// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * authencesn.c - AEAD wrapper for IPsec with extended sequence numbers,
 *                 derived from authenc.c
 *
 * Copyright (C) 2010 secunet Security Networks AG
 * Copyright (C) 2010 Steffen Klassert <steffen.klassert@secunet.com>
 * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
 */

#include <crypto/internal/aead.h>
#include <crypto/internal/hash.h>
#include <crypto/internal/skcipher.h>
#include <crypto/authenc.h>
#include <crypto/null.h>
#include <crypto/scatterwalk.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/rtnetlink.h>
#include <linux/slab.h>
#include <linux/spinlock.h>

struct authenc_esn_instance_ctx {
        struct crypto_ahash_spawn auth;
        struct crypto_skcipher_spawn enc;
};

struct crypto_authenc_esn_ctx {
        unsigned int reqoff;
        struct crypto_ahash *auth;
        struct crypto_skcipher *enc;
        struct crypto_sync_skcipher *null;
};

struct authenc_esn_request_ctx {
        struct scatterlist src[2];
        struct scatterlist dst[2];
        char tail[];
};

static void authenc_esn_request_complete(struct aead_request *req, int err)
{
        if (err != -EINPROGRESS)
                aead_request_complete(req, err);
}

static int crypto_authenc_esn_setauthsize(struct crypto_aead *authenc_esn,
                                          unsigned int authsize)
{
        if (authsize > 0 && authsize < 4)
                return -EINVAL;

        return 0;
}

static int crypto_authenc_esn_setkey(struct crypto_aead *authenc_esn, const u8 *key,
                                     unsigned int keylen)
{
        struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);
        struct crypto_ahash *auth = ctx->auth;
        struct crypto_skcipher *enc = ctx->enc;
        struct crypto_authenc_keys keys;
        int err = -EINVAL;

        if (crypto_authenc_extractkeys(&keys, key, keylen) != 0)
                goto out;

        crypto_ahash_clear_flags(auth, CRYPTO_TFM_REQ_MASK);
        crypto_ahash_set_flags(auth, crypto_aead_get_flags(authenc_esn) &
                                     CRYPTO_TFM_REQ_MASK);
        err = crypto_ahash_setkey(auth, keys.authkey, keys.authkeylen);
        if (err)
                goto out;

        crypto_skcipher_clear_flags(enc, CRYPTO_TFM_REQ_MASK);
        crypto_skcipher_set_flags(enc, crypto_aead_get_flags(authenc_esn) &
                                         CRYPTO_TFM_REQ_MASK);
        err = crypto_skcipher_setkey(enc, keys.enckey, keys.enckeylen);
out:
        memzero_explicit(&keys, sizeof(keys));
        return err;
}

static int crypto_authenc_esn_genicv_tail(struct aead_request *req,
                                          unsigned int flags)
{
        struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
        struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);
        u8 *hash = areq_ctx->tail;
        unsigned int authsize = crypto_aead_authsize(authenc_esn);
        unsigned int assoclen = req->assoclen;
        unsigned int cryptlen = req->cryptlen;
        struct scatterlist *dst = req->dst;
        u32 tmp[2];

        /* Move high-order bits of sequence number back. */
        scatterwalk_map_and_copy(tmp, dst, 4, 4, 0);
        scatterwalk_map_and_copy(tmp + 1, dst, assoclen + cryptlen, 4, 0);
        scatterwalk_map_and_copy(tmp, dst, 0, 8, 1);

        scatterwalk_map_and_copy(hash, dst, assoclen + cryptlen, authsize, 1);
        return 0;
}

static void authenc_esn_geniv_ahash_done(void *data, int err)
{
        struct aead_request *req = data;

        err = err ?: crypto_authenc_esn_genicv_tail(req, 0);
        aead_request_complete(req, err);
}

static int crypto_authenc_esn_genicv(struct aead_request *req,
                                     unsigned int flags)
{
        struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
        struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);
        struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);
        struct crypto_ahash *auth = ctx->auth;
        u8 *hash = areq_ctx->tail;
        struct ahash_request *ahreq = (void *)(areq_ctx->tail + ctx->reqoff);
        unsigned int authsize = crypto_aead_authsize(authenc_esn);
        unsigned int assoclen = req->assoclen;
        unsigned int cryptlen = req->cryptlen;
        struct scatterlist *dst = req->dst;
        u32 tmp[2];

        if (!authsize)
                return 0;

        /* Move high-order bits of sequence number to the end. */
        scatterwalk_map_and_copy(tmp, dst, 0, 8, 0);
        scatterwalk_map_and_copy(tmp, dst, 4, 4, 1);
        scatterwalk_map_and_copy(tmp + 1, dst, assoclen + cryptlen, 4, 1);

        sg_init_table(areq_ctx->dst, 2);
        dst = scatterwalk_ffwd(areq_ctx->dst, dst, 4);

        ahash_request_set_tfm(ahreq, auth);
        ahash_request_set_crypt(ahreq, dst, hash, assoclen + cryptlen);
        ahash_request_set_callback(ahreq, flags,
                                   authenc_esn_geniv_ahash_done, req);

        return crypto_ahash_digest(ahreq) ?:
               crypto_authenc_esn_genicv_tail(req, aead_request_flags(req));
}


static void crypto_authenc_esn_encrypt_done(void *data, int err)
{
        struct aead_request *areq = data;

        if (!err)
                err = crypto_authenc_esn_genicv(areq, 0);

        authenc_esn_request_complete(areq, err);
}

static int crypto_authenc_esn_copy(struct aead_request *req, unsigned int len)
{
        struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
        struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);
        SYNC_SKCIPHER_REQUEST_ON_STACK(skreq, ctx->null);

        skcipher_request_set_sync_tfm(skreq, ctx->null);
        skcipher_request_set_callback(skreq, aead_request_flags(req),
                                      NULL, NULL);
        skcipher_request_set_crypt(skreq, req->src, req->dst, len, NULL);

        return crypto_skcipher_encrypt(skreq);
}

static int crypto_authenc_esn_encrypt(struct aead_request *req)
{
        struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
        struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);
        struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);
        struct skcipher_request *skreq = (void *)(areq_ctx->tail +
                                                  ctx->reqoff);
        struct crypto_skcipher *enc = ctx->enc;
        unsigned int assoclen = req->assoclen;
        unsigned int cryptlen = req->cryptlen;
        struct scatterlist *src, *dst;
        int err;

        sg_init_table(areq_ctx->src, 2);
        src = scatterwalk_ffwd(areq_ctx->src, req->src, assoclen);
        dst = src;

        if (req->src != req->dst) {
                err = crypto_authenc_esn_copy(req, assoclen);
                if (err)
                        return err;

                sg_init_table(areq_ctx->dst, 2);
                dst = scatterwalk_ffwd(areq_ctx->dst, req->dst, assoclen);
        }

        skcipher_request_set_tfm(skreq, enc);
        skcipher_request_set_callback(skreq, aead_request_flags(req),
                                      crypto_authenc_esn_encrypt_done, req);
        skcipher_request_set_crypt(skreq, src, dst, cryptlen, req->iv);

        err = crypto_skcipher_encrypt(skreq);
        if (err)
                return err;

        return crypto_authenc_esn_genicv(req, aead_request_flags(req));
}

static int crypto_authenc_esn_decrypt_tail(struct aead_request *req,
                                           unsigned int flags)
{
        struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
        unsigned int authsize = crypto_aead_authsize(authenc_esn);
        struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);
        struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);
        struct skcipher_request *skreq = (void *)(areq_ctx->tail +
                                                  ctx->reqoff);
        struct crypto_ahash *auth = ctx->auth;
        u8 *ohash = areq_ctx->tail;
        unsigned int cryptlen = req->cryptlen - authsize;
        unsigned int assoclen = req->assoclen;
        struct scatterlist *dst = req->dst;
        u8 *ihash = ohash + crypto_ahash_digestsize(auth);
        u32 tmp[2];

        if (!authsize)
                goto decrypt;

        /* Move high-order bits of sequence number back. */
        scatterwalk_map_and_copy(tmp, dst, 4, 4, 0);
        scatterwalk_map_and_copy(tmp + 1, dst, assoclen + cryptlen, 4, 0);
        scatterwalk_map_and_copy(tmp, dst, 0, 8, 1);

        if (crypto_memneq(ihash, ohash, authsize))
                return -EBADMSG;

decrypt:

        sg_init_table(areq_ctx->dst, 2);
        dst = scatterwalk_ffwd(areq_ctx->dst, dst, assoclen);

        skcipher_request_set_tfm(skreq, ctx->enc);
        skcipher_request_set_callback(skreq, flags,
                                      req->base.complete, req->base.data);
        skcipher_request_set_crypt(skreq, dst, dst, cryptlen, req->iv);

        return crypto_skcipher_decrypt(skreq);
}

static void authenc_esn_verify_ahash_done(void *data, int err)
{
        struct aead_request *req = data;

        err = err ?: crypto_authenc_esn_decrypt_tail(req, 0);
        authenc_esn_request_complete(req, err);
}

static int crypto_authenc_esn_decrypt(struct aead_request *req)
{
        struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
        struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);
        struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);
        struct ahash_request *ahreq = (void *)(areq_ctx->tail + ctx->reqoff);
        unsigned int authsize = crypto_aead_authsize(authenc_esn);
        struct crypto_ahash *auth = ctx->auth;
        u8 *ohash = areq_ctx->tail;
        unsigned int assoclen = req->assoclen;
        unsigned int cryptlen = req->cryptlen;
        u8 *ihash = ohash + crypto_ahash_digestsize(auth);
        struct scatterlist *dst = req->dst;
        u32 tmp[2];
        int err;

        cryptlen -= authsize;

        if (req->src != dst) {
                err = crypto_authenc_esn_copy(req, assoclen + cryptlen);
                if (err)
                        return err;
        }

        scatterwalk_map_and_copy(ihash, req->src, assoclen + cryptlen,
                                 authsize, 0);

        if (!authsize)
                goto tail;

        /* Move high-order bits of sequence number to the end. */
        scatterwalk_map_and_copy(tmp, dst, 0, 8, 0);
        scatterwalk_map_and_copy(tmp, dst, 4, 4, 1);
        scatterwalk_map_and_copy(tmp + 1, dst, assoclen + cryptlen, 4, 1);

        sg_init_table(areq_ctx->dst, 2);
        dst = scatterwalk_ffwd(areq_ctx->dst, dst, 4);

        ahash_request_set_tfm(ahreq, auth);
        ahash_request_set_crypt(ahreq, dst, ohash, assoclen + cryptlen);
        ahash_request_set_callback(ahreq, aead_request_flags(req),
                                   authenc_esn_verify_ahash_done, req);

        err = crypto_ahash_digest(ahreq);
        if (err)
                return err;

tail:
        return crypto_authenc_esn_decrypt_tail(req, aead_request_flags(req));
}

static int crypto_authenc_esn_init_tfm(struct crypto_aead *tfm)
{
        struct aead_instance *inst = aead_alg_instance(tfm);
        struct authenc_esn_instance_ctx *ictx = aead_instance_ctx(inst);
        struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(tfm);
        struct crypto_ahash *auth;
        struct crypto_skcipher *enc;
        struct crypto_sync_skcipher *null;
        int err;

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

        enc = crypto_spawn_skcipher(&ictx->enc);
        err = PTR_ERR(enc);
        if (IS_ERR(enc))
                goto err_free_ahash;

        null = crypto_get_default_null_skcipher();
        err = PTR_ERR(null);
        if (IS_ERR(null))
                goto err_free_skcipher;

        ctx->auth = auth;
        ctx->enc = enc;
        ctx->null = null;

        ctx->reqoff = 2 * crypto_ahash_digestsize(auth);

        crypto_aead_set_reqsize(
                tfm,
                sizeof(struct authenc_esn_request_ctx) +
                ctx->reqoff +
                max_t(unsigned int,
                      crypto_ahash_reqsize(auth) +
                      sizeof(struct ahash_request),
                      sizeof(struct skcipher_request) +
                      crypto_skcipher_reqsize(enc)));

        return 0;

err_free_skcipher:
        crypto_free_skcipher(enc);
err_free_ahash:
        crypto_free_ahash(auth);
        return err;
}

static void crypto_authenc_esn_exit_tfm(struct crypto_aead *tfm)
{
        struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(tfm);

        crypto_free_ahash(ctx->auth);
        crypto_free_skcipher(ctx->enc);
        crypto_put_default_null_skcipher();
}

static void crypto_authenc_esn_free(struct aead_instance *inst)
{
        struct authenc_esn_instance_ctx *ctx = aead_instance_ctx(inst);

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

static int crypto_authenc_esn_create(struct crypto_template *tmpl,
                                     struct rtattr **tb)
{
        u32 mask;
        struct aead_instance *inst;
        struct authenc_esn_instance_ctx *ctx;
        struct skcipher_alg_common *enc;
        struct hash_alg_common *auth;
        struct crypto_alg *auth_base;
        int err;

        err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_AEAD, &mask);
        if (err)
                return err;

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

        err = crypto_grab_ahash(&ctx->auth, aead_crypto_instance(inst),
                                crypto_attr_alg_name(tb[1]), 0, mask);
        if (err)
                goto err_free_inst;
        auth = crypto_spawn_ahash_alg(&ctx->auth);
        auth_base = &auth->base;

        err = crypto_grab_skcipher(&ctx->enc, aead_crypto_instance(inst),
                                   crypto_attr_alg_name(tb[2]), 0, mask);
        if (err)
                goto err_free_inst;
        enc = crypto_spawn_skcipher_alg_common(&ctx->enc);

        err = -ENAMETOOLONG;
        if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
                     "authencesn(%s,%s)", auth_base->cra_name,
                     enc->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
                goto err_free_inst;

        if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
                     "authencesn(%s,%s)", auth_base->cra_driver_name,
                     enc->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
                goto err_free_inst;

        inst->alg.base.cra_priority = enc->base.cra_priority * 10 +
                                      auth_base->cra_priority;
        inst->alg.base.cra_blocksize = enc->base.cra_blocksize;
        inst->alg.base.cra_alignmask = enc->base.cra_alignmask;
        inst->alg.base.cra_ctxsize = sizeof(struct crypto_authenc_esn_ctx);

        inst->alg.ivsize = enc->ivsize;
        inst->alg.chunksize = enc->chunksize;
        inst->alg.maxauthsize = auth->digestsize;

        inst->alg.init = crypto_authenc_esn_init_tfm;
        inst->alg.exit = crypto_authenc_esn_exit_tfm;

        inst->alg.setkey = crypto_authenc_esn_setkey;
        inst->alg.setauthsize = crypto_authenc_esn_setauthsize;
        inst->alg.encrypt = crypto_authenc_esn_encrypt;
        inst->alg.decrypt = crypto_authenc_esn_decrypt;

        inst->free = crypto_authenc_esn_free;

        err = aead_register_instance(tmpl, inst);
        if (err) {
err_free_inst:
                crypto_authenc_esn_free(inst);
        }
        return err;
}

static struct crypto_template crypto_authenc_esn_tmpl = {
        .name = "authencesn",
        .create = crypto_authenc_esn_create,
        .module = THIS_MODULE,
};

static int __init crypto_authenc_esn_module_init(void)
{
        return crypto_register_template(&crypto_authenc_esn_tmpl);
}

static void __exit crypto_authenc_esn_module_exit(void)
{
        crypto_unregister_template(&crypto_authenc_esn_tmpl);
}

subsys_initcall(crypto_authenc_esn_module_init);
module_exit(crypto_authenc_esn_module_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Steffen Klassert <steffen.klassert@secunet.com>");
MODULE_DESCRIPTION("AEAD wrapper for IPsec with extended sequence numbers");
MODULE_ALIAS_CRYPTO("authencesn");