// 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/fips.h>
#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;
        MPI p;
        MPI q;
        MPI dp;
        MPI dq;
        MPI qinv;
};

static int rsa_check_payload(MPI x, MPI n)
{
        MPI n1;

        if (mpi_cmp_ui(x, 1) <= 0)
                return -EINVAL;

        n1 = mpi_alloc(0);
        if (!n1)
                return -ENOMEM;

        if (mpi_sub_ui(n1, n, 1) || mpi_cmp(x, n1) >= 0) {
                mpi_free(n1);
                return -EINVAL;
        }

        mpi_free(n1);
        return 0;
}

/*
 * 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)
{
        /*
         * Even though (1) in RFC3447 only requires 0 <= m <= n - 1, we are
         * slightly more conservative and require 1 < m < n - 1. This is in line
         * with SP 800-56Br2, Section 7.1.1.
         */
        if (rsa_check_payload(m, key->n))
                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_1 = c^dP mod p;
 * m_2 = c^dQ mod q;
 * h = (m_1 - m_2) * qInv mod p;
 * m = m_2 + q * h;
 */
static int _rsa_dec_crt(const struct rsa_mpi_key *key, MPI m_or_m1_or_h, MPI c)
{
        MPI m2, m12_or_qh;
        int ret = -ENOMEM;

        /*
         * Even though (1) in RFC3447 only requires 0 <= c <= n - 1, we are
         * slightly more conservative and require 1 < c < n - 1. This is in line
         * with SP 800-56Br2, Section 7.1.2.
         */
        if (rsa_check_payload(c, key->n))
                return -EINVAL;

        m2 = mpi_alloc(0);
        m12_or_qh = mpi_alloc(0);
        if (!m2 || !m12_or_qh)
                goto err_free_mpi;

        /* (2i) m_1 = c^dP mod p */
        ret = mpi_powm(m_or_m1_or_h, c, key->dp, key->p);
        if (ret)
                goto err_free_mpi;

        /* (2i) m_2 = c^dQ mod q */
        ret = mpi_powm(m2, c, key->dq, key->q);
        if (ret)
                goto err_free_mpi;

        /* (2iii) h = (m_1 - m_2) * qInv mod p */
        ret = mpi_sub(m12_or_qh, m_or_m1_or_h, m2) ?:
              mpi_mulm(m_or_m1_or_h, m12_or_qh, key->qinv, key->p);

        /* (2iv) m = m_2 + q * h */
        ret = ret ?:
              mpi_mul(m12_or_qh, key->q, m_or_m1_or_h) ?:
              mpi_addm(m_or_m1_or_h, m2, m12_or_qh, key->n);

err_free_mpi:
        mpi_free(m12_or_qh);
        mpi_free(m2);
        return ret;
}

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_crt(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);
        mpi_free(key->p);
        mpi_free(key->q);
        mpi_free(key->dp);
        mpi_free(key->dq);
        mpi_free(key->qinv);
        key->d = NULL;
        key->e = NULL;
        key->n = NULL;
        key->p = NULL;
        key->q = NULL;
        key->dp = NULL;
        key->dq = NULL;
        key->qinv = NULL;
}

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

        return -EINVAL;
}

static int rsa_check_exponent_fips(MPI e)
{
        MPI e_max = NULL;
        int err;

        /* check if odd */
        if (!mpi_test_bit(e, 0)) {
                return -EINVAL;
        }

        /* check if 2^16 < e < 2^256. */
        if (mpi_cmp_ui(e, 65536) <= 0) {
                return -EINVAL;
        }

        e_max = mpi_alloc(0);
        if (!e_max)
                return -ENOMEM;

        err = mpi_set_bit(e_max, 256);
        if (err) {
                mpi_free(e_max);
                return err;
        }

        if (mpi_cmp(e, e_max) >= 0) {
                mpi_free(e_max);
                return -EINVAL;
        }

        mpi_free(e_max);
        return 0;
}

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;
        }

        if (fips_enabled && rsa_check_exponent_fips(mpi_key->e)) {
                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;

        mpi_key->p = mpi_read_raw_data(raw_key.p, raw_key.p_sz);
        if (!mpi_key->p)
                goto err;

        mpi_key->q = mpi_read_raw_data(raw_key.q, raw_key.q_sz);
        if (!mpi_key->q)
                goto err;

        mpi_key->dp = mpi_read_raw_data(raw_key.dp, raw_key.dp_sz);
        if (!mpi_key->dp)
                goto err;

        mpi_key->dq = mpi_read_raw_data(raw_key.dq, raw_key.dq_sz);
        if (!mpi_key->dq)
                goto err;

        mpi_key->qinv = mpi_read_raw_data(raw_key.qinv, raw_key.qinv_sz);
        if (!mpi_key->qinv)
                goto err;

        if (rsa_check_key_length(mpi_get_size(mpi_key->n) << 3)) {
                rsa_free_mpi_key(mpi_key);
                return -EINVAL;
        }

        if (fips_enabled && rsa_check_exponent_fips(mpi_key->e)) {
                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 __init rsa_init(void)
{
        int err;

        err = crypto_register_akcipher(&rsa);
        if (err)
                return err;

        err = crypto_register_template(&rsa_pkcs1pad_tmpl);
        if (err)
                goto err_unregister_rsa;

        err = crypto_register_template(&rsassa_pkcs1_tmpl);
        if (err)
                goto err_unregister_rsa_pkcs1pad;

        return 0;

err_unregister_rsa_pkcs1pad:
        crypto_unregister_template(&rsa_pkcs1pad_tmpl);
err_unregister_rsa:
        crypto_unregister_akcipher(&rsa);
        return err;
}

static void __exit rsa_exit(void)
{
        crypto_unregister_template(&rsassa_pkcs1_tmpl);
        crypto_unregister_template(&rsa_pkcs1pad_tmpl);
        crypto_unregister_akcipher(&rsa);
}

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