feat(secrets): add work gitconfig secret and a no-sudo replace flow (#346)

* feat(secrets): add work gitconfig secret, symlink it in home-manager

* feat(secrets): add a no-sudo replace recipe for new secrets

* refactor(secrets): move work gitconfig symlink into the desktop layer

.agents/skills/nix-config-secrets/SKILL.md

@@ -50,14 +50,17 @@ The private repository groups the `.age` files: `desktop/` (only desktops decryp
 ## 2. Add or change a secret
 
 Do the mechanical work yourself: edit `secrets.nix` in `~/codes/nix-secrets`, run the
-non-interactive steps, bump the lock, and add the declaration and consumer. Hand back only what
-needs a human: the `edit`/`rekey` recipes in [`secrets/Justfile`](../../../secrets/Justfile) (they
-handle key material and `$EDITOR`) and anything else under `sudo`. Commits and pushes follow the
-global git rules.
+non-interactive steps, bump the lock, and add the declaration and consumer. For a new secret, or a
+full replacement, pipe the plaintext into the `replace` recipe: it removes the target first, so
+agenix only encrypts and needs no `sudo`. Hand back only what needs a human: the partial `edit` and
+the `rekey` recipes in [`secrets/Justfile`](../../../secrets/Justfile) (they decrypt the current
+value, so they handle key material, `$EDITOR`, and `sudo`) and anything else under `sudo`. Commits
+and pushes follow the global git rules.
 
 1. In `~/codes/nix-secrets`, add the file under `desktop/` or `server/` with a matching
    `secrets.nix` entry, keyed by that exact path (e.g. `"./desktop/xxx.age"`), and the recipient set
-   from core rule 3. Then ask the user to create or edit it on a desktop with the command in §3.
+   from core rule 3. Then encrypt it with the `replace` recipe (§3); ask the user only when the
+   plaintext has to come from an interactive session.
 2. Here: `just upp mysecrets` (commits the lock) or `nix flake update mysecrets` (leaves it for you
    to commit). `git diff flake.lock` should show only `mysecrets` moving.
 3. Declare it in `secrets/nixos.nix` or `secrets/darwin.nix` under the right
@@ -65,7 +68,8 @@ global git rules.
 4. Point the consumer at the runtime path, from a module behind the same gate (core rule 4).
 5. `just test` and `just build-host <host>`, deploy, then verify as in §5.
 
-Changing only a secret's value is steps 1, 2, and the deploy.
+Changing only a secret's value is steps 1, 2, and the deploy: use `replace` for a full replacement
+(the agent can run it) or `edit` for a partial change (needs the host key).
 
 ## 3. The private repository
 
@@ -75,12 +79,15 @@ The agenix operations run against `~/codes/nix-secrets`. Their single source is
 `secrets.nix`:
 
 ```bash
-just -f secrets/Justfile edit ./desktop/xxx.age   # edit or create (interactive)
+just -f secrets/Justfile replace ./desktop/xxx.age < plaintext   # add or fully replace (no sudo)
+just -f secrets/Justfile edit ./desktop/xxx.age                  # partial edit (sudo, $EDITOR)
 just -f secrets/Justfile rekey                                   # re-encrypt after a recipient change
 ```
 
-`edit` passes `EDITOR=hx` to the root `agenix` process, because `sudo` resets the environment and
-the invoking user's `EDITOR` would not reach it; do not add `sudo -E` or set `EDITOR` yourself.
+`edit` and `rekey` decrypt the current value with the host key, so they need `sudo`; `replace` only
+encrypts to the recipients in `secrets.nix`, so it needs no `sudo`. `edit` passes `EDITOR=hx` to the
+root `agenix` process, because `sudo` resets the environment and the invoking user's `EDITOR` would
+not reach it; do not add `sudo -E` or set `EDITOR` yourself.
 
 The repository keeps a single amended commit: `git commit --amend -a --no-edit`,
 `git reflog expire --expire-unreachable=now --all`, `git gc --prune=now`, then force push. Treat

flake.lock

@@ -484,10 +484,10 @@
     "mysecrets": {
       "flake": false,
       "locked": {
-        "lastModified": 1790915701,
-        "narHash": "sha256-ES+PUPSCJBE4pwhTBwgKsoBit3oXjrI/OJt5xxngeT4=",
+        "lastModified": 1790919428,
+        "narHash": "sha256-04+A6Hmjj2lXGanEWfqoQkkAGiQgVT0CMY5BTOlfcBo=",
         "ref": "refs/heads/main",
-        "rev": "37e3c3ee87ac649fc52f9314db1cdf672a3c62b0",
+        "rev": "7b78dbb128be0ca52ac2815d5d8a73c5f883dada",
         "shallow": true,
         "type": "git",
         "url": "ssh://git@github.com/ryan4yin/nix-secrets.git"

home/base/core/git.nix

@@ -3,6 +3,7 @@
   lib,
   pkgs,
   myvars,
+  osConfig,
   ...
 }:
 {
@@ -14,6 +15,14 @@
     rm -f ${config.home.homeDirectory}/.gitconfig
   '';
 
+  # Work identity (email/name) lives encrypted in nix-secrets and is symlinked
+  # to ~/work/.gitconfig, which `programs.git.includes` below makes git read for
+  # repos under ~/work. `work-gitconfig` is only declared on desktops, so the
+  # symlink follows the secret.
+  home.file."work/.gitconfig" = lib.mkIf ((osConfig.age.secrets or { }) ? "work-gitconfig") {
+    source = config.lib.file.mkOutOfStoreSymlink "/etc/agenix/work-gitconfig";
+  };
+
   # GitHub CLI tool
   # https://cli.github.com/manual/
   home.packages = [ pkgs.gh ];

home/base/gui/work-gitconfig.nix

@@ -0,0 +1,13 @@
+{ config, ... }:
+{
+  # Work git identity (email/name), decrypted from nix-secrets. ~/work/.gitconfig
+  # is what `programs.git.includes` (home/base/core/git.nix) tells git to read
+  # for repos under ~/work.
+  #
+  # This lives in the desktop layer rather than core: base/gui is imported only
+  # by hosts that declare the desktop secret (the NixOS desktops via
+  # home/linux/gui.nix and macOS via home/darwin), so the consumer and the
+  # secret share the same gate.
+  home.file."work/.gitconfig".source =
+    config.lib.file.mkOutOfStoreSymlink "/etc/agenix/work-gitconfig";
+}

secrets/Justfile

@@ -13,10 +13,15 @@ editor := "hx"
 default:
     @just --list --justfile {{justfile()}}
 
-# Edit or create a secret (interactive); pipe the plaintext to write non-interactively
+# Partially edit an existing secret (interactive, needs sudo)
 edit file:
     sudo env EDITOR={{quote(editor)}} agenix -i {{identity}} -e {{quote(file)}}
 
+# Create a secret, or fully replace one, from plaintext on stdin (no sudo)
+replace file:
+    rm -f {{quote(file)}}
+    agenix -e {{quote(file)}}
+
 # Re-encrypt every secret after adding or changing a recipient key
 [confirm("Re-encrypt every secret in ~/codes/nix-secrets?")]
 rekey:

secrets/README.md

@@ -107,8 +107,17 @@ in
 }
 ```
 
-3. Create and edit the secret file `xxx.age` with the [`Justfile`](./Justfile) `edit` recipe
-   (interactive, from the repository root); pipe the plaintext to write it non-interactively:
+3. Create the secret file `xxx.age` from the repository root with the [`Justfile`](./Justfile)
+   `replace` recipe, piping the plaintext on stdin:
+
+```shell
+just -f secrets/Justfile replace ./xxx.age < plaintext
+```
+
+`replace` deletes the target first, so agenix only encrypts to the public keys in `secrets.nix` and
+never decrypts the old value — it needs no `sudo`. Use `edit` instead for a partial change to an
+existing secret: it decrypts the current value first with the host key
+(`/etc/ssh/ssh_host_ed25519_key`), so it needs `sudo`.
 
 ```shell
 just -f secrets/Justfile edit ./xxx.age

secrets/darwin.nix

@@ -82,6 +82,12 @@
         file = "${mysecrets}/desktop/nushell-secrets.nu.age";
       }
       // user_readable;
+
+      # work git identity, symlinked to ~/work/.gitconfig by home-manager
+      "work-gitconfig" = {
+        file = "${mysecrets}/desktop/work-gitconfig.age";
+      }
+      // user_readable;
     };
 
   # place secrets in /etc/
@@ -105,6 +111,10 @@
     "agenix/nushell-secrets.nu" = {
       source = config.age.secrets."nushell-secrets.nu".path;
     };
+
+    "agenix/work-gitconfig" = {
+      source = config.age.secrets."work-gitconfig".path;
+    };
   };
 
   # both the original file and the symlink should be readable and executable by the user

secrets/nixos.nix

@@ -120,6 +120,12 @@ in
           file = "${mysecrets}/desktop/nushell-secrets.nu.age";
         }
         // user_readable;
+
+        # work git identity, symlinked to ~/work/.gitconfig by home-manager
+        "work-gitconfig" = {
+          file = "${mysecrets}/desktop/work-gitconfig.age";
+        }
+        // user_readable;
       };
 
       # place secrets in /etc/
@@ -148,6 +154,16 @@ in
           mode = "0400";
           user = myvars.username;
         };
+
+        # Used by a home-manager module, so it must be readable by the user.
+        # Setting `mode` makes environment.etc copy the file instead of
+        # symlinking the runtime secret, so the owner must be set as well —
+        # otherwise it becomes a world-readable, root-owned copy of the secret.
+        "agenix/work-gitconfig" = {
+          source = config.age.secrets."work-gitconfig".path;
+          mode = "0400";
+          user = myvars.username;
+        };
       };
     })