Fix 2063 (#2079)

src/base64/base64.zig

@@ -49,8 +49,9 @@ pub fn decodeLenUpperBound(len: usize) usize {
 
 pub fn decodeLen(source: anytype) usize {
     return zig_base64.standard.Decoder.calcSizeForSlice(source) catch {
-        //fallback
-        return source.len / 4 * 3;
+
+        //fallback; add 2 to allow for potentially missing padding
+        return source.len / 4 * 3 + 2;
     };
 }
 

test/bun.js/buffer.test.js

@@ -2550,3 +2550,11 @@ it("should not perform out-of-bound access on invalid UTF-8 byte sequence", () =
   expect(str.length).toBe(6);
   expect(str).toBe("\uFFFD\x13\x12\x11\x10\x09");
 });
+
+it("repro #2063", () => {
+  const buf = Buffer.from("eyJlbWFpbCI6Ijg3MTg4NDYxN0BxcS5jb20iLCJpZCI6OCwicm9sZSI6Im5vcm1hbCIsImlhdCI6MTY3NjI4NDQyMSwiZXhwIjoxNjc2ODg5MjIxfQ", 'base64');
+  expect(buf.length).toBe(85);
+  expect(buf[82]).toBe(50);
+  expect(buf[83]).toBe(49);
+  expect(buf[84]).toBe(125);
+});