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/**
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
* SPDX-License-Identifier: Apache-2.0.
*/
#include <aws/common/device_random.h>
#include <aws/common/byte_buf.h>
#include <aws/common/thread.h>
#include <fcntl.h>
#include <unistd.h>
static int s_rand_fd = -1;
static aws_thread_once s_rand_init = AWS_THREAD_ONCE_STATIC_INIT;
#ifdef O_CLOEXEC
# define OPEN_FLAGS (O_RDONLY | O_CLOEXEC)
#else
# define OPEN_FLAGS (O_RDONLY)
#endif
static void s_init_rand(void *user_data) {
(void)user_data;
s_rand_fd = open("/dev/urandom", OPEN_FLAGS);
if (s_rand_fd == -1) {
s_rand_fd = open("/dev/urandom", O_RDONLY);
if (s_rand_fd == -1) {
abort();
}
}
if (-1 == fcntl(s_rand_fd, F_SETFD, FD_CLOEXEC)) {
abort();
}
}
int aws_device_random_buffer_append(struct aws_byte_buf *output, size_t n) {
AWS_PRECONDITION(aws_byte_buf_is_valid(output));
aws_thread_call_once(&s_rand_init, s_init_rand, NULL);
size_t space_available = output->capacity - output->len;
if (space_available < n) {
AWS_POSTCONDITION(aws_byte_buf_is_valid(output));
return aws_raise_error(AWS_ERROR_SHORT_BUFFER);
}
size_t original_len = output->len;
/* read() can fail if N is too large (e.g. x64 macos fails if N > INT32_MAX),
* so work in reasonably sized chunks. */
while (n > 0) {
size_t capped_n = aws_min_size(n, 1024 * 1024 * 1024 * 1 /* 1GiB */);
ssize_t amount_read = read(s_rand_fd, output->buffer + output->len, capped_n);
if (amount_read <= 0) {
output->len = original_len;
AWS_POSTCONDITION(aws_byte_buf_is_valid(output));
return aws_raise_error(AWS_ERROR_RANDOM_GEN_FAILED);
}
output->len += amount_read;
n -= amount_read;
}
AWS_POSTCONDITION(aws_byte_buf_is_valid(output));
return AWS_OP_SUCCESS;
}
int aws_device_random_buffer(struct aws_byte_buf *output) {
return aws_device_random_buffer_append(output, output->capacity - output->len);
}
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