algif_skcipher.c

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/*
 * algif_skcipher: User-space interface for skcipher algorithms
 *
 * This file provides the user-space API for symmetric key ciphers.
 *
 * Copyright (c) 2010 Herbert Xu <[email protected]>
 *
 * 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/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_sg_list {
    struct list_head list;

    int cur;

    struct scatterlist sg[0];
};

struct skcipher_ctx {
    struct list_head tsgl;
    struct af_alg_sgl rsgl;

    void *iv;

    struct af_alg_completion completion;

    unsigned used;

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

    struct ablkcipher_request req;
};

#define MAX_SGL_ENTS ((PAGE_SIZE - sizeof(struct skcipher_sg_list)) / \
              sizeof(struct scatterlist) - 1)

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

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

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

static int skcipher_alloc_sgl(struct sock *sk)
{
    struct alg_sock *ask = alg_sk(sk);
    struct skcipher_ctx *ctx = ask->private;
    struct skcipher_sg_list *sgl;
    struct scatterlist *sg = NULL;

    sgl = list_entry(ctx->tsgl.prev, struct skcipher_sg_list, list);
    if (!list_empty(&ctx->tsgl))
        sg = sgl->sg;

    if (!sg || sgl->cur >= MAX_SGL_ENTS) {
        sgl = sock_kmalloc(sk, sizeof(*sgl) +
                       sizeof(sgl->sg[0]) * (MAX_SGL_ENTS + 1),
                   GFP_KERNEL);
        if (!sgl)
            return -ENOMEM;

        sg_init_table(sgl->sg, MAX_SGL_ENTS + 1);
        sgl->cur = 0;

        if (sg)
            scatterwalk_sg_chain(sg, MAX_SGL_ENTS + 1, sgl->sg);

        list_add_tail(&sgl->list, &ctx->tsgl);
    }

    return 0;
}

static void skcipher_pull_sgl(struct sock *sk, int used)
{
    struct alg_sock *ask = alg_sk(sk);
    struct skcipher_ctx *ctx = ask->private;
    struct skcipher_sg_list *sgl;
    struct scatterlist *sg;
    int i;

    while (!list_empty(&ctx->tsgl)) {
        sgl = list_first_entry(&ctx->tsgl, struct skcipher_sg_list,
                       list);
        sg = sgl->sg;

        for (i = 0; i < sgl->cur; i++) {
            int plen = min_t(int, used, sg[i].length);

            if (!sg_page(sg + i))
                continue;

            sg[i].length -= plen;
            sg[i].offset += plen;

            used -= plen;
            ctx->used -= plen;

            if (sg[i].length)
                return;

            put_page(sg_page(sg + i));
            sg_assign_page(sg + i, NULL);
        }

        list_del(&sgl->list);
        sock_kfree_s(sk, sgl,
                 sizeof(*sgl) + sizeof(sgl->sg[0]) *
                        (MAX_SGL_ENTS + 1));
    }

    if (!ctx->used)
        ctx->merge = 0;
}

static void skcipher_free_sgl(struct sock *sk)
{
    struct alg_sock *ask = alg_sk(sk);
    struct skcipher_ctx *ctx = ask->private;

    skcipher_pull_sgl(sk, ctx->used);
}

static int skcipher_wait_for_wmem(struct sock *sk, unsigned flags)
{
    long timeout;
    DEFINE_WAIT(wait);
    int err = -ERESTARTSYS;

    if (flags & MSG_DONTWAIT)
        return -EAGAIN;

    set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);

    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, skcipher_writable(sk))) {
            err = 0;
            break;
        }
    }
    finish_wait(sk_sleep(sk), &wait);

    return err;
}

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

    if (!skcipher_writable(sk))
        return;

    rcu_read_lock();
    wq = rcu_dereference(sk->sk_wq);
    if (wq_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 skcipher_wait_for_data(struct sock *sk, unsigned flags)
{
    struct alg_sock *ask = alg_sk(sk);
    struct skcipher_ctx *ctx = ask->private;
    long timeout;
    DEFINE_WAIT(wait);
    int err = -ERESTARTSYS;

    if (flags & MSG_DONTWAIT) {
        return -EAGAIN;
    }

    set_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);

    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->used)) {
            err = 0;
            break;
        }
    }
    finish_wait(sk_sleep(sk), &wait);

    clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);

    return err;
}

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

    if (!ctx->used)
        return;

    rcu_read_lock();
    wq = rcu_dereference(sk->sk_wq);
    if (wq_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 skcipher_sendmsg(struct kiocb *unused, struct socket *sock,
                struct msghdr *msg, size_t size)
{
    struct sock *sk = sock->sk;
    struct alg_sock *ask = alg_sk(sk);
    struct skcipher_ctx *ctx = ask->private;
    struct crypto_ablkcipher *tfm = crypto_ablkcipher_reqtfm(&ctx->req);
    unsigned ivsize = crypto_ablkcipher_ivsize(tfm);
    struct skcipher_sg_list *sgl;
    struct af_alg_control con = {};
    long copied = 0;
    bool enc = 0;
    int err;
    int i;

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

        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;
    }

    err = -EINVAL;

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

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

    while (size) {
        struct scatterlist *sg;
        unsigned long len = size;
        int plen;

        if (ctx->merge) {
            sgl = list_entry(ctx->tsgl.prev,
                     struct skcipher_sg_list, list);
            sg = sgl->sg + sgl->cur - 1;
            len = min_t(unsigned long, len,
                    PAGE_SIZE - sg->offset - sg->length);

            err = memcpy_fromiovec(page_address(sg_page(sg)) +
                           sg->offset + sg->length,
                           msg->msg_iov, 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 (!skcipher_writable(sk)) {
            err = skcipher_wait_for_wmem(sk, msg->msg_flags);
            if (err)
                goto unlock;
        }

        len = min_t(unsigned long, len, skcipher_sndbuf(sk));

        err = skcipher_alloc_sgl(sk);
        if (err)
            goto unlock;

        sgl = list_entry(ctx->tsgl.prev, struct skcipher_sg_list, list);
        sg = sgl->sg;
        do {
            i = sgl->cur;
            plen = min_t(int, len, PAGE_SIZE);

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

            err = memcpy_fromiovec(page_address(sg_page(sg + i)),
                           msg->msg_iov, plen);
            if (err) {
                __free_page(sg_page(sg + i));
                sg_assign_page(sg + i, NULL);
                goto unlock;
            }

            sg[i].length = plen;
            len -= plen;
            ctx->used += plen;
            copied += plen;
            size -= plen;
            sgl->cur++;
        } while (len && sgl->cur < MAX_SGL_ENTS);

        ctx->merge = plen & (PAGE_SIZE - 1);
    }

    err = 0;

    ctx->more = msg->msg_flags & MSG_MORE;
    if (!ctx->more && !list_empty(&ctx->tsgl))
        sgl = list_entry(ctx->tsgl.prev, struct skcipher_sg_list, list);

unlock:
    skcipher_data_wakeup(sk);
    release_sock(sk);

    return copied ?: err;
}

static ssize_t skcipher_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 skcipher_ctx *ctx = ask->private;
    struct skcipher_sg_list *sgl;
    int err = -EINVAL;

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

    if (!size)
        goto done;

    if (!skcipher_writable(sk)) {
        err = skcipher_wait_for_wmem(sk, flags);
        if (err)
            goto unlock;
    }

    err = skcipher_alloc_sgl(sk);
    if (err)
        goto unlock;

    ctx->merge = 0;
    sgl = list_entry(ctx->tsgl.prev, struct skcipher_sg_list, list);

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

done:
    ctx->more = flags & MSG_MORE;
    if (!ctx->more && !list_empty(&ctx->tsgl))
        sgl = list_entry(ctx->tsgl.prev, struct skcipher_sg_list, list);

unlock:
    skcipher_data_wakeup(sk);
    release_sock(sk);

    return err ?: size;
}

static int skcipher_recvmsg(struct kiocb *unused, struct socket *sock,
                struct msghdr *msg, size_t ignored, int flags)
{
    struct sock *sk = sock->sk;
    struct alg_sock *ask = alg_sk(sk);
    struct skcipher_ctx *ctx = ask->private;
    unsigned bs = crypto_ablkcipher_blocksize(crypto_ablkcipher_reqtfm(
        &ctx->req));
    struct skcipher_sg_list *sgl;
    struct scatterlist *sg;
    unsigned long iovlen;
    struct iovec *iov;
    int err = -EAGAIN;
    int used;
    long copied = 0;

    lock_sock(sk);
    for (iov = msg->msg_iov, iovlen = msg->msg_iovlen; iovlen > 0;
         iovlen--, iov++) {
        unsigned long seglen = iov->iov_len;
        char __user *from = iov->iov_base;

        while (seglen) {
            sgl = list_first_entry(&ctx->tsgl,
                           struct skcipher_sg_list, list);
            sg = sgl->sg;

            while (!sg->length)
                sg++;

            used = ctx->used;
            if (!used) {
                err = skcipher_wait_for_data(sk, flags);
                if (err)
                    goto unlock;
            }

            used = min_t(unsigned long, used, seglen);

            used = af_alg_make_sg(&ctx->rsgl, from, used, 1);
            err = used;
            if (err < 0)
                goto unlock;

            if (ctx->more || used < ctx->used)
                used -= used % bs;

            err = -EINVAL;
            if (!used)
                goto free;

            ablkcipher_request_set_crypt(&ctx->req, sg,
                             ctx->rsgl.sg, used,
                             ctx->iv);

            err = af_alg_wait_for_completion(
                ctx->enc ?
                    crypto_ablkcipher_encrypt(&ctx->req) :
                    crypto_ablkcipher_decrypt(&ctx->req),
                &ctx->completion);

free:
            af_alg_free_sg(&ctx->rsgl);

            if (err)
                goto unlock;

            copied += used;
            from += used;
            seglen -= used;
            skcipher_pull_sgl(sk, used);
        }
    }

    err = 0;

unlock:
    skcipher_wmem_wakeup(sk);
    release_sock(sk);

    return copied ?: err;
}


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

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

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

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

    return mask;
}

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   =   skcipher_sendpage,
    .recvmsg    =   skcipher_recvmsg,
    .poll       =   skcipher_poll,
};

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

static void skcipher_release(void *private)
{
    crypto_free_ablkcipher(private);
}

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

static void skcipher_sock_destruct(struct sock *sk)
{
    struct alg_sock *ask = alg_sk(sk);
    struct skcipher_ctx *ctx = ask->private;
    struct crypto_ablkcipher *tfm = crypto_ablkcipher_reqtfm(&ctx->req);

    skcipher_free_sgl(sk);
    sock_kfree_s(sk, ctx->iv, crypto_ablkcipher_ivsize(tfm));
    sock_kfree_s(sk, ctx, ctx->len);
    af_alg_release_parent(sk);
}

static int skcipher_accept_parent(void *private, struct sock *sk)
{
    struct skcipher_ctx *ctx;
    struct alg_sock *ask = alg_sk(sk);
    unsigned int len = sizeof(*ctx) + crypto_ablkcipher_reqsize(private);

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

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

    memset(ctx->iv, 0, crypto_ablkcipher_ivsize(private));

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

    ask->private = ctx;

    ablkcipher_request_set_tfm(&ctx->req, private);
    ablkcipher_request_set_callback(&ctx->req, CRYPTO_TFM_REQ_MAY_BACKLOG,
                    af_alg_complete, &ctx->completion);

    sk->sk_destruct = skcipher_sock_destruct;

    return 0;
}

static const struct af_alg_type algif_type_skcipher = {
    .bind       =   skcipher_bind,
    .release    =   skcipher_release,
    .setkey     =   skcipher_setkey,
    .accept     =   skcipher_accept_parent,
    .ops        =   &algif_skcipher_ops,
    .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");