Summarize TLS handshake/fingerprint availability (JA3/JA4/JA3S) for session exchanges.
AI agents call proxy_get_session_handshakes to retrieve information from Proxy without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This is a Read operation that queries existing TLS session data without side effects. However, severity is medium rather than low due to the sensitive nature of cryptographic handshake information—exposing TLS fingerprints and handshake details could enable fingerprinting attacks, spoofing detection evasion, or man-in-the-middle analysis.
From the tool's definition Tool retrieves summary of TLS handshake and fingerprint data (JA3/JA4/JA3S) for session exchanges. The verb 'summarize' and noun 'availability' clearly indicate data retrieval with no modification or execution.
Documented attack patterns abuse exactly the kind of access proxy_get_session_handshakes gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Proxy, and nothing reaches the server without passing your rules. This is the rule we recommend for proxy_get_session_handshakes:
{
"version": "1",
"default": "deny",
"tools": {
"proxy_get_session_handshakes": {}
}
}proxy_get_session_handshakes is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Summarize TLS handshake/fingerprint availability (JA3/JA4/JA3S) for session exchanges. It is categorised as a Read tool in the Proxy MCP Server, which means it retrieves data without modifying state.
Register the Proxy MCP server in PolicyLayer and add a rule for proxy_get_session_handshakes: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Proxy. Nothing to install.
proxy_get_session_handshakes is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the proxy_get_session_handshakes rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for proxy_get_session_handshakes. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
proxy_get_session_handshakes is provided by the Proxy MCP server (yfe404/proxy-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Proxy, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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