It sorts dictionary entries incorrectly.

[issuefiler]

Bug

bncode/bncode.js

Lines 370 to 372 in 704e8d5

	function encodeDict (obj) {
	var func = function (obj, pos) {
	var keys = Object.keys(obj).sort()

     var keys = Object.keys(obj).sort()

This is not the correct way of sorting dictionary entries. The encoder is producing specification-incompliant octets that’ll be floating around in the wild, the network.

---

When you say “strings” in the context of Bencoding, you mean “binary strings,” or more specifically, “8-bit byte sequences.”

BEP 52 — The BitTorrent protocol specification version 2

Note that, in the context of bencoding, strings, including dictionary keys, are arbitrary byte sequences (uint8_t[]).

And Array.prototype.sort compares 16-bit units by default.

If compareFn is not supplied, all non-undefined array elements are sorted by converting them to strings and comparing strings in UTF-16 code units order.

The simple .sort() results in a different order (sorted_in_utf16) than the correct one (sorted_in_utf8). Observe:

const A = String.fromCodePoint(0xFF61);
const B = String.fromCodePoint(0x10002);
const sorted_in_utf8 = [A, B].sort((a, b) => Buffer.compare(Buffer.from(a), Buffer.from(b))); // [A, B]
const sorted_in_utf16 = [A, B].sort(); // [B, A]

The related issue

• It sorts dictionary entries incorrectly. webtorrent/node-bencode#142