From f72d4304f938fd0f39577f776ece2ae6cedebb08 Mon Sep 17 00:00:00 2001
From: Alexis Mousset <alexis.mousset@rudder.io>
Date: Thu, 14 Sep 2023 20:46:29 +0200
Subject: [PATCH] Allow inheriting attributes using global variables in bodies
 having local parameters.

This also prevents a memory corruption when
an attribute contains external vars but no
local vars.

Ticket: CFE-4254
Changelog: Bodies can now inherit attributes containing global variables

Signed-off-by: Alexis Mousset <alexis.mousset@rudder.io>
(cherry picked from commit a99a1ccc342bd6104c2503ff72f5c271e15ffa3a)
Signed-off-by: Lars Erik Wik <lars.erik.wik@northern.tech>
---
 libpromises/rlist.c                           | 14 ++++-
 .../03_bodies/inherit_from_with_global_var.cf | 55 +++++++++++++++++++
 2 files changed, 67 insertions(+), 2 deletions(-)
 create mode 100644 tests/acceptance/00_basics/03_bodies/inherit_from_with_global_var.cf

diff --git a/libpromises/rlist.c b/libpromises/rlist.c
index 64ea0e6ac4..27703dd786 100644
--- a/libpromises/rlist.c
+++ b/libpromises/rlist.c
@@ -373,13 +373,14 @@ Rval RvalNewRewriter(const void *item, RvalType type, JsonElement *map)
 
             Buffer *format = BufferNew();
             StringCopy(item, buffer_from, max_size);
+            buffer_to[0] = '\0';
 
             for (int iteration = 0; iteration < 10; iteration++)
             {
                 bool replacement_made = false;
                 int var_start = -1;
                 char closing_brace = 0;
-                for (int c = 0; c < buffer_from[c]; c++)
+                for (int c = 0; buffer_from[c] != '\0'; c++)
                 {
                     if (buffer_from[c] == '$')
                     {
@@ -402,6 +403,7 @@ Rval RvalNewRewriter(const void *item, RvalType type, JsonElement *map)
                     {
                         char saved = buffer_from[c];
                         buffer_from[c] = '\0';
+
                         const char *repl = JsonObjectGetAsString(map, buffer_from + var_start + 2);
                         buffer_from[c] = saved;
 
@@ -433,7 +435,15 @@ Rval RvalNewRewriter(const void *item, RvalType type, JsonElement *map)
                 }
             }
 
-            char *ret = xstrdup(buffer_to);
+            char* ret;
+            if (buffer_to[0] == '\0') {
+                // If nothing has been written to buffer_to, we pass the input verbatim.
+                // This function only evaluates body parameters, but the body can also reference the global
+                // context.
+                ret = xstrdup(buffer_from);
+            } else {
+                ret = xstrdup(buffer_to);
+            }
 
             BufferDestroy(format);
             free(buffer_to);
diff --git a/tests/acceptance/00_basics/03_bodies/inherit_from_with_global_var.cf b/tests/acceptance/00_basics/03_bodies/inherit_from_with_global_var.cf
new file mode 100644
index 0000000000..c9dec4f368
--- /dev/null
+++ b/tests/acceptance/00_basics/03_bodies/inherit_from_with_global_var.cf
@@ -0,0 +1,55 @@
+#######################################################
+#
+# Test that bodies can inherit attributes containing global variables
+#
+#######################################################
+
+body common control
+{
+      inputs => { "../../default.cf.sub" };
+      bundlesequence  => { default("$(this.promise_filename)") };
+      version => "1.0";
+}
+
+#######################################################
+
+
+bundle agent init
+{
+  vars:
+      "class" string => "_pass";
+}
+
+#######################################################
+
+body classes parent(p)
+{
+      promise_kept => { "${init.class}" };
+}
+
+body classes static(p)
+{
+      inherit_from => parent(p);
+}
+
+bundle agent test {
+  meta:
+    "description" -> { "CFE-4254" }
+      string => "Test that bodies can inherit attributes containing global variables";
+
+  vars:
+    "test" string => "test",
+          classes => static("placeholder");
+}
+
+#######################################################
+
+bundle agent check
+{
+  methods:
+    _pass:: 
+      "pass" usebundle => dcs_pass("$(this.promise_filename)");
+
+    !_pass::
+      "pass" usebundle => dcs_fail("$(this.promise_filename)");
+}