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Linux/crypto/algif_rng.c

  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/module.h>
 42 #include <crypto/rng.h>
 43 #include <linux/random.h>
 44 #include <crypto/if_alg.h>
 45 #include <linux/net.h>
 46 #include <net/sock.h>
 47 
 48 MODULE_LICENSE("GPL");
 49 MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
 50 MODULE_DESCRIPTION("User-space interface for random number generators");
 51 
 52 struct rng_ctx {
 53 #define MAXSIZE 128
 54         unsigned int len;
 55         struct crypto_rng *drng;
 56 };
 57 
 58 static int rng_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 59                        int flags)
 60 {
 61         struct sock *sk = sock->sk;
 62         struct alg_sock *ask = alg_sk(sk);
 63         struct rng_ctx *ctx = ask->private;
 64         int err = -EFAULT;
 65         int genlen = 0;
 66         u8 result[MAXSIZE];
 67 
 68         if (len == 0)
 69                 return 0;
 70         if (len > MAXSIZE)
 71                 len = MAXSIZE;
 72 
 73         /*
 74          * although not strictly needed, this is a precaution against coding
 75          * errors
 76          */
 77         memset(result, 0, len);
 78 
 79         /*
 80          * The enforcement of a proper seeding of an RNG is done within an
 81          * RNG implementation. Some RNGs (DRBG, krng) do not need specific
 82          * seeding as they automatically seed. The X9.31 DRNG will return
 83          * an error if it was not seeded properly.
 84          */
 85         genlen = crypto_rng_get_bytes(ctx->drng, result, len);
 86         if (genlen < 0)
 87                 return genlen;
 88 
 89         err = memcpy_to_msg(msg, result, len);
 90         memzero_explicit(result, len);
 91 
 92         return err ? err : len;
 93 }
 94 
 95 static struct proto_ops algif_rng_ops = {
 96         .family         =       PF_ALG,
 97 
 98         .connect        =       sock_no_connect,
 99         .socketpair     =       sock_no_socketpair,
100         .getname        =       sock_no_getname,
101         .ioctl          =       sock_no_ioctl,
102         .listen         =       sock_no_listen,
103         .shutdown       =       sock_no_shutdown,
104         .getsockopt     =       sock_no_getsockopt,
105         .mmap           =       sock_no_mmap,
106         .bind           =       sock_no_bind,
107         .accept         =       sock_no_accept,
108         .setsockopt     =       sock_no_setsockopt,
109         .poll           =       sock_no_poll,
110         .sendmsg        =       sock_no_sendmsg,
111         .sendpage       =       sock_no_sendpage,
112 
113         .release        =       af_alg_release,
114         .recvmsg        =       rng_recvmsg,
115 };
116 
117 static void *rng_bind(const char *name, u32 type, u32 mask)
118 {
119         return crypto_alloc_rng(name, type, mask);
120 }
121 
122 static void rng_release(void *private)
123 {
124         crypto_free_rng(private);
125 }
126 
127 static void rng_sock_destruct(struct sock *sk)
128 {
129         struct alg_sock *ask = alg_sk(sk);
130         struct rng_ctx *ctx = ask->private;
131 
132         sock_kfree_s(sk, ctx, ctx->len);
133         af_alg_release_parent(sk);
134 }
135 
136 static int rng_accept_parent(void *private, struct sock *sk)
137 {
138         struct rng_ctx *ctx;
139         struct alg_sock *ask = alg_sk(sk);
140         unsigned int len = sizeof(*ctx);
141 
142         ctx = sock_kmalloc(sk, len, GFP_KERNEL);
143         if (!ctx)
144                 return -ENOMEM;
145 
146         ctx->len = len;
147 
148         /*
149          * No seeding done at that point -- if multiple accepts are
150          * done on one RNG instance, each resulting FD points to the same
151          * state of the RNG.
152          */
153 
154         ctx->drng = private;
155         ask->private = ctx;
156         sk->sk_destruct = rng_sock_destruct;
157 
158         return 0;
159 }
160 
161 static int rng_setkey(void *private, const u8 *seed, unsigned int seedlen)
162 {
163         /*
164          * Check whether seedlen is of sufficient size is done in RNG
165          * implementations.
166          */
167         return crypto_rng_reset(private, seed, seedlen);
168 }
169 
170 static const struct af_alg_type algif_type_rng = {
171         .bind           =       rng_bind,
172         .release        =       rng_release,
173         .accept         =       rng_accept_parent,
174         .setkey         =       rng_setkey,
175         .ops            =       &algif_rng_ops,
176         .name           =       "rng",
177         .owner          =       THIS_MODULE
178 };
179 
180 static int __init rng_init(void)
181 {
182         return af_alg_register_type(&algif_type_rng);
183 }
184 
185 static void __exit rng_exit(void)
186 {
187         int err = af_alg_unregister_type(&algif_type_rng);
188         BUG_ON(err);
189 }
190 
191 module_init(rng_init);
192 module_exit(rng_exit);
193 

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