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ae099e8e98
When a VM forks, we must immediately mix in additional information to the stream of random output so that two forks or a rollback don't produce the same stream of random numbers, which could have catastrophic cryptographic consequences. This commit adds a simple API, add_vmfork_ randomness(), for that, by force reseeding the crng. This has the added benefit of also draining the entropy pool and setting its timer back, so that any old entropy that was there prior -- which could have already been used by a different fork, or generally gone stale -- does not contribute to the accounting of the next 256 bits. Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Theodore Ts'o <tytso@mit.edu> Cc: Jann Horn <jannh@google.com> Cc: Eric Biggers <ebiggers@google.com> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
165 lines
4.3 KiB
C
165 lines
4.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_RANDOM_H
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#define _LINUX_RANDOM_H
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#include <linux/bug.h>
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#include <linux/kernel.h>
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#include <linux/list.h>
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#include <linux/once.h>
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#include <uapi/linux/random.h>
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struct random_ready_callback {
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struct list_head list;
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void (*func)(struct random_ready_callback *rdy);
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struct module *owner;
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};
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extern void add_device_randomness(const void *, size_t);
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extern void add_bootloader_randomness(const void *, size_t);
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#if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__)
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static inline void add_latent_entropy(void)
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{
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add_device_randomness((const void *)&latent_entropy,
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sizeof(latent_entropy));
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}
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#else
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static inline void add_latent_entropy(void) {}
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#endif
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extern void add_input_randomness(unsigned int type, unsigned int code,
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unsigned int value) __latent_entropy;
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extern void add_interrupt_randomness(int irq) __latent_entropy;
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extern void add_hwgenerator_randomness(const void *buffer, size_t count,
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size_t entropy);
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extern void add_vmfork_randomness(const void *unique_vm_id, size_t size);
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extern void get_random_bytes(void *buf, size_t nbytes);
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extern int wait_for_random_bytes(void);
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extern int __init rand_initialize(void);
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extern bool rng_is_initialized(void);
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extern int add_random_ready_callback(struct random_ready_callback *rdy);
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extern void del_random_ready_callback(struct random_ready_callback *rdy);
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extern size_t __must_check get_random_bytes_arch(void *buf, size_t nbytes);
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#ifndef MODULE
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extern const struct file_operations random_fops;
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#endif
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u32 get_random_u32(void);
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u64 get_random_u64(void);
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static inline unsigned int get_random_int(void)
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{
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return get_random_u32();
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}
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static inline unsigned long get_random_long(void)
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{
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#if BITS_PER_LONG == 64
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return get_random_u64();
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#else
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return get_random_u32();
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#endif
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}
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/*
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* On 64-bit architectures, protect against non-terminated C string overflows
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* by zeroing out the first byte of the canary; this leaves 56 bits of entropy.
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*/
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#ifdef CONFIG_64BIT
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# ifdef __LITTLE_ENDIAN
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# define CANARY_MASK 0xffffffffffffff00UL
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# else /* big endian, 64 bits: */
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# define CANARY_MASK 0x00ffffffffffffffUL
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# endif
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#else /* 32 bits: */
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# define CANARY_MASK 0xffffffffUL
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#endif
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static inline unsigned long get_random_canary(void)
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{
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unsigned long val = get_random_long();
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return val & CANARY_MASK;
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}
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/* Calls wait_for_random_bytes() and then calls get_random_bytes(buf, nbytes).
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* Returns the result of the call to wait_for_random_bytes. */
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static inline int get_random_bytes_wait(void *buf, size_t nbytes)
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{
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int ret = wait_for_random_bytes();
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get_random_bytes(buf, nbytes);
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return ret;
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}
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#define declare_get_random_var_wait(var) \
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static inline int get_random_ ## var ## _wait(var *out) { \
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int ret = wait_for_random_bytes(); \
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if (unlikely(ret)) \
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return ret; \
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*out = get_random_ ## var(); \
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return 0; \
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}
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declare_get_random_var_wait(u32)
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declare_get_random_var_wait(u64)
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declare_get_random_var_wait(int)
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declare_get_random_var_wait(long)
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#undef declare_get_random_var
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unsigned long randomize_page(unsigned long start, unsigned long range);
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/*
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* This is designed to be standalone for just prandom
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* users, but for now we include it from <linux/random.h>
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* for legacy reasons.
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*/
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#include <linux/prandom.h>
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#ifdef CONFIG_ARCH_RANDOM
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# include <asm/archrandom.h>
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#else
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static inline bool __must_check arch_get_random_long(unsigned long *v)
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{
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return false;
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}
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static inline bool __must_check arch_get_random_int(unsigned int *v)
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{
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return false;
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}
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static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
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{
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return false;
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}
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static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
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{
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return false;
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}
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#endif
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/*
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* Called from the boot CPU during startup; not valid to call once
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* secondary CPUs are up and preemption is possible.
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*/
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#ifndef arch_get_random_seed_long_early
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static inline bool __init arch_get_random_seed_long_early(unsigned long *v)
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{
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WARN_ON(system_state != SYSTEM_BOOTING);
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return arch_get_random_seed_long(v);
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}
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#endif
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#ifndef arch_get_random_long_early
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static inline bool __init arch_get_random_long_early(unsigned long *v)
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{
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WARN_ON(system_state != SYSTEM_BOOTING);
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return arch_get_random_long(v);
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}
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#endif
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#ifdef CONFIG_SMP
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extern int random_prepare_cpu(unsigned int cpu);
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extern int random_online_cpu(unsigned int cpu);
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#endif
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#endif /* _LINUX_RANDOM_H */
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