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
entropy_available(void * opaque)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
rng_random_request_entropy(RngBackend * b,RngRequest * req)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
rng_random_opened(RngBackend * b,Error ** errp)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(s->filename, O_RDONLY | O_NONBLOCK, errp);
79 }
80 }
81
rng_random_get_filename(Object * obj,Error ** errp)82 static char *rng_random_get_filename(Object *obj, Error **errp)
83 {
84 RngRandom *s = RNG_RANDOM(obj);
85
86 return g_strdup(s->filename);
87 }
88
rng_random_set_filename(Object * obj,const char * filename,Error ** errp)89 static void rng_random_set_filename(Object *obj, const char *filename,
90 Error **errp)
91 {
92 RngBackend *b = RNG_BACKEND(obj);
93 RngRandom *s = RNG_RANDOM(obj);
94
95 if (b->opened) {
96 error_setg(errp, "Property 'filename' can no longer be set");
97 return;
98 }
99
100 g_free(s->filename);
101 s->filename = g_strdup(filename);
102 }
103
rng_random_init(Object * obj)104 static void rng_random_init(Object *obj)
105 {
106 RngRandom *s = RNG_RANDOM(obj);
107
108 s->filename = g_strdup("/dev/urandom");
109 s->fd = -1;
110 }
111
rng_random_finalize(Object * obj)112 static void rng_random_finalize(Object *obj)
113 {
114 RngRandom *s = RNG_RANDOM(obj);
115
116 if (s->fd != -1) {
117 qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
118 qemu_close(s->fd);
119 }
120
121 g_free(s->filename);
122 }
123
rng_random_class_init(ObjectClass * klass,void * data)124 static void rng_random_class_init(ObjectClass *klass, void *data)
125 {
126 RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
127
128 rbc->request_entropy = rng_random_request_entropy;
129 rbc->opened = rng_random_opened;
130 object_class_property_add_str(klass, "filename",
131 rng_random_get_filename,
132 rng_random_set_filename);
133
134 }
135
136 static const TypeInfo rng_random_info = {
137 .name = TYPE_RNG_RANDOM,
138 .parent = TYPE_RNG_BACKEND,
139 .instance_size = sizeof(RngRandom),
140 .class_init = rng_random_class_init,
141 .instance_init = rng_random_init,
142 .instance_finalize = rng_random_finalize,
143 };
144
register_types(void)145 static void register_types(void)
146 {
147 type_register_static(&rng_random_info);
148 }
149
150 type_init(register_types);
151