28 lines
1.6 KiB
Markdown
28 lines
1.6 KiB
Markdown
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# Always use -t with ssh-add (and always set passwords on your ssh keys)
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Many people use SSH keys for the sole purpose of avoiding password entry when
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logging into remote boxes. That is legtimate, especially if you frequently run
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remote commands or wish to take advantage of remote tab complation, but creating
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a key with an empty password is certainly the wrong approach---if an attacker
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gets a hold of the key, then they have access to all of your boxes before you
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have the chance to notice and revoke the key.
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ssh-agent exists for this purpose. The problem is---creating an agent only to
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place the key in memory indefinately is also a terrible idea. If your system
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does become compromised and the attacker is either root access or access as your
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user, then they can simply connect to the ssh-agent (unless it's password
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protected) and start using your key. Also consider that, should you leave your
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box unattended for even a moment without locking it (for whatever reason---shit
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happens), an attacker could gain physical access to your PC (and an attacker may
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just be a coworker looking to play a prank).
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Every morning at work, I begin the day by typing ssh-add followed by an
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appropriate lifetime (be it the duration of the work day, or the duration that I
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think I will need the key). This way, your key is in memory when you are likely
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to be physically present at the box and it is automatically removed from memory
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after a given lifetime. Additionally, I like to add `ssh-add -D` to the script
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that locks my PC when I walk away from my desk: that will immediately clear all
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keys from memory, just in case.
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