncoder(&buf)
err := enc.Encode(res)
if err != nil {
log.Error("gob.Encode(): %s", err)
return
}
_ = cache.Set([]byte(host), buf.Bytes())
log.Debug("Stored in cache %p: %s", cache, host)
}
func getCachedResult(cache cache.Cache, host string) (Result, bool) {
data := cache.Get([]byte(host))
if data == nil {
return Result{}, false
}
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exp := int(binary.BigEndian.Uint32(data[:4]))
if exp <= int(time.Now().Unix()) {
cache.Del([]byte(host))
return Result{}, false
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}
var buf bytes.Buffer
buf.Write(data[4:])
dec := gob.NewDecoder(&buf)
r := Result{}
err := dec.Decode(&r)
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if err != nil {
log.Debug("gob.Decode(): %s", err)
return Result{}, false
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}
return r, true
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}
// for each dot, hash it and add it to string
func hostnameToHashParam(host string, addslash bool) (string, map[string]bool) {
var hashparam bytes.Buffer
hashes := map[string]bool{}
tld, icann := publicsuffix.PublicSuffix(host)
if !icann {
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// private suffixes like cloudfront.net
tld = ""
}
curhost := host
for {
if curhost == "" {
// we've reached end of string
break
}
if tld != "" && curhost == tld {
// we've reached the TLD, don't hash it
break
}
tohash := []byte(curhost)
if addslash {
tohash = append(tohash, '/')
}
sum := sha256.Sum256(tohash)
hexhash := fmt.Sprintf("%X", sum)
hashes[hexhash] = true
hashparam.WriteString(fmt.Sprintf("%02X%02X%02X%02X/", sum[0], sum[1], sum[2], sum[3]))
pos := strings.IndexByte(curhost, byte('.'))
if pos < 0 {
break
}
curhost = curhost[pos+1:]
}
return hashparam.String(), hashes
}
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func (d *Dnsfilter) checkSafeSearch(host string) (Result, error) {
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if log.GetLevel() >= log.DEBUG {
timer := log.StartTimer()
defer timer.LogElapsed("SafeSearch HTTP lookup for %s", host)
}
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// Check cache. Return cached result if it was found
cachedValue, isFound := getCachedResult(gctx.safeSearchCache, host)
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if isFound {
atomic.AddUint64(&gctx.stats.Safesearch.CacheHits, 1)
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log.Tracef("%s: found in SafeSearch cache", host)
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return cachedValue, nil
}
safeHost, ok := d.SafeSearchDomain(host)
if !ok {
return Result{}, nil
}
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res := Result{IsFiltered: true, Reason: FilteredSafeSearch}
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if ip := net.ParseIP(safeHost); ip != nil {
res.IP = ip
d.setCacheResult(gctx.safeSearchCache, host, res)
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return res, nil
}
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// TODO this address should be resolved with upstream that was configured in dnsforward
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addrs, err := net.LookupIP(safeHost)
if err != nil {
log.Tracef("SafeSearchDomain for %s was found but failed to lookup for %s cause %s", host, safeHost, err)
return Result{}, err
}
for _, i := range addrs {
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if ipv4 := i.To4(); ipv4 != nil {
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res.IP = ipv4
break
}
}
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if len(res.IP) == 0 {
return Result{}, fmt.Errorf("no ipv4 addresses in safe search response for %s", safeHost)
}
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// Cache result
d.setCacheResult(gctx.safeSearchCache, host, res)
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return res, nil
}
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func (d *Dnsfilter) checkSafeBrowsing(host string) (Result, error) {
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if log.GetLevel() >= log.DEBUG {
timer := log.StartTimer()
defer timer.LogElapsed("SafeBrowsing HTTP lookup for %s", host)
}
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format := func(hashparam string) string {
schema := "https"
if d.UsePlainHTTP {
schema = "http"
}
url := fmt.Sprintf(defaultSafebrowsingURL, schema, d.safeBrowsingServer, hashparam)
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return url
}
handleBody := func(body []byte, hashes map[string]bool) (Result, error) {
result := Result{}
scanner := bufio.NewScanner(strings.NewReader(string(body)))
for scanner.Scan() {
line := scanner.Text()
splitted := strings.Split(line, ":")
if len(splitted) < 3 {
continue
}
hash := splitted[2]
if _, ok := hashes[hash]; ok {
// it's in the hash
result.IsFiltered = true
result.Reason = FilteredSafeBrowsing
result.Rule = splitted[0]
break
}
}
if err := scanner.Err(); err != nil {
// error, don't save cache
return Result{}, err
}
return result, nil
}
// check cache
cachedValue, isFound := getCachedResult(gctx.safebrowsingCache, host)
if isFound {
atomic.AddUint64(&gctx.stats.Safebrowsing.CacheHits, 1)
log.Tracef("%s: found in the lookup cache %p", host, gctx.safebrowsingCache)
return cachedValue, nil
}
result, err := d.lookupCommon(host, &gctx.stats.Safebrowsing, true, format, handleBody)
if err == nil {
d.setCacheResult(gctx.safebrowsingCache, host, result)
}
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return result, err
}
func (d *Dnsfilter) checkParental(host string) (Result, error) {
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if log.GetLevel() >= log.DEBUG {
timer := log.StartTimer()
defer timer.LogElapsed("Parental HTTP lookup for %s", host)
}
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format := func(hashparam string) string {
schema := "https"
if d.UsePlainHTTP {
schema = "http"
}
sensitivity := d.ParentalSensitivity
if sensitivity == 0 {
sensitivity = defaultParentalSensitivity
}
url := fmt.Sprintf(defaultParentalURL, schema, d.parentalServer, hashparam, sensitivity)
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return url
}
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handleBody := func(body []byte, hashes map[string]bool) (Result, error) {
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// parse json
var m []struct {
Blocked bool `json:"blocked"`
ClientTTL int `json:"clientTtl"`
Reason string `json:"reason"`
Hash string `json:"hash"`
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}
err := json.Unmarshal(body, &m)
if err != nil {
// error, don't save cache
log.Printf("Couldn't parse json '%s': %s", body, err)
return Result{}, err
}
result := Result{}
for i := range m {
if !hashes[m[i].Hash] {
continue
}
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if m[i].Blocked {
result.IsFiltered = true
result.Reason = FilteredParental
result.Rule = fmt.Sprintf("parental %s", m[i].Reason)
break
}
}
return result, nil
}
// check cache
cachedValue, isFound := getCachedResult(gctx.parentalCache, host)
if isFound {
atomic.AddUint64(&gctx.stats.Parental.CacheHits, 1)
log.Tracef("%s: found in the lookup cache %p", host, gctx.parentalCache)
return cachedValue, nil
}
result, err := d.lookupCommon(host, &gctx.stats.Parental, false, format, handleBody)
if err == nil {
d.setCacheResult(gctx.parentalCache, host, result)
}
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return result, err
}
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type formatHandler func(hashparam string) string
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type bodyHandler func(body []byte, hashes map[string]bool) (Result, error)
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// real implementation of lookup/check
func (d *Dnsfilter) lookupCommon(host string, lookupstats *LookupStats, hashparamNeedSlash bool, format formatHandler, handleBody bodyHandler) (Result, error) {
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// convert hostname to hash parameters
hashparam, hashes := hostnameToHashParam(host, hashparamNeedSlash)
// format URL with our hashes
url := format(hashparam)
// do HTTP request
atomic.AddUint64(&lookupstats.Requests, 1)
atomic.AddInt64(&lookupstats.Pending, 1)
updateMax(&lookupstats.Pending, &lookupstats.PendingMax)
resp, err := d.client.Get(url)
atomic.AddInt64(&lookupstats.Pending, -1)
if resp != nil && resp.Body != nil {
defer resp.Body.Close()
}
if err != nil {
// error, don't save cache
return Result{}, err
}
// get body text
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
// error, don't save cache
return Result{}, err
}
// handle status code
switch {
case resp.StatusCode == 204:
// empty result, save cache
return Result{}, nil
case resp.StatusCode != 200:
return Result{}, fmt.Errorf("HTTP status code: %d", resp.StatusCode)
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}
result, err := handleBody(body, hashes)
if err != nil {
return Result{}, err
}
return result, nil
}
//
// 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
}
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// 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())
}
}
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return Result{}, nil
}
//
// lifecycle helper functions
//
// Return TRUE if this host's IP should be cached
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func (d *Dnsfilter) shouldBeInDialCache(host string) bool {
return host == d.safeBrowsingServer ||
host == d.parentalServer
}
// Search for an IP address by host name
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func searchInDialCache(host string) string {
rawValue, err := gctx.dialCache.Get(host)
if err != nil {
return ""
}
ip, _ := rawValue.(string)
log.Debug("Found in cache: %s -> %s", host, ip)
return ip
}
// Add "hostname" -> "IP address" entry to cache
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func addToDialCache(host, ip string) {
err := gctx.dialCache.Set(host, ip)
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if err != nil {
log.Debug("dialCache.Set: %s", err)
}
log.Debug("Added to cache: %s -> %s", host, ip)
}
type dialFunctionType func(ctx context.Context, network, addr string) (net.Conn, error)
// Connect to a remote server resolving hostname using our own DNS server
func (d *Dnsfilter) createCustomDialContext(resolverAddr string) dialFunctionType {
return func(ctx context.Context, network, addr string) (net.Conn, error) {
log.Tracef("network:%v addr:%v", network, addr)
host, port, err := net.SplitHostPort(addr)
if err != nil {
return nil, err
}
dialer := &net.Dialer{
Timeout: time.Minute * 5,
}
if net.ParseIP(host) != nil {
con, err := dialer.DialContext(ctx, network, addr)
return con, err
}
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cache := d.shouldBeInDialCache(host)
if cache {
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ip := searchInDialCache(host)
if len(ip) != 0 {
addr = fmt.Sprintf("%s:%s", ip, port)
return dialer.DialContext(ctx, network, addr)
}
}
r := upstream.NewResolver(resolverAddr, 30*time.Second)
addrs, e := r.LookupIPAddr(ctx, host)
log.Tracef("LookupIPAddr: %s: %v", host, addrs)
if e != nil {
return nil, e
}
if len(addrs) == 0 {
return nil, fmt.Errorf("couldn't lookup host: %s", host)
}
var dialErrs []error
for _, a := range addrs {
addr = fmt.Sprintf("%s:%s", a.String(), port)
con, err := dialer.DialContext(ctx, network, addr)
if err != nil {
dialErrs = append(dialErrs, err)
continue
}
if cache {
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addToDialCache(host, a.String())
}
return con, err
}
return nil, errorx.DecorateMany(fmt.Sprintf("couldn't dial to %s", addr), dialErrs...)
}
}
// 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)
}
if len(c.ResolverAddress) != 0 && gctx.dialCache == nil {
dur := time.Duration(c.CacheTime) * time.Minute
gctx.dialCache = gcache.New(maxDialCacheSize).LRU().Expiration(dur).Build()
}
}
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d := new(Dnsfilter)
// Customize the Transport to have larger connection pool,
// We are not (re)using http.DefaultTransport because of race conditions found by tests
d.transport = &http.Transport{
Proxy: http.ProxyFromEnvironment,
MaxIdleConns: defaultHTTPMaxIdleConnections, // default 100
MaxIdleConnsPerHost: defaultHTTPMaxIdleConnections, // default 2
IdleConnTimeout: 90 * time.Second,
TLSHandshakeTimeout: 10 * time.Second,
ExpectContinueTimeout: 1 * time.Second,
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}
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if c != nil && len(c.ResolverAddress) != 0 {
d.transport.DialContext = d.createCustomDialContext(c.ResolverAddress)
}
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d.client = http.Client{
Transport: d.transport,
Timeout: defaultHTTPTimeout,
}
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d.safeBrowsingServer = defaultSafebrowsingServer
d.parentalServer = defaultParentalServer
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()
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if d.Config.HTTPRegister != nil { // for tests
d.registerSecurityHandlers()
d.registerRewritesHandlers()
}
return d
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}
//
// config manipulation helpers
//
// SetSafeBrowsingServer lets you optionally change hostname of safesearch lookup
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func (d *Dnsfilter) SetSafeBrowsingServer(host string) {
if len(host) == 0 {
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d.safeBrowsingServer = defaultSafebrowsingServer
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} else {
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d.safeBrowsingServer = host
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}
}
// SetHTTPTimeout lets you optionally change timeout during lookups
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func (d *Dnsfilter) SetHTTPTimeout(t time.Duration) {
d.client.Timeout = t
}
// ResetHTTPTimeout resets lookup timeouts
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func (d *Dnsfilter) ResetHTTPTimeout() {
d.client.Timeout = defaultHTTPTimeout
}
// SafeSearchDomain returns replacement address for search engine
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func (d *Dnsfilter) SafeSearchDomain(host string) (string, bool) {
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if d.SafeSearchEnabled {
val, ok := safeSearchDomains[host]
return val, ok
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}
return "", false
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}
//
// stats
//
// GetStats return dns filtering stats since startup
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func (d *Dnsfilter) GetStats() Stats {
return gctx.stats
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}