User:Saul

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Revision as of 22:17, 23 September 2024 by Saul (talk | contribs) (→‎Node Fetch and Ipv6: Add global setting.)

This page contains my notes and documentation of various technologies, mostly related to the tech stack I use.

Useful Links In This Wiki

My Crypto Links In This Wiki

My Troubleshooting Pages

Cool Projects

Snippets:

BASH:

Copy File To Server

To copy a file from or to a server over ssh run: 

# scp SOURCE DESTINATION
scp -r USER@IP:~/SOME_FOLDER ~/SOME_FOLDER

VPS Proxy

To proxy traffic over port 1080 run: 

ssh -NCD 1080 user@ip

Then in Firefox go: Edit -> Preferences -> General -> Network Proxy (near the bottom) and modify the following settings: 

Manual Proxy Configuration
Socks Host: localhost
port: 1080

Alias

To save a command run: 

alias COMMANDNAME="COMMAND"

This will be lost on reboot however so to save it run: 

echo "alias COMMANDNAME=\"COMMAND\";" >> ~/.bash_aliases # OR directly into the rc file (~/.bashrc)

Random Password Generation

A useful command to generate a random password of 10 characters: 

</dev/urandom tr -dc 'A-Za-z0-9!#$%&()*+,-./:;<=>?@[\]^_`{|}~' | head -c 10 ; echo

Or even better use this.

SSH Tunnel

A SSH tunnel can allow you to make queries on a local machine and have them tunneled onto a remote machine. 

# Open tunnel
ssh -M -\
	S ~/tunnel-file \
	-o "ExitOnForwardFailure yes" \
	-fN root@example.com \
	-L 4040:localhost:4040

# Listen to port
nc -lv localhost \
	-p 4040

# send data on port
cat < /dev/urandom > /dev/tcp/localhost/4040

Block Non-VPN Network Activity

# Name of VPN network adapter
VPN_IF=tun0

VPN_SERVER=1.2.3.4
VPN_PORT=1194

# Reset the IP Tables
sudo iptables -F

# Allow inbound connections related to things you initiate on any interface
sudo iptables -A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
# Allow loopback
sudo iptables -A INPUT -i lo -j ACCEPT
sudo iptables -A OUTPUT -o lo -j ACCEPT
# Allow all out to VPN
sudo iptables -A OUTPUT -o $VPN_IF -j ACCEPT
# Assuming UDP
sudo iptables -A OUTPUT -p udp --dport $VPN_PORT -d $VPN_SERVER -j ACCEPT
# Allow DHCP
sudo iptables -A OUTPUT -p udp --dport 67 -j ACCEPT
sudo iptables -A INPUT -p udp --dport 68 -j ACCEPT
# Default drop the rest
sudo iptables -A INPUT -j DROP
sudo iptables -A OUTPUT -j DROP

To reset: 

sudo iptables -F

Archiving

Parameters:

  • -f Specify file
  • -v Verbose
  • -z Use gzip
  • -c Compress
  • -x Extract
# Compress (GZIP)
tar -czvf <ARCHIVE NAME>.tar.gz <DIRECTORY TO ARCHIVE>

# Decompress (GZIP)
tar -xzvf <ARCHIVE NAME>.tar.gz -C <DIRECTORY TO Extract To>

# LZ4 Install
apt-get install liblz4-tool

# Compress (LZ4)
tar -cvf - <DIRECTORY TO ARCHIVE> | lz4 - <ARCHIVE NAME>.tar.lz4

# Decompress (LZ4)
lz4 -c -d <ARCHIVE NAME>.tar.lz4 | tar -xvfC <DIRECTORY TO Extract To>
tar --use-compress-program=lz4 -xvf <ARCHIVE NAME>.tar.lz4 -C <DIRECTORY TO Extract To> # Alternative

Open Encrypted Home Folders

To mount an encrypted home directory you will need to run the following commands: 

sudo su;
mkdir /mnt/home;
ecryptfs-unwrap-passphrase /media/mint/UUID/home/.ecryptfs/USER/.ecryptfs/wrapped-passphrase; # Replace 'UUID' and 'USER'

# The last command will output a string, copy it somewhere for later.

sudo ecryptfs-add-passphrase --fnek # Input the string from the last command

# This will provide 2 sig outputs copy the last one somewhere for later. (it looks like a hash and is in between square brackets).

mount -t ecryptfs /media/mint/UUID/home/.ecryptfs/USER/.Private /mnt/home; # Replace 'UUID' and 'USER'
# 1. Choose opt. #1 'passphrase' and input the passphrase you copied earlier.
# 2. Choose 'aes' (default)
# 3. Choose '16' (default) for key bytes.
# 4. Choose 'no' (default) for Enable plaintext passthrough
# 5. Choose 'yes' for Enable filename encryption
# 6. Input the sig output you copied earlier.

The home directory should now be mounted at /mnt/home

Joining mp3s

sudo apt-get install mp3wrap
mp3wrap output.mp3 *.mp3

There is also mp3split for splitting mp3s

Fix mp3 Meta

mp3val damaged.mp3 -f

LVM Resize Disk

Display volume group data: 

vgdisplay

Get the value under LV Path. 

sudo lvextend -L+500GB <LV_PATH>

Then you need to resize the filesystem: 

sudo resize2fs <LV_PATH>

CSS:

Sticky Footer

body .site{
	display: flex !important;
	min-height: 100vh !important;
	flex-direction: column !important;
}

#content {
	flex: 1 !important;
}

Note: in Wordpress the user bar will make the page need to scroll so logout to see it properly.

Hide ReCaptcha

body:not(.page-id-16) .grecaptcha-badge {
    display: none;
}

Same Height Columns:

.Container{
	display: flex;
}

.Column{
	flex: 1; /* optional to equalize widths */
}

Javascript

Git Web Hooks

const http = require("http");
const crypto = require("crypto");
const exec = require("child_process").exec;

const repo = "<DIRECTORY OF YOUR REPO>";
const secret = "<YOUR SECRET>";

http.createServer((req, res) => {
	req.on("data", chunk => {
		try {
			const body = JSON.parse(chunk.toString());

			// Github
			const sig = "sha1=" + crypto.createHmac("sha1", secret).update(chunk.toString()).digest("hex");

			// Gitea
			//const sig = crypto.createHmac("sha256", secret).update(chunk.toString()).digest("hex");

			const isMaster = body?.ref === "refs/heads/master";

			// Gitea needs "x-gitea-signature"
			if (req.headers["x-hub-signature"] == sig && isMaster) {
				if (isMaster)
					exec(`cd ${repo} && git pull`);

				res.writeHead(200);
				res.end("Success!");
			} else {
				console.error("Failed verification.");
				res.writeHead(403);
				res.end("Failed verification.");
			}
		} catch (e) {
			console.error(e);
			res.writeHead(403);
			res.end(`Somthing went wrong.`);
		}
	});
}).listen(8080);

Add it as a service: /etc/systemd/system/webhook.service 

[Unit]
Description=Git webhook
After=network.target

[Service]
Environment=NODE_PORT=8080
Type=simple
User=root
ExecStart=/usr/bin/nodejs <WEBHOOK DIRECTORY>
Restart=on-failure

[Install]
WantedBy=multi-user.target

Higher Order Functions

Higher order functions are functions that accept or return a function. These are useful of abstracting and reducing your code.

// ES6+
const fetchResource = (resource, id) => fetch(`api/${resource}/${id}`);

const makeFetcher = resource => id => fetchResource(resource, id);

const fetchUser = makeFetcher("users");
const fetchGroup = makeFetcher("group");

const user = fetchUser("123");
const group = fetchGroup("10");

// ES5
function fetchResource (resource, id) {
	return fetch("api/" + resource + "/" + id);
}

function makeFetcher (resource) {
	return function (id) {
		fetchResource(resource, id);
	};
}

function fetchUser () {
	return makeFetcher("users");
}

function fetchGroup () {
	return makeFetcher("group");
}

var user = fetchUser("123");
var group = fetchGroup("10");

This example helps show how higher order functions can be useful. If the api location changes you only need to change one function to get your code working again.
The fetchResource function is just a simple function that calls the fetch function with its parameters. The makeFetcher is a closure function that returns another function that calls our first, therefore when make fetcher gets called it returns a function that only needs the id due to the resource being saved due to the first function acting a a closure. Then you can quickly make your fethcUser, fetchGroup functions and so on.

Unpacking Objects And Arrays

Arrays can be unpacked into a variables list like this example: 

let list = ["apples", "bananas", "carrots", "pears", "corn"];

let [itemOne, itemTwo, ItemThree, ItemFour] = list;

console.log(itemOne); // Output: "apples"
console.log(itemThree); // Output: "carrots"

You can use this syntax to switch the variables too! 

[itemOne, itemTwo] = [itemTwo, itemOne];

console.log(itemOne); // Output: "bananas"

Objects can be unpacked using similar syntax: 

let person = {
	name: "sam",
	height: 2,
	food: "pizza"
}

{name, height, food} = person;

console.log(name); // Output: "sam"
console.log(food); // Output: "pizza"

({height, food, name}) = person;

console.log(name); // Output: "sam"
console.log(height); // Output: 2

Note that the variable names must match the object properties, if you want different names you can do it like this: 

({name: n}) = person;

console.log(n); // Output: "sam"

Using this syntax you can also set default values for properties like so: 

({name: n, pet: favouriteAnimal = "dragon"}) = person;

Node Fetch and Ipv6

Node's fetch can sometimes fail due to IPv6 selection failing and it only gives a timeout error. 

// Fix package 'node-fetch'
import http, { Agent } from 'https'

http.globalAgent = new Agent({ family: 4 })
// Fix default node fetch implementation (undici)
import undici, { fetch, Agent } from 'undici'

const agent = new Agent({
  autoSelectFamily: true,
  autoSelectFamilyAttemptTimeout: 1000
})

// Per fetch call:
await fetch('your url here', {
  dispatcher: agent
})

// Globally:
undici.setGlobalDispatcher(agent)

C

Printing the raw bits of a variable: 

// Change "unsigned char" to the type you would like to inspect.
void printbits (unsigned char v) {
	int i;
	for(i = sizeof(v) * 8 - 1; i >= 0; i--) putchar('0' + ((v >> i) & 1));
}
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