blkcipher.c

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/*
 * Block chaining cipher operations.
 * 
 * Generic encrypt/decrypt wrapper for ciphers, handles operations across
 * multiple page boundaries by using temporary blocks.  In user context,
 * the kernel is given a chance to schedule us once per page.
 *
 * Copyright (c) 2006 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/internal/skcipher.h>
#include <crypto/scatterwalk.h>
#include <linux/errno.h>
#include <linux/hardirq.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/cryptouser.h>
#include <net/netlink.h>

#include "internal.h"

enum {
    BLKCIPHER_WALK_PHYS = 1 << 0,
    BLKCIPHER_WALK_SLOW = 1 << 1,
    BLKCIPHER_WALK_COPY = 1 << 2,
    BLKCIPHER_WALK_DIFF = 1 << 3,
};

static int blkcipher_walk_next(struct blkcipher_desc *desc,
                   struct blkcipher_walk *walk);
static int blkcipher_walk_first(struct blkcipher_desc *desc,
                struct blkcipher_walk *walk);

static inline void blkcipher_map_src(struct blkcipher_walk *walk)
{
    walk->src.virt.addr = scatterwalk_map(&walk->in);
}

static inline void blkcipher_map_dst(struct blkcipher_walk *walk)
{
    walk->dst.virt.addr = scatterwalk_map(&walk->out);
}

static inline void blkcipher_unmap_src(struct blkcipher_walk *walk)
{
    scatterwalk_unmap(walk->src.virt.addr);
}

static inline void blkcipher_unmap_dst(struct blkcipher_walk *walk)
{
    scatterwalk_unmap(walk->dst.virt.addr);
}

/* Get a spot of the specified length that does not straddle a page.
 * The caller needs to ensure that there is enough space for this operation.
 */
static inline u8 *blkcipher_get_spot(u8 *start, unsigned int len)
{
    u8 *end_page = (u8 *)(((unsigned long)(start + len - 1)) & PAGE_MASK);
    return max(start, end_page);
}

static inline unsigned int blkcipher_done_slow(struct crypto_blkcipher *tfm,
                           struct blkcipher_walk *walk,
                           unsigned int bsize)
{
    u8 *addr;
    unsigned int alignmask = crypto_blkcipher_alignmask(tfm);

    addr = (u8 *)ALIGN((unsigned long)walk->buffer, alignmask + 1);
    addr = blkcipher_get_spot(addr, bsize);
    scatterwalk_copychunks(addr, &walk->out, bsize, 1);
    return bsize;
}

static inline unsigned int blkcipher_done_fast(struct blkcipher_walk *walk,
                           unsigned int n)
{
    if (walk->flags & BLKCIPHER_WALK_COPY) {
        blkcipher_map_dst(walk);
        memcpy(walk->dst.virt.addr, walk->page, n);
        blkcipher_unmap_dst(walk);
    } else if (!(walk->flags & BLKCIPHER_WALK_PHYS)) {
        if (walk->flags & BLKCIPHER_WALK_DIFF)
            blkcipher_unmap_dst(walk);
        blkcipher_unmap_src(walk);
    }

    scatterwalk_advance(&walk->in, n);
    scatterwalk_advance(&walk->out, n);

    return n;
}

int blkcipher_walk_done(struct blkcipher_desc *desc,
            struct blkcipher_walk *walk, int err)
{
    struct crypto_blkcipher *tfm = desc->tfm;
    unsigned int nbytes = 0;

    if (likely(err >= 0)) {
        unsigned int n = walk->nbytes - err;

        if (likely(!(walk->flags & BLKCIPHER_WALK_SLOW)))
            n = blkcipher_done_fast(walk, n);
        else if (WARN_ON(err)) {
            err = -EINVAL;
            goto err;
        } else
            n = blkcipher_done_slow(tfm, walk, n);

        nbytes = walk->total - n;
        err = 0;
    }

    scatterwalk_done(&walk->in, 0, nbytes);
    scatterwalk_done(&walk->out, 1, nbytes);

err:
    walk->total = nbytes;
    walk->nbytes = nbytes;

    if (nbytes) {
        crypto_yield(desc->flags);
        return blkcipher_walk_next(desc, walk);
    }

    if (walk->iv != desc->info)
        memcpy(desc->info, walk->iv, crypto_blkcipher_ivsize(tfm));
    if (walk->buffer != walk->page)
        kfree(walk->buffer);
    if (walk->page)
        free_page((unsigned long)walk->page);

    return err;
}
EXPORT_SYMBOL_GPL(blkcipher_walk_done);

static inline int blkcipher_next_slow(struct blkcipher_desc *desc,
                      struct blkcipher_walk *walk,
                      unsigned int bsize,
                      unsigned int alignmask)
{
    unsigned int n;
    unsigned aligned_bsize = ALIGN(bsize, alignmask + 1);

    if (walk->buffer)
        goto ok;

    walk->buffer = walk->page;
    if (walk->buffer)
        goto ok;

    n = aligned_bsize * 3 - (alignmask + 1) +
        (alignmask & ~(crypto_tfm_ctx_alignment() - 1));
    walk->buffer = kmalloc(n, GFP_ATOMIC);
    if (!walk->buffer)
        return blkcipher_walk_done(desc, walk, -ENOMEM);

ok:
    walk->dst.virt.addr = (u8 *)ALIGN((unsigned long)walk->buffer,
                      alignmask + 1);
    walk->dst.virt.addr = blkcipher_get_spot(walk->dst.virt.addr, bsize);
    walk->src.virt.addr = blkcipher_get_spot(walk->dst.virt.addr +
                         aligned_bsize, bsize);

    scatterwalk_copychunks(walk->src.virt.addr, &walk->in, bsize, 0);

    walk->nbytes = bsize;
    walk->flags |= BLKCIPHER_WALK_SLOW;

    return 0;
}

static inline int blkcipher_next_copy(struct blkcipher_walk *walk)
{
    u8 *tmp = walk->page;

    blkcipher_map_src(walk);
    memcpy(tmp, walk->src.virt.addr, walk->nbytes);
    blkcipher_unmap_src(walk);

    walk->src.virt.addr = tmp;
    walk->dst.virt.addr = tmp;

    return 0;
}

static inline int blkcipher_next_fast(struct blkcipher_desc *desc,
                      struct blkcipher_walk *walk)
{
    unsigned long diff;

    walk->src.phys.page = scatterwalk_page(&walk->in);
    walk->src.phys.offset = offset_in_page(walk->in.offset);
    walk->dst.phys.page = scatterwalk_page(&walk->out);
    walk->dst.phys.offset = offset_in_page(walk->out.offset);

    if (walk->flags & BLKCIPHER_WALK_PHYS)
        return 0;

    diff = walk->src.phys.offset - walk->dst.phys.offset;
    diff |= walk->src.virt.page - walk->dst.virt.page;

    blkcipher_map_src(walk);
    walk->dst.virt.addr = walk->src.virt.addr;

    if (diff) {
        walk->flags |= BLKCIPHER_WALK_DIFF;
        blkcipher_map_dst(walk);
    }

    return 0;
}

static int blkcipher_walk_next(struct blkcipher_desc *desc,
                   struct blkcipher_walk *walk)
{
    struct crypto_blkcipher *tfm = desc->tfm;
    unsigned int alignmask = crypto_blkcipher_alignmask(tfm);
    unsigned int bsize;
    unsigned int n;
    int err;

    n = walk->total;
    if (unlikely(n < crypto_blkcipher_blocksize(tfm))) {
        desc->flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
        return blkcipher_walk_done(desc, walk, -EINVAL);
    }

    walk->flags &= ~(BLKCIPHER_WALK_SLOW | BLKCIPHER_WALK_COPY |
             BLKCIPHER_WALK_DIFF);
    if (!scatterwalk_aligned(&walk->in, alignmask) ||
        !scatterwalk_aligned(&walk->out, alignmask)) {
        walk->flags |= BLKCIPHER_WALK_COPY;
        if (!walk->page) {
            walk->page = (void *)__get_free_page(GFP_ATOMIC);
            if (!walk->page)
                n = 0;
        }
    }

    bsize = min(walk->blocksize, n);
    n = scatterwalk_clamp(&walk->in, n);
    n = scatterwalk_clamp(&walk->out, n);

    if (unlikely(n < bsize)) {
        err = blkcipher_next_slow(desc, walk, bsize, alignmask);
        goto set_phys_lowmem;
    }

    walk->nbytes = n;
    if (walk->flags & BLKCIPHER_WALK_COPY) {
        err = blkcipher_next_copy(walk);
        goto set_phys_lowmem;
    }

    return blkcipher_next_fast(desc, walk);

set_phys_lowmem:
    if (walk->flags & BLKCIPHER_WALK_PHYS) {
        walk->src.phys.page = virt_to_page(walk->src.virt.addr);
        walk->dst.phys.page = virt_to_page(walk->dst.virt.addr);
        walk->src.phys.offset &= PAGE_SIZE - 1;
        walk->dst.phys.offset &= PAGE_SIZE - 1;
    }
    return err;
}

static inline int blkcipher_copy_iv(struct blkcipher_walk *walk,
                    struct crypto_blkcipher *tfm,
                    unsigned int alignmask)
{
    unsigned bs = walk->blocksize;
    unsigned int ivsize = crypto_blkcipher_ivsize(tfm);
    unsigned aligned_bs = ALIGN(bs, alignmask + 1);
    unsigned int size = aligned_bs * 2 + ivsize + max(aligned_bs, ivsize) -
                (alignmask + 1);
    u8 *iv;

    size += alignmask & ~(crypto_tfm_ctx_alignment() - 1);
    walk->buffer = kmalloc(size, GFP_ATOMIC);
    if (!walk->buffer)
        return -ENOMEM;

    iv = (u8 *)ALIGN((unsigned long)walk->buffer, alignmask + 1);
    iv = blkcipher_get_spot(iv, bs) + aligned_bs;
    iv = blkcipher_get_spot(iv, bs) + aligned_bs;
    iv = blkcipher_get_spot(iv, ivsize);

    walk->iv = memcpy(iv, walk->iv, ivsize);
    return 0;
}

int blkcipher_walk_virt(struct blkcipher_desc *desc,
            struct blkcipher_walk *walk)
{
    walk->flags &= ~BLKCIPHER_WALK_PHYS;
    walk->blocksize = crypto_blkcipher_blocksize(desc->tfm);
    return blkcipher_walk_first(desc, walk);
}
EXPORT_SYMBOL_GPL(blkcipher_walk_virt);

int blkcipher_walk_phys(struct blkcipher_desc *desc,
            struct blkcipher_walk *walk)
{
    walk->flags |= BLKCIPHER_WALK_PHYS;
    walk->blocksize = crypto_blkcipher_blocksize(desc->tfm);
    return blkcipher_walk_first(desc, walk);
}
EXPORT_SYMBOL_GPL(blkcipher_walk_phys);

static int blkcipher_walk_first(struct blkcipher_desc *desc,
                struct blkcipher_walk *walk)
{
    struct crypto_blkcipher *tfm = desc->tfm;
    unsigned int alignmask = crypto_blkcipher_alignmask(tfm);

    if (WARN_ON_ONCE(in_irq()))
        return -EDEADLK;

    walk->nbytes = walk->total;
    if (unlikely(!walk->total))
        return 0;

    walk->buffer = NULL;
    walk->iv = desc->info;
    if (unlikely(((unsigned long)walk->iv & alignmask))) {
        int err = blkcipher_copy_iv(walk, tfm, alignmask);
        if (err)
            return err;
    }

    scatterwalk_start(&walk->in, walk->in.sg);
    scatterwalk_start(&walk->out, walk->out.sg);
    walk->page = NULL;

    return blkcipher_walk_next(desc, walk);
}

int blkcipher_walk_virt_block(struct blkcipher_desc *desc,
                  struct blkcipher_walk *walk,
                  unsigned int blocksize)
{
    walk->flags &= ~BLKCIPHER_WALK_PHYS;
    walk->blocksize = blocksize;
    return blkcipher_walk_first(desc, walk);
}
EXPORT_SYMBOL_GPL(blkcipher_walk_virt_block);

static int setkey_unaligned(struct crypto_tfm *tfm, const u8 *key,
                unsigned int keylen)
{
    struct blkcipher_alg *cipher = &tfm->__crt_alg->cra_blkcipher;
    unsigned long alignmask = crypto_tfm_alg_alignmask(tfm);
    int ret;
    u8 *buffer, *alignbuffer;
    unsigned long absize;

    absize = keylen + alignmask;
    buffer = kmalloc(absize, GFP_ATOMIC);
    if (!buffer)
        return -ENOMEM;

    alignbuffer = (u8 *)ALIGN((unsigned long)buffer, alignmask + 1);
    memcpy(alignbuffer, key, keylen);
    ret = cipher->setkey(tfm, alignbuffer, keylen);
    memset(alignbuffer, 0, keylen);
    kfree(buffer);
    return ret;
}

static int setkey(struct crypto_tfm *tfm, const u8 *key, unsigned int keylen)
{
    struct blkcipher_alg *cipher = &tfm->__crt_alg->cra_blkcipher;
    unsigned long alignmask = crypto_tfm_alg_alignmask(tfm);

    if (keylen < cipher->min_keysize || keylen > cipher->max_keysize) {
        tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
        return -EINVAL;
    }

    if ((unsigned long)key & alignmask)
        return setkey_unaligned(tfm, key, keylen);

    return cipher->setkey(tfm, key, keylen);
}

static int async_setkey(struct crypto_ablkcipher *tfm, const u8 *key,
            unsigned int keylen)
{
    return setkey(crypto_ablkcipher_tfm(tfm), key, keylen);
}

static int async_encrypt(struct ablkcipher_request *req)
{
    struct crypto_tfm *tfm = req->base.tfm;
    struct blkcipher_alg *alg = &tfm->__crt_alg->cra_blkcipher;
    struct blkcipher_desc desc = {
        .tfm = __crypto_blkcipher_cast(tfm),
        .info = req->info,
        .flags = req->base.flags,
    };


    return alg->encrypt(&desc, req->dst, req->src, req->nbytes);
}

static int async_decrypt(struct ablkcipher_request *req)
{
    struct crypto_tfm *tfm = req->base.tfm;
    struct blkcipher_alg *alg = &tfm->__crt_alg->cra_blkcipher;
    struct blkcipher_desc desc = {
        .tfm = __crypto_blkcipher_cast(tfm),
        .info = req->info,
        .flags = req->base.flags,
    };

    return alg->decrypt(&desc, req->dst, req->src, req->nbytes);
}

static unsigned int crypto_blkcipher_ctxsize(struct crypto_alg *alg, u32 type,
                         u32 mask)
{
    struct blkcipher_alg *cipher = &alg->cra_blkcipher;
    unsigned int len = alg->cra_ctxsize;

    if ((mask & CRYPTO_ALG_TYPE_MASK) == CRYPTO_ALG_TYPE_MASK &&
        cipher->ivsize) {
        len = ALIGN(len, (unsigned long)alg->cra_alignmask + 1);
        len += cipher->ivsize;
    }

    return len;
}

static int crypto_init_blkcipher_ops_async(struct crypto_tfm *tfm)
{
    struct ablkcipher_tfm *crt = &tfm->crt_ablkcipher;
    struct blkcipher_alg *alg = &tfm->__crt_alg->cra_blkcipher;

    crt->setkey = async_setkey;
    crt->encrypt = async_encrypt;
    crt->decrypt = async_decrypt;
    if (!alg->ivsize) {
        crt->givencrypt = skcipher_null_givencrypt;
        crt->givdecrypt = skcipher_null_givdecrypt;
    }
    crt->base = __crypto_ablkcipher_cast(tfm);
    crt->ivsize = alg->ivsize;

    return 0;
}

static int crypto_init_blkcipher_ops_sync(struct crypto_tfm *tfm)
{
    struct blkcipher_tfm *crt = &tfm->crt_blkcipher;
    struct blkcipher_alg *alg = &tfm->__crt_alg->cra_blkcipher;
    unsigned long align = crypto_tfm_alg_alignmask(tfm) + 1;
    unsigned long addr;

    crt->setkey = setkey;
    crt->encrypt = alg->encrypt;
    crt->decrypt = alg->decrypt;

    addr = (unsigned long)crypto_tfm_ctx(tfm);
    addr = ALIGN(addr, align);
    addr += ALIGN(tfm->__crt_alg->cra_ctxsize, align);
    crt->iv = (void *)addr;

    return 0;
}

static int crypto_init_blkcipher_ops(struct crypto_tfm *tfm, u32 type, u32 mask)
{
    struct blkcipher_alg *alg = &tfm->__crt_alg->cra_blkcipher;

    if (alg->ivsize > PAGE_SIZE / 8)
        return -EINVAL;

    if ((mask & CRYPTO_ALG_TYPE_MASK) == CRYPTO_ALG_TYPE_MASK)
        return crypto_init_blkcipher_ops_sync(tfm);
    else
        return crypto_init_blkcipher_ops_async(tfm);
}

#ifdef CONFIG_NET
static int crypto_blkcipher_report(struct sk_buff *skb, struct crypto_alg *alg)
{
    struct crypto_report_blkcipher rblkcipher;

    snprintf(rblkcipher.type, CRYPTO_MAX_ALG_NAME, "%s", "blkcipher");
    snprintf(rblkcipher.geniv, CRYPTO_MAX_ALG_NAME, "%s",
         alg->cra_blkcipher.geniv ?: "<default>");

    rblkcipher.blocksize = alg->cra_blocksize;
    rblkcipher.min_keysize = alg->cra_blkcipher.min_keysize;
    rblkcipher.max_keysize = alg->cra_blkcipher.max_keysize;
    rblkcipher.ivsize = alg->cra_blkcipher.ivsize;

    if (nla_put(skb, CRYPTOCFGA_REPORT_BLKCIPHER,
            sizeof(struct crypto_report_blkcipher), &rblkcipher))
        goto nla_put_failure;
    return 0;

nla_put_failure:
    return -EMSGSIZE;
}
#else
static int crypto_blkcipher_report(struct sk_buff *skb, struct crypto_alg *alg)
{
    return -ENOSYS;
}
#endif

static void crypto_blkcipher_show(struct seq_file *m, struct crypto_alg *alg)
    __attribute__ ((unused));
static void crypto_blkcipher_show(struct seq_file *m, struct crypto_alg *alg)
{
    seq_printf(m, "type         : blkcipher\n");
    seq_printf(m, "blocksize    : %u\n", alg->cra_blocksize);
    seq_printf(m, "min keysize  : %u\n", alg->cra_blkcipher.min_keysize);
    seq_printf(m, "max keysize  : %u\n", alg->cra_blkcipher.max_keysize);
    seq_printf(m, "ivsize       : %u\n", alg->cra_blkcipher.ivsize);
    seq_printf(m, "geniv        : %s\n", alg->cra_blkcipher.geniv ?:
                         "<default>");
}

const struct crypto_type crypto_blkcipher_type = {
    .ctxsize = crypto_blkcipher_ctxsize,
    .init = crypto_init_blkcipher_ops,
#ifdef CONFIG_PROC_FS
    .show = crypto_blkcipher_show,
#endif
    .report = crypto_blkcipher_report,
};
EXPORT_SYMBOL_GPL(crypto_blkcipher_type);

static int crypto_grab_nivcipher(struct crypto_skcipher_spawn *spawn,
                const char *name, u32 type, u32 mask)
{
    struct crypto_alg *alg;
    int err;

    type = crypto_skcipher_type(type);
    mask = crypto_skcipher_mask(mask)| CRYPTO_ALG_GENIV;

    alg = crypto_alg_mod_lookup(name, type, mask);
    if (IS_ERR(alg))
        return PTR_ERR(alg);

    err = crypto_init_spawn(&spawn->base, alg, spawn->base.inst, mask);
    crypto_mod_put(alg);
    return err;
}

struct crypto_instance *skcipher_geniv_alloc(struct crypto_template *tmpl,
                         struct rtattr **tb, u32 type,
                         u32 mask)
{
    struct {
        int (*setkey)(struct crypto_ablkcipher *tfm, const u8 *key,
                  unsigned int keylen);
        int (*encrypt)(struct ablkcipher_request *req);
        int (*decrypt)(struct ablkcipher_request *req);

        unsigned int min_keysize;
        unsigned int max_keysize;
        unsigned int ivsize;

        const char *geniv;
    } balg;
    const char *name;
    struct crypto_skcipher_spawn *spawn;
    struct crypto_attr_type *algt;
    struct crypto_instance *inst;
    struct crypto_alg *alg;
    int err;

    algt = crypto_get_attr_type(tb);
    err = PTR_ERR(algt);
    if (IS_ERR(algt))
        return ERR_PTR(err);

    if ((algt->type ^ (CRYPTO_ALG_TYPE_GIVCIPHER | CRYPTO_ALG_GENIV)) &
        algt->mask)
        return ERR_PTR(-EINVAL);

    name = crypto_attr_alg_name(tb[1]);
    err = PTR_ERR(name);
    if (IS_ERR(name))
        return ERR_PTR(err);

    inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
    if (!inst)
        return ERR_PTR(-ENOMEM);

    spawn = crypto_instance_ctx(inst);

    /* Ignore async algorithms if necessary. */
    mask |= crypto_requires_sync(algt->type, algt->mask);

    crypto_set_skcipher_spawn(spawn, inst);
    err = crypto_grab_nivcipher(spawn, name, type, mask);
    if (err)
        goto err_free_inst;

    alg = crypto_skcipher_spawn_alg(spawn);

    if ((alg->cra_flags & CRYPTO_ALG_TYPE_MASK) ==
        CRYPTO_ALG_TYPE_BLKCIPHER) {
        balg.ivsize = alg->cra_blkcipher.ivsize;
        balg.min_keysize = alg->cra_blkcipher.min_keysize;
        balg.max_keysize = alg->cra_blkcipher.max_keysize;

        balg.setkey = async_setkey;
        balg.encrypt = async_encrypt;
        balg.decrypt = async_decrypt;

        balg.geniv = alg->cra_blkcipher.geniv;
    } else {
        balg.ivsize = alg->cra_ablkcipher.ivsize;
        balg.min_keysize = alg->cra_ablkcipher.min_keysize;
        balg.max_keysize = alg->cra_ablkcipher.max_keysize;

        balg.setkey = alg->cra_ablkcipher.setkey;
        balg.encrypt = alg->cra_ablkcipher.encrypt;
        balg.decrypt = alg->cra_ablkcipher.decrypt;

        balg.geniv = alg->cra_ablkcipher.geniv;
    }

    err = -EINVAL;
    if (!balg.ivsize)
        goto err_drop_alg;

    /*
     * This is only true if we're constructing an algorithm with its
     * default IV generator.  For the default generator we elide the
     * template name and double-check the IV generator.
     */
    if (algt->mask & CRYPTO_ALG_GENIV) {
        if (!balg.geniv)
            balg.geniv = crypto_default_geniv(alg);
        err = -EAGAIN;
        if (strcmp(tmpl->name, balg.geniv))
            goto err_drop_alg;

        memcpy(inst->alg.cra_name, alg->cra_name, CRYPTO_MAX_ALG_NAME);
        memcpy(inst->alg.cra_driver_name, alg->cra_driver_name,
               CRYPTO_MAX_ALG_NAME);
    } else {
        err = -ENAMETOOLONG;
        if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
                 "%s(%s)", tmpl->name, alg->cra_name) >=
            CRYPTO_MAX_ALG_NAME)
            goto err_drop_alg;
        if (snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
                 "%s(%s)", tmpl->name, alg->cra_driver_name) >=
            CRYPTO_MAX_ALG_NAME)
            goto err_drop_alg;
    }

    inst->alg.cra_flags = CRYPTO_ALG_TYPE_GIVCIPHER | CRYPTO_ALG_GENIV;
    inst->alg.cra_flags |= alg->cra_flags & CRYPTO_ALG_ASYNC;
    inst->alg.cra_priority = alg->cra_priority;
    inst->alg.cra_blocksize = alg->cra_blocksize;
    inst->alg.cra_alignmask = alg->cra_alignmask;
    inst->alg.cra_type = &crypto_givcipher_type;

    inst->alg.cra_ablkcipher.ivsize = balg.ivsize;
    inst->alg.cra_ablkcipher.min_keysize = balg.min_keysize;
    inst->alg.cra_ablkcipher.max_keysize = balg.max_keysize;
    inst->alg.cra_ablkcipher.geniv = balg.geniv;

    inst->alg.cra_ablkcipher.setkey = balg.setkey;
    inst->alg.cra_ablkcipher.encrypt = balg.encrypt;
    inst->alg.cra_ablkcipher.decrypt = balg.decrypt;

out:
    return inst;

err_drop_alg:
    crypto_drop_skcipher(spawn);
err_free_inst:
    kfree(inst);
    inst = ERR_PTR(err);
    goto out;
}
EXPORT_SYMBOL_GPL(skcipher_geniv_alloc);

void skcipher_geniv_free(struct crypto_instance *inst)
{
    crypto_drop_skcipher(crypto_instance_ctx(inst));
    kfree(inst);
}
EXPORT_SYMBOL_GPL(skcipher_geniv_free);

int skcipher_geniv_init(struct crypto_tfm *tfm)
{
    struct crypto_instance *inst = (void *)tfm->__crt_alg;
    struct crypto_ablkcipher *cipher;

    cipher = crypto_spawn_skcipher(crypto_instance_ctx(inst));
    if (IS_ERR(cipher))
        return PTR_ERR(cipher);

    tfm->crt_ablkcipher.base = cipher;
    tfm->crt_ablkcipher.reqsize += crypto_ablkcipher_reqsize(cipher);

    return 0;
}
EXPORT_SYMBOL_GPL(skcipher_geniv_init);

void skcipher_geniv_exit(struct crypto_tfm *tfm)
{
    crypto_free_ablkcipher(tfm->crt_ablkcipher.base);
}
EXPORT_SYMBOL_GPL(skcipher_geniv_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Generic block chaining cipher type");