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 static const struct af_alg_allowlist_entry rng_allowlist[] = { 54 {}, 55 }; 56 57 struct 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 65 struct rng_parent_ctx { 66 struct crypto_rng *drng; 67 u8 *entropy; 68 }; 69 70 static 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 77 static 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 } 110 111 static 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 } 120 121 static 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 } 136 137 static 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; 162 163 unlock: 164 release_sock(sock->sk); 165 return err ? err : len; 166 } 167 168 static 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 }; 185 186 static 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 }; 203 204 static 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 } 227 228 static 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 } 238 239 static 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 } 248 249 static 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 } 282 283 static 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 } 292 293 static 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 } 322 323 static 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 }; 335 336 static int __init rng_init(void) 337 { 338 return af_alg_register_type(&algif_type_rng); 339 } 340 341 static void __exit rng_exit(void) 342 { 343 int err = af_alg_unregister_type(&algif_type_rng); 344 BUG_ON(err); 345 } 346 347 module_init(rng_init); 348 module_exit(rng_exit); 349