knock を Homebrew, apk, dnf, MacPorts, zypper, apt, pacman でインストール

プロジェクトリンク

• ホームページ
• 上流ドキュメント
• パッケージマネージャページ

コマンドとエイリアス

• knock
• knock_helper_ipt.sh
• knockd

プロジェクトの歴史

The README carries a 2004 copyright notice and describes the core design that still defines the package: closed ports can receive a secret sequence because knockd sniffs link-layer traffic rather than listening on those ports. The bundled ChangeLog lists 0.1 as the initial release and shows later work adding TCP flag handling, reload behavior, timeouts, kernel-space BPF filtering, one-time sequences, interface selection, and IPv6 support.

Version 0.8 was published on 2021-04-24 with multiple fixes and IPv6 support. The GitHub repository retained a small C codebase, an example `knockd.conf`, and manpage documentation rather than growing into a larger access-control framework.

採用の歴史

knock spread through Unix-like distributions because it solved a specific sysadmin problem with a small daemon and client. Package names vary between `knock`, `knockd`, and distribution-specific formula names, but the underlying model stayed close to the original README example: a knock sequence opens SSH, and another sequence closes it.

使われ方

A server runs `knockd` with a configuration file such as `/etc/knockd.conf`; a client runs `knock` to send TCP or UDP packets to the configured sequence. Commands usually add or remove firewall rules, so the tool is operationally simple but security-sensitive: the sequence should be treated like a shared secret and firewall commands must be written carefully.

パッケージ好きにとっての重要性

knock is a memorable package because it embodies a whole security pattern in a tiny Unix daemon. It is also a reminder of the early-2000s sysadmin style: libpcap, iptables commands, config files, and a tiny client were enough to make a practical layer around SSH exposure.

タイムライン

• 2004: README copyright identifies Judd Vinet's original project era.
• 0.1: ChangeLog records the initial release.
• 0.3: ChangeLog added PPP support, command timeout directives, SIGHUP config reloads, and per-port protocols.
• 0.5: ChangeLog added one-time sequences, interface selection, BPF filtering, and security fixes.
• 0.7: ChangeLog documented the target directive and consolidated OS-specific networking code.
• 2021-04-24: v0.8 release published with fixes and IPv6 support.

Related projects

• knock is related to other port-knocking and single-packet-authorization tools, firewall managers such as iptables, packet crafting tools such as sendip, and SSH hardening workflows.

ソース

• https://github.com/jvinet/knock
• https://github.com/jvinet/knock/blob/master/ChangeLog
• https://github.com/jvinet/knock/releases/tag/v0.8
• https://raw.githubusercontent.com/jvinet/knock/master/knockd.conf