This is my new blog CMS https://jlelse.blog
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package main
import (
"crypto/rsa"
"crypto/x509"
"database/sql"
"encoding/json"
"encoding/pem"
"errors"
"fmt"
"io"
"log"
"net/http"
"net/url"
"os"
"strings"
"sync"
"time"
"github.com/go-chi/chi/v5"
"github.com/go-fed/httpsig"
)
var (
apPrivateKey *rsa.PrivateKey
apPostSigner httpsig.Signer
apPostSignMutex *sync.Mutex = &sync.Mutex{}
webfingerResources map[string]*configBlog
webfingerAccts map[string]string
)
func initActivityPub() error {
if !appConfig.ActivityPub.Enabled {
return nil
}
// Add hooks
postHooks[postPostHook] = append(postHooks[postPostHook], func(p *post) {
if p.isPublishedSectionPost() {
p.apPost()
}
})
postHooks[postUpdateHook] = append(postHooks[postUpdateHook], func(p *post) {
if p.isPublishedSectionPost() {
p.apUpdate()
}
})
postHooks[postDeleteHook] = append(postHooks[postDeleteHook], func(p *post) {
p.apDelete()
})
// Prepare webfinger
webfingerResources = map[string]*configBlog{}
webfingerAccts = map[string]string{}
for name, blog := range appConfig.Blogs {
acct := "acct:" + name + "@" + appConfig.Server.publicHostname
webfingerResources[acct] = blog
webfingerResources[blog.apIri()] = blog
webfingerAccts[blog.apIri()] = acct
}
// Read key and prepare signing
pkfile, err := os.ReadFile(appConfig.ActivityPub.KeyPath)
if err != nil {
return err
}
privateKeyDecoded, _ := pem.Decode(pkfile)
if privateKeyDecoded == nil {
return errors.New("failed to decode private key")
}
apPrivateKey, err = x509.ParsePKCS1PrivateKey(privateKeyDecoded.Bytes)
if err != nil {
return err
}
apPostSigner, _, err = httpsig.NewSigner(
[]httpsig.Algorithm{httpsig.RSA_SHA256},
httpsig.DigestSha256,
[]string{httpsig.RequestTarget, "date", "host", "digest"},
httpsig.Signature,
0,
)
if err != nil {
return err
}
// Init send queue
if err = initAPSendQueue(); err != nil {
return err
}
return nil
}
func apHandleWebfinger(w http.ResponseWriter, r *http.Request) {
blog, ok := webfingerResources[r.URL.Query().Get("resource")]
if !ok {
serveError(w, r, "Resource not found", http.StatusNotFound)
return
}
b, _ := json.Marshal(map[string]interface{}{
"subject": webfingerAccts[blog.apIri()],
"aliases": []string{
webfingerAccts[blog.apIri()],
blog.apIri(),
},
"links": []map[string]string{
{
"rel": "self",
"type": contentTypeAS,
"href": blog.apIri(),
},
{
"rel": "http://webfinger.net/rel/profile-page",
"type": "text/html",
"href": blog.apIri(),
},
},
})
w.Header().Set(contentType, "application/jrd+json"+charsetUtf8Suffix)
_, _ = writeMinified(w, contentTypeJSON, b)
}
func apHandleInbox(w http.ResponseWriter, r *http.Request) {
blogName := chi.URLParam(r, "blog")
blog := appConfig.Blogs[blogName]
if blog == nil {
serveError(w, r, "Inbox not found", http.StatusNotFound)
return
}
blogIri := blog.apIri()
// Verify request
requestActor, requestKey, requestActorStatus, err := apVerifySignature(r)
if err != nil {
// Send 401 because signature could not be verified
serveError(w, r, err.Error(), http.StatusUnauthorized)
return
}
if requestActorStatus != 0 {
if requestActorStatus == http.StatusGone || requestActorStatus == http.StatusNotFound {
u, err := url.Parse(requestKey)
if err == nil {
u.Fragment = ""
u.RawFragment = ""
_ = apRemoveFollower(blogName, u.String())
w.WriteHeader(http.StatusOK)
return
}
}
serveError(w, r, "Error when trying to get request actor", http.StatusBadRequest)
return
}
// Parse activity
activity := map[string]interface{}{}
err = json.NewDecoder(r.Body).Decode(&activity)
_ = r.Body.Close()
if err != nil {
serveError(w, r, "Failed to decode body", http.StatusBadRequest)
return
}
// Get and check activity actor
activityActor, ok := activity["actor"].(string)
if !ok {
serveError(w, r, "actor in activity is no string", http.StatusBadRequest)
return
}
if activityActor != requestActor.ID {
serveError(w, r, "Request actor isn't activity actor", http.StatusForbidden)
return
}
// Do
switch activity["type"] {
case "Follow":
apAccept(blogName, blog, activity)
case "Undo":
{
if object, ok := activity["object"].(map[string]interface{}); ok {
if objectType, ok := object["type"].(string); ok && objectType == "Follow" {
if iri, ok := object["actor"].(string); ok && iri == activityActor {
_ = apRemoveFollower(blogName, activityActor)
}
}
}
}
case "Create":
{
if object, ok := activity["object"].(map[string]interface{}); ok {
inReplyTo, hasReplyToString := object["inReplyTo"].(string)
id, hasID := object["id"].(string)
if hasReplyToString && hasID && len(inReplyTo) > 0 && len(id) > 0 && strings.Contains(inReplyTo, blogIri) {
// It's an ActivityPub reply; save reply as webmention
_ = createWebmention(id, inReplyTo)
} else if content, hasContent := object["content"].(string); hasContent && hasID && len(id) > 0 {
// May be a mention; find links to blog and save them as webmentions
if links, err := allLinksFromHTML(strings.NewReader(content), id); err == nil {
for _, link := range links {
if strings.Contains(link, blogIri) {
_ = createWebmention(id, link)
}
}
}
}
}
}
case "Delete":
case "Block":
{
if object, ok := activity["object"].(string); ok && len(object) > 0 && object == activityActor {
_ = apRemoveFollower(blogName, activityActor)
}
}
case "Like":
{
likeObject, likeObjectOk := activity["object"].(string)
if likeObjectOk && len(likeObject) > 0 && strings.Contains(likeObject, blogIri) {
sendNotification(fmt.Sprintf("%s liked %s", activityActor, likeObject))
}
}
case "Announce":
{
announceObject, announceObjectOk := activity["object"].(string)
if announceObjectOk && len(announceObject) > 0 && strings.Contains(announceObject, blogIri) {
sendNotification(fmt.Sprintf("%s announced %s", activityActor, announceObject))
}
}
}
// Return 200
w.WriteHeader(http.StatusOK)
}
func apVerifySignature(r *http.Request) (*asPerson, string, int, error) {
verifier, err := httpsig.NewVerifier(r)
if err != nil {
// Error with signature header etc.
return nil, "", 0, err
}
keyID := verifier.KeyId()
actor, statusCode, err := apGetRemoteActor(keyID)
if err != nil || actor == nil || statusCode != 0 {
// Actor not found or something else bad
return nil, keyID, statusCode, err
}
if actor.PublicKey == nil || actor.PublicKey.PublicKeyPem == "" {
return nil, keyID, 0, errors.New("Actor has no public key")
}
block, _ := pem.Decode([]byte(actor.PublicKey.PublicKeyPem))
if block == nil {
return nil, keyID, 0, errors.New("Public key invalid")
}
pubKey, err := x509.ParsePKIXPublicKey(block.Bytes)
if err != nil {
// Unable to parse public key
return nil, keyID, 0, err
}
return actor, keyID, 0, verifier.Verify(pubKey, httpsig.RSA_SHA256)
}
func handleWellKnownHostMeta(w http.ResponseWriter, r *http.Request) {
w.Header().Set(contentType, "application/xrd+xml"+charsetUtf8Suffix)
_, _ = w.Write([]byte(`<?xml version="1.0" encoding="UTF-8"?><XRD xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0"><Link rel="lrdd" type="application/xrd+xml" template="https://` + r.Host + `/.well-known/webfinger?resource={uri}"/></XRD>`))
}
func apGetRemoteActor(iri string) (*asPerson, int, error) {
req, err := http.NewRequest(http.MethodGet, iri, nil)
if err != nil {
return nil, 0, err
}
req.Header.Set("Accept", contentTypeAS)
req.Header.Set(userAgent, appUserAgent)
resp, err := appHttpClient.Do(req)
if err != nil {
return nil, 0, err
}
defer resp.Body.Close()
if !apRequestIsSuccess(resp.StatusCode) {
_, _ = io.Copy(io.Discard, resp.Body)
return nil, resp.StatusCode, nil
}
actor := &asPerson{}
err = json.NewDecoder(resp.Body).Decode(actor)
if err != nil {
_, _ = io.Copy(io.Discard, resp.Body)
return nil, 0, err
}
return actor, 0, nil
}
func apGetAllInboxes(blog string) ([]string, error) {
rows, err := appDbQuery("select distinct inbox from activitypub_followers where blog = @blog", sql.Named("blog", blog))
if err != nil {
return nil, err
}
inboxes := []string{}
for rows.Next() {
var inbox string
err = rows.Scan(&inbox)
if err != nil {
return nil, err
}
inboxes = append(inboxes, inbox)
}
return inboxes, nil
}
func apAddFollower(blog, follower, inbox string) error {
_, err := appDbExec("insert or replace into activitypub_followers (blog, follower, inbox) values (@blog, @follower, @inbox)", sql.Named("blog", blog), sql.Named("follower", follower), sql.Named("inbox", inbox))
return err
}
func apRemoveFollower(blog, follower string) error {
_, err := appDbExec("delete from activitypub_followers where blog = @blog and follower = @follower", sql.Named("blog", blog), sql.Named("follower", follower))
return err
}
func apRemoveInbox(inbox string) error {
_, err := appDbExec("delete from activitypub_followers where inbox = @inbox", sql.Named("inbox", inbox))
return err
}
func (p *post) apPost() {
n := p.toASNote()
apSendToAllFollowers(p.Blog, map[string]interface{}{
"@context": asContext,
"actor": appConfig.Blogs[p.Blog].apIri(),
"id": p.fullURL(),
"published": n.Published,
"type": "Create",
"object": n,
})
if n.InReplyTo != "" {
// Is reply, so announce it
time.Sleep(30 * time.Second)
p.apAnnounce()
}
}
func (p *post) apUpdate() {
apSendToAllFollowers(p.Blog, map[string]interface{}{
"@context": asContext,
"actor": appConfig.Blogs[p.Blog].apIri(),
"id": p.fullURL(),
"published": time.Now().Format("2006-01-02T15:04:05-07:00"),
"type": "Update",
"object": p.toASNote(),
})
}
func (p *post) apAnnounce() {
apSendToAllFollowers(p.Blog, map[string]interface{}{
"@context": asContext,
"actor": appConfig.Blogs[p.Blog].apIri(),
"id": p.fullURL() + "#announce",
"published": p.toASNote().Published,
"type": "Announce",
"object": p.fullURL(),
})
}
func (p *post) apDelete() {
apSendToAllFollowers(p.Blog, map[string]interface{}{
"@context": asContext,
"actor": appConfig.Blogs[p.Blog].apIri(),
"id": p.fullURL() + "#delete",
"type": "Delete",
"object": map[string]string{
"id": p.fullURL(),
"type": "Tombstone",
},
})
}
func apAccept(blogName string, blog *configBlog, follow map[string]interface{}) {
// it's a follow, write it down
newFollower := follow["actor"].(string)
log.Println("New follow request:", newFollower)
// check we aren't following ourselves
if newFollower == follow["object"] {
// actor and object are equal
return
}
follower, status, err := apGetRemoteActor(newFollower)
if err != nil || status != 0 {
// Couldn't retrieve remote actor info
log.Println("Failed to retrieve remote actor info:", newFollower)
return
}
// Add or update follower
inbox := follower.Inbox
if endpoints := follower.Endpoints; endpoints != nil && endpoints.SharedInbox != "" {
inbox = endpoints.SharedInbox
}
if err = apAddFollower(blogName, follower.ID, inbox); err != nil {
return
}
// remove @context from the inner activity
delete(follow, "@context")
accept := map[string]interface{}{
"@context": asContext,
"to": follow["actor"],
"actor": blog.apIri(),
"object": follow,
"type": "Accept",
}
_, accept["id"] = apNewID(blog)
_ = apQueueSendSigned(blog.apIri(), follower.Inbox, accept)
}
func apSendToAllFollowers(blog string, activity interface{}) {
inboxes, err := apGetAllInboxes(blog)
if err != nil {
log.Println("Failed to retrieve inboxes:", err.Error())
return
}
apSendTo(appConfig.Blogs[blog].apIri(), activity, inboxes)
}
func apSendTo(blogIri string, activity interface{}, inboxes []string) {
for _, i := range inboxes {
go func(inbox string) {
_ = apQueueSendSigned(blogIri, inbox, activity)
}(i)
}
}
func apNewID(blog *configBlog) (hash string, url string) {
return hash, blog.apIri() + generateRandomString(16)
}
func (b *configBlog) apIri() string {
return appConfig.Server.PublicAddress + b.Path
}
func apRequestIsSuccess(code int) bool {
return code == http.StatusOK || code == http.StatusCreated || code == http.StatusAccepted || code == http.StatusNoContent
}