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 } RandomFlags;
  14
  15 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 */
  16 void pseudo_random_bytes(void *p, size_t n);                    /* returns only pseudo-randommess (but possibly seeded from something better) */
  17 void random_bytes(void *p, size_t n);                           /* returns genuine randomness if cheaply available, and pseudo randomness if not. */
  18
  19 void initialize_srand(void);
  20
  21 static inline uint64_t random_u64(void) {
  22         uint64_t u;
  23         random_bytes(&u, sizeof(u));
  24         return u;
  25 }
  26
  27 static inline uint32_t random_u32(void) {
  28         uint32_t u;
  29         random_bytes(&u, sizeof(u));
  30         return u;
  31 }
  32
  33 int rdrand(unsigned long *ret);
  34
  35 /* Some limits on the pool sizes when we deal with the kernel random pool */
  36 #define RANDOM_POOL_SIZE_MIN 512U
  37 #define RANDOM_POOL_SIZE_MAX (10U*1024U*1024U)
  38
  39 size_t random_pool_size(void);