Arcane Vulnerable to Unauthenticated Disclosure of Custom Compose Template Content (incl. `.env` secrets)

Summary

Four GET endpoints under /api/templates* in Arcane's Huma backend are registered without any Security requirement, allowing any unauthenticated network client to list and read the full Compose YAML and .env content of every custom template stored in the instance. Because Arcane's UI exposes a "Save as Template" flow on the project / swarm-stack creation pages that persists the operator's real env content (database passwords, API keys, etc.) verbatim, this missing authorization is an unauthenticated read of operator secrets in practice — not a theoretical info-disclosure.

The frontend explicitly treats /customize/templates/* as an authenticated area (PROTECTED_PREFIXES in frontend/src/lib/utils/redirect.util.ts), and every CRUD operation (POST/PUT/DELETE) on the same paths requires a Bearer/API key, so this is a clear backend authorization gap, not intended public access.

Details

Affected file: backend/internal/huma/handlers/templates.go:194-228.

In RegisterTemplates, four huma.Register calls have no Security: block:

// templates.go
huma.Register(api, huma.Operation{
    OperationID: "listTemplatesPaginated",
    Method:      "GET",
    Path:        "/templates",
    ...
    // <-- no Security
}, h.ListTemplates)

huma.Register(api, huma.Operation{
    OperationID: "getAllTemplates",
    Method:      "GET",
    Path:        "/templates/all",
    ...
}, h.GetAllTemplates)

huma.Register(api, huma.Operation{
    OperationID: "getTemplate",
    Method:      "GET",
    Path:        "/templates/{id}",
    ...
}, h.GetTemplate)

huma.Register(api, huma.Operation{
    OperationID: "getTemplateContent",
    Method:      "GET",
    Path:        "/templates/{id}/content",
    ...
}, h.GetTemplateContent)

Arcane's auth bridge (backend/internal/huma/middleware/auth.go:168-172) only enforces authentication when the operation declares one of the security schemes (BearerAuth or ApiKeyAuth). With Security omitted, parseSecurityRequirements returns isRequired=false and the request flows through with no token check.

TemplateHandler.GetTemplateContent (templates.go:478-499) calls templateService.GetTemplateContentWithParsedData (backend/internal/services/template_service.go:1303-1347), which returns the model's Content, EnvContent, parsed services, and parsed env-variable key/value pairs verbatim. The model () stores and as plain columns and has no owner / user binding.