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Sandbox artifact rendering via iframe + CSP

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Splits /p/{slug} into a trusted wrapper (HTML with a sandboxed iframe)
and /p/{slug}/raw (the artifact itself, served with Content-Security-Policy:
sandbox). Artifact JS now runs in an opaque origin and can't read admin
cookies or make same-origin credentialed requests to /a/* or /api/*.
Password gating is enforced on both routes so /raw can't be used to bypass
the unlock flow.
This commit is contained in:
dtoro
2026-04-23 13:59:50 +02:00
parent 2b0ab836fe
commit 9e3443079f
3 changed files with 54 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
internal/server/artifact.go
View File

@@ -33,17 +33,42 @@ func (s *Server) getArtifact(w http.ResponseWriter, r *http.Request) {
return return
} }
s.render(w, "artifact_wrapper", struct{ Slug string }{Slug: slug})
// Log view asynchronously. Failures are non-fatal.
go s.logView(r, slug)
}
func (s *Server) getArtifactRaw(w http.ResponseWriter, r *http.Request) {
slug := chi.URLParam(r, "slug")
art, err := s.store.GetArtifact(slug)
if err != nil {
http.NotFound(w, r)
return
}
if art.ExpiresAt != nil && time.Now().After(*art.ExpiresAt) {
http.NotFound(w, r)
return
}
if art.HasPassword && !s.artifact.Verify(r, slug) {
http.NotFound(w, r)
return
}
body, err := os.ReadFile(s.store.ArtifactPath(slug)) body, err := os.ReadFile(s.store.ArtifactPath(slug))
if err != nil { if err != nil {
http.Error(w, "artifact missing on disk", http.StatusInternalServerError) http.Error(w, "artifact missing on disk", http.StatusInternalServerError)
return return
} }
// CSP: sandbox — if this URL is loaded directly (not via the wrapper
// iframe), the browser applies the same restrictions as an iframe
// sandbox, preventing artifact JS from reading cookies or making
// same-origin credentialed requests to the admin surface.
w.Header().Set("Content-Security-Policy",
"sandbox allow-scripts allow-forms allow-popups allow-popups-to-escape-sandbox allow-modals")
w.Header().Set("Content-Type", "text/html; charset=utf-8") w.Header().Set("Content-Type", "text/html; charset=utf-8")
w.Write(body) w.Write(body)
// Log view asynchronously. Failures are non-fatal.
go s.logView(r, slug)
} }
func (s *Server) postUnlock(w http.ResponseWriter, r *http.Request) { func (s *Server) postUnlock(w http.ResponseWriter, r *http.Request) {

11
internal/server/server.go
View File

@@ -75,8 +75,12 @@ func (s *Server) Handler() http.Handler {
r.Get("/login", s.getLogin) r.Get("/login", s.getLogin)
r.Post("/login", s.postLogin) r.Post("/login", s.postLogin)
// Artifact serving (public; password gating is per-artifact) // Artifact serving (public; password gating is per-artifact).
// /p/{slug} renders a sandbox-iframe wrapper; /p/{slug}/raw serves the
// artifact HTML itself with CSP: sandbox so cookies + same-origin XHR
// are unavailable to artifact JS whether loaded via iframe or directly.
r.Get("/p/{slug}", s.getArtifact) r.Get("/p/{slug}", s.getArtifact)
r.Get("/p/{slug}/raw", s.getArtifactRaw)
r.Post("/p/{slug}/unlock", s.postUnlock) r.Post("/p/{slug}/unlock", s.postUnlock)
// Admin-only routes // Admin-only routes
@@ -127,8 +131,9 @@ func (s *Server) RollupLoop(stop <-chan struct{}) {
func securityHeaders(next http.Handler) http.Handler { func securityHeaders(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
// Note: no CSP on /p/{slug} since artifact HTML often uses inline scripts + CDNs. // The raw artifact endpoint sets its own CSP: sandbox; skip ours here.
if !strings.HasPrefix(r.URL.Path, "/p/") { isRaw := strings.HasPrefix(r.URL.Path, "/p/") && strings.HasSuffix(r.URL.Path, "/raw")
if !isRaw {
w.Header().Set("Content-Security-Policy", w.Header().Set("Content-Security-Policy",
"default-src 'self'; "+ "default-src 'self'; "+
"script-src 'self' https://unpkg.com https://cdn.tailwindcss.com 'unsafe-inline'; "+ "script-src 'self' https://unpkg.com https://cdn.tailwindcss.com 'unsafe-inline'; "+

18
internal/server/templates/artifact_wrapper.html Normal file
View File

@@ -0,0 +1,18 @@
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>artifact</title>
<style>
html, body { margin: 0; padding: 0; height: 100%; background: #fff; }
iframe { display: block; width: 100%; height: 100vh; border: 0; }
</style>
</head>
<body>
<iframe sandbox="allow-scripts allow-forms allow-popups allow-popups-to-escape-sandbox allow-modals"
src="/p/{{.Slug}}/raw"
referrerpolicy="no-referrer"
title="artifact"></iframe>
</body>
</html>