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Net-BitTorrent-v2.1.0
⭐ Starred 13 / Net::BitTorrent::Torrent::Generator
Security Advisories (2)
CVE-2026-57080 (2026-06-30)

Net::BitTorrent versions through 2.1.0 for Perl allow remote memory exhaustion via an uncapped peer-wire message-length prefix. The peer-wire framing in _process_messages trusts the 4-byte length prefix sent by a connected peer with no upper bound, while receive_data appends every inbound byte to the input buffer. A peer announces a length prefix of up to about 4 GiB and then streams bytes; the decoder waits until the buffer holds the full message before processing it, so the buffer grows without limit. Peer connections are unauthenticated, so any peer in the swarm exhausts the downloading process's memory. The largest legitimate message is a 16 KiB piece block, so any announced length far above that is anomalous.

CVE-2026-57081 (2026-06-30)

Net::BitTorrent versions through 2.1.0 for Perl allow remote memory exhaustion via deeply nested bencoded input. bdecode recurses once per nested list or dictionary level with no depth cap, and each recursive call receives the remaining buffer by value while the list and dictionary branches capture the whole remainder, so every live recursion frame keeps its own copy of the shrinking buffer (O(N^2) bytes for an N-deep input). The decoder runs on every untrusted bencode source: .torrent files, BEP09 metadata fetched from peers, DHT messages, and tracker responses. A bencoded input of roughly 150,000 nested lists (about 150 KB on the wire) drives multi-gigabyte peak memory, so one short message from any peer, or one crafted .torrent file or magnet link, terminates the client.

NAME

Net::BitTorrent::Torrent::Generator - .torrent File Generator

SYNOPSIS

use Net::BitTorrent::Torrent::Generator;

my $gen = Net::BitTorrent::Torrent::Generator->new(
    base_path    => './my_files',
    piece_length => 262144 # 256KiB
);

# Add files to the torrent
$gen->add_file( 'linux-distro.iso' );
$gen->add_file( 'README.txt' );

# Add metadata
$gen->add_tracker( 'https://tracker.example.com/announce' );
$gen->add_node( 'router.bittorrent.com' , 6881);

# Generate the .torrent file data (bencoded)
my $v1_data     = $gen->generate_v1( );
my $v2_data     = $gen->generate_v2( );
my $hybrid_data = $gen->generate_hybrid( );

path('my_project.torrent')->spew_raw( $hybrid_data );

DESCRIPTION

Net::BitTorrent::Torrent::Generator allows you to programmatically create BitTorrent metadata files (.torrent). It supports the latest BEP 52 standards for BitTorrent v2 and hybrid swarms.

METHODS

new( %params )

Creates a new Generator object.

my $gen = Net::BitTorrent::Torrent::Generator->new(
    base_path => './data'
);

Expected parameters:

base_path

The root directory containing the files to be included in the torrent.

piece_length - optional

The size of each piece in bytes. Defaults to 262144 (256KiB).

add_file( $rel_path )

Adds a file from the base_path to the metainfo.

$gen->add_file( 'data/movie.mp4' );

If set_align_files( 1 ) has been called, this will automatically insert padding files (BEP 47) to ensure files start on piece boundaries, which is highly recommended for hybrid torrents.

Expected parameters:

$rel_path

The relative path to the file from the base path.

add_tracker( $url )

Adds a tracker URL.

$gen->add_tracker( 'udp://tracker.openbittorrent.com:80/announce' );

Expected parameters:

$url

The tracker announce URL.

add_node( $host, $port )

Adds a DHT bootstrap node.

$gen->add_node( 'router.bittorrent.com', 6881 );

Expected parameters:

$host

The hostname or IP.

$port

The port number.

set_private( $val )

Sets the private flag.

$gen->set_private( 1 );

If true, a client will only use trackers and will not enable DHT or PEX for this swarm.

Expected parameters:

$val

Boolean.

set_align_files( $val )

Sets whether to align files to piece boundaries (v2/hybrid).

$gen->set_align_files( 1 );

If true, ensures every file starts at the beginning of a piece by adding zero-filled padding files. This optimizes performance and allows for better cross-swarm deduplication.

Expected parameters:

$val

Boolean.

generate_v1( )

Generates a BitTorrent v1 .torrent file using SHA-1 piece hashes. Compatible with all clients.

my $raw = $gen->generate_v1();

generate_v2( )

Generates a BitTorrent v2 .torrent file. Uses SHA-256 and Merkle trees. Only compatible with v2-aware clients (Net::BitTorrent, libtorrent, etc.).

my $raw = $gen->generate_v2();

generate_hybrid( )

Generates a torrent containing both v1 and v2 metadata. This allows v1-only clients to participate in the same swarm as v2 clients. Recommended for maximum compatibility.

my $raw = $gen->generate_hybrid();

AUTHOR

Sanko Robinson - https://github.com/sanko

COPYRIGHT

Copyright (C) 2008-2026 by Sanko Robinson.

This library is free software; you can redistribute it and/or modify it under the terms of the Artistic License 2.0.