hashbrowncipher

The %util column in iostat has always been something of a weird bird. It was created back in the day when hard disks could only effectively process a single request at once. Back then, if %util was 100, then the disk was completely saturated and could go no faster. Modern block devices have the ability to perform multiple operations concurrently, and so %util's usefulness has ebbed. The manpage gives a clear warning about the meaning (or lack thereof) of %util, describing it as:

Percentage of elapsed time during which I/O requests were issued to the device (bandwidth utilization for the device). Device saturation occurs when this value is close to 100% for devices serving requests serially. But for devices serving requests in parallel, such as RAID arrays and modern SSDs, this number does not reflect their performance limits.

hashbrowncipher

//Invoke like `./bin <frequency in Hz (e.g. 100)> <filename to read>`

#define _GNU_SOURCE
#include <fcntl.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

hashbrowncipher

#!/usr/bin/env python3
"""Cross platform, rootless, and fast debootstrap.

Designed to work anywhere you can run Python and Docker/Podman (e.g. a Mac laptop).

* Tested only with Ubuntu Focal and Jammy
* Right now LZMA decoding takes up most of the time. Parallelize it? Python's LZMA
  library does release the GIL.

"""

hashbrowncipher

#!/bin/bash
# Copyright 2021 Josh Snyder
# See license and documentation in lambda_function.py
set -x -o errexit -o nounset

ebs_name() { 
  nvme id-ctrl -o binary $1  | cut -c3073-3104 | tr -d ' '
}

export AWS_DEFAULT_REGION=$AWS_REGION  

hashbrowncipher

Scientific American
May 1973
Volume 228
Number 5

Cryptography and Computer Privacy
by Horst Fiestel

Computer systems in general and personal "data banks" in particular
need protection. This can be achieved by enciphering all material and authenticating

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/*
 * A little x86-64 loader for Linux's binfmt_misc.
 *
 * Compile with: gcc -O3 -static -nostdlib -o loader loader.c
 *
 * Register as:
 *   mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
 *   echo ':amd64:E::amd64::/path/to/loader:O' > /proc/sys/fs/binfmt_misc/register
 *
 * Then just run your favorite shellcode. Sample:

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Moving from running to port closed took: 3.147979 s
Moving from port closed to port open took: 0.000000 s
Moving from running to port closed took: 2.366330 s
Moving from port closed to port open took: 0.000000 s
Moving from running to port closed took: 2.998677 s
Moving from port closed to port open took: 0.000000 s
Moving from running to port closed took: 2.605815 s
Moving from port closed to port open took: 0.024404 s
Moving from running to port closed took: 2.754971 s
Moving from port closed to port open took: 0.009866 s

hashbrowncipher

- this uses a squashfs root image with a writable overlay
- only a single application service is running (sshd)
- the instance was a c5.large that had already booted once

hashbrowncipher

- This run was on a c5.large which had been booted up before
- Set MODULES=dep in /etc/initramfs-tools/initramfs.conf
- Deleted a bunch of initramfs-tools hooks, including especially: iscsi mdadm lvm2
- Removed a bunch of stock ubuntu services
  * snapd
  * ec2-instance-connect
  * cryptsetup-initramfs
  * udisks2
  * unattended-upgrades
  * plymouth

hashbrowncipher

josh@ubuntu:~/hasher$ dd if=/dev/zero bs=65536 count=16384 | ./xxHash/xxh128sum 
16384+0 records in
16384+0 records out
16024760318c6298efd1151033ad2e9f  stdin
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.23966 s, 4.5 GB/s
josh@ubuntu:~/hasher$ dd if=/dev/zero bs=65536 count=16384 | ./a.out 
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.210685 s, 5.1 GB/s
16024760318c6298efd1151033ad2e9f