base-security-scanner-mcp

Instructions

Implementation Reference

• src/index.ts:777-868 (handler)

  Implementation of the check_token_permissions MCP tool. It retrieves the contract bytecode, extracts selectors, checks for specific dangerous function selectors, retrieves ownership information, and summarizes the findings.

  server.tool(
    "check_token_permissions",
    "Check owner permissions on a token: can mint? can pause? can blacklist? can change fees? Can disable trading? Ownership renounced?",
    {
      token_address: z.string().describe("Token contract address on Base mainnet"),
    },
    async ({ token_address }) => {
      try {
        const code = await getContractBytecode(token_address);
        if (code === "0x" || code.length <= 2) {
          return ok({ token: token_address, isContract: false, message: "Not a contract" });
        }
  
        const selectors = extractSelectors(code);
        const ownership = await checkOwnership(token_address);
  
        const permissions: Record<string, { present: boolean; risk: string; detail: string }> = {
          canMint: {
            present: selectors.includes("40c10f19"),
            risk: "critical",
            detail: "mint(address,uint256) -- can create new tokens",
          },
          canPause: {
            present: selectors.includes("8456cb59"),
            risk: "high",
            detail: "pause() -- can freeze all transfers",
          },
          canBlacklist: {
            present: selectors.includes("44337ea1"),
            risk: "high",
            detail: "blacklist(address) -- can block specific addresses",
          },
          canChangeFees: {
            present: selectors.includes("69fe0e2d"),
            risk: "high",
            detail: "setFee(uint256) -- can change transaction fees",
          },
          canDisableTrading: {
            present: selectors.includes("1a8145bb"),
            risk: "critical",
            detail: "setTradingActive(bool) -- can disable all trading",
          },
          canSetMaxTx: {
            present: selectors.includes("e4748b9e"),
            risk: "high",
            detail: "setMaxTxAmount(uint256) -- can restrict transaction sizes",
          },
          canSetMaxWallet: {
            present: selectors.includes("8ee88c53"),
            risk: "high",
            detail: "setMaxWalletSize(uint256) -- can restrict wallet holdings",
          },
          canBurnOthers: {
            present: selectors.includes("79cc6790"),
            risk: "medium",
            detail: "burnFrom(address,uint256) -- can burn tokens from other addresses",
          },
          canUpgrade: {
            present: selectors.includes("3659cfe6") || selectors.includes("4f1ef286"),
            risk: "critical",
            detail: "upgradeTo/upgradeToAndCall -- proxy can be upgraded to new logic",
          },
          canRenounceOwnership: {
            present: selectors.includes("715018a6"),
            risk: "info",
            detail: "renounceOwnership() -- ownership can be given up (positive sign)",
          },
          canTransferOwnership: {
            present: selectors.includes("f2fde38b"),
            risk: "medium",
            detail: "transferOwnership(address) -- ownership can be moved to another address",
          },
        };
  
        const dangerousPermissions = Object.entries(permissions)
          .filter(([, v]) => v.present && (v.risk === "critical" || v.risk === "high"))
          .map(([k]) => k);
  
        return ok({
          token: token_address,
          ownership: serializeBigInts(ownership) as Record<string, unknown>,
          permissions,
          dangerousPermissions,
          riskSummary: dangerousPermissions.length === 0
            ? "No dangerous owner permissions detected"
            : `${dangerousPermissions.length} dangerous permission(s) found: ${dangerousPermissions.join(", ")}`,
        });
      } catch (err) {
        return fail(`check_token_permissions failed: ${err instanceof Error ? err.message : String(err)}`);
      }
    }
  );