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