LXR qemu/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/error.h"
  17#include "qapi/qmp/qerror.h"
  18#include "qemu/main-loop.h"
  19
  20struct RndRandom
  21{
  22    RngBackend parent;
  23
  24    int fd;
  25    char *filename;
  26};
  27
  28/**
  29 * A simple and incomplete backend to request entropy from /dev/random.
  30 *
  31 * This backend exposes an additional "filename" property that can be used to
  32 * set the filename to use to open the backend.
  33 */
  34
  35static void entropy_available(void *opaque)
  36{
  37    RndRandom *s = RNG_RANDOM(opaque);
  38
  39    while (!QSIMPLEQ_EMPTY(&s->parent.requests)) {
  40        RngRequest *req = QSIMPLEQ_FIRST(&s->parent.requests);
  41        ssize_t len;
  42
  43        len = read(s->fd, req->data, req->size);
  44        if (len < 0 && errno == EAGAIN) {
  45            return;
  46        }
  47        g_assert(len != -1);
  48
  49        req->receive_entropy(req->opaque, req->data, len);
  50
  51        rng_backend_finalize_request(&s->parent, req);
  52    }
  53
  54    /* We've drained all requests, the fd handler can be reset. */
  55    qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
  56}
  57
  58static void rng_random_request_entropy(RngBackend *b, RngRequest *req)
  59{
  60    RndRandom *s = RNG_RANDOM(b);
  61
  62    if (QSIMPLEQ_EMPTY(&s->parent.requests)) {
  63        /* If there are no pending requests yet, we need to
  64         * install our fd handler. */
  65        qemu_set_fd_handler(s->fd, entropy_available, NULL, s);
  66    }
  67}
  68
  69static void rng_random_opened(RngBackend *b, Error **errp)
  70{
  71    RndRandom *s = RNG_RANDOM(b);
  72
  73    if (s->filename == NULL) {
  74        error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
  75                   "filename", "a valid filename");
  76    } else {
  77        s->fd = qemu_open(s->filename, O_RDONLY | O_NONBLOCK);
  78        if (s->fd == -1) {
  79            error_setg_file_open(errp, errno, s->filename);
  80        }
  81    }
  82}
  83
  84static char *rng_random_get_filename(Object *obj, Error **errp)
  85{
  86    RndRandom *s = RNG_RANDOM(obj);
  87
  88    return g_strdup(s->filename);
  89}
  90
  91static void rng_random_set_filename(Object *obj, const char *filename,
  92                                 Error **errp)
  93{
  94    RngBackend *b = RNG_BACKEND(obj);
  95    RndRandom *s = RNG_RANDOM(obj);
  96
  97    if (b->opened) {
  98        error_setg(errp, QERR_PERMISSION_DENIED);
  99        return;
 100    }
 101
 102    g_free(s->filename);
 103    s->filename = g_strdup(filename);
 104}
 105
 106static void rng_random_init(Object *obj)
 107{
 108    RndRandom *s = RNG_RANDOM(obj);
 109
 110    object_property_add_str(obj, "filename",
 111                            rng_random_get_filename,
 112                            rng_random_set_filename,
 113                            NULL);
 114
 115    s->filename = g_strdup("/dev/random");
 116    s->fd = -1;
 117}
 118
 119static void rng_random_finalize(Object *obj)
 120{
 121    RndRandom *s = RNG_RANDOM(obj);
 122
 123    if (s->fd != -1) {
 124        qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
 125        qemu_close(s->fd);
 126    }
 127
 128    g_free(s->filename);
 129}
 130
 131static void rng_random_class_init(ObjectClass *klass, void *data)
 132{
 133    RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
 134
 135    rbc->request_entropy = rng_random_request_entropy;
 136    rbc->opened = rng_random_opened;
 137}
 138
 139static const TypeInfo rng_random_info = {
 140    .name = TYPE_RNG_RANDOM,
 141    .parent = TYPE_RNG_BACKEND,
 142    .instance_size = sizeof(RndRandom),
 143    .class_init = rng_random_class_init,
 144    .instance_init = rng_random_init,
 145    .instance_finalize = rng_random_finalize,
 146};
 147
 148static void register_types(void)
 149{
 150    type_register_static(&rng_random_info);
 151}
 152
 153type_init(register_types);
 154