343 lines
8.4 KiB
C
343 lines
8.4 KiB
C
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/*
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* algif_rng: User-space interface for random number generators
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*
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* This file provides the user-space API for random number generators.
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*
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* Copyright (C) 2014, Stephan Mueller <smueller@chronox.de>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, and the entire permission notice in its entirety,
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* including the disclaimer of warranties.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote
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* products derived from this software without specific prior
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* written permission.
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*
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* ALTERNATIVELY, this product may be distributed under the terms of
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* the GNU General Public License, in which case the provisions of the GPL2
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* are required INSTEAD OF the above restrictions. (This clause is
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* necessary due to a potential bad interaction between the GPL and
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* the restrictions contained in a BSD-style copyright.)
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
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* WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
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* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
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* USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
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* DAMAGE.
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*/
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#include <linux/capability.h>
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#include <linux/module.h>
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#include <crypto/rng.h>
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#include <linux/random.h>
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#include <crypto/if_alg.h>
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#include <linux/net.h>
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#include <net/sock.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
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MODULE_DESCRIPTION("User-space interface for random number generators");
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struct rng_ctx {
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#define MAXSIZE 128
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unsigned int len;
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struct crypto_rng *drng;
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u8 *addtl;
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size_t addtl_len;
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};
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struct rng_parent_ctx {
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struct crypto_rng *drng;
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u8 *entropy;
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};
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static void rng_reset_addtl(struct rng_ctx *ctx)
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{
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kfree_sensitive(ctx->addtl);
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ctx->addtl = NULL;
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ctx->addtl_len = 0;
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}
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static int _rng_recvmsg(struct crypto_rng *drng, struct msghdr *msg, size_t len,
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u8 *addtl, size_t addtl_len)
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{
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int err = 0;
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int genlen = 0;
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u8 result[MAXSIZE];
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if (len == 0)
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return 0;
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if (len > MAXSIZE)
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len = MAXSIZE;
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/*
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* although not strictly needed, this is a precaution against coding
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* errors
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*/
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memset(result, 0, len);
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/*
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* The enforcement of a proper seeding of an RNG is done within an
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* RNG implementation. Some RNGs (DRBG, krng) do not need specific
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* seeding as they automatically seed. The X9.31 DRNG will return
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* an error if it was not seeded properly.
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*/
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genlen = crypto_rng_generate(drng, addtl, addtl_len, result, len);
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if (genlen < 0)
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return genlen;
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err = memcpy_to_msg(msg, result, len);
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memzero_explicit(result, len);
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return err ? err : len;
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}
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static int rng_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
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int flags)
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{
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struct sock *sk = sock->sk;
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struct alg_sock *ask = alg_sk(sk);
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struct rng_ctx *ctx = ask->private;
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return _rng_recvmsg(ctx->drng, msg, len, NULL, 0);
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}
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static int rng_test_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
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int flags)
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{
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struct sock *sk = sock->sk;
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struct alg_sock *ask = alg_sk(sk);
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struct rng_ctx *ctx = ask->private;
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int ret;
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lock_sock(sock->sk);
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ret = _rng_recvmsg(ctx->drng, msg, len, ctx->addtl, ctx->addtl_len);
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rng_reset_addtl(ctx);
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release_sock(sock->sk);
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return ret;
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}
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static int rng_test_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
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{
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int err;
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struct alg_sock *ask = alg_sk(sock->sk);
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struct rng_ctx *ctx = ask->private;
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lock_sock(sock->sk);
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if (len > MAXSIZE) {
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err = -EMSGSIZE;
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goto unlock;
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}
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rng_reset_addtl(ctx);
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ctx->addtl = kmalloc(len, GFP_KERNEL);
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if (!ctx->addtl) {
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err = -ENOMEM;
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goto unlock;
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}
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err = memcpy_from_msg(ctx->addtl, msg, len);
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if (err) {
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rng_reset_addtl(ctx);
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goto unlock;
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}
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ctx->addtl_len = len;
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unlock:
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release_sock(sock->sk);
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return err ? err : len;
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}
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static struct proto_ops algif_rng_ops = {
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.family = PF_ALG,
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.connect = sock_no_connect,
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.socketpair = sock_no_socketpair,
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.getname = sock_no_getname,
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.ioctl = sock_no_ioctl,
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.listen = sock_no_listen,
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.shutdown = sock_no_shutdown,
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.mmap = sock_no_mmap,
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.bind = sock_no_bind,
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.accept = sock_no_accept,
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.sendmsg = sock_no_sendmsg,
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.sendpage = sock_no_sendpage,
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.release = af_alg_release,
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.recvmsg = rng_recvmsg,
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};
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static struct proto_ops __maybe_unused algif_rng_test_ops = {
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.family = PF_ALG,
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.connect = sock_no_connect,
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.socketpair = sock_no_socketpair,
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.getname = sock_no_getname,
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.ioctl = sock_no_ioctl,
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.listen = sock_no_listen,
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.shutdown = sock_no_shutdown,
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.mmap = sock_no_mmap,
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.bind = sock_no_bind,
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.accept = sock_no_accept,
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.sendpage = sock_no_sendpage,
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.release = af_alg_release,
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.recvmsg = rng_test_recvmsg,
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.sendmsg = rng_test_sendmsg,
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};
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static void *rng_bind(const char *name, u32 type, u32 mask)
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{
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struct rng_parent_ctx *pctx;
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struct crypto_rng *rng;
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pctx = kzalloc(sizeof(*pctx), GFP_KERNEL);
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if (!pctx)
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return ERR_PTR(-ENOMEM);
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rng = crypto_alloc_rng(name, type, mask);
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if (IS_ERR(rng)) {
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kfree(pctx);
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return ERR_CAST(rng);
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}
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pctx->drng = rng;
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return pctx;
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}
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static void rng_release(void *private)
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{
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struct rng_parent_ctx *pctx = private;
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if (unlikely(!pctx))
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return;
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crypto_free_rng(pctx->drng);
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kfree_sensitive(pctx->entropy);
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kfree_sensitive(pctx);
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}
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static void rng_sock_destruct(struct sock *sk)
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{
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struct alg_sock *ask = alg_sk(sk);
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struct rng_ctx *ctx = ask->private;
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rng_reset_addtl(ctx);
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sock_kfree_s(sk, ctx, ctx->len);
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af_alg_release_parent(sk);
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}
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static int rng_accept_parent(void *private, struct sock *sk)
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{
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struct rng_ctx *ctx;
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struct rng_parent_ctx *pctx = private;
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struct alg_sock *ask = alg_sk(sk);
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unsigned int len = sizeof(*ctx);
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ctx = sock_kmalloc(sk, len, GFP_KERNEL);
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if (!ctx)
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return -ENOMEM;
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ctx->len = len;
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ctx->addtl = NULL;
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ctx->addtl_len = 0;
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/*
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* No seeding done at that point -- if multiple accepts are
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* done on one RNG instance, each resulting FD points to the same
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* state of the RNG.
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*/
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ctx->drng = pctx->drng;
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ask->private = ctx;
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sk->sk_destruct = rng_sock_destruct;
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/*
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* Non NULL pctx->entropy means that CAVP test has been initiated on
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* this socket, replace proto_ops algif_rng_ops with algif_rng_test_ops.
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*/
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if (IS_ENABLED(CONFIG_CRYPTO_USER_API_RNG_CAVP) && pctx->entropy)
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sk->sk_socket->ops = &algif_rng_test_ops;
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return 0;
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}
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static int rng_setkey(void *private, const u8 *seed, unsigned int seedlen)
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{
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struct rng_parent_ctx *pctx = private;
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/*
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* Check whether seedlen is of sufficient size is done in RNG
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* implementations.
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*/
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return crypto_rng_reset(pctx->drng, seed, seedlen);
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}
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static int __maybe_unused rng_setentropy(void *private, sockptr_t entropy,
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unsigned int len)
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{
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struct rng_parent_ctx *pctx = private;
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u8 *kentropy = NULL;
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if (!capable(CAP_SYS_ADMIN))
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return -EACCES;
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if (pctx->entropy)
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return -EINVAL;
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if (len > MAXSIZE)
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return -EMSGSIZE;
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if (len) {
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kentropy = memdup_sockptr(entropy, len);
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if (IS_ERR(kentropy))
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return PTR_ERR(kentropy);
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}
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crypto_rng_alg(pctx->drng)->set_ent(pctx->drng, kentropy, len);
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/*
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* Since rng doesn't perform any memory management for the entropy
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* buffer, save kentropy pointer to pctx now to free it after use.
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*/
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pctx->entropy = kentropy;
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return 0;
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}
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static const struct af_alg_type algif_type_rng = {
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.bind = rng_bind,
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.release = rng_release,
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.accept = rng_accept_parent,
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.setkey = rng_setkey,
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#ifdef CONFIG_CRYPTO_USER_API_RNG_CAVP
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.setentropy = rng_setentropy,
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#endif
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.ops = &algif_rng_ops,
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.name = "rng",
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.owner = THIS_MODULE
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};
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static int __init rng_init(void)
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{
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return af_alg_register_type(&algif_type_rng);
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}
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static void __exit rng_exit(void)
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{
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int err = af_alg_unregister_type(&algif_type_rng);
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BUG_ON(err);
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}
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module_init(rng_init);
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module_exit(rng_exit);
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