diff options
Diffstat (limited to 'drivers/char/random.c')
| -rw-r--r-- | drivers/char/random.c | 1447 |
1 files changed, 754 insertions, 693 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 5a1aa64f4e7..71529e196b8 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -125,20 +125,32 @@ * 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. Disk interrupts are - * a better measure, since the timing of the disk 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 + * entropy pool. Note that high-speed solid state drives with very low + * seek times do not make for good sources of entropy, as their seek + * times are usually fairly consistent. * * All of these routines try to estimate how many bits of randomness a * particular randomness source. They do this by keeping track of the @@ -241,137 +253,149 @@ #include <linux/percpu.h> #include <linux/cryptohash.h> #include <linux/fips.h> - -#ifdef CONFIG_GENERIC_HARDIRQS -# include <linux/irq.h> -#endif +#include <linux/ptrace.h> +#include <linux/kmemcheck.h> +#include <linux/workqueue.h> +#include <linux/irq.h> #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 */ -#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. */ -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 = 128; +static int random_write_wakeup_bits = 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 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 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 Modeling 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 */ @@ -379,21 +403,6 @@ static DECLARE_WAIT_QUEUE_HEAD(random_read_wait); static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); static struct fasync_struct *fasync; -#if 0 -static int 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) -#else -#define DEBUG_ENT(fmt, arg...) do {} while (0) -#endif - /********************************************************************** * * OS independent entropy store. Here are the functions which handle @@ -404,20 +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 short add_ptr; + unsigned short input_rotate; int entropy_count; - int input_rotate; + int entropy_total; + unsigned int initialized:1; + 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]; @@ -426,7 +441,7 @@ static struct entropy_store input_pool = { .poolinfo = &poolinfo_table[0], .name = "input", .limit = 1, - .lock = __SPIN_LOCK_UNLOCKED(&input_pool.lock), + .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), .pool = input_pool_data }; @@ -435,18 +450,26 @@ static struct entropy_store blocking_pool = { .name = "blocking", .limit = 1, .pull = &input_pool, - .lock = __SPIN_LOCK_UNLOCKED(&blocking_pool.lock), - .pool = blocking_pool_data + .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock), + .pool = blocking_pool_data, + .push_work = __WORK_INITIALIZER(blocking_pool.push_work, + push_to_pool), }; static struct entropy_store nonblocking_pool = { .poolinfo = &poolinfo_table[1], .name = "nonblocking", .pull = &input_pool, - .lock = __SPIN_LOCK_UNLOCKED(&nonblocking_pool.lock), - .pool = nonblocking_pool_data + .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock), + .pool = nonblocking_pool_data, + .push_work = __WORK_INITIALIZER(nonblocking_pool.push_work, + push_to_pool), }; +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 @@ -457,33 +480,28 @@ 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--) { - w = rol32(*bytes++, input_rotate & 31); + w = rol32(*bytes++, input_rotate); i = (i - 1) & wordmask; /* XOR in the various taps */ @@ -503,53 +521,192 @@ static void mix_pool_bytes_extract(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; } - 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, __u32 input[4]) { - mix_pool_bytes_extract(r, in, bytes, NULL); + __u32 w; + unsigned input_rotate = f->rotate; + + 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) { - unsigned long flags; - int entropy_count; + int entropy_count, orig; + const int pool_size = r->poolinfo->poolfracbits; + int nfrac = nbits << ENTROPY_SHIFT; if (!nbits) return; - spin_lock_irqsave(&r->lock, flags); +retry: + entropy_count = orig = ACCESS_ONCE(r->entropy_count); + 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)); + } - 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"); + if (unlikely(entropy_count < 0)) { + 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; - 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); + } else if (entropy_count > pool_size) + entropy_count = pool_size; + if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) + goto retry; + + 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 >> ENTROPY_SHIFT, + r->entropy_total, _RET_IP_); + + if (r == &input_pool) { + int entropy_bits = entropy_count >> ENTROPY_SHIFT; + + /* should we wake readers? */ + if (entropy_bits >= random_read_wakeup_bits) { + 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_bits > random_write_wakeup_bits && + r->initialized && + r->entropy_total >= 2*random_read_wakeup_bits) { + 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; + } + } } - spin_unlock_irqrestore(&r->lock, flags); +} + +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); } /********************************************************************* @@ -565,44 +722,35 @@ 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; -} +#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, }; -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 = random_get_entropy() ^ jiffies; + unsigned long flags; - desc = irq_to_desc(irq); + 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); - desc->timer_rand_state = state; + 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); } -#endif +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 @@ -616,23 +764,21 @@ 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 { - cycles_t cycles; long jiffies; + unsigned cycles; 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.cycles = random_get_entropy(); sample.num = num; - mix_pool_bytes(&input_pool, &sample, sizeof(sample)); + 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. @@ -666,10 +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(); } @@ -682,24 +826,71 @@ 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); -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; + 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; + 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; + + fast_mix(fast_pool, input); + + if ((fast_pool->count & 63) && !time_after(now, fast_pool->last + HZ)) + return; - state = get_timer_rand_state(irq); + fast_pool->last = now; - if (state == NULL) - return; + 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, otherwise credit 1 bit. + */ + credit = 1; + if (cycles == 0) { + if (irq_flags & __IRQF_TIMER) { + if (fast_pool->last_timer_intr) + credit = 0; + fast_pool->last_timer_intr = 1; + } else + fast_pool->last_timer_intr = 0; + } + + /* + * 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; + } - DEBUG_ENT("irq event %d\n", irq); - add_timer_randomness(state, 0x100 + irq); + credit_entropy_bits(r, credit); } #ifdef CONFIG_BLOCK @@ -708,11 +899,10 @@ 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)); } +EXPORT_SYMBOL_GPL(add_disk_randomness); #endif /********************************************************************* @@ -725,97 +915,149 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf, size_t nbytes, int min, int rsvd); /* - * This utility inline function is responsible for transfering entropy + * This utility inline function is responsible for transferring entropy * 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->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); + 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; } + 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 wakeups' worth */ + int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4; + int bytes = nbytes; + + /* 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_bits / 8, rsvd_bytes); + mix_pool_bytes(r, tmp, bytes, NULL); + credit_entropy_bits(r, bytes*8); } /* - * 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. + * 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_bits/8); + trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT, + r->pull->entropy_count >> ENTROPY_SHIFT); +} +/* + * 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; - - /* Hold lock while accounting */ - spin_lock_irqsave(&r->lock, flags); + int entropy_count, orig; + size_t ibytes, nfrac; - BUG_ON(r->entropy_count > r->poolinfo->POOLBITS); - DEBUG_ENT("trying to extract %d 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 { - /* 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); - } +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); + + if ((have_bytes -= reserved) < 0) + have_bytes = 0; + ibytes = min_t(size_t, ibytes, have_bytes); } + if (ibytes < min) + ibytes = 0; - DEBUG_ENT("debiting %d entropy credits from %s%s\n", - nbytes * 8, r->name, r->limit ? "" : " (unlimited)"); + if (unlikely(entropy_count < 0)) { + pr_warn("random: negative entropy count: pool %s count %d\n", + r->name, entropy_count); + WARN_ON(1); + entropy_count = 0; + } + nfrac = ibytes << (ENTROPY_SHIFT + 3); + if ((size_t) entropy_count > nfrac) + entropy_count -= nfrac; + else + entropy_count = 0; - spin_unlock_irqrestore(&r->lock, flags); + if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) + goto retry; + + trace_debit_entropy(r->name, 8 * ibytes); + if (ibytes && + (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) { + wake_up_interruptible(&random_write_wait); + kill_fasync(&fasync, SIGIO, POLL_OUT); + } - return nbytes; + 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; - __u32 hash[5], workspace[SHA_WORKSPACE_WORDS]; + union { + __u32 w[5]; + unsigned long l[LONGS(20)]; + } hash; + __u32 workspace[SHA_WORKSPACE_WORDS]; __u8 extract[64]; + unsigned long flags; + + /* + * 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; + } /* Generate a hash across the pool, 16 words (512 bits) at a time */ - sha_init(hash); + 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 @@ -826,13 +1068,14 @@ 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)); @@ -841,20 +1084,47 @@ 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); + + memcpy(out, &hash, EXTRACT_SIZE); + 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) + size_t nbytes, int min, int reserved) { ssize_t ret = 0, i; __u8 tmp[EXTRACT_SIZE]; unsigned long flags; + /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */ + if (fips_enabled) { + spin_lock_irqsave(&r->lock, flags); + if (!r->last_data_init) { + r->last_data_init = 1; + spin_unlock_irqrestore(&r->lock, flags); + trace_extract_entropy(r->name, EXTRACT_SIZE, + ENTROPY_BITS(r), _RET_IP_); + xfer_secondary_pool(r, EXTRACT_SIZE); + extract_buf(r, tmp); + spin_lock_irqsave(&r->lock, flags); + memcpy(r->last_data, tmp, EXTRACT_SIZE); + } + spin_unlock_irqrestore(&r->lock, flags); + } + + trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_); xfer_secondary_pool(r, nbytes); nbytes = account(r, nbytes, min, reserved); @@ -881,12 +1151,17 @@ 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) { ssize_t ret = 0, i; __u8 tmp[EXTRACT_SIZE]; + trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_); xfer_secondary_pool(r, nbytes); nbytes = account(r, nbytes, 0, 0); @@ -920,16 +1195,59 @@ 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 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) { +#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); /* + * 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_arch(nbytes, _RET_IP_); + while (nbytes) { + unsigned long v; + int chunk = min(nbytes, (int)sizeof(unsigned long)); + + if (!arch_get_random_long(&v)) + break; + + memcpy(p, &v, chunk); + p += chunk; + nbytes -= chunk; + } + + if (nbytes) + extract_entropy(&nonblocking_pool, p, nbytes, 0, 0); +} +EXPORT_SYMBOL(get_random_bytes_arch); + + +/* * init_std_data - initialize pool with system data * * @r: pool to initialize @@ -940,18 +1258,31 @@ EXPORT_SYMBOL(get_random_bytes); */ 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()))); + int i; + ktime_t now = ktime_get_real(); + unsigned long rv; + + 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_seed_long(&rv) && + !arch_get_random_long(&rv)) + rv = random_get_entropy(); + mix_pool_bytes(r, &rv, sizeof(rv), NULL); + } + 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); @@ -959,25 +1290,7 @@ static int rand_initialize(void) init_std_data(&nonblocking_pool); return 0; } -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); -} +early_initcall(rand_initialize); #ifdef CONFIG_BLOCK void rand_initialize_disk(struct gendisk *disk) @@ -989,71 +1302,96 @@ 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 -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; - - 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); + for (i = 0; i < nlongs; i++) { + if (arch_get_random_seed_long(&buf[n])) + n++; + } - if (n == 0) { - if (file->f_flags & O_NONBLOCK) { - retval = -EAGAIN; - break; - } + if (n) { + unsigned int rand_bytes = n * sizeof(unsigned long); - DEBUG_ENT("sleeping?\n"); + mix_pool_bytes(&input_pool, buf, rand_bytes, NULL); + credit_entropy_bits(&input_pool, rand_bytes*4); + } - wait_event_interruptible(random_read_wait, - input_pool.entropy_count >= - random_read_wakeup_thresh); + return n; +} - DEBUG_ENT("awake\n"); +static ssize_t +random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) +{ + ssize_t n; - if (signal_pending(current)) { - retval = -ERESTARTSYS; - break; - } + 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; + + /* Pool is (near) empty. Maybe wait and retry. */ + + /* First try an emergency refill */ + if (arch_random_refill()) 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 (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 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); + + nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3)); + 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 @@ -1064,9 +1402,9 @@ 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_bits) mask |= POLLIN | POLLRDNORM; - if (input_pool.entropy_count < random_write_wakeup_thresh) + if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits) mask |= POLLOUT | POLLWRNORM; return mask; } @@ -1086,7 +1424,7 @@ 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(); } @@ -1117,7 +1455,8 @@ 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: @@ -1125,7 +1464,7 @@ 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)) @@ -1140,14 +1479,19 @@ 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; @@ -1207,32 +1551,37 @@ 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(ctl_table *table, int write, +static int proc_do_uuid(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { - ctl_table fake_table; + struct 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); + } else { + static DEFINE_SPINLOCK(bootid_spinlock); + + spin_lock(&bootid_spinlock); + if (!uuid[8]) + generate_random_uuid(uuid); + spin_unlock(&bootid_spinlock); + } sprintf(buf, "%pU", uuid); @@ -1242,8 +1591,26 @@ static int proc_do_uuid(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(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, loff_t *ppos) +{ + struct 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; -ctl_table random_table[] = { +extern struct ctl_table random_table[]; +struct ctl_table random_table[] = { { .procname = "poolsize", .data = &sysctl_poolsize, @@ -1255,12 +1622,12 @@ 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, }, { .procname = "read_wakeup_threshold", - .data = &random_read_wakeup_thresh, + .data = &random_read_wakeup_bits, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_minmax, @@ -1269,7 +1636,7 @@ 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, @@ -1277,6 +1644,13 @@ 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, @@ -1293,330 +1667,13 @@ ctl_table random_table[] = { }; #endif /* CONFIG_SYSCTL */ -/******************************************************************** - * - * Random functions for networking - * - ********************************************************************/ - -/* - * TCP initial sequence number picking. This uses the random number - * generator to pick an initial secret value. This value is hashed - * along with the TCP endpoint information to provide a unique - * starting point for each pair of TCP endpoints. This defeats - * attacks which rely on guessing the initial TCP sequence number. - * This algorithm was suggested by Steve Bellovin. - * - * Using a very strong hash was taking an appreciable amount of the total - * TCP connection establishment time, so this is a weaker hash, - * compensated for by changing the secret periodically. - */ - -/* F, G and H are basic MD4 functions: selection, majority, parity */ -#define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z)))) -#define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z))) -#define H(x, y, z) ((x) ^ (y) ^ (z)) - -/* - * The generic round function. The application is so specific that - * we don't bother protecting all the arguments with parens, as is generally - * good macro practice, in favor of extra legibility. - * Rotation is separate from addition to prevent recomputation - */ -#define ROUND(f, a, b, c, d, x, s) \ - (a += f(b, c, d) + x, a = (a << s) | (a >> (32 - s))) -#define K1 0 -#define K2 013240474631UL -#define K3 015666365641UL - -#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) +static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned; -static __u32 twothirdsMD4Transform(__u32 const buf[4], __u32 const in[12]) +int random_int_secret_init(void) { - __u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3]; - - /* Round 1 */ - ROUND(F, a, b, c, d, in[ 0] + K1, 3); - ROUND(F, d, a, b, c, in[ 1] + K1, 7); - ROUND(F, c, d, a, b, in[ 2] + K1, 11); - ROUND(F, b, c, d, a, in[ 3] + K1, 19); - ROUND(F, a, b, c, d, in[ 4] + K1, 3); - ROUND(F, d, a, b, c, in[ 5] + K1, 7); - ROUND(F, c, d, a, b, in[ 6] + K1, 11); - ROUND(F, b, c, d, a, in[ 7] + K1, 19); - ROUND(F, a, b, c, d, in[ 8] + K1, 3); - ROUND(F, d, a, b, c, in[ 9] + K1, 7); - ROUND(F, c, d, a, b, in[10] + K1, 11); - ROUND(F, b, c, d, a, in[11] + K1, 19); - - /* Round 2 */ - ROUND(G, a, b, c, d, in[ 1] + K2, 3); - ROUND(G, d, a, b, c, in[ 3] + K2, 5); - ROUND(G, c, d, a, b, in[ 5] + K2, 9); - ROUND(G, b, c, d, a, in[ 7] + K2, 13); - ROUND(G, a, b, c, d, in[ 9] + K2, 3); - ROUND(G, d, a, b, c, in[11] + K2, 5); - ROUND(G, c, d, a, b, in[ 0] + K2, 9); - ROUND(G, b, c, d, a, in[ 2] + K2, 13); - ROUND(G, a, b, c, d, in[ 4] + K2, 3); - ROUND(G, d, a, b, c, in[ 6] + K2, 5); - ROUND(G, c, d, a, b, in[ 8] + K2, 9); - ROUND(G, b, c, d, a, in[10] + K2, 13); - - /* Round 3 */ - ROUND(H, a, b, c, d, in[ 3] + K3, 3); - ROUND(H, d, a, b, c, in[ 7] + K3, 9); - ROUND(H, c, d, a, b, in[11] + K3, 11); - ROUND(H, b, c, d, a, in[ 2] + K3, 15); - ROUND(H, a, b, c, d, in[ 6] + K3, 3); - ROUND(H, d, a, b, c, in[10] + K3, 9); - ROUND(H, c, d, a, b, in[ 1] + K3, 11); - ROUND(H, b, c, d, a, in[ 5] + K3, 15); - ROUND(H, a, b, c, d, in[ 9] + K3, 3); - ROUND(H, d, a, b, c, in[ 0] + K3, 9); - ROUND(H, c, d, a, b, in[ 4] + K3, 11); - ROUND(H, b, c, d, a, in[ 8] + K3, 15); - - return buf[1] + b; /* "most hashed" word */ - /* Alternative: return sum of all words? */ -} -#endif - -#undef ROUND -#undef F -#undef G -#undef H -#undef K1 -#undef K2 -#undef K3 - -/* This should not be decreased so low that ISNs wrap too fast. */ -#define REKEY_INTERVAL (300 * HZ) -/* - * Bit layout of the tcp sequence numbers (before adding current time): - * bit 24-31: increased after every key exchange - * bit 0-23: hash(source,dest) - * - * The implementation is similar to the algorithm described - * in the Appendix of RFC 1185, except that - * - it uses a 1 MHz clock instead of a 250 kHz clock - * - it performs a rekey every 5 minutes, which is equivalent - * to a (source,dest) tulple dependent forward jump of the - * clock by 0..2^(HASH_BITS+1) - * - * Thus the average ISN wraparound time is 68 minutes instead of - * 4.55 hours. - * - * SMP cleanup and lock avoidance with poor man's RCU. - * Manfred Spraul <manfred@colorfullife.com> - * - */ -#define COUNT_BITS 8 -#define COUNT_MASK ((1 << COUNT_BITS) - 1) -#define HASH_BITS 24 -#define HASH_MASK ((1 << HASH_BITS) - 1) - -static struct keydata { - __u32 count; /* already shifted to the final position */ - __u32 secret[12]; -} ____cacheline_aligned ip_keydata[2]; - -static unsigned int ip_cnt; - -static void rekey_seq_generator(struct work_struct *work); - -static DECLARE_DELAYED_WORK(rekey_work, rekey_seq_generator); - -/* - * Lock avoidance: - * The ISN generation runs lockless - it's just a hash over random data. - * State changes happen every 5 minutes when the random key is replaced. - * Synchronization is performed by having two copies of the hash function - * state and rekey_seq_generator always updates the inactive copy. - * The copy is then activated by updating ip_cnt. - * The implementation breaks down if someone blocks the thread - * that processes SYN requests for more than 5 minutes. Should never - * happen, and even if that happens only a not perfectly compliant - * ISN is generated, nothing fatal. - */ -static void rekey_seq_generator(struct work_struct *work) -{ - struct keydata *keyptr = &ip_keydata[1 ^ (ip_cnt & 1)]; - - get_random_bytes(keyptr->secret, sizeof(keyptr->secret)); - keyptr->count = (ip_cnt & COUNT_MASK) << HASH_BITS; - smp_wmb(); - ip_cnt++; - schedule_delayed_work(&rekey_work, - round_jiffies_relative(REKEY_INTERVAL)); -} - -static inline struct keydata *get_keyptr(void) -{ - struct keydata *keyptr = &ip_keydata[ip_cnt & 1]; - - smp_rmb(); - - return keyptr; -} - -static __init int seqgen_init(void) -{ - rekey_seq_generator(NULL); + get_random_bytes(random_int_secret, sizeof(random_int_secret)); return 0; } -late_initcall(seqgen_init); - -#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) -__u32 secure_tcpv6_sequence_number(__be32 *saddr, __be32 *daddr, - __be16 sport, __be16 dport) -{ - __u32 seq; - __u32 hash[12]; - struct keydata *keyptr = get_keyptr(); - - /* The procedure is the same as for IPv4, but addresses are longer. - * Thus we must use twothirdsMD4Transform. - */ - - memcpy(hash, saddr, 16); - hash[4] = ((__force u16)sport << 16) + (__force u16)dport; - memcpy(&hash[5], keyptr->secret, sizeof(__u32) * 7); - - seq = twothirdsMD4Transform((const __u32 *)daddr, hash) & HASH_MASK; - seq += keyptr->count; - - seq += ktime_to_ns(ktime_get_real()); - - return seq; -} -EXPORT_SYMBOL(secure_tcpv6_sequence_number); -#endif - -/* The code below is shamelessly stolen from secure_tcp_sequence_number(). - * All blames to Andrey V. Savochkin <saw@msu.ru>. - */ -__u32 secure_ip_id(__be32 daddr) -{ - struct keydata *keyptr; - __u32 hash[4]; - - keyptr = get_keyptr(); - - /* - * Pick a unique starting offset for each IP destination. - * The dest ip address is placed in the starting vector, - * which is then hashed with random data. - */ - hash[0] = (__force __u32)daddr; - hash[1] = keyptr->secret[9]; - hash[2] = keyptr->secret[10]; - hash[3] = keyptr->secret[11]; - - return half_md4_transform(hash, keyptr->secret); -} - -#ifdef CONFIG_INET - -__u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr, - __be16 sport, __be16 dport) -{ - __u32 seq; - __u32 hash[4]; - struct keydata *keyptr = get_keyptr(); - - /* - * Pick a unique starting offset for each TCP connection endpoints - * (saddr, daddr, sport, dport). - * Note that the words are placed into the starting vector, which is - * then mixed with a partial MD4 over random data. - */ - hash[0] = (__force u32)saddr; - hash[1] = (__force u32)daddr; - hash[2] = ((__force u16)sport << 16) + (__force u16)dport; - hash[3] = keyptr->secret[11]; - - seq = half_md4_transform(hash, keyptr->secret) & HASH_MASK; - seq += keyptr->count; - /* - * As close as possible to RFC 793, which - * suggests using a 250 kHz clock. - * Further reading shows this assumes 2 Mb/s networks. - * For 10 Mb/s Ethernet, a 1 MHz clock is appropriate. - * For 10 Gb/s Ethernet, a 1 GHz clock should be ok, but - * we also need to limit the resolution so that the u32 seq - * overlaps less than one time per MSL (2 minutes). - * Choosing a clock of 64 ns period is OK. (period of 274 s) - */ - seq += ktime_to_ns(ktime_get_real()) >> 6; - - return seq; -} - -/* Generate secure starting point for ephemeral IPV4 transport port search */ -u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport) -{ - struct keydata *keyptr = get_keyptr(); - u32 hash[4]; - - /* - * Pick a unique starting offset for each ephemeral port search - * (saddr, daddr, dport) and 48bits of random data. - */ - hash[0] = (__force u32)saddr; - hash[1] = (__force u32)daddr; - hash[2] = (__force u32)dport ^ keyptr->secret[10]; - hash[3] = keyptr->secret[11]; - - return half_md4_transform(hash, keyptr->secret); -} -EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral); - -#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) -u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr, - __be16 dport) -{ - struct keydata *keyptr = get_keyptr(); - u32 hash[12]; - - memcpy(hash, saddr, 16); - hash[4] = (__force u32)dport; - memcpy(&hash[5], keyptr->secret, sizeof(__u32) * 7); - - return twothirdsMD4Transform((const __u32 *)daddr, hash); -} -#endif - -#if defined(CONFIG_IP_DCCP) || defined(CONFIG_IP_DCCP_MODULE) -/* Similar to secure_tcp_sequence_number but generate a 48 bit value - * bit's 32-47 increase every key exchange - * 0-31 hash(source, dest) - */ -u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr, - __be16 sport, __be16 dport) -{ - u64 seq; - __u32 hash[4]; - struct keydata *keyptr = get_keyptr(); - - hash[0] = (__force u32)saddr; - hash[1] = (__force u32)daddr; - hash[2] = ((__force u16)sport << 16) + (__force u16)dport; - hash[3] = keyptr->secret[11]; - - seq = half_md4_transform(hash, keyptr->secret); - seq |= ((u64)keyptr->count) << (32 - HASH_BITS); - - seq += ktime_to_ns(ktime_get_real()); - seq &= (1ull << 48) - 1; - - return seq; -} -EXPORT_SYMBOL(secure_dccp_sequence_number); -#endif - -#endif /* CONFIG_INET */ - /* * Get a random word for internal kernel use only. Similar to urandom but @@ -1624,21 +1681,25 @@ EXPORT_SYMBOL(secure_dccp_sequence_number); * value is not cryptographically secure but for several uses the cost of * depleting entropy is too high */ -DEFINE_PER_CPU(__u32 [4], get_random_int_hash); +static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash); unsigned int get_random_int(void) { - struct keydata *keyptr; - __u32 *hash = get_cpu_var(get_random_int_hash); - int ret; + __u32 *hash; + unsigned int ret; + + if (arch_get_random_int(&ret)) + return ret; - keyptr = get_keyptr(); - hash[0] += current->pid + jiffies + get_cycles(); + hash = get_cpu_var(get_random_int_hash); - ret = half_md4_transform(hash, keyptr->secret); + hash[0] += current->pid + jiffies + random_get_entropy(); + md5_transform(hash, random_int_secret); + ret = hash[0]; put_cpu_var(get_random_int_hash); return ret; } +EXPORT_SYMBOL(get_random_int); /* * randomize_range() returns a start address such that |