src/basic/random-util.h

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 #pragma once
   3
   4 #include <stdbool.h>
   5 #include <stddef.h>
   6 #include <stdint.h>
   7
   8 typedef enum RandomFlags {
   9         RANDOM_EXTEND_WITH_PSEUDO = 1 << 0, /* If we can't get enough genuine randomness, but some, fill up the rest with pseudo-randomness */
  10         RANDOM_BLOCK              = 1 << 1, /* Rather block than return crap randomness (only if the kernel supports that) */
  11         RANDOM_MAY_FAIL           = 1 << 2, /* If we can't get any randomness at all, return early with -ENODATA */
  12         RANDOM_ALLOW_RDRAND       = 1 << 3, /* Allow usage of the CPU RNG */
  13         RANDOM_ALLOW_INSECURE     = 1 << 4, /* Allow usage of GRND_INSECURE flag to kernel's getrandom() API */
  14 } RandomFlags;
  15
  16 int genuine_random_bytes(void *p, size_t n, RandomFlags flags); /* returns "genuine" randomness, optionally filled up with pseudo random, if not enough is available */
  17 void pseudo_random_bytes(void *p, size_t n);                    /* returns only pseudo-randommess (but possibly seeded from something better) */
  18 void random_bytes(void *p, size_t n);                           /* returns genuine randomness if cheaply available, and pseudo randomness if not. */
  19
  20 void initialize_srand(void);
  21
  22 static inline uint64_t random_u64(void) {
  23         uint64_t u;
  24         random_bytes(&u, sizeof(u));
  25         return u;
  26 }
  27
  28 static inline uint32_t random_u32(void) {
  29         uint32_t u;
  30         random_bytes(&u, sizeof(u));
  31         return u;
  32 }
  33
  34 int rdrand(unsigned long *ret);
  35
  36 /* Some limits on the pool sizes when we deal with the kernel random pool */
  37 #define RANDOM_POOL_SIZE_MIN 512U
  38 #define RANDOM_POOL_SIZE_MAX (10U*1024U*1024U)
  39
  40 size_t random_pool_size(void);
  41
  42 int random_write_entropy(int fd, const void *seed, size_t size, bool credit);