diff options
| -rw-r--r-- | drivers/char/random.c | 28 | ||||
| -rw-r--r-- | include/linux/random.h | 1 |
2 files changed, 29 insertions, 0 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 315feb1f59f3..df3358ab5b99 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -125,11 +125,20 @@ * 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, 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. * @@ -646,6 +655,25 @@ static void set_timer_rand_state(unsigned int irq, } #endif +/* + * 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) +{ + unsigned long time = get_cycles() ^ jiffies; + + 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); +} +EXPORT_SYMBOL(add_device_randomness); + static struct timer_rand_state input_timer_state; /* diff --git a/include/linux/random.h b/include/linux/random.h index 6ef39d7f2db1..e14b4387354a 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -50,6 +50,7 @@ struct rnd_state { extern void rand_initialize_irq(int irq); +extern void add_device_randomness(const void *, unsigned int); extern void add_input_randomness(unsigned int type, unsigned int code, unsigned int value); extern void add_interrupt_randomness(int irq, int irq_flags); |