boringssl/include/openssl/rand.h
David Benjamin bc5b2a2e22 Add a deterministic PRNG for fuzzing.
If running the stack through a fuzzer, we would like execution to be
completely deterministic. This is gated on a
BORINGSSL_UNSAFE_FUZZER_MODE #ifdef.

For now, this just uses the zero ChaCha20 key and a global counter. As
needed, we can extend this to a thread-local counter and a separate
ChaCha20 stream and counter per input length.

Change-Id: Ic6c9d8a25e70d68e5dc6804e2c234faf48e51395
Reviewed-on: https://boringssl-review.googlesource.com/7286
Reviewed-by: Adam Langley <agl@google.com>
2016-03-03 01:36:19 +00:00

123 lines
4.5 KiB
C

/* 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.
*
* 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_FUZZER_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_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 */