From acaf36a1bfd32063aa86ed4c19adc5119dc5ed62 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Janne=20He=C3=9F?= Date: Tue, 29 Mar 2022 19:14:06 +0200 Subject: [PATCH] Implement home-manager support Closes #62 Closes #163 --- README.md | 35 ++++- modules/home-manager/sops.nix | 226 ++++++++++++++++++++++++++++++ modules/sops/default.nix | 1 + pkgs/sops-install-secrets/main.go | 75 +++++++--- 4 files changed, 314 insertions(+), 23 deletions(-) create mode 100644 modules/home-manager/sops.nix diff --git a/README.md b/README.md index 85e7857..d8814c4 100644 --- a/README.md +++ b/README.md @@ -19,6 +19,7 @@ environment variables that can be passed to sops. - 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), etc. - Version-control friendly: Since all files are encrypted they can be directly committed to version control without worry. Diffs of the secrets are readable, and [can be shown in cleartext](https://github.com/mozilla/sops#showing-diffs-in-cleartext-in-git). - CI friendly: Since sops files can be added to the Nix store without leaking secrets, a machine definition can be built as a whole from a repository, without needing to rely on external secrets or services. +- Home-manager friendly: Provides a home-manager module - Works well in teams: sops-nix comes with `nix-shell` hooks that allows multiple people to quickly import all GPG keys. The cryptography used in sops is designed to be scalable: Secrets are only encrypted once with a master key instead of encrypted per machine/developer key. @@ -34,7 +35,7 @@ There is a `configuration.nix` example in the [deployment step](#deploy-example) ## Supported encryption methods -sops-nix supports two basic ways of encryption, GPG and `age`. +sops-nix supports two basic ways of encryption, GPG and `age`. GPG is based on [GnuPG](https://gnupg.org/) and encrypts against GPG public keys. Private GPG keys may be used to decrypt the secrets on the target machine. The tool [`ssh-to-pgp`](https://github.com/Mic92/ssh-to-pgp) can @@ -733,6 +734,38 @@ This is how it can be included in your `configuration.nix`: } ``` +## Use with home manager + +sops-nix also provides a home-manager module. +This module provides a subset of features provided by the system-wide sops-nix since features like the creation of the ramfs and changing the owner of the secrets are not available for non-root users. + +Instead of running as an activation script, sops-nix runs as a systemd user service called `sops-nix.service`. +And instead of decrypting to `/run/secrets`, the secrets are decrypted to `$XDG_RUNTIME_DIR/secrets`. + +Usage example: +```nix +{ + # NixOS home-manager configuration + home-manager.sharedModules = [ + /path/to/sops-nix/modules/home-manager/sops.nix + ]; + + # Configuration via home.nix + imports = [ + /path/to/sops-nix/modules/home-manager/sops.nix + ]; + + # Configuration of secrets + sops = { + age.sshKeyPaths = [ "/home/user/path-to-ssh-key" ]; # must have no password! + sops.secrets.test = { + sopsFile = ./secrets.yml.enc; + path = "%r/test.txt"; # %r gets replaced with your $XDG_RUNTIME_DIR + }; + }; +} +``` + ## Use with GPG instead of SSH keys If you prefer having a separate GPG key, sops-nix also comes with a helper tool, `sops-init-gpg-key`: diff --git a/modules/home-manager/sops.nix b/modules/home-manager/sops.nix new file mode 100644 index 0000000..31bfa0e --- /dev/null +++ b/modules/home-manager/sops.nix @@ -0,0 +1,226 @@ +{ config, lib, pkgs, ... }: + +let + cfg = config.sops; + sops-install-secrets = (pkgs.callPackage ../.. {}).sops-install-secrets; + secretType = lib.types.submodule ({ config, name, ... }: { + options = { + name = lib.mkOption { + type = lib.types.str; + default = name; + description = '' + Name of the file used in /run/user/*/secrets + ''; + }; + + key = lib.mkOption { + type = lib.types.str; + default = name; + description = '' + Key used to lookup in the sops file. + No tested data structures are supported right now. + This option is ignored if format is binary. + ''; + }; + + path = lib.mkOption { + type = lib.types.str; + default = "%r/secrets/${name}"; + description = '' + Path where secrets are symlinked to. + If the default is kept no symlink is created. + ''; + }; + + format = lib.mkOption { + type = lib.types.enum [ "yaml" "json" "binary" ]; + default = cfg.defaultSopsFormat; + description = '' + File format used to decrypt the sops secret. + Binary files are written to the target file as is. + ''; + }; + + mode = lib.mkOption { + type = lib.types.str; + default = "0400"; + description = '' + Permissions mode of the in octal. + ''; + }; + + sopsFile = lib.mkOption { + type = lib.types.path; + default = cfg.defaultSopsFile; + defaultText = "\${config.sops.defaultSopsFile}"; + description = '' + Sops file the secret is loaded from. + ''; + }; + }; + }); + + manifestFor = suffix: secrets: pkgs.writeTextFile { + name = "manifest${suffix}.json"; + text = builtins.toJSON { + secrets = builtins.attrValues secrets; + secretsMountPoint = "%r/secrets.d"; + symlinkPath = "%r/secrets"; + keepGenerations = cfg.keepGenerations; + gnupgHome = cfg.gnupg.home; + sshKeyPaths = cfg.gnupg.sshKeyPaths; + ageKeyFile = cfg.age.keyFile; + ageSshKeyPaths = cfg.age.sshKeyPaths; + userMode = true; + logging = { + keyImport = builtins.elem "keyImport" cfg.log; + secretChanges = builtins.elem "secretChanges" cfg.log; + }; + }; + checkPhase = '' + ${sops-install-secrets}/bin/sops-install-secrets -check-mode=${if cfg.validateSopsFiles then "sopsfile" else "manifest"} "$out" + ''; + }; + + manifest = manifestFor "" cfg.secrets; +in { + options.sops = { + secrets = lib.mkOption { + type = lib.types.attrsOf secretType; + default = {}; + description = '' + Secrets to decrypt. + ''; + }; + + defaultSopsFile = lib.mkOption { + type = lib.types.path; + description = '' + Default sops file used for all secrets. + ''; + }; + + defaultSopsFormat = lib.mkOption { + type = lib.types.str; + default = "yaml"; + description = '' + Default sops format used for all secrets. + ''; + }; + + validateSopsFiles = lib.mkOption { + type = lib.types.bool; + default = true; + description = '' + Check all sops files at evaluation time. + This requires sops files to be added to the nix store. + ''; + }; + + keepGenerations = lib.mkOption { + type = lib.types.ints.unsigned; + default = 1; + description = '' + Number of secrets generations to keep. Setting this to 0 disables pruning. + ''; + }; + + log = lib.mkOption { + type = lib.types.listOf (lib.types.enum [ "keyImport" "secretChanges" ]); + default = [ "keyImport" "secretChanges" ]; + description = "What to log"; + }; + + age = { + keyFile = lib.mkOption { + type = lib.types.nullOr lib.types.path; + default = null; + example = "/var/lib/sops-nix/key.txt"; + description = '' + Path to age key file used for sops decryption. + ''; + }; + + generateKey = lib.mkOption { + type = lib.types.bool; + default = false; + description = '' + Whether or not to generate the age key. If this + option is set to false, the key must already be + present at the specified location. + ''; + }; + + sshKeyPaths = lib.mkOption { + type = lib.types.listOf lib.types.path; + default = []; + defaultText = lib.literalDocBook "The ed25519 keys from "; + description = '' + Paths to ssh keys added as age keys during sops description. + ''; + }; + }; + + gnupg = { + home = lib.mkOption { + type = lib.types.nullOr lib.types.str; + default = null; + example = "/root/.gnupg"; + description = '' + Path to gnupg database directory containing the key for decrypting the sops file. + ''; + }; + + sshKeyPaths = lib.mkOption { + type = lib.types.listOf lib.types.path; + default = []; + defaultText = lib.literalDocBook "The rsa keys from "; + description = '' + Path to ssh keys added as GPG keys during sops description. + This option must be explicitly unset if config.sops.gnupg.sshKeyPaths is set. + ''; + }; + }; + }; + + config = lib.mkIf (cfg.secrets != {}) { + assertions = [{ + assertion = cfg.gnupg.home != null || cfg.gnupg.sshKeyPaths != [] || cfg.age.keyFile != null || cfg.age.sshKeyPaths != []; + message = "No key source configurated for sops"; + } { + assertion = !(cfg.gnupg.home != null && cfg.gnupg.sshKeyPaths != []); + message = "Exactly one of sops.gnupg.home and sops.gnupg.sshKeyPaths must be set"; + }] ++ lib.optionals cfg.validateSopsFiles ( + lib.concatLists (lib.mapAttrsToList (name: secret: [{ + assertion = builtins.pathExists secret.sopsFile; + message = "Cannot find path '${secret.sopsFile}' set in sops.secrets.${lib.strings.escapeNixIdentifier name}.sopsFile"; + } { + assertion = + builtins.isPath secret.sopsFile || + (builtins.isString secret.sopsFile && lib.hasPrefix builtins.storeDir secret.sopsFile); + message = "'${secret.sopsFile}' is not in the Nix store. Either add it to the Nix store or set sops.validateSopsFiles to false"; + }]) cfg.secrets) + ); + + systemd.user.services.sops-nix = { + Unit = { + Description = "sops-nix activation"; + }; + Service = { + Environment = lib.mkIf (cfg.gnupg.home != null) [ "SOPS_GPG_EXEC=${pkgs.gnupg}/bin/gpg" ]; + Type = "oneshot"; + ExecStart = toString (pkgs.writeShellScript "sops-nix-user" (lib.optionalString cfg.age.generateKey '' + if [[ ! -f '${cfg.age.keyFile}' ]]; then + echo generating machine-specific age key... + mkdir -p $(dirname ${cfg.age.keyFile}) + # age-keygen sets 0600 by default, no need to chmod. + ${pkgs.age}/bin/age-keygen -o ${cfg.age.keyFile} + fi + '' + '' + ${sops-install-secrets}/bin/sops-install-secrets -ignore-passwd '${manifest}' + '')); + }; + Install.WantedBy = [ "default.target" ]; + }; + }; +} diff --git a/modules/sops/default.nix b/modules/sops/default.nix index 2aac71e..d17fa9a 100644 --- a/modules/sops/default.nix +++ b/modules/sops/default.nix @@ -126,6 +126,7 @@ let sshKeyPaths = cfg.gnupg.sshKeyPaths; ageKeyFile = cfg.age.keyFile; ageSshKeyPaths = cfg.age.sshKeyPaths; + userMode = false; logging = { keyImport = builtins.elem "keyImport" cfg.log; secretChanges = builtins.elem "secretChanges" cfg.log; diff --git a/pkgs/sops-install-secrets/main.go b/pkgs/sops-install-secrets/main.go index 12d5609..5355772 100644 --- a/pkgs/sops-install-secrets/main.go +++ b/pkgs/sops-install-secrets/main.go @@ -58,6 +58,7 @@ type manifest struct { GnupgHome string `json:"gnupgHome"` AgeKeyFile string `json:"ageKeyFile"` AgeSshKeyPaths []string `json:"ageSshKeyPaths"` + UserMode bool `json:"userMode"` Logging loggingConfig `json:"logging"` } @@ -179,15 +180,17 @@ func linksAreEqual(linkTarget, targetFile string, info os.FileInfo, secret *secr return linkTarget == targetFile && validUG } -func symlinkSecret(targetFile string, secret *secret) error { +func symlinkSecret(targetFile string, secret *secret, userMode bool) error { for { stat, err := os.Lstat(secret.Path) if os.IsNotExist(err) { if err := os.Symlink(targetFile, secret.Path); err != nil { return fmt.Errorf("Cannot create symlink '%s': %w", secret.Path, err) } - if err := secureSymlinkChown(secret.Path, targetFile, secret.owner, secret.group); err != nil { - return fmt.Errorf("Cannot chown symlink '%s': %w", secret.Path, err) + if !userMode { + if err := secureSymlinkChown(secret.Path, targetFile, secret.owner, secret.group); err != nil { + return fmt.Errorf("Cannot chown symlink '%s': %w", secret.Path, err) + } } return nil } else if err != nil { @@ -209,7 +212,7 @@ func symlinkSecret(targetFile string, secret *secret) error { } } -func symlinkSecrets(targetDir string, secrets []secret) error { +func symlinkSecrets(targetDir string, secrets []secret, userMode bool) error { for _, secret := range secrets { targetFile := filepath.Join(targetDir, secret.Name) if targetFile == secret.Path { @@ -219,7 +222,7 @@ func symlinkSecrets(targetDir string, secrets []secret) error { if err := os.MkdirAll(parent, os.ModePerm); err != nil { return fmt.Errorf("Cannot create parent directory of '%s': %w", secret.Path, err) } - if err := symlinkSecret(targetFile, &secret); err != nil { + if err := symlinkSecret(targetFile, &secret, userMode); err != nil { return fmt.Errorf("Failed to symlink secret '%s': %w", secret.Path, err) } } @@ -328,11 +331,16 @@ func decryptSecrets(secrets []secret) error { const RAMFS_MAGIC int32 = -2054924042 -func mountSecretFs(mountpoint string, keysGid int) error { +func mountSecretFs(mountpoint string, keysGid int, userMode bool) error { if err := os.MkdirAll(mountpoint, 0751); err != nil { return fmt.Errorf("Cannot create directory '%s': %w", mountpoint, err) } + // We can't create a ramfs as user + if userMode { + return nil + } + buf := unix.Statfs_t{} if err := unix.Statfs(mountpoint, &buf); err != nil { return fmt.Errorf("Cannot get statfs for directory '%s': %w", mountpoint, err) @@ -350,7 +358,7 @@ func mountSecretFs(mountpoint string, keysGid int) error { return nil } -func prepareSecretsDir(secretMountpoint string, linkName string, keysGid int) (*string, error) { +func prepareSecretsDir(secretMountpoint string, linkName string, keysGid int, userMode bool) (*string, error) { var generation uint64 linkTarget, err := os.Readlink(linkName) if err == nil { @@ -374,13 +382,15 @@ func prepareSecretsDir(secretMountpoint string, linkName string, keysGid int) (* if err := os.Mkdir(dir, os.FileMode(0751)); err != nil { return nil, fmt.Errorf("mkdir(): %w", err) } - if err := os.Chown(dir, 0, int(keysGid)); err != nil { - return nil, fmt.Errorf("Cannot change owner/group of '%s' to 0/%d: %w", dir, keysGid, err) + if !userMode { + if err := os.Chown(dir, 0, int(keysGid)); err != nil { + return nil, fmt.Errorf("Cannot change owner/group of '%s' to 0/%d: %w", dir, keysGid, err) + } } return &dir, nil } -func writeSecrets(secretDir string, secrets []secret, keysGid int) error { +func writeSecrets(secretDir string, secrets []secret, keysGid int, userMode bool) error { for _, secret := range secrets { fp := filepath.Join(secretDir, secret.Name) @@ -391,16 +401,20 @@ func writeSecrets(secretDir string, secrets []secret, keysGid int) error { if err := os.MkdirAll(pathSoFar, 0751); err != nil { return fmt.Errorf("Cannot create directory '%s' for %s: %w", pathSoFar, fp, err) } - if err := os.Chown(pathSoFar, 0, int(keysGid)); err != nil { - return fmt.Errorf("Cannot own directory '%s' for %s: %w", pathSoFar, fp, err) + if !userMode { + if err := os.Chown(pathSoFar, 0, int(keysGid)); err != nil { + return fmt.Errorf("Cannot own directory '%s' for %s: %w", pathSoFar, fp, err) + } } } if err := ioutil.WriteFile(fp, []byte(secret.value), secret.mode); err != nil { return fmt.Errorf("Cannot write %s: %w", fp, err) } - if err := os.Chown(fp, secret.owner, secret.group); err != nil { - return fmt.Errorf("Cannot change owner/group of '%s' to %d/%d: %w", fp, secret.owner, secret.group, err) + if !userMode { + if err := os.Chown(fp, secret.owner, secret.group); err != nil { + return fmt.Errorf("Cannot change owner/group of '%s' to %d/%d: %w", fp, secret.owner, secret.group, err) + } } } return nil @@ -488,7 +502,7 @@ func (app *appContext) validateSecret(secret *secret) error { if app.ignorePasswd || os.Getenv("NIXOS_ACTION") == "dry-activate" { secret.owner = 0 secret.group = 0 - } else if app.checkMode == Off { + } else if app.checkMode == Off || app.ignorePasswd { // we only access to the user/group during deployment owner, err := user.Lookup(secret.Owner) if err != nil { @@ -873,7 +887,7 @@ func parseFlags(args []string) (*options, error) { } var checkMode string fs.StringVar(&checkMode, "check-mode", "off", `Validate configuration without installing it (possible values: "manifest","sopsfile","off")`) - fs.BoolVar(&opts.ignorePasswd, "ignore-passwd", false, `Don't look up anything in /etc/passwd. Causes everything to be owned by root:root`) + fs.BoolVar(&opts.ignorePasswd, "ignore-passwd", false, `Don't look up anything in /etc/passwd. Causes everything to be owned by root:root or the user executing the tool in user mode`) if err := fs.Parse(args[1:]); err != nil { return nil, err } @@ -904,6 +918,21 @@ func installSecrets(args []string) error { return err } + if manifest.UserMode { + rundir, ok := os.LookupEnv("XDG_RUNTIME_DIR") + if !ok { + rundir = fmt.Sprintf("/run/user/%d", os.Getuid()) + } + manifest.SecretsMountPoint = strings.ReplaceAll(manifest.SecretsMountPoint, "%r", rundir) + manifest.SymlinkPath = strings.ReplaceAll(manifest.SymlinkPath, "%r", rundir) + var newSecrets []secret + for _, secret := range manifest.Secrets { + secret.Path = strings.ReplaceAll(secret.Path, "%r", rundir) + newSecrets = append(newSecrets, secret) + } + manifest.Secrets = newSecrets + } + app := appContext{ manifest: *manifest, checkMode: opts.checkMode, @@ -931,7 +960,7 @@ func installSecrets(args []string) error { isDry := os.Getenv("NIXOS_ACTION") == "dry-activate" - if err := mountSecretFs(manifest.SecretsMountPoint, keysGid); err != nil { + if err := mountSecretFs(manifest.SecretsMountPoint, keysGid, manifest.UserMode); err != nil { return fmt.Errorf("Failed to mount filesystem for secrets: %w", err) } @@ -983,21 +1012,23 @@ func installSecrets(args []string) error { return err } - secretDir, err := prepareSecretsDir(manifest.SecretsMountPoint, manifest.SymlinkPath, keysGid) + secretDir, err := prepareSecretsDir(manifest.SecretsMountPoint, manifest.SymlinkPath, keysGid, manifest.UserMode) if err != nil { return fmt.Errorf("Failed to prepare new secrets directory: %w", err) } - if err := writeSecrets(*secretDir, manifest.Secrets, keysGid); err != nil { + if err := writeSecrets(*secretDir, manifest.Secrets, keysGid, manifest.UserMode); err != nil { return fmt.Errorf("Cannot write secrets: %w", err) } - if err := handleModifications(isDry, manifest.Logging, manifest.SymlinkPath, *secretDir, manifest.Secrets); err != nil { - return fmt.Errorf("Cannot request units to restart: %w", err) + if !manifest.UserMode { + if err := handleModifications(isDry, manifest.Logging, manifest.SymlinkPath, *secretDir, manifest.Secrets); err != nil { + return fmt.Errorf("Cannot request units to restart: %w", err) + } } // No need to perform the actual symlinking if isDry { return nil } - if err := symlinkSecrets(manifest.SymlinkPath, manifest.Secrets); err != nil { + if err := symlinkSecrets(manifest.SymlinkPath, manifest.Secrets, manifest.UserMode); err != nil { return fmt.Errorf("Failed to prepare symlinks to secret store: %w", err) } if err := atomicSymlink(*secretDir, manifest.SymlinkPath); err != nil {