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linux/crypto/rsa.c
Joachim Vandersmissen e8829ef1f7 crypto: rsa - restrict plaintext/ciphertext values more 
SP 800-56Br2, Section 7.1.1 [1] specifies that:
1. If m does not satisfy 1 < m < (n – 1), output an indication that m is
out of range, and exit without further processing.

Similarly, Section 7.1.2 of the same standard specifies that:
1. If the ciphertext c does not satisfy 1 < c < (n – 1), output an
indication that the ciphertext is out of range, and exit without further
processing.

This range is slightly more conservative than RFC3447, as it also
excludes RSA fixed points 0, 1, and n - 1.

[1] https://doi.org/10.6028/NIST.SP.800-56Br2

Signed-off-by: Joachim Vandersmissen <git@jvdsn.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2024-02-09 12:57:18 +08:00

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// 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 */
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 */
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);
ret = 0;
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;
/* 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;
mpi_set_bit(e_max, 256);
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) {
crypto_unregister_akcipher(&rsa);
return err;
}
return 0;
}
static void __exit 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");
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