Security

Encryption

All traffic between the client and server is end-to-end encrypted. The relay only sees opaque binary blobs.

Layer	Algorithm
Key exchange	X25519 ECDH
Key derivation	HKDF-SHA256 (pairing code as salt)
Encryption	AES-256-GCM

MITM protection

The pairing code is cryptographically bound into key derivation via the HKDF salt. After key exchange, both sides derive and exchange a SAS (Short Authentication String) verification tag over the encrypted channel. If a man-in-the-middle substitutes public keys, the derived keys will differ and the SAS tags won't match — the connection is aborted.

This is inspired by Magic Wormhole's approach of binding a short code into the cryptographic handshake.

Pairing codes

• 8-digit numeric codes generated with Python's secrets module (cryptographic PRNG)
• Maximum 5 attempts per session — after 5 wrong codes, the session is destroyed
• Sessions expire after 120 seconds if unpaired

Relay trust model

The relay is untrusted by design:

• It never sees decrypted traffic
• It cannot forge or inject frames (all data is authenticated by AES-256-GCM)
• It only forwards WebSocket messages between paired sessions
• A single agent and single client connection is enforced per session

You can use the public relay at mykube.onrender.com or self-host your own.

Additional protections

Protection	Details
Rate limiting	20 requests/min per IP on API endpoints
Session hijacking	Duplicate agent/client connections are rejected
Temp file permissions	Kubeconfig written with mode 0600 to a random path, deleted on exit
Input sanitization	Cluster names stripped to [a-zA-Z0-9._-] before use in paths and shell commands
WebSocket message size	16 MiB limit on both CLI and relay

Known issues tracker

The table below tracks all identified security issues and their status.

Fixed

#	Issue	Fix
1	K8s credentials exposed to relay	E2E encryption (X25519 + HKDF + AES-256-GCM + SAS)
4	Weak pairing code / non-crypto PRNG	secrets module, 8-digit codes
5	World-readable temp file	os.CreateTemp (mode 0600, random path)
6	Path traversal via ClusterName	SanitizeClusterName strips to [a-zA-Z0-9._-]
7	Shell injection via ClusterName	Same sanitization applied in RC file
8	YAML injection via ClusterName	Sanitized name used in template
9	No rate limiting	20 req/min per IP on /api/*
11	No WS message size limit	16 MiB limit on CLI and relay
13	Session hijacking (duplicate connections)	Reject if agent/client already connected
14	ConnID spoofing	E2E encryption means relay can't forge frames
15	Unbounded WS reads	SetReadLimit(16 MiB) on both sides
18	Symlink attack on temp file	os.CreateTemp with O_EXCL
20	random instead of secrets	Uses secrets.choice

Open

#	Issue	Severity
2	insecure-skip-tls-verify in generated kubeconfig	Critical
3	No authentication on relay endpoints	Critical
10	No WebSocket Origin validation	High
12	Unbounded session count	Medium
16	No handshake field validation	Medium
17	No CORS middleware	Medium
19	Busy-wait polling loops	Low
21	Broad except Exception: pass	Low