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Change get_random_{int,log} to use the CRNG used by /dev/urandom and

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getrandom(2).  It's faster and arguably more secure than cut-down MD5
 that we had been using.
 
 Also do some code cleanup.
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Merge tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random

Pull random updates from Ted Ts'o:
 "Change get_random_{int,log} to use the CRNG used by /dev/urandom and
  getrandom(2). It's faster and arguably more secure than cut-down MD5
  that we had been using.

  Also do some code cleanup"

* tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  random: move random_min_urandom_seed into CONFIG_SYSCTL ifdef block
  random: convert get_random_int/long into get_random_u32/u64
  random: use chacha20 for get_random_int/long
  random: fix comment for unused random_min_urandom_seed
  random: remove variable limit
  random: remove stale urandom_init_wait
  random: remove stale maybe_reseed_primary_crng
This commit is contained in:
Linus Torvalds 2017-03-11 09:08:47 -08:00
commit 84c37c168c
3 changed files with 71 additions and 89 deletions
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141
drivers/char/random.c
View File

@ -312,13 +312,6 @@ static int random_read_wakeup_bits = 64;
*/
static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
/*
* The minimum number of seconds between urandom pool reseeding. 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;
/*
* Originally, we used a primitive polynomial of degree .poolwords
* over GF(2). The taps for various sizes are defined below. They
@ -409,7 +402,6 @@ static struct poolinfo {
*/
static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
static DECLARE_WAIT_QUEUE_HEAD(urandom_init_wait);
static struct fasync_struct *fasync;
static DEFINE_SPINLOCK(random_ready_list_lock);
@ -467,7 +459,6 @@ struct entropy_store {
int entropy_count;
int entropy_total;
unsigned int initialized:1;
unsigned int limit:1;
unsigned int last_data_init:1;
__u8 last_data[EXTRACT_SIZE];
};
@ -485,7 +476,6 @@ static __u32 blocking_pool_data[OUTPUT_POOL_WORDS] __latent_entropy;
static struct entropy_store input_pool = {
.poolinfo = &poolinfo_table[0],
.name = "input",
.limit = 1,
.lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
.pool = input_pool_data
};
@ -493,7 +483,6 @@ static struct entropy_store input_pool = {
static struct entropy_store blocking_pool = {
.poolinfo = &poolinfo_table[1],
.name = "blocking",
.limit = 1,
.pull = &input_pool,
.lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
.pool = blocking_pool_data,
@ -855,13 +844,6 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
spin_unlock_irqrestore(&primary_crng.lock, flags);
}
static inline void maybe_reseed_primary_crng(void)
{
if (crng_init > 2 &&
time_after(jiffies, primary_crng.init_time + CRNG_RESEED_INTERVAL))
crng_reseed(&primary_crng, &input_pool);
}
static inline void crng_wait_ready(void)
{
wait_event_interruptible(crng_init_wait, crng_ready());
@ -1220,15 +1202,6 @@ static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
r->entropy_count > r->poolinfo->poolfracbits)
return;
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;
}
_xfer_secondary_pool(r, nbytes);
}
@ -1236,8 +1209,6 @@ static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
{
__u32 tmp[OUTPUT_POOL_WORDS];
/* For /dev/random's pool, always leave two wakeups' worth */
int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4;
int bytes = nbytes;
/* pull at least as much as a wakeup */
@ -1248,7 +1219,7 @@ static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
bytes = extract_entropy(r->pull, tmp, bytes,
random_read_wakeup_bits / 8, rsvd_bytes);
random_read_wakeup_bits / 8, 0);
mix_pool_bytes(r, tmp, bytes);
credit_entropy_bits(r, bytes*8);
}
@ -1276,7 +1247,7 @@ static void push_to_pool(struct work_struct *work)
static size_t account(struct entropy_store *r, size_t nbytes, int min,
int reserved)
{
int entropy_count, orig;
int entropy_count, orig, have_bytes;
size_t ibytes, nfrac;
BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
@ -1285,14 +1256,12 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
retry:
entropy_count = orig = ACCESS_ONCE(r->entropy_count);
ibytes = nbytes;
/* If limited, never pull more than available */
if (r->limit) {
int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
/* never pull more than available */
have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
if ((have_bytes -= reserved) < 0)
have_bytes = 0;
ibytes = min_t(size_t, ibytes, have_bytes);
}
if ((have_bytes -= reserved) < 0)
have_bytes = 0;
ibytes = min_t(size_t, ibytes, have_bytes);
if (ibytes < min)
ibytes = 0;
@ -1912,6 +1881,7 @@ SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
static int min_read_thresh = 8, min_write_thresh;
static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
static int max_write_thresh = INPUT_POOL_WORDS * 32;
static int random_min_urandom_seed = 60;
static char sysctl_bootid[16];
/*
@ -2042,63 +2012,64 @@ struct ctl_table random_table[] = {
};
#endif /* CONFIG_SYSCTL */
static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
int random_int_secret_init(void)
{
get_random_bytes(random_int_secret, sizeof(random_int_secret));
return 0;
}
static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash)
__aligned(sizeof(unsigned long));
struct batched_entropy {
union {
u64 entropy_u64[CHACHA20_BLOCK_SIZE / sizeof(u64)];
u32 entropy_u32[CHACHA20_BLOCK_SIZE / sizeof(u32)];
};
unsigned int position;
};
/*
* Get a random word for internal kernel use only. Similar to urandom but
* with the goal of minimal entropy pool depletion. As a result, the random
* value is not cryptographically secure but for several uses the cost of
* depleting entropy is too high
* Get a random word for internal kernel use only. The quality of the random
* number is either as good as RDRAND or as good as /dev/urandom, with the
* goal of being quite fast and not depleting entropy.
*/
unsigned int get_random_int(void)
static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64);
u64 get_random_u64(void)
{
__u32 *hash;
unsigned int ret;
u64 ret;
struct batched_entropy *batch;
#if BITS_PER_LONG == 64
if (arch_get_random_long((unsigned long *)&ret))
return ret;
#else
if (arch_get_random_long((unsigned long *)&ret) &&
arch_get_random_long((unsigned long *)&ret + 1))
return ret;
#endif
batch = &get_cpu_var(batched_entropy_u64);
if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
extract_crng((u8 *)batch->entropy_u64);
batch->position = 0;
}
ret = batch->entropy_u64[batch->position++];
put_cpu_var(batched_entropy_u64);
return ret;
}
EXPORT_SYMBOL(get_random_u64);
static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32);
u32 get_random_u32(void)
{
u32 ret;
struct batched_entropy *batch;
if (arch_get_random_int(&ret))
return ret;
hash = get_cpu_var(get_random_int_hash);
hash[0] += current->pid + jiffies + random_get_entropy();
md5_transform(hash, random_int_secret);
ret = hash[0];
put_cpu_var(get_random_int_hash);
batch = &get_cpu_var(batched_entropy_u32);
if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {
extract_crng((u8 *)batch->entropy_u32);
batch->position = 0;
}
ret = batch->entropy_u32[batch->position++];
put_cpu_var(batched_entropy_u32);
return ret;
}
EXPORT_SYMBOL(get_random_int);
/*
* Same as get_random_int(), but returns unsigned long.
*/
unsigned long get_random_long(void)
{
__u32 *hash;
unsigned long ret;
if (arch_get_random_long(&ret))
return ret;
hash = get_cpu_var(get_random_int_hash);
hash[0] += current->pid + jiffies + random_get_entropy();
md5_transform(hash, random_int_secret);
ret = *(unsigned long *)hash;
put_cpu_var(get_random_int_hash);
return ret;
}
EXPORT_SYMBOL(get_random_long);
EXPORT_SYMBOL(get_random_u32);
/**
* randomize_page - Generate a random, page aligned address

18
include/linux/random.h
View File

@ -37,14 +37,26 @@ extern void get_random_bytes(void *buf, int nbytes);
extern int add_random_ready_callback(struct random_ready_callback *rdy);
extern void del_random_ready_callback(struct random_ready_callback *rdy);
extern void get_random_bytes_arch(void *buf, int nbytes);
extern int random_int_secret_init(void);
#ifndef MODULE
extern const struct file_operations random_fops, urandom_fops;
#endif
unsigned int get_random_int(void);
unsigned long get_random_long(void);
u32 get_random_u32(void);
u64 get_random_u64(void);
static inline unsigned int get_random_int(void)
{
return get_random_u32();
}
static inline unsigned long get_random_long(void)
{
#if BITS_PER_LONG == 64
return get_random_u64();
#else
return get_random_u32();
#endif
}
unsigned long randomize_page(unsigned long start, unsigned long range);
u32 prandom_u32(void);

1
init/main.c
View File

@ -882,7 +882,6 @@ static void __init do_basic_setup(void)
do_ctors();
usermodehelper_enable();
do_initcalls();
random_int_secret_init();
}
static void __init do_pre_smp_initcalls(void)