disorder-choose now uses an arcfour keystream as its RNG instead of

[disorder] / lib / random.c

diff --git a/lib/random.c b/lib/random.c
new file mode 100644 (file)
index 0000000..70e19f8
--- /dev/null
+++ b/lib/random.c
@@ -0,0 +1,85 @@
+/*
+ * This file is part of DisOrder
+ * Copyright (C) 2008 Richard Kettlewell
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+ * USA
+ */
+
+/** @file lib/random.c
+ * @brief Random number generator
+ *
+ */
+
+#include <config.h>
+#include "types.h"
+
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+
+#include "random.h"
+#include "log.h"
+#include "arcfour.h"
+
+static int random_count;
+static int random_fd = -1;
+static arcfour_context random_ctx[1];
+
+/** @brief Rekey the RNG
+ *
+ * Resets the RNG's key to a random one read from /dev/urandom
+ */
+static void random__rekey(void) {
+  char key[128];
+  int n;
+
+  if(random_fd < 0) {
+    if((random_fd = open("/dev/urandom", O_RDONLY)) < 0)
+      fatal(errno, "opening /dev/urandom");
+  }
+  if((n = read(random_fd, key, sizeof key)) < 0)
+    fatal(errno, "reading from /dev/urandom");
+  if((size_t)n < sizeof key)
+    fatal(0, "reading from /dev/urandom: short read");
+  arcfour_setkey(random_ctx, key, sizeof key);
+  random_count = 8 * 1024 * 1024;
+}
+
+/** @brief Get random bytes
+ * @param ptr Where to put random bytes
+ * @param bytes How many random bytes to generate
+ */
+void random_get(uint8_t *ptr, size_t bytes) {
+  if(random_count == 0)
+    random__rekey();
+  /* Encrypting 0s == just returning the keystream */
+  memset(ptr, 0, bytes);
+  arcfour_stream(random_ctx, (char *)ptr, (char *)ptr, bytes);
+  if(bytes > (size_t)random_count)
+    random_count = 0;
+  else
+    random_count -= bytes;
+}
+
+/*
+Local Variables:
+c-basic-offset:2
+comment-column:40
+fill-column:79
+indent-tabs-mode:nil
+End:
+*/