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FAQ on the xz-utils backdoor

Background

On March 29th, 2024, a backdoor was discovered in xz-utils, a suite of software that gives developers lossless compression. This package is commonly used for compressing release tarballs, software packages, kernel images, and initramfs images. It is very widely distributed, statistically your average Linux or macOS system will have it installed for

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ELF Format Cheatsheet

Introduction

Executable and Linkable Format (ELF), is the default binary format on Linux-based systems.

Compilation

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###################################################################
          Writing C software without the standard library
                           Linux Edition
###################################################################
There are many tutorials on the web that explain how to build a
simple hello world in C without the libc on AMD64, but most of them
stop there.

I will provide a more complete explanation that will allow you to
build yourself a little framework to write more complex programs.

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	float ph =  234.4;
	float temp =  22.2;
	printf("\n\ntemp: %f\nph: %f\n", temp, ph);

	char buffer[200] ;
	sprintf(buffer, "Temperature: %.2f \nPH: %f", temp, ph);
	printf("%s\n", buffer);

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  onPress = () => {
    return fetch("http://www.agis-mapp.xyz/doctors", {
      method: "POST",
      headers: {
        Accept: "application/json",
        "Content-Type": "application/json"
      },
      body: JSON.stringify({
        email: this.state.email,
        password: this.state.password,

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# NOTE:
# keylength is the number of bytes in that key
# pad is xor'ed on character parts
def  get_pad(key, message_length):
    keylength = len(key)
    pad = [None] * message_length
    s = []
    #-- key-scheduling algorithm: initialize the s array
    for i in range(256):
        s.append(i)

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from p5 import *
import math  

triangle_center_x = 80
triangle_center_y = 60
diameter = 80

bottom_arc = 0
right_arc = 1
left_arc = 2

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def setPixel(x, y):
    print("x is {x}, y is {y}. ".format(x = x, y = y))

def draw_circle(centre_x, centre_y, radius):
    offset_y = 0
    offset_x = radius
    crit = 1 - radius
    while offset_y <= offset_x:
        print("crit is {c}, off_x is {x}, off_y is {y}. ".format(x = offset_x, y = offset_y, c = crit))