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 if (s->fd == -1) { 82 error_setg_file_open(errp, errno, s->filename); 83 } 84 } 85 } 86 87 static char *rng_random_get_filename(Object *obj, Error **errp) 88 { 89 RndRandom *s = RNG_RANDOM(obj); 90 91 if (s->filename) { 92 return g_strdup(s->filename); 93 } 94 95 return NULL; 96 } 97 98 static void rng_random_set_filename(Object *obj, const char *filename, 99 Error **errp) 100 { 101 RngBackend *b = RNG_BACKEND(obj); 102 RndRandom *s = RNG_RANDOM(obj); 103 104 if (b->opened) { 105 error_set(errp, QERR_PERMISSION_DENIED); 106 return; 107 } 108 109 g_free(s->filename); 110 s->filename = g_strdup(filename); 111 } 112 113 static void rng_random_init(Object *obj) 114 { 115 RndRandom *s = RNG_RANDOM(obj); 116 117 object_property_add_str(obj, "filename", 118 rng_random_get_filename, 119 rng_random_set_filename, 120 NULL); 121 122 s->filename = g_strdup("/dev/random"); 123 s->fd = -1; 124 } 125 126 static void rng_random_finalize(Object *obj) 127 { 128 RndRandom *s = RNG_RANDOM(obj); 129 130 if (s->fd != -1) { 131 qemu_set_fd_handler(s->fd, NULL, NULL, NULL); 132 qemu_close(s->fd); 133 } 134 135 g_free(s->filename); 136 } 137 138 static void rng_random_class_init(ObjectClass *klass, void *data) 139 { 140 RngBackendClass *rbc = RNG_BACKEND_CLASS(klass); 141 142 rbc->request_entropy = rng_random_request_entropy; 143 rbc->opened = rng_random_opened; 144 } 145 146 static const TypeInfo rng_random_info = { 147 .name = TYPE_RNG_RANDOM, 148 .parent = TYPE_RNG_BACKEND, 149 .instance_size = sizeof(RndRandom), 150 .class_init = rng_random_class_init, 151 .instance_init = rng_random_init, 152 .instance_finalize = rng_random_finalize, 153 }; 154 155 static void register_types(void) 156 { 157 type_register_static(&rng_random_info); 158 } 159 160 type_init(register_types); 161