diff options
Diffstat (limited to 'drivers/char/random.c')
| -rw-r--r-- | drivers/char/random.c | 655 |
1 files changed, 410 insertions, 245 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 7737b5bd26a..429b75bb60e 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -255,6 +255,7 @@ #include <linux/fips.h> #include <linux/ptrace.h> #include <linux/kmemcheck.h> +#include <linux/workqueue.h> #include <linux/irq.h> #include <asm/processor.h> @@ -269,14 +270,28 @@ /* * Configuration information */ -#define INPUT_POOL_WORDS 128 -#define OUTPUT_POOL_WORDS 32 -#define SEC_XFER_SIZE 512 -#define EXTRACT_SIZE 10 +#define INPUT_POOL_SHIFT 12 +#define INPUT_POOL_WORDS (1 << (INPUT_POOL_SHIFT-5)) +#define OUTPUT_POOL_SHIFT 10 +#define OUTPUT_POOL_WORDS (1 << (OUTPUT_POOL_SHIFT-5)) +#define SEC_XFER_SIZE 512 +#define EXTRACT_SIZE 10 + +#define DEBUG_RANDOM_BOOT 0 #define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long)) /* + * To allow fractional bits to be tracked, the entropy_count field is + * denominated in units of 1/8th bits. + * + * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in + * credit_entropy_bits() needs to be 64 bits wide. + */ +#define ENTROPY_SHIFT 3 +#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT) + +/* * The minimum number of bits of entropy before we wake up a read on * /dev/random. Should be enough to do a significant reseed. */ @@ -287,108 +302,100 @@ static int random_read_wakeup_thresh = 64; * should wake up processes which are selecting or polling on write * access to /dev/random. */ -static int random_write_wakeup_thresh = 128; +static int random_write_wakeup_thresh = 28 * OUTPUT_POOL_WORDS; /* - * When the input pool goes over trickle_thresh, start dropping most - * samples to avoid wasting CPU time and reduce lock contention. + * The minimum number of seconds between urandom pool resending. 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 trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28; - -static DEFINE_PER_CPU(int, trickle_count); +static int random_min_urandom_seed = 60; /* - * A pool of size .poolwords is stirred with a primitive polynomial - * of degree .poolwords over GF(2). The taps for various sizes are - * defined below. They are chosen to be evenly spaced (minimum RMS - * distance from evenly spaced; the numbers in the comments are a - * scaled squared error sum) except for the last tap, which is 1 to - * get the twisting happening as fast as possible. + * Originally, we used a primitive polynomial of degree .poolwords + * over GF(2). The taps for various sizes are defined below. They + * were chosen to be evenly spaced except for the last tap, which is 1 + * to get the twisting happening as fast as possible. + * + * For the purposes of better mixing, we use the CRC-32 polynomial as + * well to make a (modified) twisted Generalized Feedback Shift + * 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 + * Simulation 4:254-266) + * + * Thanks to Colin Plumb for suggesting this. + * + * The mixing operation is much less sensitive than the output hash, + * where we use SHA-1. All that we want of mixing operation is that + * it be a good non-cryptographic hash; i.e. it not produce collisions + * when fed "random" data of the sort we expect to see. As long as + * the pool state differs for different inputs, we have preserved the + * input entropy and done a good job. The fact that an intelligent + * attacker can construct inputs that will produce controlled + * alterations to the pool's state is not important because we don't + * consider such inputs to contribute any randomness. The only + * property we need with respect to them is that the attacker can't + * increase his/her knowledge of the pool's state. Since all + * additions are reversible (knowing the final state and the input, + * you can reconstruct the initial state), if an attacker has any + * uncertainty about the initial state, he/she can only shuffle that + * uncertainty about, but never cause any collisions (which would + * decrease the uncertainty). + * + * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and + * Videau in their paper, "The Linux Pseudorandom Number Generator + * Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their + * paper, they point out that we are not using a true Twisted GFSR, + * since Matsumoto & Kurita used a trinomial feedback polynomial (that + * is, with only three taps, instead of the six that we are using). + * As a result, the resulting polynomial is neither primitive nor + * irreducible, and hence does not have a maximal period over + * GF(2**32). They suggest a slight change to the generator + * polynomial which improves the resulting TGFSR polynomial to be + * irreducible, which we have made here. */ static struct poolinfo { - int poolwords; + int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits; +#define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5) int tap1, tap2, tap3, tap4, tap5; } poolinfo_table[] = { - /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */ - { 128, 103, 76, 51, 25, 1 }, - /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */ - { 32, 26, 20, 14, 7, 1 }, + /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */ + /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */ + { S(128), 104, 76, 51, 25, 1 }, + /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */ + /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */ + { S(32), 26, 19, 14, 7, 1 }, #if 0 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */ - { 2048, 1638, 1231, 819, 411, 1 }, + { S(2048), 1638, 1231, 819, 411, 1 }, /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */ - { 1024, 817, 615, 412, 204, 1 }, + { S(1024), 817, 615, 412, 204, 1 }, /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */ - { 1024, 819, 616, 410, 207, 2 }, + { S(1024), 819, 616, 410, 207, 2 }, /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */ - { 512, 411, 308, 208, 104, 1 }, + { S(512), 411, 308, 208, 104, 1 }, /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */ - { 512, 409, 307, 206, 102, 2 }, + { S(512), 409, 307, 206, 102, 2 }, /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */ - { 512, 409, 309, 205, 103, 2 }, + { S(512), 409, 309, 205, 103, 2 }, /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */ - { 256, 205, 155, 101, 52, 1 }, + { S(256), 205, 155, 101, 52, 1 }, /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */ - { 128, 103, 78, 51, 27, 2 }, + { S(128), 103, 78, 51, 27, 2 }, /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */ - { 64, 52, 39, 26, 14, 1 }, + { S(64), 52, 39, 26, 14, 1 }, #endif }; -#define POOLBITS poolwords*32 -#define POOLBYTES poolwords*4 - -/* - * For the purposes of better mixing, we use the CRC-32 polynomial as - * well to make a twisted Generalized Feedback Shift Reigster - * - * (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 Simulation 4:254-266) - * - * Thanks to Colin Plumb for suggesting this. - * - * We have not analyzed the resultant polynomial to prove it primitive; - * in fact it almost certainly isn't. Nonetheless, the irreducible factors - * of a random large-degree polynomial over GF(2) are more than large enough - * that periodicity is not a concern. - * - * The input hash is much less sensitive than the output hash. All - * that we want of it is that it be a good non-cryptographic hash; - * i.e. it not produce collisions when fed "random" data of the sort - * we expect to see. As long as the pool state differs for different - * inputs, we have preserved the input entropy and done a good job. - * The fact that an intelligent attacker can construct inputs that - * will produce controlled alterations to the pool's state is not - * important because we don't consider such inputs to contribute any - * randomness. The only property we need with respect to them is that - * the attacker can't increase his/her knowledge of the pool's state. - * Since all additions are reversible (knowing the final state and the - * input, you can reconstruct the initial state), if an attacker has - * any uncertainty about the initial state, he/she can only shuffle - * that uncertainty about, but never cause any collisions (which would - * decrease the uncertainty). - * - * The chosen system lets the state of the pool be (essentially) the input - * modulo the generator polymnomial. Now, for random primitive polynomials, - * this is a universal class of hash functions, meaning that the chance - * of a collision is limited by the attacker's knowledge of the generator - * polynomail, so if it is chosen at random, an attacker can never force - * a collision. Here, we use a fixed polynomial, but we *can* assume that - * ###--> it is unknown to the processes generating the input entropy. <-### - * Because of this important property, this is a good, collision-resistant - * hash; hash collisions will occur no more often than chance. - */ - /* * Static global variables */ @@ -396,17 +403,6 @@ static DECLARE_WAIT_QUEUE_HEAD(random_read_wait); static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); static struct fasync_struct *fasync; -static bool debug; -module_param(debug, bool, 0644); -#define DEBUG_ENT(fmt, arg...) do { \ - if (debug) \ - printk(KERN_DEBUG "random %04d %04d %04d: " \ - fmt,\ - input_pool.entropy_count,\ - blocking_pool.entropy_count,\ - nonblocking_pool.entropy_count,\ - ## arg); } while (0) - /********************************************************************** * * OS independent entropy store. Here are the functions which handle @@ -417,23 +413,26 @@ module_param(debug, bool, 0644); struct entropy_store; struct entropy_store { /* read-only data: */ - struct poolinfo *poolinfo; + const struct poolinfo *poolinfo; __u32 *pool; const char *name; struct entropy_store *pull; - int limit; + struct work_struct push_work; /* read-write data: */ + unsigned long last_pulled; spinlock_t lock; - unsigned add_ptr; - unsigned input_rotate; + unsigned short add_ptr; + unsigned short input_rotate; int entropy_count; int entropy_total; unsigned int initialized:1; - bool last_data_init; + unsigned int limit:1; + unsigned int last_data_init:1; __u8 last_data[EXTRACT_SIZE]; }; +static void push_to_pool(struct work_struct *work); static __u32 input_pool_data[INPUT_POOL_WORDS]; static __u32 blocking_pool_data[OUTPUT_POOL_WORDS]; static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS]; @@ -452,7 +451,9 @@ static struct entropy_store blocking_pool = { .limit = 1, .pull = &input_pool, .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock), - .pool = blocking_pool_data + .pool = blocking_pool_data, + .push_work = __WORK_INITIALIZER(blocking_pool.push_work, + push_to_pool), }; static struct entropy_store nonblocking_pool = { @@ -460,7 +461,9 @@ static struct entropy_store nonblocking_pool = { .name = "nonblocking", .pull = &input_pool, .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock), - .pool = nonblocking_pool_data + .pool = nonblocking_pool_data, + .push_work = __WORK_INITIALIZER(nonblocking_pool.push_work, + push_to_pool), }; static __u32 const twist_table[8] = { @@ -498,7 +501,7 @@ static void _mix_pool_bytes(struct entropy_store *r, const void *in, /* mix one byte at a time to simplify size handling and churn faster */ while (nbytes--) { - w = rol32(*bytes++, input_rotate & 31); + w = rol32(*bytes++, input_rotate); i = (i - 1) & wordmask; /* XOR in the various taps */ @@ -518,7 +521,7 @@ static void _mix_pool_bytes(struct entropy_store *r, const void *in, * rotation, so that successive passes spread the * input bits across the pool evenly. */ - input_rotate += i ? 7 : 14; + input_rotate = (input_rotate + (i ? 7 : 14)) & 31; } ACCESS_ONCE(r->input_rotate) = input_rotate; @@ -561,62 +564,151 @@ struct fast_pool { * 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) +static void fast_mix(struct fast_pool *f, __u32 input[4]) { - 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; + w = rol32(input[0], input_rotate) ^ f->pool[0] ^ f->pool[3]; + f->pool[0] = (w >> 3) ^ twist_table[w & 7]; + input_rotate = (input_rotate + 14) & 31; + w = rol32(input[1], input_rotate) ^ f->pool[1] ^ f->pool[0]; + f->pool[1] = (w >> 3) ^ twist_table[w & 7]; + input_rotate = (input_rotate + 7) & 31; + w = rol32(input[2], input_rotate) ^ f->pool[2] ^ f->pool[1]; + f->pool[2] = (w >> 3) ^ twist_table[w & 7]; + input_rotate = (input_rotate + 7) & 31; + w = rol32(input[3], input_rotate) ^ f->pool[3] ^ f->pool[2]; + f->pool[3] = (w >> 3) ^ twist_table[w & 7]; + input_rotate = (input_rotate + 7) & 31; + f->rotate = input_rotate; + f->count++; } /* - * Credit (or debit) the entropy store with n bits of entropy + * Credit (or debit) the entropy store with n bits of entropy. + * Use credit_entropy_bits_safe() if the value comes from userspace + * or otherwise should be checked for extreme values. */ static void credit_entropy_bits(struct entropy_store *r, int nbits) { int entropy_count, orig; + const int pool_size = r->poolinfo->poolfracbits; + int nfrac = nbits << ENTROPY_SHIFT; if (!nbits) return; - DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name); retry: entropy_count = orig = ACCESS_ONCE(r->entropy_count); - entropy_count += nbits; + if (nfrac < 0) { + /* Debit */ + entropy_count += nfrac; + } else { + /* + * Credit: we have to account for the possibility of + * overwriting already present entropy. Even in the + * ideal case of pure Shannon entropy, new contributions + * approach the full value asymptotically: + * + * entropy <- entropy + (pool_size - entropy) * + * (1 - exp(-add_entropy/pool_size)) + * + * For add_entropy <= pool_size/2 then + * (1 - exp(-add_entropy/pool_size)) >= + * (add_entropy/pool_size)*0.7869... + * so we can approximate the exponential with + * 3/4*add_entropy/pool_size and still be on the + * safe side by adding at most pool_size/2 at a time. + * + * The use of pool_size-2 in the while statement is to + * prevent rounding artifacts from making the loop + * arbitrarily long; this limits the loop to log2(pool_size)*2 + * turns no matter how large nbits is. + */ + int pnfrac = nfrac; + const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2; + /* The +2 corresponds to the /4 in the denominator */ + + do { + unsigned int anfrac = min(pnfrac, pool_size/2); + unsigned int add = + ((pool_size - entropy_count)*anfrac*3) >> s; + + entropy_count += add; + pnfrac -= anfrac; + } while (unlikely(entropy_count < pool_size-2 && pnfrac)); + } if (entropy_count < 0) { - DEBUG_ENT("negative entropy/overflow\n"); + pr_warn("random: negative entropy/overflow: pool %s count %d\n", + r->name, entropy_count); + WARN_ON(1); entropy_count = 0; - } else if (entropy_count > r->poolinfo->POOLBITS) - entropy_count = r->poolinfo->POOLBITS; + } else if (entropy_count > pool_size) + entropy_count = pool_size; 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; + r->entropy_total += nbits; + if (!r->initialized && r->entropy_total > 128) { + r->initialized = 1; + r->entropy_total = 0; + if (r == &nonblocking_pool) { + prandom_reseed_late(); + pr_notice("random: %s pool is initialized\n", r->name); + } } - trace_credit_entropy_bits(r->name, nbits, entropy_count, + trace_credit_entropy_bits(r->name, nbits, + entropy_count >> ENTROPY_SHIFT, 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); + if (r == &input_pool) { + int entropy_bytes = entropy_count >> ENTROPY_SHIFT; + + /* should we wake readers? */ + if (entropy_bytes >= random_read_wakeup_thresh) { + wake_up_interruptible(&random_read_wait); + kill_fasync(&fasync, SIGIO, POLL_IN); + } + /* If the input pool is getting full, send some + * entropy to the two output pools, flipping back and + * forth between them, until the output pools are 75% + * full. + */ + if (entropy_bytes > random_write_wakeup_thresh && + r->initialized && + r->entropy_total >= 2*random_read_wakeup_thresh) { + static struct entropy_store *last = &blocking_pool; + struct entropy_store *other = &blocking_pool; + + if (last == &blocking_pool) + other = &nonblocking_pool; + if (other->entropy_count <= + 3 * other->poolinfo->poolfracbits / 4) + last = other; + if (last->entropy_count <= + 3 * last->poolinfo->poolfracbits / 4) { + schedule_work(&last->push_work); + r->entropy_total = 0; + } + } } } +static void credit_entropy_bits_safe(struct entropy_store *r, int nbits) +{ + const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1)); + + /* Cap the value to avoid overflows */ + nbits = min(nbits, nbits_max); + nbits = max(nbits, -nbits_max); + + credit_entropy_bits(r, nbits); +} + /********************************************************************* * * Entropy input management @@ -630,6 +722,8 @@ struct timer_rand_state { unsigned dont_count_entropy:1; }; +#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, }; + /* * Add device- or boot-specific data to the input and nonblocking * pools to help initialize them to unique values. @@ -640,16 +734,23 @@ struct timer_rand_state { */ void add_device_randomness(const void *buf, unsigned int size) { - unsigned long time = get_cycles() ^ jiffies; + unsigned long time = random_get_entropy() ^ jiffies; + unsigned long flags; - 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); + trace_add_device_randomness(size, _RET_IP_); + spin_lock_irqsave(&input_pool.lock, flags); + _mix_pool_bytes(&input_pool, buf, size, NULL); + _mix_pool_bytes(&input_pool, &time, sizeof(time), NULL); + spin_unlock_irqrestore(&input_pool.lock, flags); + + spin_lock_irqsave(&nonblocking_pool.lock, flags); + _mix_pool_bytes(&nonblocking_pool, buf, size, NULL); + _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL); + spin_unlock_irqrestore(&nonblocking_pool.lock, flags); } EXPORT_SYMBOL(add_device_randomness); -static struct timer_rand_state input_timer_state; +static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE; /* * This function adds entropy to the entropy "pool" by using timing @@ -663,6 +764,7 @@ static struct timer_rand_state input_timer_state; */ static void add_timer_randomness(struct timer_rand_state *state, unsigned num) { + struct entropy_store *r; struct { long jiffies; unsigned cycles; @@ -671,15 +773,12 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num) long delta, delta2, delta3; preempt_disable(); - /* if over the trickle threshold, use only 1 in 4096 samples */ - if (input_pool.entropy_count > trickle_thresh && - ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff)) - goto out; sample.jiffies = jiffies; - sample.cycles = get_cycles(); + sample.cycles = random_get_entropy(); sample.num = num; - mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL); + r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool; + mix_pool_bytes(r, &sample, sizeof(sample), NULL); /* * Calculate number of bits of randomness we probably added. @@ -713,10 +812,8 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num) * 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)); + credit_entropy_bits(r, min_t(int, fls(delta>>1), 11)); } -out: preempt_enable(); } @@ -729,10 +826,10 @@ void add_input_randomness(unsigned int type, unsigned int code, 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); + trace_add_input_randomness(ENTROPY_BITS(&input_pool)); } EXPORT_SYMBOL_GPL(add_input_randomness); @@ -744,20 +841,21 @@ void add_interrupt_randomness(int irq, int irq_flags) 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; - } + cycles_t cycles = random_get_entropy(); + __u32 input[4], c_high, j_high; + __u64 ip; - fast_mix(fast_pool, input, sizeof(input)); + c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0; + j_high = (sizeof(now) > 4) ? now >> 32 : 0; + input[0] = cycles ^ j_high ^ irq; + input[1] = now ^ c_high; + ip = regs ? instruction_pointer(regs) : _RET_IP_; + input[2] = ip; + input[3] = ip >> 32; - if ((fast_pool->count & 1023) && - !time_after(now, fast_pool->last + HZ)) + fast_mix(fast_pool, input); + + if ((fast_pool->count & 63) && !time_after(now, fast_pool->last + HZ)) return; fast_pool->last = now; @@ -786,10 +884,8 @@ 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)); + trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool)); } #endif @@ -807,30 +903,58 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf, * from the primary pool to the secondary extraction pool. We make * sure we pull enough for a 'catastrophic reseed'. */ +static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes); static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes) { - __u32 tmp[OUTPUT_POOL_WORDS]; + if (r->limit == 0 && random_min_urandom_seed) { + unsigned long now = jiffies; - 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 " - "(%zu 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, NULL); - credit_entropy_bits(r, bytes*8); + if (time_before(now, + r->last_pulled + random_min_urandom_seed * HZ)) + return; + r->last_pulled = now; } + if (r->pull && + r->entropy_count < (nbytes << (ENTROPY_SHIFT + 3)) && + r->entropy_count < r->poolinfo->poolfracbits) + _xfer_secondary_pool(r, nbytes); +} + +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; + 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)); + + 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); + mix_pool_bytes(r, tmp, bytes, NULL); + credit_entropy_bits(r, bytes*8); +} + +/* + * Used as a workqueue function so that when the input pool is getting + * full, we can "spill over" some entropy to the output pools. That + * way the output pools can store some of the excess entropy instead + * of letting it go to waste. + */ +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); + trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT, + r->pull->entropy_count >> ENTROPY_SHIFT); } /* @@ -850,50 +974,48 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min, { 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->POOLBITS); - DEBUG_ENT("trying to extract %zu bits from %s\n", - nbytes * 8, r->name); + BUG_ON(r->entropy_count > r->poolinfo->poolfracbits); /* Can we pull enough? */ - if (r->entropy_count / 8 < min + reserved) { - nbytes = 0; - } else { - int entropy_count, orig; retry: - entropy_count = orig = ACCESS_ONCE(r->entropy_count); + entropy_count = orig = ACCESS_ONCE(r->entropy_count); + have_bytes = entropy_count >> (ENTROPY_SHIFT + 3); + ibytes = nbytes; + if (have_bytes < min + reserved) { + ibytes = 0; + } else { /* If limited, never pull more than available */ - if (r->limit && nbytes + reserved >= entropy_count / 8) - nbytes = entropy_count/8 - reserved; - - if (entropy_count / 8 >= nbytes + reserved) { - entropy_count -= nbytes*8; - if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) - goto retry; - } else { - entropy_count = reserved; - if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) - goto retry; - } + if (r->limit && ibytes + reserved >= have_bytes) + ibytes = have_bytes - reserved; - if (entropy_count < random_write_wakeup_thresh) - wakeup_write = 1; - } + if (have_bytes >= ibytes + reserved) + entropy_count -= ibytes << (ENTROPY_SHIFT + 3); + else + entropy_count = reserved << (ENTROPY_SHIFT + 3); - DEBUG_ENT("debiting %zu entropy credits from %s%s\n", - nbytes * 8, r->name, r->limit ? "" : " (unlimited)"); + 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); + trace_debit_entropy(r->name, 8 * ibytes); if (wakeup_write) { wake_up_interruptible(&random_write_wait); kill_fasync(&fasync, SIGIO, POLL_OUT); } - return nbytes; + return ibytes; } static void extract_buf(struct entropy_store *r, __u8 *out) @@ -901,7 +1023,7 @@ static void extract_buf(struct entropy_store *r, __u8 *out) int i; union { __u32 w[5]; - unsigned long l[LONGS(EXTRACT_SIZE)]; + unsigned long l[LONGS(20)]; } hash; __u32 workspace[SHA_WORKSPACE_WORDS]; __u8 extract[64]; @@ -914,6 +1036,17 @@ static void extract_buf(struct entropy_store *r, __u8 *out) sha_transform(hash.w, (__u8 *)(r->pool + i), workspace); /* + * If we have a architectural hardware random number + * generator, mix that in, too. + */ + for (i = 0; i < LONGS(20); i++) { + unsigned long v; + if (!arch_get_random_long(&v)) + break; + hash.l[i] ^= v; + } + + /* * 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 @@ -942,17 +1075,6 @@ static void extract_buf(struct entropy_store *r, __u8 *out) 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)); } @@ -968,10 +1090,10 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf, if (fips_enabled) { spin_lock_irqsave(&r->lock, flags); if (!r->last_data_init) { - r->last_data_init = true; + r->last_data_init = 1; spin_unlock_irqrestore(&r->lock, flags); trace_extract_entropy(r->name, EXTRACT_SIZE, - r->entropy_count, _RET_IP_); + ENTROPY_BITS(r), _RET_IP_); xfer_secondary_pool(r, EXTRACT_SIZE); extract_buf(r, tmp); spin_lock_irqsave(&r->lock, flags); @@ -980,7 +1102,7 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf, spin_unlock_irqrestore(&r->lock, flags); } - trace_extract_entropy(r->name, nbytes, r->entropy_count, _RET_IP_); + trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_); xfer_secondary_pool(r, nbytes); nbytes = account(r, nbytes, min, reserved); @@ -1013,7 +1135,7 @@ 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_); + trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_); xfer_secondary_pool(r, nbytes); nbytes = account(r, nbytes, 0, 0); @@ -1053,6 +1175,14 @@ static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf, */ void get_random_bytes(void *buf, int nbytes) { +#if DEBUG_RANDOM_BOOT > 0 + if (unlikely(nonblocking_pool.initialized == 0)) + printk(KERN_NOTICE "random: %pF get_random_bytes called " + "with %d bits of entropy available\n", + (void *) _RET_IP_, + nonblocking_pool.entropy_total); +#endif + trace_get_random_bytes(nbytes, _RET_IP_); extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0); } EXPORT_SYMBOL(get_random_bytes); @@ -1071,7 +1201,7 @@ void get_random_bytes_arch(void *buf, int nbytes) { char *p = buf; - trace_get_random_bytes(nbytes, _RET_IP_); + trace_get_random_bytes_arch(nbytes, _RET_IP_); while (nbytes) { unsigned long v; int chunk = min(nbytes, (int)sizeof(unsigned long)); @@ -1105,13 +1235,11 @@ static void init_std_data(struct entropy_store *r) ktime_t now = ktime_get_real(); unsigned long rv; - r->entropy_count = 0; - r->entropy_total = 0; - r->last_data_init = false; + r->last_pulled = jiffies; mix_pool_bytes(r, &now, sizeof(now), NULL); - for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof(rv)) { + for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) { if (!arch_get_random_long(&rv)) - break; + rv = random_get_entropy(); mix_pool_bytes(r, &rv, sizeof(rv), NULL); } mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL); @@ -1134,7 +1262,7 @@ static int rand_initialize(void) init_std_data(&nonblocking_pool); return 0; } -module_init(rand_initialize); +early_initcall(rand_initialize); #ifdef CONFIG_BLOCK void rand_initialize_disk(struct gendisk *disk) @@ -1146,8 +1274,10 @@ void rand_initialize_disk(struct gendisk *disk) * source. */ state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL); - if (state) + if (state) { + state->last_time = INITIAL_JIFFIES; disk->random = state; + } } #endif @@ -1164,8 +1294,6 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) if (n > SEC_XFER_SIZE) n = SEC_XFER_SIZE; - DEBUG_ENT("reading %zu bits\n", n*8); - n = extract_entropy_user(&blocking_pool, buf, n); if (n < 0) { @@ -1173,8 +1301,9 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) break; } - DEBUG_ENT("read got %zd bits (%zd still needed)\n", - n*8, (nbytes-n)*8); + trace_random_read(n*8, (nbytes-n)*8, + ENTROPY_BITS(&blocking_pool), + ENTROPY_BITS(&input_pool)); if (n == 0) { if (file->f_flags & O_NONBLOCK) { @@ -1182,13 +1311,9 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) break; } - DEBUG_ENT("sleeping?\n"); - wait_event_interruptible(random_read_wait, - input_pool.entropy_count >= - random_read_wakeup_thresh); - - DEBUG_ENT("awake\n"); + ENTROPY_BITS(&input_pool) >= + random_read_wakeup_thresh); if (signal_pending(current)) { retval = -ERESTARTSYS; @@ -1211,7 +1336,18 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) static ssize_t urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) { - return extract_entropy_user(&nonblocking_pool, buf, nbytes); + int ret; + + if (unlikely(nonblocking_pool.initialized == 0)) + printk_once(KERN_NOTICE "random: %s urandom read " + "with %d bits of entropy available\n", + current->comm, nonblocking_pool.entropy_total); + + ret = extract_entropy_user(&nonblocking_pool, buf, nbytes); + + trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool), + ENTROPY_BITS(&input_pool)); + return ret; } static unsigned int @@ -1222,9 +1358,9 @@ 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 (input_pool.entropy_count >= random_read_wakeup_thresh) + if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_thresh) mask |= POLLIN | POLLRDNORM; - if (input_pool.entropy_count < random_write_wakeup_thresh) + if (ENTROPY_BITS(&input_pool) < random_write_wakeup_thresh) mask |= POLLOUT | POLLWRNORM; return mask; } @@ -1275,7 +1411,8 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) switch (cmd) { case RNDGETENTCNT: /* inherently racy, no point locking */ - if (put_user(input_pool.entropy_count, p)) + ent_count = ENTROPY_BITS(&input_pool); + if (put_user(ent_count, p)) return -EFAULT; return 0; case RNDADDTOENTCNT: @@ -1283,7 +1420,7 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) return -EPERM; if (get_user(ent_count, p)) return -EFAULT; - credit_entropy_bits(&input_pool, ent_count); + credit_entropy_bits_safe(&input_pool, ent_count); return 0; case RNDADDENTROPY: if (!capable(CAP_SYS_ADMIN)) @@ -1298,14 +1435,19 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) size); if (retval < 0) return retval; - credit_entropy_bits(&input_pool, ent_count); + credit_entropy_bits_safe(&input_pool, ent_count); return 0; case RNDZAPENTCNT: case RNDCLEARPOOL: - /* Clear the entropy pool counters. */ + /* + * Clear the entropy pool counters. We no longer clear + * the entropy pool, as that's silly. + */ if (!capable(CAP_SYS_ADMIN)) return -EPERM; - rand_initialize(); + input_pool.entropy_count = 0; + nonblocking_pool.entropy_count = 0; + blocking_pool.entropy_count = 0; return 0; default: return -EINVAL; @@ -1405,6 +1547,23 @@ static int proc_do_uuid(struct ctl_table *table, int write, return proc_dostring(&fake_table, write, buffer, lenp, ppos); } +/* + * Return entropy available scaled to integral bits + */ +static int proc_do_entropy(ctl_table *table, int write, + void __user *buffer, size_t *lenp, loff_t *ppos) +{ + ctl_table fake_table; + int entropy_count; + + entropy_count = *(int *)table->data >> ENTROPY_SHIFT; + + fake_table.data = &entropy_count; + fake_table.maxlen = sizeof(entropy_count); + + return proc_dointvec(&fake_table, write, buffer, lenp, ppos); +} + static int sysctl_poolsize = INPUT_POOL_WORDS * 32; extern struct ctl_table random_table[]; struct ctl_table random_table[] = { @@ -1419,7 +1578,7 @@ struct ctl_table random_table[] = { .procname = "entropy_avail", .maxlen = sizeof(int), .mode = 0444, - .proc_handler = proc_dointvec, + .proc_handler = proc_do_entropy, .data = &input_pool.entropy_count, }, { @@ -1441,6 +1600,13 @@ struct ctl_table random_table[] = { .extra2 = &max_write_thresh, }, { + .procname = "urandom_min_reseed_secs", + .data = &random_min_urandom_seed, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec, + }, + { .procname = "boot_id", .data = &sysctl_bootid, .maxlen = 16, @@ -1459,12 +1625,11 @@ struct ctl_table random_table[] = { static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned; -static int __init random_int_secret_init(void) +int random_int_secret_init(void) { get_random_bytes(random_int_secret, sizeof(random_int_secret)); return 0; } -late_initcall(random_int_secret_init); /* * Get a random word for internal kernel use only. Similar to urandom but @@ -1483,7 +1648,7 @@ unsigned int get_random_int(void) hash = get_cpu_var(get_random_int_hash); - hash[0] += current->pid + jiffies + get_cycles(); + hash[0] += current->pid + jiffies + random_get_entropy(); md5_transform(hash, random_int_secret); ret = hash[0]; put_cpu_var(get_random_int_hash); |