ctr.c

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/*
 * CTR: Counter mode
 *
 * (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/algapi.h>
#include <crypto/ctr.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>

struct crypto_ctr_ctx {
    struct crypto_cipher *child;
};

struct crypto_rfc3686_ctx {
    struct crypto_blkcipher *child;
    u8 nonce[CTR_RFC3686_NONCE_SIZE];
};

static int crypto_ctr_setkey(struct crypto_tfm *parent, const u8 *key,
                 unsigned int keylen)
{
    struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(parent);
    struct crypto_cipher *child = ctx->child;
    int err;

    crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
    crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
                CRYPTO_TFM_REQ_MASK);
    err = crypto_cipher_setkey(child, key, keylen);
    crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
                 CRYPTO_TFM_RES_MASK);

    return err;
}

static void crypto_ctr_crypt_final(struct blkcipher_walk *walk,
                   struct crypto_cipher *tfm)
{
    unsigned int bsize = crypto_cipher_blocksize(tfm);
    unsigned long alignmask = crypto_cipher_alignmask(tfm);
    u8 *ctrblk = walk->iv;
    u8 tmp[bsize + alignmask];
    u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
    u8 *src = walk->src.virt.addr;
    u8 *dst = walk->dst.virt.addr;
    unsigned int nbytes = walk->nbytes;

    crypto_cipher_encrypt_one(tfm, keystream, ctrblk);
    crypto_xor(keystream, src, nbytes);
    memcpy(dst, keystream, nbytes);

    crypto_inc(ctrblk, bsize);
}

static int crypto_ctr_crypt_segment(struct blkcipher_walk *walk,
                    struct crypto_cipher *tfm)
{
    void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
           crypto_cipher_alg(tfm)->cia_encrypt;
    unsigned int bsize = crypto_cipher_blocksize(tfm);
    u8 *ctrblk = walk->iv;
    u8 *src = walk->src.virt.addr;
    u8 *dst = walk->dst.virt.addr;
    unsigned int nbytes = walk->nbytes;

    do {
        /* create keystream */
        fn(crypto_cipher_tfm(tfm), dst, ctrblk);
        crypto_xor(dst, src, bsize);

        /* increment counter in counterblock */
        crypto_inc(ctrblk, bsize);

        src += bsize;
        dst += bsize;
    } while ((nbytes -= bsize) >= bsize);

    return nbytes;
}

static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk,
                    struct crypto_cipher *tfm)
{
    void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
           crypto_cipher_alg(tfm)->cia_encrypt;
    unsigned int bsize = crypto_cipher_blocksize(tfm);
    unsigned long alignmask = crypto_cipher_alignmask(tfm);
    unsigned int nbytes = walk->nbytes;
    u8 *ctrblk = walk->iv;
    u8 *src = walk->src.virt.addr;
    u8 tmp[bsize + alignmask];
    u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);

    do {
        /* create keystream */
        fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
        crypto_xor(src, keystream, bsize);

        /* increment counter in counterblock */
        crypto_inc(ctrblk, bsize);

        src += bsize;
    } while ((nbytes -= bsize) >= bsize);

    return nbytes;
}

static int crypto_ctr_crypt(struct blkcipher_desc *desc,
                  struct scatterlist *dst, struct scatterlist *src,
                  unsigned int nbytes)
{
    struct blkcipher_walk walk;
    struct crypto_blkcipher *tfm = desc->tfm;
    struct crypto_ctr_ctx *ctx = crypto_blkcipher_ctx(tfm);
    struct crypto_cipher *child = ctx->child;
    unsigned int bsize = crypto_cipher_blocksize(child);
    int err;

    blkcipher_walk_init(&walk, dst, src, nbytes);
    err = blkcipher_walk_virt_block(desc, &walk, bsize);

    while (walk.nbytes >= bsize) {
        if (walk.src.virt.addr == walk.dst.virt.addr)
            nbytes = crypto_ctr_crypt_inplace(&walk, child);
        else
            nbytes = crypto_ctr_crypt_segment(&walk, child);

        err = blkcipher_walk_done(desc, &walk, nbytes);
    }

    if (walk.nbytes) {
        crypto_ctr_crypt_final(&walk, child);
        err = blkcipher_walk_done(desc, &walk, 0);
    }

    return err;
}

static int crypto_ctr_init_tfm(struct crypto_tfm *tfm)
{
    struct crypto_instance *inst = (void *)tfm->__crt_alg;
    struct crypto_spawn *spawn = crypto_instance_ctx(inst);
    struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
    struct crypto_cipher *cipher;

    cipher = crypto_spawn_cipher(spawn);
    if (IS_ERR(cipher))
        return PTR_ERR(cipher);

    ctx->child = cipher;

    return 0;
}

static void crypto_ctr_exit_tfm(struct crypto_tfm *tfm)
{
    struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);

    crypto_free_cipher(ctx->child);
}

static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
{
    struct crypto_instance *inst;
    struct crypto_alg *alg;
    int err;

    err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
    if (err)
        return ERR_PTR(err);

    alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
                  CRYPTO_ALG_TYPE_MASK);
    if (IS_ERR(alg))
        return ERR_CAST(alg);

    /* Block size must be >= 4 bytes. */
    err = -EINVAL;
    if (alg->cra_blocksize < 4)
        goto out_put_alg;

    /* If this is false we'd fail the alignment of crypto_inc. */
    if (alg->cra_blocksize % 4)
        goto out_put_alg;

    inst = crypto_alloc_instance("ctr", alg);
    if (IS_ERR(inst))
        goto out;

    inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
    inst->alg.cra_priority = alg->cra_priority;
    inst->alg.cra_blocksize = 1;
    inst->alg.cra_alignmask = alg->cra_alignmask | (__alignof__(u32) - 1);
    inst->alg.cra_type = &crypto_blkcipher_type;

    inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
    inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
    inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize;

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

    inst->alg.cra_init = crypto_ctr_init_tfm;
    inst->alg.cra_exit = crypto_ctr_exit_tfm;

    inst->alg.cra_blkcipher.setkey = crypto_ctr_setkey;
    inst->alg.cra_blkcipher.encrypt = crypto_ctr_crypt;
    inst->alg.cra_blkcipher.decrypt = crypto_ctr_crypt;

    inst->alg.cra_blkcipher.geniv = "chainiv";

out:
    crypto_mod_put(alg);
    return inst;

out_put_alg:
    inst = ERR_PTR(err);
    goto out;
}

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

static struct crypto_template crypto_ctr_tmpl = {
    .name = "ctr",
    .alloc = crypto_ctr_alloc,
    .free = crypto_ctr_free,
    .module = THIS_MODULE,
};

static int crypto_rfc3686_setkey(struct crypto_tfm *parent, const u8 *key,
                 unsigned int keylen)
{
    struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(parent);
    struct crypto_blkcipher *child = ctx->child;
    int err;

    /* the nonce is stored in bytes at end of key */
    if (keylen < CTR_RFC3686_NONCE_SIZE)
        return -EINVAL;

    memcpy(ctx->nonce, key + (keylen - CTR_RFC3686_NONCE_SIZE),
           CTR_RFC3686_NONCE_SIZE);

    keylen -= CTR_RFC3686_NONCE_SIZE;

    crypto_blkcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
    crypto_blkcipher_set_flags(child, crypto_tfm_get_flags(parent) &
                      CRYPTO_TFM_REQ_MASK);
    err = crypto_blkcipher_setkey(child, key, keylen);
    crypto_tfm_set_flags(parent, crypto_blkcipher_get_flags(child) &
                     CRYPTO_TFM_RES_MASK);

    return err;
}

static int crypto_rfc3686_crypt(struct blkcipher_desc *desc,
                struct scatterlist *dst,
                struct scatterlist *src, unsigned int nbytes)
{
    struct crypto_blkcipher *tfm = desc->tfm;
    struct crypto_rfc3686_ctx *ctx = crypto_blkcipher_ctx(tfm);
    struct crypto_blkcipher *child = ctx->child;
    unsigned long alignmask = crypto_blkcipher_alignmask(tfm);
    u8 ivblk[CTR_RFC3686_BLOCK_SIZE + alignmask];
    u8 *iv = PTR_ALIGN(ivblk + 0, alignmask + 1);
    u8 *info = desc->info;
    int err;

    /* set up counter block */
    memcpy(iv, ctx->nonce, CTR_RFC3686_NONCE_SIZE);
    memcpy(iv + CTR_RFC3686_NONCE_SIZE, info, CTR_RFC3686_IV_SIZE);

    /* initialize counter portion of counter block */
    *(__be32 *)(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =
        cpu_to_be32(1);

    desc->tfm = child;
    desc->info = iv;
    err = crypto_blkcipher_encrypt_iv(desc, dst, src, nbytes);
    desc->tfm = tfm;
    desc->info = info;

    return err;
}

static int crypto_rfc3686_init_tfm(struct crypto_tfm *tfm)
{
    struct crypto_instance *inst = (void *)tfm->__crt_alg;
    struct crypto_spawn *spawn = crypto_instance_ctx(inst);
    struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(tfm);
    struct crypto_blkcipher *cipher;

    cipher = crypto_spawn_blkcipher(spawn);
    if (IS_ERR(cipher))
        return PTR_ERR(cipher);

    ctx->child = cipher;

    return 0;
}

static void crypto_rfc3686_exit_tfm(struct crypto_tfm *tfm)
{
    struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(tfm);

    crypto_free_blkcipher(ctx->child);
}

static struct crypto_instance *crypto_rfc3686_alloc(struct rtattr **tb)
{
    struct crypto_instance *inst;
    struct crypto_alg *alg;
    int err;

    err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
    if (err)
        return ERR_PTR(err);

    alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_BLKCIPHER,
                  CRYPTO_ALG_TYPE_MASK);
    err = PTR_ERR(alg);
    if (IS_ERR(alg))
        return ERR_PTR(err);

    /* We only support 16-byte blocks. */
    err = -EINVAL;
    if (alg->cra_blkcipher.ivsize != CTR_RFC3686_BLOCK_SIZE)
        goto out_put_alg;

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

    inst = crypto_alloc_instance("rfc3686", alg);
    if (IS_ERR(inst))
        goto out;

    inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
    inst->alg.cra_priority = alg->cra_priority;
    inst->alg.cra_blocksize = 1;
    inst->alg.cra_alignmask = alg->cra_alignmask;
    inst->alg.cra_type = &crypto_blkcipher_type;

    inst->alg.cra_blkcipher.ivsize = CTR_RFC3686_IV_SIZE;
    inst->alg.cra_blkcipher.min_keysize = alg->cra_blkcipher.min_keysize
                          + CTR_RFC3686_NONCE_SIZE;
    inst->alg.cra_blkcipher.max_keysize = alg->cra_blkcipher.max_keysize
                          + CTR_RFC3686_NONCE_SIZE;

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

    inst->alg.cra_ctxsize = sizeof(struct crypto_rfc3686_ctx);

    inst->alg.cra_init = crypto_rfc3686_init_tfm;
    inst->alg.cra_exit = crypto_rfc3686_exit_tfm;

    inst->alg.cra_blkcipher.setkey = crypto_rfc3686_setkey;
    inst->alg.cra_blkcipher.encrypt = crypto_rfc3686_crypt;
    inst->alg.cra_blkcipher.decrypt = crypto_rfc3686_crypt;

out:
    crypto_mod_put(alg);
    return inst;

out_put_alg:
    inst = ERR_PTR(err);
    goto out;
}

static struct crypto_template crypto_rfc3686_tmpl = {
    .name = "rfc3686",
    .alloc = crypto_rfc3686_alloc,
    .free = crypto_ctr_free,
    .module = THIS_MODULE,
};

static int __init crypto_ctr_module_init(void)
{
    int err;

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

    err = crypto_register_template(&crypto_rfc3686_tmpl);
    if (err)
        goto out_drop_ctr;

out:
    return err;

out_drop_ctr:
    crypto_unregister_template(&crypto_ctr_tmpl);
    goto out;
}

static void __exit crypto_ctr_module_exit(void)
{
    crypto_unregister_template(&crypto_rfc3686_tmpl);
    crypto_unregister_template(&crypto_ctr_tmpl);
}

module_init(crypto_ctr_module_init);
module_exit(crypto_ctr_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("CTR Counter block mode");
MODULE_ALIAS("rfc3686");