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// Copyright 2014 The BoringSSL Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#if !defined(_GNU_SOURCE)
#define _GNU_SOURCE // needed for syscall() on Linux.
#endif
#include <contrib/restricted/google/boringssl/include/openssl/rand.h>
#include "../bcm_support.h"
#include "internal.h"
#if defined(OPENSSL_RAND_URANDOM)
#include <errno.h>
#include <fcntl.h>
#include <linux/random.h>
#include <stdio.h>
#include <sys/syscall.h>
#include <unistd.h>
#include "../internal.h"
using namespace bssl;
#if defined(OPENSSL_MSAN)
extern "C" {
void __msan_unpoison(void *, size_t);
}
#endif
static ssize_t boringssl_getrandom(void *buf, size_t buf_len, unsigned flags) {
ssize_t ret;
do {
ret = syscall(__NR_getrandom, buf, buf_len, flags);
} while (ret == -1 && errno == EINTR);
#if defined(OPENSSL_MSAN)
if (ret > 0) {
// MSAN doesn't recognise |syscall| and thus doesn't notice that we have
// initialised the output buffer.
__msan_unpoison(buf, ret);
}
#endif // OPENSSL_MSAN
return ret;
}
// kHaveGetrandom in |urandom_fd| signals that |getrandom| or |getentropy| is
// available and should be used instead.
static const int kHaveGetrandom = -3;
// urandom_fd is a file descriptor to /dev/urandom. It's protected by |once|.
static int urandom_fd;
static CRYPTO_once_t rand_once = CRYPTO_ONCE_INIT;
// init_once initializes the state of this module to values previously
// requested. This is the only function that modifies |urandom_fd|, which may be
// read safely after calling the once.
static void init_once() {
int have_getrandom;
uint8_t dummy;
ssize_t getrandom_ret =
boringssl_getrandom(&dummy, sizeof(dummy), GRND_NONBLOCK);
if (getrandom_ret == 1) {
have_getrandom = 1;
} else if (getrandom_ret == -1 && errno == EAGAIN) {
// We have getrandom, but the entropy pool has not been initialized yet.
have_getrandom = 1;
} else if (getrandom_ret == -1 && errno == ENOSYS) {
// Fallthrough to using /dev/urandom, below.
have_getrandom = 0;
} else {
// Other errors are fatal.
perror("getrandom");
abort();
}
if (have_getrandom) {
urandom_fd = kHaveGetrandom;
return;
}
// FIPS builds must support getrandom.
#if defined(BORINGSSL_FIPS)
perror("getrandom not found");
abort();
#endif
int fd;
do {
fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
} while (fd == -1 && errno == EINTR);
if (fd < 0) {
perror("failed to open /dev/urandom");
abort();
}
urandom_fd = fd;
}
void bssl::CRYPTO_init_sysrand() { CRYPTO_once(&rand_once, init_once); }
// CRYPTO_sysrand writes |len| bytes of entropy into |out|.
void bssl::CRYPTO_sysrand(uint8_t *out, size_t len) {
if (len == 0) {
return;
}
CRYPTO_init_sysrand();
// Clear |errno| so it has defined value if |read| or |getrandom|
// "successfully" returns zero.
errno = 0;
while (len > 0) {
ssize_t r;
if (urandom_fd == kHaveGetrandom) {
r = boringssl_getrandom(out, len, 0);
} else {
do {
r = read(urandom_fd, out, len);
} while (r == -1 && errno == EINTR);
}
if (r <= 0) {
perror("entropy fill failed");
abort();
}
out += r;
len -= r;
}
}
#endif // OPENSSL_RAND_URANDOM
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