include/openssl/rand.h

/* Copyright (c) 2014, Google Inc.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#ifndef OPENSSL_HEADER_RAND_H
#define OPENSSL_HEADER_RAND_H

#include <openssl/base.h>

#if defined(__cplusplus)
extern "C" {
#endif


// Random number generation.


// RAND_bytes writes |len| bytes of random data to |buf| and returns one.
OPENSSL_EXPORT int RAND_bytes(uint8_t *buf, size_t len);

// RAND_cleanup frees any resources used by the RNG. This is not safe if other
// threads might still be calling |RAND_bytes|.
OPENSSL_EXPORT void RAND_cleanup(void);


// Obscure functions.

#if !defined(OPENSSL_WINDOWS)
// RAND_set_urandom_fd causes the module to use a copy of |fd| for system
// randomness rather opening /dev/urandom internally. The caller retains
// ownership of |fd| and is at liberty to close it at any time. This is useful
// if, due to a sandbox, /dev/urandom isn't available. If used, it must be
// called before the first call to |RAND_bytes|, and it is mutually exclusive
// with |RAND_enable_fork_unsafe_buffering|.
//
// |RAND_set_urandom_fd| does not buffer any entropy, so it is safe to call
// |fork| at any time after calling |RAND_set_urandom_fd|.
OPENSSL_EXPORT void RAND_set_urandom_fd(int fd);

// RAND_enable_fork_unsafe_buffering enables efficient buffered reading of
// /dev/urandom. It adds an overhead of a few KB of memory per thread. It must
// be called before the first call to |RAND_bytes| and it is mutually exclusive
// with calls to |RAND_set_urandom_fd|.
//
// If |fd| is non-negative then a copy of |fd| will be used rather than opening
// /dev/urandom internally. Like |RAND_set_urandom_fd|, the caller retains
// ownership of |fd|. If |fd| is negative then /dev/urandom will be opened and
// any error from open(2) crashes the address space.
//
// Setting this also enables thread-local PRNG state, which can reduce lock
// contention in highly-threaded applications although at the cost of yet more
// memory.
//
// It has an unusual name because the buffer is unsafe across calls to |fork|.
// Hence, this function should never be called by libraries.
OPENSSL_EXPORT void RAND_enable_fork_unsafe_buffering(int fd);
#endif

#if defined(BORINGSSL_UNSAFE_DETERMINISTIC_MODE)
// RAND_reset_for_fuzzing resets the fuzzer-only deterministic RNG. This
// function is only defined in the fuzzer-only build configuration.
OPENSSL_EXPORT void RAND_reset_for_fuzzing(void);
#endif


// Deprecated functions

// RAND_pseudo_bytes is a wrapper around |RAND_bytes|.
OPENSSL_EXPORT int RAND_pseudo_bytes(uint8_t *buf, size_t len);

// RAND_seed reads a single byte of random data to ensure that any file
// descriptors etc are opened.
OPENSSL_EXPORT void RAND_seed(const void *buf, int num);

// RAND_load_file returns a nonnegative number.
OPENSSL_EXPORT int RAND_load_file(const char *path, long num);

// RAND_file_name returns NULL.
OPENSSL_EXPORT const char *RAND_file_name(char *buf, size_t num);

// RAND_add does nothing.
OPENSSL_EXPORT void RAND_add(const void *buf, int num, double entropy);

// RAND_egd returns 255.
OPENSSL_EXPORT int RAND_egd(const char *);

// RAND_poll returns one.
OPENSSL_EXPORT int RAND_poll(void);

// RAND_status returns one.
OPENSSL_EXPORT int RAND_status(void);

// rand_meth_st is typedefed to |RAND_METHOD| in base.h. It isn't used; it
// exists only to be the return type of |RAND_SSLeay|. It's
// external so that variables of this type can be initialized.
struct rand_meth_st {
  void (*seed) (const void *buf, int num);
  int (*bytes) (uint8_t *buf, size_t num);
  void (*cleanup) (void);
  void (*add) (const void *buf, int num, double entropy);
  int (*pseudorand) (uint8_t *buf, size_t num);
  int (*status) (void);
};

// RAND_SSLeay returns a pointer to a dummy |RAND_METHOD|.
OPENSSL_EXPORT RAND_METHOD *RAND_SSLeay(void);

// RAND_get_rand_method returns |RAND_SSLeay()|.
OPENSSL_EXPORT const RAND_METHOD *RAND_get_rand_method(void);

// RAND_set_rand_method does nothing.
OPENSSL_EXPORT void RAND_set_rand_method(const RAND_METHOD *);


#if defined(__cplusplus)
}  // extern C
#endif

#endif  // OPENSSL_HEADER_RAND_H