http://www.openwall.com/lists/oss-security/2014/09/25/13

current bash func export behavior does:
	foo='() { ... }'
which will set up a func named "foo" in the env

after this patch, it will look like:
	BASH_FUNC_foo()='() { ... }'

this prevents collisions with random env vars by having a clear prefix and
by using an invalid name (ends with "()").

--- a/variables.c	2014-09-25 13:07:59.313209541 +0200
+++ b/variables.c	2014-09-25 13:15:29.869420719 +0200
@@ -268,7 +268,7 @@
 static void propagate_temp_var __P((PTR_T));
 static void dispose_temporary_env __P((sh_free_func_t *));     
 
-static inline char *mk_env_string __P((const char *, const char *));
+static inline char *mk_env_string __P((const char *, const char *, int));
 static char **make_env_array_from_var_list __P((SHELL_VAR **));
 static char **make_var_export_array __P((VAR_CONTEXT *));
 static char **make_func_export_array __P((void));
@@ -301,6 +301,14 @@
 #endif
 }
 
+/* Prefix and suffix for environment variable names which contain
+   shell functions. */
+#define FUNCDEF_PREFIX "BASH_FUNC_"
+#define FUNCDEF_PREFIX_LEN (strlen (FUNCDEF_PREFIX))
+#define FUNCDEF_SUFFIX "()"
+#define FUNCDEF_SUFFIX_LEN (strlen (FUNCDEF_SUFFIX))
+
+
 /* Initialize the shell variables from the current environment.
    If PRIVMODE is nonzero, don't import functions from ENV or
    parse $SHELLOPTS. */
@@ -338,27 +346,39 @@
 
       /* 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))
-	{
-	  string_length = strlen (string);
-	  temp_string = (char *)xmalloc (3 + string_length + char_index);
+      if (privmode == 0 && read_but_dont_execute == 0
+	  && STREQN (FUNCDEF_PREFIX, name, FUNCDEF_PREFIX_LEN)
+	  && STREQ (name + char_index - FUNCDEF_SUFFIX_LEN, FUNCDEF_SUFFIX)
+	  && STREQN ("() {", string, 4))
+	{
+	  size_t name_length
+	    = char_index - (FUNCDEF_PREFIX_LEN + FUNCDEF_SUFFIX_LEN);
+	  char *temp_name = name + FUNCDEF_PREFIX_LEN;
+	  /* Temporarily remove the suffix. */
+	  temp_name[name_length] = '\0';
 
-	  strcpy (temp_string, name);
-	  temp_string[char_index] = ' ';
-	  strcpy (temp_string + char_index + 1, string);
+	  string_length = strlen (string);
+	  temp_string = (char *)xmalloc (name_length + 1 + string_length + 1);
+	  memcpy (temp_string, temp_name, name_length);
+	  temp_string[name_length] = ' ';
+	  memcpy (temp_string + name_length + 1, string, string_length + 1);
 
 	  /* Don't import function names that are invalid identifiers from the
 	     environment. */
-	  if (legal_identifier (name))
-	    parse_and_execute (temp_string, name, SEVAL_NONINT|SEVAL_NOHIST|SEVAL_FUNCDEF|SEVAL_ONECMD);
+	  if (legal_identifier (temp_name))
+	    parse_and_execute (temp_string, temp_name,
+			       SEVAL_NONINT|SEVAL_NOHIST|SEVAL_FUNCDEF|SEVAL_ONECMD);
 
-	  if (temp_var = find_function (name))
+	  if (temp_var = find_function (temp_name))
 	    {
 	      VSETATTR (temp_var, (att_exported|att_imported));
 	      array_needs_making = 1;
 	    }
 	  else
 	    report_error (_("error importing function definition for `%s'"), name);
+
+	  /* Restore the original suffix. */
+	  temp_name[name_length] = FUNCDEF_SUFFIX[0];
 	}
 #if defined (ARRAY_VARS)
 #  if 0
@@ -2537,7 +2557,7 @@
   var->context = variable_context;	/* XXX */
 
   INVALIDATE_EXPORTSTR (var);
-  var->exportstr = mk_env_string (name, value);
+  var->exportstr = mk_env_string (name, value, 0);
 
   array_needs_making = 1;
 
@@ -3388,22 +3408,43 @@
 /*								    */
 /* **************************************************************** */
 
+/* Returns the string NAME=VALUE if !FUNCTIONP or if VALUE == NULL (in
+   which case it is treated as empty).  Otherwise, decorate NAME with
+   FUNCDEF_PREFIX and FUNCDEF_SUFFIX, and return a string of the form
+   FUNCDEF_PREFIX NAME FUNCDEF_SUFFIX = VALUE (without spaces).  */
 static inline char *
-mk_env_string (name, value)
+mk_env_string (name, value, functionp)
      const char *name, *value;
+     int functionp;
 {
-  int name_len, value_len;
-  char	*p;
+  size_t name_len, value_len;
+  char *p, *q;
 
   name_len = strlen (name);
   value_len = STRLEN (value);
-  p = (char *)xmalloc (2 + name_len + value_len);
-  strcpy (p, name);
-  p[name_len] = '=';
+  if (functionp && value != NULL)
+    {
+      p = (char *)xmalloc (FUNCDEF_PREFIX_LEN + name_len + FUNCDEF_SUFFIX_LEN
+			   + 1 + value_len + 1);
+      q = p;
+      memcpy (q, FUNCDEF_PREFIX, FUNCDEF_PREFIX_LEN);
+      q += FUNCDEF_PREFIX_LEN;
+      memcpy (q, name, name_len);
+      q += name_len;
+      memcpy (q, FUNCDEF_SUFFIX, FUNCDEF_SUFFIX_LEN);
+      q += FUNCDEF_SUFFIX_LEN;
+    }
+  else
+    {
+      p = (char *)xmalloc (name_len + 1 + value_len + 1);
+      memcpy (p, name, name_len);
+      q = p + name_len;
+    }
+  q[0] = '=';
   if (value && *value)
-    strcpy (p + name_len + 1, value);
+    memcpy (q + 1, value, value_len + 1);
   else
-    p[name_len + 1] = '\0';
+    q[1] = '\0';
   return (p);
 }
 
@@ -3489,7 +3530,7 @@
 	  /* Gee, I'd like to get away with not using savestring() if we're
 	     using the cached exportstr... */
 	  list[list_index] = USE_EXPORTSTR ? savestring (value)
-					   : mk_env_string (var->name, value);
+	    : mk_env_string (var->name, value, function_p (var));
 
 	  if (USE_EXPORTSTR == 0)
 	    SAVE_EXPORTSTR (var, list[list_index]);