diff options
| -rw-r--r-- | drivers/char/mem.c | 2 | ||||
| -rw-r--r-- | drivers/char/random.c | 72 | ||||
| -rw-r--r-- | include/linux/random.h | 2 |
3 files changed, 57 insertions, 19 deletions
diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 9f586025dbe6..cc296f0823bd 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -707,7 +707,7 @@ static const struct memdev { [5] = { "zero", 0666, &zero_fops, FMODE_NOWAIT }, [7] = { "full", 0666, &full_fops, 0 }, [8] = { "random", 0666, &random_fops, 0 }, - [9] = { "urandom", 0666, &random_fops, 0 }, + [9] = { "urandom", 0666, &urandom_fops, 0 }, #ifdef CONFIG_PRINTK [11] = { "kmsg", 0644, &kmsg_fops, 0 }, #endif diff --git a/drivers/char/random.c b/drivers/char/random.c index 85f4cca6e707..66ce7c03a142 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -89,14 +89,17 @@ static RAW_NOTIFIER_HEAD(random_ready_chain); /* Control how we warn userspace. */ static struct ratelimit_state unseeded_warning = RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3); +static struct ratelimit_state urandom_warning = + RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3); static int ratelimit_disable __read_mostly; module_param_named(ratelimit_disable, ratelimit_disable, int, 0644); MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression"); /* * Returns whether or not the input pool has been seeded and thus guaranteed - * to supply cryptographically secure random numbers. This applies to - * get_random_bytes() and get_random_{u32,u64,int,long}(). + * to supply cryptographically secure random numbers. This applies to: the + * /dev/urandom device, the get_random_bytes function, and the get_random_{u32, + * ,u64,int,long} family of functions. * * Returns: true if the input pool has been seeded. * false if the input pool has not been seeded. @@ -112,10 +115,10 @@ static void try_to_generate_entropy(void); /* * Wait for the input pool to be seeded and thus guaranteed to supply - * cryptographically secure random numbers. This applies to - * get_random_bytes() and get_random_{u32,u64,int,long}(). Using any - * of these functions without first calling this function means that - * the returned numbers might not be cryptographically secure. + * cryptographically secure random numbers. This applies to: the /dev/urandom + * device, the get_random_bytes function, and the get_random_{u32,u64,int,long} + * family of functions. Using any of these functions without first calling + * this function forfeits the guarantee of security. * * Returns: 0 if the input pool has been seeded. * -ERESTARTSYS if the function was interrupted by a signal. @@ -220,10 +223,10 @@ static void _warn_unseeded_randomness(const char *func_name, void *caller, void * unsigned long get_random_long() * * These interfaces will return the requested number of random bytes - * into the given buffer or as a return value. The returned numbers are - * the same as those of getrandom(0). The integer family of functions may - * be higher performance for one-off random integers, because they do a - * bit of buffering and do not invoke reseeding. + * into the given buffer or as a return value. This is equivalent to + * a read from /dev/urandom. The integer family of functions may be + * higher performance for one-off random integers, because they do a + * bit of buffering. * *********************************************************************/ @@ -300,6 +303,11 @@ static void crng_reseed(bool force) unseeded_warning.missed); unseeded_warning.missed = 0; } + if (urandom_warning.missed) { + pr_notice("%d urandom warning(s) missed due to ratelimiting\n", + urandom_warning.missed); + urandom_warning.missed = 0; + } } } @@ -979,8 +987,10 @@ int __init rand_initialize(void) pr_notice("crng init done (trusting CPU's manufacturer)\n"); } - if (ratelimit_disable) + if (ratelimit_disable) { + urandom_warning.interval = 0; unseeded_warning.interval = 0; + } return 0; } @@ -1420,16 +1430,20 @@ static void try_to_generate_entropy(void) * getrandom(2) is the primary modern interface into the RNG and should * be used in preference to anything else. * - * Reading from /dev/random and /dev/urandom both have the same effect - * as calling getrandom(2) with flags=0. (In earlier versions, however, - * they each had different semantics.) + * Reading from /dev/random has the same functionality as calling + * getrandom(2) with flags=0. In earlier versions, however, it had + * vastly different semantics and should therefore be avoided, to + * prevent backwards compatibility issues. + * + * Reading from /dev/urandom has the same functionality as calling + * getrandom(2) with flags=GRND_INSECURE. Because it does not block + * waiting for the RNG to be ready, it should not be used. * * Writing to either /dev/random or /dev/urandom adds entropy to * the input pool but does not credit it. * - * Polling on /dev/random or /dev/urandom indicates when the RNG - * is initialized, on the read side, and when it wants new entropy, - * on the write side. + * Polling on /dev/random indicates when the RNG is initialized, on + * the read side, and when it wants new entropy, on the write side. * * Both /dev/random and /dev/urandom have the same set of ioctls for * adding entropy, getting the entropy count, zeroing the count, and @@ -1514,6 +1528,21 @@ static ssize_t random_write(struct file *file, const char __user *buffer, return (ssize_t)count; } +static ssize_t urandom_read(struct file *file, char __user *buf, size_t nbytes, + loff_t *ppos) +{ + static int maxwarn = 10; + + if (!crng_ready() && maxwarn > 0) { + maxwarn--; + if (__ratelimit(&urandom_warning)) + pr_notice("%s: uninitialized urandom read (%zd bytes read)\n", + current->comm, nbytes); + } + + return get_random_bytes_user(buf, nbytes); +} + static ssize_t random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) { @@ -1600,6 +1629,15 @@ const struct file_operations random_fops = { .llseek = noop_llseek, }; +const struct file_operations urandom_fops = { + .read = urandom_read, + .write = random_write, + .unlocked_ioctl = random_ioctl, + .compat_ioctl = compat_ptr_ioctl, + .fasync = random_fasync, + .llseek = noop_llseek, +}; + /******************************************************************** * diff --git a/include/linux/random.h b/include/linux/random.h index c0baffe7afb1..f673fbb838b3 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -48,7 +48,7 @@ extern int unregister_random_ready_notifier(struct notifier_block *nb); extern size_t __must_check get_random_bytes_arch(void *buf, size_t nbytes); #ifndef MODULE -extern const struct file_operations random_fops; +extern const struct file_operations random_fops, urandom_fops; #endif u32 get_random_u32(void); |