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gnu: linux-libre: Try to aggressively gather entropy during boot.

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Fixes <https://bugs.gnu.org/37501>.

* gnu/packages/patches/linux-libre-active-entropy.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/linux.scm (linux-libre-5.2-source): Use it.
This commit is contained in:
Marius Bakke 2019-10-03 22:22:08 +02:00
parent 5157edd885
commit dd69897113
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GPG key ID: A2A06DF2A33A54FA
3 changed files with 89 additions and 1 deletions
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1
gnu/local.mk
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@ -1078,6 +1078,7 @@ dist_patch_DATA = \
%D%/packages/patches/lierolibre-remove-arch-warning.patch \
%D%/packages/patches/lierolibre-try-building-other-arch.patch \
%D%/packages/patches/linkchecker-tests-require-network.patch \
%D%/packages/patches/linux-libre-active-entropy.patch \
%D%/packages/patches/linux-pam-no-setfsuid.patch \
%D%/packages/patches/lirc-localstatedir.patch \
%D%/packages/patches/lirc-reproducible-build.patch \

3
gnu/packages/linux.scm
View file

@ -420,7 +420,8 @@ (define (source-with-patches source patches)
(define-public linux-libre-5.2-source
(source-with-patches linux-libre-5.2-pristine-source
(list %boot-logo-patch
(list (search-patch "linux-libre-active-entropy.patch")
%boot-logo-patch
%linux-libre-arm-export-__sync_icache_dcache-patch)))
(define-public linux-libre-4.19-source

86
gnu/packages/patches/linux-libre-active-entropy.patch Normal file
View file

@ -0,0 +1,86 @@
Try to actively add entropy instead of waiting forever.
Fixes <https://bugs.gnu.org/37501>.
Taken from upstream:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/patch/?id=50ee7529ec4500c88f8664560770a7a1b65db72b
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 5d5ea4ce1442..2fda6166c1dd 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1731,6 +1731,56 @@ void get_random_bytes(void *buf, int nbytes)
}
EXPORT_SYMBOL(get_random_bytes);
+
+/*
+ * Each time the timer fires, we expect that we got an unpredictable
+ * jump in the cycle counter. Even if the timer is running on another
+ * CPU, the timer activity will be touching the stack of the CPU that is
+ * generating entropy..
+ *
+ * Note that we don't re-arm the timer in the timer itself - we are
+ * happy to be scheduled away, since that just makes the load more
+ * complex, but we do not want the timer to keep ticking unless the
+ * entropy loop is running.
+ *
+ * So the re-arming always happens in the entropy loop itself.
+ */
+static void entropy_timer(struct timer_list *t)
+{
+ credit_entropy_bits(&input_pool, 1);
+}
+
+/*
+ * If we have an actual cycle counter, see if we can
+ * generate enough entropy with timing noise
+ */
+static void try_to_generate_entropy(void)
+{
+ struct {
+ unsigned long now;
+ struct timer_list timer;
+ } stack;
+
+ stack.now = random_get_entropy();
+
+ /* Slow counter - or none. Don't even bother */
+ if (stack.now == random_get_entropy())
+ return;
+
+ timer_setup_on_stack(&stack.timer, entropy_timer, 0);
+ while (!crng_ready()) {
+ if (!timer_pending(&stack.timer))
+ mod_timer(&stack.timer, jiffies+1);
+ mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now));
+ schedule();
+ stack.now = random_get_entropy();
+ }
+
+ del_timer_sync(&stack.timer);
+ destroy_timer_on_stack(&stack.timer);
+ mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now));
+}
+
/*
* Wait for the urandom pool to be seeded and thus guaranteed to supply
* cryptographically secure random numbers. This applies to: the /dev/urandom
@@ -1745,7 +1795,17 @@ int wait_for_random_bytes(void)
{
if (likely(crng_ready()))
return 0;
- return wait_event_interruptible(crng_init_wait, crng_ready());
+
+ do {
+ int ret;
+ ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
+ if (ret)
+ return ret > 0 ? 0 : ret;
+
+ try_to_generate_entropy();
+ } while (!crng_ready());
+
+ return 0;
}
EXPORT_SYMBOL(wait_for_random_bytes);