mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-23 01:10:04 +00:00
![Jason A. Donenfeld](/assets/img/avatar_default.png)
It is very useful to be able to know whether or not get_random_bytes_wait / wait_for_random_bytes is going to block or not, or whether plain get_random_bytes is going to return good randomness or bad randomness. The particular use case is for mitigating certain attacks in WireGuard. A handshake packet arrives and is queued up. Elsewhere a worker thread takes items from the queue and processes them. In replying to these items, it needs to use some random data, and it has to be good random data. If we simply block until we can have good randomness, then it's possible for an attacker to fill the queue up with packets waiting to be processed. Upon realizing the queue is full, WireGuard will detect that it's under a denial of service attack, and behave accordingly. A better approach is just to drop incoming handshake packets if the crng is not yet initialized. This patch, therefore, makes that information directly accessible. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
200 lines
5.1 KiB
C
200 lines
5.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
/*
|
|
* include/linux/random.h
|
|
*
|
|
* Include file for the random number generator.
|
|
*/
|
|
#ifndef _LINUX_RANDOM_H
|
|
#define _LINUX_RANDOM_H
|
|
|
|
#include <linux/list.h>
|
|
#include <linux/once.h>
|
|
|
|
#include <uapi/linux/random.h>
|
|
|
|
struct random_ready_callback {
|
|
struct list_head list;
|
|
void (*func)(struct random_ready_callback *rdy);
|
|
struct module *owner;
|
|
};
|
|
|
|
extern void add_device_randomness(const void *, unsigned int);
|
|
|
|
#if defined(CONFIG_GCC_PLUGIN_LATENT_ENTROPY) && !defined(__CHECKER__)
|
|
static inline void add_latent_entropy(void)
|
|
{
|
|
add_device_randomness((const void *)&latent_entropy,
|
|
sizeof(latent_entropy));
|
|
}
|
|
#else
|
|
static inline void add_latent_entropy(void) {}
|
|
#endif
|
|
|
|
extern void add_input_randomness(unsigned int type, unsigned int code,
|
|
unsigned int value) __latent_entropy;
|
|
extern void add_interrupt_randomness(int irq, int irq_flags) __latent_entropy;
|
|
|
|
extern void get_random_bytes(void *buf, int nbytes);
|
|
extern int wait_for_random_bytes(void);
|
|
extern bool rng_is_initialized(void);
|
|
extern int add_random_ready_callback(struct random_ready_callback *rdy);
|
|
extern void del_random_ready_callback(struct random_ready_callback *rdy);
|
|
extern int __must_check get_random_bytes_arch(void *buf, int nbytes);
|
|
|
|
#ifndef MODULE
|
|
extern const struct file_operations random_fops, urandom_fops;
|
|
#endif
|
|
|
|
u32 get_random_u32(void);
|
|
u64 get_random_u64(void);
|
|
static inline unsigned int get_random_int(void)
|
|
{
|
|
return get_random_u32();
|
|
}
|
|
static inline unsigned long get_random_long(void)
|
|
{
|
|
#if BITS_PER_LONG == 64
|
|
return get_random_u64();
|
|
#else
|
|
return get_random_u32();
|
|
#endif
|
|
}
|
|
|
|
/*
|
|
* On 64-bit architectures, protect against non-terminated C string overflows
|
|
* by zeroing out the first byte of the canary; this leaves 56 bits of entropy.
|
|
*/
|
|
#ifdef CONFIG_64BIT
|
|
# ifdef __LITTLE_ENDIAN
|
|
# define CANARY_MASK 0xffffffffffffff00UL
|
|
# else /* big endian, 64 bits: */
|
|
# define CANARY_MASK 0x00ffffffffffffffUL
|
|
# endif
|
|
#else /* 32 bits: */
|
|
# define CANARY_MASK 0xffffffffUL
|
|
#endif
|
|
|
|
static inline unsigned long get_random_canary(void)
|
|
{
|
|
unsigned long val = get_random_long();
|
|
|
|
return val & CANARY_MASK;
|
|
}
|
|
|
|
/* Calls wait_for_random_bytes() and then calls get_random_bytes(buf, nbytes).
|
|
* Returns the result of the call to wait_for_random_bytes. */
|
|
static inline int get_random_bytes_wait(void *buf, int nbytes)
|
|
{
|
|
int ret = wait_for_random_bytes();
|
|
get_random_bytes(buf, nbytes);
|
|
return ret;
|
|
}
|
|
|
|
#define declare_get_random_var_wait(var) \
|
|
static inline int get_random_ ## var ## _wait(var *out) { \
|
|
int ret = wait_for_random_bytes(); \
|
|
if (unlikely(ret)) \
|
|
return ret; \
|
|
*out = get_random_ ## var(); \
|
|
return 0; \
|
|
}
|
|
declare_get_random_var_wait(u32)
|
|
declare_get_random_var_wait(u64)
|
|
declare_get_random_var_wait(int)
|
|
declare_get_random_var_wait(long)
|
|
#undef declare_get_random_var
|
|
|
|
unsigned long randomize_page(unsigned long start, unsigned long range);
|
|
|
|
u32 prandom_u32(void);
|
|
void prandom_bytes(void *buf, size_t nbytes);
|
|
void prandom_seed(u32 seed);
|
|
void prandom_reseed_late(void);
|
|
|
|
struct rnd_state {
|
|
__u32 s1, s2, s3, s4;
|
|
};
|
|
|
|
u32 prandom_u32_state(struct rnd_state *state);
|
|
void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes);
|
|
void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state);
|
|
|
|
#define prandom_init_once(pcpu_state) \
|
|
DO_ONCE(prandom_seed_full_state, (pcpu_state))
|
|
|
|
/**
|
|
* prandom_u32_max - returns a pseudo-random number in interval [0, ep_ro)
|
|
* @ep_ro: right open interval endpoint
|
|
*
|
|
* Returns a pseudo-random number that is in interval [0, ep_ro). Note
|
|
* that the result depends on PRNG being well distributed in [0, ~0U]
|
|
* u32 space. Here we use maximally equidistributed combined Tausworthe
|
|
* generator, that is, prandom_u32(). This is useful when requesting a
|
|
* random index of an array containing ep_ro elements, for example.
|
|
*
|
|
* Returns: pseudo-random number in interval [0, ep_ro)
|
|
*/
|
|
static inline u32 prandom_u32_max(u32 ep_ro)
|
|
{
|
|
return (u32)(((u64) prandom_u32() * ep_ro) >> 32);
|
|
}
|
|
|
|
/*
|
|
* Handle minimum values for seeds
|
|
*/
|
|
static inline u32 __seed(u32 x, u32 m)
|
|
{
|
|
return (x < m) ? x + m : x;
|
|
}
|
|
|
|
/**
|
|
* prandom_seed_state - set seed for prandom_u32_state().
|
|
* @state: pointer to state structure to receive the seed.
|
|
* @seed: arbitrary 64-bit value to use as a seed.
|
|
*/
|
|
static inline void prandom_seed_state(struct rnd_state *state, u64 seed)
|
|
{
|
|
u32 i = (seed >> 32) ^ (seed << 10) ^ seed;
|
|
|
|
state->s1 = __seed(i, 2U);
|
|
state->s2 = __seed(i, 8U);
|
|
state->s3 = __seed(i, 16U);
|
|
state->s4 = __seed(i, 128U);
|
|
}
|
|
|
|
#ifdef CONFIG_ARCH_RANDOM
|
|
# include <asm/archrandom.h>
|
|
#else
|
|
static inline bool arch_get_random_long(unsigned long *v)
|
|
{
|
|
return 0;
|
|
}
|
|
static inline bool arch_get_random_int(unsigned int *v)
|
|
{
|
|
return 0;
|
|
}
|
|
static inline bool arch_has_random(void)
|
|
{
|
|
return 0;
|
|
}
|
|
static inline bool arch_get_random_seed_long(unsigned long *v)
|
|
{
|
|
return 0;
|
|
}
|
|
static inline bool arch_get_random_seed_int(unsigned int *v)
|
|
{
|
|
return 0;
|
|
}
|
|
static inline bool arch_has_random_seed(void)
|
|
{
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
/* Pseudo random number generator from numerical recipes. */
|
|
static inline u32 next_pseudo_random32(u32 seed)
|
|
{
|
|
return seed * 1664525 + 1013904223;
|
|
}
|
|
|
|
#endif /* _LINUX_RANDOM_H */
|