If you have an encrypted ssh key for each domain you access (you should), and you keep your unlocked keys in a single ssh-agent (you maybe shouldn't), AND you've ever decided you need to forward your ssh-agent, then you should feel bad.

If you forward an ssh-agent with all your unique keys for every domain to a ssh server that is compromised - all those unique keys for all those unique domains you access? Kablooie! Done. Have fun rotating them all.

sshecret is a tool that creates an ssh-agent for each identity file found in your ssh_config(5) and executes ssh commands for a particular host using an environment that has access to only the key for that one host.

If a server to which you've forwarded your ssh-agent is compromised, then only the key used for that domain will be affected.

sshecret is a wrapper around ssh that automatically manages multiple ssh-agent(1) sockets each containing only a single unlocked ssh key. sshecret accepts the same parameters as ssh(1) - fundamentally sshecret uses execve(2) to wrap ssh, modifying the environment to ensure that each key in your ssh_config(5) uses its own ssh-agent.

Install via pip:

pip install --user sshecret

Install manually / via APT:

apt-get install python3-paramiko

git clone https://github.com/thcipriani/sshecret/

cp sshecret.py /usr/local/bin/sshecret

To use sshecret with git, point GIT_SSH to use sshecret by adding this to your shell initialization file (~/.bashrc or the like):

if command -v sshecret > /dev/null 2>&1; then
    export GIT_SSH=sshecret
fi

To use sshecret with scp add this alias to your shell initialization file:

if command -v sshecret > /dev/null 2>&1; then
    alias scp='scp -S sshecret'
fi

sshecret obviously won't help you if you're using the same ssh key for multiple domains. You are clearly beyond help.

sshecret depends on a correct ssh_config(5) for your user (found at ~/.ssh/config or wherever $SSH_CONF is pointing), so it'll get weird if that file is weird or nonexistent. Sorry, I guess.

Requirements:

• Paramiko

Usage:

usage: sshecret [whatever you want to pass to ssh]

sshecret is a wrapper around ssh that automatically manages multiple
ssh-agent(1)s each containing only a single ssh key.

    EXAMPLE: sshecret -A -L8080:localhost:80 -l johndoe -p2222 example.com

sshecret accepts the same parameters as ssh(1) - fundamentally sshecret uses
execve(2) to wrap ssh, modifying the environment to ensure that each key in
your ssh_config(5) uses its own ssh- agent.

optional arguments:
  -h, --help  show this help message and exit
  -v          Increase verbosity of output