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allow.go
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allow.go
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package main
import (
"context"
"encoding/json"
"expvar"
"fmt"
"io/ioutil"
"log"
"net"
"net/http"
"net/url"
"os"
"strings"
"sync"
"sync/atomic"
"time"
"cloud.google.com/go/logging"
topk "github.com/dgryski/go-topk"
"golang.org/x/exp/slog"
"golang.org/x/net/publicsuffix"
"golang.org/x/oauth2/google"
"golang.org/x/oauth2/jwt"
)
type originAllower struct {
ns *expvar.Map
hostname string
gclog logClient
ama *allowMapsAtomic
metricsMu *sync.RWMutex
topKAllDomains *topk.Stream
topKOfflistDomains *topk.Stream
errLogger *slog.Logger
}
type logClient interface {
Log(logging.Entry)
Flush() error
}
func newOriginAllower(ama *allowMapsAtomic, hostname string, gclog logClient, ns *expvar.Map, allowErrLogger *slog.Logger) *originAllower {
metricsMu := &sync.RWMutex{}
topKAllDomains := topk.New(100)
topKOfflistDomains := topk.New(100)
lifetime := new(expvar.Map).Init()
ns.Set("lifetime", lifetime)
lifetime.Set("top_all_domains", expvar.Func(func() interface{} {
metricsMu.RLock()
defer metricsMu.RUnlock()
return topKAllDomains.Keys()
}))
lifetime.Set("top_offlist_domains", expvar.Func(func() interface{} {
metricsMu.RLock()
defer metricsMu.RUnlock()
return topKOfflistDomains.Keys()
}))
oa := &originAllower{
ama: ama,
ns: ns,
hostname: hostname,
gclog: gclog,
metricsMu: metricsMu,
topKAllDomains: topKAllDomains,
topKOfflistDomains: topKOfflistDomains,
errLogger: allowErrLogger,
}
return oa
}
func (oa *originAllower) Allow(r *http.Request) (string, bool) {
origin := r.Header.Get("Origin")
referrer := r.Header.Get("Referer")
apiKey := r.FormValue("key")
userAgent := r.Header.Get("User-Agent")
remoteIP, _, err := net.SplitHostPort(r.RemoteAddr)
if err != nil {
oa.errLogger.ErrorContext(r.Context(), "error splitting RemoteAddr as host:port", "RemoteAddr", r.RemoteAddr, "err", err)
remoteIP = "0.0.0.0"
}
entry := &apiLogEntry{
DetectedDomain: "",
DetectedFullDomain: "",
Allowed: false,
APIKey: apiKey,
Headers: headers{
Origin: origin,
Referrer: referrer,
UserAgent: userAgent,
},
}
defer func() {
go oa.countRequest(entry, r, remoteIP)
}()
if origin == "" && referrer == "" {
entry.Allowed = true
return "", true
}
if origin != "" {
etldplus1, fullDomain, ok := oa.checkDomain(r.Context(), origin)
entry.DetectedDomain = etldplus1
entry.DetectedFullDomain = fullDomain
entry.Allowed = ok
if !ok {
entry.RejectionReason = rejectionConfig
}
return etldplus1, ok
}
if referrer != "" {
etldplus1, fullDomain, ok := oa.checkDomain(r.Context(), referrer)
entry.DetectedDomain = etldplus1
entry.DetectedFullDomain = fullDomain
entry.Allowed = ok
if !ok {
entry.RejectionReason = rejectionConfig
}
return etldplus1, ok
}
return "", false
}
// checkDomain checks if the detected domain from the request headers and
// whether domain is allowed to make requests against howsmyssl's API.
func (oa *originAllower) checkDomain(ctx context.Context, d string) (string, string, bool) {
d = strings.ToLower(d)
etldplus1, fullDomain, err := effectiveDomain(d)
if err != nil {
return "", "", false
}
am := oa.ama.Load()
if am.AllowTheseDomains[fullDomain] {
return etldplus1, fullDomain, true
}
if fullDomain != etldplus1 {
dom := nextDomain(fullDomain)
for {
if am.AllowSubdomainsOn[dom] {
return etldplus1, fullDomain, true
}
if dom == etldplus1 {
break
}
dom = nextDomain(dom)
if dom == "" {
oa.errLogger.ErrorContext(ctx, "when fullDomain isn't eTLD+1, got an empty string domain. Bug?", "etldplus1", etldplus1, "fullDomain", fullDomain)
break
}
}
}
dom := fullDomain
for {
if am.BlockedDomains[dom] {
return etldplus1, fullDomain, false
}
if dom == etldplus1 {
break
}
dom = nextDomain(dom)
if dom == "" {
oa.errLogger.ErrorContext(ctx, "when checking fullDomain, got an empty string domain. Bug?", "etldplus1", etldplus1, "fullDomain", fullDomain)
break
}
}
return etldplus1, fullDomain, true
}
func nextDomain(dom string) string {
i := strings.Index(dom, ".")
if i == -1 {
return ""
}
ni := i + 1
if ni == len(dom) {
return ""
}
return dom[ni:]
}
func (oa *originAllower) countRequest(entry *apiLogEntry, r *http.Request, remoteIP string) {
oa.gclog.Log(logging.Entry{
Payload: entry,
HTTPRequest: &logging.HTTPRequest{Request: r, RemoteIP: remoteIP},
Labels: map[string]string{
"server_hostname": oa.hostname,
"app": "howsmyssl",
},
})
if entry.DetectedDomain == "" {
return
}
oa.metricsMu.Lock()
defer oa.metricsMu.Unlock()
oa.topKAllDomains.Insert(entry.DetectedDomain, 1)
if !entry.Allowed {
oa.topKOfflistDomains.Insert(entry.DetectedDomain, 1)
}
}
func effectiveDomain(str string) (string, string, error) {
if str == "localhost" {
return "localhost", "localhost", nil
}
u, err := url.Parse(str)
if err != nil {
return "", "", err
}
host := u.Host
if host == "" {
return "", "", fmt.Errorf("unparsable domain string %#v", str)
}
h2, _, err := net.SplitHostPort(host)
if err == nil {
host = h2
}
ip := net.ParseIP(host)
if ip != nil {
return host, host, nil
}
if host == "localhost" {
return "localhost", "localhost", nil
}
d, err := publicsuffix.EffectiveTLDPlusOne(host)
if err != nil {
return "", "", err
}
return d, host, nil
}
func loadAllowMaps(fp string) (*allowMaps, error) {
f, err := os.Open(fp)
if err != nil {
return nil, fmt.Errorf("unable to open allowlists config file %#v: %s", fp, err)
}
defer f.Close()
al := &allowLists{}
err = json.NewDecoder(f).Decode(al)
if err != nil {
return nil, fmt.Errorf("unable to parse allowlists config file %#v: %s", fp, err)
}
am := &allowMaps{
AllowTheseDomains: make(map[string]bool, len(al.AllowTheseDomains)),
AllowSubdomainsOn: make(map[string]bool, len(al.AllowSubdomainsOn)),
BlockedDomains: make(map[string]bool, len(al.BlockedDomains)),
}
for _, dom := range al.AllowTheseDomains {
am.AllowTheseDomains[dom] = true
}
for _, dom := range al.AllowSubdomainsOn {
am.AllowSubdomainsOn[dom] = true
}
for _, dom := range al.BlockedDomains {
am.BlockedDomains[dom] = true
}
return am, nil
}
func reloadAllowMapsForever(allowListsFile string, ama *allowMapsAtomic, tick *time.Ticker) {
for range tick.C {
am, err := loadAllowMaps(allowListsFile)
if err != nil {
log.Printf("unable to reload allowlists at %#v: %s", allowListsFile, err)
}
ama.Store(am)
}
}
type allowMapsAtomic atomic.Value
func (a *allowMapsAtomic) Load() *allowMaps {
return (*atomic.Value)(a).Load().(*allowMaps)
}
func (a *allowMapsAtomic) Store(am *allowMaps) {
(*atomic.Value)(a).Store(am)
}
type rejectionReason string
const rejectionConfig = rejectionReason("config")
type apiLogEntry struct {
DetectedDomain string `json:"detected_domain"`
DetectedFullDomain string `json:"detected_full_domain"`
Allowed bool `json:"allowed"`
APIKey string `json:"api_key"`
RejectionReason rejectionReason `json:"rejection_reason"`
Headers headers `json:"headers"`
}
type headers struct {
Origin string `json:"origin"`
Referrer string `json:"referrer"`
UserAgent string `json:"user_agent"`
}
func loadGoogleServiceAccount(fp string) *googleConfig {
bs, err := ioutil.ReadFile(fp)
if err != nil {
log.Fatalf("unable to read Google service account config %#v: %s", fp, err)
}
c := &googleConfig{}
err = json.Unmarshal(bs, c)
if err != nil {
log.Fatalf("unable to parse project ID from Google service account config %#v: %s", fp, err)
}
if c.ProjectID == "" {
log.Fatalf("blank project ID in Google service account config %#v: %s", fp, err)
}
jwtConf, err := google.JWTConfigFromJSON(bs, logging.WriteScope)
if err != nil {
log.Fatalf("unable to parse Google service account config %#v: %s", fp, err)
}
c.conf = jwtConf
return c
}
type googleConfig struct {
ProjectID string `json:"project_id"`
conf *jwt.Config
}
var _ logClient = nullLogClient{}
type nullLogClient struct{}
func (n nullLogClient) Log(e logging.Entry) {
}
func (n nullLogClient) Flush() error {
return nil
}
type allowLists struct {
AllowTheseDomains []string `json:"allow_these_domains"`
AllowSubdomainsOn []string `json:"allow_subdomains_on"`
BlockedDomains []string `json:"blocked_domains"`
}
type allowMaps struct {
AllowTheseDomains map[string]bool
AllowSubdomainsOn map[string]bool
BlockedDomains map[string]bool
}