TrustTunnel is an open-source VPN protocol with a rule bypass issue in versions prior to 0.9.115. In tls_listener.rs, TlsListener::listen() peeks 1024 bytes and calls extract_client_random(...). If parse_tls_plaintext fails (for example, a fragmented/partial ClientHello split across TCP writes), extract_client_random returns None. In rules.rs, RulesEngine::evaluate only evaluates client_random_prefix when client_random is Some(...). As a result, when extraction fails (client_random == None), any rule that relies on client_random_prefix matching is skipped and evaluation falls through to later rules. As an important semantics note: client_random_prefix is a match condition only. It does not mean block non-matching prefixes by itself. A rule with client_random_prefix = ... triggers its action only when the prefix matches (and the field is available to evaluate). Non-matches (or None) simply do not match that rule and continue to fall through. The vulnerability is fixed in version 0.9.115.
Weakness
The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.
Extended Description
Access control involves the use of several protection mechanisms such as:
When any mechanism is not applied or otherwise fails, attackers can compromise the security of the product by gaining privileges, reading sensitive information, executing commands, evading detection, etc. There are two distinct behaviors that can introduce access control weaknesses:
Potential Mitigations
- Compartmentalize the system to have “safe” areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
- Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
Related Attack Patterns
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