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/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         .sendpage       =       sock_no_sendpage,
 178
 179         .release        =       af_alg_release,
 180         .recvmsg        =       rng_recvmsg,
 181 };
 182
 183 static struct proto_ops __maybe_unused algif_rng_test_ops = {
 184         .family         =       PF_ALG,
 185
 186         .connect        =       sock_no_connect,
 187         .socketpair     =       sock_no_socketpair,
 188         .getname        =       sock_no_getname,
 189         .ioctl          =       sock_no_ioctl,
 190         .listen         =       sock_no_listen,
 191         .shutdown       =       sock_no_shutdown,
 192         .mmap           =       sock_no_mmap,
 193         .bind           =       sock_no_bind,
 194         .accept         =       sock_no_accept,
 195         .sendpage       =       sock_no_sendpage,
 196
 197         .release        =       af_alg_release,
 198         .recvmsg        =       rng_test_recvmsg,
 199         .sendmsg        =       rng_test_sendmsg,
 200 };
 201
 202 static void *rng_bind(const char *name, u32 type, u32 mask)
 203 {
 204         struct rng_parent_ctx *pctx;
 205         struct crypto_rng *rng;
 206
 207         pctx = kzalloc(sizeof(*pctx), GFP_KERNEL);
 208         if (!pctx)
 209                 return ERR_PTR(-ENOMEM);
 210
 211         rng = crypto_alloc_rng(name, type, mask);
 212         if (IS_ERR(rng)) {
 213                 kfree(pctx);
 214                 return ERR_CAST(rng);
 215         }
 216
 217         pctx->drng = rng;
 218         return pctx;
 219 }
 220
 221 static void rng_release(void *private)
 222 {
 223         struct rng_parent_ctx *pctx = private;
 224
 225         if (unlikely(!pctx))
 226                 return;
 227         crypto_free_rng(pctx->drng);
 228         kfree_sensitive(pctx->entropy);
 229         kfree_sensitive(pctx);
 230 }
 231
 232 static void rng_sock_destruct(struct sock *sk)
 233 {
 234         struct alg_sock *ask = alg_sk(sk);
 235         struct rng_ctx *ctx = ask->private;
 236
 237         rng_reset_addtl(ctx);
 238         sock_kfree_s(sk, ctx, ctx->len);
 239         af_alg_release_parent(sk);
 240 }
 241
 242 static int rng_accept_parent(void *private, struct sock *sk)
 243 {
 244         struct rng_ctx *ctx;
 245         struct rng_parent_ctx *pctx = private;
 246         struct alg_sock *ask = alg_sk(sk);
 247         unsigned int len = sizeof(*ctx);
 248
 249         ctx = sock_kmalloc(sk, len, GFP_KERNEL);
 250         if (!ctx)
 251                 return -ENOMEM;
 252
 253         ctx->len = len;
 254         ctx->addtl = NULL;
 255         ctx->addtl_len = 0;
 256
 257         /*
 258          * No seeding done at that point -- if multiple accepts are
 259          * done on one RNG instance, each resulting FD points to the same
 260          * state of the RNG.
 261          */
 262
 263         ctx->drng = pctx->drng;
 264         ask->private = ctx;
 265         sk->sk_destruct = rng_sock_destruct;
 266
 267         /*
 268          * Non NULL pctx->entropy means that CAVP test has been initiated on
 269          * this socket, replace proto_ops algif_rng_ops with algif_rng_test_ops.
 270          */
 271         if (IS_ENABLED(CONFIG_CRYPTO_USER_API_RNG_CAVP) && pctx->entropy)
 272                 sk->sk_socket->ops = &algif_rng_test_ops;
 273
 274         return 0;
 275 }
 276
 277 static int rng_setkey(void *private, const u8 *seed, unsigned int seedlen)
 278 {
 279         struct rng_parent_ctx *pctx = private;
 280         /*
 281          * Check whether seedlen is of sufficient size is done in RNG
 282          * implementations.
 283          */
 284         return crypto_rng_reset(pctx->drng, seed, seedlen);
 285 }
 286
 287 static int __maybe_unused rng_setentropy(void *private, sockptr_t entropy,
 288                                          unsigned int len)
 289 {
 290         struct rng_parent_ctx *pctx = private;
 291         u8 *kentropy = NULL;
 292
 293         if (!capable(CAP_SYS_ADMIN))
 294                 return -EACCES;
 295
 296         if (pctx->entropy)
 297                 return -EINVAL;
 298
 299         if (len > MAXSIZE)
 300                 return -EMSGSIZE;
 301
 302         if (len) {
 303                 kentropy = memdup_sockptr(entropy, len);
 304                 if (IS_ERR(kentropy))
 305                         return PTR_ERR(kentropy);
 306         }
 307
 308         crypto_rng_alg(pctx->drng)->set_ent(pctx->drng, kentropy, len);
 309         /*
 310          * Since rng doesn't perform any memory management for the entropy
 311          * buffer, save kentropy pointer to pctx now to free it after use.
 312          */
 313         pctx->entropy = kentropy;
 314         return 0;
 315 }
 316
 317 static const struct af_alg_type algif_type_rng = {
 318         .bind           =       rng_bind,
 319         .release        =       rng_release,
 320         .accept         =       rng_accept_parent,
 321         .setkey         =       rng_setkey,
 322 #ifdef CONFIG_CRYPTO_USER_API_RNG_CAVP
 323         .setentropy     =       rng_setentropy,
 324 #endif
 325         .ops            =       &algif_rng_ops,
 326         .name           =       "rng",
 327         .owner          =       THIS_MODULE
 328 };
 329
 330 static int __init rng_init(void)
 331 {
 332         return af_alg_register_type(&algif_type_rng);
 333 }
 334
 335 static void __exit rng_exit(void)
 336 {
 337         int err = af_alg_unregister_type(&algif_type_rng);
 338         BUG_ON(err);
 339 }
 340
 341 module_init(rng_init);
 342 module_exit(rng_exit);