Do not render templates when decrypting neededForUsers secrets

This fixes https://github.com/Mic92/sops-nix/issues/659

In https://github.com/Mic92/sops-nix/pull/649, we started rendering
templates twice:

1. When rendering `neededForUsers` secrets (if there are any
   `neededForUsers` secrets).
2. When decrypting "regular" secrets.

This alone was weird and wrong, but didn't cause issues
for people until https://github.com/Mic92/sops-nix/pull/655, which
triggered https://github.com/Mic92/sops-nix/issues/659. The cause is not
super obvious:

1. When rendering `neededForUsers` secrets, we'd generate templates in
   `/run/secrets-for-users/rendered`.
2. However, the `path` for these templates is in
   `/run/secrets/rendered`, which is not inside of the
   `/run/secrets-for-users` directory we're dealing with, so we'd
   generate a symlink from `/run/secrets/rendered/<foo>` to
   `/run/secrets-for-users/rendered/<foo>`, which required making
   the parent directory of the symlink (`/run/secrets/rendered/`).
3. This breaks sops-nix's assumption that `/run/secrets` either doesn't
   exist, or is a symlink, and you get the symptoms described in
   <https://github.com/Mic92/sops-nix/issues/659>.

Reproducing this in a test was straightforward: just expand our existing
template test to also have a `neededForUsers` secret.

Fixing this was also straightforward: don't render templates during the
`neededForUsers` phase (if we want to add support for `neededForUsers`
templates in the future, that would be straightforward to do, but I
opted not do that here).

modules/home-manager/sops.nix

@@ -3,7 +3,7 @@
 let
   cfg = config.sops;
   sops-install-secrets = (pkgs.callPackage ../.. {}).sops-install-secrets;
-  secretType = lib.types.submodule ({ config, name, ... }: {
+  secretType = lib.types.submodule ({ name, ... }: {
     options = {
       name = lib.mkOption {
         type = lib.types.str;
@@ -71,10 +71,11 @@ let
     merge = lib.mergeEqualOption;
   };
 
-  manifestFor = suffix: secrets: pkgs.writeTextFile {
+  manifestFor = suffix: secrets: templates: pkgs.writeTextFile {
     name = "manifest${suffix}.json";
     text = builtins.toJSON {
       secrets = builtins.attrValues secrets;
+      templates = builtins.attrValues templates;
       secretsMountPoint = cfg.defaultSecretsMountPoint;
       symlinkPath = cfg.defaultSymlinkPath;
       keepGenerations = cfg.keepGenerations;
@@ -93,11 +94,11 @@ let
     '';
   };
 
-  manifest = manifestFor "" cfg.secrets;
+  manifest = manifestFor "" cfg.secrets cfg.templates;
 
   escapedAgeKeyFile = lib.escapeShellArg cfg.age.keyFile;
 
-  script = toString (pkgs.writeShellScript "sops-nix-user" ((lib.optionalString cfg.age.generateKey ''
+  script = toString (pkgs.writeShellScript "sops-nix-user" (lib.optionalString cfg.age.generateKey ''
     if [[ ! -f ${escapedAgeKeyFile} ]]; then
       echo generating machine-specific age key...
       ${pkgs.coreutils}/bin/mkdir -p $(${pkgs.coreutils}/bin/dirname ${escapedAgeKeyFile})
@@ -106,7 +107,7 @@ let
     fi
   '' + ''
     ${sops-install-secrets}/bin/sops-install-secrets -ignore-passwd ${manifest}
-  '')));
+  ''));
 in {
   options.sops = {
     secrets = lib.mkOption {

modules/sops/default.nix

@@ -8,7 +8,7 @@ let
     inherit cfg;
     inherit (pkgs) writeTextFile;
   };
-  manifest = manifestFor "" regularSecrets {};
+  manifest = manifestFor "" regularSecrets regularTemplates {};
 
   pathNotInStore = lib.mkOptionType {
     name = "pathNotInStore";
@@ -20,6 +20,9 @@ let
 
   regularSecrets = lib.filterAttrs (_: v: !v.neededForUsers) cfg.secrets;
 
+  # Currently, all templates are "regular" (there's no support for `neededForUsers` for templates.)
+  regularTemplates = cfg.templates;
+
   useSystemdActivation = (options.systemd ? sysusers && config.systemd.sysusers.enable) ||
     (options.services ? userborn && config.services.userborn.enable);
 
@@ -354,7 +357,7 @@ in {
 
       sops.environment.SOPS_GPG_EXEC = lib.mkIf (cfg.gnupg.home != null || cfg.gnupg.sshKeyPaths != []) (lib.mkDefault "${pkgs.gnupg}/bin/gpg");
 
-      # When using sysusers we no longer be started as an activation script because those are started in initrd while sysusers is started later.
+      # When using sysusers we no longer are started as an activation script because those are started in initrd while sysusers is started later.
       systemd.services.sops-install-secrets = lib.mkIf (regularSecrets != { } && useSystemdActivation) {
         wantedBy = [  "sysinit.target" ];
         after = [ "systemd-sysusers.service" ];

modules/sops/manifest-for.nix

@@ -1,11 +1,12 @@
 { writeTextFile, cfg }:
 
-suffix: secrets: extraJson:
+suffix: secrets: templates: extraJson:
 
 writeTextFile {
   name = "manifest${suffix}.json";
   text = builtins.toJSON ({
     secrets = builtins.attrValues secrets;
+    templates = builtins.attrValues templates;
     # Does this need to be configurable?
     secretsMountPoint = "/run/secrets.d";
     symlinkPath = "/run/secrets";
@@ -15,7 +16,6 @@ writeTextFile {
     ageKeyFile = cfg.age.keyFile;
     ageSshKeyPaths = cfg.age.sshKeyPaths;
     useTmpfs = cfg.useTmpfs;
-    templates = cfg.templates;
     placeholderBySecretName = cfg.placeholder;
     userMode = false;
     logging = {

modules/sops/secrets-for-users/default.nix

@@ -2,6 +2,7 @@
 let
   cfg = config.sops;
   secretsForUsers = lib.filterAttrs (_: v: v.neededForUsers) cfg.secrets;
+  templatesForUsers = {};  # We do not currently support `neededForUsers` for templates.
   manifestFor = pkgs.callPackage ../manifest-for.nix {
     inherit cfg;
     inherit (pkgs) writeTextFile;
@@ -9,7 +10,7 @@ let
   withEnvironment = import ../with-environment.nix {
     inherit cfg lib;
   };
-  manifestForUsers = manifestFor "-for-users" secretsForUsers {
+  manifestForUsers = manifestFor "-for-users" secretsForUsers templatesForUsers {
     secretsMountPoint = "/run/secrets-for-users.d";
     symlinkPath = "/run/secrets-for-users";
   };

pkgs/sops-install-secrets/main.go

@@ -71,7 +71,7 @@ type template struct {
 
 type manifest struct {
 	Secrets                 []secret             `json:"secrets"`
-	Templates               map[string]*template `json:"templates"`
+	Templates               []template           `json:"templates"`
 	PlaceholderBySecretName map[string]string    `json:"placeholderBySecretName"`
 	SecretsMountPoint       string               `json:"secretsMountPoint"`
 	SymlinkPath             string               `json:"symlinkPath"`
@@ -185,7 +185,7 @@ func linksAreEqual(linkTarget, targetFile string, info os.FileInfo, owner int, g
 	return linkTarget == targetFile && validUG
 }
 
-func symlinkSecret(targetFile string, path string, owner int, group int, userMode bool) error {
+func createSymlink(targetFile string, path string, owner int, group int, userMode bool) error {
 	for {
 		stat, err := os.Lstat(path)
 		if os.IsNotExist(err) {
@@ -217,7 +217,7 @@ func symlinkSecret(targetFile string, path string, owner int, group int, userMod
 	}
 }
 
-func symlinkSecrets(targetDir string, secrets []secret, templates map[string]*template, userMode bool) error {
+func symlinkSecretsAndTemplates(targetDir string, secrets []secret, templates []template, userMode bool) error {
 	for _, secret := range secrets {
 		targetFile := filepath.Join(targetDir, secret.Name)
 		if targetFile == secret.Path {
@@ -227,7 +227,7 @@ func symlinkSecrets(targetDir string, secrets []secret, templates map[string]*te
 		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.Path, secret.owner, secret.group, userMode); err != nil {
+		if err := createSymlink(targetFile, secret.Path, secret.owner, secret.group, userMode); err != nil {
 			return fmt.Errorf("failed to symlink secret '%s': %w", secret.Path, err)
 		}
 	}
@@ -241,7 +241,7 @@ func symlinkSecrets(targetDir string, secrets []secret, templates map[string]*te
 		if err := os.MkdirAll(parent, os.ModePerm); err != nil {
 			return fmt.Errorf("cannot create parent directory of '%s': %w", template.Path, err)
 		}
-		if err := symlinkSecret(targetFile, template.Path, template.owner, template.group, userMode); err != nil {
+		if err := createSymlink(targetFile, template.Path, template.owner, template.group, userMode); err != nil {
 			return fmt.Errorf("failed to symlink template '%s': %w", template.Path, err)
 		}
 	}
@@ -610,8 +610,9 @@ func (app *appContext) validateSecret(secret *secret) error {
 	return app.validateSopsFile(secret, &file)
 }
 
-func renderTemplates(templates map[string]*template, secretByPlaceholder map[string]*secret) {
+func renderTemplates(templates []template, secretByPlaceholder map[string]*secret) {
-	for _, template := range templates {
+	for i := range templates {
+		template := &templates[i]
 		rendered := renderTemplate(&template.content, secretByPlaceholder)
 		template.value = []byte(rendered)
 	}
@@ -702,7 +703,8 @@ func (app *appContext) validateManifest() error {
 		}
 	}
 
-	for _, template := range m.Templates {
+	for i := range m.Templates {
+		template := &m.Templates[i]
 		if err := app.validateTemplate(template); err != nil {
 			return err
 		}
@@ -893,7 +895,7 @@ func symlinkWalk(filename string, linkDirname string, walkFn filepath.WalkFunc)
 	return filepath.Walk(filename, symWalkFunc)
 }
 
-func handleModifications(isDry bool, logcfg loggingConfig, symlinkPath string, secretDir string, secrets []secret, templates map[string]*template) error {
+func handleModifications(isDry bool, logcfg loggingConfig, symlinkPath string, secretDir string, secrets []secret, templates []template) error {
 	var restart []string
 	var reload []string
 
@@ -1148,7 +1150,7 @@ func replaceRuntimeDir(path, rundir string) (ret string) {
 	return
 }
 
-func writeTemplates(targetDir string, templates map[string]*template, keysGID int, userMode bool) error {
+func writeTemplates(targetDir string, templates []template, keysGID int, userMode bool) error {
 	for _, template := range templates {
 		fp := filepath.Join(targetDir, template.Name)
 
@@ -1302,7 +1304,7 @@ func installSecrets(args []string) error {
 	if isDry {
 		return nil
 	}
-	if err := symlinkSecrets(manifest.SymlinkPath, manifest.Secrets, manifest.Templates, manifest.UserMode); err != nil {
+	if err := symlinkSecretsAndTemplates(manifest.SymlinkPath, manifest.Secrets, manifest.Templates, manifest.UserMode); err != nil {
 		return fmt.Errorf("failed to prepare symlinks to secret store: %w", err)
 	}
 	if err := atomicSymlink(*secretDir, manifest.SymlinkPath); err != nil {

pkgs/sops-install-secrets/nixos-test.nix

@@ -266,6 +266,10 @@ in {
         age.keyFile = "/run/age-keys.txt";
         defaultSopsFile = ./test-assets/secrets.yaml;
         secrets.test_key = { };
+
+        # Verify that things work even with `neededForUsers` secrets. See
+        # <https://github.com/Mic92/sops-nix/issues/659>.
+        secrets."nested/test/file".neededForUsers = true;
       };
 
       # must run before sops sets up keys