# sops-nix Atomic secret provisioning for NixOS based on [sops](https://github.com/mozilla/sops). ## How it works Sops-nix decrypts secrets [sops files](https://github.com/mozilla/sops#2usage) on the target machine to files specified in the NixOS configuration at activation time. It also adjusts file permissions/owner/group. It uses either host ssh keys or GPG keys for decryption. In future we will also support cloud key management APIs such as AWS KMS, GCP KMS, Azure Key Vault or Hashicorp's vault. ## Features - Compatible with all NixOS deployment frameworks: [NixOps](https://github.com/NixOS/nixops), nixos-rebuild, [krops](https://github.com/krebs/krops/), [morph](https://github.com/DBCDK/morph), [nixus](https://github.com/Infinisil/nixus) - Version-control friendly: Since all files are encrypted they can directly committed to version control. The format is readable in diffs and there are also ways of showing [git diffs in cleartext](https://github.com/mozilla/sops#showing-diffs-in-cleartext-in-git) - Works well in teams: sops-nix comes with nix-shell hooks that allows quickly import multiple people to import all used keys. The cryptography used in sops is designed to be scalable: Secrets are only encrypted once with a master key instead of each machine/developer key. - CI friendly: Since sops files can be added to the Nix store without leaking secrets, a machine definition can be built as a whole. - Atomic upgrades: New secrets are written to a new directory which replaces the old directory in an atomic step. - Rollback support: If sops files are added to Nix store, old secrets can be rolled back. This is optional. - Fast: Unlike solutions implemented by NixOps, krops and morph there is no extra step required to upload secrets - Different storage formats: Secrets can be stored in YAML, JSON or binary. - Minimize configuration errors: sops files are checked against the configuration at evaluation time. ## Demo There is a configuration.nix example in the [deployment step](#5-deploy) of our usage example. ## Usage example ### 1. Install nix-sops Choose one of the following methods: #### [niv](https://github.com/nmattia/niv) (Current recommendation) First add it to niv: ```console $ niv add Mic92/sops-nix ``` Then add the following to your configuration.nix in the `imports` list: ```nix { imports = [ "${(import ./nix/sources.nix).sops-nix}/modules/sops" ]; } ``` #### nix-channel As root run: ```console $ nix-channel --add https://github.com/Mic92/sops-nix/archive/master.tar.gz sops-nix $ nix-channel --update ``` Then add the following to your configuration.nix in the `imports` list: ```nix { imports = [ ]; } ``` #### fetchTarball Add the following to your configuration.nix: ``` nix { imports = [ "${builtins.fetchTarball "https://github.com/Mic92/sops-nix/archive/master.tar.gz"}/modules/sops" ]; } ``` or with pinning: ```nix { imports = let # replace this with an actual commit id or tag commit = "298b235f664f925b433614dc33380f0662adfc3f"; in [ "${builtins.fetchTarball { url = "https://github.com/Mic92/sops-nix/archive/${commit}.tar.gz"; # replace this with an actual hash sha256 = "0000000000000000000000000000000000000000000000000000"; }}/modules/sops" ]; } ``` #### Flakes If you use experimental nix flakes support: ``` nix { inputs.sops-nix.url = github:Mic92/sops-nix; # optional, not necessary for the module #inputs.sops-nix.inputs.nixpkgs.follows = "nixpkgs"; outputs = { self, nixpkgs, sops-nix }: { # change `yourhostname` to your actual hostname nixosConfigurations.yourhostname = nixpkgs.lib.nixosSystem { # change to your system: system = "x86_64-linux"; modules = [ ./configuration.nix sops-nix.nixosModules.sops ]; }; }; } ``` ### 2. Generate a GPG key for yourself First generate yourself [a GPG key](https://docs.github.com/en/github/authenticating-to-github/generating-a-new-gpg-key) or use nix-sops conversion tool to convert an existing ssh key (we only support RSA keys right now): ``` $ nix run -f https://github.com/Mic92/sops-nix/archive/master.tar.gz ssh-to-pgp $ ssh-to-pgp -private-key -i $HOME/.ssh/id_rsa | gpg --import --quiet 2504791468b153b8a3963cc97ba53d1919c5dfd4 # This exports the public key $ ssh-to-pgp -i $HOME/.ssh/id_rsa -o $USER.asc 2504791468b153b8a3963cc97ba53d1919c5dfd4 ``` If you get: ``` ssh-to-pgp: failed to parse private ssh key: ssh: this private key is passphrase protected ``` then your ssh key is encrypted with your password and you need to create an unencrypted copy temporarily: ``` $ cp $HOME/.ssh/id_rsa /tmp/id_rsa $ ssh-keygen -p -N "" -f /tmp/id_rsa $ ssh-to-pgp -private-key -i /tmp/id_rsa | gpg --import --quiet ``` The hex string printed here is your GPG fingerprint that can be exported to `SOPS_PGP_FP`. ``` export SOPS_PGP_FP=2504791468b153b8a3963cc97ba53d1919c5dfd4 ``` If you have generated a GnuPG key directly you can get your fingerprint like this: ``` gpg --list-secret-keys /tmp/tmp.JA07D1aVRD/pubring.kbx ------------------------------- sec rsa2048 1970-01-01 [SCE] 9F89C5F69A10281A835014B09C3DC61F752087EF uid [ unknown] root ``` The fingerprint here is `9F89C5F69A10281A835014B09C3DC61F752087EF`. ### 3. Get a PGP Public key for your machine The easiest way to add new hosts is using ssh host keys (requires openssh to be enabled). Since sops does not natively supports ssh keys yet, nix-sops supports a conversion tool to store them as gpg keys. ``` $ nix-shell -p ssh-to-pgp $ ssh root@server01 "cat /etc/ssh/ssh_host_rsa_key" | ssh-to-pgp -o server01.asc # or with sudo $ ssh youruser@server01 "sudo cat /etc/ssh/ssh_host_rsa_key" | ssh-to-pgp -o server01.asc 0fd60c8c3b664aceb1796ce02b318df330331003 # Or just read them locally (or in a ssh session) $ ssh-to-pgp -i /etc/ssh/ssh_host_rsa_key -o server01.asc 0fd60c8c3b664aceb1796ce02b318df330331003 ``` Also the hex string here is the fingerprint of your server's gpg key that can be exported append to `SOPS_PGP_FP`: ``` export SOPS_PGP_FP=${SOPS_PGP_FP}:2504791468b153b8a3963cc97ba53d1919c5dfd4 ``` If you prefer having a separate GnuPG key, see [Use with GnuPG instead of ssh keys](#use-with-gnupg-instead-of-ssh-keys). ### 4. Create a sops file To create a sops file you need to set export `SOPS_PGP_FP` to include both the fingerprint of your personal gpg key (and your colleagues) and your servers: ``` export SOPS_PGP_FP="2504791468b153b8a3963cc97ba53d1919c5dfd4,2504791468b153b8a3963cc97ba53d1919c5dfd4" ``` sops-nix automates that with a hook for nix-shell and also takes care of importing all keys, allowing public keys to be stored in git: ``` # shell.nix with import {}; mkShell { # imports all files ending in .asc/.gpg and sets $SOPS_PGP_FP. sopsPGPKeyDirs = [ "./keys/hosts" "./keys/users" ]; # Also single files can be imported. #sopsPGPKeys = [ # "./keys/users/mic92.asc" # "./keys/hosts/server01.asc" #]; nativeBuildInputs = [ (pkgs.callPackage {}).sops-pgp-hook ]; } ``` Our directory structure looks like this: ```console $ tree . . ├── keys │   ├── hosts │   │   └── server01.asc │   └── users │   └── mic92.asc ``` After that you can open a new file with sops ``` nix-shell --run "sops secrets.yaml" ``` This will start your configured editor In our example we put the following content in it: ``` example-key: example-value ``` NOTE: At the moment we do not support nested data structures that sops support. This might change in the future. See also [Different file formats](#different-file-formats) As a result when saving the file the following content will be in it: ``` example-key: ENC[AES256_GCM,data:7QIOMLd2kZkeVVpH0Q==,iv:ROh+J59ZM6BtjZLhRj1Ylk6ROEvsiX6/UR8obHX8YcQ=,tag:QOiFoHKyGFBkhr9lcWBB3Q==,type:str] sops: kms: [] gcp_kms: [] azure_kv: [] lastmodified: '2020-07-13T09:09:14Z' mac: ENC[AES256_GCM,data:BCwTBxaW6qINVfixC32EEYrlqPvGz47wF+o/vNPqcwed1HPwZezlNy7Z4NFLbRcCLAELyeMqkJ+fi9XCWvnT3UvfwB45COpz/xZphURt3gyCVOyd9mT/s9cJ1O9vNy5iKblqCae2X0CTKee/GxJ0G725LDOL4r+oHM1+WWEInWo=,iv:S43qegidSqcaUaDjvQpEQj/qvF/OZcW32Yo05CfyTUs=,tag:npj5auJXZrg7jQwYSjC6Vg==,type:str] pgp: - created_at: '2020-07-13T08:34:30Z' enc: | -----BEGIN PGP MESSAGE----- hQIMAysxjfMwMxADAQ//SyBLvbpyuoTGCZCtoJyaFzZ+vCKWZaD7dCZEURRyNKFV 87wZyNO/rwtA1jP64Smqy0q2R8iZfoN0v5oVvtj2y5wFECs8Q5nONCVP4rs9nTRK n46w0v2UE2GqIWStFE7Mpv11qdZaMDoNGXq+n6s/uA2mwSYIVvzcWwhKvyKrMNrd iOlfCKl4QTaGgGupZqmT2S00AEMJzY5lohvtzAC1TlnXGXhetDyCHtkoN/NKZDU7 m7j1/pvlIwxTQKeA3FKuxDJDYk+p3+W/EgwEchYDzjo+5A529J/tuIfXWBOF7BAV ZiVVWISTahky/ioOMatNBAttu0lBGlSkovkbqIVsbTG7nF1wzGdToCxZmwQveEj7 0N8ZzocDkOXqS71LW+X2HYSeywxNUbg/S6MrHrZN8MOp5qnGztm8yrKW2gDDe+Nl nqJJ4lGg5CbODoDmhbPPof9tmWkykFmQSqmkjs4pcomcNthmcQvPVy75pnXEN9Wo 0cDRnHtgROCJLqfv1AsXWkSxtmZRMMQ1yKJIPVFUHSPodgAoTyA81sHi66RypDOV KezX6sW8UuTZ7q1oPcJFpaaHrpIHDn+bqPGMfhu4NVXFusdb7MPxtxlKflhTdc8B xzlrB6+LdnCaeN+KqB6DOvmiPP3nC91zflO1SpMY3yUOnTFDKZG7wnVjidyIuMvS UAHk6rhsBEJleAn5f4AuBVWtWLuvS4t1g9Lhci3833f7XNp+GFNy05UOsmUo9upr cgqaa2teuy2cbUtzS6gLBbcMA7SEs5MDYHjq6le/pwKv =ZYPM -----END PGP MESSAGE----- fp: 0FD60C8C3B664ACEB1796CE02B318DF330331003 - created_at: '2020-07-13T08:34:30Z' enc: | -----BEGIN PGP MESSAGE----- hQIMAysxjfMwMxADARAAqbkG7+WZIDDHNjFp4mcabdGcKaTenJmAQKJjk4vnAWZD 5Y6yInTldxldsFNvPcVmjZp/nM1otyH0MEHrurl5LX+BuUj8hRIE0ZFnNU0hNmyd toiwTE4GF1/otYFOPb9WnhDt+g6Y0ORuV/ZMSvP8PIu5/UnTeCkbZR/VudOvUq/m qF013M3q7UKssW4aReO2goFEhLjm8GfWksCuiGYKoHdJKzFAPYNhoxnxU3n43Oxp wz7QYFI0aA7RLZph70WjUNBun5+y4UyEJ8uNZ+cgVBeHQLqVdFUuejdzWK0d79Mr 5D9fxgSsPMz7yUMMdPl0T4rrAsZ977pftI9+JofqMN+u9UzUJwfTjnbCxlob39/t bfORkanzU8BNUCxpHyyqau921AUtfcqV9Y9Hf+qwxgVRVKgfETOqN376A1nhrYsf Mhvmcsk/rDssiRSIu11/mZwifcpALnS8WgO5tK+e/454ANqsiEdSRVogWBTzcIIs trm/6kwsTl7COzK0ThUKIb6aOfb910JQKaYq93qWqF1fceIf49Ubz9NVZc80J0an OiAaVGS0IOGI1ua8zciY7m+rr1BlrqJFtUm7hd8C9fMaF8YdB2SXgW8/HPGL8uTd f9ASg9TMSxhr7wjdqWp4EXXxdB6p4FXai9XBbgAJ2tKcS6AV6QmRVMoITZ7uZpvS UAG4nIgey9A57C8DSnt5zVPtxAsjDNiMubLUnHzTEJEJyQH5j2E41teujycOOAye I/UHMfpxSgrFfS8JJHYrJO0JQq/maBZi/VzZCl/G3IMn =Xls9 -----END PGP MESSAGE----- fp: 0FD60C8C3B664ACEB1796CE02B318DF330331003 - created_at: '2020-07-13T08:34:30Z' enc: | -----BEGIN PGP MESSAGE----- hQEMA5w9xh91IIfvAQf+I1FDo7rglcA6EF7jmQ0pq9FwYR/Dd9+4pu4mxUofQawj YsXPToVvyOKFrs1BZzW3Idyn5U/oXnkPN0qNK30DKir/wCt9OBqHHuhlo80OR2nS G2ZvHOJKEW3W5Hs2yT1e1MQxznI1lGFrsj6xgZAnKtK3Y6iy48XZ9pTw4Fxjkixw NppHtYrMj30mwV9XFAer0EfGlV2AIi70xBZ2inYAzPU2SpLEEoGyztjIeSS4VfhQ fnKSx3UjlVIix65s2ky0JqbL1wI+FPKNt2hWupW+M7en8BJ5VfAcbU7n0ZuQnaFx YPErw3agfhw1bNnqXh0y5aZ9sswt/Jy+IRkMJHLcqNJQAREdKgGmkW8wO2dngYYL IwLyChHJfcSnixboVcW5CIbfmIbOdgfEk2tdSiX1tJIA6qeeJz+D8UbR47nIdIw2 ZoID5dEUiDgikopjdqWk+zk= =43hf -----END PGP MESSAGE----- fp: 9F89C5F69A10281A835014B09C3DC61F752087EF unencrypted_suffix: _unencrypted version: 3.5.0 ``` ### 5. Deploy If you derived your server public key from ssh, all you need in your configuration.nix is: ```nix { imports = [ ]; # This will add secrets.yml to the nix store # You can avoid this by adding a string to the full path instead, i.e. # sops.defaultSopsFile = "/root/.sops/secrets.yaml"; sops.defaultSopsFile = ./secrets.yaml; sops.secrets.example-key = {}; } ``` On `nixos-rebuild switch` this will make the key accessible via `/run/secrets/example-key`: ```console $ cat /run/secrets/example-key example-value ``` `/run/secrets` is a symlink to `/etc/secret.d/1`: ```console $ ls -la /run/secrets lrwxrwxrwx 16 root 12 Jul 6:23  /run/secrets -> /run/secrets.d/1 ``` ## Set secret permission/owner and allow services to access it By default secrets are owned by `root:root`. Furthermore the parent directory `/run/secrets.d` is only owned by `root` and the `keys` group has read access to it: ``` console $ ls -la /run/secrets.d/1 total 24 drwxr-x--- 2 root keys 0 Jul 18 15:35 . drwxr-x--- 3 root keys 0 Jul 18 15:35 .. -r-------- 1 root root 20 Jul 18 15:35 borgbackup ``` The secrets option has further parameter to change secret permission. Consider the following nixos configuration example: ```nix { # Permission modes are in octal representation, # the digits reprsent: user|group|owner # 7 - full (rwx) # 6 - read and write (rw-) # 5 - read and execute (r-x) # 4 - read only (r--) # 3 - write and execute (-wx) # 2 - write only (-w-) # 1 - execute only (--x) # 0 - none (---) sops.secrets.example-secret.mode = "0440"; # Either a user id or group name representation of the secret owner # It is recommended to get the user name from `config.users..name` to avoid misconfiguration sops.secrets.example-secret.owner = config.users.nobody.name; # Either the group id or group name representation of the secret group # It is recommended to get the group name from `config.users..group` to avoid misconfiguration sops.secrets.example-secret.group = config.users.nobody.group; } ``` To access secrets each non-root process/service needs to be part of the keys group. For systemd services this can be achieved as following: ```nix { systemd.services.some-service = { serviceConfig.SupplementaryGroups = [ config.users.groups.keys.name ]; }; } ``` For login or system users this can be done like this: ```nix { users.users.example-user.extraGroups = [ config.users.groups.keys.name ]; } ``` The following example configures secrets for buildkite, a CI agent the service needs a token and a ssh private key to function: ```nix { pkgs, config, ... }: { services.buildkite-agents.builder = { enable = true; tokenPath = config.sops.secrets.buildkite-token.path; privateSshKeyPath = config.sops.secrets.buildkite-ssh-key.path; runtimePackages = [ pkgs.gnutar pkgs.bash pkgs.nix pkgs.gzip pkgs.git ]; }; systemd.services.buildkite-agent-builder = { serviceConfig.SupplementaryGroups = [ config.users.groups.keys.name ]; }; sops.secrets.buildkite-token.owner = config.users.buildkite-agent-builder.name; sops.secrets.buildkite-ssh-key.owner = config.users.buildkite-agent-builder.name; } ``` ## Symlinks to other directories Some services might expect files in certain locations. Using the `path` option as symlink to this directory can be created: ```nix { sops.secrets."home-assistant-secrets.yaml" = { owner = "hass"; path = "/var/lib/hass/secrets.yaml"; }; } ``` ```console $ ls -la /var/lib/hass/secrets.yaml lrwxrwxrwx 1 root root 40 Jul 19 22:36 /var/lib/hass/secrets.yaml -> /run/secrets/home-assistant-secrets.yaml ``` ## Different file formats At the moment we support the following file formats: YAML, JSON, binary NOTE: At the moment we do not support nested data structures that sops support. This might change in the future: We support the following yaml: ```yaml key: 1 ``` but not: ```yaml nested: key: 1 ``` nix-sops allows to specify multiple sops files in different file formats: ```nix { imports = [ ]; # The default sops file used for all secrets can be controlled using `sops.defaultSopsFile` sops.defaultSopsFile = ./secrets.yaml; # If you use something different from yaml, you can also specify it here: #sops.defaultSopsFormat = "yaml"; sops.secrets.github_token = { # The sops file can be also overwritten per secret... sopsFile = ./other-secrets.json; # ... as well as the format format = "json"; }; } ``` ### YAML Open a new file with sops ending in `.yaml`: ```console $ sops secrets.yaml ``` Than put in the following content: ```yaml github_token: 4a6c73f74928a9c4c4bc47379256b72e598e2bd3 # multi-line strings in yaml start with an | ssh_key: | -----BEGIN OPENSSH PRIVATE KEY----- b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW QyNTUxOQAAACDENhLwQI4v/Ecv65iCMZ7aZAL+Sdc0Cqyjkd012XwJzQAAAJht4at6beGr egAAAAtzc2gtZWQyNTUxOQAAACDENhLwQI4v/Ecv65iCMZ7aZAL+Sdc0Cqyjkd012XwJzQ AAAEBizgX7v+VMZeiCtWRjpl95dxqBWUkbrPsUSYF3DGV0rsQ2EvBAji/8Ry/rmIIxntpk Av5J1zQKrKOR3TXZfAnNAAAAE2pvZXJnQHR1cmluZ21hY2hpbmUBAg== -----END OPENSSH PRIVATE KEY----- ``` You can include it like this in your `configuration.nix`: ```nix { sops.defaultSopsFile = ./secrets.yaml; # yaml is the default #sops.defaultSopsFormat = "yaml"; sops.secrets.github_token = { format = "yaml"; # can be also set per secret sopsFile = ./secrets.yaml; }; } ``` ### JSON Open a new file with sops ending in `.json`: ```console $ sops secrets.json ``` Than put in the following content: ``` json { "github_token": "4a6c73f74928a9c4c4bc47379256b72e598e2bd3", "ssh_key": "-----BEGIN OPENSSH PRIVATE KEY-----\\nb3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW\\nQyNTUxOQAAACDENhLwQI4v/Ecv65iCMZ7aZAL+Sdc0Cqyjkd012XwJzQAAAJht4at6beGr\\negAAAAtzc2gtZWQyNTUxOQAAACDENhLwQI4v/Ecv65iCMZ7aZAL+Sdc0Cqyjkd012XwJzQ\\nAAAEBizgX7v+VMZeiCtWRjpl95dxqBWUkbrPsUSYF3DGV0rsQ2EvBAji/8Ry/rmIIxntpk\\nAv5J1zQKrKOR3TXZfAnNAAAAE2pvZXJnQHR1cmluZ21hY2hpbmUBAg==\\n-----END OPENSSH PRIVATE KEY-----\\n" } ``` You can include it like this in your `configuration.nix`: ```nix { sops.defaultSopsFile = ./secrets.json; # yaml is the default sops.defaultSopsFormat = "json"; sops.secrets.github_token = { format = "json"; # can be also set per secret sopsFile = ./secrets.json; }; } ``` ### Binary Unlike the other two formats for binaries one file correspond to one secret. This format allows to encrypt an arbitrary binary format that can't be put into JSON/YAML files. To encrypt an binary file use the following command: ``` console $ sops -e /tmp/krb5.keytab > krb5.keytab $ head krb5.keytab { "data": "ENC[AES256_GCM,data:bIsPHrjrl9wxvKMcQzaAbS3RXCI2h8spw2Ee+KYUTsuousUBU6OMIdyY0wqrX3eh/1BUtl8H9EZciCTW29JfEJKfi3ackGufBH+0wp6vLg7r,iv:TlKiOmQUeH3+NEdDUMImg1XuXg/Tv9L6TmPQrraPlCQ=,tag:dVeVvRM567NszsXKK9pZvg==,type:str]", "sops": { "kms": null, "gcp_kms": null, "azure_kv": null, "lastmodified": "2020-07-06T06:21:06Z", "mac": "ENC[AES256_GCM,data:ISjUzaw/5mNiwypmUrOk2DAZnlkbnhURHmTTYA3705NmRsSyUh1PyQvCuwglmaHscwl4GrsnIz4rglvwx1zYa+UUwanR0+VeBqntHwzSNiWhh7qMAQwdUXmdCNiOyeGy6jcSDsXUeQmyIWH6yibr7hhzoQFkZEB7Wbvcw6Sossk=,iv:UilxNvfHN6WkEvfY8ZIJCWijSSpLk7fqSCWh6n8+7lk=,tag:HUTgyL01qfVTCNWCTBfqXw==,type:str]", "pgp": [ { ``` It can be decrypted again like this: ``` console $ sops -d krb5.keytab > /tmp/krb5.keytab ``` This is how it can be included in your configuration.nix: ```nix { sops.secrets.krb5-keytab = { format = "binary"; sopsFile = ./krb5.keytab; }; } ``` ## Use with GnuPG instead of ssh keys If you prefer having a separate GnuPG key, sops-nix also comes with a helper tool: ``` $ nix-shell -p sops-init-gpg-key $ sops-init-gpg-key --hostname server01 --gpghome /tmp/newkey You can use the following command to save it to a file: cat > server01.asc <