backends/rng-egd.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.h"
  15 #include "chardev/char-fe.h"
  16 #include "qapi/error.h"
  17 #include "qapi/qmp/qerror.h"
  18 #include "qemu/module.h"
  19 #include "qom/object.h"
  20
  21 #define TYPE_RNG_EGD "rng-egd"
  22 typedef struct RngEgd RngEgd;
  23 DECLARE_INSTANCE_CHECKER(RngEgd, RNG_EGD,
  24                          TYPE_RNG_EGD)
  25
  26 struct RngEgd {
  27     RngBackend parent;
  28
  29     CharBackend chr;
  30     char *chr_name;
  31 };
  32
  33 static void rng_egd_request_entropy(RngBackend *b, RngRequest *req)
  34 {
  35     RngEgd *s = RNG_EGD(b);
  36     size_t size = req->size;
  37
  38     while (size > 0) {
  39         uint8_t header[2];
  40         uint8_t len = MIN(size, 255);
  41
  42         /* synchronous entropy request */
  43         header[0] = 0x02;
  44         header[1] = len;
  45
  46         /* XXX this blocks entire thread. Rewrite to use
  47          * qemu_chr_fe_write and background I/O callbacks */
  48         qemu_chr_fe_write_all(&s->chr, header, sizeof(header));
  49
  50         size -= len;
  51     }
  52 }
  53
  54 static int rng_egd_chr_can_read(void *opaque)
  55 {
  56     RngEgd *s = RNG_EGD(opaque);
  57     RngRequest *req;
  58     int size = 0;
  59
  60     QSIMPLEQ_FOREACH(req, &s->parent.requests, next) {
  61         size += req->size - req->offset;
  62     }
  63
  64     return size;
  65 }
  66
  67 static void rng_egd_chr_read(void *opaque, const uint8_t *buf, int size)
  68 {
  69     RngEgd *s = RNG_EGD(opaque);
  70     size_t buf_offset = 0;
  71
  72     while (size > 0 && !QSIMPLEQ_EMPTY(&s->parent.requests)) {
  73         RngRequest *req = QSIMPLEQ_FIRST(&s->parent.requests);
  74         int len = MIN(size, req->size - req->offset);
  75
  76         memcpy(req->data + req->offset, buf + buf_offset, len);
  77         buf_offset += len;
  78         req->offset += len;
  79         size -= len;
  80
  81         if (req->offset == req->size) {
  82             req->receive_entropy(req->opaque, req->data, req->size);
  83
  84             rng_backend_finalize_request(&s->parent, req);
  85         }
  86     }
  87 }
  88
  89 static void rng_egd_opened(RngBackend *b, Error **errp)
  90 {
  91     RngEgd *s = RNG_EGD(b);
  92     Chardev *chr;
  93
  94     if (s->chr_name == NULL) {
  95         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
  96                    "chardev", "a valid character device");
  97         return;
  98     }
  99
 100     chr = qemu_chr_find(s->chr_name);
 101     if (chr == NULL) {
 102         error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
 103                   "Device '%s' not found", s->chr_name);
 104         return;
 105     }
 106     if (!qemu_chr_fe_init(&s->chr, chr, errp)) {
 107         return;
 108     }
 109
 110     /* FIXME we should resubmit pending requests when the CDS reconnects. */
 111     qemu_chr_fe_set_handlers(&s->chr, rng_egd_chr_can_read,
 112                              rng_egd_chr_read, NULL, NULL, s, NULL, true);
 113 }
 114
 115 static void rng_egd_set_chardev(Object *obj, const char *value, Error **errp)
 116 {
 117     RngBackend *b = RNG_BACKEND(obj);
 118     RngEgd *s = RNG_EGD(b);
 119
 120     if (b->opened) {
 121         error_setg(errp, QERR_PERMISSION_DENIED);
 122     } else {
 123         g_free(s->chr_name);
 124         s->chr_name = g_strdup(value);
 125     }
 126 }
 127
 128 static char *rng_egd_get_chardev(Object *obj, Error **errp)
 129 {
 130     RngEgd *s = RNG_EGD(obj);
 131     Chardev *chr = qemu_chr_fe_get_driver(&s->chr);
 132
 133     if (chr && chr->label) {
 134         return g_strdup(chr->label);
 135     }
 136
 137     return NULL;
 138 }
 139
 140 static void rng_egd_init(Object *obj)
 141 {
 142     object_property_add_str(obj, "chardev",
 143                             rng_egd_get_chardev, rng_egd_set_chardev);
 144 }
 145
 146 static void rng_egd_finalize(Object *obj)
 147 {
 148     RngEgd *s = RNG_EGD(obj);
 149
 150     qemu_chr_fe_deinit(&s->chr, false);
 151     g_free(s->chr_name);
 152 }
 153
 154 static void rng_egd_class_init(ObjectClass *klass, void *data)
 155 {
 156     RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
 157
 158     rbc->request_entropy = rng_egd_request_entropy;
 159     rbc->opened = rng_egd_opened;
 160 }
 161
 162 static const TypeInfo rng_egd_info = {
 163     .name = TYPE_RNG_EGD,
 164     .parent = TYPE_RNG_BACKEND,
 165     .instance_size = sizeof(RngEgd),
 166     .class_init = rng_egd_class_init,
 167     .instance_init = rng_egd_init,
 168     .instance_finalize = rng_egd_finalize,
 169 };
 170
 171 static void register_types(void)
 172 {
 173     type_register_static(&rng_egd_info);
 174 }
 175
 176 type_init(register_types);