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-rw-r--r--drivers/char/random.c352
1 files changed, 228 insertions, 124 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 4ec04a7..d98b2a6 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -125,21 +125,26 @@
* The current exported interfaces for gathering environmental noise
* from the devices are:
*
+ * void add_device_randomness(const void *buf, unsigned int size);
* void add_input_randomness(unsigned int type, unsigned int code,
* unsigned int value);
- * void add_interrupt_randomness(int irq);
+ * void add_interrupt_randomness(int irq, int irq_flags);
* void add_disk_randomness(struct gendisk *disk);
*
+ * add_device_randomness() is for adding data to the random pool that
+ * is likely to differ between two devices (or possibly even per boot).
+ * This would be things like MAC addresses or serial numbers, or the
+ * read-out of the RTC. This does *not* add any actual entropy to the
+ * pool, but it initializes the pool to different values for devices
+ * that might otherwise be identical and have very little entropy
+ * available to them (particularly common in the embedded world).
+ *
* add_input_randomness() uses the input layer interrupt timing, as well as
* the event type information from the hardware.
*
- * add_interrupt_randomness() uses the inter-interrupt timing as random
- * inputs to the entropy pool. Note that not all interrupts are good
- * sources of randomness! For example, the timer interrupts is not a
- * good choice, because the periodicity of the interrupts is too
- * regular, and hence predictable to an attacker. Network Interface
- * Controller interrupts are a better measure, since the timing of the
- * NIC interrupts are more unpredictable.
+ * add_interrupt_randomness() uses the interrupt timing as random
+ * inputs to the entropy pool. Using the cycle counters and the irq source
+ * as inputs, it feeds the randomness roughly once a second.
*
* add_disk_randomness() uses what amounts to the seek time of block
* layer request events, on a per-disk_devt basis, as input to the
@@ -248,6 +253,8 @@
#include <linux/percpu.h>
#include <linux/cryptohash.h>
#include <linux/fips.h>
+#include <linux/ptrace.h>
+#include <linux/kmemcheck.h>
#ifdef CONFIG_GENERIC_HARDIRQS
# include <linux/irq.h>
@@ -256,8 +263,12 @@
#include <asm/processor.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
+#include <asm/irq_regs.h>
#include <asm/io.h>
+#define CREATE_TRACE_POINTS
+#include <trace/events/random.h>
+
/*
* Configuration information
*/
@@ -266,6 +277,8 @@
#define SEC_XFER_SIZE 512
#define EXTRACT_SIZE 10
+#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
+
/*
* The minimum number of bits of entropy before we wake up a read on
* /dev/random. Should be enough to do a significant reseed.
@@ -420,8 +433,10 @@ struct entropy_store {
/* read-write data: */
spinlock_t lock;
unsigned add_ptr;
+ unsigned input_rotate;
int entropy_count;
- int input_rotate;
+ int entropy_total;
+ unsigned int initialized:1;
__u8 last_data[EXTRACT_SIZE];
};
@@ -454,6 +469,10 @@ static struct entropy_store nonblocking_pool = {
.pool = nonblocking_pool_data
};
+static __u32 const twist_table[8] = {
+ 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
+ 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
+
/*
* This function adds bytes into the entropy "pool". It does not
* update the entropy estimate. The caller should call
@@ -464,29 +483,24 @@ static struct entropy_store nonblocking_pool = {
* it's cheap to do so and helps slightly in the expected case where
* the entropy is concentrated in the low-order bits.
*/
-static void mix_pool_bytes_extract(struct entropy_store *r, const void *in,
- int nbytes, __u8 out[64])
+static void _mix_pool_bytes(struct entropy_store *r, const void *in,
+ int nbytes, __u8 out[64])
{
- static __u32 const twist_table[8] = {
- 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
- 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
int input_rotate;
int wordmask = r->poolinfo->poolwords - 1;
const char *bytes = in;
__u32 w;
- unsigned long flags;
- /* Taps are constant, so we can load them without holding r->lock. */
tap1 = r->poolinfo->tap1;
tap2 = r->poolinfo->tap2;
tap3 = r->poolinfo->tap3;
tap4 = r->poolinfo->tap4;
tap5 = r->poolinfo->tap5;
- spin_lock_irqsave(&r->lock, flags);
- input_rotate = r->input_rotate;
- i = r->add_ptr;
+ smp_rmb();
+ input_rotate = ACCESS_ONCE(r->input_rotate);
+ i = ACCESS_ONCE(r->add_ptr);
/* mix one byte at a time to simplify size handling and churn faster */
while (nbytes--) {
@@ -513,19 +527,61 @@ static void mix_pool_bytes_extract(struct entropy_store *r, const void *in,
input_rotate += i ? 7 : 14;
}
- r->input_rotate = input_rotate;
- r->add_ptr = i;
+ ACCESS_ONCE(r->input_rotate) = input_rotate;
+ ACCESS_ONCE(r->add_ptr) = i;
+ smp_wmb();
if (out)
for (j = 0; j < 16; j++)
((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
+}
+
+static void __mix_pool_bytes(struct entropy_store *r, const void *in,
+ int nbytes, __u8 out[64])
+{
+ trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
+ _mix_pool_bytes(r, in, nbytes, out);
+}
+
+static void mix_pool_bytes(struct entropy_store *r, const void *in,
+ int nbytes, __u8 out[64])
+{
+ unsigned long flags;
+ trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
+ spin_lock_irqsave(&r->lock, flags);
+ _mix_pool_bytes(r, in, nbytes, out);
spin_unlock_irqrestore(&r->lock, flags);
}
-static void mix_pool_bytes(struct entropy_store *r, const void *in, int bytes)
+struct fast_pool {
+ __u32 pool[4];
+ unsigned long last;
+ unsigned short count;
+ unsigned char rotate;
+ unsigned char last_timer_intr;
+};
+
+/*
+ * This is a fast mixing routine used by the interrupt randomness
+ * collector. It's hardcoded for an 128 bit pool and assumes that any
+ * locks that might be needed are taken by the caller.
+ */
+static void fast_mix(struct fast_pool *f, const void *in, int nbytes)
{
- mix_pool_bytes_extract(r, in, bytes, NULL);
+ const char *bytes = in;
+ __u32 w;
+ unsigned i = f->count;
+ unsigned input_rotate = f->rotate;
+
+ while (nbytes--) {
+ w = rol32(*bytes++, input_rotate & 31) ^ f->pool[i & 3] ^
+ f->pool[(i + 1) & 3];
+ f->pool[i & 3] = (w >> 3) ^ twist_table[w & 7];
+ input_rotate += (i++ & 3) ? 7 : 14;
+ }
+ f->count = i;
+ f->rotate = input_rotate;
}
/*
@@ -533,30 +589,38 @@ static void mix_pool_bytes(struct entropy_store *r, const void *in, int bytes)
*/
static void credit_entropy_bits(struct entropy_store *r, int nbits)
{
- unsigned long flags;
- int entropy_count;
+ int entropy_count, orig;
if (!nbits)
return;
- spin_lock_irqsave(&r->lock, flags);
-
DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);
- entropy_count = r->entropy_count;
+retry:
+ entropy_count = orig = ACCESS_ONCE(r->entropy_count);
entropy_count += nbits;
+
if (entropy_count < 0) {
DEBUG_ENT("negative entropy/overflow\n");
entropy_count = 0;
} else if (entropy_count > r->poolinfo->POOLBITS)
entropy_count = r->poolinfo->POOLBITS;
- r->entropy_count = entropy_count;
+ if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
+ goto retry;
+
+ if (!r->initialized && nbits > 0) {
+ r->entropy_total += nbits;
+ if (r->entropy_total > 128)
+ r->initialized = 1;
+ }
+
+ trace_credit_entropy_bits(r->name, nbits, entropy_count,
+ r->entropy_total, _RET_IP_);
/* should we wake readers? */
if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) {
wake_up_interruptible(&random_read_wait);
kill_fasync(&fasync, SIGIO, POLL_IN);
}
- spin_unlock_irqrestore(&r->lock, flags);
}
/*********************************************************************
@@ -572,42 +636,24 @@ struct timer_rand_state {
unsigned dont_count_entropy:1;
};
-#ifndef CONFIG_GENERIC_HARDIRQS
-
-static struct timer_rand_state *irq_timer_state[NR_IRQS];
-
-static struct timer_rand_state *get_timer_rand_state(unsigned int irq)
-{
- return irq_timer_state[irq];
-}
-
-static void set_timer_rand_state(unsigned int irq,
- struct timer_rand_state *state)
-{
- irq_timer_state[irq] = state;
-}
-
-#else
-
-static struct timer_rand_state *get_timer_rand_state(unsigned int irq)
-{
- struct irq_desc *desc;
-
- desc = irq_to_desc(irq);
-
- return desc->timer_rand_state;
-}
-
-static void set_timer_rand_state(unsigned int irq,
- struct timer_rand_state *state)
+/*
+ * Add device- or boot-specific data to the input and nonblocking
+ * pools to help initialize them to unique values.
+ *
+ * None of this adds any entropy, it is meant to avoid the
+ * problem of the nonblocking pool having similar initial state
+ * across largely identical devices.
+ */
+void add_device_randomness(const void *buf, unsigned int size)
{
- struct irq_desc *desc;
+ unsigned long time = get_cycles() ^ jiffies;
- desc = irq_to_desc(irq);
-
- desc->timer_rand_state = state;
+ mix_pool_bytes(&input_pool, buf, size, NULL);
+ mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
+ mix_pool_bytes(&nonblocking_pool, buf, size, NULL);
+ mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);
}
-#endif
+EXPORT_SYMBOL(add_device_randomness);
static struct timer_rand_state input_timer_state;
@@ -637,13 +683,9 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
goto out;
sample.jiffies = jiffies;
-
- /* Use arch random value, fall back to cycles */
- if (!arch_get_random_int(&sample.cycles))
- sample.cycles = get_cycles();
-
+ sample.cycles = get_cycles();
sample.num = num;
- mix_pool_bytes(&input_pool, &sample, sizeof(sample));
+ mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL);
/*
* Calculate number of bits of randomness we probably added.
@@ -700,17 +742,48 @@ void add_input_randomness(unsigned int type, unsigned int code,
}
EXPORT_SYMBOL_GPL(add_input_randomness);
-void add_interrupt_randomness(int irq)
+static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
+
+void add_interrupt_randomness(int irq, int irq_flags)
{
- struct timer_rand_state *state;
+ struct entropy_store *r;
+ struct fast_pool *fast_pool = &__get_cpu_var(irq_randomness);
+ struct pt_regs *regs = get_irq_regs();
+ unsigned long now = jiffies;
+ __u32 input[4], cycles = get_cycles();
+
+ input[0] = cycles ^ jiffies;
+ input[1] = irq;
+ if (regs) {
+ __u64 ip = instruction_pointer(regs);
+ input[2] = ip;
+ input[3] = ip >> 32;
+ }
- state = get_timer_rand_state(irq);
+ fast_mix(fast_pool, input, sizeof(input));
- if (state == NULL)
+ if ((fast_pool->count & 1023) &&
+ !time_after(now, fast_pool->last + HZ))
return;
- DEBUG_ENT("irq event %d\n", irq);
- add_timer_randomness(state, 0x100 + irq);
+ fast_pool->last = now;
+
+ 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.
+ */
+ if (cycles == 0) {
+ if (irq_flags & __IRQF_TIMER) {
+ if (fast_pool->last_timer_intr)
+ return;
+ fast_pool->last_timer_intr = 1;
+ } else
+ fast_pool->last_timer_intr = 0;
+ }
+ credit_entropy_bits(r, 1);
}
#ifdef CONFIG_BLOCK
@@ -742,7 +815,7 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf,
*/
static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
{
- __u32 tmp[OUTPUT_POOL_WORDS];
+ __u32 tmp[OUTPUT_POOL_WORDS];
if (r->pull && r->entropy_count < nbytes * 8 &&
r->entropy_count < r->poolinfo->POOLBITS) {
@@ -761,7 +834,7 @@ static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
bytes = extract_entropy(r->pull, tmp, bytes,
random_read_wakeup_thresh / 8, rsvd);
- mix_pool_bytes(r, tmp, bytes);
+ mix_pool_bytes(r, tmp, bytes, NULL);
credit_entropy_bits(r, bytes*8);
}
}
@@ -820,13 +893,19 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
static void extract_buf(struct entropy_store *r, __u8 *out)
{
int i;
- __u32 hash[5], workspace[SHA_WORKSPACE_WORDS];
+ union {
+ __u32 w[5];
+ unsigned long l[LONGS(EXTRACT_SIZE)];
+ } hash;
+ __u32 workspace[SHA_WORKSPACE_WORDS];
__u8 extract[64];
+ unsigned long flags;
/* Generate a hash across the pool, 16 words (512 bits) at a time */
- sha_init(hash);
+ sha_init(hash.w);
+ spin_lock_irqsave(&r->lock, flags);
for (i = 0; i < r->poolinfo->poolwords; i += 16)
- sha_transform(hash, (__u8 *)(r->pool + i), workspace);
+ sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
/*
* We mix the hash back into the pool to prevent backtracking
@@ -837,13 +916,14 @@ static void extract_buf(struct entropy_store *r, __u8 *out)
* brute-forcing the feedback as hard as brute-forcing the
* hash.
*/
- mix_pool_bytes_extract(r, hash, sizeof(hash), extract);
+ __mix_pool_bytes(r, hash.w, sizeof(hash.w), extract);
+ spin_unlock_irqrestore(&r->lock, flags);
/*
* To avoid duplicates, we atomically extract a portion of the
* pool while mixing, and hash one final time.
*/
- sha_transform(hash, extract, workspace);
+ sha_transform(hash.w, extract, workspace);
memset(extract, 0, sizeof(extract));
memset(workspace, 0, sizeof(workspace));
@@ -852,20 +932,32 @@ static void extract_buf(struct entropy_store *r, __u8 *out)
* pattern, we fold it in half. Thus, we always feed back
* twice as much data as we output.
*/
- hash[0] ^= hash[3];
- hash[1] ^= hash[4];
- hash[2] ^= rol32(hash[2], 16);
- memcpy(out, hash, EXTRACT_SIZE);
- memset(hash, 0, sizeof(hash));
+ hash.w[0] ^= hash.w[3];
+ hash.w[1] ^= hash.w[4];
+ hash.w[2] ^= rol32(hash.w[2], 16);
+
+ /*
+ * If we have a architectural hardware random number
+ * generator, mix that in, too.
+ */
+ for (i = 0; i < LONGS(EXTRACT_SIZE); i++) {
+ unsigned long v;
+ if (!arch_get_random_long(&v))
+ break;
+ hash.l[i] ^= v;
+ }
+
+ memcpy(out, &hash, EXTRACT_SIZE);
+ memset(&hash, 0, sizeof(hash));
}
static ssize_t extract_entropy(struct entropy_store *r, void *buf,
- size_t nbytes, int min, int reserved)
+ size_t nbytes, int min, int reserved)
{
ssize_t ret = 0, i;
__u8 tmp[EXTRACT_SIZE];
- unsigned long flags;
+ trace_extract_entropy(r->name, nbytes, r->entropy_count, _RET_IP_);
xfer_secondary_pool(r, nbytes);
nbytes = account(r, nbytes, min, reserved);
@@ -873,6 +965,8 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf,
extract_buf(r, tmp);
if (fips_enabled) {
+ unsigned long flags;
+
spin_lock_irqsave(&r->lock, flags);
if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
panic("Hardware RNG duplicated output!\n");
@@ -898,6 +992,7 @@ static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
ssize_t ret = 0, i;
__u8 tmp[EXTRACT_SIZE];
+ trace_extract_entropy_user(r->name, nbytes, r->entropy_count, _RET_IP_);
xfer_secondary_pool(r, nbytes);
nbytes = account(r, nbytes, 0, 0);
@@ -931,17 +1026,35 @@ 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 seeding TCP sequence
- * numbers, etc.
+ * 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.
*/
void get_random_bytes(void *buf, int nbytes)
{
+ extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
+}
+EXPORT_SYMBOL(get_random_bytes);
+
+/*
+ * This function will use the architecture-specific hardware random
+ * number generator if it is available. The arch-specific hw RNG will
+ * almost certainly be faster than what we can do in software, but it
+ * is impossible to verify that it is implemented securely (as
+ * opposed, to, say, the AES encryption of a sequence number using a
+ * key known by the NSA). So it's useful if we need the speed, but
+ * only if we're willing to trust the hardware manufacturer not to
+ * have put in a back door.
+ */
+void get_random_bytes_arch(void *buf, int nbytes)
+{
char *p = buf;
+ trace_get_random_bytes(nbytes, _RET_IP_);
while (nbytes) {
unsigned long v;
int chunk = min(nbytes, (int)sizeof(unsigned long));
-
+
if (!arch_get_random_long(&v))
break;
@@ -950,9 +1063,11 @@ void get_random_bytes(void *buf, int nbytes)
nbytes -= chunk;
}
- extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
+ if (nbytes)
+ extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
}
-EXPORT_SYMBOL(get_random_bytes);
+EXPORT_SYMBOL(get_random_bytes_arch);
+
/*
* init_std_data - initialize pool with system data
@@ -966,23 +1081,30 @@ EXPORT_SYMBOL(get_random_bytes);
static void init_std_data(struct entropy_store *r)
{
int i;
- ktime_t now;
- unsigned long flags;
+ ktime_t now = ktime_get_real();
+ unsigned long rv;
- spin_lock_irqsave(&r->lock, flags);
r->entropy_count = 0;
- spin_unlock_irqrestore(&r->lock, flags);
-
- now = ktime_get_real();
- mix_pool_bytes(r, &now, sizeof(now));
- for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof flags) {
- if (!arch_get_random_long(&flags))
+ r->entropy_total = 0;
+ mix_pool_bytes(r, &now, sizeof(now), NULL);
+ for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof(rv)) {
+ if (!arch_get_random_long(&rv))
break;
- mix_pool_bytes(r, &flags, sizeof(flags));
+ mix_pool_bytes(r, &rv, sizeof(rv), NULL);
}
- mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
+ mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL);
}
+/*
+ * Note that setup_arch() may call add_device_randomness()
+ * long before we get here. This allows seeding of the pools
+ * with some platform dependent data very early in the boot
+ * process. But it limits our options here. We must use
+ * statically allocated structures that already have all
+ * initializations complete at compile time. We should also
+ * take care not to overwrite the precious per platform data
+ * we were given.
+ */
static int rand_initialize(void)
{
init_std_data(&input_pool);
@@ -992,24 +1114,6 @@ static int rand_initialize(void)
}
module_init(rand_initialize);
-void rand_initialize_irq(int irq)
-{
- struct timer_rand_state *state;
-
- state = get_timer_rand_state(irq);
-
- if (state)
- return;
-
- /*
- * If kzalloc returns null, we just won't use that entropy
- * source.
- */
- state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
- if (state)
- set_timer_rand_state(irq, state);
-}
-
#ifdef CONFIG_BLOCK
void rand_initialize_disk(struct gendisk *disk)
{
@@ -1117,7 +1221,7 @@ write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
count -= bytes;
p += bytes;
- mix_pool_bytes(r, buf, bytes);
+ mix_pool_bytes(r, buf, bytes, NULL);
cond_resched();
}