/*
 * algif_skcipher: User-space interface for skcipher algorithms
 *
 * This file provides the user-space API for symmetric key ciphers.
 *
 * Copyright (c) 2010 Herbert Xu <herbert@gondor.apana.org.au>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * The following concept of the memory management is used:
 *
 * The kernel maintains two SGLs, the TX SGL and the RX SGL. The TX SGL is
 * filled by user space with the data submitted via sendpage/sendmsg. Filling
 * up the TX SGL does not cause a crypto operation -- the data will only be
 * tracked by the kernel. Upon receipt of one recvmsg call, the caller must
 * provide a buffer which is tracked with the RX SGL.
 *
 * During the processing of the recvmsg operation, the cipher request is
 * allocated and prepared. As part of the recvmsg operation, the processed
 * TX buffers are extracted from the TX SGL into a separate SGL.
 *
 * After the completion of the crypto operation, the RX SGL and the cipher
 * request is released. The extracted TX SGL parts are released together with
 * the RX SGL release.
 */

#include <crypto/scatterwalk.h>
#include <crypto/skcipher.h>
#include <crypto/if_alg.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/net.h>
#include <net/sock.h>

struct skcipher_tfm {
        struct crypto_skcipher *skcipher;
        bool has_key;
};

static int skcipher_sendmsg(struct socket *sock, struct msghdr *msg,
                            size_t size)
{
        struct sock *sk = sock->sk;
        struct alg_sock *ask = alg_sk(sk);
        struct sock *psk = ask->parent;
        struct alg_sock *pask = alg_sk(psk);
        struct skcipher_tfm *skc = pask->private;
        struct crypto_skcipher *tfm = skc->skcipher;
        unsigned ivsize = crypto_skcipher_ivsize(tfm);

        return af_alg_sendmsg(sock, msg, size, ivsize);
}

static int _skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
                             size_t ignored, int flags)
{
        struct sock *sk = sock->sk;
        struct alg_sock *ask = alg_sk(sk);
        struct sock *psk = ask->parent;
        struct alg_sock *pask = alg_sk(psk);
        struct af_alg_ctx *ctx = ask->private;
        struct skcipher_tfm *skc = pask->private;
        struct crypto_skcipher *tfm = skc->skcipher;
        unsigned int bs = crypto_skcipher_blocksize(tfm);
        struct af_alg_async_req *areq;
        int err = 0;
        size_t len = 0;

        /* Allocate cipher request for current operation. */
        areq = af_alg_alloc_areq(sk, sizeof(struct af_alg_async_req) +
                                     crypto_skcipher_reqsize(tfm));
        if (IS_ERR(areq))
                return PTR_ERR(areq);

        /* convert iovecs of output buffers into RX SGL */
        err = af_alg_get_rsgl(sk, msg, flags, areq, -1, &len);
        if (err)
                goto free;

        /* Process only as much RX buffers for which we have TX data */
        if (len > ctx->used)
                len = ctx->used;

        /*
         * If more buffers are to be expected to be processed, process only
         * full block size buffers.
         */
        if (ctx->more || len < ctx->used)
                len -= len % bs;

        /*
         * Create a per request TX SGL for this request which tracks the
         * SG entries from the global TX SGL.
         */
        areq->tsgl_entries = af_alg_count_tsgl(sk, len, 0);
        if (!areq->tsgl_entries)
                areq->tsgl_entries = 1;
        areq->tsgl = sock_kmalloc(sk, sizeof(*areq->tsgl) * areq->tsgl_entries,
                                  GFP_KERNEL);
        if (!areq->tsgl) {
                err = -ENOMEM;
                goto free;
        }
        sg_init_table(areq->tsgl, areq->tsgl_entries);
        af_alg_pull_tsgl(sk, len, areq->tsgl, 0);

        /* Initialize the crypto operation */
        skcipher_request_set_tfm(&areq->cra_u.skcipher_req, tfm);
        skcipher_request_set_crypt(&areq->cra_u.skcipher_req, areq->tsgl,
                                   areq->first_rsgl.sgl.sg, len, ctx->iv);

        if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) {
                /* AIO operation */
                areq->iocb = msg->msg_iocb;
                skcipher_request_set_callback(&areq->cra_u.skcipher_req,
                                              CRYPTO_TFM_REQ_MAY_SLEEP,
                                              af_alg_async_cb, areq);
                err = ctx->enc ?
                        crypto_skcipher_encrypt(&areq->cra_u.skcipher_req) :
                        crypto_skcipher_decrypt(&areq->cra_u.skcipher_req);
        } else {
                /* Synchronous operation */
                skcipher_request_set_callback(&areq->cra_u.skcipher_req,
                                              CRYPTO_TFM_REQ_MAY_SLEEP |
                                              CRYPTO_TFM_REQ_MAY_BACKLOG,
                                              af_alg_complete,
                                              &ctx->completion);
                err = af_alg_wait_for_completion(ctx->enc ?
                        crypto_skcipher_encrypt(&areq->cra_u.skcipher_req) :
                        crypto_skcipher_decrypt(&areq->cra_u.skcipher_req),
                                                 &ctx->completion);
        }

        /* AIO operation in progress */
        if (err == -EINPROGRESS) {
                sock_hold(sk);

                /* Remember output size that will be generated. */
                areq->outlen = len;

                return -EIOCBQUEUED;
        }

free:
        af_alg_free_areq_sgls(areq);
        sock_kfree_s(sk, areq, areq->areqlen);

        return err ? err : len;
}

static int skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
                            size_t ignored, int flags)
{
        struct sock *sk = sock->sk;
        int ret = 0;

        lock_sock(sk);
        while (msg_data_left(msg)) {
                int err = _skcipher_recvmsg(sock, msg, ignored, flags);

                /*
                 * This error covers -EIOCBQUEUED which implies that we can
                 * only handle one AIO request. If the caller wants to have
                 * multiple AIO requests in parallel, he must make multiple
                 * separate AIO calls.
                 *
                 * Also return the error if no data has been processed so far.
                 */
                if (err <= 0) {
                        if (err == -EIOCBQUEUED || !ret)
                                ret = err;
                        goto out;
                }

                ret += err;
        }

out:
        af_alg_wmem_wakeup(sk);
        release_sock(sk);
        return ret;
}


static struct proto_ops algif_skcipher_ops = {
        .family         =       PF_ALG,

        .connect        =       sock_no_connect,
        .socketpair     =       sock_no_socketpair,
        .getname        =       sock_no_getname,
        .ioctl          =       sock_no_ioctl,
        .listen         =       sock_no_listen,
        .shutdown       =       sock_no_shutdown,
        .getsockopt     =       sock_no_getsockopt,
        .mmap           =       sock_no_mmap,
        .bind           =       sock_no_bind,
        .accept         =       sock_no_accept,
        .setsockopt     =       sock_no_setsockopt,

        .release        =       af_alg_release,
        .sendmsg        =       skcipher_sendmsg,
        .sendpage       =       af_alg_sendpage,
        .recvmsg        =       skcipher_recvmsg,
        .poll           =       af_alg_poll,
};

static int skcipher_check_key(struct socket *sock)
{
        int err = 0;
        struct sock *psk;
        struct alg_sock *pask;
        struct skcipher_tfm *tfm;
        struct sock *sk = sock->sk;
        struct alg_sock *ask = alg_sk(sk);

        lock_sock(sk);
        if (ask->refcnt)
                goto unlock_child;

        psk = ask->parent;
        pask = alg_sk(ask->parent);
        tfm = pask->private;

        err = -ENOKEY;
        lock_sock_nested(psk, SINGLE_DEPTH_NESTING);
        if (!tfm->has_key)
                goto unlock;

        if (!pask->refcnt++)
                sock_hold(psk);

        ask->refcnt = 1;
        sock_put(psk);

        err = 0;

unlock:
        release_sock(psk);
unlock_child:
        release_sock(sk);

        return err;
}

static int skcipher_sendmsg_nokey(struct socket *sock, struct msghdr *msg,
                                  size_t size)
{
        int err;

        err = skcipher_check_key(sock);
        if (err)
                return err;

        return skcipher_sendmsg(sock, msg, size);
}

static ssize_t skcipher_sendpage_nokey(struct socket *sock, struct page *page,
                                       int offset, size_t size, int flags)
{
        int err;

        err = skcipher_check_key(sock);
        if (err)
                return err;

        return af_alg_sendpage(sock, page, offset, size, flags);
}

static int skcipher_recvmsg_nokey(struct socket *sock, struct msghdr *msg,
                                  size_t ignored, int flags)
{
        int err;

        err = skcipher_check_key(sock);
        if (err)
                return err;

        return skcipher_recvmsg(sock, msg, ignored, flags);
}

static struct proto_ops algif_skcipher_ops_nokey = {
        .family         =       PF_ALG,

        .connect        =       sock_no_connect,
        .socketpair     =       sock_no_socketpair,
        .getname        =       sock_no_getname,
        .ioctl          =       sock_no_ioctl,
        .listen         =       sock_no_listen,
        .shutdown       =       sock_no_shutdown,
        .getsockopt     =       sock_no_getsockopt,
        .mmap           =       sock_no_mmap,
        .bind           =       sock_no_bind,
        .accept         =       sock_no_accept,
        .setsockopt     =       sock_no_setsockopt,

        .release        =       af_alg_release,
        .sendmsg        =       skcipher_sendmsg_nokey,
        .sendpage       =       skcipher_sendpage_nokey,
        .recvmsg        =       skcipher_recvmsg_nokey,
        .poll           =       af_alg_poll,
};

static void *skcipher_bind(const char *name, u32 type, u32 mask)
{
        struct skcipher_tfm *tfm;
        struct crypto_skcipher *skcipher;

        tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
        if (!tfm)
                return ERR_PTR(-ENOMEM);

        skcipher = crypto_alloc_skcipher(name, type, mask);
        if (IS_ERR(skcipher)) {
                kfree(tfm);
                return ERR_CAST(skcipher);
        }

        tfm->skcipher = skcipher;

        return tfm;
}

static void skcipher_release(void *private)
{
        struct skcipher_tfm *tfm = private;

        crypto_free_skcipher(tfm->skcipher);
        kfree(tfm);
}

static int skcipher_setkey(void *private, const u8 *key, unsigned int keylen)
{
        struct skcipher_tfm *tfm = private;
        int err;

        err = crypto_skcipher_setkey(tfm->skcipher, key, keylen);
        tfm->has_key = !err;

        return err;
}

static void skcipher_sock_destruct(struct sock *sk)
{
        struct alg_sock *ask = alg_sk(sk);
        struct af_alg_ctx *ctx = ask->private;
        struct sock *psk = ask->parent;
        struct alg_sock *pask = alg_sk(psk);
        struct skcipher_tfm *skc = pask->private;
        struct crypto_skcipher *tfm = skc->skcipher;

        af_alg_pull_tsgl(sk, ctx->used, NULL, 0);
        sock_kzfree_s(sk, ctx->iv, crypto_skcipher_ivsize(tfm));
        sock_kfree_s(sk, ctx, ctx->len);
        af_alg_release_parent(sk);
}

static int skcipher_accept_parent_nokey(void *private, struct sock *sk)
{
        struct af_alg_ctx *ctx;
        struct alg_sock *ask = alg_sk(sk);
        struct skcipher_tfm *tfm = private;
        struct crypto_skcipher *skcipher = tfm->skcipher;
        unsigned int len = sizeof(*ctx);

        ctx = sock_kmalloc(sk, len, GFP_KERNEL);
        if (!ctx)
                return -ENOMEM;

        ctx->iv = sock_kmalloc(sk, crypto_skcipher_ivsize(skcipher),
                               GFP_KERNEL);
        if (!ctx->iv) {
                sock_kfree_s(sk, ctx, len);
                return -ENOMEM;
        }

        memset(ctx->iv, 0, crypto_skcipher_ivsize(skcipher));

        INIT_LIST_HEAD(&ctx->tsgl_list);
        ctx->len = len;
        ctx->used = 0;
        ctx->rcvused = 0;
        ctx->more = 0;
        ctx->merge = 0;
        ctx->enc = 0;
        af_alg_init_completion(&ctx->completion);

        ask->private = ctx;

        sk->sk_destruct = skcipher_sock_destruct;

        return 0;
}

static int skcipher_accept_parent(void *private, struct sock *sk)
{
        struct skcipher_tfm *tfm = private;

        if (!tfm->has_key && crypto_skcipher_has_setkey(tfm->skcipher))
                return -ENOKEY;

        return skcipher_accept_parent_nokey(private, sk);
}

static const struct af_alg_type algif_type_skcipher = {
        .bind           =       skcipher_bind,
        .release        =       skcipher_release,
        .setkey         =       skcipher_setkey,
        .accept         =       skcipher_accept_parent,
        .accept_nokey   =       skcipher_accept_parent_nokey,
        .ops            =       &algif_skcipher_ops,
        .ops_nokey      =       &algif_skcipher_ops_nokey,
        .name           =       "skcipher",
        .owner          =       THIS_MODULE
};

static int __init algif_skcipher_init(void)
{
        return af_alg_register_type(&algif_type_skcipher);
}

static void __exit algif_skcipher_exit(void)
{
        int err = af_alg_unregister_type(&algif_type_skcipher);
        BUG_ON(err);
}

module_init(algif_skcipher_init);
module_exit(algif_skcipher_exit);
MODULE_LICENSE("GPL");