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); 154