Arcane Has an Authenticated Arbitrary Host File Read via Docker Compose Include Directives

## Summary `ProjectService.GetProjectFileContent` returns the contents of any Docker Compose include directive declared in a project's compose file before any path-traversal validation runs. Because `ProjectService.CreateProject` writes attacker-supplied compose content to disk without validating include paths, an authenticated user can create a project whose compose file declares `include: ['../../../../etc/passwd']`, then read the include via the project file API. The result is arbitrary read of any file readable by the Arcane backend process, including `/app/data/arcane.db` (the SQLite database containing every user's password hash and API key), enabling escalation to admin and, via Arcane's Docker control plane, RCE on the host. ## Details **Root cause #1 — `CreateProject` writes compose content without validation** (`backend/internal/services/project_service.go:1605-1644`): ```go func (s *ProjectService) CreateProject(ctx context.Context, name, composeContent string, envContent *string, user models.User) (*models.Project, error) { // ... directory setup ... if err := projects.SaveOrUpdateProjectFiles(projectsDirectory, projectPath, composeContent, envContent); err != nil { _ = s.db.WithContext(ctx).Delete(proj).Error return nil, fmt.Errorf("failed to save project files: %w", err) } // ... } ``` Compare with `UpdateProject` (project_service.go:2494, :2577), which calls `validateComposeContentForUpdate`. That validator (line 2599) loads the compose with `missingIncludeStubResourceLoaderInternal`, which calls `ValidateIncludePathForWrite` (includes.go:139) and rejects includes outside the project directory. `CreateProject` bypasses this entirely, so any malicious `include:` array survives to disk. **Root cause #2 — `GetProjectFileContent` reads include files before path validation** (`backend/internal/services/project_service.go:831-872`): ```go includes, parseErr := projects.ParseIncludes(composeFile, envMap, true) if parseErr == nil { for _, inc := range includes { if inc.RelativePath == relativePath { return project.IncludeFile{ Path: inc.Path, RelativePath: inc.RelativePath, Content: inc.Content, // <-- arbitrary file content returned here }, nil } } } fullPath := filepath.Join(proj.Path, relativePath) // ... IsSafeSubdirectory check at line 870 — never reached when include matches ... ``` **Root cause #3 — `ParseIncludes` reads include files from anywhere by design** (`backend/pkg/projects/includes.go:24-72`): ```go // Security Model for Include Files: // - READ: Docker Compose allows include files from anywhere (parent dirs, absolute paths, etc.) // We allow reading from any path to maintain compatibility with standard Docker Compose behavior // - WRITE/DELETE: Restricted to files within the project directory only for security ``` `parseIncludeItemInternal` at includes.go:97-101 builds `fullPath = filepath.Clean(filepath.Join(baseDir, includePath))` and `os.ReadFile(fullPath)` at line 105 — no containment check. The returned `RelativePath` (line 124) is `filepath.ToSlash(filepath.Clean(includePath))`, which preserves `../../../../etc/passwd` verbatim for the equality match in `GetProjectFileContent`. **Authorization surface**: The handler `GET /api/environments/{id}/projects/{projectId}/file` (`backend/internal/huma/handlers/projects.go:268-279`) and `POST /api/environments/{id}/projects` (line 242-253) only declare `BearerAuth`/`ApiKeyAuth`. There is no admin-role gate on either handler — `GetProjectFile` (line 582) and `CreateProject` (line 524) simply call `humamw.GetCurrentUserFromContext`. The default user role assigned in `users.go:223` is `"user"` (not admin), and that role is sufficient to exploit. **Resulting primitive**: arbitrary read of any file readable by the Arcane backend process (uid/gid of the container). Sensitive targets include `/app/data/arcane.db` (SQLite containing argon2 password hashes and API keys for every user), `/app/data/secrets/*`, mounted host configuration, SSH keys (if mounted), and Docker socket-adjacent secrets. ## Impact - **Arbitrary file read** as the Arcane backend process for any authenticated user, including users with the lowest-privilege `"user"` role. - **Credential disclosure**: `arcane.db` contains argon2 password hashes for every account (including admins) and API key material — supports offline cracking and direct token exfiltration. - **Privilege escalation**: a `"user"`-role attacker can recover or replay admin credentials, then exercise full Arcane functionality (Docker container/exec/volume control), which on a typical deployment with the host Docker socket mounted is host RCE. - **Configuration / secret exposure**: any environment files, OIDC client secrets, registry credentials, or files mounted into the container are reachable. - The scope crosses the security authority of other user accounts (S:C), since one authenticated user reads credentials belonging to other users and to the admin. Source Code Location: https://github.com/getarcaneapp/arcane Affected Packages: - go:github.com/getarcaneapp/arcane/backend, affected <= 1.19.3, patched in 1.19.4 CWEs: - CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') CVSS: - Primary: score 7.7, CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N - CVSS_V3: score 7.7, CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N References: - https://github.com/getarcaneapp/arcane/security/advisories/GHSA-c3px-h233-h6fq - https://github.com/getarcaneapp/arcane/commit/b6cbffabf61dbc3f12a28d3b5830e3c6b7e67daf - https://github.com/advisories/GHSA-c3px-h233-h6fq