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 20 struct RngRandom 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 35 static void entropy_available(void *opaque) 36 { 37 RngRandom *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 58 static void rng_random_request_entropy(RngBackend *b, RngRequest *req) 59 { 60 RngRandom *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 69 static void rng_random_opened(RngBackend *b, Error **errp) 70 { 71 RngRandom *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 84 static char *rng_random_get_filename(Object *obj, Error **errp) 85 { 86 RngRandom *s = RNG_RANDOM(obj); 87 88 return g_strdup(s->filename); 89 } 90 91 static void rng_random_set_filename(Object *obj, const char *filename, 92 Error **errp) 93 { 94 RngBackend *b = RNG_BACKEND(obj); 95 RngRandom *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 } 105 106 static void rng_random_init(Object *obj) 107 { 108 RngRandom *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 } 118 119 static void rng_random_finalize(Object *obj) 120 { 121 RngRandom *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 } 130 131 static 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 } 138 139 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); 154