enhance deterministic password support

common/deterministic-passwords.nix

@@ -1,18 +1,68 @@
+# generate passwords using hashes and a root key
+#
+# uses util-linux uuidgen as a KDF with custom namespaces to generate passwords across a network.
+#
+# 
+
 {pkgs, lib, config, ...}:
 with lib;
 with builtins;
 with import <cascade/functions>;
 
 {
-options = {
+options = with types; {
-  environment.deterministic-passwords = mkOption {
+  environment.deterministic-passwords.namespaces = mkOption {
+    type = listOf str;
+    default = [];
+    description = ''
+      Namespaces to be made available on the host.
+
+      For maximum security, this should _not_ contain anything unused on the host.
+
+      Any namespaces used by the Nix-based deterministic passwords module will be
+      included automatically.  This can usually be left as default.
+    '';
+  };
+  system.build.deterministic-passwords.generateNamespaces = mkOption {
+    type = str;
+    description = ''
+      command which expects a $ROOT variable and which produce namespace UUID secrets.
+
+      defaults to an automatically generated version.
+    '';
+  };
+  environment.deterministic-passwords.namespace-folder = mkOption {
+    type = str;
+    default = "/etc/cascade/deterministic-passwords/namespaces";
+    description = ''
+      Folder where namespace secrets are held.
+    '';
+  };
+  environment.deterministic-passwords.secrets = mkOption {
+    default = {};
+    description = ''
+      Secrets to be placed on disk.
+    '';
     type = with types; attrsOf (submodule ({config, name, ...}@args: {
       options = {
         enabled = mkEnableOption "password writer for ${name}" // {default = true;};
 
-        destination = mkOption {
+        namespace = mkOption {
           type = str;
-          description = ''Where to save the secret'';
+          description = ''
+            Namespace in which to create password.
+
+	    This is a namespace-prefixed, colon-delimited, hostname-compatible
+	    name which usually will represent the scope of members which should
+	    know the secret.  For hosts, the namespace prefix is "host:". I.e.,
+	    this will be "host:chimecho" for secrets which should only be known
+	    to the host named "chimecho".  It might instead be "service:vault"
+	    for secrets which should be known to a cluster serving vault, such
+	    as the database password.
+
+            Defaults to the hostname if the string is empty or not set.
+          '';
+          default = "";
         };
 
         group = mkOption {
@@ -33,10 +83,45 @@ options = {
           description = "Target file mode (octal)";
         };
 
-        action = mkOption {
+        destination = mkOption {
+          type = str;
+          description = ''Where to save the secret'';
+        };
+
+        writer = mkOption {
+          default = ''
+	    echo "$secret" > "$destination"
+	  '';
+          type = str;
+	  #merge = xl: join-string "\n" (map (cmd: "bash -c ${shq cmd}") xl);
+          description = ''
+	    Actions to perform on the remote host to create the new secret on disk.
+
+            $secret is the secret.
+	    $destination is the path to the destination file.
+	  '';
+        };
+
+	before = mkOption {
 	  default = [];
 	  type = listOf str;
-          description = "Action to perform on the remote host when the secret changes";
+          description = ''
+	    systemd units depending on this password being in place should be
+	    listed here.
+
+	    this translates directly to systemd.services."deterministic-passwords-''${NAME}".before
+	    systemd.services."deterministic-passwords-''${NAME}".requiredBy
+	  '';
+	};
+
+        action = mkOption {
+	  default = "";
+	  type = str;
+	  #merge = xl: join-string "\n" (map (cmd: "bash -c ${shq cmd}") xl);
+	  description = ''
+	    actions to perform after the secret has been written.  these actions MAY occur after the
+	    units in "before" are allowed to start.
+	  '';
 	};
       };
     }));
@@ -45,39 +130,83 @@ options = {
 
 config = 
 let shq = escapeShellArg;
-    makeUpdateScript = n: {enabled, destination, group, user, mode, action}@opts: ''
+    ns = {namespace,...}@opts: if namespace == "" then "host:${config.networking.hostName}" else namespace;
+    makeUpdateScript = n: {enabled, writer, destination, group, user, mode, action, ...}@opts: ''
+      ( set -e; export PATH="$PATH:/run/current-system/sw/sbin:/run/current-system/sw/bin"
+        # mkdir here instead of in a global activation script for simplicity.
+        mkdir -p ${shq config.environment.deterministic-passwords.namespace-folder}
+
+        if [ -e /etc/cascade/deterministic-passwords/namespaces/${ns opts} ];then
+          umask 0277
+          mkdir -p "$(dirname ${shq destination})"
 	  (
-      umask 0777
+            export secret="$( ${pkgs.util-linux}/bin/uuidgen -s -n $(cat /etc/cascade/deterministic-passwords/namespaces/${ns opts}) -N ${shq n} )"
-      ACTION=${shq (join-string "\n" action)}
+	    export destination=${shq destination}
-      ${pkgs.util-linux}/bin/uuidgen -s -n $(cat /etc/cascade/host-secret.uuid) -N ${shq n} > ${shq destination}
+	    bash -c ${shq writer}
+          )
           chown ${shq user}:${shq group} ${shq destination}
           chmod ${shq mode} ${shq destination}
-      ${pkgs.bash}/bin/bash -c "$ACTION"
+        fi
       )
     '';
-    secretToPath = n: {enabled, destination, group, user, mode, action}@opts: mkIf (enabled) { 
+    secretToPath = n: {enabled, destination, group, user, mode, action, ...}@opts: mkIf (enabled) { 
       wantedBy = [ "multi-user.target" ];
       pathConfig = {
-        PathChanged = "/etc/cascade/host-secret.uuid";
+        PathChanged = "/etc/cascade/deterministic-passwords/namespaces/${ns opts}";
       };
-      after = [ "network-online.target" ];
     };
-    secretToService = n: {enabled, destination, group, user, mode, action}@opts: mkIf (enabled) { 
+    secretToService = n: {enabled, before, ...}@opts: mkIf (enabled) { 
       serviceConfig.Type = "oneshot";
+      requiredBy = before;
+      before = before;
       script = makeUpdateScript n opts;
     };
-    secretToActivationScript = n: {enabled, destination, group, user, mode, action}@opts: { 
+    secretToAfterPath = n: {enabled, ...}@opts: mkIf (enabled) { 
+      wantedBy = [ "multi-user.target" ];
+      pathConfig = {
+        PathChanged = "/etc/cascade/deterministic-passwords/namespaces/${ns opts}";
+      };
+    };
+    secretToAfterService = n: {action, before, enabled, ...}@opts: mkIf (enabled) { 
+      serviceConfig.Type = "oneshot";
+      after = [ "deterministic-password-setup-${n}.service" ];
+      script = ''
+        set -e; export PATH="$PATH:/run/current-system/sw/sbin:/run/current-system/sw/bin"
+	${action}
+      '';
+    };
+    secretToActivationScript = n: {enabled, destination, ...}@opts: { 
       text = mkMerge [
-        (mkIf   enabled  (makeUpdateScript n opts))
         (mkIf (!enabled) ''rm -f ${shq destination}'')
       ];
     };
+    secretToGenerateNamespace = n: opts: let namespace = ns opts; in ''
+      printf 'echo %q > %q\n' "$(${pkgs.util-linux}/bin/uuidgen -s -n "$UUID" -N ${shq namespace})" ${shq config.environment.deterministic-passwords.namespace-folder}/${shq namespace}
+    '';
 in
 {
-  systemd.paths = mapAttrs' (n: v: nameValuePair "deterministic-password-${n}" (secretToPath n v)) config.environment.deterministic-passwords;
+  systemd.targets."deterministic-passwords".wants = [ "paths.target" ];
-  systemd.services = mapAttrs' (n: v: nameValuePair "deterministic-password-${n}" (secretToService n v)) config.environment.deterministic-passwords;
+  systemd.paths = (
-  system.activationScripts = mapAttrs' (n: v: nameValuePair "deterministic-password-${n}-refresh" (secretToActivationScript n v)) config.environment.deterministic-passwords;
+    (mapAttrs' (n: v: nameValuePair "deterministic-password-setup-${n}" (secretToPath n v)) config.environment.deterministic-passwords.secrets)
-  environment.deterministic-passwords = mkDefault {};
+    //
+    (mapAttrs' (n: v: nameValuePair "deterministic-password-after-${n}" (secretToAfterPath n v)) config.environment.deterministic-passwords.secrets)
+  );
+  systemd.services = (
+    (mapAttrs' (n: v: nameValuePair "deterministic-password-setup-${n}" (secretToService n v)) config.environment.deterministic-passwords.secrets)
+    //
+    (mapAttrs' (n: v: nameValuePair "deterministic-password-after-${n}" (secretToAfterService n v)) config.environment.deterministic-passwords.secrets)
+  );
+  system.build.deterministic-passwords.generateNamespaces = ''
+      if [ -z "$UUID" ];then
+        1>&2 echo "the root UUID must be in the UUID environment variable"
+        exit 1
+      fi
+
+      printf '(set -e; X=%q; mkdir -p "$X"; rm -f "$X"/*:*; )\n' ${shq config.environment.deterministic-passwords.namespace-folder}
+      (
+      ${ join-string "\n" (mapAttrsToList (n: v: (secretToGenerateNamespace n v)) config.environment.deterministic-passwords.secrets) }
+      true ; ) | ${pkgs.coreutils}/bin/sort | ${pkgs.coreutils}/bin/uniq
+      '';
 };
 
 }