From 9c457c1f685a15af5ad305aa3d3db0e55b36afed Mon Sep 17 00:00:00 2001
From: Carsten <carsten@ravensburg.it>
Date: Tue, 21 Apr 2026 22:48:36 +0200
Subject: [PATCH] feat(server): Server.Auth.verify_password/1

---
 server/lib/server/auth.ex        | 16 ++++++++++++++++
 server/test/server/auth_test.exs | 28 ++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 server/lib/server/auth.ex
 create mode 100644 server/test/server/auth_test.exs

diff --git a/server/lib/server/auth.ex b/server/lib/server/auth.ex
new file mode 100644
index 0000000..1f2a8e8
--- /dev/null
+++ b/server/lib/server/auth.ex
@@ -0,0 +1,16 @@
+defmodule Server.Auth do
+  @moduledoc "Single-user dashboard authentication."
+
+  @spec verify_password(term()) :: :ok | :error
+  def verify_password(password) when is_binary(password) do
+    hash = Application.fetch_env!(:server, :dashboard_password_hash)
+
+    if Argon2.verify_pass(password, hash) do
+      :ok
+    else
+      :error
+    end
+  end
+
+  def verify_password(_), do: :error
+end
diff --git a/server/test/server/auth_test.exs b/server/test/server/auth_test.exs
new file mode 100644
index 0000000..cc60c73
--- /dev/null
+++ b/server/test/server/auth_test.exs
@@ -0,0 +1,28 @@
+defmodule Server.AuthTest do
+  use ExUnit.Case, async: true
+
+  alias Server.Auth
+
+  setup do
+    hash = Argon2.hash_pwd_salt("testpass")
+    prev = Application.get_env(:server, :dashboard_password_hash)
+    Application.put_env(:server, :dashboard_password_hash, hash)
+    on_exit(fn -> Application.put_env(:server, :dashboard_password_hash, prev) end)
+    :ok
+  end
+
+  describe "verify_password/1" do
+    test "returns :ok for correct password" do
+      assert Auth.verify_password("testpass") == :ok
+    end
+
+    test "returns :error for wrong password" do
+      assert Auth.verify_password("wrong") == :error
+    end
+
+    test "returns :error for non-binary input" do
+      assert Auth.verify_password(nil) == :error
+      assert Auth.verify_password(123) == :error
+    end
+  end
+end