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-rw-r--r--gpxe/src/crypto/crandom.c55
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diff --git a/gpxe/src/crypto/crandom.c b/gpxe/src/crypto/crandom.c
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+/*
+ * Copyright (c) 2009 Joshua Oreman <oremanj@rwcr.net>.
+ *
+ * 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 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+/** @file
+ *
+ * Cryptographically strong random number generator
+ *
+ * Currently the cryptographic part is not implemented, and this just
+ * uses random().
+ */
+
+#include <gpxe/crypto.h>
+#include <stdlib.h>
+
+/**
+ * Get cryptographically strong random bytes
+ *
+ * @v buf Buffer in which to store random bytes
+ * @v len Number of random bytes to generate
+ *
+ * @b WARNING: This function is currently underimplemented, and does
+ * not give numbers any stronger than random()!
+ */
+void get_random_bytes ( void *buf, size_t len )
+{
+ u8 *bufp = buf;
+
+ /*
+ * Somewhat arbitrarily, choose the 0x00FF0000-masked byte
+ * returned by random() as having good entropy. PRNGs often
+ * don't provide good entropy in lower bits, and the top byte
+ * might show a pattern because of sign issues.
+ */
+
+ while ( len-- ) {
+ *bufp++ = ( random() >> 16 ) & 0xFF;
+ }
+}