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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 <windows.h>
#include <bcrypt.h>
static BCRYPT_ALG_HANDLE s_alg_handle = NULL;
static aws_thread_once s_rand_init = AWS_THREAD_ONCE_STATIC_INIT;
static void s_init_rand(void *user_data) {
(void)user_data;
NTSTATUS status = 0;
status = BCryptOpenAlgorithmProvider(&s_alg_handle, BCRYPT_RNG_ALGORITHM, NULL, 0);
if (!BCRYPT_SUCCESS(status)) {
abort();
}
}
int aws_device_random_buffer(struct aws_byte_buf *output) {
return aws_device_random_buffer_append(output, output->capacity - output->len);
}
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;
/* BCryptGenRandom() takes 32bit length, but we accept size_t,
* so work in chunks if necessary. */
while (n > 0) {
uint32_t capped_n = (uint32_t)aws_min_size(n, UINT32_MAX);
NTSTATUS status = BCryptGenRandom(s_alg_handle, output->buffer + output->len, capped_n, 0 /*flags*/);
if (!BCRYPT_SUCCESS(status)) {
output->len = original_len;
AWS_POSTCONDITION(aws_byte_buf_is_valid(output));
return aws_raise_error(AWS_ERROR_RANDOM_GEN_FAILED);
}
output->len += capped_n;
n -= capped_n;
}
AWS_POSTCONDITION(aws_byte_buf_is_valid(output));
return AWS_OP_SUCCESS;
}
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