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![Elena Petrova](/assets/img/avatar_default.png)
Extend the user-space RNG interface: 1. Add entropy input via ALG_SET_DRBG_ENTROPY setsockopt option; 2. Add additional data input via sendmsg syscall. This allows DRBG to be tested with test vectors, for example for the purpose of CAVP testing, which otherwise isn't possible. To prevent erroneous use of entropy input, it is hidden under CRYPTO_USER_API_RNG_CAVP config option and requires CAP_SYS_ADMIN to succeed. Signed-off-by: Elena Petrova <lenaptr@google.com> Acked-by: Stephan Müller <smueller@chronox.de> Reviewed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
342 lines
8.4 KiB
C
342 lines
8.4 KiB
C
/*
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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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