apparmor-ofono: open a root-owned file

ofono runs as root, so having the "malicious" LD_PRELOAD module read
/home/user/.bash_history requires it to exercise CAP_DAC_OVERRIDE,
leading to an AppArmor denial that doesn't match what we expect. Try
to read /etc/shadow instead, and update the expected denials
accordingly.

With that change, there's no real need for the "malicious" code to use
GLib, so use stdio instead.

Apertis: https://phabricator.apertis.org/T1848



Signed-off-by: Frédéric Dalleau <frederic.dalleau@collabora.co.uk>
Reviewed-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D4388

apparmor/ofono/ofonod-malicious-override.c

-/* vim: set sts=4 sw=4 et :
+/* vim:set et sw=2 cin cino=t0,f0,(0,{s,>2s,n-s,^-s,e2s:
  *
  * A small library that can be loaded using LD_PRELOAD to do malicious things 
  * to test whether apparmor works
  */
 
-/* Easier for the build system */
-#include "../common/function-malicious-override.c"
+#define _GNU_SOURCE
+#include <dlfcn.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <glib.h>
+
+static void
+do_malicious_stuff (void)
+{
+  const char *filename = "/etc/shadow";
+
+  if (fopen (filename, "r") == NULL)
+    {
+      fprintf (stderr, "Unable to be malicious: %s -- SUCCESS\n",
+               strerror(errno));
+    }
+  else
+    {
+      fprintf (stderr, "Malicious code read contents of '%s' -- FAILURE\n",
+               filename);
+      /* Exit immediately if apparmor doesn't stop us. */
+      exit (EXIT_FAILURE);
+    }
+}
 
 gboolean
 g_option_context_parse            (GOptionContext      *context,

apparmor/ofono/ofonod.malicious.expected

@@ -3,5 +3,5 @@ profile:/usr/sbin/ofonod
 sdmode:REJECTING
 denied_mask:r
 operation:open
-name:/home/user/.bash_history
+name:/etc/shadow
 request_mask:r