It sorts dictionary entries incorrectly.

[issuefiler]

Bug

https://github.com/a2800276/bncode/blob/704e8d5ddd4f9257d4e787191d2cc7c7ed76ad98/bncode.js#L370-L372

     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.

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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

• https://github.com/webtorrent/node-bencode/issues/142