From a49cd78aae3b85c8d97bf64420db3013e100c4db Mon Sep 17 00:00:00 2001
From: zmstone <zmstone@gmail.com>
Date: Mon, 29 Jul 2024 23:54:00 +0200
Subject: [PATCH] refactor: force getenv to access only OS env with prefix
 EMQXVAR_

---
 apps/emqx_utils/src/emqx_variform_bif.erl        | 2 +-
 apps/emqx_utils/test/emqx_variform_bif_tests.erl | 2 +-
 changes/ce/feat-13507.en.md                      | 6 ++++--
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/apps/emqx_utils/src/emqx_variform_bif.erl b/apps/emqx_utils/src/emqx_variform_bif.erl
index e66b8e47d..09048a697 100644
--- a/apps/emqx_utils/src/emqx_variform_bif.erl
+++ b/apps/emqx_utils/src/emqx_variform_bif.erl
@@ -583,7 +583,7 @@ getenv(Bin) when is_binary(Bin) ->
     EnvKey = ?ENV_CACHE(Bin),
     case persistent_term:get(EnvKey, undefined) of
         undefined ->
-            Name = erlang:binary_to_list(Bin),
+            Name = "EMQXVAR_" ++ erlang:binary_to_list(Bin),
             Result =
                 case os:getenv(Name) of
                     false ->
diff --git a/apps/emqx_utils/test/emqx_variform_bif_tests.erl b/apps/emqx_utils/test/emqx_variform_bif_tests.erl
index 36235be40..aa6724de5 100644
--- a/apps/emqx_utils/test/emqx_variform_bif_tests.erl
+++ b/apps/emqx_utils/test/emqx_variform_bif_tests.erl
@@ -77,5 +77,5 @@ system_test() ->
     EnvName = erlang:atom_to_list(?MODULE),
     EnvVal = erlang:atom_to_list(?FUNCTION_NAME),
     EnvNameBin = erlang:list_to_binary(EnvName),
-    os:putenv(EnvName, EnvVal),
+    os:putenv("EMQXVAR_" ++ EnvName, EnvVal),
     ?assertEqual(erlang:list_to_binary(EnvVal), emqx_variform_bif:getenv(EnvNameBin)).
diff --git a/changes/ce/feat-13507.en.md b/changes/ce/feat-13507.en.md
index 115fa49a9..026cf6bf4 100644
--- a/changes/ce/feat-13507.en.md
+++ b/changes/ce/feat-13507.en.md
@@ -1,2 +1,4 @@
-Added a new builtin function `getenv` in the rule engine and variform expression to access the environment variables.
-Note this value is immutable once loaded from the environment.
+Added a new builtin function `getenv` in the rule engine and variform expression to access the environment variables with below limitations.
+
+- Prefix `EMQXVAR_` is added before reading from OS environment variables. i.e. `getenv('FOO_BAR')` is to read `EMQXVAR_FOO_BAR`.
+- The values are immutable once loaded from the OS environment.