// SPDX-License-Identifier: GPL-2.0-or-later

  /* RSA asymmetric public-key algorithm [RFC3447]
   *
   * Copyright (c) 2015, Intel Corporation
   * Authors: Tadeusz Struk <tadeusz.struk@intel.com>

   */
  
  #include <linux/module.h>

  #include <linux/mpi.h>

  #include <crypto/internal/rsa.h>
  #include <crypto/internal/akcipher.h>
  #include <crypto/akcipher.h>

  #include <crypto/algapi.h>

  struct rsa_mpi_key {
  	MPI n;
  	MPI e;
  	MPI d;
  };

  /*
   * RSAEP function [RFC3447 sec 5.1.1]
   * c = m^e mod n;
   */

  static int _rsa_enc(const struct rsa_mpi_key *key, MPI c, MPI m)

  {
  	/* (1) Validate 0 <= m < n */
  	if (mpi_cmp_ui(m, 0) < 0 || mpi_cmp(m, key->n) >= 0)
  		return -EINVAL;
  
  	/* (2) c = m^e mod n */
  	return mpi_powm(c, m, key->e, key->n);
  }
  
  /*
   * RSADP function [RFC3447 sec 5.1.2]
   * m = c^d mod n;
   */

  static int _rsa_dec(const struct rsa_mpi_key *key, MPI m, MPI c)

  {
  	/* (1) Validate 0 <= c < n */
  	if (mpi_cmp_ui(c, 0) < 0 || mpi_cmp(c, key->n) >= 0)
  		return -EINVAL;
  
  	/* (2) m = c^d mod n */
  	return mpi_powm(m, c, key->d, key->n);
  }

  static inline struct rsa_mpi_key *rsa_get_key(struct crypto_akcipher *tfm)

  {
  	return akcipher_tfm_ctx(tfm);
  }
  
  static int rsa_enc(struct akcipher_request *req)
  {
  	struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);

  	const struct rsa_mpi_key *pkey = rsa_get_key(tfm);

  	MPI m, c = mpi_alloc(0);
  	int ret = 0;
  	int sign;
  
  	if (!c)
  		return -ENOMEM;
  
  	if (unlikely(!pkey->n || !pkey->e)) {
  		ret = -EINVAL;
  		goto err_free_c;
  	}

  	ret = -ENOMEM;
  	m = mpi_read_raw_from_sgl(req->src, req->src_len);
  	if (!m)

  		goto err_free_c;

  
  	ret = _rsa_enc(pkey, c, m);
  	if (ret)
  		goto err_free_m;

  	ret = mpi_write_to_sgl(c, req->dst, req->dst_len, &sign);

  	if (ret)
  		goto err_free_m;

  	if (sign < 0)

  		ret = -EBADMSG;

  
  err_free_m:
  	mpi_free(m);
  err_free_c:
  	mpi_free(c);
  	return ret;
  }
  
  static int rsa_dec(struct akcipher_request *req)
  {
  	struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);

  	const struct rsa_mpi_key *pkey = rsa_get_key(tfm);

  	MPI c, m = mpi_alloc(0);
  	int ret = 0;
  	int sign;
  
  	if (!m)
  		return -ENOMEM;
  
  	if (unlikely(!pkey->n || !pkey->d)) {
  		ret = -EINVAL;
  		goto err_free_m;
  	}

  	ret = -ENOMEM;
  	c = mpi_read_raw_from_sgl(req->src, req->src_len);
  	if (!c)

  		goto err_free_m;

  
  	ret = _rsa_dec(pkey, m, c);
  	if (ret)
  		goto err_free_c;

  	ret = mpi_write_to_sgl(m, req->dst, req->dst_len, &sign);

  	if (ret)
  		goto err_free_c;

  	if (sign < 0)

  		ret = -EBADMSG;

  err_free_c:
  	mpi_free(c);
  err_free_m:
  	mpi_free(m);
  	return ret;
  }

  static void rsa_free_mpi_key(struct rsa_mpi_key *key)
  {
  	mpi_free(key->d);
  	mpi_free(key->e);
  	mpi_free(key->n);
  	key->d = NULL;
  	key->e = NULL;
  	key->n = NULL;
  }

  static int rsa_check_key_length(unsigned int len)
  {
  	switch (len) {
  	case 512:
  	case 1024:
  	case 1536:
  	case 2048:
  	case 3072:
  	case 4096:
  		return 0;
  	}
  
  	return -EINVAL;
  }

  static int rsa_set_pub_key(struct crypto_akcipher *tfm, const void *key,
  			   unsigned int keylen)

  {

  	struct rsa_mpi_key *mpi_key = akcipher_tfm_ctx(tfm);
  	struct rsa_key raw_key = {0};

  	int ret;

  	/* Free the old MPI key if any */
  	rsa_free_mpi_key(mpi_key);
  
  	ret = rsa_parse_pub_key(&raw_key, key, keylen);

  	if (ret)
  		return ret;

  	mpi_key->e = mpi_read_raw_data(raw_key.e, raw_key.e_sz);
  	if (!mpi_key->e)
  		goto err;
  
  	mpi_key->n = mpi_read_raw_data(raw_key.n, raw_key.n_sz);
  	if (!mpi_key->n)
  		goto err;
  
  	if (rsa_check_key_length(mpi_get_size(mpi_key->n) << 3)) {
  		rsa_free_mpi_key(mpi_key);
  		return -EINVAL;

  	}

  
  	return 0;
  
  err:
  	rsa_free_mpi_key(mpi_key);
  	return -ENOMEM;

  }

  static int rsa_set_priv_key(struct crypto_akcipher *tfm, const void *key,
  			    unsigned int keylen)
  {

  	struct rsa_mpi_key *mpi_key = akcipher_tfm_ctx(tfm);
  	struct rsa_key raw_key = {0};

  	int ret;

  	/* Free the old MPI key if any */
  	rsa_free_mpi_key(mpi_key);
  
  	ret = rsa_parse_priv_key(&raw_key, key, keylen);

  	if (ret)
  		return ret;

  	mpi_key->d = mpi_read_raw_data(raw_key.d, raw_key.d_sz);
  	if (!mpi_key->d)
  		goto err;
  
  	mpi_key->e = mpi_read_raw_data(raw_key.e, raw_key.e_sz);
  	if (!mpi_key->e)
  		goto err;
  
  	mpi_key->n = mpi_read_raw_data(raw_key.n, raw_key.n_sz);
  	if (!mpi_key->n)
  		goto err;
  
  	if (rsa_check_key_length(mpi_get_size(mpi_key->n) << 3)) {
  		rsa_free_mpi_key(mpi_key);
  		return -EINVAL;

  	}

  
  	return 0;
  
  err:
  	rsa_free_mpi_key(mpi_key);
  	return -ENOMEM;

  }

  static unsigned int rsa_max_size(struct crypto_akcipher *tfm)

  {

  	struct rsa_mpi_key *pkey = akcipher_tfm_ctx(tfm);

  	return mpi_get_size(pkey->n);

  }

  static void rsa_exit_tfm(struct crypto_akcipher *tfm)
  {

  	struct rsa_mpi_key *pkey = akcipher_tfm_ctx(tfm);

  	rsa_free_mpi_key(pkey);

  }
  
  static struct akcipher_alg rsa = {
  	.encrypt = rsa_enc,
  	.decrypt = rsa_dec,

  	.set_priv_key = rsa_set_priv_key,
  	.set_pub_key = rsa_set_pub_key,
  	.max_size = rsa_max_size,

  	.exit = rsa_exit_tfm,
  	.base = {
  		.cra_name = "rsa",
  		.cra_driver_name = "rsa-generic",
  		.cra_priority = 100,
  		.cra_module = THIS_MODULE,

  		.cra_ctxsize = sizeof(struct rsa_mpi_key),

  	},
  };
  
  static int rsa_init(void)
  {

  	int err;
  
  	err = crypto_register_akcipher(&rsa);
  	if (err)
  		return err;
  
  	err = crypto_register_template(&rsa_pkcs1pad_tmpl);
  	if (err) {
  		crypto_unregister_akcipher(&rsa);
  		return err;
  	}
  
  	return 0;

  }
  
  static void rsa_exit(void)
  {

  	crypto_unregister_template(&rsa_pkcs1pad_tmpl);

  	crypto_unregister_akcipher(&rsa);
  }

  subsys_initcall(rsa_init);

  module_exit(rsa_exit);
  MODULE_ALIAS_CRYPTO("rsa");
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("RSA generic algorithm");