Tech Talk

ssh-agent

Mon 27 November 2017 by Stephen Bourke

ssh-agent

What is it?

  • A separate program that loads your keys and passes them to ssh
  • ssh will see if ssh-agent is running and if so will ask it for your keys

What's the point?

  • To decrypt your keys temporarily
  • Stores them in RAM, not on disk
  • Time out can be set so keys are forgotten after some time

Why use it?

Good news!

  • You probably already are :-)
  • You don’t have to do or configure anything
  • There’s no reason not to

Unencrypted keys

  • What’s the issue with unencrypted keys?
  • Lots of people have access to your keys
    • Lots of admins
    • Unintentional sharing
    • Abandoned data

Encrypting your keys

  • It’s done by default
  • Can be done later:
ssh-keygen -p -f keyfile

.ssh/config

Host *
   ForwardAgent yes
  • No need for private keys on remote machines
ssh-add -l

Ports

  • Internet network protocol suite (TCP/IP)
  • Controlled by Operating System
  • socket, bind, listen, accept, connect
  • IDs for programs that want to use the network
  • From the 70’s -> 16 bit number
  • Assigned by convention
  • 80: http, 22: ssh, 25: email, etc.
  • Only admin can use < 1024

SSH and ports

  • ssh can can forward your ports
  • ssh -L 12345:hebbe06-2:9876 hebbe
  • ssh -R ...
  • ssh -D 12345
    • SOCKS