1 | /* |
2 | * Copyright 2010-2018 Amazon.com, Inc. or its affiliates. All Rights Reserved. |
3 | * |
4 | * Licensed under the Apache License, Version 2.0 (the "License"). |
5 | * You may not use this file except in compliance with the License. |
6 | * A copy of the License is located at |
7 | * |
8 | * http://aws.amazon.com/apache2.0 |
9 | * |
10 | * or in the "license" file accompanying this file. This file is distributed |
11 | * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either |
12 | * express or implied. See the License for the specific language governing |
13 | * permissions and limitations under the License. |
14 | */ |
15 | #include <aws/common/device_random.h> |
16 | |
17 | #include <aws/common/byte_buf.h> |
18 | #include <aws/common/thread.h> |
19 | |
20 | #include <fcntl.h> |
21 | #include <unistd.h> |
22 | |
23 | static int s_rand_fd = -1; |
24 | static aws_thread_once s_rand_init = AWS_THREAD_ONCE_STATIC_INIT; |
25 | |
26 | #ifdef O_CLOEXEC |
27 | # define OPEN_FLAGS (O_RDONLY | O_CLOEXEC) |
28 | #else |
29 | # define OPEN_FLAGS (O_RDONLY) |
30 | #endif |
31 | static void s_init_rand(void *user_data) { |
32 | (void)user_data; |
33 | s_rand_fd = open("/dev/urandom" , OPEN_FLAGS); |
34 | |
35 | if (s_rand_fd == -1) { |
36 | s_rand_fd = open("/dev/urandom" , O_RDONLY); |
37 | |
38 | if (s_rand_fd == -1) { |
39 | abort(); |
40 | } |
41 | } |
42 | |
43 | if (-1 == fcntl(s_rand_fd, F_SETFD, FD_CLOEXEC)) { |
44 | abort(); |
45 | } |
46 | } |
47 | |
48 | static int s_fallback_device_random_buffer(struct aws_byte_buf *output) { |
49 | |
50 | aws_thread_call_once(&s_rand_init, s_init_rand, NULL); |
51 | |
52 | size_t diff = output->capacity - output->len; |
53 | |
54 | ssize_t amount_read = read(s_rand_fd, output->buffer + output->len, diff); |
55 | |
56 | if (amount_read != diff) { |
57 | return aws_raise_error(AWS_ERROR_RANDOM_GEN_FAILED); |
58 | } |
59 | |
60 | output->len += diff; |
61 | |
62 | return AWS_OP_SUCCESS; |
63 | } |
64 | |
65 | int aws_device_random_buffer(struct aws_byte_buf *output) { |
66 | return s_fallback_device_random_buffer(output); |
67 | } |
68 | |