| 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 "system/rng-random.h" |
| 15 | #include "system/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(s->filename, O_RDONLY | O_NONBLOCK, errp); |
| 79 | } |
| 80 | } |
| 81 | |
| 82 | static char *rng_random_get_filename(Object *obj, Error **errp) |
| 83 | { |
| 84 | RngRandom *s = RNG_RANDOM(obj); |
| 85 | |
| 86 | return g_strdup(s->filename); |
| 87 | } |
| 88 | |
| 89 | static void rng_random_set_filename(Object *obj, const char *filename, |
| 90 | Error **errp) |
| 91 | { |
| 92 | RngBackend *b = RNG_BACKEND(obj); |
| 93 | RngRandom *s = RNG_RANDOM(obj); |
| 94 | |
| 95 | if (b->opened) { |
| 96 | error_setg(errp, "Property 'filename' can no longer be set"); |
| 97 | return; |
| 98 | } |
| 99 | |
| 100 | g_free(s->filename); |
| 101 | s->filename = g_strdup(filename); |
| 102 | } |
| 103 | |
| 104 | static void rng_random_init(Object *obj) |
| 105 | { |
| 106 | RngRandom *s = RNG_RANDOM(obj); |
| 107 | |
| 108 | s->filename = g_strdup("/dev/urandom"); |
| 109 | s->fd = -1; |
| 110 | } |
| 111 | |
| 112 | static void rng_random_finalize(Object *obj) |
| 113 | { |
| 114 | RngRandom *s = RNG_RANDOM(obj); |
| 115 | |
| 116 | if (s->fd != -1) { |
| 117 | qemu_set_fd_handler(s->fd, NULL, NULL, NULL); |
| 118 | qemu_close(s->fd); |
| 119 | } |
| 120 | |
| 121 | g_free(s->filename); |
| 122 | } |
| 123 | |
| 124 | static void rng_random_class_init(ObjectClass *klass, const void *data) |
| 125 | { |
| 126 | RngBackendClass *rbc = RNG_BACKEND_CLASS(klass); |
| 127 | |
| 128 | rbc->request_entropy = rng_random_request_entropy; |
| 129 | rbc->opened = rng_random_opened; |
| 130 | object_class_property_add_str(klass, "filename", |
| 131 | rng_random_get_filename, |
| 132 | rng_random_set_filename); |
| 133 | |
| 134 | } |
| 135 | |
| 136 | static const TypeInfo rng_random_info = { |
| 137 | .name = TYPE_RNG_RANDOM, |
| 138 | .parent = TYPE_RNG_BACKEND, |
| 139 | .instance_size = sizeof(RngRandom), |
| 140 | .class_init = rng_random_class_init, |
| 141 | .instance_init = rng_random_init, |
| 142 | .instance_finalize = rng_random_finalize, |
| 143 | }; |
| 144 | |
| 145 | static void register_types(void) |
| 146 | { |
| 147 | type_register_static(&rng_random_info); |
| 148 | } |
| 149 | |
| 150 | type_init(register_types); |