From: "Jason A. Donenfeld" Jason@zx2c4.com
commit 92c653cf14400946f376a29b828d6af7e01f38dd upstream.
This pulls all of the entropy collection-focused functions into the fourth labeled section.
No functional changes.
Cc: Theodore Ts'o tytso@mit.edu Reviewed-by: Dominik Brodowski linux@dominikbrodowski.net Reviewed-by: Eric Biggers ebiggers@google.com Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/char/random.c | 370 +++++++++++++++++++++++++++----------------------- 1 file changed, 206 insertions(+), 164 deletions(-)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1035,60 +1035,112 @@ static bool drain_entropy(void *buf, siz return true; }
-struct fast_pool { - union { - u32 pool32[4]; - u64 pool64[2]; - }; - unsigned long last; - u16 reg_idx; - u8 count; -}; + +/********************************************************************** + * + * Entropy collection routines. + * + * The following exported functions are used for pushing entropy into + * the above entropy accumulation routines: + * + * void add_device_randomness(const void *buf, size_t size); + * void add_input_randomness(unsigned int type, unsigned int code, + * unsigned int value); + * void add_disk_randomness(struct gendisk *disk); + * void add_hwgenerator_randomness(const void *buffer, size_t count, + * size_t entropy); + * void add_bootloader_randomness(const void *buf, size_t size); + * void add_interrupt_randomness(int irq); + * + * add_device_randomness() adds data to the input 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* credit 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_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. + * + * The above two routines try to estimate how many bits of entropy + * to credit. They do this by keeping track of the first and second + * order deltas of the event timings. + * + * add_hwgenerator_randomness() is for true hardware RNGs, and will credit + * entropy as specified by the caller. If the entropy pool is full it will + * block until more entropy is needed. + * + * add_bootloader_randomness() is the same as add_hwgenerator_randomness() or + * add_device_randomness(), depending on whether or not the configuration + * option CONFIG_RANDOM_TRUST_BOOTLOADER is set. + * + * 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 input pool roughly once a second or after 64 + * interrupts, crediting 1 bit of entropy for whichever comes first. + * + **********************************************************************/ + +static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU); +static int __init parse_trust_cpu(char *arg) +{ + return kstrtobool(arg, &trust_cpu); +} +early_param("random.trust_cpu", parse_trust_cpu);
/* - * 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. + * The first collection of entropy occurs at system boot while interrupts + * are still turned off. Here we push in RDSEED, a timestamp, and utsname(). + * Depending on the above configuration knob, RDSEED may be considered + * sufficient for initialization. Note that much earlier setup may already + * have pushed entropy into the input pool by the time we get here. */ -static void fast_mix(u32 pool[4]) +int __init rand_initialize(void) { - u32 a = pool[0], b = pool[1]; - u32 c = pool[2], d = pool[3]; - - a += b; c += d; - b = rol32(b, 6); d = rol32(d, 27); - d ^= a; b ^= c; + size_t i; + ktime_t now = ktime_get_real(); + bool arch_init = true; + unsigned long rv;
- a += b; c += d; - b = rol32(b, 16); d = rol32(d, 14); - d ^= a; b ^= c; + for (i = 0; i < BLAKE2S_BLOCK_SIZE; i += sizeof(rv)) { + if (!arch_get_random_seed_long_early(&rv) && + !arch_get_random_long_early(&rv)) { + rv = random_get_entropy(); + arch_init = false; + } + mix_pool_bytes(&rv, sizeof(rv)); + } + mix_pool_bytes(&now, sizeof(now)); + mix_pool_bytes(utsname(), sizeof(*(utsname())));
- a += b; c += d; - b = rol32(b, 6); d = rol32(d, 27); - d ^= a; b ^= c; + extract_entropy(base_crng.key, sizeof(base_crng.key)); + ++base_crng.generation;
- a += b; c += d; - b = rol32(b, 16); d = rol32(d, 14); - d ^= a; b ^= c; + if (arch_init && trust_cpu && crng_init < 2) { + crng_init = 2; + pr_notice("crng init done (trusting CPU's manufacturer)\n"); + }
- pool[0] = a; pool[1] = b; - pool[2] = c; pool[3] = d; + if (ratelimit_disable) { + urandom_warning.interval = 0; + unseeded_warning.interval = 0; + } + return 0; }
-/********************************************************************* - * - * Entropy input management - * - *********************************************************************/ - /* There is one of these per entropy source */ struct timer_rand_state { cycles_t last_time; long last_delta, last_delta2; };
-#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, }; - /* * Add device- or boot-specific data to the input pool to help * initialize it. @@ -1112,8 +1164,6 @@ void add_device_randomness(const void *b } EXPORT_SYMBOL(add_device_randomness);
-static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE; - /* * This function adds entropy to the entropy "pool" by using timing * delays. It uses the timer_rand_state structure to make an estimate @@ -1175,8 +1225,9 @@ void add_input_randomness(unsigned int t unsigned int value) { static unsigned char last_value; + static struct timer_rand_state input_timer_state = { INITIAL_JIFFIES };
- /* ignore autorepeat and the like */ + /* Ignore autorepeat and the like. */ if (value == last_value) return;
@@ -1186,6 +1237,119 @@ void add_input_randomness(unsigned int t } EXPORT_SYMBOL_GPL(add_input_randomness);
+#ifdef CONFIG_BLOCK +void add_disk_randomness(struct gendisk *disk) +{ + if (!disk || !disk->random) + return; + /* First major is 1, so we get >= 0x200 here. */ + add_timer_randomness(disk->random, 0x100 + disk_devt(disk)); +} +EXPORT_SYMBOL_GPL(add_disk_randomness); + +void rand_initialize_disk(struct gendisk *disk) +{ + struct timer_rand_state *state; + + /* + * If kzalloc returns null, we just won't use that entropy + * source. + */ + state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL); + if (state) { + state->last_time = INITIAL_JIFFIES; + disk->random = state; + } +} +#endif + +/* + * Interface for in-kernel drivers of true hardware RNGs. + * Those devices may produce endless random bits and will be throttled + * when our pool is full. + */ +void add_hwgenerator_randomness(const void *buffer, size_t count, + size_t entropy) +{ + if (unlikely(crng_init == 0)) { + size_t ret = crng_fast_load(buffer, count); + mix_pool_bytes(buffer, ret); + count -= ret; + buffer += ret; + if (!count || crng_init == 0) + return; + } + + /* + * Throttle writing if we're above the trickle threshold. + * We'll be woken up again once below POOL_MIN_BITS, when + * the calling thread is about to terminate, or once + * CRNG_RESEED_INTERVAL has elapsed. + */ + wait_event_interruptible_timeout(random_write_wait, + !system_wq || kthread_should_stop() || + input_pool.entropy_count < POOL_MIN_BITS, + CRNG_RESEED_INTERVAL); + mix_pool_bytes(buffer, count); + credit_entropy_bits(entropy); +} +EXPORT_SYMBOL_GPL(add_hwgenerator_randomness); + +/* + * Handle random seed passed by bootloader. + * If the seed is trustworthy, it would be regarded as hardware RNGs. Otherwise + * it would be regarded as device data. + * The decision is controlled by CONFIG_RANDOM_TRUST_BOOTLOADER. + */ +void add_bootloader_randomness(const void *buf, size_t size) +{ + if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER)) + add_hwgenerator_randomness(buf, size, size * 8); + else + add_device_randomness(buf, size); +} +EXPORT_SYMBOL_GPL(add_bootloader_randomness); + +struct fast_pool { + union { + u32 pool32[4]; + u64 pool64[2]; + }; + unsigned long last; + u16 reg_idx; + u8 count; +}; + +/* + * 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(u32 pool[4]) +{ + u32 a = pool[0], b = pool[1]; + u32 c = pool[2], d = pool[3]; + + a += b; c += d; + b = rol32(b, 6); d = rol32(d, 27); + d ^= a; b ^= c; + + a += b; c += d; + b = rol32(b, 16); d = rol32(d, 14); + d ^= a; b ^= c; + + a += b; c += d; + b = rol32(b, 6); d = rol32(d, 27); + d ^= a; b ^= c; + + a += b; c += d; + b = rol32(b, 16); d = rol32(d, 14); + d ^= a; b ^= c; + + pool[0] = a; pool[1] = b; + pool[2] = c; pool[3] = d; +} + static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
static u32 get_reg(struct fast_pool *f, struct pt_regs *regs) @@ -1255,22 +1419,11 @@ void add_interrupt_randomness(int irq)
fast_pool->count = 0;
- /* award one bit for the contents of the fast pool */ + /* Award one bit for the contents of the fast pool. */ credit_entropy_bits(1); } EXPORT_SYMBOL_GPL(add_interrupt_randomness);
-#ifdef CONFIG_BLOCK -void add_disk_randomness(struct gendisk *disk) -{ - if (!disk || !disk->random) - return; - /* first major is 1, so we get >= 0x200 here */ - add_timer_randomness(disk->random, 0x100 + disk_devt(disk)); -} -EXPORT_SYMBOL_GPL(add_disk_randomness); -#endif - /* * Each time the timer fires, we expect that we got an unpredictable * jump in the cycle counter. Even if the timer is running on another @@ -1320,73 +1473,6 @@ static void try_to_generate_entropy(void mix_pool_bytes(&stack.now, sizeof(stack.now)); }
-static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU); -static int __init parse_trust_cpu(char *arg) -{ - return kstrtobool(arg, &trust_cpu); -} -early_param("random.trust_cpu", parse_trust_cpu); - -/* - * 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. - */ -int __init rand_initialize(void) -{ - size_t i; - ktime_t now = ktime_get_real(); - bool arch_init = true; - unsigned long rv; - - for (i = 0; i < BLAKE2S_BLOCK_SIZE; i += sizeof(rv)) { - if (!arch_get_random_seed_long_early(&rv) && - !arch_get_random_long_early(&rv)) { - rv = random_get_entropy(); - arch_init = false; - } - mix_pool_bytes(&rv, sizeof(rv)); - } - mix_pool_bytes(&now, sizeof(now)); - mix_pool_bytes(utsname(), sizeof(*(utsname()))); - - extract_entropy(base_crng.key, sizeof(base_crng.key)); - ++base_crng.generation; - - if (arch_init && trust_cpu && crng_init < 2) { - crng_init = 2; - pr_notice("crng init done (trusting CPU's manufacturer)\n"); - } - - if (ratelimit_disable) { - urandom_warning.interval = 0; - unseeded_warning.interval = 0; - } - return 0; -} - -#ifdef CONFIG_BLOCK -void rand_initialize_disk(struct gendisk *disk) -{ - struct timer_rand_state *state; - - /* - * If kzalloc returns null, we just won't use that entropy - * source. - */ - state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL); - if (state) { - state->last_time = INITIAL_JIFFIES; - disk->random = state; - } -} -#endif - static ssize_t urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) { @@ -1669,47 +1755,3 @@ struct ctl_table random_table[] = { { } }; #endif /* CONFIG_SYSCTL */ - -/* Interface for in-kernel drivers of true hardware RNGs. - * Those devices may produce endless random bits and will be throttled - * when our pool is full. - */ -void add_hwgenerator_randomness(const void *buffer, size_t count, - size_t entropy) -{ - if (unlikely(crng_init == 0)) { - size_t ret = crng_fast_load(buffer, count); - mix_pool_bytes(buffer, ret); - count -= ret; - buffer += ret; - if (!count || crng_init == 0) - return; - } - - /* Throttle writing if we're above the trickle threshold. - * We'll be woken up again once below POOL_MIN_BITS, when - * the calling thread is about to terminate, or once - * CRNG_RESEED_INTERVAL has elapsed. - */ - wait_event_interruptible_timeout(random_write_wait, - !system_wq || kthread_should_stop() || - input_pool.entropy_count < POOL_MIN_BITS, - CRNG_RESEED_INTERVAL); - mix_pool_bytes(buffer, count); - credit_entropy_bits(entropy); -} -EXPORT_SYMBOL_GPL(add_hwgenerator_randomness); - -/* Handle random seed passed by bootloader. - * If the seed is trustworthy, it would be regarded as hardware RNGs. Otherwise - * it would be regarded as device data. - * The decision is controlled by CONFIG_RANDOM_TRUST_BOOTLOADER. - */ -void add_bootloader_randomness(const void *buf, size_t size) -{ - if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER)) - add_hwgenerator_randomness(buf, size, size * 8); - else - add_device_randomness(buf, size); -} -EXPORT_SYMBOL_GPL(add_bootloader_randomness);