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; 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 .mmap = sock_no_mmap, 105 .bind = sock_no_bind, 106 .accept = sock_no_accept, 107 .sendmsg = sock_no_sendmsg, 108 .sendpage = sock_no_sendpage, 109 110 .release = af_alg_release, 111 .recvmsg = rng_recvmsg, 112 }; 113 114 static void *rng_bind(const char *name, u32 type, u32 mask) 115 { 116 return crypto_alloc_rng(name, type, mask); 117 } 118 119 static void rng_release(void *private) 120 { 121 crypto_free_rng(private); 122 } 123 124 static void rng_sock_destruct(struct sock *sk) 125 { 126 struct alg_sock *ask = alg_sk(sk); 127 struct rng_ctx *ctx = ask->private; 128 129 sock_kfree_s(sk, ctx, ctx->len); 130 af_alg_release_parent(sk); 131 } 132 133 static int rng_accept_parent(void *private, struct sock *sk) 134 { 135 struct rng_ctx *ctx; 136 struct alg_sock *ask = alg_sk(sk); 137 unsigned int len = sizeof(*ctx); 138 139 ctx = sock_kmalloc(sk, len, GFP_KERNEL); 140 if (!ctx) 141 return -ENOMEM; 142 143 ctx->len = len; 144 145 /* 146 * No seeding done at that point -- if multiple accepts are 147 * done on one RNG instance, each resulting FD points to the same 148 * state of the RNG. 149 */ 150 151 ctx->drng = private; 152 ask->private = ctx; 153 sk->sk_destruct = rng_sock_destruct; 154 155 return 0; 156 } 157 158 static int rng_setkey(void *private, const u8 *seed, unsigned int seedlen) 159 { 160 /* 161 * Check whether seedlen is of sufficient size is done in RNG 162 * implementations. 163 */ 164 return crypto_rng_reset(private, seed, seedlen); 165 } 166 167 static const struct af_alg_type algif_type_rng = { 168 .bind = rng_bind, 169 .release = rng_release, 170 .accept = rng_accept_parent, 171 .setkey = rng_setkey, 172 .ops = &algif_rng_ops, 173 .name = "rng", 174 .owner = THIS_MODULE 175 }; 176 177 static int __init rng_init(void) 178 { 179 return af_alg_register_type(&algif_type_rng); 180 } 181 182 static void __exit rng_exit(void) 183 { 184 int err = af_alg_unregister_type(&algif_type_rng); 185 BUG_ON(err); 186 } 187 188 module_init(rng_init); 189 module_exit(rng_exit); 190