backends/rng-random.c

   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/qmp/qerror.h"
  17 #include "qemu/main-loop.h"
  18
  19 struct RndRandom
  20 {
  21     RngBackend parent;
  22
  23     int fd;
  24     char *filename;
  25
  26     EntropyReceiveFunc *receive_func;
  27     void *opaque;
  28     size_t size;
  29 };
  30
  31 /**
  32  * A simple and incomplete backend to request entropy from /dev/random.
  33  *
  34  * This backend exposes an additional "filename" property that can be used to
  35  * set the filename to use to open the backend.
  36  */
  37
  38 static void entropy_available(void *opaque)
  39 {
  40     RndRandom *s = RNG_RANDOM(opaque);
  41     uint8_t buffer[s->size];
  42     ssize_t len;
  43
  44     len = read(s->fd, buffer, s->size);
  45     if (len < 0 && errno == EAGAIN) {
  46         return;
  47     }
  48     g_assert(len != -1);
  49
  50     s->receive_func(s->opaque, buffer, len);
  51     s->receive_func = NULL;
  52
  53     qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
  54 }
  55
  56 static void rng_random_request_entropy(RngBackend *b, size_t size,
  57                                         EntropyReceiveFunc *receive_entropy,
  58                                         void *opaque)
  59 {
  60     RndRandom *s = RNG_RANDOM(b);
  61
  62     if (s->receive_func) {
  63         s->receive_func(s->opaque, NULL, 0);
  64     }
  65
  66     s->receive_func = receive_entropy;
  67     s->opaque = opaque;
  68     s->size = size;
  69
  70     qemu_set_fd_handler(s->fd, entropy_available, NULL, s);
  71 }
  72
  73 static void rng_random_opened(RngBackend *b, Error **errp)
  74 {
  75     RndRandom *s = RNG_RANDOM(b);
  76
  77     if (s->filename == NULL) {
  78         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
  79                    "filename", "a valid filename");
  80     } else {
  81         s->fd = qemu_open(s->filename, O_RDONLY | O_NONBLOCK);
  82         if (s->fd == -1) {
  83             error_setg_file_open(errp, errno, s->filename);
  84         }
  85     }
  86 }
  87
  88 static char *rng_random_get_filename(Object *obj, Error **errp)
  89 {
  90     RndRandom *s = RNG_RANDOM(obj);
  91
  92     return g_strdup(s->filename);
  93 }
  94
  95 static void rng_random_set_filename(Object *obj, const char *filename,
  96                                  Error **errp)
  97 {
  98     RngBackend *b = RNG_BACKEND(obj);
  99     RndRandom *s = RNG_RANDOM(obj);
 100
 101     if (b->opened) {
 102         error_setg(errp, QERR_PERMISSION_DENIED);
 103         return;
 104     }
 105
 106     g_free(s->filename);
 107     s->filename = g_strdup(filename);
 108 }
 109
 110 static void rng_random_init(Object *obj)
 111 {
 112     RndRandom *s = RNG_RANDOM(obj);
 113
 114     object_property_add_str(obj, "filename",
 115                             rng_random_get_filename,
 116                             rng_random_set_filename,
 117                             NULL);
 118
 119     s->filename = g_strdup("/dev/random");
 120     s->fd = -1;
 121 }
 122
 123 static void rng_random_finalize(Object *obj)
 124 {
 125     RndRandom *s = RNG_RANDOM(obj);
 126
 127     if (s->fd != -1) {
 128         qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
 129         qemu_close(s->fd);
 130     }
 131
 132     g_free(s->filename);
 133 }
 134
 135 static void rng_random_class_init(ObjectClass *klass, void *data)
 136 {
 137     RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
 138
 139     rbc->request_entropy = rng_random_request_entropy;
 140     rbc->opened = rng_random_opened;
 141 }
 142
 143 static const TypeInfo rng_random_info = {
 144     .name = TYPE_RNG_RANDOM,
 145     .parent = TYPE_RNG_BACKEND,
 146     .instance_size = sizeof(RndRandom),
 147     .class_init = rng_random_class_init,
 148     .instance_init = rng_random_init,
 149     .instance_finalize = rng_random_finalize,
 150 };
 151
 152 static void register_types(void)
 153 {
 154     type_register_static(&rng_random_info);
 155 }
 156
 157 type_init(register_types);