ccm.c

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/*
 * CCM: Counter with CBC-MAC
 *
 * (C) Copyright IBM Corp. 2007 - Joy Latten <[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/aead.h>
#include <crypto/internal/skcipher.h>
#include <crypto/scatterwalk.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>

#include "internal.h"

struct ccm_instance_ctx {
    struct crypto_skcipher_spawn ctr;
    struct crypto_spawn cipher;
};

struct crypto_ccm_ctx {
    struct crypto_cipher *cipher;
    struct crypto_ablkcipher *ctr;
};

struct crypto_rfc4309_ctx {
    struct crypto_aead *child;
    u8 nonce[3];
};

struct crypto_ccm_req_priv_ctx {
    u8 odata[16];
    u8 idata[16];
    u8 auth_tag[16];
    u32 ilen;
    u32 flags;
    struct scatterlist src[2];
    struct scatterlist dst[2];
    struct ablkcipher_request abreq;
};

static inline struct crypto_ccm_req_priv_ctx *crypto_ccm_reqctx(
    struct aead_request *req)
{
    unsigned long align = crypto_aead_alignmask(crypto_aead_reqtfm(req));

    return (void *)PTR_ALIGN((u8 *)aead_request_ctx(req), align + 1);
}

static int set_msg_len(u8 *block, unsigned int msglen, int csize)
{
    __be32 data;

    memset(block, 0, csize);
    block += csize;

    if (csize >= 4)
        csize = 4;
    else if (msglen > (1 << (8 * csize)))
        return -EOVERFLOW;

    data = cpu_to_be32(msglen);
    memcpy(block - csize, (u8 *)&data + 4 - csize, csize);

    return 0;
}

static int crypto_ccm_setkey(struct crypto_aead *aead, const u8 *key,
                 unsigned int keylen)
{
    struct crypto_ccm_ctx *ctx = crypto_aead_ctx(aead);
    struct crypto_ablkcipher *ctr = ctx->ctr;
    struct crypto_cipher *tfm = ctx->cipher;
    int err = 0;

    crypto_ablkcipher_clear_flags(ctr, CRYPTO_TFM_REQ_MASK);
    crypto_ablkcipher_set_flags(ctr, crypto_aead_get_flags(aead) &
                    CRYPTO_TFM_REQ_MASK);
    err = crypto_ablkcipher_setkey(ctr, key, keylen);
    crypto_aead_set_flags(aead, crypto_ablkcipher_get_flags(ctr) &
                  CRYPTO_TFM_RES_MASK);
    if (err)
        goto out;

    crypto_cipher_clear_flags(tfm, CRYPTO_TFM_REQ_MASK);
    crypto_cipher_set_flags(tfm, crypto_aead_get_flags(aead) &
                    CRYPTO_TFM_REQ_MASK);
    err = crypto_cipher_setkey(tfm, key, keylen);
    crypto_aead_set_flags(aead, crypto_cipher_get_flags(tfm) &
                  CRYPTO_TFM_RES_MASK);

out:
    return err;
}

static int crypto_ccm_setauthsize(struct crypto_aead *tfm,
                  unsigned int authsize)
{
    switch (authsize) {
    case 4:
    case 6:
    case 8:
    case 10:
    case 12:
    case 14:
    case 16:
        break;
    default:
        return -EINVAL;
    }

    return 0;
}

static int format_input(u8 *info, struct aead_request *req,
            unsigned int cryptlen)
{
    struct crypto_aead *aead = crypto_aead_reqtfm(req);
    unsigned int lp = req->iv[0];
    unsigned int l = lp + 1;
    unsigned int m;

    m = crypto_aead_authsize(aead);

    memcpy(info, req->iv, 16);

    /* format control info per RFC 3610 and
     * NIST Special Publication 800-38C
     */
    *info |= (8 * ((m - 2) / 2));
    if (req->assoclen)
        *info |= 64;

    return set_msg_len(info + 16 - l, cryptlen, l);
}

static int format_adata(u8 *adata, unsigned int a)
{
    int len = 0;

    /* add control info for associated data
     * RFC 3610 and NIST Special Publication 800-38C
     */
    if (a < 65280) {
        *(__be16 *)adata = cpu_to_be16(a);
        len = 2;
    } else  {
        *(__be16 *)adata = cpu_to_be16(0xfffe);
        *(__be32 *)&adata[2] = cpu_to_be32(a);
        len = 6;
    }

    return len;
}

static void compute_mac(struct crypto_cipher *tfm, u8 *data, int n,
               struct crypto_ccm_req_priv_ctx *pctx)
{
    unsigned int bs = 16;
    u8 *odata = pctx->odata;
    u8 *idata = pctx->idata;
    int datalen, getlen;

    datalen = n;

    /* first time in here, block may be partially filled. */
    getlen = bs - pctx->ilen;
    if (datalen >= getlen) {
        memcpy(idata + pctx->ilen, data, getlen);
        crypto_xor(odata, idata, bs);
        crypto_cipher_encrypt_one(tfm, odata, odata);
        datalen -= getlen;
        data += getlen;
        pctx->ilen = 0;
    }

    /* now encrypt rest of data */
    while (datalen >= bs) {
        crypto_xor(odata, data, bs);
        crypto_cipher_encrypt_one(tfm, odata, odata);

        datalen -= bs;
        data += bs;
    }

    /* check and see if there's leftover data that wasn't
     * enough to fill a block.
     */
    if (datalen) {
        memcpy(idata + pctx->ilen, data, datalen);
        pctx->ilen += datalen;
    }
}

static void get_data_to_compute(struct crypto_cipher *tfm,
                   struct crypto_ccm_req_priv_ctx *pctx,
                   struct scatterlist *sg, unsigned int len)
{
    struct scatter_walk walk;
    u8 *data_src;
    int n;

    scatterwalk_start(&walk, sg);

    while (len) {
        n = scatterwalk_clamp(&walk, len);
        if (!n) {
            scatterwalk_start(&walk, sg_next(walk.sg));
            n = scatterwalk_clamp(&walk, len);
        }
        data_src = scatterwalk_map(&walk);

        compute_mac(tfm, data_src, n, pctx);
        len -= n;

        scatterwalk_unmap(data_src);
        scatterwalk_advance(&walk, n);
        scatterwalk_done(&walk, 0, len);
        if (len)
            crypto_yield(pctx->flags);
    }

    /* any leftover needs padding and then encrypted */
    if (pctx->ilen) {
        int padlen;
        u8 *odata = pctx->odata;
        u8 *idata = pctx->idata;

        padlen = 16 - pctx->ilen;
        memset(idata + pctx->ilen, 0, padlen);
        crypto_xor(odata, idata, 16);
        crypto_cipher_encrypt_one(tfm, odata, odata);
        pctx->ilen = 0;
    }
}

static int crypto_ccm_auth(struct aead_request *req, struct scatterlist *plain,
               unsigned int cryptlen)
{
    struct crypto_aead *aead = crypto_aead_reqtfm(req);
    struct crypto_ccm_ctx *ctx = crypto_aead_ctx(aead);
    struct crypto_ccm_req_priv_ctx *pctx = crypto_ccm_reqctx(req);
    struct crypto_cipher *cipher = ctx->cipher;
    unsigned int assoclen = req->assoclen;
    u8 *odata = pctx->odata;
    u8 *idata = pctx->idata;
    int err;

    /* format control data for input */
    err = format_input(odata, req, cryptlen);
    if (err)
        goto out;

    /* encrypt first block to use as start in computing mac  */
    crypto_cipher_encrypt_one(cipher, odata, odata);

    /* format associated data and compute into mac */
    if (assoclen) {
        pctx->ilen = format_adata(idata, assoclen);
        get_data_to_compute(cipher, pctx, req->assoc, req->assoclen);
    } else {
        pctx->ilen = 0;
    }

    /* compute plaintext into mac */
    get_data_to_compute(cipher, pctx, plain, cryptlen);

out:
    return err;
}

static void crypto_ccm_encrypt_done(struct crypto_async_request *areq, int err)
{
    struct aead_request *req = areq->data;
    struct crypto_aead *aead = crypto_aead_reqtfm(req);
    struct crypto_ccm_req_priv_ctx *pctx = crypto_ccm_reqctx(req);
    u8 *odata = pctx->odata;

    if (!err)
        scatterwalk_map_and_copy(odata, req->dst, req->cryptlen,
                     crypto_aead_authsize(aead), 1);
    aead_request_complete(req, err);
}

static inline int crypto_ccm_check_iv(const u8 *iv)
{
    /* 2 <= L <= 8, so 1 <= L' <= 7. */
    if (1 > iv[0] || iv[0] > 7)
        return -EINVAL;

    return 0;
}

static int crypto_ccm_encrypt(struct aead_request *req)
{
    struct crypto_aead *aead = crypto_aead_reqtfm(req);
    struct crypto_ccm_ctx *ctx = crypto_aead_ctx(aead);
    struct crypto_ccm_req_priv_ctx *pctx = crypto_ccm_reqctx(req);
    struct ablkcipher_request *abreq = &pctx->abreq;
    struct scatterlist *dst;
    unsigned int cryptlen = req->cryptlen;
    u8 *odata = pctx->odata;
    u8 *iv = req->iv;
    int err;

    err = crypto_ccm_check_iv(iv);
    if (err)
        return err;

    pctx->flags = aead_request_flags(req);

    err = crypto_ccm_auth(req, req->src, cryptlen);
    if (err)
        return err;

     /* Note: rfc 3610 and NIST 800-38C require counter of
     * zero to encrypt auth tag.
     */
    memset(iv + 15 - iv[0], 0, iv[0] + 1);

    sg_init_table(pctx->src, 2);
    sg_set_buf(pctx->src, odata, 16);
    scatterwalk_sg_chain(pctx->src, 2, req->src);

    dst = pctx->src;
    if (req->src != req->dst) {
        sg_init_table(pctx->dst, 2);
        sg_set_buf(pctx->dst, odata, 16);
        scatterwalk_sg_chain(pctx->dst, 2, req->dst);
        dst = pctx->dst;
    }

    ablkcipher_request_set_tfm(abreq, ctx->ctr);
    ablkcipher_request_set_callback(abreq, pctx->flags,
                    crypto_ccm_encrypt_done, req);
    ablkcipher_request_set_crypt(abreq, pctx->src, dst, cryptlen + 16, iv);
    err = crypto_ablkcipher_encrypt(abreq);
    if (err)
        return err;

    /* copy authtag to end of dst */
    scatterwalk_map_and_copy(odata, req->dst, cryptlen,
                 crypto_aead_authsize(aead), 1);
    return err;
}

static void crypto_ccm_decrypt_done(struct crypto_async_request *areq,
                   int err)
{
    struct aead_request *req = areq->data;
    struct crypto_ccm_req_priv_ctx *pctx = crypto_ccm_reqctx(req);
    struct crypto_aead *aead = crypto_aead_reqtfm(req);
    unsigned int authsize = crypto_aead_authsize(aead);
    unsigned int cryptlen = req->cryptlen - authsize;

    if (!err) {
        err = crypto_ccm_auth(req, req->dst, cryptlen);
        if (!err && memcmp(pctx->auth_tag, pctx->odata, authsize))
            err = -EBADMSG;
    }
    aead_request_complete(req, err);
}

static int crypto_ccm_decrypt(struct aead_request *req)
{
    struct crypto_aead *aead = crypto_aead_reqtfm(req);
    struct crypto_ccm_ctx *ctx = crypto_aead_ctx(aead);
    struct crypto_ccm_req_priv_ctx *pctx = crypto_ccm_reqctx(req);
    struct ablkcipher_request *abreq = &pctx->abreq;
    struct scatterlist *dst;
    unsigned int authsize = crypto_aead_authsize(aead);
    unsigned int cryptlen = req->cryptlen;
    u8 *authtag = pctx->auth_tag;
    u8 *odata = pctx->odata;
    u8 *iv = req->iv;
    int err;

    if (cryptlen < authsize)
        return -EINVAL;
    cryptlen -= authsize;

    err = crypto_ccm_check_iv(iv);
    if (err)
        return err;

    pctx->flags = aead_request_flags(req);

    scatterwalk_map_and_copy(authtag, req->src, cryptlen, authsize, 0);

    memset(iv + 15 - iv[0], 0, iv[0] + 1);

    sg_init_table(pctx->src, 2);
    sg_set_buf(pctx->src, authtag, 16);
    scatterwalk_sg_chain(pctx->src, 2, req->src);

    dst = pctx->src;
    if (req->src != req->dst) {
        sg_init_table(pctx->dst, 2);
        sg_set_buf(pctx->dst, authtag, 16);
        scatterwalk_sg_chain(pctx->dst, 2, req->dst);
        dst = pctx->dst;
    }

    ablkcipher_request_set_tfm(abreq, ctx->ctr);
    ablkcipher_request_set_callback(abreq, pctx->flags,
                    crypto_ccm_decrypt_done, req);
    ablkcipher_request_set_crypt(abreq, pctx->src, dst, cryptlen + 16, iv);
    err = crypto_ablkcipher_decrypt(abreq);
    if (err)
        return err;

    err = crypto_ccm_auth(req, req->dst, cryptlen);
    if (err)
        return err;

    /* verify */
    if (memcmp(authtag, odata, authsize))
        return -EBADMSG;

    return err;
}

static int crypto_ccm_init_tfm(struct crypto_tfm *tfm)
{
    struct crypto_instance *inst = (void *)tfm->__crt_alg;
    struct ccm_instance_ctx *ictx = crypto_instance_ctx(inst);
    struct crypto_ccm_ctx *ctx = crypto_tfm_ctx(tfm);
    struct crypto_cipher *cipher;
    struct crypto_ablkcipher *ctr;
    unsigned long align;
    int err;

    cipher = crypto_spawn_cipher(&ictx->cipher);
    if (IS_ERR(cipher))
        return PTR_ERR(cipher);

    ctr = crypto_spawn_skcipher(&ictx->ctr);
    err = PTR_ERR(ctr);
    if (IS_ERR(ctr))
        goto err_free_cipher;

    ctx->cipher = cipher;
    ctx->ctr = ctr;

    align = crypto_tfm_alg_alignmask(tfm);
    align &= ~(crypto_tfm_ctx_alignment() - 1);
    tfm->crt_aead.reqsize = align +
                sizeof(struct crypto_ccm_req_priv_ctx) +
                crypto_ablkcipher_reqsize(ctr);

    return 0;

err_free_cipher:
    crypto_free_cipher(cipher);
    return err;
}

static void crypto_ccm_exit_tfm(struct crypto_tfm *tfm)
{
    struct crypto_ccm_ctx *ctx = crypto_tfm_ctx(tfm);

    crypto_free_cipher(ctx->cipher);
    crypto_free_ablkcipher(ctx->ctr);
}

static struct crypto_instance *crypto_ccm_alloc_common(struct rtattr **tb,
                               const char *full_name,
                               const char *ctr_name,
                               const char *cipher_name)
{
    struct crypto_attr_type *algt;
    struct crypto_instance *inst;
    struct crypto_alg *ctr;
    struct crypto_alg *cipher;
    struct ccm_instance_ctx *ictx;
    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_AEAD) & algt->mask)
        return ERR_PTR(-EINVAL);

    cipher = crypto_alg_mod_lookup(cipher_name,  CRYPTO_ALG_TYPE_CIPHER,
                       CRYPTO_ALG_TYPE_MASK);
    err = PTR_ERR(cipher);
    if (IS_ERR(cipher))
        return ERR_PTR(err);

    err = -EINVAL;
    if (cipher->cra_blocksize != 16)
        goto out_put_cipher;

    inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL);
    err = -ENOMEM;
    if (!inst)
        goto out_put_cipher;

    ictx = crypto_instance_ctx(inst);

    err = crypto_init_spawn(&ictx->cipher, cipher, inst,
                CRYPTO_ALG_TYPE_MASK);
    if (err)
        goto err_free_inst;

    crypto_set_skcipher_spawn(&ictx->ctr, inst);
    err = crypto_grab_skcipher(&ictx->ctr, ctr_name, 0,
                   crypto_requires_sync(algt->type,
                            algt->mask));
    if (err)
        goto err_drop_cipher;

    ctr = crypto_skcipher_spawn_alg(&ictx->ctr);

    /* Not a stream cipher? */
    err = -EINVAL;
    if (ctr->cra_blocksize != 1)
        goto err_drop_ctr;

    /* We want the real thing! */
    if (ctr->cra_ablkcipher.ivsize != 16)
        goto err_drop_ctr;

    err = -ENAMETOOLONG;
    if (snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
             "ccm_base(%s,%s)", ctr->cra_driver_name,
             cipher->cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
        goto err_drop_ctr;

    memcpy(inst->alg.cra_name, full_name, CRYPTO_MAX_ALG_NAME);

    inst->alg.cra_flags = CRYPTO_ALG_TYPE_AEAD;
    inst->alg.cra_flags |= ctr->cra_flags & CRYPTO_ALG_ASYNC;
    inst->alg.cra_priority = cipher->cra_priority + ctr->cra_priority;
    inst->alg.cra_blocksize = 1;
    inst->alg.cra_alignmask = cipher->cra_alignmask | ctr->cra_alignmask |
                  (__alignof__(u32) - 1);
    inst->alg.cra_type = &crypto_aead_type;
    inst->alg.cra_aead.ivsize = 16;
    inst->alg.cra_aead.maxauthsize = 16;
    inst->alg.cra_ctxsize = sizeof(struct crypto_ccm_ctx);
    inst->alg.cra_init = crypto_ccm_init_tfm;
    inst->alg.cra_exit = crypto_ccm_exit_tfm;
    inst->alg.cra_aead.setkey = crypto_ccm_setkey;
    inst->alg.cra_aead.setauthsize = crypto_ccm_setauthsize;
    inst->alg.cra_aead.encrypt = crypto_ccm_encrypt;
    inst->alg.cra_aead.decrypt = crypto_ccm_decrypt;

out:
    crypto_mod_put(cipher);
    return inst;

err_drop_ctr:
    crypto_drop_skcipher(&ictx->ctr);
err_drop_cipher:
    crypto_drop_spawn(&ictx->cipher);
err_free_inst:
    kfree(inst);
out_put_cipher:
    inst = ERR_PTR(err);
    goto out;
}

static struct crypto_instance *crypto_ccm_alloc(struct rtattr **tb)
{
    int err;
    const char *cipher_name;
    char ctr_name[CRYPTO_MAX_ALG_NAME];
    char full_name[CRYPTO_MAX_ALG_NAME];

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

    if (snprintf(ctr_name, CRYPTO_MAX_ALG_NAME, "ctr(%s)",
             cipher_name) >= CRYPTO_MAX_ALG_NAME)
        return ERR_PTR(-ENAMETOOLONG);

    if (snprintf(full_name, CRYPTO_MAX_ALG_NAME, "ccm(%s)", cipher_name) >=
        CRYPTO_MAX_ALG_NAME)
        return ERR_PTR(-ENAMETOOLONG);

    return crypto_ccm_alloc_common(tb, full_name, ctr_name, cipher_name);
}

static void crypto_ccm_free(struct crypto_instance *inst)
{
    struct ccm_instance_ctx *ctx = crypto_instance_ctx(inst);

    crypto_drop_spawn(&ctx->cipher);
    crypto_drop_skcipher(&ctx->ctr);
    kfree(inst);
}

static struct crypto_template crypto_ccm_tmpl = {
    .name = "ccm",
    .alloc = crypto_ccm_alloc,
    .free = crypto_ccm_free,
    .module = THIS_MODULE,
};

static struct crypto_instance *crypto_ccm_base_alloc(struct rtattr **tb)
{
    int err;
    const char *ctr_name;
    const char *cipher_name;
    char full_name[CRYPTO_MAX_ALG_NAME];

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

    cipher_name = crypto_attr_alg_name(tb[2]);
    err = PTR_ERR(cipher_name);
    if (IS_ERR(cipher_name))
        return ERR_PTR(err);

    if (snprintf(full_name, CRYPTO_MAX_ALG_NAME, "ccm_base(%s,%s)",
             ctr_name, cipher_name) >= CRYPTO_MAX_ALG_NAME)
        return ERR_PTR(-ENAMETOOLONG);

    return crypto_ccm_alloc_common(tb, full_name, ctr_name, cipher_name);
}

static struct crypto_template crypto_ccm_base_tmpl = {
    .name = "ccm_base",
    .alloc = crypto_ccm_base_alloc,
    .free = crypto_ccm_free,
    .module = THIS_MODULE,
};

static int crypto_rfc4309_setkey(struct crypto_aead *parent, const u8 *key,
                 unsigned int keylen)
{
    struct crypto_rfc4309_ctx *ctx = crypto_aead_ctx(parent);
    struct crypto_aead *child = ctx->child;
    int err;

    if (keylen < 3)
        return -EINVAL;

    keylen -= 3;
    memcpy(ctx->nonce, key + keylen, 3);

    crypto_aead_clear_flags(child, CRYPTO_TFM_REQ_MASK);
    crypto_aead_set_flags(child, crypto_aead_get_flags(parent) &
                     CRYPTO_TFM_REQ_MASK);
    err = crypto_aead_setkey(child, key, keylen);
    crypto_aead_set_flags(parent, crypto_aead_get_flags(child) &
                      CRYPTO_TFM_RES_MASK);

    return err;
}

static int crypto_rfc4309_setauthsize(struct crypto_aead *parent,
                      unsigned int authsize)
{
    struct crypto_rfc4309_ctx *ctx = crypto_aead_ctx(parent);

    switch (authsize) {
    case 8:
    case 12:
    case 16:
        break;
    default:
        return -EINVAL;
    }

    return crypto_aead_setauthsize(ctx->child, authsize);
}

static struct aead_request *crypto_rfc4309_crypt(struct aead_request *req)
{
    struct aead_request *subreq = aead_request_ctx(req);
    struct crypto_aead *aead = crypto_aead_reqtfm(req);
    struct crypto_rfc4309_ctx *ctx = crypto_aead_ctx(aead);
    struct crypto_aead *child = ctx->child;
    u8 *iv = PTR_ALIGN((u8 *)(subreq + 1) + crypto_aead_reqsize(child),
               crypto_aead_alignmask(child) + 1);

    /* L' */
    iv[0] = 3;

    memcpy(iv + 1, ctx->nonce, 3);
    memcpy(iv + 4, req->iv, 8);

    aead_request_set_tfm(subreq, child);
    aead_request_set_callback(subreq, req->base.flags, req->base.complete,
                  req->base.data);
    aead_request_set_crypt(subreq, req->src, req->dst, req->cryptlen, iv);
    aead_request_set_assoc(subreq, req->assoc, req->assoclen);

    return subreq;
}

static int crypto_rfc4309_encrypt(struct aead_request *req)
{
    req = crypto_rfc4309_crypt(req);

    return crypto_aead_encrypt(req);
}

static int crypto_rfc4309_decrypt(struct aead_request *req)
{
    req = crypto_rfc4309_crypt(req);

    return crypto_aead_decrypt(req);
}

static int crypto_rfc4309_init_tfm(struct crypto_tfm *tfm)
{
    struct crypto_instance *inst = (void *)tfm->__crt_alg;
    struct crypto_aead_spawn *spawn = crypto_instance_ctx(inst);
    struct crypto_rfc4309_ctx *ctx = crypto_tfm_ctx(tfm);
    struct crypto_aead *aead;
    unsigned long align;

    aead = crypto_spawn_aead(spawn);
    if (IS_ERR(aead))
        return PTR_ERR(aead);

    ctx->child = aead;

    align = crypto_aead_alignmask(aead);
    align &= ~(crypto_tfm_ctx_alignment() - 1);
    tfm->crt_aead.reqsize = sizeof(struct aead_request) +
                ALIGN(crypto_aead_reqsize(aead),
                      crypto_tfm_ctx_alignment()) +
                align + 16;

    return 0;
}

static void crypto_rfc4309_exit_tfm(struct crypto_tfm *tfm)
{
    struct crypto_rfc4309_ctx *ctx = crypto_tfm_ctx(tfm);

    crypto_free_aead(ctx->child);
}

static struct crypto_instance *crypto_rfc4309_alloc(struct rtattr **tb)
{
    struct crypto_attr_type *algt;
    struct crypto_instance *inst;
    struct crypto_aead_spawn *spawn;
    struct crypto_alg *alg;
    const char *ccm_name;
    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_AEAD) & algt->mask)
        return ERR_PTR(-EINVAL);

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

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

    spawn = crypto_instance_ctx(inst);
    crypto_set_aead_spawn(spawn, inst);
    err = crypto_grab_aead(spawn, ccm_name, 0,
                   crypto_requires_sync(algt->type, algt->mask));
    if (err)
        goto out_free_inst;

    alg = crypto_aead_spawn_alg(spawn);

    err = -EINVAL;

    /* We only support 16-byte blocks. */
    if (alg->cra_aead.ivsize != 16)
        goto out_drop_alg;

    /* Not a stream cipher? */
    if (alg->cra_blocksize != 1)
        goto out_drop_alg;

    err = -ENAMETOOLONG;
    if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
             "rfc4309(%s)", alg->cra_name) >= CRYPTO_MAX_ALG_NAME ||
        snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
             "rfc4309(%s)", alg->cra_driver_name) >=
        CRYPTO_MAX_ALG_NAME)
        goto out_drop_alg;

    inst->alg.cra_flags = CRYPTO_ALG_TYPE_AEAD;
    inst->alg.cra_flags |= alg->cra_flags & CRYPTO_ALG_ASYNC;
    inst->alg.cra_priority = alg->cra_priority;
    inst->alg.cra_blocksize = 1;
    inst->alg.cra_alignmask = alg->cra_alignmask;
    inst->alg.cra_type = &crypto_nivaead_type;

    inst->alg.cra_aead.ivsize = 8;
    inst->alg.cra_aead.maxauthsize = 16;

    inst->alg.cra_ctxsize = sizeof(struct crypto_rfc4309_ctx);

    inst->alg.cra_init = crypto_rfc4309_init_tfm;
    inst->alg.cra_exit = crypto_rfc4309_exit_tfm;

    inst->alg.cra_aead.setkey = crypto_rfc4309_setkey;
    inst->alg.cra_aead.setauthsize = crypto_rfc4309_setauthsize;
    inst->alg.cra_aead.encrypt = crypto_rfc4309_encrypt;
    inst->alg.cra_aead.decrypt = crypto_rfc4309_decrypt;

    inst->alg.cra_aead.geniv = "seqiv";

out:
    return inst;

out_drop_alg:
    crypto_drop_aead(spawn);
out_free_inst:
    kfree(inst);
    inst = ERR_PTR(err);
    goto out;
}

static void crypto_rfc4309_free(struct crypto_instance *inst)
{
    crypto_drop_spawn(crypto_instance_ctx(inst));
    kfree(inst);
}

static struct crypto_template crypto_rfc4309_tmpl = {
    .name = "rfc4309",
    .alloc = crypto_rfc4309_alloc,
    .free = crypto_rfc4309_free,
    .module = THIS_MODULE,
};

static int __init crypto_ccm_module_init(void)
{
    int err;

    err = crypto_register_template(&crypto_ccm_base_tmpl);
    if (err)
        goto out;

    err = crypto_register_template(&crypto_ccm_tmpl);
    if (err)
        goto out_undo_base;

    err = crypto_register_template(&crypto_rfc4309_tmpl);
    if (err)
        goto out_undo_ccm;

out:
    return err;

out_undo_ccm:
    crypto_unregister_template(&crypto_ccm_tmpl);
out_undo_base:
    crypto_unregister_template(&crypto_ccm_base_tmpl);
    goto out;
}

static void __exit crypto_ccm_module_exit(void)
{
    crypto_unregister_template(&crypto_rfc4309_tmpl);
    crypto_unregister_template(&crypto_ccm_tmpl);
    crypto_unregister_template(&crypto_ccm_base_tmpl);
}

module_init(crypto_ccm_module_init);
module_exit(crypto_ccm_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Counter with CBC MAC");
MODULE_ALIAS("ccm_base");
MODULE_ALIAS("rfc4309");