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diff --git a/content/blog/1password-ssh-agent.md b/content/blog/1password-ssh-agent.md new file mode 100644 index 0000000..9be0581 --- /dev/null +++ b/content/blog/1password-ssh-agent.md @@ -0,0 +1,201 @@ +--- +title: 1password's ssh agent and nix +date: 2023-11-13 +tags: +- ssh +- git +- nix +--- +[A while ago](https://blog.1password.com/1password-ssh-agent/), 1password introduced an SSH agent, and I've been using it for a while now. The following describe how I've configured it with `nix`. All my ssh keys are in 1password, and it's the only ssh agent I'm using at this point. + +## Personal configuration + +I have a personal 1password account, and I've created a new SSH key in it that I use for both authenticating to github and to sign commits. I use [nix-darwin](http://daiderd.com/nix-darwin/) and [home-manager](https://github.com/nix-community/home-manager) to configure my personal machine. + +This is how I configure ssh: +```nix +programs.ssh = { + enable = true; + forwardAgent = true; + serverAliveInterval = 60; + controlMaster = "auto"; + controlPersist = "30m"; + extraConfig = '' + IdentityAgent "~/Library/Group Containers/2BUA8C4S2C.com.1password/t/agent.sock" + ''; + matchBlocks = { + "github.com" = { + hostname = "github.com"; + user = "git"; + forwardAgent = false; + extraOptions = { preferredAuthentications = "publickey"; }; + }; + }; +}; +``` + +The configuration for git: +```nix +{ lib, pkgs, config, ... }: +let + sshPub = builtins.fromTOML ( + builtins.readFile ../../configs/ssh-pubkeys.toml + ); +in +{ + home.file.".ssh/allowed_signers".text = lib.concatMapStrings (x: "franck@fcuny.net ${x}\n") (with sshPub; [ ykey-laptop ykey-backup op ]); + + programs.git = { + enable = true; + userName = "Franck Cuny"; + userEmail = "franck@fcuny.net"; + + signing = { + key = "key::${sshPub.op}"; + signByDefault = true; + }; + + extraConfig = { + gpg.format = "ssh"; + gpg.ssh.allowedSignersFile = "~/.ssh/allowed_signers"; + gpg.ssh.program = "/Applications/1Password.app/Contents/MacOS/op-ssh-sign"; + }; +} +``` + +In the repository with my nix configuration, I've a file `ssh-pubkeys.toml` that contains all the public ssh keys I keep track of (mine and a few other developers). Keys from that file are used to create the file `~/.ssh/allowed_signers` that is then used by `git` (for example `git log --show-signature`) when I want to ensure commits are signed with a valid key. + +`ssh-pubkeys.toml` looks like this: +```toml +# yubikey key connected to the laptop +ykey-laptop="ssh-ed25519 ..." +# backup yubikey key +ykey-backup="ssh-ed25519 ..." +# 1password key +op="ssh-ed25519 ..." +``` + +And the following is for `zsh` so that I can use the agent for other commands that I run in the shell: +```nix +programs.zsh.envExtra = '' + # use 1password ssh agent + # see https://developer.1password.com/docs/ssh/get-started#step-4-configure-your-ssh-or-git-client + export SSH_AUTH_SOCK=~/Library/Group\ Containers/2BUA8C4S2C.com.1password/t/agent.sock +''; +``` + +And that's it, this is enough to get use the agent for all my personal use cases. + +## Work configuration + +The work configuration is slightly different. Here I want to use both my work and personal keys so that I can clone some of my personal repositories on the work machine (for example my emacs configuration). We also use both github.com and a github enterprise instance and I need to authenticate against both. + +I've imported my existing keys into 1password, and I keep the public keys on the disk: `$HOME/.ssh/work_gh.pub` and `$HOME/.ssh/personal_gh.pub`. I've removed the private keys from the disk. + +This is the configuration I use for work: +```nix +programs.ssh = { + enable = true; + forwardAgent = true; + serverAliveInterval = 60; + controlMaster = "auto"; + controlPersist = "30m"; + extraConfig = '' + IdentityAgent "~/Library/Group Containers/2BUA8C4S2C.com.1password/t/agent.sock" + ''; + matchBlocks = { + "personal" = { + hostname = "github.com"; + user = "git"; + forwardAgent = false; + identifyFile = "~/.ssh/personal_gh.pub"; + identitiesOnly = true; + extraOptions = { preferredAuthentications = "publickey"; }; + }; + "work" = { + hostname = "github.com"; + user = "git"; + forwardAgent = false; + identifyFile = "~/.ssh/work_gh.pub"; + identitiesOnly = true; + extraOptions = { preferredAuthentications = "publickey"; }; + }; + "github.enterprise" = { + hostname = "github.enterprise"; + user = "git"; + forwardAgent = false; + identifyFile = "~/.ssh/work_gh.pub"; + identitiesOnly = true; + extraOptions = { preferredAuthentications = "publickey"; }; + }; + }; +}; +``` + +I also create a configuration file for the 1password agent, to make sure I can use the keys from all the accounts: +```nix + # Generate ssh agent config for 1Password - I want both my personal and work keys + home.file.".config/1Password/ssh/agent.toml".text = '' + [[ssh-keys]] + account = "my.1password.com" + [[ssh-keys]] + account = "$work.1password.com" + ''; +``` + +Then the ssh configuration: +```nix +{ config, lib, pkgs, ... }: +let + sshPub = builtins.fromTOML ( + builtins.readFile ../etc/ssh-pubkeys.toml + ); +in +{ + home.file.".ssh/allowed_signers".text = lib.concatMapStrings (x: "franck@fcuny.net ${x}\n") (with sshPub; [ work_laptop op ]); + + programs.git = { + enable = true; + + signing = { + key = "key::${sshPub.op}"; + signByDefault = true; + }; + + extraConfig = { + gpg.format = "ssh"; + gpg.ssh.allowedSignersFile = "~/.ssh/allowed_signers"; + gpg.ssh.program = "/Applications/1Password.app/Contents/MacOS/op-ssh-sign"; + + url = { + "ssh://git@github.enterprise/" = { + insteadOf = "https://github.enterprise/"; + }; + }; + }; + }; +} +``` + +Now, when I clone a repository, instead of doing `git clone git@github.com/$WORK/repo` I do `git clone work:/$WORK/repo`. + +## Conclusion + +I've used yubikey to sign my commits for a while, but I find the 1password ssh agent a bit more convenient. The initial setup for yubikey was not as straightforward (granted, it's a one time thing per key). + +On my personal machine, my `$HOME/.ssh` looks as follow: +```sh +➜ ~ ls -l ~/.ssh ~ +total 16 +lrwxr-xr-x@ 1 fcuny staff 83 Nov 6 17:03 allowed_signers -> /nix/store/v9qhbr2vb7w6bd24ypbjjz59xis3g8y2-home-manager-files/.ssh/allowed_signers +lrwxr-xr-x@ 1 fcuny staff 74 Nov 6 17:03 config -> /nix/store/v9qhbr2vb7w6bd24ypbjjz59xis3g8y2-home-manager-files/.ssh/config +-rw-------@ 1 fcuny staff 828 Nov 13 17:53 known_hosts +``` + +When I create a new commit, 1password ask me to authorize git to use the agent and sign the commit. Same when I want to ssh to a host. + +When I'm working on the macbook, I use touch ID to confirm, and when the laptop is connected to a dock, I need to type my 1password's password to unlock it and authorize the command. + +There's a cache in the agent so I'm not prompted too often. I find this convenient, I will never have to copy my ssh key when I get a new laptop, since it's already in 1password. + +The agent has worked flawlessly so far, and I'm happy with this setup. |