1 /*
2 * algif_rng: User-space interface for random number generators
3 *
4 * This file provides the user-space API for random number generators.
5 *
6 * Copyright (C) 2014, Stephan Mueller <smueller@chronox.de>
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, and the entire permission notice in its entirety,
13 * including the disclaimer of warranties.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. The name of the author may not be used to endorse or promote
18 * products derived from this software without specific prior
19 * written permission.
20 *
21 * ALTERNATIVELY, this product may be distributed under the terms of
22 * the GNU General Public License, in which case the provisions of the GPL2
23 * are required INSTEAD OF the above restrictions. (This clause is
24 * necessary due to a potential bad interaction between the GPL and
25 * the restrictions contained in a BSD-style copyright.)
26 *
27 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
28 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
30 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
31 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
32 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
33 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
34 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
35 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
36 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
37 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
38 * DAMAGE.
39 */
40
41 #include <linux/capability.h>
42 #include <linux/module.h>
43 #include <crypto/rng.h>
44 #include <linux/random.h>
45 #include <crypto/if_alg.h>
46 #include <linux/net.h>
47 #include <net/sock.h>
48
49 MODULE_LICENSE("GPL");
50 MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
51 MODULE_DESCRIPTION("User-space interface for random number generators");
52
53 struct rng_ctx {
54 #define MAXSIZE 128
55 unsigned int len;
56 struct crypto_rng *drng;
57 u8 *addtl;
58 size_t addtl_len;
59 };
60
61 struct rng_parent_ctx {
62 struct crypto_rng *drng;
63 u8 *entropy;
64 };
65
66 static void rng_reset_addtl(struct rng_ctx *ctx)
67 {
68 kfree_sensitive(ctx->addtl);
69 ctx->addtl = NULL;
70 ctx->addtl_len = 0;
71 }
72
73 static int _rng_recvmsg(struct crypto_rng *drng, struct msghdr *msg, size_t len,
74 u8 *addtl, size_t addtl_len)
75 {
76 int err = 0;
77 int genlen = 0;
78 u8 result[MAXSIZE];
79
80 if (len == 0)
81 return 0;
82 if (len > MAXSIZE)
83 len = MAXSIZE;
84
85 /*
86 * although not strictly needed, this is a precaution against coding
87 * errors
88 */
89 memset(result, 0, len);
90
91 /*
92 * The enforcement of a proper seeding of an RNG is done within an
93 * RNG implementation. Some RNGs (DRBG, krng) do not need specific
94 * seeding as they automatically seed. The X9.31 DRNG will return
95 * an error if it was not seeded properly.
96 */
97 genlen = crypto_rng_generate(drng, addtl, addtl_len, result, len);
98 if (genlen < 0)
99 return genlen;
100
101 err = memcpy_to_msg(msg, result, len);
102 memzero_explicit(result, len);
103
104 return err ? err : len;
105 }
106
107 static int rng_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
108 int flags)
109 {
110 struct sock *sk = sock->sk;
111 struct alg_sock *ask = alg_sk(sk);
112 struct rng_ctx *ctx = ask->private;
113
114 return _rng_recvmsg(ctx->drng, msg, len, NULL, 0);
115 }
116
117 static int rng_test_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
118 int flags)
119 {
120 struct sock *sk = sock->sk;
121 struct alg_sock *ask = alg_sk(sk);
122 struct rng_ctx *ctx = ask->private;
123 int ret;
124
125 lock_sock(sock->sk);
126 ret = _rng_recvmsg(ctx->drng, msg, len, ctx->addtl, ctx->addtl_len);
127 rng_reset_addtl(ctx);
128 release_sock(sock->sk);
129
130 return ret;
131 }
132
133 static int rng_test_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
134 {
135 int err;
136 struct alg_sock *ask = alg_sk(sock->sk);
137 struct rng_ctx *ctx = ask->private;
138
139 lock_sock(sock->sk);
140 if (len > MAXSIZE) {
141 err = -EMSGSIZE;
142 goto unlock;
143 }
144
145 rng_reset_addtl(ctx);
146 ctx->addtl = kmalloc(len, GFP_KERNEL);
147 if (!ctx->addtl) {
148 err = -ENOMEM;
149 goto unlock;
150 }
151
152 err = memcpy_from_msg(ctx->addtl, msg, len);
153 if (err) {
154 rng_reset_addtl(ctx);
155 goto unlock;
156 }
157 ctx->addtl_len = len;
158
159 unlock:
160 release_sock(sock->sk);
161 return err ? err : len;
162 }
163
164 static struct proto_ops algif_rng_ops = {
165 .family = PF_ALG,
166
167 .connect = sock_no_connect,
168 .socketpair = sock_no_socketpair,
169 .getname = sock_no_getname,
170 .ioctl = sock_no_ioctl,
171 .listen = sock_no_listen,
172 .shutdown = sock_no_shutdown,
173 .mmap = sock_no_mmap,
174 .bind = sock_no_bind,
175 .accept = sock_no_accept,
176 .sendmsg = sock_no_sendmsg,
177
178 .release = af_alg_release,
179 .recvmsg = rng_recvmsg,
180 };
181
182 static struct proto_ops __maybe_unused algif_rng_test_ops = {
183 .family = PF_ALG,
184
185 .connect = sock_no_connect,
186 .socketpair = sock_no_socketpair,
187 .getname = sock_no_getname,
188 .ioctl = sock_no_ioctl,
189 .listen = sock_no_listen,
190 .shutdown = sock_no_shutdown,
191 .mmap = sock_no_mmap,
192 .bind = sock_no_bind,
193 .accept = sock_no_accept,
194
195 .release = af_alg_release,
196 .recvmsg = rng_test_recvmsg,
197 .sendmsg = rng_test_sendmsg,
198 };
199
200 static void *rng_bind(const char *name, u32 type, u32 mask)
201 {
202 struct rng_parent_ctx *pctx;
203 struct crypto_rng *rng;
204
205 pctx = kzalloc(sizeof(*pctx), GFP_KERNEL);
206 if (!pctx)
207 return ERR_PTR(-ENOMEM);
208
209 rng = crypto_alloc_rng(name, type, mask);
210 if (IS_ERR(rng)) {
211 kfree(pctx);
212 return ERR_CAST(rng);
213 }
214
215 pctx->drng = rng;
216 return pctx;
217 }
218
219 static void rng_release(void *private)
220 {
221 struct rng_parent_ctx *pctx = private;
222
223 if (unlikely(!pctx))
224 return;
225 crypto_free_rng(pctx->drng);
226 kfree_sensitive(pctx->entropy);
227 kfree_sensitive(pctx);
228 }
229
230 static void rng_sock_destruct(struct sock *sk)
231 {
232 struct alg_sock *ask = alg_sk(sk);
233 struct rng_ctx *ctx = ask->private;
234
235 rng_reset_addtl(ctx);
236 sock_kfree_s(sk, ctx, ctx->len);
237 af_alg_release_parent(sk);
238 }
239
240 static int rng_accept_parent(void *private, struct sock *sk)
241 {
242 struct rng_ctx *ctx;
243 struct rng_parent_ctx *pctx = private;
244 struct alg_sock *ask = alg_sk(sk);
245 unsigned int len = sizeof(*ctx);
246
247 ctx = sock_kmalloc(sk, len, GFP_KERNEL);
248 if (!ctx)
249 return -ENOMEM;
250
251 ctx->len = len;
252 ctx->addtl = NULL;
253 ctx->addtl_len = 0;
254
255 /*
256 * No seeding done at that point -- if multiple accepts are
257 * done on one RNG instance, each resulting FD points to the same
258 * state of the RNG.
259 */
260
261 ctx->drng = pctx->drng;
262 ask->private = ctx;
263 sk->sk_destruct = rng_sock_destruct;
264
265 /*
266 * Non NULL pctx->entropy means that CAVP test has been initiated on
267 * this socket, replace proto_ops algif_rng_ops with algif_rng_test_ops.
268 */
269 if (IS_ENABLED(CONFIG_CRYPTO_USER_API_RNG_CAVP) && pctx->entropy)
270 sk->sk_socket->ops = &algif_rng_test_ops;
271
272 return 0;
273 }
274
275 static int rng_setkey(void *private, const u8 *seed, unsigned int seedlen)
276 {
277 struct rng_parent_ctx *pctx = private;
278 /*
279 * Check whether seedlen is of sufficient size is done in RNG
280 * implementations.
281 */
282 return crypto_rng_reset(pctx->drng, seed, seedlen);
283 }
284
285 static int __maybe_unused rng_setentropy(void *private, sockptr_t entropy,
286 unsigned int len)
287 {
288 struct rng_parent_ctx *pctx = private;
289 u8 *kentropy = NULL;
290
291 if (!capable(CAP_SYS_ADMIN))
292 return -EACCES;
293
294 if (pctx->entropy)
295 return -EINVAL;
296
297 if (len > MAXSIZE)
298 return -EMSGSIZE;
299
300 if (len) {
301 kentropy = memdup_sockptr(entropy, len);
302 if (IS_ERR(kentropy))
303 return PTR_ERR(kentropy);
304 }
305
306 crypto_rng_alg(pctx->drng)->set_ent(pctx->drng, kentropy, len);
307 /*
308 * Since rng doesn't perform any memory management for the entropy
309 * buffer, save kentropy pointer to pctx now to free it after use.
310 */
311 pctx->entropy = kentropy;
312 return 0;
313 }
314
315 static const struct af_alg_type algif_type_rng = {
316 .bind = rng_bind,
317 .release = rng_release,
318 .accept = rng_accept_parent,
319 .setkey = rng_setkey,
320 #ifdef CONFIG_CRYPTO_USER_API_RNG_CAVP
321 .setentropy = rng_setentropy,
322 #endif
323 .ops = &algif_rng_ops,
324 .name = "rng",
325 .owner = THIS_MODULE
326 };
327
328 static int __init rng_init(void)
329 {
330 return af_alg_register_type(&algif_type_rng);
331 }
332
333 static void __exit rng_exit(void)
334 {
335 int err = af_alg_unregister_type(&algif_type_rng);
336 BUG_ON(err);
337 }
338
339 module_init(rng_init);
340 module_exit(rng_exit);
341
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