diff -up hashalot-0.3/hashalot.c.orig hashalot-0.3/hashalot.c
--- hashalot-0.3/hashalot.c.orig	2009-02-11 19:31:16.000000000 -0600
+++ hashalot-0.3/hashalot.c	2009-02-11 19:47:46.000000000 -0600
@@ -34,6 +34,7 @@
 #include "sha512.h"
 
 #define PASSWDBUFFLEN 130
+#define MAXHASHLEN (ULONG_MAX/2 - 2)
 
 typedef int (*phash_func_t)(char dest[], size_t dest_len, const char src[], size_t src_len);
 
@@ -179,8 +180,7 @@ static void *
 xmalloc (size_t size) {
         void *p;
 
-        if (size == 0)
-                return NULL;
+        assert(size != 0);
 
         p = malloc(size);
         if (p == NULL) {
@@ -239,6 +239,12 @@ main(int argc, char *argv[])
 				show_usage(argv[0]);
 				exit(EXIT_FAILURE);
 			}
+			if (hashlen >= MAXHASHLEN) {
+				fprintf(stderr, 
+					"please supply a value smaller than %lu for the -n option\n",
+					MAXHASHLEN);
+				exit(EXIT_FAILURE);
+			}
 			break;
                 case 's':
                         salt = optarg;