Commit message: random: make get_random_int() more random

It's a really simple patch that basically just open-codes the current
"secure_ip_id()" call, but when open-coding it we now use a _static_
hashing area, so that it gets updated every time.

And to make sure somebody can't just start from the same original seed of
all-zeroes, and then do the "half_md4_transform()" over and over until
they get the same sequence as the kernel has, each iteration also mixes in
the same old "current->pid + jiffies" we used - so we should now have a
regular strong pseudo-number generator, but we also have one that doesn't
have a single seed.

Note: the "pid + jiffies" is just meant to be a tiny tiny bit of noise. It
has no real meaning. It could be anything. I just picked the previous
seed, it's just that now we keep the state in between calls and that will
feed into the next result, and that should make all the difference.

I made that hash be a per-cpu data just to avoid cache-line ping-pong:
having multiple CPU's write to the same data would be fine for randomness,
and add yet another layer of chaos to it, but since get_random_int() is
supposed to be a fast interface I did it that way instead. I considered
using "__raw_get_cpu_var()" to avoid any preemption overhead while still
getting the hash be _mostly_ ping-pong free, but in the end good taste won
out.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
CVE: CVE-2009-3238
CWE: CWE-310
Vulnerability description: The get_random_int function in drivers/char/random.c in the Linux kernel before 2.6.30 produces insufficiently random numbers, which allows attackers to predict the return value, and possibly defeat protection mechanisms based on randomization, via vectors that leverage the function's tendency to "return the same value over and over again for long stretches of time."

Project: linux-2.6

static int uuid_strategy(ctl_table *table,
			 void __user *oldval, size_t __user *oldlenp,
			 void __user *newval, size_t newlen)
{
	unsigned char tmp_uuid[16], *uuid;
	unsigned int len;

	if (!oldval || !oldlenp)
		return 1;

	uuid = table->data;
	if (!uuid) {
		uuid = tmp_uuid;
		uuid[8] = 0;
	}
	if (uuid[8] == 0)
		generate_random_uuid(uuid);

	if (get_user(len, oldlenp))
		return -EFAULT;
	if (len) {
		if (len > 16)
			len = 16;
		if (copy_to_user(oldval, uuid, len) ||
		    put_user(len, oldlenp))
			return -EFAULT;
	}
	return 1;
}

Project: linux-2.6

unsigned int get_random_int(void)
{
	struct keydata *keyptr;
	__u32 *hash = get_cpu_var(get_random_int_hash);
	int ret;

	keyptr = get_keyptr();
	hash[0] += current->pid + jiffies + get_cycles() + (int)(long)&ret;

	ret = half_md4_transform(hash, keyptr->secret);
	put_cpu_var(get_random_int_hash);

	return ret;
}

Project: linux-2.6

void generate_random_uuid(unsigned char uuid_out[16])
{
	get_random_bytes(uuid_out, 16);
	/* Set UUID version to 4 --- truely random generation */
	uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
	/* Set the UUID variant to DCE */
	uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
}

Project: linux-2.6

static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
				    size_t nbytes)
{
	ssize_t ret = 0, i;
	__u8 tmp[EXTRACT_SIZE];

	xfer_secondary_pool(r, nbytes);
	nbytes = account(r, nbytes, 0, 0);

	while (nbytes) {
		if (need_resched()) {
			if (signal_pending(current)) {
				if (ret == 0)
					ret = -ERESTARTSYS;
				break;
			}
			schedule();
		}

		extract_buf(r, tmp);
		i = min_t(int, nbytes, EXTRACT_SIZE);
		if (copy_to_user(buf, tmp, i)) {
			ret = -EFAULT;
			break;
		}

		nbytes -= i;
		buf += i;
		ret += i;
	}

	/* Wipe data just returned from memory */
	memset(tmp, 0, sizeof(tmp));

	return ret;
}

Project: linux-2.6

static struct timer_rand_state *get_timer_rand_state(unsigned int irq)
{
	return irq_timer_state[irq];
}

Project: linux-2.6

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);
}

Project: linux-2.6

static void credit_entropy_bits(struct entropy_store *r, int nbits)
{
	unsigned long flags;
	int entropy_count;

	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;
	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;

	/* 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);
}

Project: linux-2.6

void add_interrupt_randomness(int irq)
{
	struct timer_rand_state *state;

	state = get_timer_rand_state(irq);

	if (state == NULL)
		return;

	DEBUG_ENT("irq event %d\n", irq);
	add_timer_randomness(state, 0x100 + irq);
}

Project: linux-2.6

static size_t account(struct entropy_store *r, size_t nbytes, int min,
		      int reserved)
{
	unsigned long flags;

	/* Hold lock while accounting */
	spin_lock_irqsave(&r->lock, flags);

	BUG_ON(r->entropy_count > r->poolinfo->POOLBITS);
	DEBUG_ENT("trying to extract %d bits from %s\n",
		  nbytes * 8, r->name);

	/* Can we pull enough? */
	if (r->entropy_count / 8 < min + reserved) {
		nbytes = 0;
	} else {
		/* If limited, never pull more than available */
		if (r->limit && nbytes + reserved >= r->entropy_count / 8)
			nbytes = r->entropy_count/8 - reserved;

		if (r->entropy_count / 8 >= nbytes + reserved)
			r->entropy_count -= nbytes*8;
		else
			r->entropy_count = reserved;

		if (r->entropy_count < random_write_wakeup_thresh) {
			wake_up_interruptible(&random_write_wait);
			kill_fasync(&fasync, SIGIO, POLL_OUT);
		}
	}

	DEBUG_ENT("debiting %d entropy credits from %s%s\n",
		  nbytes * 8, r->name, r->limit ? "" : " (unlimited)");

	spin_unlock_irqrestore(&r->lock, flags);

	return nbytes;
}

Project: linux-2.6

static void mix_pool_bytes(struct entropy_store *r, const void *in, int bytes)
{
       mix_pool_bytes_extract(r, in, bytes, NULL);
}

Project: linux-2.6

randomize_range(unsigned long start, unsigned long end, unsigned long len)
{
	unsigned long range = end - len - start;

	if (end <= start + len)
		return 0;
	return PAGE_ALIGN(get_random_int() % range + start);
}

Project: linux-2.6

write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
{
	size_t bytes;
	__u32 buf[16];
	const char __user *p = buffer;

	while (count > 0) {
		bytes = min(count, sizeof(buf));
		if (copy_from_user(&buf, p, bytes))
			return -EFAULT;

		count -= bytes;
		p += bytes;

		mix_pool_bytes(r, buf, bytes);
		cond_resched();
	}

	return 0;
}

Project: linux-2.6

random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
{
	ssize_t n, retval = 0, count = 0;

	if (nbytes == 0)
		return 0;

	while (nbytes > 0) {
		n = nbytes;
		if (n > SEC_XFER_SIZE)
			n = SEC_XFER_SIZE;

		DEBUG_ENT("reading %d bits\n", n*8);

		n = extract_entropy_user(&blocking_pool, buf, n);

		DEBUG_ENT("read got %d bits (%d still needed)\n",
			  n*8, (nbytes-n)*8);

		if (n == 0) {
			if (file->f_flags & O_NONBLOCK) {
				retval = -EAGAIN;
				break;
			}

			DEBUG_ENT("sleeping?\n");

			wait_event_interruptible(random_read_wait,
				input_pool.entropy_count >=
						 random_read_wakeup_thresh);

			DEBUG_ENT("awake\n");

			if (signal_pending(current)) {
				retval = -ERESTARTSYS;
				break;
			}

			continue;
		}

		if (n < 0) {
			retval = n;
			break;
		}
		count += n;
		buf += n;
		nbytes -= n;
		break;		/* This break makes the device work */
				/* like a named pipe */
	}

	/*
	 * If we gave the user some bytes, update the access time.
	 */
	if (count)
		file_accessed(file);

	return (count ? count : retval);
}

Project: linux-2.6

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;
}

Project: linux-2.6

static ssize_t random_write(struct file *file, const char __user *buffer,
			    size_t count, loff_t *ppos)
{
	size_t ret;
	struct inode *inode = file->f_path.dentry->d_inode;

	ret = write_pool(&blocking_pool, buffer, count);
	if (ret)
		return ret;
	ret = write_pool(&nonblocking_pool, buffer, count);
	if (ret)
		return ret;

	inode->i_mtime = current_fs_time(inode->i_sb);
	mark_inode_dirty(inode);
	return (ssize_t)count;
}

Project: linux-2.6

static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
{
	int size, ent_count;
	int __user *p = (int __user *)arg;
	int retval;

	switch (cmd) {
	case RNDGETENTCNT:
		/* inherently racy, no point locking */
		if (put_user(input_pool.entropy_count, p))
			return -EFAULT;
		return 0;
	case RNDADDTOENTCNT:
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		if (get_user(ent_count, p))
			return -EFAULT;
		credit_entropy_bits(&input_pool, ent_count);
		return 0;
	case RNDADDENTROPY:
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		if (get_user(ent_count, p++))
			return -EFAULT;
		if (ent_count < 0)
			return -EINVAL;
		if (get_user(size, p++))
			return -EFAULT;
		retval = write_pool(&input_pool, (const char __user *)p,
				    size);
		if (retval < 0)
			return retval;
		credit_entropy_bits(&input_pool, ent_count);
		return 0;
	case RNDZAPENTCNT:
	case RNDCLEARPOOL:
		/* Clear the entropy pool counters. */
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		rand_initialize();
		return 0;
	default:
		return -EINVAL;
	}
}

Project: linux-2.6

void add_disk_randomness(struct gendisk *disk)
{
	if (!disk || !disk->random)
		return;
	/* first major is 1, so we get >= 0x200 here */
	DEBUG_ENT("disk event %d:%d\n",
		  MAJOR(disk_devt(disk)), MINOR(disk_devt(disk)));

	add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
}

Project: linux-2.6

static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
{
	__u32 tmp[OUTPUT_POOL_WORDS];

	if (r->pull && r->entropy_count < nbytes * 8 &&
	    r->entropy_count < r->poolinfo->POOLBITS) {
		/* If we're limited, always leave two wakeup worth's BITS */
		int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
		int bytes = nbytes;

		/* pull at least as many as BYTES as wakeup BITS */
		bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
		/* but never more than the buffer size */
		bytes = min_t(int, bytes, sizeof(tmp));

		DEBUG_ENT("going to reseed %s with %d bits "
			  "(%d of %d requested)\n",
			  r->name, bytes * 8, nbytes * 8, r->entropy_count);

		bytes = extract_entropy(r->pull, tmp, bytes,
					random_read_wakeup_thresh / 8, rsvd);
		mix_pool_bytes(r, tmp, bytes);
		credit_entropy_bits(r, bytes*8);
	}
}

Project: linux-2.6

static ssize_t extract_entropy(struct entropy_store *r, void *buf,
			       size_t nbytes, int min, int reserved)
{
	ssize_t ret = 0, i;
	__u8 tmp[EXTRACT_SIZE];

	xfer_secondary_pool(r, nbytes);
	nbytes = account(r, nbytes, min, reserved);

	while (nbytes) {
		extract_buf(r, tmp);
		i = min_t(int, nbytes, EXTRACT_SIZE);
		memcpy(buf, tmp, i);
		nbytes -= i;
		buf += i;
		ret += i;
	}

	/* Wipe data just returned from memory */
	memset(tmp, 0, sizeof(tmp));

	return ret;
}

Project: linux-2.6

random_poll(struct file *file, poll_table * wait)
{
	unsigned int mask;

	poll_wait(file, &random_read_wait, wait);
	poll_wait(file, &random_write_wait, wait);
	mask = 0;
	if (input_pool.entropy_count >= random_read_wakeup_thresh)
		mask |= POLLIN | POLLRDNORM;
	if (input_pool.entropy_count < random_write_wakeup_thresh)
		mask |= POLLOUT | POLLWRNORM;
	return mask;
}

Project: linux-2.6

static void init_std_data(struct entropy_store *r)
{
	ktime_t now;
	unsigned long flags;

	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));
	mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
}

Project: linux-2.6

static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
{
	struct {
		cycles_t cycles;
		long jiffies;
		unsigned num;
	} sample;
	long delta, delta2, delta3;

	preempt_disable();
	/* if over the trickle threshold, use only 1 in 4096 samples */
	if (input_pool.entropy_count > trickle_thresh &&
	    (__get_cpu_var(trickle_count)++ & 0xfff))
		goto out;

	sample.jiffies = jiffies;
	sample.cycles = get_cycles();
	sample.num = num;
	mix_pool_bytes(&input_pool, &sample, sizeof(sample));

	/*
	 * Calculate number of bits of randomness we probably added.
	 * We take into account the first, second and third-order deltas
	 * in order to make our estimate.
	 */

	if (!state->dont_count_entropy) {
		delta = sample.jiffies - state->last_time;
		state->last_time = sample.jiffies;

		delta2 = delta - state->last_delta;
		state->last_delta = delta;

		delta3 = delta2 - state->last_delta2;
		state->last_delta2 = delta2;

		if (delta < 0)
			delta = -delta;
		if (delta2 < 0)
			delta2 = -delta2;
		if (delta3 < 0)
			delta3 = -delta3;
		if (delta > delta2)
			delta = delta2;
		if (delta > delta3)
			delta = delta3;

		/*
		 * delta is now minimum absolute delta.
		 * Round down by 1 bit on general principles,
		 * and limit entropy entimate to 12 bits.
		 */
		credit_entropy_bits(&input_pool,
				    min_t(int, fls(delta>>1), 11));
	}
out:
	preempt_enable();
}

Project: linux-2.6

void get_random_bytes(void *buf, int nbytes)
{
	extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
}

Project: linux-2.6

static void set_timer_rand_state(unsigned int irq,
				 struct timer_rand_state *state)
{
	struct irq_desc *desc;

	desc = irq_to_desc(irq);

	desc->timer_rand_state = state;
}

Project: linux-2.6

urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
{
	return extract_entropy_user(&nonblocking_pool, buf, nbytes);
}

Project: linux-2.6

static void mix_pool_bytes_extract(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;

	/* mix one byte at a time to simplify size handling and churn faster */
	while (nbytes--) {
		w = rol32(*bytes++, input_rotate & 31);
		i = (i - 1) & wordmask;

		/* XOR in the various taps */
		w ^= r->pool[i];
		w ^= r->pool[(i + tap1) & wordmask];
		w ^= r->pool[(i + tap2) & wordmask];
		w ^= r->pool[(i + tap3) & wordmask];
		w ^= r->pool[(i + tap4) & wordmask];
		w ^= r->pool[(i + tap5) & wordmask];

		/* Mix the result back in with a twist */
		r->pool[i] = (w >> 3) ^ twist_table[w & 7];

		/*
		 * Normally, we add 7 bits of rotation to the pool.
		 * At the beginning of the pool, add an extra 7 bits
		 * rotation, so that successive passes spread the
		 * input bits across the pool evenly.
		 */
		input_rotate += i ? 7 : 14;
	}

	r->input_rotate = input_rotate;
	r->add_ptr = i;

	if (out)
		for (j = 0; j < 16; j++)
			((__u32 *)out)[j] = r->pool[(i - j) & wordmask];

	spin_unlock_irqrestore(&r->lock, flags);
}

Project: linux-2.6

static int proc_do_uuid(ctl_table *table, int write, struct file *filp,
			void __user *buffer, size_t *lenp, loff_t *ppos)
{
	ctl_table fake_table;
	unsigned char buf[64], tmp_uuid[16], *uuid;

	uuid = table->data;
	if (!uuid) {
		uuid = tmp_uuid;
		uuid[8] = 0;
	}
	if (uuid[8] == 0)
		generate_random_uuid(uuid);

	sprintf(buf, "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-"
		"%02x%02x%02x%02x%02x%02x",
		uuid[0],  uuid[1],  uuid[2],  uuid[3],
		uuid[4],  uuid[5],  uuid[6],  uuid[7],
		uuid[8],  uuid[9],  uuid[10], uuid[11],
		uuid[12], uuid[13], uuid[14], uuid[15]);
	fake_table.data = buf;
	fake_table.maxlen = sizeof(buf);

	return proc_dostring(&fake_table, write, filp, buffer, lenp, ppos);
}

Project: linux-2.6

static int rand_initialize(void)
{
	init_std_data(&input_pool);
	init_std_data(&blocking_pool);
	init_std_data(&nonblocking_pool);
	return 0;
}

Project: linux-2.6

static void set_timer_rand_state(unsigned int irq,
				 struct timer_rand_state *state)
{
	irq_timer_state[irq] = state;
}

Project: linux-2.6

static void extract_buf(struct entropy_store *r, __u8 *out)
{
	int i;
	__u32 hash[5], workspace[SHA_WORKSPACE_WORDS];
	__u8 extract[64];

	/* Generate a hash across the pool, 16 words (512 bits) at a time */
	sha_init(hash);
	for (i = 0; i < r->poolinfo->poolwords; i += 16)
		sha_transform(hash, (__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
	 * plus the current outputs, and attempts to find previous
	 * ouputs), unless the hash function can be inverted. By
	 * mixing at least a SHA1 worth of hash data back, we make
	 * brute-forcing the feedback as hard as brute-forcing the
	 * hash.
	 */
	mix_pool_bytes_extract(r, hash, sizeof(hash), extract);

	/*
	 * To avoid duplicates, we atomically extract a portion of the
	 * pool while mixing, and hash one final time.
	 */
	sha_transform(hash, extract, workspace);
	memset(extract, 0, sizeof(extract));
	memset(workspace, 0, sizeof(workspace));

	/*
	 * In case the hash function has some recognizable output
	 * 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));
}

Project: linux-2.6

void rand_initialize_disk(struct gendisk *disk)
{
	struct timer_rand_state *state;

	/*
	 * If kzalloc returns null, we just won't use that entropy
	 * source.
	 */
	state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
	if (state)
		disk->random = state;
}

Project: linux-2.6

void add_input_randomness(unsigned int type, unsigned int code,
				 unsigned int value)
{
	static unsigned char last_value;

	/* ignore autorepeat and the like */
	if (value == last_value)
		return;

	DEBUG_ENT("input event\n");
	last_value = value;
	add_timer_randomness(&input_timer_state,
			     (type << 4) ^ code ^ (code >> 4) ^ value);
}