From de0c7743e0cd6f9daf90a0dc9d0629dd63c50b65 Mon Sep 17 00:00:00 2001
From: Henning Westerholt <hw@skalatan.de>
Date: Thu, 3 Oct 2019 17:52:37 +0200
Subject: [PATCH] core: add small wrappers around cryptographic PRNG with an
 interface like fastrand

---
 src/core/rand/cryptorand.c | 53 ++++++++++++++++++++++++++++++++++++++
 src/core/rand/cryptorand.h | 33 ++++++++++++++++++++++++
 2 files changed, 86 insertions(+)
 create mode 100644 src/core/rand/cryptorand.c
 create mode 100644 src/core/rand/cryptorand.h

diff --git a/src/core/rand/cryptorand.c b/src/core/rand/cryptorand.c
new file mode 100644
index 00000000000..469e986b16d
--- /dev/null
+++ b/src/core/rand/cryptorand.c
@@ -0,0 +1,53 @@
+/*
+ * cryptographic secure pseudo random generation
+ *
+ * Copyright (C) 2019 Henning Westerholt
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/* wrapper around fortuna cryptographic pseudo random number generator
+ * https://en.wikipedia.org/wiki/Fortuna_(PRNG)
+ */
+
+#include "cryptorand.h"
+
+#include "fortuna/random.h"
+#include "../dprint.h"
+
+/* seed the generator, will also use system randomness */
+void cryptorand_seed(const unsigned int seed) {
+	u_int8_t bytes[4];
+	
+	bytes[0] = (seed >> 24) & 0xFF;
+	bytes[1] = (seed >> 16) & 0xFF;
+	bytes[2] = (seed >> 8)  & 0xFF;
+	bytes[3] = seed & 0xFF;
+
+	LM_DBG("seeding cryptorand generator with %u\n", seed);
+	sr_add_entropy(bytes, 4);
+}
+
+/* generate a 32 bit random number */
+unsigned int cryptorand(void) {
+	u_int8_t bytes[4];
+	u_int32_t result = 0;
+	
+	sr_get_pseudo_random_bytes(bytes, 4);
+	result |= (u_int32_t)bytes[0] << 24;
+	result |= (u_int32_t)bytes[1] << 16;
+	result |= (u_int32_t)bytes[2] << 8;
+	result |= (u_int32_t)bytes[3];
+	
+	return result;
+}
+
diff --git a/src/core/rand/cryptorand.h b/src/core/rand/cryptorand.h
new file mode 100644
index 00000000000..08cb5a3e642
--- /dev/null
+++ b/src/core/rand/cryptorand.h
@@ -0,0 +1,33 @@
+/*
+ * cryptographic secure pseudo random generation
+ *
+ * Copyright (C) 2019 Henning Westerholt
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/* wrapper around fortuna cryptographic pseudo random number generator
+ * https://en.wikipedia.org/wiki/Fortuna_(PRNG)
+ */
+
+#ifndef _cryptorand_h
+#define _cryptorand_h
+
+#include <sys/types.h>
+
+/* seed the generator, will also use system randomness */
+void cryptorand_seed(const unsigned int seed);
+
+/* generate a 32 bit random number */
+unsigned int cryptorand(void);
+
+#endif