During libstrongswan initialization, check if memwipe() works as expected

diff --git a/src/libstrongswan/library.c b/src/libstrongswan/library.c
index 819c680..4dec612 100644 (file)
--- a/src/libstrongswan/library.c
+++ b/src/libstrongswan/library.c
@@ -150,6 +150,51 @@ static bool equals(char *a, char *b)
        return streq(a, b);
 }
 
+/**
+ * Write magic to memory, and try to clear it with memwipe()
+ */
+__attribute__((noinline))
+static void do_magic(int magic, int **stack)
+{
+       int buf[32], i;
+
+       /* tell caller where callee stack is (but don't point to buf) */
+       *stack = &i;
+       for (i = 0; i < countof(buf); i++)
+       {
+               buf[i] = magic;
+       }
+       /* passing buf to dbg should make sure the compiler can't optimize out buf.
+        * we use directly dbg(3), as DBG3() might be stripped with DEBUG_LEVEL. */
+       dbg(DBG_LIB, 3, "memwipe() pre: %b", buf, sizeof(buf));
+       memwipe(buf, sizeof(buf));
+}
+
+/**
+ * Check if memwipe works as expected
+ */
+static bool check_memwipe()
+{
+       int magic = 0xCAFEBABE, *ptr, *deeper, i, stackdir = 1;
+
+       do_magic(magic, &deeper);
+
+       ptr = &magic;
+       if (deeper < ptr)
+       {       /* stack grows down */
+               stackdir = -1;
+       }
+       for (i = 0; i < 128; i++)
+       {
+               ptr = ptr + stackdir;
+               if (*ptr == magic)
+               {
+                       return FALSE;
+               }
+       }
+       return TRUE;
+}
+
 /*
  * see header file
  */
@@ -221,6 +266,12 @@ bool library_init(char *settings)
        this->public.scheduler = scheduler_create();
        this->public.plugins = plugin_loader_create();
 
+       if (!check_memwipe())
+       {
+               DBG1(DBG_LIB, "memwipe() check failed");
+               return FALSE;
+       }
+
        if (lib->settings->get_bool(lib->settings,
                                                                "libstrongswan.integrity_test", FALSE))
        {
@@ -239,4 +290,3 @@ bool library_init(char *settings)
 
        return !this->integrity_failed;
 }
-