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