feat: add file env support for secrets

config/runtime.exs

@@ -7,6 +7,75 @@ import Config
 # any compile-time configuration in here, as it won't be applied.
 # The block below contains prod specific runtime configuration.
 
+# Helper function to read environment variables with Docker secrets support.
+# Supports the _FILE suffix pattern: if VAR_FILE is set, reads the value from
+# that file path. Otherwise falls back to VAR directly.
+# VAR_FILE takes priority and must contain the full absolute path to the secret file.
+get_env_or_file = fn var_name, default ->
+  file_var = "#{var_name}_FILE"
+
+  case System.get_env(file_var) do
+    nil ->
+      System.get_env(var_name, default)
+
+    file_path ->
+      case File.read(file_path) do
+        {:ok, content} ->
+          String.trim(content)
+
+        {:error, reason} ->
+          raise """
+          Failed to read secret from file specified in #{file_var}="#{file_path}".
+          Error: #{inspect(reason)}
+          """
+      end
+  end
+end
+
+# Same as get_env_or_file but raises if the value is not set
+get_env_or_file! = fn var_name, error_message ->
+  case get_env_or_file.(var_name, nil) do
+    nil -> raise error_message
+    value -> value
+  end
+end
+
+# Build database URL from individual components or use DATABASE_URL directly.
+# Supports both approaches:
+# 1. DATABASE_URL (or DATABASE_URL_FILE) - full connection URL
+# 2. Separate vars: DATABASE_HOST, DATABASE_USER, DATABASE_PASSWORD (or _FILE), DATABASE_NAME, DATABASE_PORT
+build_database_url = fn ->
+  case get_env_or_file.("DATABASE_URL", nil) do
+    nil ->
+      # Build URL from separate components
+      host =
+        System.get_env("DATABASE_HOST") ||
+          raise "DATABASE_HOST is required when DATABASE_URL is not set"
+
+      user =
+        System.get_env("DATABASE_USER") ||
+          raise "DATABASE_USER is required when DATABASE_URL is not set"
+
+      password =
+        get_env_or_file!.("DATABASE_PASSWORD", """
+        DATABASE_PASSWORD or DATABASE_PASSWORD_FILE is required when DATABASE_URL is not set.
+        """)
+
+      database =
+        System.get_env("DATABASE_NAME") ||
+          raise "DATABASE_NAME is required when DATABASE_URL is not set"
+
+      port = System.get_env("DATABASE_PORT", "5432")
+
+      # URL-encode the password to handle special characters
+      encoded_password = URI.encode_www_form(password)
+      "ecto://#{user}:#{encoded_password}@#{host}:#{port}/#{database}"
+
+    url ->
+      url
+  end
+end
+
 # ## Using releases
 #
 # If you use `mix release`, you need to explicitly enable the server
@@ -21,12 +90,7 @@ if System.get_env("PHX_SERVER") do
 end
 
 if config_env() == :prod do
-  database_url =
-    System.get_env("DATABASE_URL") ||
-      raise """
-      environment variable DATABASE_URL is missing.
-      For example: ecto://USER:PASS@HOST/DATABASE
-      """
+  database_url = build_database_url.()
 
   maybe_ipv6 = if System.get_env("ECTO_IPV6") in ~w(true 1), do: [:inet6], else: []
 
@@ -41,12 +105,12 @@ if config_env() == :prod do
   # want to use a different value for prod and you most likely don't want
   # to check this value into version control, so we use an environment
   # variable instead.
+  # Supports SECRET_KEY_BASE or SECRET_KEY_BASE_FILE for Docker secrets.
   secret_key_base =
-    System.get_env("SECRET_KEY_BASE") ||
-      raise """
-      environment variable SECRET_KEY_BASE is missing.
-      You can generate one by calling: mix phx.gen.secret
-      """
+    get_env_or_file!.("SECRET_KEY_BASE", """
+    environment variable SECRET_KEY_BASE (or SECRET_KEY_BASE_FILE) is missing.
+    You can generate one by calling: mix phx.gen.secret
+    """)
 
   host = System.get_env("PHX_HOST") || raise "Please define the PHX_HOST environment variable."
   port = String.to_integer(System.get_env("PORT") || "4000")
@@ -54,21 +118,22 @@ if config_env() == :prod do
   config :mv, :dns_cluster_query, System.get_env("DNS_CLUSTER_QUERY")
 
   # Rauthy OIDC configuration
+  # Supports OIDC_CLIENT_SECRET or OIDC_CLIENT_SECRET_FILE for Docker secrets.
   config :mv, :rauthy,
     client_id: System.get_env("OIDC_CLIENT_ID") || "mv",
     base_url: System.get_env("OIDC_BASE_URL") || "http://localhost:8080/auth/v1",
-    client_secret: System.get_env("OIDC_CLIENT_SECRET"),
+    client_secret: get_env_or_file.("OIDC_CLIENT_SECRET", nil),
     redirect_uri:
       System.get_env("OIDC_REDIRECT_URI") || "http://#{host}:#{port}/auth/user/rauthy/callback"
 
   # Token signing secret from environment variable
   # This overrides the placeholder value set in prod.exs
+  # Supports TOKEN_SIGNING_SECRET or TOKEN_SIGNING_SECRET_FILE for Docker secrets.
   token_signing_secret =
-    System.get_env("TOKEN_SIGNING_SECRET") ||
-      raise """
-      environment variable TOKEN_SIGNING_SECRET is missing.
-      You can generate one by calling: mix phx.gen.secret
-      """
+    get_env_or_file!.("TOKEN_SIGNING_SECRET", """
+    environment variable TOKEN_SIGNING_SECRET (or TOKEN_SIGNING_SECRET_FILE) is missing.
+    You can generate one by calling: mix phx.gen.secret
+    """)
 
   config :mv, :token_signing_secret, token_signing_secret