Meetups/Infra/2025-05-19

Started a developer off on Telegram and Notion API use, discussed binary analysis, system call inspection, dynamic library inspection, internet-networking ASes, BGP.

Introductions

• [name] - [background]. [goals for meetup, or interests to explore]

• Loren -- Wants to set up a server for meetup chat
• Daniel -- not supposed to be here
• Zacchae -- other than phone number, I only use services I succeed in self-hosting
• [a person]
• Chris -- good front-end developer -- current interests:
• Sai (sp) -- backend eng, stumbling into the meetup
• Thereesa -- (2nd time)
• Nick -- interested in self-hosting (challenge: ask 2 questions)
• Dianna -- here - interested in infrastructure
• Greg -- interested in FOSS broadly, not working onanything today
• Mike - unemployed software engineer. Working on setting up services on my home k8s cluster.
• Doug -- terrible front- and back-end engineer -- here to chrome cast

(free ross)

Lesson or Demo

• Read aloud: clarify for meetup. We are taking notes in a riseup pad (or I am--help appreciated, and links). We have meeting notes posted to the wiki. noisebridge.net, search Infra, or Meetups/Infra. (the Infrastructure page has a disambiguation link.)
• Shell, web services, self-hosting, networking!

• platform questions -- full-stack development & use of platforms: Notion. Telegram.
  • telegram -- concerns
    • *lying* about their cryptography --

possibility of commercialization -

https://core.telegram.org/bots/api https://developers.notion.com/

• binary inspection

https://binsider.dev/ - rust + rataTUI https://github.com/ReFirmLabs/binwalk https://binvis.io/ https://github.com/sharkdp/hexyl rabin2 -I binary

1. 1. List information about binary

```shell $ rabin2 -I binary arch arm baddr 0x100000000 binsz 33512 bintype mach0 bits 64 canary false injprot false class MACH064 compiler clang [...] ```

• • dyld Cheatsheet**

========

1. 1. 1. Introduction

• `dyld` stands for "dynamic linker" or "dynamic link editor"
• Responsible for loading and linking dynamic libraries into running processes

1. 1. 1. Key Functions

• Loads dynamic libraries into memory
• Resolves symbol references between executables and libraries
• Performs relocations to adjust memory addresses
• Handles library dependencies

1. 1. 1. Benefits

• **Memory efficiency**: Shares dynamic libraries among multiple processes
• **Improved performance**: Loads libraries dynamically to reduce startup times
• **Simplified software development**: Enables independent updates of libraries and executables

1. 1. 1. Useful Commands

• `otool -L <executable>`: Inspect dynamic libraries used by an executable

   + Example: `otool -L /bin/ls`

• `dylib`: Work with dynamic libraries directly

   + Example: `dylib /usr/lib/libSystem.B.dylib`

1. 1. 1. Examples

Inspecting Dynamic Libraries ```bash $ otool -L /bin/ls /bin/ls:

   /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1234.0.0)
   /usr/lib/libc.dylib (compatibility version 1.0.0, current version 1234.0.0)

``` Working with Dynamic Libraries ```bash $ dylib /usr/lib/libSystem.B.dylib ```

otool -L /bin/ls

/bin/ls:

   /usr/lib/libutil.dylib (compatibility version 1.0.0, current version 1.0.0)
   /usr/lib/libncurses.5.4.dylib (compatibility version 5.4.0, current version 5.4.0)
   /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1351.0.0)

btop (htop, top, iotop), xxd (od),

mtr, traceroute, hping3

1. `hping3` - Advanced ping utility which supports protocols such TCP, UDP, and raw IP.

https://www.kali.org/tools/hping3/

1. 1. Ping an IP address over UDP on port 80

```sh hping3 --udp --destport 80 --syn ip_or_hostname ```

1. 1. Scan TCP port 80, scanning from the specific local source port 5090:

```sh hping3 --verbose --syn --destport 80 --baseport 5090 ip_or_hostname ```

IP addresses are assigned to:

• AS / ASNs (AS Number) https://en-wp.org/wiki/Autonomous_system_(Internet)

Much as domain names are leased to individuals to allow lookup of IP addreseses for servers, where poeple host the services they want to provide.

• loading executables

ldd -- macos dyld / dyld_info https://jmmv.dev/2023/07/ldd-untrusted-binaries.html

torsocks (macOS vs linux -- use different dynamic linkers)

strace -- statx / openat

1. List of tools to demonstrate practical uses of tools (Quick Reference Guides)

cht.sh -- hping https://cht.sh TLDR: https://tldr.sh/tlrc/ -

• dynamic linking

• security cryptography whatever

https://securitycryptographywhatever.com/episodes/

takeaways

• Doug -- more cht.sh
• Mike -- (silently) 5th amendment rights assertion. ebpf
• Greg -- cht.sh cool, would: live code nix
• Dianna -- tldr --
• Nick -- ASNs -- all the tools -- curious about self-hosting, curious about security
• Theresa -- binary analsis -- , cht.sh, TeleGram
• Jams -- lots of interesting thing
• Chris -- how IP addresses work
• -- binvis stuff
• Zacchae -- let's do a project uuuhhh. ideas for what you want. informational (want to: do more actual building.)

• • system crafters

Questions, Discussion, or Coworking

• [Issue]

For next time

Readings & Exercises

• Readings
• Exercises

Join online

• Try it yourself!
  • Join libera.chat #nb-meetup-infra

https://www.noisebridge.net/wiki/Meetups/Infra