Add validation for ERC20 premint amount to prevent "Literal too large" error (#488)

Co-authored-by: Eric Lau <[email protected]>

Author: hashpalk

packages/core/solidity/CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## Unreleased
+
+- Add validation for ERC20 premint field. ([#488](https://github.com/OpenZeppelin/contracts-wizard/pull/488))
+
 ## 0.5.3 (2025-03-13)
 
 - Add ERC20 Cross-Chain Bridging, SuperchainERC20. ([#436](https://github.com/OpenZeppelin/contracts-wizard/pull/436))

packages/core/solidity/src/erc20.test.ts

@@ -69,6 +69,43 @@ testERC20('erc20 premint of 0', {
   premint: '0',
 });
 
+function testPremint(scenario: string, premint: string, expectedError?: string) {
+  test(`erc20 premint - ${scenario} - ${expectedError ? 'invalid' : 'valid'}`, async t => {
+    if (expectedError) {
+      const error = t.throws(() =>
+        buildERC20({
+          name: 'MyToken',
+          symbol: 'MTK',
+          premint,
+        }),
+      );
+      t.is((error as OptionsError).messages.premint, expectedError);
+    } else {
+      const c = buildERC20({
+        name: 'MyToken',
+        symbol: 'MTK',
+        premint,
+      });
+      t.snapshot(printContract(c));
+    }
+  });
+}
+
+testPremint('max literal', '115792089237316195423570985008687907853269984665640564039457.584007913129639935'); // 2^256 - 1, shifted by 18 decimals
+testPremint(
+  'max literal + 1',
+  '115792089237316195423570985008687907853269984665640564039457.584007913129639936',
+  'Value is greater than uint256 max value',
+);
+testPremint('no arithmetic overflow', '115792089237316195423570985008687907853269984665640564039457'); // 2^256 - 1, truncated by 18 decimals
+testPremint(
+  'arithmetic overflow',
+  '115792089237316195423570985008687907853269984665640564039458',
+  'Amount would overflow uint256 after applying decimals',
+);
+testPremint('e notation', '1e59');
+testPremint('e notation arithmetic overflow', '1e60', 'Amount would overflow uint256 after applying decimals');
+
 testERC20('erc20 mintable', {
   mintable: true,
   access: 'ownable',

packages/core/solidity/src/erc20.test.ts.md

@@ -235,6 +235,69 @@ Generated by [AVA](https://avajs.dev).
     }␊
     `
 
+## erc20 premint - max literal - valid
+
+> Snapshot 1
+
+    `// SPDX-License-Identifier: MIT␊
+    // Compatible with OpenZeppelin Contracts ^5.0.0␊
+    pragma solidity ^0.8.22;␊
+    ␊
+    import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";␊
+    import {ERC20Permit} from "@openzeppelin/contracts/token/ERC20/extensions/ERC20Permit.sol";␊
+    ␊
+    contract MyToken is ERC20, ERC20Permit {␊
+        constructor(address recipient)␊
+            ERC20("MyToken", "MTK")␊
+            ERC20Permit("MyToken")␊
+        {␊
+            _mint(recipient, 115792089237316195423570985008687907853269984665640564039457584007913129639935 * 10 ** (decimals() - 18));␊
+        }␊
+    }␊
+    `
+
+## erc20 premint - no arithmetic overflow - valid
+
+> Snapshot 1
+
+    `// SPDX-License-Identifier: MIT␊
+    // Compatible with OpenZeppelin Contracts ^5.0.0␊
+    pragma solidity ^0.8.22;␊
+    ␊
+    import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";␊
+    import {ERC20Permit} from "@openzeppelin/contracts/token/ERC20/extensions/ERC20Permit.sol";␊
+    ␊
+    contract MyToken is ERC20, ERC20Permit {␊
+        constructor(address recipient)␊
+            ERC20("MyToken", "MTK")␊
+            ERC20Permit("MyToken")␊
+        {␊
+            _mint(recipient, 115792089237316195423570985008687907853269984665640564039457 * 10 ** decimals());␊
+        }␊
+    }␊
+    `
+
+## erc20 premint - e notation - valid
+
+> Snapshot 1
+
+    `// SPDX-License-Identifier: MIT␊
+    // Compatible with OpenZeppelin Contracts ^5.0.0␊
+    pragma solidity ^0.8.22;␊
+    ␊
+    import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";␊
+    import {ERC20Permit} from "@openzeppelin/contracts/token/ERC20/extensions/ERC20Permit.sol";␊
+    ␊
+    contract MyToken is ERC20, ERC20Permit {␊
+        constructor(address recipient)␊
+            ERC20("MyToken", "MTK")␊
+            ERC20Permit("MyToken")␊
+        {␊
+            _mint(recipient, 100000000000000000000000000000000000000000000000000000000000 * 10 ** decimals());␊
+        }␊
+    }␊
+    `
+
 ## erc20 mintable
 
 > Snapshot 1

packages/core/solidity/src/erc20.test.ts.snap

@@ -13,6 +13,7 @@ import type { ClockMode } from './set-clock-mode';
 import { clockModeDefault, setClockMode } from './set-clock-mode';
 import { supportsInterface } from './common-functions';
 import { OptionsError } from './error';
+import { toUint256, UINT256_MAX } from './utils/convert-strings';
 
 export const crossChainBridgingOptions = [false, 'custom', 'superchain'] as const;
 export type CrossChainBridging = (typeof crossChainBridgingOptions)[number];
@@ -163,6 +164,14 @@ export function isValidChainId(str: string): boolean {
   return chainIdPattern.test(str);
 }
 
+function scaleByPowerOfTen(base: bigint, exponent: number): bigint {
+  if (exponent < 0) {
+    return base / BigInt(10) ** BigInt(-exponent);
+  } else {
+    return base * BigInt(10) ** BigInt(exponent);
+  }
+}
+
 function addPremint(
   c: ContractBuilder,
   amount: string,
@@ -181,6 +190,9 @@ function addPremint(
       const units = integer + decimals + zeroes;
       const exp = decimalPlace <= 0 ? 'decimals()' : `(decimals() - ${decimalPlace})`;
 
+      const validatedBaseUnits = toUint256(units, 'premint');
+      checkPotentialPremintOverflow(validatedBaseUnits, decimalPlace);
+
       c.addConstructorArgument({ type: 'address', name: 'recipient' });
 
       const mintLine = `_mint(recipient, ${units} * 10 ** ${exp});`;
@@ -212,6 +224,24 @@ function addPremint(
   }
 }
 
+/**
+ * Check for potential premint overflow assuming the user's contract has decimals() = 18
+ *
+ * @param baseUnits The base units of the token, before applying power of 10
+ * @param decimalPlace If positive, the number of assumed decimal places in the least significant digits of `validatedBaseUnits`. Ignored if <= 0.
+ * @throws OptionsError if the calculated value would overflow uint256
+ */
+function checkPotentialPremintOverflow(baseUnits: bigint, decimalPlace: number) {
+  const assumedExp = decimalPlace <= 0 ? 18 : 18 - decimalPlace;
+  const calculatedValue = scaleByPowerOfTen(baseUnits, assumedExp);
+
+  if (calculatedValue > UINT256_MAX) {
+    throw new OptionsError({
+      premint: 'Amount would overflow uint256 after applying decimals',
+    });
+  }
+}
+
 function addMintable(c: ContractBuilder, access: Access) {
   requireAccessControl(c, functions.mint, access, 'MINTER', 'minter');
   c.addFunctionCode('_mint(to, amount);', functions.mint);

packages/core/solidity/src/erc20.ts

@@ -0,0 +1,23 @@
+import test from 'ava';
+
+import { toUint256, UINT256_MAX } from './convert-strings';
+import { OptionsError } from '../error';
+
+test('toUint256', t => {
+  t.is(toUint256('123', 'foo'), BigInt(123));
+});
+
+test('toUint256 - not number', t => {
+  const error = t.throws(() => toUint256('abc', 'foo'), { instanceOf: OptionsError });
+  t.is(error.messages.foo, 'Not a valid number');
+});
+
+test('toUint256 - negative', t => {
+  const error = t.throws(() => toUint256('-1', 'foo'), { instanceOf: OptionsError });
+  t.is(error.messages.foo, 'Not a valid number');
+});
+
+test('toUint256 - too large', t => {
+  const error = t.throws(() => toUint256(String(UINT256_MAX + BigInt(1)), 'foo'), { instanceOf: OptionsError });
+  t.is(error.messages.foo, 'Value is greater than uint256 max value');
+});

packages/core/solidity/src/utils/convert-strings.test.ts

@@ -0,0 +1,27 @@
+import { OptionsError } from '../error';
+
+export const UINT256_MAX = BigInt(2) ** BigInt(256) - BigInt(1);
+
+/**
+ * Checks that a string is a valid `uint256` value and converts it to bigint.
+ *
+ * @param value The value to check.
+ * @param field The field name to use in the error if the value is invalid.
+ * @throws OptionsError if the value is not a valid number or is greater than the maximum value for `uint256`.
+ * @returns The value as a bigint.
+ */
+export function toUint256(value: string, field: string): bigint {
+  const isValidNumber = /^\d+$/.test(value);
+  if (!isValidNumber) {
+    throw new OptionsError({
+      [field]: 'Not a valid number',
+    });
+  }
+  const numValue = BigInt(value);
+  if (numValue > UINT256_MAX) {
+    throw new OptionsError({
+      [field]: 'Value is greater than uint256 max value',
+    });
+  }
+  return numValue;
+}