run authelia's digest under a real shell, not the service user's nologin

nix/host-modules/lib/oidc-client-secrets.nix

@@ -16,11 +16,12 @@
 # its digest but the store could not be read, so the caller finishes its work
 # from the digests and then retries.
 #
-# Pure function — NOT a NixOS module. Call it after `./store-seeded-secret.nix`
-# and `./atomic-write-secret.nix`, with `store_init` and `store_login` run and
-# `$clients` set to the digest directory. Needs `authelia`, `bao`, `script`
+# Pure function of `shell`, the path of a real shell; NOT a NixOS module. Call
+# it after `./store-seeded-secret.nix` and `./atomic-write-secret.nix`, with
+# `store_init` and `store_login` run and `$clients` set to the digest directory.
+# Needs `authelia`, `bao`, `script`
 # (util-linux), `coreutils`, `grep` and `sed` on the caller's `path`.
-{ }:
+{ shell }:
 ''
   # <leaf>. Sets CLIENT_SECRET_VALUE. 0: the store holds a value. 1: it holds
   # none. 2: it cannot tell (not logged in, down, or refusing the read).
@@ -43,10 +44,11 @@
   # written. The CLI takes a password only on a terminal prompt or in argv,
   # and argv is world-readable in /proc, so the prompt is answered through a
   # pty from stdin. The pty echoes the password into the pipe, and only the
-  # `Digest:` line leaves it.
+  # `Digest:` line leaves it. `script` runs the command as `$SHELL -c`, and the
+  # service user's login shell is nologin, so the call sets `SHELL` to `shell`.
   client_secret_digest() {
     printf '%s\n' "$1" \
-      | timeout 60 script -qec "authelia crypto hash generate pbkdf2 --variant sha512 --no-confirm" /dev/null \
+      | SHELL=${shell} timeout 60 script -qec "authelia crypto hash generate pbkdf2 --variant sha512 --no-confirm" /dev/null \
       | tr -d '\r' | sed -n 's/^Digest: *//p'
   }
 

nix/host-modules/swarm-authelia.nix

@@ -464,7 +464,7 @@ let
         ''
     );
 
-  oidcClientSecrets = import ./lib/oidc-client-secrets.nix { };
+  oidcClientSecrets = import ./lib/oidc-client-secrets.nix { shell = lib.getExe pkgs.bash; };
 
   # Every client with a secret to mint: a native client is public and has none.
   secretClients = lib.filter (c: c.kind != "native") cfg.oidc.clients;

nix/script-tests/oidc-client-secrets.nix

@@ -74,13 +74,13 @@ let
     esac
   '';
 
-  # Runs the command it is given, as util-linux's `script -qec <cmd> /dev/null`
+  # Runs the command it is given with `$SHELL -c`, as util-linux's `script -qec <cmd> /dev/null`
   # does, without needing a pty in the build sandbox. The real pty is checked
   # against the real authelia by hand.
   fakeScript = pkgs.writeShellScriptBin "script" ''
     echo "script $1 $3" >> "$FAKE_AUTHELIA_LOG"
     [ "$1" = -qec ] || exit 99
-    exec ${pkgs.bash}/bin/bash -c "$2"
+    exec "$SHELL" -c "$2"
   '';
 in
 pkgs.runCommand "hyperhive-script-test-oidc-client-secrets"
@@ -88,7 +88,7 @@ pkgs.runCommand "hyperhive-script-test-oidc-client-secrets"
     HELPER = pkgs.writeText "oidc-client-secrets.sh" (
       import ../host-modules/lib/store-seeded-secret.nix { }
       + import ../host-modules/lib/atomic-write-secret.nix { }
-      + import ../host-modules/lib/oidc-client-secrets.nix { }
+      + import ../host-modules/lib/oidc-client-secrets.nix { shell = "${pkgs.bash}/bin/bash"; }
     );
     FAKE_BIN = pkgs.symlinkJoin {
       name = "fake-bao-and-authelia";

nix/script-tests/oidc-client-secrets.sh

@@ -28,6 +28,8 @@ setup() {
   : >"$FAKE_BAO_LOG"
   : >"$FAKE_AUTHELIA_LOG"
   clients=$dir/clients
+  printf '#!/bin/sh\necho "This account is currently not available." >&2\nexit 1\n' >"$dir/nologin"
+  chmod +x "$dir/nologin"
   digest=$clients/$id.digest
   legacy=$clients/$id.secret
   stored=$FAKE_BAO_KV/$(printf '%s' "$leaf" | tr / _)
@@ -35,11 +37,14 @@ setup() {
 
 # run <function> — the function for $id and $leaf, with the stubs first on
 # PATH, after the store login the units make first and, when $PREFETCH is set,
-# `store_prefetch` of the leaf. Sets $rc and $minted.
+# `store_prefetch` of the leaf. `SHELL` is a nologin stub, as the service
+# user's is. Sets $rc and $minted.
 run() {
   minted=$(
     set -e
     PATH="$FAKE_BIN/bin:$PATH"
+    SHELL=$dir/nologin
+    export SHELL
     unset BAO_TOKEN
     # shellcheck source=/dev/null
     . "$HELPER"
@@ -174,6 +179,13 @@ if [ "$(stat -c %a "$digest")" != 600 ]; then fail "digest mode is $(stat -c %a
 if ! logged "oidc client $id: wrote the digest from the secret in the store"; then fail "no info line"; fi
 no_secret_in_argv
 
+setup "mint: the digest is computed although the login shell is nologin"
+printf 'old-secret' >"$stored"
+run mint_client_secret
+expect 0
+digest_is digest-of-old-secret
+if grep -q "not available" "$dir/err" "$dir/out"; then fail "the nologin shell ran"; fi
+
 setup "mint: a plaintext file the store lacks seeds the store once, mints nothing and keeps the digest and the file"
 printf 'old-secret\n' >"$legacy"
 printf 'old-digest\n' >"$digest"