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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 <[email protected]>
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
49MODULE_LICENSE("GPL");
50MODULE_AUTHOR("Stephan Mueller <[email protected]>");
51MODULE_DESCRIPTION("User-space interface for random number generators");
52
53static const struct af_alg_allowlist_entry rng_allowlist[] = {
54 {},
55};
56
57struct rng_ctx {
58#define MAXSIZE 128
59 unsigned int len;
60 struct crypto_rng *drng;
61 u8 *addtl;
62 size_t addtl_len;
63};
64
65struct rng_parent_ctx {
66 struct crypto_rng *drng;
67 u8 *entropy;
68};
69
70static void rng_reset_addtl(struct rng_ctx *ctx)
71{
72 kfree_sensitive(ctx->addtl);
73 ctx->addtl = NULL;
74 ctx->addtl_len = 0;
75}
76
77static int _rng_recvmsg(struct crypto_rng *drng, struct msghdr *msg, size_t len,
78 u8 *addtl, size_t addtl_len)
79{
80 int err = 0;
81 int genlen = 0;
82 u8 result[MAXSIZE];
83
84 if (len == 0)
85 return 0;
86 if (len > MAXSIZE)
87 len = MAXSIZE;
88
89 /*
90 * although not strictly needed, this is a precaution against coding
91 * errors
92 */
93 memset(result, 0, len);
94
95 /*
96 * The enforcement of a proper seeding of an RNG is done within an
97 * RNG implementation. Some RNGs (DRBG, krng) do not need specific
98 * seeding as they automatically seed. The X9.31 DRNG will return
99 * an error if it was not seeded properly.
100 */
101 genlen = crypto_rng_generate(drng, addtl, addtl_len, result, len);
102 if (genlen < 0)
103 return genlen;
104
105 err = memcpy_to_msg(msg, result, len);
106 memzero_explicit(result, len);
107
108 return err ? err : len;
109}
110
111static int rng_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
112 int flags)
113{
114 struct sock *sk = sock->sk;
115 struct alg_sock *ask = alg_sk(sk);
116 struct rng_ctx *ctx = ask->private;
117
118 return _rng_recvmsg(ctx->drng, msg, len, NULL, 0);
119}
120
121static int rng_test_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
122 int flags)
123{
124 struct sock *sk = sock->sk;
125 struct alg_sock *ask = alg_sk(sk);
126 struct rng_ctx *ctx = ask->private;
127 int ret;
128
129 lock_sock(sock->sk);
130 ret = _rng_recvmsg(ctx->drng, msg, len, ctx->addtl, ctx->addtl_len);
131 rng_reset_addtl(ctx);
132 release_sock(sock->sk);
133
134 return ret;
135}
136
137static int rng_test_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
138{
139 int err;
140 struct alg_sock *ask = alg_sk(sock->sk);
141 struct rng_ctx *ctx = ask->private;
142
143 lock_sock(sock->sk);
144 if (len > MAXSIZE) {
145 err = -EMSGSIZE;
146 goto unlock;
147 }
148
149 rng_reset_addtl(ctx);
150 ctx->addtl = kmalloc(len, GFP_KERNEL);
151 if (!ctx->addtl) {
152 err = -ENOMEM;
153 goto unlock;
154 }
155
156 err = memcpy_from_msg(ctx->addtl, msg, len);
157 if (err) {
158 rng_reset_addtl(ctx);
159 goto unlock;
160 }
161 ctx->addtl_len = len;
162
163unlock:
164 release_sock(sock->sk);
165 return err ? err : len;
166}
167
168static struct proto_ops algif_rng_ops = {
169 .family = PF_ALG,
170
171 .connect = sock_no_connect,
172 .socketpair = sock_no_socketpair,
173 .getname = sock_no_getname,
174 .ioctl = sock_no_ioctl,
175 .listen = sock_no_listen,
176 .shutdown = sock_no_shutdown,
177 .mmap = sock_no_mmap,
178 .bind = sock_no_bind,
179 .accept = sock_no_accept,
180 .sendmsg = sock_no_sendmsg,
181
182 .release = af_alg_release,
183 .recvmsg = rng_recvmsg,
184};
185
186static struct proto_ops __maybe_unused algif_rng_test_ops = {
187 .family = PF_ALG,
188
189 .connect = sock_no_connect,
190 .socketpair = sock_no_socketpair,
191 .getname = sock_no_getname,
192 .ioctl = sock_no_ioctl,
193 .listen = sock_no_listen,
194 .shutdown = sock_no_shutdown,
195 .mmap = sock_no_mmap,
196 .bind = sock_no_bind,
197 .accept = sock_no_accept,
198
199 .release = af_alg_release,
200 .recvmsg = rng_test_recvmsg,
201 .sendmsg = rng_test_sendmsg,
202};
203
204static void *rng_bind(const char *name)
205{
206 struct rng_parent_ctx *pctx;
207 struct crypto_rng *rng;
208 int err;
209
210 err = af_alg_check_restriction(name, rng_allowlist);
211 if (err)
212 return ERR_PTR(err);
213
214 pctx = kzalloc_obj(*pctx);
215 if (!pctx)
216 return ERR_PTR(-ENOMEM);
217
218 rng = crypto_alloc_rng(name, 0, AF_ALG_CRYPTOAPI_MASK);
219 if (IS_ERR(rng)) {
220 kfree(pctx);
221 return ERR_CAST(rng);
222 }
223
224 pctx->drng = rng;
225 return pctx;
226}
227
228static void rng_release(void *private)
229{
230 struct rng_parent_ctx *pctx = private;
231
232 if (unlikely(!pctx))
233 return;
234 crypto_free_rng(pctx->drng);
235 kfree_sensitive(pctx->entropy);
236 kfree_sensitive(pctx);
237}
238
239static void rng_sock_destruct(struct sock *sk)
240{
241 struct alg_sock *ask = alg_sk(sk);
242 struct rng_ctx *ctx = ask->private;
243
244 rng_reset_addtl(ctx);
245 sock_kfree_s(sk, ctx, ctx->len);
246 af_alg_release_parent(sk);
247}
248
249static int rng_accept_parent(void *private, struct sock *sk)
250{
251 struct rng_ctx *ctx;
252 struct rng_parent_ctx *pctx = private;
253 struct alg_sock *ask = alg_sk(sk);
254 unsigned int len = sizeof(*ctx);
255
256 ctx = sock_kmalloc(sk, len, GFP_KERNEL);
257 if (!ctx)
258 return -ENOMEM;
259
260 memset(ctx, 0, len);
261 ctx->len = len;
262
263 /*
264 * No seeding done at that point -- if multiple accepts are
265 * done on one RNG instance, each resulting FD points to the same
266 * state of the RNG.
267 */
268
269 ctx->drng = pctx->drng;
270 ask->private = ctx;
271 sk->sk_destruct = rng_sock_destruct;
272
273 /*
274 * Non NULL pctx->entropy means that CAVP test has been initiated on
275 * this socket, replace proto_ops algif_rng_ops with algif_rng_test_ops.
276 */
277 if (IS_ENABLED(CONFIG_CRYPTO_USER_API_RNG_CAVP) && pctx->entropy)
278 sk->sk_socket->ops = &algif_rng_test_ops;
279
280 return 0;
281}
282
283static int rng_setkey(void *private, const u8 *seed, unsigned int seedlen)
284{
285 struct rng_parent_ctx *pctx = private;
286 /*
287 * Check whether seedlen is of sufficient size is done in RNG
288 * implementations.
289 */
290 return crypto_rng_reset(pctx->drng, seed, seedlen);
291}
292
293static int __maybe_unused rng_setentropy(void *private, sockptr_t entropy,
294 unsigned int len)
295{
296 struct rng_parent_ctx *pctx = private;
297 u8 *kentropy = NULL;
298
299 if (!capable(CAP_SYS_ADMIN))
300 return -EACCES;
301
302 if (pctx->entropy)
303 return -EINVAL;
304
305 if (len > MAXSIZE)
306 return -EMSGSIZE;
307
308 if (len) {
309 kentropy = memdup_sockptr(entropy, len);
310 if (IS_ERR(kentropy))
311 return PTR_ERR(kentropy);
312 }
313
314 crypto_rng_alg(pctx->drng)->set_ent(pctx->drng, kentropy, len);
315 /*
316 * Since rng doesn't perform any memory management for the entropy
317 * buffer, save kentropy pointer to pctx now to free it after use.
318 */
319 pctx->entropy = kentropy;
320 return 0;
321}
322
323static const struct af_alg_type algif_type_rng = {
324 .bind = rng_bind,
325 .release = rng_release,
326 .accept = rng_accept_parent,
327 .setkey = rng_setkey,
328#ifdef CONFIG_CRYPTO_USER_API_RNG_CAVP
329 .setentropy = rng_setentropy,
330#endif
331 .ops = &algif_rng_ops,
332 .name = "rng",
333 .owner = THIS_MODULE
334};
335
336static int __init rng_init(void)
337{
338 return af_alg_register_type(&algif_type_rng);
339}
340
341static void __exit rng_exit(void)
342{
343 int err = af_alg_unregister_type(&algif_type_rng);
344 BUG_ON(err);
345}
346
347module_init(rng_init);
348module_exit(rng_exit);