Merge branch 'prandom'

prandom fixes/improvements

====================
It would be great if you could still consider this series that fixes and
improves prandom for 3.13. We have sent it to netdev as prandom() originally
came from net/core/utils.c and networking is its main user. For a detailled
description, please see individual patches.

For patch 3 in this series, there will be a minor merge conflict with the
random tree that is for 3.13. See below how to resolve it.

====
Hannes says: on merge with the random tree I would suggest to resolve the
conflict in drivers/char/random.c like this:

if (r->entropy_total > 128) {
	r->initialized = 1;
	r->entropy_total = 0;
	if (r == &nonblocking_pool) {
		prandom_reseed_late();
		pr_notice("random: %s pool is initialized\n",
			  r->name);
	}
}

So it won't generate a warning if DEBUG_RANDOM_BOOT gets activated.
====

Patch 1 should probably also go to -stable.

Set tested on 32 and 64 bit machines.

Thanks a lot!

Ref. original discussion: http://patchwork.ozlabs.org/patch/289951/
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 280 insertions, 34 deletions

diff --git a/lib/Kconfig b/lib/Kconfig
index b3c8be0da17..75485e163ca 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -189,6 +189,13 @@ config AUDIT_GENERIC
 	depends on AUDIT && !AUDIT_ARCH
 	default y
 
+config RANDOM32_SELFTEST
+	bool "PRNG perform self test on init"
+	default n
+	help
+	  This option enables the 32 bit PRNG library functions to perform a
+	  self test on initialization.
+
 #
 # compression support is select'ed if needed
 #
diff --git a/lib/random32.c b/lib/random32.c
index 52280d5526b..82da4f4c348 100644
--- a/lib/random32.c
+++ b/lib/random32.c
@@ -2,19 +2,19 @@
   This is a maximally equidistributed combined Tausworthe generator
   based on code from GNU Scientific Library 1.5 (30 Jun 2004)
 
-   x_n = (s1_n ^ s2_n ^ s3_n)
+  lfsr113 version:
 
-   s1_{n+1} = (((s1_n & 4294967294) <<12) ^ (((s1_n <<13) ^ s1_n) >>19))
-   s2_{n+1} = (((s2_n & 4294967288) << 4) ^ (((s2_n << 2) ^ s2_n) >>25))
-   s3_{n+1} = (((s3_n & 4294967280) <<17) ^ (((s3_n << 3) ^ s3_n) >>11))
+   x_n = (s1_n ^ s2_n ^ s3_n ^ s4_n)
 
-   The period of this generator is about 2^88.
+   s1_{n+1} = (((s1_n & 4294967294) << 18) ^ (((s1_n <<  6) ^ s1_n) >> 13))
+   s2_{n+1} = (((s2_n & 4294967288) <<  2) ^ (((s2_n <<  2) ^ s2_n) >> 27))
+   s3_{n+1} = (((s3_n & 4294967280) <<  7) ^ (((s3_n << 13) ^ s3_n) >> 21))
+   s4_{n+1} = (((s4_n & 4294967168) << 13) ^ (((s4_n <<  3) ^ s4_n) >> 12))
 
-   From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe
-   Generators", Mathematics of Computation, 65, 213 (1996), 203--213.
-
-   This is available on the net from L'Ecuyer's home page,
+   The period of this generator is about 2^113 (see erratum paper).
 
+   From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe
+   Generators", Mathematics of Computation, 65, 213 (1996), 203--213:
    http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps
    ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps
 
@@ -29,7 +29,7 @@
         that paper.)
 
    This affects the seeding procedure by imposing the requirement
-   s1 > 1, s2 > 7, s3 > 15.
+   s1 > 1, s2 > 7, s3 > 15, s4 > 127.
 
 */
 
@@ -38,6 +38,11 @@
 #include <linux/export.h>
 #include <linux/jiffies.h>
 #include <linux/random.h>
+#include <linux/sched.h>
+
+#ifdef CONFIG_RANDOM32_SELFTEST
+static void __init prandom_state_selftest(void);
+#endif
 
 static DEFINE_PER_CPU(struct rnd_state, net_rand_state);
 
@@ -52,11 +57,12 @@ u32 prandom_u32_state(struct rnd_state *state)
 {
 #define TAUSWORTHE(s,a,b,c,d) ((s&c)<<d) ^ (((s <<a) ^ s)>>b)
 
-	state->s1 = TAUSWORTHE(state->s1, 13, 19, 4294967294UL, 12);
-	state->s2 = TAUSWORTHE(state->s2, 2, 25, 4294967288UL, 4);
-	state->s3 = TAUSWORTHE(state->s3, 3, 11, 4294967280UL, 17);
+	state->s1 = TAUSWORTHE(state->s1,  6U, 13U, 4294967294U, 18U);
+	state->s2 = TAUSWORTHE(state->s2,  2U, 27U, 4294967288U,  2U);
+	state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U,  7U);
+	state->s4 = TAUSWORTHE(state->s4,  3U, 12U, 4294967168U, 13U);
 
-	return (state->s1 ^ state->s2 ^ state->s3);
+	return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4);
 }
 EXPORT_SYMBOL(prandom_u32_state);
 
@@ -126,6 +132,38 @@ void prandom_bytes(void *buf, int bytes)
 }
 EXPORT_SYMBOL(prandom_bytes);
 
+static void prandom_warmup(struct rnd_state *state)
+{
+	/* Calling RNG ten times to satify recurrence condition */
+	prandom_u32_state(state);
+	prandom_u32_state(state);
+	prandom_u32_state(state);
+	prandom_u32_state(state);
+	prandom_u32_state(state);
+	prandom_u32_state(state);
+	prandom_u32_state(state);
+	prandom_u32_state(state);
+	prandom_u32_state(state);
+	prandom_u32_state(state);
+}
+
+static void prandom_seed_very_weak(struct rnd_state *state, u32 seed)
+{
+	/* Note: This sort of seeding is ONLY used in test cases and
+	 * during boot at the time from core_initcall until late_initcall
+	 * as we don't have a stronger entropy source available yet.
+	 * After late_initcall, we reseed entire state, we have to (!),
+	 * otherwise an attacker just needs to search 32 bit space to
+	 * probe for our internal 128 bit state if he knows a couple
+	 * of prandom32 outputs!
+	 */
+#define LCG(x)	((x) * 69069U)	/* super-duper LCG */
+	state->s1 = __seed(LCG(seed),        2U);
+	state->s2 = __seed(LCG(state->s1),   8U);
+	state->s3 = __seed(LCG(state->s2),  16U);
+	state->s4 = __seed(LCG(state->s3), 128U);
+}
+
 /**
  *	prandom_seed - add entropy to pseudo random number generator
  *	@seed: seed value
@@ -141,7 +179,9 @@ void prandom_seed(u32 entropy)
 	 */
 	for_each_possible_cpu (i) {
 		struct rnd_state *state = &per_cpu(net_rand_state, i);
-		state->s1 = __seed(state->s1 ^ entropy, 1);
+
+		state->s1 = __seed(state->s1 ^ entropy, 2U);
+		prandom_warmup(state);
 	}
 }
 EXPORT_SYMBOL(prandom_seed);
@@ -154,46 +194,245 @@ static int __init prandom_init(void)
 {
 	int i;
 
+#ifdef CONFIG_RANDOM32_SELFTEST
+	prandom_state_selftest();
+#endif
+
 	for_each_possible_cpu(i) {
 		struct rnd_state *state = &per_cpu(net_rand_state,i);
 
-#define LCG(x)	((x) * 69069)	/* super-duper LCG */
-		state->s1 = __seed(LCG(i + jiffies), 1);
-		state->s2 = __seed(LCG(state->s1), 7);
-		state->s3 = __seed(LCG(state->s2), 15);
-
-		/* "warm it up" */
-		prandom_u32_state(state);
-		prandom_u32_state(state);
-		prandom_u32_state(state);
-		prandom_u32_state(state);
-		prandom_u32_state(state);
-		prandom_u32_state(state);
+		prandom_seed_very_weak(state, (i + jiffies) ^ random_get_entropy());
+		prandom_warmup(state);
 	}
 	return 0;
 }
 core_initcall(prandom_init);
 
+static void __prandom_timer(unsigned long dontcare);
+static DEFINE_TIMER(seed_timer, __prandom_timer, 0, 0);
+
+static void __prandom_timer(unsigned long dontcare)
+{
+	u32 entropy;
+
+	get_random_bytes(&entropy, sizeof(entropy));
+	prandom_seed(entropy);
+	/* reseed every ~60 seconds, in [40 .. 80) interval with slack */
+	seed_timer.expires = jiffies + (40 * HZ + (prandom_u32() % (40 * HZ)));
+	add_timer(&seed_timer);
+}
+
+static void prandom_start_seed_timer(void)
+{
+	set_timer_slack(&seed_timer, HZ);
+	seed_timer.expires = jiffies + 40 * HZ;
+	add_timer(&seed_timer);
+}
+
 /*
  *	Generate better values after random number generator
  *	is fully initialized.
  */
-static int __init prandom_reseed(void)
+static void __prandom_reseed(bool late)
 {
 	int i;
+	unsigned long flags;
+	static bool latch = false;
+	static DEFINE_SPINLOCK(lock);
+
+	/* only allow initial seeding (late == false) once */
+	spin_lock_irqsave(&lock, flags);
+	if (latch && !late)
+		goto out;
+	latch = true;
 
 	for_each_possible_cpu(i) {
 		struct rnd_state *state = &per_cpu(net_rand_state,i);
-		u32 seeds[3];
+		u32 seeds[4];
 
 		get_random_bytes(&seeds, sizeof(seeds));
-		state->s1 = __seed(seeds[0], 1);
-		state->s2 = __seed(seeds[1], 7);
-		state->s3 = __seed(seeds[2], 15);
+		state->s1 = __seed(seeds[0],   2U);
+		state->s2 = __seed(seeds[1],   8U);
+		state->s3 = __seed(seeds[2],  16U);
+		state->s4 = __seed(seeds[3], 128U);
 
-		/* mix it in */
-		prandom_u32_state(state);
+		prandom_warmup(state);
 	}
+out:
+	spin_unlock_irqrestore(&lock, flags);
+}
+
+void prandom_reseed_late(void)
+{
+	__prandom_reseed(true);
+}
+
+static int __init prandom_reseed(void)
+{
+	__prandom_reseed(false);
+	prandom_start_seed_timer();
 	return 0;
 }
 late_initcall(prandom_reseed);
+
+#ifdef CONFIG_RANDOM32_SELFTEST
+static struct prandom_test1 {
+	u32 seed;
+	u32 result;
+} test1[] = {
+	{ 1U, 3484351685U },
+	{ 2U, 2623130059U },
+	{ 3U, 3125133893U },
+	{ 4U,  984847254U },
+};
+
+static struct prandom_test2 {
+	u32 seed;
+	u32 iteration;
+	u32 result;
+} test2[] = {
+	/* Test cases against taus113 from GSL library. */
+	{  931557656U, 959U, 2975593782U },
+	{ 1339693295U, 876U, 3887776532U },
+	{ 1545556285U, 961U, 1615538833U },
+	{  601730776U, 723U, 1776162651U },
+	{ 1027516047U, 687U,  511983079U },
+	{  416526298U, 700U,  916156552U },
+	{ 1395522032U, 652U, 2222063676U },
+	{  366221443U, 617U, 2992857763U },
+	{ 1539836965U, 714U, 3783265725U },
+	{  556206671U, 994U,  799626459U },
+	{  684907218U, 799U,  367789491U },
+	{ 2121230701U, 931U, 2115467001U },
+	{ 1668516451U, 644U, 3620590685U },
+	{  768046066U, 883U, 2034077390U },
+	{ 1989159136U, 833U, 1195767305U },
+	{  536585145U, 996U, 3577259204U },
+	{ 1008129373U, 642U, 1478080776U },
+	{ 1740775604U, 939U, 1264980372U },
+	{ 1967883163U, 508U,   10734624U },
+	{ 1923019697U, 730U, 3821419629U },
+	{  442079932U, 560U, 3440032343U },
+	{ 1961302714U, 845U,  841962572U },
+	{ 2030205964U, 962U, 1325144227U },
+	{ 1160407529U, 507U,  240940858U },
+	{  635482502U, 779U, 4200489746U },
+	{ 1252788931U, 699U,  867195434U },
+	{ 1961817131U, 719U,  668237657U },
+	{ 1071468216U, 983U,  917876630U },
+	{ 1281848367U, 932U, 1003100039U },
+	{  582537119U, 780U, 1127273778U },
+	{ 1973672777U, 853U, 1071368872U },
+	{ 1896756996U, 762U, 1127851055U },
+	{  847917054U, 500U, 1717499075U },
+	{ 1240520510U, 951U, 2849576657U },
+	{ 1685071682U, 567U, 1961810396U },
+	{ 1516232129U, 557U,    3173877U },
+	{ 1208118903U, 612U, 1613145022U },
+	{ 1817269927U, 693U, 4279122573U },
+	{ 1510091701U, 717U,  638191229U },
+	{  365916850U, 807U,  600424314U },
+	{  399324359U, 702U, 1803598116U },
+	{ 1318480274U, 779U, 2074237022U },
+	{  697758115U, 840U, 1483639402U },
+	{ 1696507773U, 840U,  577415447U },
+	{ 2081979121U, 981U, 3041486449U },
+	{  955646687U, 742U, 3846494357U },
+	{ 1250683506U, 749U,  836419859U },
+	{  595003102U, 534U,  366794109U },
+	{   47485338U, 558U, 3521120834U },
+	{  619433479U, 610U, 3991783875U },
+	{  704096520U, 518U, 4139493852U },
+	{ 1712224984U, 606U, 2393312003U },
+	{ 1318233152U, 922U, 3880361134U },
+	{  855572992U, 761U, 1472974787U },
+	{   64721421U, 703U,  683860550U },
+	{  678931758U, 840U,  380616043U },
+	{  692711973U, 778U, 1382361947U },
+	{  677703619U, 530U, 2826914161U },
+	{   92393223U, 586U, 1522128471U },
+	{ 1222592920U, 743U, 3466726667U },
+	{  358288986U, 695U, 1091956998U },
+	{ 1935056945U, 958U,  514864477U },
+	{  735675993U, 990U, 1294239989U },
+	{ 1560089402U, 897U, 2238551287U },
+	{   70616361U, 829U,   22483098U },
+	{  368234700U, 731U, 2913875084U },
+	{   20221190U, 879U, 1564152970U },
+	{  539444654U, 682U, 1835141259U },
+	{ 1314987297U, 840U, 1801114136U },
+	{ 2019295544U, 645U, 3286438930U },
+	{  469023838U, 716U, 1637918202U },
+	{ 1843754496U, 653U, 2562092152U },
+	{  400672036U, 809U, 4264212785U },
+	{  404722249U, 965U, 2704116999U },
+	{  600702209U, 758U,  584979986U },
+	{  519953954U, 667U, 2574436237U },
+	{ 1658071126U, 694U, 2214569490U },
+	{  420480037U, 749U, 3430010866U },
+	{  690103647U, 969U, 3700758083U },
+	{ 1029424799U, 937U, 3787746841U },
+	{ 2012608669U, 506U, 3362628973U },
+	{ 1535432887U, 998U,   42610943U },
+	{ 1330635533U, 857U, 3040806504U },
+	{ 1223800550U, 539U, 3954229517U },
+	{ 1322411537U, 680U, 3223250324U },
+	{ 1877847898U, 945U, 2915147143U },
+	{ 1646356099U, 874U,  965988280U },
+	{  805687536U, 744U, 4032277920U },
+	{ 1948093210U, 633U, 1346597684U },
+	{  392609744U, 783U, 1636083295U },
+	{  690241304U, 770U, 1201031298U },
+	{ 1360302965U, 696U, 1665394461U },
+	{ 1220090946U, 780U, 1316922812U },
+	{  447092251U, 500U, 3438743375U },
+	{ 1613868791U, 592U,  828546883U },
+	{  523430951U, 548U, 2552392304U },
+	{  726692899U, 810U, 1656872867U },
+	{ 1364340021U, 836U, 3710513486U },
+	{ 1986257729U, 931U,  935013962U },
+	{  407983964U, 921U,  728767059U },
+};
+
+static void __init prandom_state_selftest(void)
+{
+	int i, j, errors = 0, runs = 0;
+	bool error = false;
+
+	for (i = 0; i < ARRAY_SIZE(test1); i++) {
+		struct rnd_state state;
+
+		prandom_seed_very_weak(&state, test1[i].seed);
+		prandom_warmup(&state);
+
+		if (test1[i].result != prandom_u32_state(&state))
+			error = true;
+	}
+
+	if (error)
+		pr_warn("prandom: seed boundary self test failed\n");
+	else
+		pr_info("prandom: seed boundary self test passed\n");
+
+	for (i = 0; i < ARRAY_SIZE(test2); i++) {
+		struct rnd_state state;
+
+		prandom_seed_very_weak(&state, test2[i].seed);
+		prandom_warmup(&state);
+
+		for (j = 0; j < test2[i].iteration - 1; j++)
+			prandom_u32_state(&state);
+
+		if (test2[i].result != prandom_u32_state(&state))
+			errors++;
+
+		runs++;
+		cond_resched();
+	}
+
+	if (errors)
+		pr_warn("prandom: %d/%d self tests failed\n", errors, runs);
+	else
+		pr_info("prandom: %d self tests passed\n", runs);
+}
+#endif