1 files changed, 47 insertions, 0 deletions
diff --git a/ext/node/polyfills/_crypto/crypto_browserify/randombytes.ts b/ext/node/polyfills/_crypto/crypto_browserify/randombytes.ts
new file mode 100644
index 000000000..d70ada282
--- /dev/null
+++ b/ext/node/polyfills/_crypto/crypto_browserify/randombytes.ts
@@ -0,0 +1,47 @@
+// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
+// Copyright 2017 crypto-browserify. All rights reserved. MIT license.
+import { Buffer } from "internal:deno_node/polyfills/buffer.ts";
+import { nextTick } from "internal:deno_node/polyfills/_next_tick.ts";
+
+// limit of Crypto.getRandomValues()
+// https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues
+const MAX_BYTES = 65536;
+
+// Node supports requesting up to this number of bytes
+// https://github.com/nodejs/node/blob/master/lib/internal/crypto/random.js#L48
+const MAX_UINT32 = 4294967295;
+
+export function randomBytes(
+  size: number,
+  cb?: (err: Error | null, b: Buffer) => void,
+) {
+  // phantomjs needs to throw
+  if (size > MAX_UINT32) {
+    throw new RangeError("requested too many random bytes");
+  }
+
+  const bytes = Buffer.allocUnsafe(size);
+
+  if (size > 0) { // getRandomValues fails on IE if size == 0
+    if (size > MAX_BYTES) { // this is the max bytes crypto.getRandomValues
+      // can do at once see https://developer.mozilla.org/en-US/docs/Web/API/window.crypto.getRandomValues
+      for (let generated = 0; generated < size; generated += MAX_BYTES) {
+        // buffer.slice automatically checks if the end is past the end of
+        // the buffer so we don't have to here
+        globalThis.crypto.getRandomValues(
+          bytes.slice(generated, generated + MAX_BYTES),
+        );
+      }
+    } else {
+      globalThis.crypto.getRandomValues(bytes);
+    }
+  }
+
+  if (typeof cb === "function") {
+    return nextTick(function () {
+      cb(null, bytes);
+    });
+  }
+
+  return bytes;
+}