Preventing Protocol-Level Vulnerabilities in the Griffin Proxy

A. How X is implemented in Griffin?

Griffin use rusttls under the hood. With proper configuration, it already prevent some popular protocol-level attacks.

B. Classification of Protocol-level Attacks Vectors

1. Downgrade Attacks

Attackers try to force the connection to fall back to a weaker protocol.

Examples

• Forcing TLS 1.3 → TLS 1.0
• Downgrading cipher suites to weak ones
• Breaking HTTP/2 to HTTP/1.1 and
• injecting vulnerabilities

Implications: If your proxy accidentally accepts weaker modes, attackers can hijack or decrypt traffic.

Prevention

• Disable TLS < 1.2
• Prefer TLS 1.3
• Disable all weak ciphers
• Rustls already prevents downgrade attacks by design

2. MITM via Weak Certificate Validation

If a TLS stack does not validate SAN, CN, signature, or chain properly → attackers insert fake certs.

Examples

• Accepting expired certificates
• Accepting wrong hostname
• Not validating SAN
• Trusting a self-signed cert accidentally

Prevention

• Always validate hostnames
• Always validate certificate chain
• Rustls has strong strict hostname checking

3. Replay Attacks

Captured requests get replayed (especially POST requests).

Where it matters

• Authentication tokens
• Nonces
• Payment requests

Prevention

• Use nonce, timestamp, or expiring tokens (JWT)
• Use TLS 1.3 (built-in anti-replay for 0-RTT)

4. 0-RTT Replay Attack (TLS 1.3)

A unique TLS 1.3 issue: early data (0-RTT) can be replayed.

Prevention

• Disable 0-RTT unless you know what you’re doing
• Rustls: do not enable 0-RTT for sensitive operations

5. Certificate Injection Attacks

If your proxy loads certificates dynamically and you do not authenticate them, attackers may inject malicious certs.

Prevention

• Sign certificates with a known CA
• Validate issuer
• Match private key to cert
• Never allow arbitrary PEM loading without validation

6. SNI-based Attacks

Proxy picks the wrong certificate because:

• SNI is missing
• SNI is spoofed
• Proxy has fallback cert that exposes sensitive domain

Prevention

• Require SNI for HTTPS
• Reject empty SNI for TLS 1.2
• Rustls supports strict SNI routing

7. TLS Renegotiation Attack

TLS renegotiation historically allowed MITM injection.

Prevention

• Fully disable renegotiation
• Rustls does not support renegotiation → safe

8. Beast, Crime, Poodle, Lucky13

These are old TLS/SSL attacks.

Good news:

• Rustls does not implement SSLv2/v3,
• avoiding all these issues
• TLS 1.3 removes many old cipher pitfalls

Still, avoid using:

• CBC mode ciphers
• RC4
• TLS 1.0/1.1

9. Sidechannel Attacks

Like timing attacks if you implement crypto incorrectly.

Example

• Non-constant-time comparison leaks key info
• RSA padding oracle attacks (Bleichenbacher)

Prevention

• Use Rustls/OpenSSL — don’t implement crypto yourself
• Avoid custom crypto unless absolutely necessary

10. ALPN Manipulation

If your proxy does not validate ALPN negotiation:

• Attacker can force HTTP/1.1 instead of HTTP/2
• Or downgrade gRPC → HTTP fallback

Prevention

• Specify allowed ALPN list explicitly
• Rustls supports ALPN safely