From ddf2b3b84ca56f47f310448201cc14b0fcc606b8 Mon Sep 17 00:00:00 2001
From: Greg Hudson <ghudson@mit.edu>
Date: Fri, 25 Feb 2011 19:29:23 +0000
Subject: [PATCH] Add a non-default PRNG module which just retrieves entropy
 from /dev/urandom without any cryptographic post-processing.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@24664 dc483132-0cff-0310-8789-dd5450dbe970
---
 src/lib/crypto/krb/prng_os.c | 94 ++++++++++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 src/lib/crypto/krb/prng_os.c

diff --git a/src/lib/crypto/krb/prng_os.c b/src/lib/crypto/krb/prng_os.c
new file mode 100644
index 000000000..2da8b1986
--- /dev/null
+++ b/src/lib/crypto/krb/prng_os.c
@@ -0,0 +1,94 @@
+/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
+/* lib/crypto/krb/prng/fortuna/prng_os.c - OS-native PRNG implementation */
+/*
+ * Copyright (C) 2011 by the Massachusetts Institute of Technology.
+ * All rights reserved.
+ *
+ *
+ * Export of this software from the United States of America may require
+ * a specific license from the United States Government.  It is the
+ * responsibility of any person or organization contemplating export to
+ * obtain such a license before exporting.
+ *
+ * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
+ * distribute this software and its documentation for any purpose and
+ * without fee is hereby granted, provided that the above copyright
+ * notice appear in all copies and that both that copyright notice and
+ * this permission notice appear in supporting documentation, and that
+ * the name of M.I.T. not be used in advertising or publicity pertaining
+ * to distribution of the software without specific, written prior
+ * permission.  Furthermore if you modify this software you must label
+ * your software as modified software and not distribute it in such a
+ * fashion that it might be confused with the original M.I.T. software.
+ * M.I.T. makes no representations about the suitability of
+ * this software for any purpose.  It is provided "as is" without express
+ *  or implied warranty.
+ */
+
+/*
+ * This file implements a PRNG module which relies on the system's /dev/urandom
+ * device.  An OS packager can select this module given sufficient confidence
+ * in the operating system's native PRNG quality.
+ */
+
+#include "k5-int.h"
+#include "prng.h"
+
+#define DEVICE "/dev/urandom"
+
+static int fd = -1;
+
+int
+k5_prng_init(void)
+{
+    /* Try to open the random device read-write; if that fails, read-only is
+     * okay. */
+    fd = open(DEVICE, O_RDWR, 0);
+    if (fd == -1)
+	fd = open(DEVICE, O_RDONLY, 0);
+    if (fd == -1)
+	return errno;
+    return 0;
+}
+
+void
+k5_prng_cleanup(void)
+{
+    close(fd);
+    fd = -1;
+}
+
+krb5_error_code KRB5_CALLCONV
+krb5_c_random_add_entropy(krb5_context context, unsigned int randsource,
+                          const krb5_data *indata)
+{
+    krb5_error_code ret;
+
+    ret = krb5int_crypto_init();
+    if (ret)
+        return ret;
+
+    /* Some random devices let user-space processes contribute entropy.  Don't
+     * worry if this fails. */
+    (void)write(fd, indata->data, indata->length);
+    return 0;
+}
+
+krb5_error_code KRB5_CALLCONV
+krb5_c_random_make_octets(krb5_context context, krb5_data *outdata)
+{
+    char *buf = outdata->data;
+    size_t len = outdata->length;
+    ssize_t count;
+
+    while (len > 0) {
+	count = read(fd, buf, len);
+	if (count == 0)         /* Not expected from a random device. */
+	    return KRB5_CRYPTO_INTERNAL;
+	if (count == -1)
+	    return errno;
+	buf += count;
+	len -= count;
+    }
+    return 0;
+}
-- 
2.26.2