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/rng-random.h"
  14 #include "qemu/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     g_assert(len != -1);
  45
  46     s->receive_func(s->opaque, buffer, len);
  47     s->receive_func = NULL;
  48
  49     qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
  50 }
  51
  52 static void rng_random_request_entropy(RngBackend *b, size_t size,
  53                                         EntropyReceiveFunc *receive_entropy,
  54                                         void *opaque)
  55 {
  56     RndRandom *s = RNG_RANDOM(b);
  57
  58     if (s->receive_func) {
  59         s->receive_func(s->opaque, NULL, 0);
  60     }
  61
  62     s->receive_func = receive_entropy;
  63     s->opaque = opaque;
  64     s->size = size;
  65
  66     qemu_set_fd_handler(s->fd, entropy_available, NULL, s);
  67 }
  68
  69 static void rng_random_opened(RngBackend *b, Error **errp)
  70 {
  71     RndRandom *s = RNG_RANDOM(b);
  72
  73     if (s->filename == NULL) {
  74         error_set(errp, QERR_INVALID_PARAMETER_VALUE,
  75                   "filename", "a valid filename");
  76     } else {
  77         s->fd = open(s->filename, O_RDONLY | O_NONBLOCK);
  78
  79         if (s->fd == -1) {
  80             error_set(errp, QERR_OPEN_FILE_FAILED, s->filename);
  81         }
  82     }
  83 }
  84
  85 static char *rng_random_get_filename(Object *obj, Error **errp)
  86 {
  87     RndRandom *s = RNG_RANDOM(obj);
  88
  89     if (s->filename) {
  90         return g_strdup(s->filename);
  91     }
  92
  93     return NULL;
  94 }
  95
  96 static void rng_random_set_filename(Object *obj, const char *filename,
  97                                  Error **errp)
  98 {
  99     RngBackend *b = RNG_BACKEND(obj);
 100     RndRandom *s = RNG_RANDOM(obj);
 101
 102     if (b->opened) {
 103         error_set(errp, QERR_PERMISSION_DENIED);
 104         return;
 105     }
 106
 107     if (s->filename) {
 108         g_free(s->filename);
 109     }
 110
 111     s->filename = g_strdup(filename);
 112 }
 113
 114 static void rng_random_init(Object *obj)
 115 {
 116     RndRandom *s = RNG_RANDOM(obj);
 117
 118     object_property_add_str(obj, "filename",
 119                             rng_random_get_filename,
 120                             rng_random_set_filename,
 121                             NULL);
 122
 123     s->filename = g_strdup("/dev/random");
 124 }
 125
 126 static void rng_random_finalize(Object *obj)
 127 {
 128     RndRandom *s = RNG_RANDOM(obj);
 129
 130     qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
 131
 132     if (s->fd != -1) {
 133         close(s->fd);
 134     }
 135
 136     g_free(s->filename);
 137 }
 138
 139 static void rng_random_class_init(ObjectClass *klass, void *data)
 140 {
 141     RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
 142
 143     rbc->request_entropy = rng_random_request_entropy;
 144     rbc->opened = rng_random_opened;
 145 }
 146
 147 static const TypeInfo rng_random_info = {
 148     .name = TYPE_RNG_RANDOM,
 149     .parent = TYPE_RNG_BACKEND,
 150     .instance_size = sizeof(RndRandom),
 151     .class_init = rng_random_class_init,
 152     .instance_init = rng_random_init,
 153     .instance_finalize = rng_random_finalize,
 154 };
 155
 156 static void register_types(void)
 157 {
 158     type_register_static(&rng_random_info);
 159 }
 160
 161 type_init(register_types);