It sorts dictionary entries incorrectly.

[issuefiler]

Bug

bencode-js/src/encode.coffee

Lines 9 to 10 in 3ca25e4

	encodeDictionary = (object) ->
	keys = (key for own key of object).sort()

   keys = (key for own key of object).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, polluting 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