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
49MODULE_LICENSE("GPL");
50MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
51MODULE_DESCRIPTION("User-space interface for random number generators");
52
53struct 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
61struct rng_parent_ctx {
62	struct crypto_rng *drng;
63	u8 *entropy;
64};
65
66static 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
73static 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
107static 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
117static 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
133static 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
159unlock:
160	release_sock(sock->sk);
161	return err ? err : len;
162}
163
164static 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
182static 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
200static 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
219static 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
230static 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
240static 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
275static 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
285static 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
315static 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
328static int __init rng_init(void)
329{
330	return af_alg_register_type(&algif_type_rng);
331}
332
333static void __exit rng_exit(void)
334{
335	int err = af_alg_unregister_type(&algif_type_rng);
336	BUG_ON(err);
337}
338
339module_init(rng_init);
340module_exit(rng_exit);
341