CPRNG(9) | Kernel Developer's Manual | CPRNG(9) |
cprng_strong_t *
cprng_strong_create(const char *name, int ipl, int flags);
void
cprng_strong_destroy(cprng_strong_t *cprng);
size_t
cprng_strong(cprng_strong_t *cprng, void *buf, size_t len, int flags);
uint32_t
cprng_strong32(void);
uint64_t
cprng_strong64(void);
size_t
cprng_fast(void *buf, size_t len);
uint32_t
cprng_fast32(void);
uint32_t
cprng_fast64(void);
#define CPRNG_MAX_LEN 524288
The “strong” family of functions use cryptographically strong pseudorandom number generators suitable for keying crypto systems and similar purposes. Calls to rnd_extract_data(9) should be replaced by calls to cprng_strong().
The “fast” family of functions use cryptographically weaker pseudorandom number generators suitable for initialization vectors, nonces in certain protocols, and other similar purposes, using a faster but less secure stream-cipher-based generator. Calls to arc4random(9) should be replaced by calls to cprng_fast32(), and calls to arc4randbytes(9) should be replaced by calls to cprng_fast().
A single instance of the fast generator serves the entire kernel. A well-known instance of the strong generator, kern_cprng, may be used by any in-kernel caller, but separately seeded instances of the strong generator can also be created by calling cprng_strong_create().
The name argument is used to “personalize” the CTR_DRBG according to the standard, so that its initial state will depend both on seed material from the entropy pool and also on the personalization string (name).
The ipl argument specifies the interrupt priority level for the mutex which will serialize access to the new instance of the generator (see spl(9)), and must be no higher than IPL_VM.
The flags argument controls the behavior of the generator:
Creation will succeed even if full entropy for the generator is not available. In this case, the first request to read from the generator may cause reseeding.
cprng_strong_create() may sleep to allocate memory.
cprng_strong_destroy() may sleep.
If cprng was created with the CPRNG_USE_CV flag and has been exhausted, then cprng_strong() may sleep until full entropy can be obtained from the entropy pool to reseed it. However, if flags includes the FNONBLOCK flag, then cprng_strong() will immediately return zero in this case instead.
If cprng was created with the CPRNG_HARD flag, then cprng_strong() will return at most as many bytes as are left from its seed size since the last reseeding.
If cprng was created with neither the CPRNG_USE_CV flag nor the CPRNG_HARD flag, then cprng_strong() is guaranteed to return as many bytes as requested, up to CPRNG_MAX_LEN, without sleeping.
cprng_strong32() does not sleep.
cprng_strong64() does not sleep.
cprng_fast() does not sleep.
cprng_fast32() does not sleep.
cprng_fast64() does not sleep.
Elaine Barker and John Kelsey, Recommendation for Random Number Generation Using Deterministic Random Bit Generators (Revised), National Institute of Standards and Technology, 2011, NIST Special Publication 800-90A, Rev 1.
July 18, 2013 | NetBSD 6.99 |