set_bucket_policy · Rustfs MCP: Risk & Policy

WHAT IT DOES

What set_bucket_policy does on Rustfs

AI agents use set_bucket_policy to create or update resources in Rustfs — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Rustfs environment.

WHY IT NEEDS A POLICY

Why set_bucket_policy needs a policy

Setting bucket policies modifies S3 access control rules and permissions, which can grant or revoke access to sensitive data. This is a Write operation because policy changes are reversible (can be updated or deleted), but the blast radius is high because misconfigured policies could expose or lock down entire buckets, affecting data availability and security posture.

From the tool's definition Tool name 'set_bucket_policy' and description 'Set a bucket policy (JSON string)' indicate modification of bucket access control policies, a reversible configuration change.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_bucket_policy Rate-limited

set_bucket_policy stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "set_bucket_policy": {
      "limits": [
        {
          "counter": "set_bucket_policy_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about set_bucket_policy

What does the set_bucket_policy tool do? +

Set a bucket policy (JSON string). (Refused on read-only / production add-ons.). It is categorised as a Write tool in the Rustfs MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on set_bucket_policy? +

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

What risk level is set_bucket_policy? +

set_bucket_policy is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit set_bucket_policy? +

Yes. Add a rate_limit block to the set_bucket_policy 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 set_bucket_policy completely? +

Set action: deny in the PolicyLayer policy for set_bucket_policy. 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 set_bucket_policy? +

set_bucket_policy is provided by the Rustfs MCP server (stackblaze/rustfs-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.