Re: Re: CVE-2014-6271: remote code execution through bash (3rd vulnerability)

[christos () zoulas com (Christos Zoulas)]

On Sep 26,  1:47pm, john.haxby () oracle com (John Haxby) wrote:
-- Subject: Re: [oss-security] Re: CVE-2014-6271: remote code execution throu

| It's not so much the known attacks -- redefining ls, unset, command,
| typeset, declare, etc -- it's the future parser bugs that we don't yet
| know about.
| 
| A friend of mine said this could be a vulnerability gift that keeps on
| giving.

I think that at this point the conservative approach is best, so
until the bash author figures what the best solution is, the feature
is disabled by default for NetBSD. It is not wise to expose bash's
parser to the internet and then debug it live while being attacked.

christos

$NetBSD: patch-shell.c,v 1.1 2014/09/25 20:28:32 christos Exp $

Add flag to disable importing of function unless explicitly enabled

--- shell.c.christos    2014-01-14 08:04:32.000000000 -0500
+++ shell.c     2014-09-25 16:11:51.000000000 -0400
@@ -229,6 +229,7 @@
 #else
 int posixly_correct = 0;       /* Non-zero means posix.2 superset. */
 #endif
+int import_functions = 0;      /* Import functions from environment */
 
 /* Some long-winded argument names.  These are obviously new. */
 #define Int 1
@@ -248,6 +249,7 @@
   { "help", Int, &want_initial_help, (char **)0x0 },
   { "init-file", Charp, (int *)0x0, &bashrc_file },
   { "login", Int, &make_login_shell, (char **)0x0 },
+  { "import-functions", Int, &import_functions, (char **)0x0 },
   { "noediting", Int, &no_line_editing, (char **)0x0 },
   { "noprofile", Int, &no_profile, (char **)0x0 },
   { "norc", Int, &no_rc, (char **)0x0 },

$NetBSD: patch-variables.c,v 1.1 2014/09/25 20:28:32 christos Exp $

Only read functions from environment if flag is set.

--- variables.c.christos        2014-09-25 16:09:41.000000000 -0400
+++ variables.c 2014-09-25 16:12:10.000000000 -0400
@@ -105,6 +105,7 @@
 extern int assigning_in_environment;
 extern int executing_builtin;
 extern int funcnest_max;
+extern int import_functions;
 
 #if defined (READLINE)
 extern int no_line_editing;
@@ -349,7 +350,7 @@
 
       /* If exported function, define it now.  Don't import functions from
         the environment in privileged mode. */
-      if (privmode == 0 && read_but_dont_execute == 0 && STREQN ("() {", string, 4))
+      if (import_functions && privmode == 0 && read_but_dont_execute == 0 && STREQN ("() {", string, 4))
        {
          string_length = strlen (string);
          temp_string = (char *)xmalloc (3 + string_length + char_index);