summaryrefslogtreecommitdiff
path: root/drivers/char/random.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/char/random.c')
-rw-r--r--drivers/char/random.c244
1 files changed, 136 insertions, 108 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 429b75bb60e8..6b75713d953a 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -295,17 +295,17 @@
* The minimum number of bits of entropy before we wake up a read on
* /dev/random. Should be enough to do a significant reseed.
*/
-static int random_read_wakeup_thresh = 64;
+static int random_read_wakeup_bits = 64;
/*
* If the entropy count falls under this number of bits, then we
* should wake up processes which are selecting or polling on write
* access to /dev/random.
*/
-static int random_write_wakeup_thresh = 28 * OUTPUT_POOL_WORDS;
+static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
/*
- * The minimum number of seconds between urandom pool resending. We
+ * 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.
*/
@@ -322,7 +322,7 @@ static int random_min_urandom_seed = 60;
* Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR
* generators. ACM Transactions on Modeling and Computer Simulation
* 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted
- * GFSR generators II. ACM Transactions on Mdeling and Computer
+ * GFSR generators II. ACM Transactions on Modeling and Computer
* Simulation 4:254-266)
*
* Thanks to Colin Plumb for suggesting this.
@@ -666,10 +666,10 @@ retry:
r->entropy_total, _RET_IP_);
if (r == &input_pool) {
- int entropy_bytes = entropy_count >> ENTROPY_SHIFT;
+ int entropy_bits = entropy_count >> ENTROPY_SHIFT;
/* should we wake readers? */
- if (entropy_bytes >= random_read_wakeup_thresh) {
+ if (entropy_bits >= random_read_wakeup_bits) {
wake_up_interruptible(&random_read_wait);
kill_fasync(&fasync, SIGIO, POLL_IN);
}
@@ -678,9 +678,9 @@ retry:
* forth between them, until the output pools are 75%
* full.
*/
- if (entropy_bytes > random_write_wakeup_thresh &&
+ if (entropy_bits > random_write_wakeup_bits &&
r->initialized &&
- r->entropy_total >= 2*random_read_wakeup_thresh) {
+ r->entropy_total >= 2*random_read_wakeup_bits) {
static struct entropy_store *last = &blocking_pool;
struct entropy_store *other = &blocking_pool;
@@ -844,6 +844,8 @@ void add_interrupt_randomness(int irq, int irq_flags)
cycles_t cycles = random_get_entropy();
__u32 input[4], c_high, j_high;
__u64 ip;
+ unsigned long seed;
+ int credit;
c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
j_high = (sizeof(now) > 4) ? now >> 32 : 0;
@@ -862,20 +864,33 @@ void add_interrupt_randomness(int irq, int irq_flags)
r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
__mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL);
+
/*
* If we don't have a valid cycle counter, and we see
* back-to-back timer interrupts, then skip giving credit for
- * any entropy.
+ * any entropy, otherwise credit 1 bit.
*/
+ credit = 1;
if (cycles == 0) {
if (irq_flags & __IRQF_TIMER) {
if (fast_pool->last_timer_intr)
- return;
+ credit = 0;
fast_pool->last_timer_intr = 1;
} else
fast_pool->last_timer_intr = 0;
}
- credit_entropy_bits(r, 1);
+
+ /*
+ * If we have architectural seed generator, produce a seed and
+ * add it to the pool. For the sake of paranoia count it as
+ * 50% entropic.
+ */
+ if (arch_get_random_seed_long(&seed)) {
+ __mix_pool_bytes(r, &seed, sizeof(seed), NULL);
+ credit += sizeof(seed) * 4;
+ }
+
+ credit_entropy_bits(r, credit);
}
#ifdef CONFIG_BLOCK
@@ -924,19 +939,19 @@ 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 wakeup worth's BITS */
- int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
+ /* 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 many as BYTES as wakeup BITS */
- bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
+ /* pull at least as much as a wakeup */
+ bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
/* but never more than the buffer size */
bytes = min_t(int, bytes, sizeof(tmp));
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_thresh / 8, rsvd);
+ random_read_wakeup_bits / 8, rsvd_bytes);
mix_pool_bytes(r, tmp, bytes, NULL);
credit_entropy_bits(r, bytes*8);
}
@@ -952,35 +967,22 @@ static void push_to_pool(struct work_struct *work)
struct entropy_store *r = container_of(work, struct entropy_store,
push_work);
BUG_ON(!r);
- _xfer_secondary_pool(r, random_read_wakeup_thresh/8);
+ _xfer_secondary_pool(r, random_read_wakeup_bits/8);
trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
r->pull->entropy_count >> ENTROPY_SHIFT);
}
/*
- * These functions extracts randomness from the "entropy pool", and
- * returns it in a buffer.
- *
- * The min parameter specifies the minimum amount we can pull before
- * failing to avoid races that defeat catastrophic reseeding while the
- * reserved parameter indicates how much entropy we must leave in the
- * pool after each pull to avoid starving other readers.
- *
- * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
+ * This function decides how many bytes to actually take from the
+ * given pool, and also debits the entropy count accordingly.
*/
-
static size_t account(struct entropy_store *r, size_t nbytes, int min,
int reserved)
{
- unsigned long flags;
- int wakeup_write = 0;
int have_bytes;
int entropy_count, orig;
size_t ibytes;
- /* Hold lock while accounting */
- spin_lock_irqsave(&r->lock, flags);
-
BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
/* Can we pull enough? */
@@ -988,29 +990,19 @@ retry:
entropy_count = orig = ACCESS_ONCE(r->entropy_count);
have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
ibytes = nbytes;
- if (have_bytes < min + reserved) {
+ /* If limited, never pull more than available */
+ if (r->limit)
+ ibytes = min_t(size_t, ibytes, have_bytes - reserved);
+ if (ibytes < min)
ibytes = 0;
- } else {
- /* If limited, never pull more than available */
- if (r->limit && ibytes + reserved >= have_bytes)
- ibytes = have_bytes - reserved;
-
- if (have_bytes >= ibytes + reserved)
- entropy_count -= ibytes << (ENTROPY_SHIFT + 3);
- else
- entropy_count = reserved << (ENTROPY_SHIFT + 3);
-
- if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
- goto retry;
-
- if ((r->entropy_count >> ENTROPY_SHIFT)
- < random_write_wakeup_thresh)
- wakeup_write = 1;
- }
- spin_unlock_irqrestore(&r->lock, flags);
+ entropy_count = max_t(int, 0,
+ entropy_count - (ibytes << (ENTROPY_SHIFT + 3)));
+ if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
+ goto retry;
trace_debit_entropy(r->name, 8 * ibytes);
- if (wakeup_write) {
+ if (ibytes &&
+ (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
wake_up_interruptible(&random_write_wait);
kill_fasync(&fasync, SIGIO, POLL_OUT);
}
@@ -1018,6 +1010,12 @@ retry:
return ibytes;
}
+/*
+ * This function does the actual extraction for extract_entropy and
+ * extract_entropy_user.
+ *
+ * Note: we assume that .poolwords is a multiple of 16 words.
+ */
static void extract_buf(struct entropy_store *r, __u8 *out)
{
int i;
@@ -1029,23 +1027,23 @@ static void extract_buf(struct entropy_store *r, __u8 *out)
__u8 extract[64];
unsigned long flags;
- /* Generate a hash across the pool, 16 words (512 bits) at a time */
- sha_init(hash.w);
- spin_lock_irqsave(&r->lock, flags);
- for (i = 0; i < r->poolinfo->poolwords; i += 16)
- sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
-
/*
- * If we have a architectural hardware random number
- * generator, mix that in, too.
+ * If we have an architectural hardware random number
+ * generator, use it for SHA's initial vector
*/
+ sha_init(hash.w);
for (i = 0; i < LONGS(20); i++) {
unsigned long v;
if (!arch_get_random_long(&v))
break;
- hash.l[i] ^= v;
+ hash.l[i] = v;
}
+ /* Generate a hash across the pool, 16 words (512 bits) at a time */
+ spin_lock_irqsave(&r->lock, flags);
+ for (i = 0; i < r->poolinfo->poolwords; i += 16)
+ sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
+
/*
* We mix the hash back into the pool to prevent backtracking
* attacks (where the attacker knows the state of the pool
@@ -1079,6 +1077,15 @@ static void extract_buf(struct entropy_store *r, __u8 *out)
memset(&hash, 0, sizeof(hash));
}
+/*
+ * This function extracts randomness from the "entropy pool", and
+ * returns it in a buffer.
+ *
+ * The min parameter specifies the minimum amount we can pull before
+ * failing to avoid races that defeat catastrophic reseeding while the
+ * reserved parameter indicates how much entropy we must leave in the
+ * pool after each pull to avoid starving other readers.
+ */
static ssize_t extract_entropy(struct entropy_store *r, void *buf,
size_t nbytes, int min, int reserved)
{
@@ -1129,6 +1136,10 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf,
return ret;
}
+/*
+ * This function extracts randomness from the "entropy pool", and
+ * returns it in a userspace buffer.
+ */
static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
size_t nbytes)
{
@@ -1170,8 +1181,9 @@ static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
/*
* This function is the exported kernel interface. It returns some
* number of good random numbers, suitable for key generation, seeding
- * TCP sequence numbers, etc. It does not use the hw random number
- * generator, if available; use get_random_bytes_arch() for that.
+ * TCP sequence numbers, etc. It does not rely on the hardware random
+ * number generator. For random bytes direct from the hardware RNG
+ * (when available), use get_random_bytes_arch().
*/
void get_random_bytes(void *buf, int nbytes)
{
@@ -1238,7 +1250,8 @@ static void init_std_data(struct entropy_store *r)
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))
+ if (!arch_get_random_seed_long(&rv) &&
+ !arch_get_random_long(&rv))
rv = random_get_entropy();
mix_pool_bytes(r, &rv, sizeof(rv), NULL);
}
@@ -1281,56 +1294,71 @@ void rand_initialize_disk(struct gendisk *disk)
}
#endif
-static ssize_t
-random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
+/*
+ * Attempt an emergency refill using arch_get_random_seed_long().
+ *
+ * As with add_interrupt_randomness() be paranoid and only
+ * credit the output as 50% entropic.
+ */
+static int arch_random_refill(void)
{
- ssize_t n, retval = 0, count = 0;
+ const unsigned int nlongs = 64; /* Arbitrary number */
+ unsigned int n = 0;
+ unsigned int i;
+ unsigned long buf[nlongs];
- if (nbytes == 0)
+ if (!arch_has_random_seed())
return 0;
- while (nbytes > 0) {
- n = nbytes;
- if (n > SEC_XFER_SIZE)
- n = SEC_XFER_SIZE;
+ for (i = 0; i < nlongs; i++) {
+ if (arch_get_random_seed_long(&buf[n]))
+ n++;
+ }
- n = extract_entropy_user(&blocking_pool, buf, n);
+ if (n) {
+ unsigned int rand_bytes = n * sizeof(unsigned long);
- if (n < 0) {
- retval = n;
- break;
- }
+ mix_pool_bytes(&input_pool, buf, rand_bytes, NULL);
+ credit_entropy_bits(&input_pool, rand_bytes*4);
+ }
+ return n;
+}
+
+static ssize_t
+random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
+{
+ ssize_t n;
+
+ if (nbytes == 0)
+ return 0;
+
+ nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
+ while (1) {
+ n = extract_entropy_user(&blocking_pool, buf, nbytes);
+ if (n < 0)
+ return n;
trace_random_read(n*8, (nbytes-n)*8,
ENTROPY_BITS(&blocking_pool),
ENTROPY_BITS(&input_pool));
+ if (n > 0)
+ return n;
- if (n == 0) {
- if (file->f_flags & O_NONBLOCK) {
- retval = -EAGAIN;
- break;
- }
-
- wait_event_interruptible(random_read_wait,
- ENTROPY_BITS(&input_pool) >=
- random_read_wakeup_thresh);
-
- if (signal_pending(current)) {
- retval = -ERESTARTSYS;
- break;
- }
+ /* Pool is (near) empty. Maybe wait and retry. */
+ /* First try an emergency refill */
+ if (arch_random_refill())
continue;
- }
- count += n;
- buf += n;
- nbytes -= n;
- break; /* This break makes the device work */
- /* like a named pipe */
- }
+ if (file->f_flags & O_NONBLOCK)
+ return -EAGAIN;
- return (count ? count : retval);
+ wait_event_interruptible(random_read_wait,
+ ENTROPY_BITS(&input_pool) >=
+ random_read_wakeup_bits);
+ if (signal_pending(current))
+ return -ERESTARTSYS;
+ }
}
static ssize_t
@@ -1358,9 +1386,9 @@ random_poll(struct file *file, poll_table * wait)
poll_wait(file, &random_read_wait, wait);
poll_wait(file, &random_write_wait, wait);
mask = 0;
- if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_thresh)
+ if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
mask |= POLLIN | POLLRDNORM;
- if (ENTROPY_BITS(&input_pool) < random_write_wakeup_thresh)
+ if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
mask |= POLLOUT | POLLWRNORM;
return mask;
}
@@ -1507,18 +1535,18 @@ EXPORT_SYMBOL(generate_random_uuid);
#include <linux/sysctl.h>
static int min_read_thresh = 8, min_write_thresh;
-static int max_read_thresh = INPUT_POOL_WORDS * 32;
+static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
static int max_write_thresh = INPUT_POOL_WORDS * 32;
static char sysctl_bootid[16];
/*
- * These functions is used to return both the bootid UUID, and random
+ * This function is used to return both the bootid UUID, and random
* UUID. The difference is in whether table->data is NULL; if it is,
* then a new UUID is generated and returned to the user.
*
- * If the user accesses this via the proc interface, it will be returned
- * as an ASCII string in the standard UUID format. If accesses via the
- * sysctl system call, it is returned as 16 bytes of binary data.
+ * If the user accesses this via the proc interface, the UUID will be
+ * returned as an ASCII string in the standard UUID format; if via the
+ * sysctl system call, as 16 bytes of binary data.
*/
static int proc_do_uuid(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
@@ -1583,7 +1611,7 @@ struct ctl_table random_table[] = {
},
{
.procname = "read_wakeup_threshold",
- .data = &random_read_wakeup_thresh,
+ .data = &random_read_wakeup_bits,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
@@ -1592,7 +1620,7 @@ struct ctl_table random_table[] = {
},
{
.procname = "write_wakeup_threshold",
- .data = &random_write_wakeup_thresh,
+ .data = &random_write_wakeup_bits,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
generated by cgit v1.2.3 (git 2.39.0) at 2024-12-23 12:39:24 +0300