This is the much-discussed major upgrade to the random(4) device, known to you all as /dev/random.

This code has had an extensive rewrite and a good series of reviews, both by the author and other parties. This means a lot of code has been simplified. Pluggable structures for high-rate entropy generators are available, and it is most definitely not the case that /dev/random can be driven by only a hardware souce any more. This has been designed out of the device. Hardware sources are stirred into the CSPRNG (Yarrow, Fortuna) like any other entropy source. Pluggable modules may be written by third parties for additional sources.

The harvesting structures and consequently the locking have been simplified. Entropy harvesting is done in a more general way (the documentation for this will follow). There is some GREAT entropy to be had in the UMA allocator, but it is disabled for now as messing with that is likely to annoy many people.

The venerable (but effective) Yarrow algorithm, which is no longer supported by its authors now has an alternative, Fortuna. For now, Yarrow is retained as the default algorithm, but this may be changed using a kernel option. It is intended to make Fortuna the default algorithm for 11.0. Interested parties are encouraged to read ISBN 978-0-470-47424-2 "Cryptography Engineering" By Ferguson, Schneier and Kohno for Fortuna's gory details. Heck, read it anyway.

Many thanks to Arthur Mesh who did early grunt work, and who got caught in the crossfire rather more than he deserved to.

My thanks also to folks who helped me thresh this out on whiteboards and in the odd "Hallway track", or otherwise.

My Nomex pants are on. Let the feedback commence!

Reviewed by:	trasz,des(partial),imp(partial?),rwatson(partial?)
Approved by:	so(des)

1 files changed, 34 insertions, 6 deletions

diff --git a/sys/dev/random/random_harvestq.h b/sys/dev/random/random_harvestq.h
index a2ac3d1..ab09a3f 100644
--- a/sys/dev/random/random_harvestq.h
+++ b/sys/dev/random/random_harvestq.h
@@ -1,4 +1,5 @@
 /*-
+ * Copyright (c) 2013-2014 Mark R V Murray
  * Copyright (c) 2013 Arthur Mesh <arthurmesh@gmail.com>
  * All rights reserved.
  *
@@ -29,14 +30,41 @@
 #ifndef SYS_DEV_RANDOM_RANDOM_HARVESTQ_H_INCLUDED
 #define SYS_DEV_RANDOM_RANDOM_HARVESTQ_H_INCLUDED
 
-typedef void (*event_proc_f)(struct harvest *event);
+#define HARVESTSIZE	16	/* max size of each harvested entropy unit */
 
-void random_harvestq_init(event_proc_f);
+/* These are used to queue harvested packets of entropy. The entropy
+ * buffer size is pretty arbitrary.
+ */
+struct harvest_event {
+	uintmax_t			he_somecounter;		/* fast counter for clock jitter */
+	uint8_t				he_entropy[HARVESTSIZE];/* some harvested entropy */
+	u_int				he_size;		/* harvested entropy byte count */
+	u_int				he_bits;		/* stats about the entropy */
+	u_int				he_destination;		/* destination pool of this entropy */
+	enum random_entropy_source	he_source;		/* origin of the entropy */
+};
+
+void random_harvestq_init(void (*)(struct harvest_event *), int);
 void random_harvestq_deinit(void);
-void random_harvestq_internal(u_int64_t, const void *,
-    u_int, u_int, enum esource);
+void random_harvestq_internal(const void *, u_int, u_int, enum random_entropy_source);
+
+/* Pool count is used by anything needing to know how many entropy
+ * pools are currently being maintained.
+ * This is of use to (e.g.) the live source feed where we need to give
+ * all the pools a top-up.
+ */
+extern int harvest_pool_count;
+
+/* This is in randomdev.c as it needs to be permanently in the kernel */
+void randomdev_set_wakeup_exit(void *);
+
+/* Force all currently pending queue contents to clear, and kick the software processor */
+void random_harvestq_flush(void);
+
+/* Function called to process one harvested stochastic event */
+extern void (*harvest_process_event)(struct harvest_event *);
 
-extern int random_kthread_control;
-extern struct mtx harvest_mtx;
+/* Round-robin destination cache. */
+extern u_int harvest_destination[ENTROPYSOURCE];
 
 #endif /* SYS_DEV_RANDOM_RANDOM_HARVESTQ_H_INCLUDED */