chainiv.c

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/*
 * chainiv: Chain IV Generator
 *
 * Generate IVs simply be using the last block of the previous encryption.
 * This is mainly useful for CBC with a synchronous algorithm.
 *
 * Copyright (c) 2007 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/rng.h>
#include <crypto/crypto_wq.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/workqueue.h>

enum {
    CHAINIV_STATE_INUSE = 0,
};

struct chainiv_ctx {
    spinlock_t lock;
    char iv[];
};

struct async_chainiv_ctx {
    unsigned long state;

    spinlock_t lock;
    int err;

    struct crypto_queue queue;
    struct work_struct postponed;

    char iv[];
};

static int chainiv_givencrypt(struct skcipher_givcrypt_request *req)
{
    struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
    struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
    struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
    unsigned int ivsize;
    int err;

    ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));
    ablkcipher_request_set_callback(subreq, req->creq.base.flags &
                        ~CRYPTO_TFM_REQ_MAY_SLEEP,
                    req->creq.base.complete,
                    req->creq.base.data);
    ablkcipher_request_set_crypt(subreq, req->creq.src, req->creq.dst,
                     req->creq.nbytes, req->creq.info);

    spin_lock_bh(&ctx->lock);

    ivsize = crypto_ablkcipher_ivsize(geniv);

    memcpy(req->giv, ctx->iv, ivsize);
    memcpy(subreq->info, ctx->iv, ivsize);

    err = crypto_ablkcipher_encrypt(subreq);
    if (err)
        goto unlock;

    memcpy(ctx->iv, subreq->info, ivsize);

unlock:
    spin_unlock_bh(&ctx->lock);

    return err;
}

static int chainiv_givencrypt_first(struct skcipher_givcrypt_request *req)
{
    struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
    struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
    int err = 0;

    spin_lock_bh(&ctx->lock);
    if (crypto_ablkcipher_crt(geniv)->givencrypt !=
        chainiv_givencrypt_first)
        goto unlock;

    crypto_ablkcipher_crt(geniv)->givencrypt = chainiv_givencrypt;
    err = crypto_rng_get_bytes(crypto_default_rng, ctx->iv,
                   crypto_ablkcipher_ivsize(geniv));

unlock:
    spin_unlock_bh(&ctx->lock);

    if (err)
        return err;

    return chainiv_givencrypt(req);
}

static int chainiv_init_common(struct crypto_tfm *tfm)
{
    tfm->crt_ablkcipher.reqsize = sizeof(struct ablkcipher_request);

    return skcipher_geniv_init(tfm);
}

static int chainiv_init(struct crypto_tfm *tfm)
{
    struct chainiv_ctx *ctx = crypto_tfm_ctx(tfm);

    spin_lock_init(&ctx->lock);

    return chainiv_init_common(tfm);
}

static int async_chainiv_schedule_work(struct async_chainiv_ctx *ctx)
{
    int queued;
    int err = ctx->err;

    if (!ctx->queue.qlen) {
        smp_mb__before_clear_bit();
        clear_bit(CHAINIV_STATE_INUSE, &ctx->state);

        if (!ctx->queue.qlen ||
            test_and_set_bit(CHAINIV_STATE_INUSE, &ctx->state))
            goto out;
    }

    queued = queue_work(kcrypto_wq, &ctx->postponed);
    BUG_ON(!queued);

out:
    return err;
}

static int async_chainiv_postpone_request(struct skcipher_givcrypt_request *req)
{
    struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
    struct async_chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
    int err;

    spin_lock_bh(&ctx->lock);
    err = skcipher_enqueue_givcrypt(&ctx->queue, req);
    spin_unlock_bh(&ctx->lock);

    if (test_and_set_bit(CHAINIV_STATE_INUSE, &ctx->state))
        return err;

    ctx->err = err;
    return async_chainiv_schedule_work(ctx);
}

static int async_chainiv_givencrypt_tail(struct skcipher_givcrypt_request *req)
{
    struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
    struct async_chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
    struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
    unsigned int ivsize = crypto_ablkcipher_ivsize(geniv);

    memcpy(req->giv, ctx->iv, ivsize);
    memcpy(subreq->info, ctx->iv, ivsize);

    ctx->err = crypto_ablkcipher_encrypt(subreq);
    if (ctx->err)
        goto out;

    memcpy(ctx->iv, subreq->info, ivsize);

out:
    return async_chainiv_schedule_work(ctx);
}

static int async_chainiv_givencrypt(struct skcipher_givcrypt_request *req)
{
    struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
    struct async_chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
    struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);

    ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));
    ablkcipher_request_set_callback(subreq, req->creq.base.flags,
                    req->creq.base.complete,
                    req->creq.base.data);
    ablkcipher_request_set_crypt(subreq, req->creq.src, req->creq.dst,
                     req->creq.nbytes, req->creq.info);

    if (test_and_set_bit(CHAINIV_STATE_INUSE, &ctx->state))
        goto postpone;

    if (ctx->queue.qlen) {
        clear_bit(CHAINIV_STATE_INUSE, &ctx->state);
        goto postpone;
    }

    return async_chainiv_givencrypt_tail(req);

postpone:
    return async_chainiv_postpone_request(req);
}

static int async_chainiv_givencrypt_first(struct skcipher_givcrypt_request *req)
{
    struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
    struct async_chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
    int err = 0;

    if (test_and_set_bit(CHAINIV_STATE_INUSE, &ctx->state))
        goto out;

    if (crypto_ablkcipher_crt(geniv)->givencrypt !=
        async_chainiv_givencrypt_first)
        goto unlock;

    crypto_ablkcipher_crt(geniv)->givencrypt = async_chainiv_givencrypt;
    err = crypto_rng_get_bytes(crypto_default_rng, ctx->iv,
                   crypto_ablkcipher_ivsize(geniv));

unlock:
    clear_bit(CHAINIV_STATE_INUSE, &ctx->state);

    if (err)
        return err;

out:
    return async_chainiv_givencrypt(req);
}

static void async_chainiv_do_postponed(struct work_struct *work)
{
    struct async_chainiv_ctx *ctx = container_of(work,
                             struct async_chainiv_ctx,
                             postponed);
    struct skcipher_givcrypt_request *req;
    struct ablkcipher_request *subreq;
    int err;

    /* Only handle one request at a time to avoid hogging keventd. */
    spin_lock_bh(&ctx->lock);
    req = skcipher_dequeue_givcrypt(&ctx->queue);
    spin_unlock_bh(&ctx->lock);

    if (!req) {
        async_chainiv_schedule_work(ctx);
        return;
    }

    subreq = skcipher_givcrypt_reqctx(req);
    subreq->base.flags |= CRYPTO_TFM_REQ_MAY_SLEEP;

    err = async_chainiv_givencrypt_tail(req);

    local_bh_disable();
    skcipher_givcrypt_complete(req, err);
    local_bh_enable();
}

static int async_chainiv_init(struct crypto_tfm *tfm)
{
    struct async_chainiv_ctx *ctx = crypto_tfm_ctx(tfm);

    spin_lock_init(&ctx->lock);

    crypto_init_queue(&ctx->queue, 100);
    INIT_WORK(&ctx->postponed, async_chainiv_do_postponed);

    return chainiv_init_common(tfm);
}

static void async_chainiv_exit(struct crypto_tfm *tfm)
{
    struct async_chainiv_ctx *ctx = crypto_tfm_ctx(tfm);

    BUG_ON(test_bit(CHAINIV_STATE_INUSE, &ctx->state) || ctx->queue.qlen);

    skcipher_geniv_exit(tfm);
}

static struct crypto_template chainiv_tmpl;

static struct crypto_instance *chainiv_alloc(struct rtattr **tb)
{
    struct crypto_attr_type *algt;
    struct crypto_instance *inst;
    int err;

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

    err = crypto_get_default_rng();
    if (err)
        return ERR_PTR(err);

    inst = skcipher_geniv_alloc(&chainiv_tmpl, tb, 0, 0);
    if (IS_ERR(inst))
        goto put_rng;

    inst->alg.cra_ablkcipher.givencrypt = chainiv_givencrypt_first;

    inst->alg.cra_init = chainiv_init;
    inst->alg.cra_exit = skcipher_geniv_exit;

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

    if (!crypto_requires_sync(algt->type, algt->mask)) {
        inst->alg.cra_flags |= CRYPTO_ALG_ASYNC;

        inst->alg.cra_ablkcipher.givencrypt =
            async_chainiv_givencrypt_first;

        inst->alg.cra_init = async_chainiv_init;
        inst->alg.cra_exit = async_chainiv_exit;

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

    inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize;

out:
    return inst;

put_rng:
    crypto_put_default_rng();
    goto out;
}

static void chainiv_free(struct crypto_instance *inst)
{
    skcipher_geniv_free(inst);
    crypto_put_default_rng();
}

static struct crypto_template chainiv_tmpl = {
    .name = "chainiv",
    .alloc = chainiv_alloc,
    .free = chainiv_free,
    .module = THIS_MODULE,
};

static int __init chainiv_module_init(void)
{
    return crypto_register_template(&chainiv_tmpl);
}

static void chainiv_module_exit(void)
{
    crypto_unregister_template(&chainiv_tmpl);
}

module_init(chainiv_module_init);
module_exit(chainiv_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Chain IV Generator");