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authenc.c

/*
 * Authenc: Simple AEAD wrapper for IPsec
 *
 * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
 *
 * 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 <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/spinlock.h>

#include "scatterwalk.h"

struct authenc_instance_ctx {
      struct crypto_spawn auth;
      struct crypto_spawn enc;

      unsigned int authsize;
      unsigned int enckeylen;
};

struct crypto_authenc_ctx {
      spinlock_t auth_lock;
      struct crypto_hash *auth;
      struct crypto_ablkcipher *enc;
};

static int crypto_authenc_setkey(struct crypto_aead *authenc, const u8 *key,
                         unsigned int keylen)
{
      struct authenc_instance_ctx *ictx =
            crypto_instance_ctx(crypto_aead_alg_instance(authenc));
      unsigned int enckeylen = ictx->enckeylen;
      unsigned int authkeylen;
      struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
      struct crypto_hash *auth = ctx->auth;
      struct crypto_ablkcipher *enc = ctx->enc;
      int err = -EINVAL;

      if (keylen < enckeylen) {
            crypto_aead_set_flags(authenc, CRYPTO_TFM_RES_BAD_KEY_LEN);
            goto out;
      }
      authkeylen = keylen - enckeylen;

      crypto_hash_clear_flags(auth, CRYPTO_TFM_REQ_MASK);
      crypto_hash_set_flags(auth, crypto_aead_get_flags(authenc) &
                            CRYPTO_TFM_REQ_MASK);
      err = crypto_hash_setkey(auth, key, authkeylen);
      crypto_aead_set_flags(authenc, crypto_hash_get_flags(auth) &
                               CRYPTO_TFM_RES_MASK);

      if (err)
            goto out;

      crypto_ablkcipher_clear_flags(enc, CRYPTO_TFM_REQ_MASK);
      crypto_ablkcipher_set_flags(enc, crypto_aead_get_flags(authenc) &
                               CRYPTO_TFM_REQ_MASK);
      err = crypto_ablkcipher_setkey(enc, key + authkeylen, enckeylen);
      crypto_aead_set_flags(authenc, crypto_ablkcipher_get_flags(enc) &
                               CRYPTO_TFM_RES_MASK);

out:
      return err;
}

static int crypto_authenc_hash(struct aead_request *req)
{
      struct crypto_aead *authenc = crypto_aead_reqtfm(req);
      struct authenc_instance_ctx *ictx =
            crypto_instance_ctx(crypto_aead_alg_instance(authenc));
      struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
      struct crypto_hash *auth = ctx->auth;
      struct hash_desc desc = {
            .tfm = auth,
      };
      u8 *hash = aead_request_ctx(req);
      struct scatterlist *dst = req->dst;
      unsigned int cryptlen = req->cryptlen;
      int err;

      hash = (u8 *)ALIGN((unsigned long)hash + crypto_hash_alignmask(auth), 
                     crypto_hash_alignmask(auth) + 1);

      spin_lock_bh(&ctx->auth_lock);
      err = crypto_hash_init(&desc);
      if (err)
            goto auth_unlock;

      err = crypto_hash_update(&desc, req->assoc, req->assoclen);
      if (err)
            goto auth_unlock;

      err = crypto_hash_update(&desc, dst, cryptlen);
      if (err)
            goto auth_unlock;

      err = crypto_hash_final(&desc, hash);
auth_unlock:
      spin_unlock_bh(&ctx->auth_lock);

      if (err)
            return err;

      scatterwalk_map_and_copy(hash, dst, cryptlen, ictx->authsize, 1);
      return 0;
}

static void crypto_authenc_encrypt_done(struct crypto_async_request *req,
                              int err)
{
      if (!err)
            err = crypto_authenc_hash(req->data);

      aead_request_complete(req->data, err);
}

static int crypto_authenc_encrypt(struct aead_request *req)
{
      struct crypto_aead *authenc = crypto_aead_reqtfm(req);
      struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
      struct ablkcipher_request *abreq = aead_request_ctx(req);
      int err;

      ablkcipher_request_set_tfm(abreq, ctx->enc);
      ablkcipher_request_set_callback(abreq, aead_request_flags(req),
                              crypto_authenc_encrypt_done, req);
      ablkcipher_request_set_crypt(abreq, req->src, req->dst, req->cryptlen,
                             req->iv);

      err = crypto_ablkcipher_encrypt(abreq);
      if (err)
            return err;

      return crypto_authenc_hash(req);
}

static int crypto_authenc_verify(struct aead_request *req)
{
      struct crypto_aead *authenc = crypto_aead_reqtfm(req);
      struct authenc_instance_ctx *ictx =
            crypto_instance_ctx(crypto_aead_alg_instance(authenc));
      struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
      struct crypto_hash *auth = ctx->auth;
      struct hash_desc desc = {
            .tfm = auth,
            .flags = aead_request_flags(req),
      };
      u8 *ohash = aead_request_ctx(req);
      u8 *ihash;
      struct scatterlist *src = req->src;
      unsigned int cryptlen = req->cryptlen;
      unsigned int authsize;
      int err;

      ohash = (u8 *)ALIGN((unsigned long)ohash + crypto_hash_alignmask(auth), 
                      crypto_hash_alignmask(auth) + 1);
      ihash = ohash + crypto_hash_digestsize(auth);

      spin_lock_bh(&ctx->auth_lock);
      err = crypto_hash_init(&desc);
      if (err)
            goto auth_unlock;

      err = crypto_hash_update(&desc, req->assoc, req->assoclen);
      if (err)
            goto auth_unlock;

      err = crypto_hash_update(&desc, src, cryptlen);
      if (err)
            goto auth_unlock;

      err = crypto_hash_final(&desc, ohash);
auth_unlock:
      spin_unlock_bh(&ctx->auth_lock);

      if (err)
            return err;

      authsize = ictx->authsize;
      scatterwalk_map_and_copy(ihash, src, cryptlen, authsize, 0);
      return memcmp(ihash, ohash, authsize) ? -EINVAL : 0;
}

static void crypto_authenc_decrypt_done(struct crypto_async_request *req,
                              int err)
{
      aead_request_complete(req->data, err);
}

static int crypto_authenc_decrypt(struct aead_request *req)
{
      struct crypto_aead *authenc = crypto_aead_reqtfm(req);
      struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
      struct ablkcipher_request *abreq = aead_request_ctx(req);
      int err;

      err = crypto_authenc_verify(req);
      if (err)
            return err;

      ablkcipher_request_set_tfm(abreq, ctx->enc);
      ablkcipher_request_set_callback(abreq, aead_request_flags(req),
                              crypto_authenc_decrypt_done, req);
      ablkcipher_request_set_crypt(abreq, req->src, req->dst, req->cryptlen,
                             req->iv);

      return crypto_ablkcipher_decrypt(abreq);
}

static int crypto_authenc_init_tfm(struct crypto_tfm *tfm)
{
      struct crypto_instance *inst = (void *)tfm->__crt_alg;
      struct authenc_instance_ctx *ictx = crypto_instance_ctx(inst);
      struct crypto_authenc_ctx *ctx = crypto_tfm_ctx(tfm);
      struct crypto_hash *auth;
      struct crypto_ablkcipher *enc;
      unsigned int digestsize;
      int err;

      auth = crypto_spawn_hash(&ictx->auth);
      if (IS_ERR(auth))
            return PTR_ERR(auth);

      err = -EINVAL;
      digestsize = crypto_hash_digestsize(auth);
      if (ictx->authsize > digestsize)
            goto err_free_hash;

      enc = crypto_spawn_ablkcipher(&ictx->enc);
      err = PTR_ERR(enc);
      if (IS_ERR(enc))
            goto err_free_hash;

      ctx->auth = auth;
      ctx->enc = enc;
      tfm->crt_aead.reqsize = max_t(unsigned int,
                              (crypto_hash_alignmask(auth) &
                               ~(crypto_tfm_ctx_alignment() - 1)) +
                              digestsize * 2,
                              sizeof(struct ablkcipher_request) +
                              crypto_ablkcipher_reqsize(enc));

      spin_lock_init(&ctx->auth_lock);

      return 0;

err_free_hash:
      crypto_free_hash(auth);
      return err;
}

static void crypto_authenc_exit_tfm(struct crypto_tfm *tfm)
{
      struct crypto_authenc_ctx *ctx = crypto_tfm_ctx(tfm);

      crypto_free_hash(ctx->auth);
      crypto_free_ablkcipher(ctx->enc);
}

static struct crypto_instance *crypto_authenc_alloc(struct rtattr **tb)
{
      struct crypto_instance *inst;
      struct crypto_alg *auth;
      struct crypto_alg *enc;
      struct authenc_instance_ctx *ctx;
      unsigned int authsize;
      unsigned int enckeylen;
      int err;

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

      auth = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_HASH,
                         CRYPTO_ALG_TYPE_HASH_MASK);
      if (IS_ERR(auth))
            return ERR_PTR(PTR_ERR(auth));

      err = crypto_attr_u32(tb[2], &authsize);
      inst = ERR_PTR(err);
      if (err)
            goto out_put_auth;

      enc = crypto_attr_alg(tb[3], CRYPTO_ALG_TYPE_BLKCIPHER,
                        CRYPTO_ALG_TYPE_MASK);
      inst = ERR_PTR(PTR_ERR(enc));
      if (IS_ERR(enc))
            goto out_put_auth;

      err = crypto_attr_u32(tb[4], &enckeylen);
      if (err)
            goto out_put_enc;

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

      err = -ENAMETOOLONG;
      if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
                 "authenc(%s,%u,%s,%u)", auth->cra_name, authsize,
                 enc->cra_name, enckeylen) >= CRYPTO_MAX_ALG_NAME)
            goto err_free_inst;

      if (snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
                 "authenc(%s,%u,%s,%u)", auth->cra_driver_name,
                 authsize, enc->cra_driver_name, enckeylen) >=
          CRYPTO_MAX_ALG_NAME)
            goto err_free_inst;

      ctx = crypto_instance_ctx(inst);
      ctx->authsize = authsize;
      ctx->enckeylen = enckeylen;

      err = crypto_init_spawn(&ctx->auth, auth, inst, CRYPTO_ALG_TYPE_MASK);
      if (err)
            goto err_free_inst;

      err = crypto_init_spawn(&ctx->enc, enc, inst, CRYPTO_ALG_TYPE_MASK);
      if (err)
            goto err_drop_auth;

      inst->alg.cra_flags = CRYPTO_ALG_TYPE_AEAD | CRYPTO_ALG_ASYNC;
      inst->alg.cra_priority = enc->cra_priority * 10 + auth->cra_priority;
      inst->alg.cra_blocksize = enc->cra_blocksize;
      inst->alg.cra_alignmask = max(auth->cra_alignmask, enc->cra_alignmask);
      inst->alg.cra_type = &crypto_aead_type;

      inst->alg.cra_aead.ivsize = enc->cra_blkcipher.ivsize;
      inst->alg.cra_aead.authsize = authsize;

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

      inst->alg.cra_init = crypto_authenc_init_tfm;
      inst->alg.cra_exit = crypto_authenc_exit_tfm;

      inst->alg.cra_aead.setkey = crypto_authenc_setkey;
      inst->alg.cra_aead.encrypt = crypto_authenc_encrypt;
      inst->alg.cra_aead.decrypt = crypto_authenc_decrypt;

out:
      crypto_mod_put(enc);
out_put_auth:
      crypto_mod_put(auth);
      return inst;

err_drop_auth:
      crypto_drop_spawn(&ctx->auth);
err_free_inst:
      kfree(inst);
out_put_enc:
      inst = ERR_PTR(err);
      goto out;
}

static void crypto_authenc_free(struct crypto_instance *inst)
{
      struct authenc_instance_ctx *ctx = crypto_instance_ctx(inst);

      crypto_drop_spawn(&ctx->enc);
      crypto_drop_spawn(&ctx->auth);
      kfree(inst);
}

static struct crypto_template crypto_authenc_tmpl = {
      .name = "authenc",
      .alloc = crypto_authenc_alloc,
      .free = crypto_authenc_free,
      .module = THIS_MODULE,
};

static int __init crypto_authenc_module_init(void)
{
      return crypto_register_template(&crypto_authenc_tmpl);
}

static void __exit crypto_authenc_module_exit(void)
{
      crypto_unregister_template(&crypto_authenc_tmpl);
}

module_init(crypto_authenc_module_init);
module_exit(crypto_authenc_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Simple AEAD wrapper for IPsec");

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