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/rng-random.h" 14 #include "qemu/rng.h" 15 #include "qapi/qmp/qerror.h" 16 #include "qemu/main-loop.h" 17 18 struct RndRandom 19 { 20 RngBackend parent; 21 22 int fd; 23 char *filename; 24 25 EntropyReceiveFunc *receive_func; 26 void *opaque; 27 size_t size; 28 }; 29 30 /** 31 * A simple and incomplete backend to request entropy from /dev/random. 32 * 33 * This backend exposes an additional "filename" property that can be used to 34 * set the filename to use to open the backend. 35 */ 36 37 static void entropy_available(void *opaque) 38 { 39 RndRandom *s = RNG_RANDOM(opaque); 40 uint8_t buffer[s->size]; 41 ssize_t len; 42 43 len = read(s->fd, buffer, s->size); 44 g_assert(len != -1); 45 46 s->receive_func(s->opaque, buffer, len); 47 s->receive_func = NULL; 48 49 qemu_set_fd_handler(s->fd, NULL, NULL, NULL); 50 } 51 52 static void rng_random_request_entropy(RngBackend *b, size_t size, 53 EntropyReceiveFunc *receive_entropy, 54 void *opaque) 55 { 56 RndRandom *s = RNG_RANDOM(b); 57 58 if (s->receive_func) { 59 s->receive_func(s->opaque, NULL, 0); 60 } 61 62 s->receive_func = receive_entropy; 63 s->opaque = opaque; 64 s->size = size; 65 66 qemu_set_fd_handler(s->fd, entropy_available, NULL, s); 67 } 68 69 static void rng_random_opened(RngBackend *b, Error **errp) 70 { 71 RndRandom *s = RNG_RANDOM(b); 72 73 if (s->filename == NULL) { 74 error_set(errp, QERR_INVALID_PARAMETER_VALUE, 75 "filename", "a valid filename"); 76 } else { 77 s->fd = open(s->filename, O_RDONLY | O_NONBLOCK); 78 79 if (s->fd == -1) { 80 error_set(errp, QERR_OPEN_FILE_FAILED, s->filename); 81 } 82 } 83 } 84 85 static char *rng_random_get_filename(Object *obj, Error **errp) 86 { 87 RndRandom *s = RNG_RANDOM(obj); 88 89 if (s->filename) { 90 return g_strdup(s->filename); 91 } 92 93 return NULL; 94 } 95 96 static void rng_random_set_filename(Object *obj, const char *filename, 97 Error **errp) 98 { 99 RngBackend *b = RNG_BACKEND(obj); 100 RndRandom *s = RNG_RANDOM(obj); 101 102 if (b->opened) { 103 error_set(errp, QERR_PERMISSION_DENIED); 104 return; 105 } 106 107 if (s->filename) { 108 g_free(s->filename); 109 } 110 111 s->filename = g_strdup(filename); 112 } 113 114 static void rng_random_init(Object *obj) 115 { 116 RndRandom *s = RNG_RANDOM(obj); 117 118 object_property_add_str(obj, "filename", 119 rng_random_get_filename, 120 rng_random_set_filename, 121 NULL); 122 123 s->filename = g_strdup("/dev/random"); 124 } 125 126 static void rng_random_finalize(Object *obj) 127 { 128 RndRandom *s = RNG_RANDOM(obj); 129 130 qemu_set_fd_handler(s->fd, NULL, NULL, NULL); 131 132 if (s->fd != -1) { 133 close(s->fd); 134 } 135 136 g_free(s->filename); 137 } 138 139 static void rng_random_class_init(ObjectClass *klass, void *data) 140 { 141 RngBackendClass *rbc = RNG_BACKEND_CLASS(klass); 142 143 rbc->request_entropy = rng_random_request_entropy; 144 rbc->opened = rng_random_opened; 145 } 146 147 static TypeInfo rng_random_info = { 148 .name = TYPE_RNG_RANDOM, 149 .parent = TYPE_RNG_BACKEND, 150 .instance_size = sizeof(RndRandom), 151 .class_init = rng_random_class_init, 152 .instance_init = rng_random_init, 153 .instance_finalize = rng_random_finalize, 154 }; 155 156 static void register_types(void) 157 { 158 type_register_static(&rng_random_info); 159 } 160 161 type_init(register_types); 162