Huge cleanup of random(4) code.

* GENERAL
- Update copyright.
- Make kernel options for RANDOM_YARROW and RANDOM_DUMMY. Set
  neither to ON, which means we want Fortuna
- If there is no 'device random' in the kernel, there will be NO
  random(4) device in the kernel, and the KERN_ARND sysctl will
  return nothing. With RANDOM_DUMMY there will be a random(4) that
  always blocks.
- Repair kern.arandom (KERN_ARND sysctl). The old version went
  through arc4random(9) and was a bit weird.
- Adjust arc4random stirring a bit - the existing code looks a little
  suspect.
- Fix the nasty pre- and post-read overloading by providing explictit
  functions to do these tasks.
- Redo read_random(9) so as to duplicate random(4)'s read internals.
  This makes it a first-class citizen rather than a hack.
- Move stuff out of locked regions when it does not need to be
  there.
- Trim RANDOM_DEBUG printfs. Some are excess to requirement, some
  behind boot verbose.
- Use SYSINIT to sequence the startup.
- Fix init/deinit sysctl stuff.
- Make relevant sysctls also tunables.
- Add different harvesting "styles" to allow for different requirements
  (direct, queue, fast).
- Add harvesting of FFS atime events. This needs to be checked for
  weighing down the FS code.
- Add harvesting of slab allocator events. This needs to be checked for
  weighing down the allocator code.
- Fix the random(9) manpage.
- Loadable modules are not present for now. These will be re-engineered
  when the dust settles.
- Use macros for locks.
- Fix comments.

* src/share/man/...
- Update the man pages.

* src/etc/...
- The startup/shutdown work is done in D2924.

* src/UPDATING
- Add UPDATING announcement.

* src/sys/dev/random/build.sh
- Add copyright.
- Add libz for unit tests.

* src/sys/dev/random/dummy.c
- Remove; no longer needed. Functionality incorporated into randomdev.*.

* live_entropy_sources.c live_entropy_sources.h
- Remove; content moved.
- move content to randomdev.[ch] and optimise.

* src/sys/dev/random/random_adaptors.c src/sys/dev/random/random_adaptors.h
- Remove; plugability is no longer used. Compile-time algorithm
  selection is the way to go.

* src/sys/dev/random/random_harvestq.c src/sys/dev/random/random_harvestq.h
- Add early (re)boot-time randomness caching.

* src/sys/dev/random/randomdev_soft.c src/sys/dev/random/randomdev_soft.h
- Remove; no longer needed.

* src/sys/dev/random/uint128.h
- Provide a fake uint128_t; if a real one ever arrived, we can use
  that instead. All that is needed here is N=0, N++, N==0, and some
  localised trickery is used to manufacture a 128-bit 0ULLL.

* src/sys/dev/random/unit_test.c src/sys/dev/random/unit_test.h
- Improve unit tests; previously the testing human needed clairvoyance;
  now the test will do a basic check of compressibility. Clairvoyant
  talent is still a good idea.
- This is still a long way off a proper unit test.

* src/sys/dev/random/fortuna.c src/sys/dev/random/fortuna.h
- Improve messy union to just uint128_t.
- Remove unneeded 'static struct fortuna_start_cache'.
- Tighten up up arithmetic.
- Provide a method to allow eternal junk to be introduced; harden
  it against blatant by compress/hashing.
- Assert that locks are held correctly.
- Fix the nasty pre- and post-read overloading by providing explictit
  functions to do these tasks.
- Turn into self-sufficient module (no longer requires randomdev_soft.[ch])

* src/sys/dev/random/yarrow.c src/sys/dev/random/yarrow.h
- Improve messy union to just uint128_t.
- Remove unneeded 'staic struct start_cache'.
- Tighten up up arithmetic.
- Provide a method to allow eternal junk to be introduced; harden
  it against blatant by compress/hashing.
- Assert that locks are held correctly.
- Fix the nasty pre- and post-read overloading by providing explictit
  functions to do these tasks.
- Turn into self-sufficient module (no longer requires randomdev_soft.[ch])
- Fix some magic numbers elsewhere used as FAST and SLOW.

Differential Revision: https://reviews.freebsd.org/D2025
Reviewed by: vsevolod,delphij,rwatson,trasz,jmg
Approved by: so (delphij)

2 files changed, 10 insertions, 16 deletions

diff --git a/sys/libkern/arc4random.c b/sys/libkern/arc4random.c
index 62ace2c..9de5a84 100644
--- a/sys/libkern/arc4random.c
+++ b/sys/libkern/arc4random.c
@@ -22,7 +22,7 @@ __FBSDID("$FreeBSD$");
 
 #define	ARC4_RESEED_BYTES 65536
 #define	ARC4_RESEED_SECONDS 300
-#define	ARC4_KEYBYTES (256 / 8)
+#define	ARC4_KEYBYTES 256
 
 int arc4rand_iniseed_state = ARC4_ENTR_NONE;
 
@@ -48,39 +48,33 @@ arc4_swap(u_int8_t *a, u_int8_t *b)
  * Stir our S-box.
  */
 static void
-arc4_randomstir (void)
+arc4_randomstir(void)
 {
-	u_int8_t key[256];
-	int r, n;
+	u_int8_t key[ARC4_KEYBYTES];
+	int n;
 	struct timeval tv_now;
 
 	/*
-	 * XXX read_random() returns unsafe numbers if the entropy
-	 * device is not loaded -- MarkM.
+	 * XXX: FIX!! This isn't brilliant. Need more confidence.
+	 * This returns zero entropy before random(4) is seeded.
 	 */
-	r = read_random(key, ARC4_KEYBYTES);
+	(void)read_random(key, ARC4_KEYBYTES);
 	getmicrouptime(&tv_now);
 	mtx_lock(&arc4_mtx);
-	/* If r == 0 || -1, just use what was on the stack. */
-	if (r > 0) {
-		for (n = r; n < sizeof(key); n++)
-			key[n] = key[n % r];
-	}
-
 	for (n = 0; n < 256; n++) {
 		arc4_j = (arc4_j + arc4_sbox[n] + key[n]) % 256;
 		arc4_swap(&arc4_sbox[n], &arc4_sbox[arc4_j]);
 	}
 	arc4_i = arc4_j = 0;
-
 	/* Reset for next reseed cycle. */
 	arc4_t_reseed = tv_now.tv_sec + ARC4_RESEED_SECONDS;
 	arc4_numruns = 0;
-
 	/*
 	 * Throw away the first N words of output, as suggested in the
 	 * paper "Weaknesses in the Key Scheduling Algorithm of RC4"
 	 * by Fluher, Mantin, and Shamir.  (N = 256 in our case.)
+	 *
+	 * http://dl.acm.org/citation.cfm?id=646557.694759
 	 */
 	for (n = 0; n < 256*4; n++)
 		arc4_randbyte();
diff --git a/sys/libkern/random.c b/sys/libkern/random.c
index 360ff81..3ad75bf 100644
--- a/sys/libkern/random.c
+++ b/sys/libkern/random.c
@@ -50,7 +50,7 @@ srandom(seed)
 }
 
 /*
- * Pseudo-random number generator for randomizing the profiling clock,
+ * Pseudo-random number generator for perturbing the profiling clock,
  * and whatever else we might use it for.  The result is uniform on
  * [0, 2^31 - 1].
  */