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https://git.yoctoproject.org/meta-ti
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Koen Kooi
df420fe6fd
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net> Signed-off-by: Denys Dmytriyenko <denys@ti.com> Signed-off-by: Denys Dmytriyenko <denis@denix.org>
96 lines
3.3 KiB
Diff
96 lines
3.3 KiB
Diff
From 6ce374197d352474ff8514805efb43436c9cf87b Mon Sep 17 00:00:00 2001
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From: Theodore Ts'o <tytso@mit.edu>
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Date: Thu, 5 Jul 2012 10:35:23 -0400
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Subject: [PATCH 20/70] random: add new get_random_bytes_arch() function
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commit c2557a303ab6712bb6e09447df828c557c710ac9 upstream.
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Create a new function, get_random_bytes_arch() which will use the
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architecture-specific hardware random number generator if it is
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present. Change get_random_bytes() to not use the HW RNG, even if it
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is avaiable.
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The reason for this is that the hw random number generator is fast (if
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it is present), but it requires that we trust the hardware
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manufacturer to have not put in a back door. (For example, an
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increasing counter encrypted by an AES key known to the NSA.)
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It's unlikely that Intel (for example) was paid off by the US
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Government to do this, but it's impossible for them to prove otherwise
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---
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drivers/char/random.c | 29 ++++++++++++++++++++++++-----
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include/linux/random.h | 1 +
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2 files changed, 25 insertions(+), 5 deletions(-)
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diff --git a/drivers/char/random.c b/drivers/char/random.c
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index 4a83220..f3200bf 100644
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--- a/drivers/char/random.c
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+++ b/drivers/char/random.c
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@@ -1038,17 +1038,34 @@ static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
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/*
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* This function is the exported kernel interface. It returns some
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- * number of good random numbers, suitable for seeding TCP sequence
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- * numbers, etc.
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+ * number of good random numbers, suitable for key generation, seeding
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+ * TCP sequence numbers, etc. It does not use the hw random number
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+ * generator, if available; use get_random_bytes_arch() for that.
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*/
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void get_random_bytes(void *buf, int nbytes)
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{
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+ extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
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+}
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+EXPORT_SYMBOL(get_random_bytes);
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+
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+/*
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+ * This function will use the architecture-specific hardware random
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+ * number generator if it is available. The arch-specific hw RNG will
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+ * almost certainly be faster than what we can do in software, but it
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+ * is impossible to verify that it is implemented securely (as
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+ * opposed, to, say, the AES encryption of a sequence number using a
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+ * key known by the NSA). So it's useful if we need the speed, but
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+ * only if we're willing to trust the hardware manufacturer not to
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+ * have put in a back door.
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+ */
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+void get_random_bytes_arch(void *buf, int nbytes)
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+{
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char *p = buf;
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while (nbytes) {
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unsigned long v;
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int chunk = min(nbytes, (int)sizeof(unsigned long));
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-
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+
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if (!arch_get_random_long(&v))
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break;
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@@ -1057,9 +1074,11 @@ void get_random_bytes(void *buf, int nbytes)
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nbytes -= chunk;
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}
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- extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
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+ if (nbytes)
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+ extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
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}
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-EXPORT_SYMBOL(get_random_bytes);
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+EXPORT_SYMBOL(get_random_bytes_arch);
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+
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/*
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* init_std_data - initialize pool with system data
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diff --git a/include/linux/random.h b/include/linux/random.h
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index e14b438..29e217a 100644
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--- a/include/linux/random.h
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+++ b/include/linux/random.h
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@@ -56,6 +56,7 @@ extern void add_input_randomness(unsigned int type, unsigned int code,
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extern void add_interrupt_randomness(int irq, int irq_flags);
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extern void get_random_bytes(void *buf, int nbytes);
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+extern void get_random_bytes_arch(void *buf, int nbytes);
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void generate_random_uuid(unsigned char uuid_out[16]);
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#ifndef MODULE
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--
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1.7.7.6
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