open_session · Ssh MCP: Risk & Policy

WHAT IT DOES

What open_session does on Ssh

AI agents invoke open_session to trigger actions in Ssh. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why open_session needs a policy

Opening an SSH session initiates an external connection to a remote system, establishing a persistent interactive shell. This is an Execute-category action because it triggers an external operation (remote SSH connection) whose effects depend on the target host and profile.

From the tool's definition Open a persistent interactive SSH session from a named profile

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

open_session Rate-limited

open_session stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "open_session": {
      "limits": [
        {
          "counter": "open_session_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Ssh, so you can run agents against it safely.

FAQ

Questions about open_session

What does the open_session tool do? +

Open a persistent interactive SSH session from a named profile. It is categorised as a Execute tool in the Ssh MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on open_session? +

Register the Ssh MCP server in PolicyLayer and add a rule for open_session: 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 Ssh. Nothing to install.

What risk level is open_session? +

open_session is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit open_session? +

Yes. Add a rate_limit block to the open_session 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.

How do I block open_session completely? +

Set action: deny in the PolicyLayer policy for open_session. 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.

What MCP server provides open_session? +

open_session is provided by the Ssh MCP server (sc-ml-cmd/ssh-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.