From: "Theodore Ts'o" <tytso@mit.edu>
To: Linux Kernel Developers List <linux-kernel@vger.kernel.org>
Cc: hpa@zytor.com, joern@logfs.org, macro@linux-mips.org,
ralf@linux-mips.org, dave.taht@gmail.com, blogic@openwrt.org,
andrewmcgr@gmail.com, smueller@chronox.de, geert@linux-m68k.org,
tg@mirbsd.de, "Theodore Ts'o" <tytso@mit.edu>
Subject: [PATCH, RFC 10/12] random: cap the rate which the /dev/urandom pool gets reseeded
Date: Sun, 22 Sep 2013 16:38:56 -0400 [thread overview]
Message-ID: <1379882338-7209-11-git-send-email-tytso@mit.edu> (raw)
In-Reply-To: <1379882338-7209-1-git-send-email-tytso@mit.edu>
In order to avoid draining the input pool of its entropy at too high
of a rate, enforce a minimum time interval between reseedings of the
urandom pool. This is set to 60 seconds by default.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
drivers/char/random.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 292e717..3439b1c 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -306,6 +306,13 @@ static int random_read_wakeup_thresh = 64;
static int random_write_wakeup_thresh = 128;
/*
+ * The minimum number of seconds between urandom pool resending. We
+ * do this to limit the amount of entropy that can be drained from the
+ * input pool even if there are heavy demands on /dev/urandom.
+ */
+static int random_min_urandom_seed = 60;
+
+/*
* When the input pool goes over trickle_thresh, start dropping most
* samples to avoid wasting CPU time and reduce lock contention.
*/
@@ -437,6 +444,7 @@ struct entropy_store {
struct entropy_store *pull;
/* read-write data: */
+ unsigned long last_pulled;
spinlock_t lock;
unsigned short add_ptr;
unsigned short input_rotate;
@@ -885,6 +893,15 @@ static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
{
__u32 tmp[OUTPUT_POOL_WORDS];
+ if (r->limit == 0 && random_min_urandom_seed) {
+ unsigned long now = jiffies;
+
+ if (time_before(now,
+ r->last_pulled + random_min_urandom_seed * HZ)) {
+ return;
+ }
+ r->last_pulled = now;
+ }
if (r->pull &&
r->entropy_count < (nbytes << (ENTROPY_SHIFT + 3)) &&
r->entropy_count < r->poolinfo->poolfracbits) {
@@ -1188,6 +1205,7 @@ static void init_std_data(struct entropy_store *r)
r->entropy_count = 0;
r->entropy_total = 0;
r->last_data_init = 0;
+ r->last_pulled = jiffies;
mix_pool_bytes(r, &now, sizeof(now), NULL);
for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
if (!arch_get_random_long(&rv))
@@ -1539,6 +1557,13 @@ struct ctl_table random_table[] = {
.extra2 = &max_write_thresh,
},
{
+ .procname = "urandom_min_reseed_secs",
+ .data = &random_min_urandom_seed,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ },
+ {
.procname = "boot_id",
.data = &sysctl_bootid,
.maxlen = 16,
--
1.7.12.rc0.22.gcdd159b
next prev parent reply other threads:[~2013-09-22 20:40 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-22 20:38 [PATCH, RFC 00/12] random driver changes Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 01/12] random: run random_int_secret_init() run after all late_initcalls Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 02/12] random: Statically compute poolbitshift, poolbytes, poolbits Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 03/12] random: Allow fractional bits to be tracked Theodore Ts'o
2013-09-23 4:01 ` Theodore Ts'o
2013-09-23 4:03 ` H. Peter Anvin
2013-09-22 20:38 ` [PATCH, RFC 04/12] random: Account for entropy loss due to overwrites Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 05/12] random: fix the tracepoint for get_random_bytes(_arch) Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 06/12] random: optimize spinlock use in add_device_randomness() Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 07/12] random: allow architectures to optionally define random_get_entropy() Theodore Ts'o
2013-09-23 10:38 ` Stephan Mueller
2013-09-23 11:05 ` Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 08/12] random: mix in architectural randomness earlier in extract_buf() Theodore Ts'o
2013-09-23 4:11 ` H. Peter Anvin
2013-09-23 4:33 ` Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 09/12] random: optimize the entropy_store structure Theodore Ts'o
2013-09-22 20:38 ` Theodore Ts'o [this message]
2013-09-22 21:21 ` [PATCH, RFC 10/12] random: cap the rate which the /dev/urandom pool gets reseeded H. Peter Anvin
2013-09-22 21:40 ` Theodore Ts'o
2013-09-22 22:45 ` H. Peter Anvin
2013-09-22 23:23 ` Theodore Ts'o
2013-09-23 0:26 ` H. Peter Anvin
2013-09-22 20:38 ` [PATCH, RFC 11/12] random: speed up the fast_mix function by a factor of four Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 12/12] random: adjust the generator polynomials in the mixing function slightly Theodore Ts'o
2013-09-25 10:51 ` Jörg-Volker Peetz
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