1) example (partially humorous random_adaptor, that I call "EXAMPLE")

 * It's not meant to be used in a real system, it's there to show how
   the basics of how to create interfaces for random_adaptors. Perhaps
   it should belong in a manual page

2) Move probe.c's functionality in to random_adaptors.c
 * rename random_ident_hardware() to random_adaptor_choose()

3) Introduce a new way to choose (or select) random_adaptors via tunable
"rngs_want" It's a list of comma separated names of adaptors, ordered
by preferences. I.e.:
rngs_want="yarrow,rdrand"

Such setting would cause yarrow to be preferred to rdrand. If neither of
them are available (or registered), then system will default to
something reasonable (currently yarrow). If yarrow is not present, then
we fall back to the adaptor that's first on the list of registered
adaptors.

4) Introduce a way where RNGs can play a role of entropy source. This is
mostly useful for HW rngs.

The way I envision this is that every HW RNG will use this
functionality by default. Functionality to disable this is also present.
I have an example of how to use this in random_adaptor_example.c (see
modload event, and init function)

5) fix kern.random.adaptors from
kern.random.adaptors: yarrowpanicblock
to
kern.random.adaptors: yarrow,panic,block

6) add kern.random.active_adaptor to indicate currently selected
adaptor:
root@freebsd04:~ # sysctl kern.random.active_adaptor
kern.random.active_adaptor: yarrow

Submitted by:	Arthur Mesh <arthurmesh@gmail.com>

6 files changed, 351 insertions, 72 deletions

diff --git a/sys/dev/random/probe.c b/sys/dev/random/probe.c
deleted file mode 100644
index 7039b92606eb..000000000000
--- a/sys/dev/random/probe.c
+++ /dev/null
@@ -1,62 +0,0 @@
-/*-
- * Copyright (c) 2004 Mark R V Murray
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer
- *    in this position and unchanged.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
- * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
- * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
- * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- */
-
-#include <sys/cdefs.h>
-__FBSDID("$FreeBSD$");
-
-#if defined(__amd64__) || defined(__i386__)
-#include "opt_cpu.h"
-#endif
-
-#include <sys/param.h>
-#include <sys/systm.h>
-#include <sys/kernel.h>
-#include <sys/selinfo.h>
-
-#include <dev/random/random_adaptors.h>
-#include <dev/random/randomdev.h>
-
-void
-random_ident_hardware(struct random_adaptor **adaptor)
-{
-	struct random_adaptor *tmp;
-	int enable;
-
-	/* Set default to software (yarrow) */
-	*adaptor = random_adaptor_get("yarrow");
-
-	/* Then go looking for hardware */
-	enable = 1;
-	TUNABLE_INT_FETCH("hw.nehemiah_rng_enable", &enable);
-	if (enable && (tmp = random_adaptor_get("nehemiah")))
-		*adaptor = tmp;
-
-	enable = 1;
-	TUNABLE_INT_FETCH("hw.ivy_rng_enable", &enable);
-	if (enable && (tmp = random_adaptor_get("rdrand")))
-		*adaptor = tmp;
-}
diff --git a/sys/dev/random/pseudo_rng.c b/sys/dev/random/pseudo_rng.c
new file mode 100644
index 000000000000..13552942f795
--- /dev/null
+++ b/sys/dev/random/pseudo_rng.c
@@ -0,0 +1,119 @@
+/*-
+ * Copyright (c) 2013 Arthur Mesh <arthurmesh@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer
+ *    in this position and unchanged.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/time.h>
+#include <sys/kernel.h>
+#include <sys/module.h>
+#include <sys/selinfo.h>
+#include <sys/systm.h>
+
+#include <dev/random/random_adaptors.h>
+#include <dev/random/randomdev.h>
+
+static struct mtx	pseudo_random_block_mtx;
+
+static int
+pseudo_random_block_read(void *buf __unused, int c __unused)
+{
+
+	mtx_lock(&pseudo_random_block_mtx);
+
+	printf("random(4) device is blocking.\n");
+	msleep(pseudo_random_block_read, &pseudo_random_block_mtx, 0,
+	    "block", 0);
+
+	mtx_unlock(&pseudo_random_block_mtx);
+
+	return (0);
+}
+
+static void
+pseudo_random_block_init(void)
+{
+
+	mtx_init(&pseudo_random_block_mtx, "sleep mtx for random_block",
+	    NULL, MTX_DEF);
+}
+
+static void
+pseudo_random_block_deinit(void)
+{
+
+	mtx_destroy(&pseudo_random_block_mtx);
+}
+
+struct random_adaptor pseudo_random_block = {
+	.ident = "pseudo-RNG that always blocks",
+	.init = pseudo_random_block_init,
+	.deinit = pseudo_random_block_deinit,
+	.read = pseudo_random_block_read,
+	.write = (random_write_func_t *)random_null_func,
+	.reseed = (random_reseed_func_t *)random_null_func,
+	.seeded = 1,
+};
+
+static int
+pseudo_random_panic_read(void *buf, int c)
+{
+
+	panic("Insert a witty panic msg in here.");
+
+	return (0);
+}
+
+struct random_adaptor pseudo_random_panic = {
+	.ident = "pseudo-RNG that always panics on first read(2)",
+	.init = (random_init_func_t *)random_null_func,
+	.deinit = (random_deinit_func_t *)random_null_func,
+	.read = pseudo_random_panic_read,
+	.write = (random_write_func_t *)random_null_func,
+	.reseed = (random_reseed_func_t *)random_null_func,
+	.seeded = 1,
+};
+
+static int
+pseudo_random_modevent(module_t mod, int type, void *unused)
+{
+
+	switch (type) {
+	case MOD_LOAD:
+		random_adaptor_register("block", &pseudo_random_block);
+		EVENTHANDLER_INVOKE(random_adaptor_attach,
+		    &pseudo_random_block);
+
+		random_adaptor_register("panic", &pseudo_random_panic);
+
+		return (0);
+	}
+
+	return (EINVAL);
+}
+
+RANDOM_ADAPTOR_MODULE(pseudo, pseudo_random_modevent, 1);
diff --git a/sys/dev/random/random_adaptors.c b/sys/dev/random/random_adaptors.c
index c187bdb7fcfe..b017993c1ecc 100644
--- a/sys/dev/random/random_adaptors.c
+++ b/sys/dev/random/random_adaptors.c
@@ -1,6 +1,7 @@
 /*-
  * Copyright (c) 2013 Arthur Mesh <arthurmesh@gmail.com>
  * Copyright (c) 2013 David E. O'Brien <obrien@NUXI.org>
+ * Copyright (c) 2004 Mark R V Murray
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -30,16 +31,20 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/kernel.h>
 #include <sys/systm.h>
+#include <sys/kthread.h>
 #include <sys/lock.h>
+#include <sys/random.h>
 #include <sys/selinfo.h>
 #include <sys/sysctl.h>
 #include <sys/sx.h>
 #include <sys/malloc.h>
 #include <sys/queue.h>
 #include <sys/libkern.h>
+#include <sys/unistd.h>
 
-#include <dev/random/random_adaptors.h>
 #include <dev/random/randomdev.h>
+#include <dev/random/randomdev_soft.h>
+#include <dev/random/random_adaptors.h>
 
 LIST_HEAD(adaptors_head, random_adaptors);
 static struct adaptors_head adaptors = LIST_HEAD_INITIALIZER(adaptors);
@@ -50,6 +55,11 @@ static struct sysctl_ctx_list random_clist;
 
 MALLOC_DEFINE(M_RANDOM_ADAPTORS, "random_adaptors", "Random adaptors buffers");
 
+struct entropy_thread_ctx {
+	 struct random_adaptor   *adaptor;
+	 int			 *control;
+};
+
 int
 random_adaptor_register(const char *name, struct random_adaptor *rsp)
 {
@@ -57,7 +67,8 @@ random_adaptor_register(const char *name, struct random_adaptor *rsp)
 
 	KASSERT(name != NULL && rsp != NULL, ("invalid input to %s", __func__));
 
-	rpp = malloc(sizeof(struct random_adaptors), M_RANDOM_ADAPTORS, M_WAITOK);
+	rpp = malloc(sizeof(struct random_adaptors), M_RANDOM_ADAPTORS,
+	    M_WAITOK);
 	rpp->name = name;
 	rpp->rsp = rsp;
 
@@ -87,6 +98,159 @@ random_adaptor_get(const char *name)
 	return (rsp);
 }
 
+/*
+ * In the past, the logic of the random_adaptor selection was inverted, such
+ * that hardware RNGs would be chosen unless disabled. This routine is here to
+ * preserve that functionality to avoid folks losing their hardware RNGs by
+ * upgrading to newer kernel.
+ */
+static void
+random_adaptor_choose_legacy(struct random_adaptor **adaptor)
+{
+	struct random_adaptor *tmp;
+	int enable;
+
+	/* Then go looking for hardware */
+	enable = 1;
+	TUNABLE_INT_FETCH("hw.nehemiah_rng_enable", &enable);
+	if (enable && (tmp = random_adaptor_get("nehemiah")))
+		*adaptor = tmp;
+
+	enable = 1;
+	TUNABLE_INT_FETCH("hw.ivy_rng_enable", &enable);
+	if (enable && (tmp = random_adaptor_get("rdrand")))
+		*adaptor = tmp;
+}
+
+/*
+ * Walk a list of registered random(4) adaptors and pick the last non-selected
+ * one.
+ *
+ * If none are selected, use yarrow if available.
+ */
+void
+random_adaptor_choose(struct random_adaptor **adaptor)
+{
+	char			 rngs[128], *token, *cp;
+	struct random_adaptors  *rpp;
+
+	KASSERT(adaptor != NULL, ("pre-conditions failed"));
+
+	*adaptor = NULL;
+
+	random_adaptor_choose_legacy(adaptor);
+
+	if (*adaptor != NULL)
+		return;
+
+	if (TUNABLE_STR_FETCH("rngs_want", rngs, sizeof(rngs))) {
+		cp = rngs;
+
+		while ((token = strsep(&cp, ",")) != NULL) {
+			if ((*adaptor = random_adaptor_get(token)) != NULL)
+				break;
+			else if (bootverbose)
+				printf(
+			    "%s random adaptor is not available, skipping\n",
+				    token);
+		}
+	}
+
+	if (*adaptor == NULL) {
+		/*
+		 * Either no RNGs are prefered via rngs_want tunable, or
+		 * no prefered RNGs are registered.
+		 * Fallback to Yarrow.
+		 */
+		*adaptor = random_adaptor_get("yarrow");
+
+		if (*adaptor == NULL) {
+			/*
+			 * Yarrow doesn't seem to be available.
+			 * Fallback to the first thing that's on the list of
+			 * available RNGs.
+			 */
+			sx_slock(&adaptors_lock);
+
+			rpp = LIST_FIRST(&adaptors);
+			if (rpp != NULL)
+				*adaptor = rpp->rsp;
+
+			sx_sunlock(&adaptors_lock);
+		}
+
+		if (bootverbose && *adaptor)
+			printf("Falling back to <%s> random adaptor",
+			    (*adaptor)->ident);
+	}
+}
+
+static void
+random_proc(void *arg)
+{
+	struct entropy_thread_ctx *ctx;
+	u_char randomness[HARVESTSIZE];
+	int i;
+
+	ctx = (struct entropy_thread_ctx *)arg;
+
+	/* Sanity check. */
+	if (ctx->adaptor == NULL || ctx->adaptor->read == NULL)
+		return;
+
+	for (; *ctx->control == 0;) {
+		i = ctx->adaptor->read(randomness, sizeof(randomness));
+
+		if (i > 0)
+			/* Be very conservative with entropy estimation here. */
+			random_harvest(randomness, i, 0, 0, RANDOM_PURE);
+
+		/* Wake up every 10 secs. */
+		tsleep_sbt(ctx->adaptor, PWAIT | PCATCH, "-", SBT_1M / 6, 0, 0);
+	}
+
+	printf("<%s> entropy source is exiting\n", ctx->adaptor->ident);
+	free(ctx, M_RANDOM_ADAPTORS);
+	kproc_exit(0);
+}
+
+/*
+ * Use RNG's output as an entropy source for another RNG. i.e.:
+ * +--------+          +--------+
+ * | Intel  |          | Yarrow |
+ * | RDRAND +--------->|        |
+ * +--------+          +--------+
+ * Very useful for seeding software RNGs with output of
+ * Hardware RNGs like Intel's RdRand and VIA's Padlock.
+ *
+ * Returns a handle to the newly created kernel process.
+ */
+void *
+random_adaptor_use_as_entropy(const char *id, struct random_adaptor *adaptor,
+    int *control)
+{
+	int error;
+	struct proc *random_chain_proc;
+	struct entropy_thread_ctx *ctx;
+
+	KASSERT(adaptor != NULL, ("can't obtain randomness"));
+	KASSERT(control != NULL, ("can't control entropy process"));
+
+	ctx = malloc(sizeof(struct entropy_thread_ctx), M_RANDOM_ADAPTORS,
+	    M_WAITOK);
+
+	ctx->control = control;
+	ctx->adaptor = adaptor;
+
+	/* Start the thread */
+	error = kproc_create(random_proc, ctx, &random_chain_proc, RFHIGHPID,
+	    0, "%s_entropy", id);
+	if (error != 0)
+		panic("Cannot create rng chaining thread");
+
+	return random_chain_proc;
+}
+
 static void
 random_adaptors_deinit(void *unused)
 {
@@ -99,18 +263,28 @@ static int
 random_sysctl_adaptors_handler(SYSCTL_HANDLER_ARGS)
 {
 	struct random_adaptors	*rpp;
-	int error;
+	int error, count;
 
-	error = 0;
+	count = error = 0;
 
 	sx_slock(&adaptors_lock);
 
-	if (LIST_EMPTY(&adaptors))
-		error = SYSCTL_OUT(req, "", strlen(""));
+	if (LIST_EMPTY(&adaptors)) {
+		error = SYSCTL_OUT(req, "", 0);
+	} else {
+
+		LIST_FOREACH(rpp, &adaptors, entries) {
+
+			error = SYSCTL_OUT(req, ",", count++ ? 1 : 0);
+
+			if (error)
+				break;
+
+			error = SYSCTL_OUT(req, rpp->name, strlen(rpp->name));
 
-	LIST_FOREACH(rpp, &adaptors, entries) {
-		if (0 != SYSCTL_OUT(req, rpp->name, strlen(rpp->name)))
-			break;
+			if (error)
+				break;
+		}
 	}
 
 	sx_sunlock(&adaptors_lock);
@@ -118,6 +292,37 @@ random_sysctl_adaptors_handler(SYSCTL_HANDLER_ARGS)
 	return (error);
 }
 
+static int
+random_sysctl_active_adaptor_handler(SYSCTL_HANDLER_ARGS)
+{
+	struct random_adaptor	*rsp;
+	struct random_adaptors	*rpp;
+	const char		*name;
+	int error;
+
+	name = NULL;
+	rsp = random_get_active_adaptor();
+
+	if (rsp != NULL) {
+		sx_slock(&adaptors_lock);
+
+		LIST_FOREACH(rpp, &adaptors, entries) {
+			if (rpp->rsp == rsp)
+				name = rpp->name;
+		}
+
+		sx_sunlock(&adaptors_lock);
+	}
+
+	if (rsp == NULL || name == NULL) {
+		error = SYSCTL_OUT(req, "", 0);
+	} else {
+		error = SYSCTL_OUT(req, name, strlen(name));
+	}
+
+	return (error);
+}
+
 static void
 random_adaptors_init(void *unused)
 {
@@ -127,6 +332,11 @@ random_adaptors_init(void *unused)
 	    NULL, 0, random_sysctl_adaptors_handler, "",
 	    "Random Number Generator adaptors");
 
+	SYSCTL_PROC(_kern_random, OID_AUTO, active_adaptor,
+	    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
+	    NULL, 0, random_sysctl_active_adaptor_handler, "",
+	    "Active Random Number Generator Adaptor");
+
 	sx_init(&adaptors_lock, "random_adaptors");
 }
 
diff --git a/sys/dev/random/random_adaptors.h b/sys/dev/random/random_adaptors.h
index 50a7a0fea017..b3038e750620 100644
--- a/sys/dev/random/random_adaptors.h
+++ b/sys/dev/random/random_adaptors.h
@@ -39,6 +39,9 @@ struct random_adaptors {
 
 struct random_adaptor *random_adaptor_get(const char *);
 int random_adaptor_register(const char *, struct random_adaptor *);
+void random_adaptor_choose(struct random_adaptor **);
+void *random_adaptor_use_as_entropy(const char *, struct random_adaptor *,
+    int *);
 
 /*
  * random_adaptor's should be registered prior to
diff --git a/sys/dev/random/randomdev.c b/sys/dev/random/randomdev.c
index d18641fe3098..850948ee9627 100644
--- a/sys/dev/random/randomdev.c
+++ b/sys/dev/random/randomdev.c
@@ -51,6 +51,7 @@ __FBSDID("$FreeBSD$");
 #include <machine/bus.h>
 #include <machine/cpu.h>
 
+#include <dev/random/random_adaptors.h>
 #include <dev/random/randomdev.h>
 
 #define RANDOM_MINOR	0
@@ -85,6 +86,13 @@ random_null_func(void)
 {
 }
 
+struct random_adaptor *
+random_get_active_adaptor(void)
+{ 
+
+	return (random_adaptor);
+}
+
 /* ARGSUSED */
 static int
 random_close(struct cdev *dev __unused, int flags, int fmt __unused,
@@ -215,7 +223,7 @@ random_modevent(module_t mod __unused, int type, void *data __unused)
 
 	switch (type) {
 	case MOD_LOAD:
-		random_ident_hardware(&random_adaptor);
+		random_adaptor_choose(&random_adaptor);
 
 		if (random_adaptor == NULL) {
 			printf(
diff --git a/sys/dev/random/randomdev.h b/sys/dev/random/randomdev.h
index 75b2c1980901..aeb47531ae72 100644
--- a/sys/dev/random/randomdev.h
+++ b/sys/dev/random/randomdev.h
@@ -53,3 +53,4 @@ struct random_adaptor {
 
 extern void random_ident_hardware(struct random_adaptor **);
 extern void random_null_func(void);
+struct random_adaptor *random_get_active_adaptor(void);