Florianbuetow Claude Code Websocket

WebSocket Security (WS)

Analyze WebSocket implementations for security vulnerabilities including missing authentication on the upgrade handshake, no origin validation (Cross-Site WebSocket Hijacking), absence of message validation, missing rate limiting on messages, and use of unencrypted ws:// in production. WebSocket connections are long-lived and bidirectional, making them a persistent attack channel when not properly secured.

Supported Flags

Read ../../shared/schemas/flags.md for the full flag specification. This skill supports all cross-cutting flags. Key flags for this skill:

• --scope determines which files to analyze (default: changed)
• --depth standard reads code and checks WebSocket handlers and configuration
• --depth deep traces message handling from connection through all event handlers
• --severity filters output (WebSocket issues are often high or critical)

Framework Context

Key CWEs in scope:

• CWE-287: Improper Authentication (missing auth on upgrade)
• CWE-346: Origin Validation Error (CSWSH)
• CWE-20: Improper Input Validation (message validation)
• CWE-770: Allocation of Resources Without Limits (rate limiting)
• CWE-319: Cleartext Transmission of Sensitive Information (ws://)

Detection Patterns

Read references/detection-patterns.md for the full catalog of code patterns, search heuristics, language-specific examples, and false positive guidance.

Workflow

1. Determine Scope

Parse flags and resolve the file list per ../../shared/schemas/flags.md. Filter to files likely to contain WebSocket logic:

• WebSocket server setup (**/ws/**, **/websocket/**, **/socket/**)
• Socket.IO / ws configuration (**/io.*, **/socket.*)
• Message handlers (**/handlers/**, **/events/**)
• Middleware for upgrade requests (**/middleware/**)
• Client WebSocket code (**/client/**, **/frontend/**)

2. Check for Available Scanners

Detect scanners per ../../shared/schemas/scanners.md:

1. semgrep -- primary scanner for WebSocket patterns

Record which scanners are available and which are missing. WebSocket-specific scanners are rare; most analysis relies on code review.

3. Run Scanners (If Available)

If semgrep is available, run with rules targeting WebSocket:

semgrep scan --config auto --json --quiet <target>

Filter results to rules matching WebSocket patterns. Normalize output to the findings schema.

4. Claude Code Analysis

Regardless of scanner availability, perform manual code analysis:

1. Authentication on upgrade: Find WebSocket server creation and verify the upgrade/connection handler checks authentication (JWT, session cookie).
2. Origin validation: Check whether the server validates the Origin header during the WebSocket handshake to prevent CSWSH.
3. Message validation: Find message handlers and verify incoming messages are validated against a schema or type before processing.
4. Rate limiting: Check for per-connection or per-message rate limiting to prevent message flooding.
5. Transport security: Verify production configuration uses wss:// not ws:// for encrypted transport.
6. Authorization per message type: Verify sensitive operations sent via WebSocket check the user's permissions per action.

When --depth deep, additionally trace:

• Full message flow from receipt through handler to side effects
• Broadcast authorization (who receives which messages)
• Reconnection/resumption authentication

5. Report Findings

Format output per ../../shared/schemas/findings.md using the WS prefix (e.g., WS-001, WS-002).

Include for each finding:

• Severity and confidence
• Exact file location with code snippet
• Attack scenario for the WebSocket vulnerability
• Concrete fix with diff when possible
• CWE references

What to Look For

These are the high-signal patterns specific to WebSocket security. Each maps to a detection pattern in references/detection-patterns.md.

1. Missing authentication on upgrade -- WebSocket server accepts connections without verifying the client's identity during the HTTP upgrade handshake.

2. No origin validation (CSWSH) -- The server does not check the Origin header, allowing malicious websites to open WebSocket connections to the server using the victim's cookies.

3. No message validation -- Incoming WebSocket messages are parsed and processed without schema validation, enabling injection attacks.

4. No rate limiting -- No limit on message frequency, allowing a single client to flood the server with messages.

5. Unencrypted transport (ws://) -- Production WebSocket connections use ws:// instead of wss://, exposing data in transit.

Scanner Integration

Fallback (no scanner): Use Grep with patterns from references/detection-patterns.md to find WebSocket server configuration, connection handlers, message handlers, and origin checking logic. Report findings with confidence: medium.

Output Format

Use the findings schema from ../../shared/schemas/findings.md.

• ID prefix: WS (e.g., WS-001)
• metadata.tool: websocket
• metadata.framework: specialized
• metadata.category: WS
• references.cwe: CWE-287, CWE-346, CWE-20
• references.owasp: A07:2021 (Identification and Authentication Failures)
• references.stride: S (Spoofing) or T (Tampering)

Severity guidance for this category:

• critical: No authentication on upgrade for sensitive APIs, CSWSH on authenticated endpoints
• high: Missing origin validation on cookie-authenticated endpoints, no message validation
• medium: No rate limiting, ws:// in production configuration
• low: Overly permissive origin allowlist, missing secondary validation

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