kennytv

Signed chat

This gist intends on clearing up some of the misinformation surrounding signed chat/the reporting feature Mojang has added to Minecraft 1.19.1. Here you can find both technical information as well as a general explanation of how these work.

Profile keys

After joining a server, clients now send a profile key used for verifying a message's authenticity. This key and thus the whole signing process is optional, but by default, servers enforce secure profiles for clients to send chat messages. Whenever the player sends a chat message and has a key associated, the message will be signed using their own private key, which the server then verifies using the public key sent after join. Assuming signature, timestamp, and message contents line up, the message goes through.

On the other end, clients can also require all broadcasted player messages to be signed, disregarding the ones without sender verified signatures.

Message signatures

misuzu

Install NixOS on Oracle Cloud over Ubuntu 18.04 (make sure to use Ubuntu 18.04 or this may not work)

# install useful tools
sudo apt-get update
sudo apt-get install --no-install-recommends -y nano mc git

# prepare /boot
sudo umount /boot/efi
sudo mv /boot /boot.bak

mcastelino

The netfilter hooks in the kernel and where they hook in the packet flow

The figure below calls out

• The netfilter hooks
• The order of table traversal

klzgrad

朴素VPN：一个纯内核级静态隧道

由于路由管控系统的建立，实时动态黑洞路由已成为最有效的封锁手段，TCP连接重置和DNS污染成为次要手段，利用漏洞的穿墙方法已不再具有普遍意义。对此应对方法是多样化协议的VPN来抵抗识别。这里介绍一种太简单、有时很朴素的“穷人VPN”。

朴素VPN只需要一次内核配置（Linux内核），即可永久稳定运行，不需要任何用户态守护进程。所有流量转换和加密全部由内核完成，原生性能，开销几乎没有。静态配置，避免动态握手和参数协商产生指纹特征导致被识别。并且支持NAT，移动的内网用户可以使用此方法。支持广泛，基于L2TPv3标准，Linux内核3.2+都有支持，其他操作系统原则上也能支持。但有两个局限：需要root权限；一个隧道只支持一个用户。

朴素VPN利用UDP封装的静态L2TP隧道实现VPN，内核XFRM实现静态IPsec。实际上IP-in-IP隧道即可实现VPN，但是这种协议无法穿越NAT，因此必须利用UDP封装。内核3.18将支持Foo-over-UDP，在UDP里面直接封装IP，与静态的L2TP-over-UDP很类似。

创建一个朴素VPN