Add Base64Url encoding (#4822)

Co-authored-by: Ernesto García <ernestognw@gmail.com>

test/utils/Base64.t.sol

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.20;
+
+import {Test} from "forge-std/Test.sol";
+
+import {Base64} from "@openzeppelin/contracts/utils/Base64.sol";
+
+/// NOTE: This test requires `ffi` to be enabled. It does not run in the CI
+/// environment given `ffi` is not recommended.
+/// See: https://github.com/foundry-rs/foundry/issues/6744
+contract Base64Test is Test {
+    function testEncode(bytes memory input) external {
+        string memory output = Base64.encode(input);
+        assertEq(output, _base64Ffi(input, "encode"));
+    }
+
+    function testEncodeURL(bytes memory input) external {
+        string memory output = Base64.encodeURL(input);
+        assertEq(output, _base64Ffi(input, "encodeURL"));
+    }
+
+    function _base64Ffi(bytes memory input, string memory fn) internal returns (string memory) {
+        string[] memory command = new string[](4);
+        command[0] = "bash";
+        command[1] = "scripts/tests/base64.sh";
+        command[2] = fn;
+        command[3] = vm.toString(input);
+        bytes memory retData = vm.ffi(command);
+        return string(retData);
+    }
+}

test/utils/Base64.test.js

@@ -2,6 +2,10 @@ const { ethers } = require('hardhat');
 const { expect } = require('chai');
 const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
 
+// Replace "+/" with "-_" in the char table, and remove the padding
+// see https://datatracker.ietf.org/doc/html/rfc4648#section-5
+const base64toBase64Url = str => str.replaceAll('+', '-').replaceAll('/', '_').replaceAll('=', '');
+
 async function fixture() {
   const mock = await ethers.deployContract('$Base64');
   return { mock };
@@ -12,18 +16,35 @@ describe('Strings', function () {
     Object.assign(this, await loadFixture(fixture));
   });
 
-  describe('from bytes - base64', function () {
+  describe('base64', function () {
     for (const { title, input, expected } of [
       { title: 'converts to base64 encoded string with double padding', input: 'test', expected: 'dGVzdA==' },
       { title: 'converts to base64 encoded string with single padding', input: 'test1', expected: 'dGVzdDE=' },
       { title: 'converts to base64 encoded string without padding', input: 'test12', expected: 'dGVzdDEy' },
-      { title: 'empty bytes', input: '0x', expected: '' },
+      { title: 'converts to base64 encoded string (/ case)', input: 'où', expected: 'b/k=' },
+      { title: 'converts to base64 encoded string (+ case)', input: 'zs~1t8', expected: 'enN+MXQ4' },
+      { title: 'empty bytes', input: '', expected: '' },
     ])
       it(title, async function () {
-        const raw = ethers.isBytesLike(input) ? input : ethers.toUtf8Bytes(input);
+        const buffer = Buffer.from(input, 'ascii');
+        expect(await this.mock.$encode(buffer)).to.equal(ethers.encodeBase64(buffer));
+        expect(await this.mock.$encode(buffer)).to.equal(expected);
+      });
+  });
 
-        expect(await this.mock.$encode(raw)).to.equal(ethers.encodeBase64(raw));
-        expect(await this.mock.$encode(raw)).to.equal(expected);
+  describe('base64url', function () {
+    for (const { title, input, expected } of [
+      { title: 'converts to base64url encoded string with double padding', input: 'test', expected: 'dGVzdA' },
+      { title: 'converts to base64url encoded string with single padding', input: 'test1', expected: 'dGVzdDE' },
+      { title: 'converts to base64url encoded string without padding', input: 'test12', expected: 'dGVzdDEy' },
+      { title: 'converts to base64url encoded string (_ case)', input: 'où', expected: 'b_k' },
+      { title: 'converts to base64url encoded string (- case)', input: 'zs~1t8', expected: 'enN-MXQ4' },
+      { title: 'empty bytes', input: '', expected: '' },
+    ])
+      it(title, async function () {
+        const buffer = Buffer.from(input, 'ascii');
+        expect(await this.mock.$encodeURL(buffer)).to.equal(base64toBase64Url(ethers.encodeBase64(buffer)));
+        expect(await this.mock.$encodeURL(buffer)).to.equal(expected);
       });
   });
 });