qemu

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rng-random.c (3759B)

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