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