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|
// link-booster: an ActivityPub bot that boosts links sent to it via DM.
//
// Static config (domain, port, admins) lives in config.json.
// The list of actors is read from <data_dir>/actors.json at startup.
// Per-actor config (summary, allowlist/curators) lives in
// <data_dir>/actors/<name>/actor.json and is read on every request so
// changes take effect immediately without restarting the server.
//
// Usage:
//
// go run . [-config ./config.json]
package main
import (
"bytes"
"crypto/rand"
"database/sql"
"embed"
"encoding/base64"
"encoding/json"
"flag"
"fmt"
"html/template"
"image"
_ "image/gif"
"image/jpeg"
_ "image/png"
"io"
"log"
"math/big"
"net/http"
"net/url"
"os"
"path/filepath"
"regexp"
"slices"
"strings"
"sync"
"time"
"activitypub"
"golang.org/x/image/draw"
_ "golang.org/x/image/webp"
)
// ---------------------------------------------------------------------------
// Templates
// ---------------------------------------------------------------------------
//go:embed templates/*.html
var templateFS embed.FS
func mustParseTemplate(files ...string) *template.Template {
// Always include base.html so every page template has access to {{template "base" .}}
files = append([]string{"templates/base.html"}, files...)
return template.Must(template.ParseFS(templateFS, files...))
}
var (
tmplLoginForm = mustParseTemplate("templates/login_form.html")
tmplLoginPin = mustParseTemplate("templates/login_pin.html")
tmplPicker = mustParseTemplate("templates/picker.html")
tmplDashboard = mustParseTemplate("templates/dashboard.html")
)
func renderTemplate(w http.ResponseWriter, t *template.Template, data any) {
w.Header().Set("Content-Type", "text/html; charset=utf-8")
if err := t.ExecuteTemplate(w, "base", data); err != nil {
log.Printf("template render: %v", err)
}
}
// Template data structs
type loginFormData struct{}
type loginPinData struct {
BotHandle string
Handle string
PIN string
Token string
Msg string
}
type pickerData struct {
Handle string
VisibleBots []string
IsAdmin bool
}
// statusRecorder wraps http.ResponseWriter to capture the response status code.
type statusRecorder struct {
http.ResponseWriter
status int
}
func (r *statusRecorder) WriteHeader(status int) {
r.status = status
r.ResponseWriter.WriteHeader(status)
}
type outboxItem struct {
Object string
Published string
Snippet string
OpenURL string
Kind string // "boost" or "quote"
}
type curatorItem struct {
Handle string
URL string
}
type dashboardData struct {
ActorName string
BotOpenURL string
UserInstance string
Handle string
VisibleBots []string
AllActorsLink bool
Curators []curatorItem
Outbox []outboxItem
IsAdmin bool
// admin-only
DisplayName string
Summary string
Allowlist string
AvatarURL string
}
// ---------------------------------------------------------------------------
// Config
// ---------------------------------------------------------------------------
// Config is the static server configuration loaded from config.json.
// Requires a restart to change.
type Config struct {
Domain string `json:"domain"`
Port string `json:"port"`
DataDir string `json:"data_dir"`
Admins []string `json:"admins"` // actor URLs that may use the web UI
BootstrapToken string `json:"bootstrap_token"` // one-time token for first login when no actors exist
}
// ActorEntry is one entry in <data_dir>/actors.json.
// The actor's data lives at <data_dir>/actors/<name>/.
type ActorEntry struct {
Name string `json:"name"`
}
// ActorMeta is the per-actor dynamic config stored in
// <data_dir>/actors/<name>/actor.json.
// Read on every request; write via the web UI.
type ActorMeta struct {
DisplayName string `json:"display_name"`
Summary string `json:"summary"`
Allowlist []string `json:"allowlist"` // curator actor URLs; empty means admins only
AvatarID string `json:"avatar_id"` // random token, empty if no avatar
}
func loadConfig(path string) (Config, error) {
f, err := os.Open(path)
if err != nil {
return Config{}, err
}
defer f.Close()
var cfg Config
if err := json.NewDecoder(f).Decode(&cfg); err != nil {
return Config{}, err
}
if cfg.Port == "" {
cfg.Port = "8080"
}
if cfg.DataDir == "" {
cfg.DataDir = "./data"
}
return cfg, nil
}
// actorDataDir returns the data directory path (relative to dataDir) for the
// named actor. Used only to construct the DataDir string passed to
// activitypub.New, which opens its own os.Root on that path.
func actorDataDir(dataDir, name string) string {
return filepath.Join(dataDir, "actors", name)
}
// loadActors reads <data_dir>/actors.json.
// If the file does not exist, it returns an empty list.
func loadActors(dataDir string) ([]ActorEntry, error) {
data, err := os.ReadFile(filepath.Join(dataDir, "actors.json"))
if os.IsNotExist(err) {
return []ActorEntry{}, nil
}
if err != nil {
return nil, err
}
var entries []ActorEntry
if err := json.Unmarshal(data, &entries); err != nil {
return nil, err
}
return entries, nil
}
// saveActors writes <data_dir>/actors.json atomically.
func saveActors(dataDir string, entries []ActorEntry) error {
data, err := json.MarshalIndent(entries, "", " ")
if err != nil {
return err
}
tmp := filepath.Join(dataDir, "actors.json.tmp")
if err := os.WriteFile(tmp, data, 0o644); err != nil {
return err
}
return os.Rename(tmp, filepath.Join(dataDir, "actors.json"))
}
// loadActorMeta reads actors/<name>/actor.json relative to root.
// Returns an empty ActorMeta (not an error) if the file doesn't exist yet.
func loadActorMeta(root *os.Root, name string) (ActorMeta, error) {
f, err := root.Open("actors/" + name + "/actor.json")
if os.IsNotExist(err) {
return ActorMeta{}, nil
}
if err != nil {
return ActorMeta{}, err
}
defer f.Close()
data, err := io.ReadAll(f)
if err != nil {
return ActorMeta{}, err
}
// Older versions of activitypub-go cached the AP actor document in this
// very file, silently replacing our settings with it. Such a file still
// unmarshals into ActorMeta without error — "summary" exists in both
// schemas — yielding an empty allowlist that looks deliberate. Say so
// loudly instead of quietly running with lost settings.
var probe map[string]any
if err := json.Unmarshal(data, &probe); err == nil {
if _, isActorDoc := probe["publicKey"]; isActorDoc {
log.Printf("WARNING: [%s] actor.json contains an ActivityPub actor "+
"document, not this actor's settings — display name, curator "+
"allowlist and avatar have been lost and need to be re-entered "+
"in the web UI. Only admins may boost via DM until then.", name)
return ActorMeta{}, nil
}
}
var meta ActorMeta
if err := json.Unmarshal(data, &meta); err != nil {
return ActorMeta{}, err
}
return meta, nil
}
// saveActorMeta writes actors/<name>/actor.json atomically relative to root.
// dataDir is still needed for the os.Rename call since os.Root lacks Rename.
func saveActorMeta(root *os.Root, dataDir, name string, meta ActorMeta) error {
dir := actorDataDir(dataDir, name)
if err := os.MkdirAll(dir, 0o755); err != nil {
return err
}
data, err := json.MarshalIndent(meta, "", " ")
if err != nil {
return err
}
tmp := "actors/" + name + "/actor.json.tmp"
wf, err := root.OpenFile(tmp, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o644)
if err != nil {
return err
}
_, werr := wf.Write(data)
cerr := wf.Close()
if werr != nil {
return werr
}
if cerr != nil {
return cerr
}
return os.Rename(
filepath.Join(dataDir, tmp),
filepath.Join(dir, "actor.json"),
)
}
// ---------------------------------------------------------------------------
// URL extraction
// ---------------------------------------------------------------------------
// hrefRe matches href="..." attributes in anchor tags.
// Mastodon wraps URLs in <a href="..."> with the visible text split across
// <span class="invisible">, <span class="ellipsis">, etc., so we must
// extract from href rather than from the stripped text content.
var hrefRe = regexp.MustCompile(`(?i)<a\s[^>]*href="(https?://[^"]+)"`)
// mentionClassRe identifies mention links we want to skip (user @-mentions).
var mentionClassRe = regexp.MustCompile(`(?i)class="[^"]*\bu-url mention\b[^"]*"`)
// plainURLRe catches bare URLs in plain-text content (fallback).
var plainURLRe = regexp.MustCompile(`https?://[^\s<>"]+`)
// extractURLs pulls https?:// URLs out of Mastodon-flavoured HTML content.
// It prefers href attributes of non-mention anchor tags; falls back to
// scanning stripped text for any remaining bare URLs.
func extractURLs(content string) []string {
seen := map[string]bool{}
var result []string
add := func(u string) {
u = strings.TrimRight(u, ".,;:!?)")
if u != "" && !seen[u] {
seen[u] = true
result = append(result, u)
}
}
// Extract from <a href="..."> — but skip mention links
anchorRe := regexp.MustCompile(`(?i)<a\s([^>]*)>`)
for _, m := range anchorRe.FindAllStringSubmatchIndex(content, -1) {
attrs := content[m[2]:m[3]]
if mentionClassRe.MatchString(attrs) {
continue
}
if sub := hrefRe.FindStringSubmatch("<a " + attrs + ">"); len(sub) == 2 {
add(sub[1])
}
}
// Fallback: scan stripped text for bare URLs not caught above
stripped := regexp.MustCompile(`<[^>]*>`).ReplaceAllString(content, " ")
for _, u := range plainURLRe.FindAllString(stripped, -1) {
add(u)
}
return result
}
// ---------------------------------------------------------------------------
// AP object resolution
// ---------------------------------------------------------------------------
// resolveAPObjectID fetches a URL with an ActivityPub Accept header and returns
// the canonical AP object id, converting HTML post URLs to their AP id.
// fetchAPObject fetches a URL with a signed AP GET and returns the parsed
// object plus the canonical AP id. Returns nil obj if the URL is not an AP
// object. Always uses HTTP signatures so servers requiring signed GETs work.
// Set followRedirects=true when the URL may be a local alias pointing to a
// post on a different instance (e.g. from a DM mention URL).
func fetchAPObject(rawURL string, srv *activitypub.Server, policy activitypub.RedirectPolicy) (obj map[string]any, apID string, err error) {
fetched, err := srv.FetchObject(rawURL, policy)
if err != nil {
return nil, "", err
}
if id, ok := fetched["id"].(string); ok && id != "" {
return fetched, id, nil
}
return nil, "", nil
}
// ---------------------------------------------------------------------------
// Per-actor setup
// ---------------------------------------------------------------------------
func setupActor(mux *http.ServeMux, domain, dataDir string, root *os.Root, db *sql.DB, admins []string, ae ActorEntry) (*activitypub.Server, *quotingState, error) {
// Load initial meta to get summary and display name for the AP actor document.
// The allowlist is re-read live from disk on every incoming DM.
meta, err := loadActorMeta(root, ae.Name)
if err != nil {
return nil, nil, fmt.Errorf("load actor meta for %s: %w", ae.Name, err)
}
dir := actorDataDir(dataDir, ae.Name)
srv, err := activitypub.New(activitypub.Config{
Domain: domain,
ActorName: ae.Name,
ActorType: "Service",
Summary: meta.Summary,
DataDir: dir,
})
if err != nil {
return nil, nil, err
}
srv.SetDisplayName(meta.DisplayName)
qs := newQuotingState()
srv.SetHooks(activitypub.Hooks{
OnFollow: func(followerActorURL string) activitypub.FollowDecision {
log.Printf("[%s] new follower: %s", ae.Name, followerActorURL)
return activitypub.AcceptFollow
},
OnAccept: func(activity map[string]any) {
qs.handleAcceptActivity(activity)
},
OnReject: func(activity map[string]any) {
qs.handleRejectActivity(activity)
},
ServeNote: qs.serveNoteHook,
OnHTML: func(w http.ResponseWriter, r *http.Request) {
actorHTML(w, srv)
},
OnDM: func(from, content, dmNoteID, inReplyTo string) {
log.Printf("[%s] DM from %s: %s", ae.Name, from, content)
checkLoginPin(from, content)
// Helper to reply to the incoming DM. target is the URL the reply
// is about; it is remembered so that a later reply to this very
// message (e.g. "unboost") can be resolved back to it. Pass "" for
// replies that are not about a particular post.
reply := func(msg, target string) {
noteID, err := srv.SendDM(from, msg, dmNoteID)
if err != nil {
log.Printf("[%s] -> reply DM failed: %v", ae.Name, err)
return
}
recordDMThread(db, noteID, target, ae.Name, from, dmOutgoing)
}
// Re-read allowlist from disk on every DM so changes take effect
// without restarting the server.
currentMeta, err := loadActorMeta(root, ae.Name)
if err != nil {
log.Printf("[%s] -> failed to load actor meta: %v", ae.Name, err)
return
}
// Resolve any handles in the allowlist to actor URLs.
var allowlist []string
for _, entry := range currentMeta.Allowlist {
resolved, err := resolveAllowlistEntry(srv, entry)
if err != nil {
log.Printf("[%s] -> resolve allowlist entry %s: %v", ae.Name, entry, err)
allowlist = append(allowlist, entry) // keep original as fallback
} else {
allowlist = append(allowlist, resolved)
}
}
if !mayBoost(admins, allowlist, from) {
log.Printf("[%s] -> ignored: %s is neither an admin nor one of the %d curator(s)",
ae.Name, from, len(allowlist))
return
}
// "unboost" has to be tested first: "boost" is a substring of it.
unboost := hasCommand(content, "unboost")
boost := !unboost && hasCommand(content, "boost")
urls := extractURLs(content)
// A DM carrying no URL can still name a post: either by replying
// in a thread the bot already knows about, or by replying to the
// post itself. Both require an explicit command word, so that
// ordinary chatter in a thread can never (un)boost by accident.
knownTargets := false
if len(urls) == 0 {
if !boost && !unboost {
log.Printf("[%s] -> no URLs and no command in DM", ae.Name)
return
}
if inReplyTo == "" {
log.Printf("[%s] -> command without URL and not a reply, ignoring", ae.Name)
reply("Send me a URL, or reply to the post you want me to boost.", "")
return
}
if known := lookupDMThread(db, inReplyTo, ae.Name); len(known) > 0 {
// A reply inside one of our own DM conversations.
urls = known
knownTargets = true
log.Printf("[%s] -> resolved reply to %s -> %v", ae.Name, inReplyTo, urls)
} else {
// Not a conversation we know about, so the DM is a reply
// to a post somewhere: that post is what is meant.
urls = []string{inReplyTo}
log.Printf("[%s] -> targeting the post replied to: %s", ae.Name, inReplyTo)
}
}
for _, u := range urls {
original := u
var apObj map[string]any
// URLs from the thread index are already canonical AP ids, and
// unboosting only has to match our own outbox entry — skip the
// fetch so it still works once the post is unreachable.
if !knownTargets {
if obj, apID, err := fetchAPObject(u, srv, activitypub.FollowRedirects); err != nil {
log.Printf("[%s] -> fetch AP object for %s failed: %v, using as-is", ae.Name, u, err)
} else if apID != "" {
if apID != u {
log.Printf("[%s] -> resolved %s -> %s", ae.Name, u, apID)
u = apID
}
apObj = obj
}
}
// Remember what this DM was about, so a later reply to it
// resolves back to the post even when it carries no URL.
recordDMThread(db, dmNoteID, u, ae.Name, from, dmIncoming)
if unboost {
log.Printf("[%s] -> unboosting %s", ae.Name, u)
if err := DeleteQuote(srv, u); err != nil {
log.Printf("[%s] -> delete quote failed: %v", ae.Name, err)
}
if err := srv.UndoAnnounce(u); err != nil {
log.Printf("[%s] -> undo announce failed: %v", ae.Name, err)
}
if original != u {
_ = DeleteQuote(srv, original)
_ = srv.UndoAnnounce(original)
}
reply(fmt.Sprintf("Unboosted %s", dmLink(u)), u)
} else if apObj != nil {
// Always try to quote-post AP objects — sends a QuoteRequest
// and waits up to 5s for approval. Falls back to Announce on
// timeout (e.g. followers-only policy and bot isn't a follower).
authorURL, _ := apObj["attributedTo"].(string)
log.Printf("[%s] -> quote-posting %s (author: %s, quote policy: %s)", ae.Name, u, authorURL, quotePolicy(apObj))
approved, err := QuotePost(srv, qs, u, authorURL)
if err != nil {
log.Printf("[%s] -> quote-post failed: %v, falling back to announce", ae.Name, err)
} else if !approved && quoteRequiresFollow(apObj, authorURL) {
log.Printf("[%s] -> quote requires follow, trying FollowAndQuote for %s", ae.Name, u)
approved, err = FollowAndQuote(srv, qs, u, authorURL)
if err != nil {
log.Printf("[%s] -> follow-and-quote failed: %v, falling back to announce", ae.Name, err)
}
}
if err != nil || !approved {
if err == nil {
log.Printf("[%s] -> quote-post timed out/rejected, falling back to announce", ae.Name)
}
if err := srv.AnnounceWithOriginal(u, original); err != nil {
log.Printf("[%s] -> announce fallback failed: %v", ae.Name, err)
reply(fmt.Sprintf("Boosted %s (could not quote: timed out)", dmLink(u)), u)
} else {
reply(fmt.Sprintf("Boosted %s (could not quote: timed out)", dmLink(u)), u)
}
} else {
reply(fmt.Sprintf("Quoted %s", dmLink(u)), u)
}
} else {
log.Printf("[%s] -> boosting %s (not an AP object)", ae.Name, u)
if err := srv.AnnounceWithOriginal(u, original); err != nil {
log.Printf("[%s] -> boost failed: %v", ae.Name, err)
reply(fmt.Sprintf("Failed to boost %s: %v", dmLink(u), err), u)
} else {
if snippet := fetchContentSnippet(srv, u); snippet != "" {
srv.SetAnnounceField(u, "contentSnippet", snippet)
}
reply(fmt.Sprintf("Boosted %s", dmLink(u)), u)
}
}
}
},
})
srv.RegisterActor(mux)
// Build and push the summary with the curated-by list in the background
// so startup isn't blocked by remote actor fetches.
go func() {
summary := buildSummaryWithCurators(srv, meta.Summary, meta.Allowlist)
srv.SetSummary(summary)
if err := srv.UpdateProfile(false); err != nil {
log.Printf("[%s] update profile with curators: %v", ae.Name, err)
}
}()
log.Printf("actor @%s@%s ready (data: %s, allowlist: %d)", ae.Name, domain, dir, len(meta.Allowlist))
return srv, qs, nil
}
// resolveAllowlistEntry resolves an allowlist entry to an actor URL.
// Entries may be actor URLs (https://...) or fediverse handles (@user@host or user@host).
func resolveAllowlistEntry(srv *activitypub.Server, entry string) (string, error) {
if strings.HasPrefix(entry, "https://") || strings.HasPrefix(entry, "http://") {
return entry, nil
}
return srv.ResolveHandle(entry)
}
// buildSummaryWithCurators appends a "Curated by" section to base, fetching
// each curator's preferredUsername and profile URL for the link text.
func buildSummaryWithCurators(srv *activitypub.Server, base string, allowlist []string) string {
if len(allowlist) == 0 {
return base
}
var links []string
for _, entry := range allowlist {
actorURL, err := resolveAllowlistEntry(srv, entry)
if err != nil {
log.Printf("buildSummaryWithCurators: resolve %s: %v", entry, err)
continue
}
obj, err := srv.FetchObject(actorURL, activitypub.NoRedirects)
if err != nil {
log.Printf("buildSummaryWithCurators: fetch %s: %v", actorURL, err)
// Fall back to just the actor URL as a link.
links = append(links, fmt.Sprintf(`<a href="%s">%s</a>`,
template.HTMLEscapeString(actorURL),
template.HTMLEscapeString(actorURL)))
continue
}
username, _ := obj["preferredUsername"].(string)
profileURL, _ := obj["url"].(string)
if profileURL == "" {
profileURL = actorURL
}
if username == "" {
username = actorURL
}
// Extract host for @user@host display.
handle := username
if u, err := url.Parse(actorURL); err == nil {
handle = "@" + username + "@" + u.Host
}
links = append(links, fmt.Sprintf(`<a href="%s" rel="nofollow noopener noreferrer">%s</a>`,
template.HTMLEscapeString(profileURL),
template.HTMLEscapeString(handle)))
}
if len(links) == 0 {
return base
}
curated := "<p>Curated by " + strings.Join(links, ", ") + "</p>"
if base == "" {
return curated
}
return base + "\n" + curated
}
// ---------------------------------------------------------------------------
// Fediverse PIN login
// ---------------------------------------------------------------------------
type loginSession struct {
actorURL string // resolved AP actor URL of the user
handle string // original handle as typed, for display
pin string // 4-digit string "0000"–"9999"
createdAt time.Time
verified bool
}
var (
loginMu sync.Mutex
loginSessions = map[string]*loginSession{}
sessionsPath string // set once in main() to <dataDir>/sessions.json
)
// newToken returns a cryptographically random base64url-encoded 128-bit token.
func newToken() string {
var b [16]byte
if _, err := rand.Read(b[:]); err != nil {
panic("crypto/rand unavailable: " + err.Error())
}
return base64.RawURLEncoding.EncodeToString(b[:])
}
// newPIN returns a zero-padded random 4-digit string "0000"–"9999".
func newPIN() string {
n, err := rand.Int(rand.Reader, big.NewInt(10000))
if err != nil {
panic("crypto/rand unavailable: " + err.Error())
}
return fmt.Sprintf("%04d", n.Int64())
}
// pinRe matches the first standalone 4-digit sequence in stripped text.
var pinRe = regexp.MustCompile(`\b(\d{4})\b`)
// stripTags removes HTML tags from s.
func stripTags(s string) string {
return regexp.MustCompile(`<[^>]*>`).ReplaceAllString(s, " ")
}
// checkLoginPin is called for every incoming DM. If the content contains a
// 4-digit PIN that matches a pending session for actorURL, it marks it verified.
func checkLoginPin(actorURL, content string) {
stripped := stripTags(content)
m := pinRe.FindStringSubmatch(stripped)
if m == nil {
return
}
pin := m[1]
loginMu.Lock()
defer loginMu.Unlock()
for _, sess := range loginSessions {
if !sess.verified && sess.actorURL == actorURL && sess.pin == pin {
sess.verified = true
log.Printf("login: PIN verified for %s (%s)", sess.handle, actorURL)
saveSessions()
return
}
}
}
// gcLoginSession deletes the session after 10 minutes if still unverified.
func gcLoginSession(token string) {
time.Sleep(10 * time.Minute)
loginMu.Lock()
defer loginMu.Unlock()
sess, ok := loginSessions[token]
if ok && !sess.verified {
delete(loginSessions, token)
log.Printf("login: session for %s expired", sess.handle)
}
}
// sessionRecord is the on-disk representation of a verified session.
// Only verified sessions are persisted; pending ones are transient.
type sessionRecord struct {
Token string `json:"token"`
Handle string `json:"handle"`
ActorURL string `json:"actor_url"`
CreatedAt time.Time `json:"created_at"`
}
// loadSessions reads verified sessions from disk into loginSessions.
// Called once at startup; non-fatal if the file is missing.
func loadSessions() {
if sessionsPath == "" {
return
}
data, err := os.ReadFile(sessionsPath)
if err != nil {
if !os.IsNotExist(err) {
log.Printf("login: load sessions: %v", err)
}
return
}
var records []sessionRecord
if err := json.Unmarshal(data, &records); err != nil {
log.Printf("login: parse sessions.json: %v", err)
return
}
loginMu.Lock()
defer loginMu.Unlock()
for _, rec := range records {
loginSessions[rec.Token] = &loginSession{
actorURL: rec.ActorURL,
handle: rec.Handle,
pin: "", // not needed after verification
createdAt: rec.CreatedAt,
verified: true,
}
}
log.Printf("login: loaded %d verified session(s) from disk", len(records))
}
// saveSessions writes all verified sessions to disk atomically.
// Must be called with loginMu held.
func saveSessions() {
if sessionsPath == "" {
return
}
var records []sessionRecord
for token, sess := range loginSessions {
if sess.verified {
records = append(records, sessionRecord{
Token: token,
Handle: sess.handle,
ActorURL: sess.actorURL,
CreatedAt: sess.createdAt,
})
}
}
data, err := json.MarshalIndent(records, "", " ")
if err != nil {
log.Printf("login: marshal sessions: %v", err)
return
}
tmp := sessionsPath + ".tmp"
if err := os.WriteFile(tmp, data, 0o600); err != nil {
log.Printf("login: write sessions.tmp: %v", err)
return
}
if err := os.Rename(tmp, sessionsPath); err != nil {
log.Printf("login: rename sessions: %v", err)
}
}
// makeLoginHandler returns a /login handler.
// apSrv is used for WebFinger resolution.
// admins and allServers are used to check that the resolved actor is either
// an admin or a curator of at least one actor.
func makeLoginHandler(apSrv *activitypub.Server, firstActorName string, dataDir string, root *os.Root, admins []string, registry *actorRegistry) http.HandlerFunc {
// Pick any bot handle for the PIN instruction — use the first actor.
botHandle := fmt.Sprintf("@%s@%s", firstActorName, apSrv.Domain())
return func(w http.ResponseWriter, r *http.Request) {
switch r.Method {
case http.MethodGet:
handle := strings.TrimSpace(r.URL.Query().Get("user"))
if handle == "" {
renderTemplate(w, tmplLoginForm, loginFormData{})
return
}
actorURL, err := apSrv.ResolveHandle(handle)
if err != nil {
log.Printf("login: resolve handle %q: %v", handle, err)
http.Error(w,
fmt.Sprintf("Could not resolve fediverse handle %q: %v", handle, err),
http.StatusBadRequest)
return
}
log.Printf("login: resolved %q -> %s", handle, actorURL)
// Allow admins and any curator of at least one actor.
permitted := inAllowlist(admins, actorURL)
if !permitted {
for _, name := range registry.names() {
meta, err := loadActorMeta(root, name)
if err == nil && inAllowlist(meta.Allowlist, actorURL) {
permitted = true
break
}
}
}
if !permitted {
log.Printf("login: rejected %s (not an admin or curator)", actorURL)
http.Error(w, "This handle is not permitted to log in.", http.StatusForbidden)
return
}
token := newToken()
pin := newPIN()
loginMu.Lock()
loginSessions[token] = &loginSession{
actorURL: actorURL,
handle: handle,
pin: pin,
createdAt: time.Now(),
}
loginMu.Unlock()
go gcLoginSession(token)
renderTemplate(w, tmplLoginPin, loginPinData{
BotHandle: botHandle,
Handle: handle,
PIN: pin,
Token: token,
})
case http.MethodPost:
if err := r.ParseForm(); err != nil {
http.Error(w, "bad form data", http.StatusBadRequest)
return
}
token := r.FormValue("session_id")
if token == "" {
http.Error(w, "missing session_id", http.StatusBadRequest)
return
}
loginMu.Lock()
sess, ok := loginSessions[token]
loginMu.Unlock()
if !ok {
http.Error(w,
"Session expired or not found. Please start again: /login?user=@you@instance",
http.StatusUnauthorized)
return
}
if !sess.verified {
renderTemplate(w, tmplLoginPin, loginPinData{
BotHandle: botHandle,
Handle: sess.handle,
PIN: sess.pin,
Token: token,
Msg: "PIN not confirmed yet — check you sent the right code, then try again.",
})
return
}
// Verified — issue session cookie and redirect to /backend
http.SetCookie(w, &http.Cookie{
Name: "session",
Value: token,
Path: "/",
MaxAge: 365 * 24 * 60 * 60, // 1 year
HttpOnly: true,
Secure: true,
SameSite: http.SameSiteLaxMode,
})
http.Redirect(w, r, "/backend", http.StatusSeeOther)
default:
http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
}
}
}
// sessionFromRequest looks up the session cookie and returns the verified
// session, or redirects to /login and returns nil.
func sessionFromRequest(w http.ResponseWriter, r *http.Request) *loginSession {
cookie, err := r.Cookie("session")
if err != nil {
http.Redirect(w, r, "/login", http.StatusSeeOther)
return nil
}
loginMu.Lock()
sess, ok := loginSessions[cookie.Value]
loginMu.Unlock()
if !ok || !sess.verified {
http.Redirect(w, r, "/login", http.StatusSeeOther)
return nil
}
return sess
}
// makeBackendHandler returns the /backend handler.
// allServers maps actor name -> *activitypub.Server.
// dataDir is the top-level data directory (used to read/write actor.json).
// admins is used to verify the session is still authorised.
func makeBackendHandler(dataDir string, root *os.Root, admins []string, registry *actorRegistry) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
sess := sessionFromRequest(w, r)
if sess == nil {
return
}
switch r.Method {
case http.MethodGet:
backendGET(w, r, dataDir, root, admins, registry, sess)
case http.MethodPost:
if err := r.ParseForm(); err != nil {
http.Error(w, "bad form data", http.StatusBadRequest)
return
}
backendPOST(w, r, dataDir, root, admins, registry, sess)
default:
http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
}
}
}
func backendGET(w http.ResponseWriter, r *http.Request, dataDir string, root *os.Root, admins []string, registry *actorRegistry, sess *loginSession) {
isAdmin := inAllowlist(admins, sess.actorURL)
// Collect actor names this session is allowed to see:
// admins see all; curators see only actors whose allowlist includes them.
var visibleNames []string
for _, name := range registry.names() {
if isAdmin {
visibleNames = append(visibleNames, name)
} else {
meta, err := loadActorMeta(root, name)
if err == nil && inAllowlist(meta.Allowlist, sess.actorURL) {
visibleNames = append(visibleNames, name)
}
}
}
if len(visibleNames) == 0 && !isAdmin {
http.Error(w, "You are not a curator of any bot.", http.StatusForbidden)
return
}
actorName := r.URL.Query().Get("actor")
// No actor selected — admins always see the picker (so they can create actors);
// non-admin curators with only one actor get redirected directly.
if actorName == "" {
if len(visibleNames) == 1 && !isAdmin {
http.Redirect(w, r, "/backend?actor="+visibleNames[0], http.StatusSeeOther)
return
}
renderTemplate(w, tmplPicker, pickerData{
Handle: sess.handle,
VisibleBots: visibleNames,
IsAdmin: isAdmin,
})
return
}
// Specific actor selected — check the session can see it
srv, ok := registry.get(actorName)
if !ok {
http.Error(w, "Unknown actor.", http.StatusNotFound)
return
}
if !isAdmin {
meta0, err := loadActorMeta(root, actorName)
if err != nil || !inAllowlist(meta0.Allowlist, sess.actorURL) {
http.Error(w, "You are not a curator of this bot.", http.StatusForbidden)
return
}
}
// Load live actor meta (summary + allowlist)
meta, err := loadActorMeta(root, actorName)
if err != nil {
http.Error(w, fmt.Sprintf("load actor meta: %v", err), http.StatusInternalServerError)
return
}
userInstance := instanceHost(sess.actorURL)
// Build outbox items
outboxItems := buildOutboxItems(srv.Outbox(), userInstance)
// Build curator items
var curators []curatorItem
for _, cu := range meta.Allowlist {
href := cu
if userInstance != "" {
href = fmt.Sprintf("https://%s/authorize_interaction?uri=%s",
userInstance, url.QueryEscape(cu))
}
curators = append(curators, curatorItem{Handle: actorHandle(cu), URL: href})
}
// Bot open URL
botOpenURL := ""
if userInstance != "" {
botOpenURL = fmt.Sprintf("https://%s/authorize_interaction?uri=%s",
userInstance, url.QueryEscape(srv.ActorURL()))
}
// Avatar URL (admin only, but safe to compute always)
avatarURL := ""
if meta.AvatarID != "" {
avatarURL = avatarPublicURL(srv.Domain(), actorName, meta.AvatarID)
}
renderTemplate(w, tmplDashboard, dashboardData{
ActorName: actorName,
BotOpenURL: botOpenURL,
UserInstance: userInstance,
Handle: sess.handle,
VisibleBots: visibleNames,
AllActorsLink: len(visibleNames) > 1 || isAdmin,
Curators: curators,
Outbox: outboxItems,
IsAdmin: isAdmin,
DisplayName: meta.DisplayName,
Summary: meta.Summary,
Allowlist: strings.Join(meta.Allowlist, "\n"),
AvatarURL: avatarURL,
})
}
func backendPOST(w http.ResponseWriter, r *http.Request, dataDir string, root *os.Root, admins []string, registry *actorRegistry, sess *loginSession) {
isAdmin := inAllowlist(admins, sess.actorURL)
actorName := r.URL.Query().Get("actor")
if actorName == "" {
actorName = r.FormValue("actor")
}
if actorName == "" {
http.Error(w, "missing actor parameter", http.StatusBadRequest)
return
}
entry, ok := registry.getEntry(actorName)
if !ok {
http.Error(w, "Unknown actor.", http.StatusNotFound)
return
}
srv := entry.srv
qs := entry.qs
action := r.FormValue("action")
// save_meta is admin-only
if action == "save_meta" {
if !isAdmin {
http.Error(w, "Only admins can edit actor settings.", http.StatusForbidden)
return
}
displayName := strings.TrimSpace(r.FormValue("display_name"))
summary := strings.TrimSpace(r.FormValue("summary"))
var allowlist []string
for line := range strings.SplitSeq(r.FormValue("allowlist"), "\n") {
if u := strings.TrimSpace(line); u != "" {
allowlist = append(allowlist, u)
}
}
// Load-then-modify so fields not present in this form (currently
// AvatarID, which is written by the avatar upload handler) survive
// the save instead of being reset to their zero value.
meta, err := loadActorMeta(root, actorName)
if err != nil {
http.Error(w, fmt.Sprintf("load actor meta: %v", err), http.StatusInternalServerError)
return
}
meta.DisplayName = displayName
meta.Summary = summary
meta.Allowlist = allowlist
if err := saveActorMeta(root, dataDir, actorName, meta); err != nil {
http.Error(w, fmt.Sprintf("save failed: %v", err), http.StatusInternalServerError)
return
}
// Update in-memory fields and push Update{Actor} to followers.
// The curated-by list is appended here exactly as it is at startup,
// otherwise saving settings would strip it from the public profile
// until the next restart. It is derived from the allowlist rather
// than stored, so meta.Summary stays the plain text the user typed.
srv.SetDisplayName(displayName)
go func() {
srv.SetSummary(buildSummaryWithCurators(srv, summary, allowlist))
if err := srv.UpdateProfile(true); err != nil {
log.Printf("backend: UpdateProfile for %s: %v", actorName, err)
}
}()
http.Redirect(w, r, "/backend?actor="+actorName, http.StatusSeeOther)
return
}
// boost/unboost: allowed for admins and curators of this actor
if !isAdmin {
meta, err := loadActorMeta(root, actorName)
if err != nil || !inAllowlist(meta.Allowlist, sess.actorURL) {
http.Error(w, "You are not a curator of this bot.", http.StatusForbidden)
return
}
}
rawURL := strings.TrimSpace(r.FormValue("url"))
if rawURL == "" {
http.Error(w, "missing url", http.StatusBadRequest)
return
}
switch action {
case "boost":
original := rawURL
var apObj map[string]any
if obj, apID, err := fetchAPObject(rawURL, srv, activitypub.FollowRedirects); err != nil {
log.Printf("backend: fetch AP object for %s: %v, using as-is", rawURL, err)
} else if apID != "" {
if apID != rawURL {
log.Printf("backend: resolved %s -> %s", rawURL, apID)
rawURL = apID
}
apObj = obj
}
if apObj != nil {
authorURL, _ := apObj["attributedTo"].(string)
log.Printf("backend: quote-posting %s (author: %s, quote policy: %s)", rawURL, authorURL, quotePolicy(apObj))
approved, err := QuotePost(srv, qs, rawURL, authorURL)
if err != nil {
log.Printf("backend: quote-post failed: %v, falling back to announce", err)
} else if !approved && quoteRequiresFollow(apObj, authorURL) {
log.Printf("backend: quote requires follow, trying FollowAndQuote for %s", rawURL)
approved, err = FollowAndQuote(srv, qs, rawURL, authorURL)
if err != nil {
log.Printf("backend: follow-and-quote failed: %v, falling back to announce", err)
}
}
if err != nil || !approved {
if err == nil {
log.Printf("backend: quote-post timed out/rejected, falling back to announce")
}
if err := srv.AnnounceWithOriginal(rawURL, original); err != nil {
log.Printf("backend: boost fallback %s: %v", rawURL, err)
http.Error(w, fmt.Sprintf("boost failed: %v", err), http.StatusInternalServerError)
return
}
}
} else {
log.Printf("backend: boosting %s (no public quote policy)", rawURL)
if err := srv.AnnounceWithOriginal(rawURL, original); err != nil {
log.Printf("backend: boost %s: %v", rawURL, err)
http.Error(w, fmt.Sprintf("boost failed: %v", err), http.StatusInternalServerError)
return
} else if snippet := fetchContentSnippet(srv, rawURL); snippet != "" {
srv.SetAnnounceField(rawURL, "contentSnippet", snippet)
}
}
case "unboost":
if err := DeleteQuote(srv, rawURL); err != nil {
log.Printf("backend: delete quote %s: %v", rawURL, err)
}
if err := srv.UndoAnnounce(rawURL); err != nil {
log.Printf("backend: unboost %s: %v", rawURL, err)
http.Error(w, fmt.Sprintf("unboost failed: %v", err), http.StatusInternalServerError)
return
}
default:
http.Error(w, "unknown action", http.StatusBadRequest)
return
}
http.Redirect(w, r, "/backend?actor="+actorName, http.StatusSeeOther)
}
// ---------------------------------------------------------------------------
// Actor registry (thread-safe, mutable at runtime)
// ---------------------------------------------------------------------------
type actorEntry struct {
srv *activitypub.Server
qs *quotingState
}
type actorRegistry struct {
mu sync.RWMutex
entries map[string]actorEntry
}
func newActorRegistry() *actorRegistry {
return &actorRegistry{entries: make(map[string]actorEntry)}
}
func (ar *actorRegistry) get(name string) (*activitypub.Server, bool) {
ar.mu.RLock()
e, ok := ar.entries[name]
ar.mu.RUnlock()
return e.srv, ok
}
func (ar *actorRegistry) getEntry(name string) (actorEntry, bool) {
ar.mu.RLock()
e, ok := ar.entries[name]
ar.mu.RUnlock()
return e, ok
}
func (ar *actorRegistry) set(name string, srv *activitypub.Server) {
ar.mu.Lock()
e := ar.entries[name]
e.srv = srv
ar.entries[name] = e
ar.mu.Unlock()
}
func (ar *actorRegistry) setEntry(name string, srv *activitypub.Server, qs *quotingState) {
ar.mu.Lock()
ar.entries[name] = actorEntry{srv: srv, qs: qs}
ar.mu.Unlock()
}
func (ar *actorRegistry) names() []string {
ar.mu.RLock()
names := make([]string, 0, len(ar.entries))
for n := range ar.entries {
names = append(names, n)
}
ar.mu.RUnlock()
return names
}
func (ar *actorRegistry) snapshot() map[string]*activitypub.Server {
ar.mu.RLock()
m := make(map[string]*activitypub.Server, len(ar.entries))
for k, e := range ar.entries {
m[k] = e.srv
}
ar.mu.RUnlock()
return m
}
// ---------------------------------------------------------------------------
// Main
// ---------------------------------------------------------------------------
func main() {
configPath := flag.String("config", "./config.json", "Path to config.json")
flag.Parse()
cfg, err := loadConfig(*configPath)
if err != nil {
log.Fatalf("load config: %v", err)
}
actors, err := loadActors(cfg.DataDir)
if err != nil {
log.Fatalf("load actors from %s/actors.json: %v", cfg.DataDir, err)
}
// Open a traversal-resistant root on the data directory.
// All file operations under cfg.DataDir use this root.
if err := os.MkdirAll(cfg.DataDir, 0o755); err != nil {
log.Fatalf("create data dir: %v", err)
}
dataRoot, err := os.OpenRoot(cfg.DataDir)
if err != nil {
log.Fatalf("open data dir root: %v", err)
}
db, err := openDB(cfg.DataDir)
if err != nil {
log.Fatalf("open database: %v", err)
}
defer db.Close()
mux := http.NewServeMux()
registry := newActorRegistry()
// The "auth" actor always exists — it's used for login PIN delivery via DM.
// This allows admins to log in even when no Service actors are configured yet.
authSrv, err := activitypub.New(activitypub.Config{
Domain: cfg.Domain,
ActorName: "auth",
ActorType: "Service",
Summary: "Authentication actor — DM me your PIN to log in.",
DataDir: filepath.Join(cfg.DataDir, "auth"),
})
if err != nil {
log.Fatalf("setup auth actor: %v", err)
}
authSrv.SetDisplayName("Auth")
authSrv.SetHooks(activitypub.Hooks{
OnDM: func(from, content, noteID, inReplyTo string) {
log.Printf("[auth] DM from %s: %s", from, content)
checkLoginPin(from, content)
},
})
authSrv.RegisterActor(mux)
for _, ae := range actors {
srv, qs, err := setupActor(mux, cfg.Domain, cfg.DataDir, dataRoot, db, cfg.Admins, ae)
if err != nil {
log.Fatalf("setup actor %s: %v", ae.Name, err)
}
registry.setEntry(ae.Name, srv, qs)
}
// Domain-wide routes (WebFinger + shared inbox) registered once.
// The auth server handles domain routes — it always exists.
authSrv.RegisterDomain(mux)
// Restore avatar URLs for actors that already have a saved avatar.
for _, ae := range actors {
meta, err := loadActorMeta(dataRoot, ae.Name)
if err == nil && meta.AvatarID != "" {
if srv, ok := registry.get(ae.Name); ok {
srv.SetIcon(avatarPublicURL(cfg.Domain, ae.Name, meta.AvatarID))
}
}
}
sessionsPath = cfg.DataDir + "/sessions.json"
loadSessions()
mux.HandleFunc("/login", makeLoginHandler(authSrv, "auth", cfg.DataDir, dataRoot, cfg.Admins, registry))
mux.HandleFunc("/backend", makeBackendHandler(cfg.DataDir, dataRoot, cfg.Admins, registry))
mux.HandleFunc("/backend/new-actor", makeNewActorHandler(cfg.DataDir, cfg.Domain, dataRoot, db, cfg.Admins, registry, mux))
mux.HandleFunc("/avatars/", makeAvatarHandler(cfg.DataDir, dataRoot))
mux.HandleFunc("/backend/avatar", makeAvatarUploadHandler(cfg.DataDir, cfg.Domain, dataRoot, cfg.Admins, registry))
log.Printf("link-booster starting on :%s (domain: %s, actors: %d, admins: %d)",
cfg.Port, cfg.Domain, len(actors), len(cfg.Admins))
handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
rw := &statusRecorder{ResponseWriter: w, status: http.StatusOK}
mux.ServeHTTP(rw, r)
if rw.status == http.StatusNotFound &&
(strings.HasPrefix(r.URL.Path, "/users/") ||
strings.HasPrefix(r.URL.Path, "/.well-known/")) {
log.Printf("404 %s %s (from %s)", r.Method, r.URL.Path, r.RemoteAddr)
}
})
if err := http.ListenAndServe(":"+cfg.Port, handler); err != nil {
log.Fatalf("ListenAndServe: %v", err)
}
}
// ---------------------------------------------------------------------------
// Avatar helpers
// ---------------------------------------------------------------------------
const avatarSize = 400
// resizeToJPEG decodes an image from src, center-crops it to a square, scales
// it to avatarSize×avatarSize using CatmullRom resampling, and encodes the
// result as JPEG quality 90.
func resizeToJPEG(src []byte) ([]byte, error) {
img, _, err := image.Decode(bytes.NewReader(src))
if err != nil {
return nil, fmt.Errorf("decode image: %w", err)
}
// Center-crop to square.
b := img.Bounds()
w, h := b.Dx(), b.Dy()
var cropRect image.Rectangle
if w > h {
// Wider than tall: trim left and right.
x0 := b.Min.X + (w-h)/2
cropRect = image.Rect(x0, b.Min.Y, x0+h, b.Max.Y)
} else {
// Taller than wide (or already square): trim top and bottom.
y0 := b.Min.Y + (h-w)/2
cropRect = image.Rect(b.Min.X, y0, b.Max.X, y0+w)
}
dst := image.NewRGBA(image.Rect(0, 0, avatarSize, avatarSize))
draw.CatmullRom.Scale(dst, dst.Bounds(), img, cropRect, draw.Over, nil)
var buf bytes.Buffer
if err := jpeg.Encode(&buf, dst, &jpeg.Options{Quality: 90}); err != nil {
return nil, fmt.Errorf("encode jpeg: %w", err)
}
return buf.Bytes(), nil
}
// avatarRootPath returns the path of the avatar JPEG relative to the data root.
// id is the random token stored in actor.json.
func avatarRootPath(actorName, id string) string {
return "actors/" + actorName + "/avatar-" + id + ".jpg"
}
// avatarPath returns the full filesystem path where the avatar JPEG is stored.
// Used only for os.Rename (os.Root does not yet support Rename).
func avatarPath(dataDir, actorName, id string) string {
return actorDataDir(dataDir, actorName) + "/avatar-" + id + ".jpg"
}
// avatarPublicURL returns the public URL at which the avatar is served.
func avatarPublicURL(domain, actorName, id string) string {
return "https://" + domain + "/avatars/" + actorName + "-" + id + ".jpg"
}
// makeAvatarHandler serves actor avatar images from disk.
// Route: GET /avatars/{name}-{id}.jpg
func makeAvatarHandler(dataDir string, root *os.Root) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
if r.Method != http.MethodGet {
http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
return
}
// filename is "<name>-<id>.jpg"; strip prefix and suffix then read directly.
filename := strings.TrimPrefix(r.URL.Path, "/avatars/")
if filename == "" || strings.ContainsAny(filename, "/\\") || !strings.HasSuffix(filename, ".jpg") {
http.Error(w, "not found", http.StatusNotFound)
return
}
// Extract actor name: everything before the last "-"
base := strings.TrimSuffix(filename, ".jpg")
dash := strings.LastIndex(base, "-")
if dash < 0 {
http.Error(w, "not found", http.StatusNotFound)
return
}
actorName := base[:dash]
id := base[dash+1:]
if actorName == "" || id == "" {
http.Error(w, "not found", http.StatusNotFound)
return
}
f, err := root.Open(avatarRootPath(actorName, id))
if err != nil {
http.Error(w, "not found", http.StatusNotFound)
return
}
defer f.Close()
data, err := io.ReadAll(f)
if err != nil {
http.Error(w, "not found", http.StatusNotFound)
return
}
w.Header().Set("Content-Type", "image/jpeg")
// Immutable: the URL changes on every upload so we can cache forever.
w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
w.Write(data)
}
}
// makeAvatarUploadHandler returns a POST handler for /backend/avatar?actor=...
// Accepts multipart/form-data with a field named "avatar".
func makeAvatarUploadHandler(dataDir, domain string, root *os.Root, admins []string, registry *actorRegistry) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
if r.Method != http.MethodPost {
http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
return
}
sess := sessionFromRequest(w, r)
if sess == nil {
return
}
if !inAllowlist(admins, sess.actorURL) {
http.Error(w, "Only admins can upload avatars.", http.StatusForbidden)
return
}
actorName := r.URL.Query().Get("actor")
if actorName == "" {
http.Error(w, "missing actor parameter", http.StatusBadRequest)
return
}
srv, ok := registry.get(actorName)
if !ok {
http.Error(w, "unknown actor", http.StatusNotFound)
return
}
// 8 MiB max upload
if err := r.ParseMultipartForm(8 << 20); err != nil {
http.Error(w, "bad multipart form", http.StatusBadRequest)
return
}
file, _, err := r.FormFile("avatar")
if err != nil {
http.Error(w, "missing avatar file", http.StatusBadRequest)
return
}
defer file.Close()
var raw bytes.Buffer
if _, err := raw.ReadFrom(file); err != nil {
http.Error(w, "read error", http.StatusInternalServerError)
return
}
resized, err := resizeToJPEG(raw.Bytes())
if err != nil {
http.Error(w, fmt.Sprintf("image processing failed: %v", err), http.StatusBadRequest)
return
}
// Generate a new random ID so the URL changes and caches are busted.
newID := newToken()
// Load current meta to get old avatar ID (for cleanup) and preserve other fields.
meta, err := loadActorMeta(root, actorName)
if err != nil {
http.Error(w, fmt.Sprintf("load actor meta: %v", err), http.StatusInternalServerError)
return
}
oldID := meta.AvatarID
wf, err := root.OpenFile(avatarRootPath(actorName, newID), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o644)
if err != nil {
http.Error(w, "save failed", http.StatusInternalServerError)
return
}
_, werr := wf.Write(resized)
cerr := wf.Close()
if werr != nil || cerr != nil {
http.Error(w, "save failed", http.StatusInternalServerError)
return
}
// Persist new ID into actor.json.
meta.AvatarID = newID
if err := saveActorMeta(root, dataDir, actorName, meta); err != nil {
http.Error(w, fmt.Sprintf("save meta failed: %v", err), http.StatusInternalServerError)
return
}
// Delete old avatar file now that the new one is safely written.
if oldID != "" {
_ = os.Remove(avatarPath(dataDir, actorName, oldID))
}
iconURL := avatarPublicURL(domain, actorName, newID)
srv.SetIcon(iconURL)
go func() {
if err := srv.UpdateProfile(true); err != nil {
log.Printf("avatar: UpdateProfile for %s: %v", actorName, err)
}
}()
http.Redirect(w, r, "/backend?actor="+actorName, http.StatusSeeOther)
}
}
// ---------------------------------------------------------------------------
// New actor handler
// ---------------------------------------------------------------------------
// validActorName matches only safe actor names (lowercase letters, digits, hyphens).
var validActorName = regexp.MustCompile(`^[a-z0-9-]+$`)
// makeNewActorHandler returns a handler for POST /backend/new-actor (admin-only).
// It creates the data directory, writes a blank actor.json, registers the actor
// with the AP library, mounts its routes on mux, and saves actors.json.
func makeNewActorHandler(dataDir, domain string, root *os.Root, db *sql.DB, admins []string, registry *actorRegistry, mux *http.ServeMux) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
if r.Method != http.MethodPost {
http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
return
}
sess := sessionFromRequest(w, r)
if sess == nil {
return
}
if !inAllowlist(admins, sess.actorURL) {
http.Error(w, "Only admins can create actors.", http.StatusForbidden)
return
}
if err := r.ParseForm(); err != nil {
http.Error(w, "bad form data", http.StatusBadRequest)
return
}
name := strings.TrimSpace(r.FormValue("name"))
if name == "" {
http.Error(w, "missing actor name", http.StatusBadRequest)
return
}
if !validActorName.MatchString(name) {
http.Error(w, "actor name may only contain lowercase letters, digits and hyphens", http.StatusBadRequest)
return
}
if _, exists := registry.get(name); exists {
http.Error(w, "actor already exists", http.StatusConflict)
return
}
// Create data directory and blank actor.json.
if err := os.MkdirAll(actorDataDir(dataDir, name), 0o755); err != nil {
http.Error(w, fmt.Sprintf("create data dir: %v", err), http.StatusInternalServerError)
return
}
if err := saveActorMeta(root, dataDir, name, ActorMeta{}); err != nil {
http.Error(w, fmt.Sprintf("save actor meta: %v", err), http.StatusInternalServerError)
return
}
// Start the AP server and mount its routes.
ae := ActorEntry{Name: name}
srv, qs, err := setupActor(mux, domain, dataDir, root, db, admins, ae)
if err != nil {
http.Error(w, fmt.Sprintf("setup actor: %v", err), http.StatusInternalServerError)
return
}
registry.setEntry(name, srv, qs)
// Persist updated actors.json.
var entries []ActorEntry
for _, n := range registry.names() {
entries = append(entries, ActorEntry{Name: n})
}
if err := saveActors(dataDir, entries); err != nil {
log.Printf("new-actor: save actors.json: %v", err)
}
log.Printf("new-actor: created @%s@%s", name, domain)
http.Redirect(w, r, "/backend?actor="+name, http.StatusSeeOther)
}
}
// buildOutboxItems converts the raw outbox from an activitypub.Server into a
// slice of outboxItem values suitable for display. userInstance is used to
// construct "open on your instance" links; pass an empty string to omit them.
func buildOutboxItems(outbox []map[string]any, userInstance string) []outboxItem {
var items []outboxItem
for _, item := range outbox {
published, _ := item["published"].(string)
snippet, _ := item["contentSnippet"].(string)
// Announce: object is a string URL
// Create(Note): object is a map with a "quote" field
var obj string
kind := "boost"
switch v := item["object"].(type) {
case string:
obj = v
case map[string]any:
if q, ok := v["quote"].(string); ok {
obj = q
kind = "quote"
}
}
if obj == "" {
continue
}
openURL := ""
if userInstance != "" {
openURL = fmt.Sprintf("https://%s/authorize_interaction?uri=%s",
userInstance, url.QueryEscape(obj))
}
items = append(items, outboxItem{
Object: obj,
Published: published,
Snippet: snippet,
OpenURL: openURL,
Kind: kind,
})
}
return items
}
func inAllowlist(allowlist []string, actorURL string) bool {
return slices.Contains(allowlist, actorURL)
}
// commandRes holds one word-boundary matcher per command word. Precompiled
// rather than built on demand because DMs are handled concurrently.
//
// The word boundaries keep a command from firing on a longer word that merely
// contains it ("boosting", "rebooting") and from matching inside a URL.
var commandRes = map[string]*regexp.Regexp{
"boost": regexp.MustCompile(`(?i)\bboost\b`),
"unboost": regexp.MustCompile(`(?i)\bunboost\b`),
}
// hasCommand reports whether the DM content contains cmd as a standalone
// word, ignoring HTML markup (mentions arrive wrapped in tags) and case.
func hasCommand(content, cmd string) bool {
re, ok := commandRes[cmd]
if !ok {
return false
}
return re.MatchString(stripTags(content))
}
// mayBoost reports whether actorURL is allowed to make this actor boost
// things by DM. Admins always are; everyone else has to be a curator of
// this particular actor.
//
// An empty allowlist means nobody (except admins), NOT everybody. This is
// deliberate: the allowlist is read from disk on every DM, so treating an
// empty one as "no restriction" would turn any failure to load it — a
// missing file, a parse error, a file overwritten by something else — into
// an open boost relay. Failing closed degrades to "no service" instead.
func mayBoost(admins, allowlist []string, actorURL string) bool {
return inAllowlist(admins, actorURL) || inAllowlist(allowlist, actorURL)
}
// fetchContentSnippet fetches an AP object by URL using a signed request and
// returns the first 100 runes of its stripped plain-text content, or empty
// string on any error. Uses srv.FetchObject so requests are HTTP-signed and
// go through the SSRF-safe client (port-443-only, public IPs only).
func fetchContentSnippet(srv *activitypub.Server, objectURL string) string {
obj, err := srv.FetchObject(objectURL, activitypub.NoRedirects)
if err != nil {
return ""
}
content, _ := obj["content"].(string)
if content == "" {
return ""
}
// Strip HTML tags
plain := stripTags(content)
// Collapse whitespace
plain = strings.Join(strings.Fields(plain), " ")
// Truncate to 100 runes
runes := []rune(plain)
if len(runes) > 100 {
return string(runes[:100]) + "…"
}
return plain
}
// instanceHost extracts the hostname from an actor URL, e.g.
// "https://mastodon.xyz/users/Profpatsch" -> "mastodon.xyz".
// Returns empty string if the URL cannot be parsed.
func instanceHost(actorURL string) string {
u, err := url.Parse(actorURL)
if err != nil || u.Host == "" {
return ""
}
return u.Host
}
// dmLink returns an HTML anchor tag for a URL, for use in DM reply content.
func dmLink(u string) string {
escaped := template.HTMLEscapeString(u)
return fmt.Sprintf(`<a href="%s">%s</a>`, escaped, escaped)
}
// quotePolicy returns a short human-readable description of the quote
// policy from an AP object's interactionPolicy, for logging purposes.
func quotePolicy(apObj map[string]any) string {
policy, _ := apObj["interactionPolicy"].(map[string]any)
if policy == nil {
return "none"
}
canQuote, _ := policy["canQuote"].(map[string]any)
if canQuote == nil {
return "none"
}
auto := canQuote["automaticApproval"]
manual := canQuote["manualApproval"]
describe := func(v any) string {
if v == nil {
return "nobody"
}
var entries []string
switch val := v.(type) {
case string:
entries = []string{val}
case []any:
for _, e := range val {
if s, ok := e.(string); ok {
entries = append(entries, s)
}
}
}
var parts []string
for _, e := range entries {
switch {
case e == "https://www.w3.org/ns/activitystreams#Public":
parts = append(parts, "public")
case strings.HasSuffix(e, "/followers"):
parts = append(parts, "followers")
case strings.HasSuffix(e, "/following"):
parts = append(parts, "following")
default:
parts = append(parts, e)
}
}
if len(parts) == 0 {
return "nobody"
}
return strings.Join(parts, ",")
}
return fmt.Sprintf("auto=%s manual=%s", describe(auto), describe(manual))
}
// quoteRequiresFollow returns true when apObj's interactionPolicy indicates
// that only the author's followers may quote (i.e. the followers collection is
// in automaticApproval and as:Public is not). authorURL is the attributedTo URL.
func quoteRequiresFollow(apObj map[string]any, authorURL string) bool {
const asPublic = "https://www.w3.org/ns/activitystreams#Public"
followersURL := authorURL + "/followers"
policy, _ := apObj["interactionPolicy"].(map[string]any)
if policy == nil {
return false
}
canQuote, _ := policy["canQuote"].(map[string]any)
if canQuote == nil {
return false
}
raw := canQuote["automaticApproval"]
if raw == nil {
return false
}
// automaticApproval may be a single string or an array.
var entries []string
switch v := raw.(type) {
case string:
entries = []string{v}
case []any:
for _, e := range v {
if s, ok := e.(string); ok {
entries = append(entries, s)
}
}
}
hasFollowers := false
for _, e := range entries {
if e == asPublic {
return false // public → no follow needed
}
if e == followersURL {
hasFollowers = true
}
}
return hasFollowers
}
// actorHandle converts an actor URL to a fediverse handle, e.g.
// "https://mastodon.xyz/users/Profpatsch" -> "@Profpatsch@mastodon.xyz".
// Falls back to the raw URL if the form cannot be determined.
func actorHandle(actorURL string) string {
u, err := url.Parse(actorURL)
if err != nil || u.Host == "" {
return actorURL
}
// Last non-empty path segment is the username
parts := strings.Split(strings.Trim(u.Path, "/"), "/")
name := parts[len(parts)-1]
if name == "" {
return actorURL
}
return "@" + name + "@" + u.Host
}
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