aboutsummaryrefslogtreecommitdiff
path: root/backends/rng-random.c
blob: d479ce8c56a444ec46835075161562df25c669f7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
/*
 * QEMU Random Number Generator Backend
 *
 * Copyright IBM, Corp. 2012
 *
 * Authors:
 *  Anthony Liguori   <aliguori@us.ibm.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 */

#include "qemu/rng-random.h"
#include "qemu/rng.h"
#include "qapi/qmp/qerror.h"
#include "qemu/main-loop.h"

struct RndRandom
{
    RngBackend parent;

    int fd;
    char *filename;

    EntropyReceiveFunc *receive_func;
    void *opaque;
    size_t size;
};

/**
 * A simple and incomplete backend to request entropy from /dev/random.
 *
 * This backend exposes an additional "filename" property that can be used to
 * set the filename to use to open the backend.
 */

static void entropy_available(void *opaque)
{
    RndRandom *s = RNG_RANDOM(opaque);
    uint8_t buffer[s->size];
    ssize_t len;

    len = read(s->fd, buffer, s->size);
    g_assert(len != -1);

    s->receive_func(s->opaque, buffer, len);
    s->receive_func = NULL;

    qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
}

static void rng_random_request_entropy(RngBackend *b, size_t size,
                                        EntropyReceiveFunc *receive_entropy,
                                        void *opaque)
{
    RndRandom *s = RNG_RANDOM(b);

    if (s->receive_func) {
        s->receive_func(s->opaque, NULL, 0);
    }

    s->receive_func = receive_entropy;
    s->opaque = opaque;
    s->size = size;

    qemu_set_fd_handler(s->fd, entropy_available, NULL, s);
}

static void rng_random_opened(RngBackend *b, Error **errp)
{
    RndRandom *s = RNG_RANDOM(b);

    if (s->filename == NULL) {
        error_set(errp, QERR_INVALID_PARAMETER_VALUE,
                  "filename", "a valid filename");
    } else {
        s->fd = open(s->filename, O_RDONLY | O_NONBLOCK);

        if (s->fd == -1) {
            error_set(errp, QERR_OPEN_FILE_FAILED, s->filename);
        }
    }
}

static char *rng_random_get_filename(Object *obj, Error **errp)
{
    RndRandom *s = RNG_RANDOM(obj);

    if (s->filename) {
        return g_strdup(s->filename);
    }

    return NULL;
}

static void rng_random_set_filename(Object *obj, const char *filename,
                                 Error **errp)
{
    RngBackend *b = RNG_BACKEND(obj);
    RndRandom *s = RNG_RANDOM(obj);

    if (b->opened) {
        error_set(errp, QERR_PERMISSION_DENIED);
        return;
    }

    if (s->filename) {
        g_free(s->filename);
    }

    s->filename = g_strdup(filename);
}

static void rng_random_init(Object *obj)
{
    RndRandom *s = RNG_RANDOM(obj);

    object_property_add_str(obj, "filename",
                            rng_random_get_filename,
                            rng_random_set_filename,
                            NULL);

    s->filename = g_strdup("/dev/random");
}

static void rng_random_finalize(Object *obj)
{
    RndRandom *s = RNG_RANDOM(obj);

    qemu_set_fd_handler(s->fd, NULL, NULL, NULL);

    if (s->fd != -1) {
        close(s->fd);
    }

    g_free(s->filename);
}

static void rng_random_class_init(ObjectClass *klass, void *data)
{
    RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);

    rbc->request_entropy = rng_random_request_entropy;
    rbc->opened = rng_random_opened;
}

static TypeInfo rng_random_info = {
    .name = TYPE_RNG_RANDOM,
    .parent = TYPE_RNG_BACKEND,
    .instance_size = sizeof(RndRandom),
    .class_init = rng_random_class_init,
    .instance_init = rng_random_init,
    .instance_finalize = rng_random_finalize,
};

static void register_types(void)
{
    type_register_static(&rng_random_info);
}

type_init(register_types);