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1 | /* | |
2 | * QEMU Random Number Generator Backend | |
3 | * | |
4 | * Copyright IBM, Corp. 2012 | |
5 | * | |
6 | * Authors: | |
7 | * Anthony Liguori <aliguori@us.ibm.com> | |
8 | * | |
9 | * This work is licensed under the terms of the GNU GPL, version 2 or later. | |
10 | * See the COPYING file in the top-level directory. | |
11 | */ | |
12 | ||
13 | #include "qemu/osdep.h" | |
14 | #include "sysemu/rng-random.h" | |
15 | #include "sysemu/rng.h" | |
16 | #include "qapi/error.h" | |
17 | #include "qapi/qmp/qerror.h" | |
18 | #include "qemu/main-loop.h" | |
19 | #include "qemu/module.h" | |
20 | ||
21 | struct RngRandom | |
22 | { | |
23 | RngBackend parent; | |
24 | ||
25 | int fd; | |
26 | char *filename; | |
27 | }; | |
28 | ||
29 | /** | |
30 | * A simple and incomplete backend to request entropy from /dev/random. | |
31 | * | |
32 | * This backend exposes an additional "filename" property that can be used to | |
33 | * set the filename to use to open the backend. | |
34 | */ | |
35 | ||
36 | static void entropy_available(void *opaque) | |
37 | { | |
38 | RngRandom *s = RNG_RANDOM(opaque); | |
39 | ||
40 | while (!QSIMPLEQ_EMPTY(&s->parent.requests)) { | |
41 | RngRequest *req = QSIMPLEQ_FIRST(&s->parent.requests); | |
42 | ssize_t len; | |
43 | ||
44 | len = read(s->fd, req->data, req->size); | |
45 | if (len < 0 && errno == EAGAIN) { | |
46 | return; | |
47 | } | |
48 | g_assert(len != -1); | |
49 | ||
50 | req->receive_entropy(req->opaque, req->data, len); | |
51 | ||
52 | rng_backend_finalize_request(&s->parent, req); | |
53 | } | |
54 | ||
55 | /* We've drained all requests, the fd handler can be reset. */ | |
56 | qemu_set_fd_handler(s->fd, NULL, NULL, NULL); | |
57 | } | |
58 | ||
59 | static void rng_random_request_entropy(RngBackend *b, RngRequest *req) | |
60 | { | |
61 | RngRandom *s = RNG_RANDOM(b); | |
62 | ||
63 | if (QSIMPLEQ_EMPTY(&s->parent.requests)) { | |
64 | /* If there are no pending requests yet, we need to | |
65 | * install our fd handler. */ | |
66 | qemu_set_fd_handler(s->fd, entropy_available, NULL, s); | |
67 | } | |
68 | } | |
69 | ||
70 | static void rng_random_opened(RngBackend *b, Error **errp) | |
71 | { | |
72 | RngRandom *s = RNG_RANDOM(b); | |
73 | ||
74 | if (s->filename == NULL) { | |
75 | error_setg(errp, QERR_INVALID_PARAMETER_VALUE, | |
76 | "filename", "a valid filename"); | |
77 | } else { | |
78 | s->fd = qemu_open_old(s->filename, O_RDONLY | O_NONBLOCK); | |
79 | if (s->fd == -1) { | |
80 | error_setg_file_open(errp, errno, s->filename); | |
81 | } | |
82 | } | |
83 | } | |
84 | ||
85 | static char *rng_random_get_filename(Object *obj, Error **errp) | |
86 | { | |
87 | RngRandom *s = RNG_RANDOM(obj); | |
88 | ||
89 | return g_strdup(s->filename); | |
90 | } | |
91 | ||
92 | static void rng_random_set_filename(Object *obj, const char *filename, | |
93 | Error **errp) | |
94 | { | |
95 | RngBackend *b = RNG_BACKEND(obj); | |
96 | RngRandom *s = RNG_RANDOM(obj); | |
97 | ||
98 | if (b->opened) { | |
99 | error_setg(errp, "Property 'filename' can no longer be set"); | |
100 | return; | |
101 | } | |
102 | ||
103 | g_free(s->filename); | |
104 | s->filename = g_strdup(filename); | |
105 | } | |
106 | ||
107 | static void rng_random_init(Object *obj) | |
108 | { | |
109 | RngRandom *s = RNG_RANDOM(obj); | |
110 | ||
111 | s->filename = g_strdup("/dev/urandom"); | |
112 | s->fd = -1; | |
113 | } | |
114 | ||
115 | static void rng_random_finalize(Object *obj) | |
116 | { | |
117 | RngRandom *s = RNG_RANDOM(obj); | |
118 | ||
119 | if (s->fd != -1) { | |
120 | qemu_set_fd_handler(s->fd, NULL, NULL, NULL); | |
121 | qemu_close(s->fd); | |
122 | } | |
123 | ||
124 | g_free(s->filename); | |
125 | } | |
126 | ||
127 | static void rng_random_class_init(ObjectClass *klass, void *data) | |
128 | { | |
129 | RngBackendClass *rbc = RNG_BACKEND_CLASS(klass); | |
130 | ||
131 | rbc->request_entropy = rng_random_request_entropy; | |
132 | rbc->opened = rng_random_opened; | |
133 | object_class_property_add_str(klass, "filename", | |
134 | rng_random_get_filename, | |
135 | rng_random_set_filename); | |
136 | ||
137 | } | |
138 | ||
139 | static const TypeInfo rng_random_info = { | |
140 | .name = TYPE_RNG_RANDOM, | |
141 | .parent = TYPE_RNG_BACKEND, | |
142 | .instance_size = sizeof(RngRandom), | |
143 | .class_init = rng_random_class_init, | |
144 | .instance_init = rng_random_init, | |
145 | .instance_finalize = rng_random_finalize, | |
146 | }; | |
147 | ||
148 | static void register_types(void) | |
149 | { | |
150 | type_register_static(&rng_random_info); | |
151 | } | |
152 | ||
153 | type_init(register_types); |