GHSA-598g-h2vc-h5vg: nebula-mesh: API endpoints lack ownership checks, enabling cross-operator privilege escalation
The `/api/v1/*` route surface trusts the bearer token alone for authorisation on most endpoints. The codebase itself admits this at `internal/api/hosts.go:384`: *"API trusts the bearer token for authorisation; per-CA ownership is enforced only in the Web layer."*The Web UI gates state-changing routes through `loadAccessibleCA` (`internal/web/cas.go`); CA-management endpoints in `internal/api/cas.go` ALSO have proper `canAccessCA` gates. **The gap is on the host, network, firewall, mobile-bundle, and most operator endpoints.** Combined with the per-operator CA model from ADR 0002, this gives any non-admin operator API key broad cross-tenant access — instant privilege escalation in the worst case.AffectedAll released versions prior to v0.3.4.Exploit chainA) Mint admin API key from any operator key (instant privilege escalation)`internal/api/operators.go:118` — `handleCreateOperatorAPIKey` does no admin check and no actor/target-operator ownership check. Any operator key can call it for any operator (including admins) and receive a fresh bearer.Reuse the returned key for subsequent requests → full admin.B) Cross-operator host takeover via reenroll`internal/api/hosts.go:321,330` → `mintEnrollmentTokenForHost`. Looks up host by URL param, mints a single-use enrollment token, returns it. No ownership check.Caller POSTs `/api/v1/enroll` with their own X25519 + Ed25519 keypairs. `enroll.go:175` overwrites `signing_pub_pem`; `SaveCertificateAndEnrollHost` overwrites the cert. Legitimate agent's next signed poll fails `bad_signature`. Attacker now owns the victim's Nebula identity.C) Cross-tenant CRUD on hosts, networks, firewallThe same gap applies across:`/api/v1/hosts*` — create, list, get, update, delete, block, unblock`/api/v1/networks*` — create, list, get`/api/v1/networks/{id}/firewall` — get, PUT`/api/v1/hosts/{id}/mobile-bundle` (already filed as public issue #119)All trust bearer-auth alone. Any operator can read or mutate any other operator's resources.Affected operator-management handlers (in addition to A)Beyond `handleCreateOperatorAPIKey` (covered by A), `internal/api/operators.go` is missing admin gates on:`handleListOperators` (line 66) — operator roster info disclosure`handleDisableOperator` (line 79) — DoS / sabotage`handleEnableOperator` (line 94) — re-enable disabled operators`handleRevokeOperatorAPIKey` (line 157) — invalidate any operator's API keys`handleListOperatorAPIKeys` (line 173) — API-key metadata disclosure`handleCreateOperator` (line 26) IS properly gated (`actorIsAdmin` at line 27).NOT affected (verified)`internal/api/cas.go` properly gates every CA endpoint via `canAccessCA` (calls at lines 70, 176, 216) and admin shortcuts at lines 39, 82. An earlier description draft mistakenly listed `/api/v1/cas/{id}/rotate` as affected — that endpoint is properly protected. CAs are not in this gap.ImpactAny non-admin operator → admin via one curl (A).Any non-admin operator → ownership of any victim's hosts with cert + identity transfer (B).Mass cross-tenant CRUD including firewall-rule mutation (C).Any operator → disable/enable other operators, revoke their API keys, enumerate the operator roster.CVSS 3.1: AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H — 9.6.Suggested fixShared helpers in a new `internal/api/authz.go`, mirroring the Web layer's `loadAccessibleCA`:Each loads the resource, resolves its CA via `*.CAID`, accepts if `actorIsAdmin(ctx)` OR actor owns the CA. Reject `403 forbidden`; audit-log `api.<resource>.forbidden` with the reason.The operator-management endpoints take `requireAdmin` instead (operator ownership doesn't map to CA ownership).Apply at the top of every host-, network-, firewall-, mobile-bundle-touching API handler, plus the 5 operator endpoints listed above. The legacy config-key path retains admin (preserves backward compatibility); the broader legacy-fallback question is tracked separately as issue #121.Test matrixadmin → all operations permittedowning non-admin → operations on owned hosts/networks permittednon-owner non-admin → 403 + audit entrylegacy config-key → preserved (admin)unauthenticated → existing 401 from middlewareCoordinated contextSubsumes public issue #119 (mobile-bundle authz). Issue #121 (actor.go:40 legacy-admin fallback) is a separate concern tracked independently.
CVSS v3.1: 9.9