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 "sysemu/rng-random.h" 14 #include "sysemu/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 if (len < 0 && errno == EAGAIN) { 45 return; 46 } 47 g_assert(len != -1); 48 49 s->receive_func(s->opaque, buffer, len); 50 s->receive_func = NULL; 51 52 qemu_set_fd_handler(s->fd, NULL, NULL, NULL); 53 } 54 55 static void rng_random_request_entropy(RngBackend *b, size_t size, 56 EntropyReceiveFunc *receive_entropy, 57 void *opaque) 58 { 59 RndRandom *s = RNG_RANDOM(b); 60 61 if (s->receive_func) { 62 s->receive_func(s->opaque, NULL, 0); 63 } 64 65 s->receive_func = receive_entropy; 66 s->opaque = opaque; 67 s->size = size; 68 69 qemu_set_fd_handler(s->fd, entropy_available, NULL, s); 70 } 71 72 static void rng_random_opened(RngBackend *b, Error **errp) 73 { 74 RndRandom *s = RNG_RANDOM(b); 75 76 if (s->filename == NULL) { 77 error_set(errp, QERR_INVALID_PARAMETER_VALUE, 78 "filename", "a valid filename"); 79 } else { 80 s->fd = qemu_open(s->filename, O_RDONLY | O_NONBLOCK); 81 82 if (s->fd == -1) { 83 error_set(errp, QERR_OPEN_FILE_FAILED, s->filename); 84 } 85 } 86 } 87 88 static char *rng_random_get_filename(Object *obj, Error **errp) 89 { 90 RndRandom *s = RNG_RANDOM(obj); 91 92 if (s->filename) { 93 return g_strdup(s->filename); 94 } 95 96 return NULL; 97 } 98 99 static void rng_random_set_filename(Object *obj, const char *filename, 100 Error **errp) 101 { 102 RngBackend *b = RNG_BACKEND(obj); 103 RndRandom *s = RNG_RANDOM(obj); 104 105 if (b->opened) { 106 error_set(errp, QERR_PERMISSION_DENIED); 107 return; 108 } 109 110 if (s->filename) { 111 g_free(s->filename); 112 } 113 114 s->filename = g_strdup(filename); 115 } 116 117 static void rng_random_init(Object *obj) 118 { 119 RndRandom *s = RNG_RANDOM(obj); 120 121 object_property_add_str(obj, "filename", 122 rng_random_get_filename, 123 rng_random_set_filename, 124 NULL); 125 126 s->filename = g_strdup("/dev/random"); 127 } 128 129 static void rng_random_finalize(Object *obj) 130 { 131 RndRandom *s = RNG_RANDOM(obj); 132 133 qemu_set_fd_handler(s->fd, NULL, NULL, NULL); 134 135 if (s->fd != -1) { 136 qemu_close(s->fd); 137 } 138 139 g_free(s->filename); 140 } 141 142 static void rng_random_class_init(ObjectClass *klass, void *data) 143 { 144 RngBackendClass *rbc = RNG_BACKEND_CLASS(klass); 145 146 rbc->request_entropy = rng_random_request_entropy; 147 rbc->opened = rng_random_opened; 148 } 149 150 static const TypeInfo rng_random_info = { 151 .name = TYPE_RNG_RANDOM, 152 .parent = TYPE_RNG_BACKEND, 153 .instance_size = sizeof(RndRandom), 154 .class_init = rng_random_class_init, 155 .instance_init = rng_random_init, 156 .instance_finalize = rng_random_finalize, 157 }; 158 159 static void register_types(void) 160 { 161 type_register_static(&rng_random_info); 162 } 163 164 type_init(register_types); 165