/*
 * algif_aead: User-space interface for AEAD algorithms
 *
 * Copyright (C) 2014, Stephan Mueller <smueller@chronox.de>
 *
 * This file provides the user-space API for AEAD ciphers.
 *
 * This file is derived from algif_skcipher.c.
 *
 * 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.
 */

#include <crypto/aead.h>
#include <crypto/scatterwalk.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 aead_sg_list {
        unsigned int cur;
        struct scatterlist sg[ALG_MAX_PAGES];
};

struct aead_ctx {
        struct aead_sg_list tsgl;
        /*
         * RSGL_MAX_ENTRIES is an artificial limit where user space at maximum
         * can cause the kernel to allocate RSGL_MAX_ENTRIES * ALG_MAX_PAGES
         * pages
         */
#define RSGL_MAX_ENTRIES ALG_MAX_PAGES
        struct af_alg_sgl rsgl[RSGL_MAX_ENTRIES];

        void *iv;

        struct af_alg_completion completion;

        unsigned long used;

        unsigned int len;
        bool more;
        bool merge;
        bool enc;

        size_t aead_assoclen;
        struct aead_request aead_req;
};

static inline int aead_sndbuf(struct sock *sk)
{
        struct alg_sock *ask = alg_sk(sk);
        struct aead_ctx *ctx = ask->private;

        return max_t(int, max_t(int, sk->sk_sndbuf & PAGE_MASK, PAGE_SIZE) -
                          ctx->used, 0);
}

static inline bool aead_writable(struct sock *sk)
{
        return PAGE_SIZE <= aead_sndbuf(sk);
}

static inline bool aead_sufficient_data(struct aead_ctx *ctx)
{
        unsigned as = crypto_aead_authsize(crypto_aead_reqtfm(&ctx->aead_req));

        return ctx->used >= ctx->aead_assoclen + as;
}

static void aead_put_sgl(struct sock *sk)
{
        struct alg_sock *ask = alg_sk(sk);
        struct aead_ctx *ctx = ask->private;
        struct aead_sg_list *sgl = &ctx->tsgl;
        struct scatterlist *sg = sgl->sg;
        unsigned int i;

        for (i = 0; i < sgl->cur; i++) {
                if (!sg_page(sg + i))
                        continue;

                put_page(sg_page(sg + i));
                sg_assign_page(sg + i, NULL);
        }
        sg_init_table(sg, ALG_MAX_PAGES);
        sgl->cur = 0;
        ctx->used = 0;
        ctx->more = 0;
        ctx->merge = 0;
}

static void aead_wmem_wakeup(struct sock *sk)
{
        struct socket_wq *wq;

        if (!aead_writable(sk))
                return;

        rcu_read_lock();
        wq = rcu_dereference(sk->sk_wq);
        if (skwq_has_sleeper(wq))
                wake_up_interruptible_sync_poll(&wq->wait, POLLIN |
                                                           POLLRDNORM |
                                                           POLLRDBAND);
        sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
        rcu_read_unlock();
}

static int aead_wait_for_data(struct sock *sk, unsigned flags)
{
        struct alg_sock *ask = alg_sk(sk);
        struct aead_ctx *ctx = ask->private;
        long timeout;
        DEFINE_WAIT(wait);
        int err = -ERESTARTSYS;

        if (flags & MSG_DONTWAIT)
                return -EAGAIN;

        sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);

        for (;;) {
                if (signal_pending(current))
                        break;
                prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
                timeout = MAX_SCHEDULE_TIMEOUT;
                if (sk_wait_event(sk, &timeout, !ctx->more)) {
                        err = 0;
                        break;
                }
        }
        finish_wait(sk_sleep(sk), &wait);

        sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);

        return err;
}

static void aead_data_wakeup(struct sock *sk)
{
        struct alg_sock *ask = alg_sk(sk);
        struct aead_ctx *ctx = ask->private;
        struct socket_wq *wq;

        if (ctx->more)
                return;
        if (!ctx->used)
                return;

        rcu_read_lock();
        wq = rcu_dereference(sk->sk_wq);
        if (skwq_has_sleeper(wq))
                wake_up_interruptible_sync_poll(&wq->wait, POLLOUT |
                                                           POLLRDNORM |
                                                           POLLRDBAND);
        sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
        rcu_read_unlock();
}

static int aead_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
{
        struct sock *sk = sock->sk;
        struct alg_sock *ask = alg_sk(sk);
        struct aead_ctx *ctx = ask->private;
        unsigned ivsize =
                crypto_aead_ivsize(crypto_aead_reqtfm(&ctx->aead_req));
        struct aead_sg_list *sgl = &ctx->tsgl;
        struct af_alg_control con = {};
        long copied = 0;
        bool enc = 0;
        bool init = 0;
        int err = -EINVAL;

        if (msg->msg_controllen) {
                err = af_alg_cmsg_send(msg, &con);
                if (err)
                        return err;

                init = 1;
                switch (con.op) {
                case ALG_OP_ENCRYPT:
                        enc = 1;
                        break;
                case ALG_OP_DECRYPT:
                        enc = 0;
                        break;
                default:
                        return -EINVAL;
                }

                if (con.iv && con.iv->ivlen != ivsize)
                        return -EINVAL;
        }

        lock_sock(sk);
        if (!ctx->more && ctx->used)
                goto unlock;

        if (init) {
                ctx->enc = enc;
                if (con.iv)
                        memcpy(ctx->iv, con.iv->iv, ivsize);

                ctx->aead_assoclen = con.aead_assoclen;
        }

        while (size) {
                size_t len = size;
                struct scatterlist *sg = NULL;

                /* use the existing memory in an allocated page */
                if (ctx->merge) {
                        sg = sgl->sg + sgl->cur - 1;
                        len = min_t(unsigned long, len,
                                    PAGE_SIZE - sg->offset - sg->length);
                        err = memcpy_from_msg(page_address(sg_page(sg)) +
                                              sg->offset + sg->length,
                                              msg, len);
                        if (err)
                                goto unlock;

                        sg->length += len;
                        ctx->merge = (sg->offset + sg->length) &
                                     (PAGE_SIZE - 1);

                        ctx->used += len;
                        copied += len;
                        size -= len;
                        continue;
                }

                if (!aead_writable(sk)) {
                        /* user space sent too much data */
                        aead_put_sgl(sk);
                        err = -EMSGSIZE;
                        goto unlock;
                }

                /* allocate a new page */
                len = min_t(unsigned long, size, aead_sndbuf(sk));
                while (len) {
                        size_t plen = 0;

                        if (sgl->cur >= ALG_MAX_PAGES) {
                                aead_put_sgl(sk);
                                err = -E2BIG;
                                goto unlock;
                        }

                        sg = sgl->sg + sgl->cur;
                        plen = min_t(size_t, len, PAGE_SIZE);

                        sg_assign_page(sg, alloc_page(GFP_KERNEL));
                        err = -ENOMEM;
                        if (!sg_page(sg))
                                goto unlock;

                        err = memcpy_from_msg(page_address(sg_page(sg)),
                                              msg, plen);
                        if (err) {
                                __free_page(sg_page(sg));
                                sg_assign_page(sg, NULL);
                                goto unlock;
                        }

                        sg->offset = 0;
                        sg->length = plen;
                        len -= plen;
                        ctx->used += plen;
                        copied += plen;
                        sgl->cur++;
                        size -= plen;
                        ctx->merge = plen & (PAGE_SIZE - 1);
                }
        }

        err = 0;

        ctx->more = msg->msg_flags & MSG_MORE;
        if (!ctx->more && !aead_sufficient_data(ctx)) {
                aead_put_sgl(sk);
                err = -EMSGSIZE;
        }

unlock:
        aead_data_wakeup(sk);
        release_sock(sk);

        return err ?: copied;
}

static ssize_t aead_sendpage(struct socket *sock, struct page *page,
                             int offset, size_t size, int flags)
{
        struct sock *sk = sock->sk;
        struct alg_sock *ask = alg_sk(sk);
        struct aead_ctx *ctx = ask->private;
        struct aead_sg_list *sgl = &ctx->tsgl;
        int err = -EINVAL;

        if (flags & MSG_SENDPAGE_NOTLAST)
                flags |= MSG_MORE;

        if (sgl->cur >= ALG_MAX_PAGES)
                return -E2BIG;

        lock_sock(sk);
        if (!ctx->more && ctx->used)
                goto unlock;

        if (!size)
                goto done;

        if (!aead_writable(sk)) {
                /* user space sent too much data */
                aead_put_sgl(sk);
                err = -EMSGSIZE;
                goto unlock;
        }

        ctx->merge = 0;

        get_page(page);
        sg_set_page(sgl->sg + sgl->cur, page, size, offset);
        sgl->cur++;
        ctx->used += size;

        err = 0;

done:
        ctx->more = flags & MSG_MORE;
        if (!ctx->more && !aead_sufficient_data(ctx)) {
                aead_put_sgl(sk);
                err = -EMSGSIZE;
        }

unlock:
        aead_data_wakeup(sk);
        release_sock(sk);

        return err ?: size;
}

static int aead_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 aead_ctx *ctx = ask->private;
        unsigned as = crypto_aead_authsize(crypto_aead_reqtfm(&ctx->aead_req));
        struct aead_sg_list *sgl = &ctx->tsgl;
        unsigned int i = 0;
        int err = -EINVAL;
        unsigned long used = 0;
        size_t outlen = 0;
        size_t usedpages = 0;
        unsigned int cnt = 0;

        /* Limit number of IOV blocks to be accessed below */
        if (msg->msg_iter.nr_segs > RSGL_MAX_ENTRIES)
                return -ENOMSG;

        lock_sock(sk);

        /*
         * AEAD memory structure: For encryption, the tag is appended to the
         * ciphertext which implies that the memory allocated for the ciphertext
         * must be increased by the tag length. For decryption, the tag
         * is expected to be concatenated to the ciphertext. The plaintext
         * therefore has a memory size of the ciphertext minus the tag length.
         *
         * The memory structure for cipher operation has the following
         * structure:
         *      AEAD encryption input:  assoc data || plaintext
         *      AEAD encryption output: cipherntext || auth tag
         *      AEAD decryption input:  assoc data || ciphertext || auth tag
         *      AEAD decryption output: plaintext
         */

        if (ctx->more) {
                err = aead_wait_for_data(sk, flags);
                if (err)
                        goto unlock;
        }

        used = ctx->used;

        /*
         * Make sure sufficient data is present -- note, the same check is
         * is also present in sendmsg/sendpage. The checks in sendpage/sendmsg
         * shall provide an information to the data sender that something is
         * wrong, but they are irrelevant to maintain the kernel integrity.
         * We need this check here too in case user space decides to not honor
         * the error message in sendmsg/sendpage and still call recvmsg. This
         * check here protects the kernel integrity.
         */
        if (!aead_sufficient_data(ctx))
                goto unlock;

        outlen = used;

        /*
         * The cipher operation input data is reduced by the associated data
         * length as this data is processed separately later on.
         */
        used -= ctx->aead_assoclen + (ctx->enc ? as : 0);

        /* convert iovecs of output buffers into scatterlists */
        while (iov_iter_count(&msg->msg_iter)) {
                size_t seglen = min_t(size_t, iov_iter_count(&msg->msg_iter),
                                      (outlen - usedpages));

                /* make one iovec available as scatterlist */
                err = af_alg_make_sg(&ctx->rsgl[cnt], &msg->msg_iter,
                                     seglen);
                if (err < 0)
                        goto unlock;
                usedpages += err;
                /* chain the new scatterlist with previous one */
                if (cnt)
                        af_alg_link_sg(&ctx->rsgl[cnt-1], &ctx->rsgl[cnt]);

                /* we do not need more iovecs as we have sufficient memory */
                if (outlen <= usedpages)
                        break;
                iov_iter_advance(&msg->msg_iter, err);
                cnt++;
        }

        err = -EINVAL;
        /* ensure output buffer is sufficiently large */
        if (usedpages < outlen)
                goto unlock;

        sg_mark_end(sgl->sg + sgl->cur - 1);

        aead_request_set_crypt(&ctx->aead_req, sgl->sg, ctx->rsgl[0].sg,
                               used, ctx->iv);
        aead_request_set_ad(&ctx->aead_req, ctx->aead_assoclen);

        err = af_alg_wait_for_completion(ctx->enc ?
                                         crypto_aead_encrypt(&ctx->aead_req) :
                                         crypto_aead_decrypt(&ctx->aead_req),
                                         &ctx->completion);

        if (err) {
                /* EBADMSG implies a valid cipher operation took place */
                if (err == -EBADMSG)
                        aead_put_sgl(sk);
                goto unlock;
        }

        aead_put_sgl(sk);

        err = 0;

unlock:
        for (i = 0; i < cnt; i++)
                af_alg_free_sg(&ctx->rsgl[i]);

        aead_wmem_wakeup(sk);
        release_sock(sk);

        return err ? err : outlen;
}

static unsigned int aead_poll(struct file *file, struct socket *sock,
                              poll_table *wait)
{
        struct sock *sk = sock->sk;
        struct alg_sock *ask = alg_sk(sk);
        struct aead_ctx *ctx = ask->private;
        unsigned int mask;

        sock_poll_wait(file, sk_sleep(sk), wait);
        mask = 0;

        if (!ctx->more)
                mask |= POLLIN | POLLRDNORM;

        if (aead_writable(sk))
                mask |= POLLOUT | POLLWRNORM | POLLWRBAND;

        return mask;
}

static struct proto_ops algif_aead_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        =       aead_sendmsg,
        .sendpage       =       aead_sendpage,
        .recvmsg        =       aead_recvmsg,
        .poll           =       aead_poll,
};

static void *aead_bind(const char *name, u32 type, u32 mask)
{
        return crypto_alloc_aead(name, type, mask);
}

static void aead_release(void *private)
{
        crypto_free_aead(private);
}

static int aead_setauthsize(void *private, unsigned int authsize)
{
        return crypto_aead_setauthsize(private, authsize);
}

static int aead_setkey(void *private, const u8 *key, unsigned int keylen)
{
        return crypto_aead_setkey(private, key, keylen);
}

static void aead_sock_destruct(struct sock *sk)
{
        struct alg_sock *ask = alg_sk(sk);
        struct aead_ctx *ctx = ask->private;
        unsigned int ivlen = crypto_aead_ivsize(
                                crypto_aead_reqtfm(&ctx->aead_req));

        aead_put_sgl(sk);
        sock_kzfree_s(sk, ctx->iv, ivlen);
        sock_kfree_s(sk, ctx, ctx->len);
        af_alg_release_parent(sk);
}

static int aead_accept_parent(void *private, struct sock *sk)
{
        struct aead_ctx *ctx;
        struct alg_sock *ask = alg_sk(sk);
        unsigned int len = sizeof(*ctx) + crypto_aead_reqsize(private);
        unsigned int ivlen = crypto_aead_ivsize(private);

        ctx = sock_kmalloc(sk, len, GFP_KERNEL);
        if (!ctx)
                return -ENOMEM;
        memset(ctx, 0, len);

        ctx->iv = sock_kmalloc(sk, ivlen, GFP_KERNEL);
        if (!ctx->iv) {
                sock_kfree_s(sk, ctx, len);
                return -ENOMEM;
        }
        memset(ctx->iv, 0, ivlen);

        ctx->len = len;
        ctx->used = 0;
        ctx->more = 0;
        ctx->merge = 0;
        ctx->enc = 0;
        ctx->tsgl.cur = 0;
        ctx->aead_assoclen = 0;
        af_alg_init_completion(&ctx->completion);
        sg_init_table(ctx->tsgl.sg, ALG_MAX_PAGES);

        ask->private = ctx;

        aead_request_set_tfm(&ctx->aead_req, private);
        aead_request_set_callback(&ctx->aead_req, CRYPTO_TFM_REQ_MAY_BACKLOG,
                                  af_alg_complete, &ctx->completion);

        sk->sk_destruct = aead_sock_destruct;

        return 0;
}

static const struct af_alg_type algif_type_aead = {
        .bind           =       aead_bind,
        .release        =       aead_release,
        .setkey         =       aead_setkey,
        .setauthsize    =       aead_setauthsize,
        .accept         =       aead_accept_parent,
        .ops            =       &algif_aead_ops,
        .name           =       "aead",
        .owner          =       THIS_MODULE
};

static int __init algif_aead_init(void)
{
        return af_alg_register_type(&algif_type_aead);
}

static void __exit algif_aead_exit(void)
{
        int err = af_alg_unregister_type(&algif_type_aead);
        BUG_ON(err);
}

module_init(algif_aead_init);
module_exit(algif_aead_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
MODULE_DESCRIPTION("AEAD kernel crypto API user space interface");