[linux.git] / crypto / dh.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*  Diffie-Hellman Key Agreement Method [RFC2631]
 *
 * Copyright (c) 2016, Intel Corporation
 * Authors: Salvatore Benedetto <[email protected]>
 */

#include <linux/module.h>
#include <crypto/internal/kpp.h>
#include <crypto/kpp.h>
#include <crypto/dh.h>
#include <linux/mpi.h>

struct dh_ctx {
	MPI p;	/* Value is guaranteed to be set. */
	MPI q;	/* Value is optional. */
	MPI g;	/* Value is guaranteed to be set. */
	MPI xa;	/* Value is guaranteed to be set. */
};

static void dh_clear_ctx(struct dh_ctx *ctx)
{
	mpi_free(ctx->p);
	mpi_free(ctx->q);
	mpi_free(ctx->g);
	mpi_free(ctx->xa);
	memset(ctx, 0, sizeof(*ctx));
}

/*
 * If base is g we compute the public key
 *	ya = g^xa mod p; [RFC2631 sec 2.1.1]
 * else if base if the counterpart public key we compute the shared secret
 *	ZZ = yb^xa mod p; [RFC2631 sec 2.1.1]
 */
static int _compute_val(const struct dh_ctx *ctx, MPI base, MPI val)
{
	/* val = base^xa mod p */
	return mpi_powm(val, base, ctx->xa, ctx->p);
}

static inline struct dh_ctx *dh_get_ctx(struct crypto_kpp *tfm)
{
	return kpp_tfm_ctx(tfm);
}

static int dh_check_params_length(unsigned int p_len)
{
	return (p_len < 1536) ? -EINVAL : 0;
}

static int dh_set_params(struct dh_ctx *ctx, struct dh *params)
{
	if (dh_check_params_length(params->p_size << 3))
		return -EINVAL;

	ctx->p = mpi_read_raw_data(params->p, params->p_size);
	if (!ctx->p)
		return -EINVAL;

	if (params->q && params->q_size) {
		ctx->q = mpi_read_raw_data(params->q, params->q_size);
		if (!ctx->q)
			return -EINVAL;
	}

	ctx->g = mpi_read_raw_data(params->g, params->g_size);
	if (!ctx->g)
		return -EINVAL;

	return 0;
}

static int dh_set_secret(struct crypto_kpp *tfm, const void *buf,
			 unsigned int len)
{
	struct dh_ctx *ctx = dh_get_ctx(tfm);
	struct dh params;

	/* Free the old MPI key if any */
	dh_clear_ctx(ctx);

	if (crypto_dh_decode_key(buf, len, &params) < 0)
		goto err_clear_ctx;

	if (dh_set_params(ctx, &params) < 0)
		goto err_clear_ctx;

	ctx->xa = mpi_read_raw_data(params.key, params.key_size);
	if (!ctx->xa)
		goto err_clear_ctx;

	return 0;

err_clear_ctx:
	dh_clear_ctx(ctx);
	return -EINVAL;
}

/*
 * SP800-56A public key verification:
 *
 * * If Q is provided as part of the domain paramenters, a full validation
 *   according to SP800-56A section 5.6.2.3.1 is performed.
 *
 * * If Q is not provided, a partial validation according to SP800-56A section
 *   5.6.2.3.2 is performed.
 */
static int dh_is_pubkey_valid(struct dh_ctx *ctx, MPI y)
{
	if (unlikely(!ctx->p))
		return -EINVAL;

	/*
	 * Step 1: Verify that 2 <= y <= p - 2.
	 *
	 * The upper limit check is actually y < p instead of y < p - 1
	 * as the mpi_sub_ui function is yet missing.
	 */
	if (mpi_cmp_ui(y, 1) < 1 || mpi_cmp(y, ctx->p) >= 0)
		return -EINVAL;

	/* Step 2: Verify that 1 = y^q mod p */
	if (ctx->q) {
		MPI val = mpi_alloc(0);
		int ret;

		if (!val)
			return -ENOMEM;

		ret = mpi_powm(val, y, ctx->q, ctx->p);

		if (ret) {
			mpi_free(val);
			return ret;
		}

		ret = mpi_cmp_ui(val, 1);

		mpi_free(val);

		if (ret != 0)
			return -EINVAL;
	}

	return 0;
}

static int dh_compute_value(struct kpp_request *req)
{
	struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
	struct dh_ctx *ctx = dh_get_ctx(tfm);
	MPI base, val = mpi_alloc(0);
	int ret = 0;
	int sign;

	if (!val)
		return -ENOMEM;

	if (unlikely(!ctx->xa)) {
		ret = -EINVAL;
		goto err_free_val;
	}

	if (req->src) {
		base = mpi_read_raw_from_sgl(req->src, req->src_len);
		if (!base) {
			ret = -EINVAL;
			goto err_free_val;
		}
		ret = dh_is_pubkey_valid(ctx, base);
		if (ret)
			goto err_free_base;
	} else {
		base = ctx->g;
	}

	ret = _compute_val(ctx, base, val);
	if (ret)
		goto err_free_base;

	ret = mpi_write_to_sgl(val, req->dst, req->dst_len, &sign);
	if (ret)
		goto err_free_base;

	if (sign < 0)
		ret = -EBADMSG;
err_free_base:
	if (req->src)
		mpi_free(base);
err_free_val:
	mpi_free(val);
	return ret;
}

static unsigned int dh_max_size(struct crypto_kpp *tfm)
{
	struct dh_ctx *ctx = dh_get_ctx(tfm);

	return mpi_get_size(ctx->p);
}

static void dh_exit_tfm(struct crypto_kpp *tfm)
{
	struct dh_ctx *ctx = dh_get_ctx(tfm);

	dh_clear_ctx(ctx);
}

static struct kpp_alg dh = {
	.set_secret = dh_set_secret,
	.generate_public_key = dh_compute_value,
	.compute_shared_secret = dh_compute_value,
	.max_size = dh_max_size,
	.exit = dh_exit_tfm,
	.base = {
		.cra_name = "dh",
		.cra_driver_name = "dh-generic",
		.cra_priority = 100,
		.cra_module = THIS_MODULE,
		.cra_ctxsize = sizeof(struct dh_ctx),
	},
};

static int dh_init(void)
{
	return crypto_register_kpp(&dh);
}

static void dh_exit(void)
{
	crypto_unregister_kpp(&dh);
}

subsys_initcall(dh_init);
module_exit(dh_exit);
MODULE_ALIAS_CRYPTO("dh");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("DH generic algorithm");
Commit	Line	Data
2874c5fd	1	// SPDX-License-Identifier: GPL-2.0-or-later
802c7f1c SB	2	/* Diffie-Hellman Key Agreement Method [RFC2631]
	3	*
	4	* Copyright (c) 2016, Intel Corporation
	5	* Authors: Salvatore Benedetto <[email protected]>
802c7f1c SB	6	*/
	7
	8	#include <linux/module.h>
	9	#include <crypto/internal/kpp.h>
	10	#include <crypto/kpp.h>
	11	#include <crypto/dh.h>
	12	#include <linux/mpi.h>
	13
	14	struct dh_ctx {
e3fe0ae1 SM	15	MPI p; /* Value is guaranteed to be set. */
	16	MPI q; /* Value is optional. */
	17	MPI g; /* Value is guaranteed to be set. */
	18	MPI xa; /* Value is guaranteed to be set. */
802c7f1c SB	19	};
802c7f1c SB	20
12d41a02	21	static void dh_clear_ctx(struct dh_ctx *ctx)
802c7f1c SB	22	{
802c7f1c SB	23	mpi_free(ctx->p);
e3fe0ae1	24	mpi_free(ctx->q);
802c7f1c	25	mpi_free(ctx->g);
802c7f1c	26	mpi_free(ctx->xa);
12d41a02	27	memset(ctx, 0, sizeof(*ctx));
802c7f1c SB	28	}
	29
	30	/*
	31	* If base is g we compute the public key
	32	* ya = g^xa mod p; [RFC2631 sec 2.1.1]
	33	* else if base if the counterpart public key we compute the shared secret
	34	* ZZ = yb^xa mod p; [RFC2631 sec 2.1.1]
	35	*/
	36	static int _compute_val(const struct dh_ctx *ctx, MPI base, MPI val)
	37	{
	38	/* val = base^xa mod p */
	39	return mpi_powm(val, base, ctx->xa, ctx->p);
	40	}
	41
	42	static inline struct dh_ctx dh_get_ctx(struct crypto_kpp tfm)
	43	{
	44	return kpp_tfm_ctx(tfm);
	45	}
	46
	47	static int dh_check_params_length(unsigned int p_len)
	48	{
	49	return (p_len < 1536) ? -EINVAL : 0;
	50	}
	51
	52	static int dh_set_params(struct dh_ctx ctx, struct dh params)
	53	{
802c7f1c SB	54	if (dh_check_params_length(params->p_size << 3))
	55	return -EINVAL;
	56
	57	ctx->p = mpi_read_raw_data(params->p, params->p_size);
	58	if (!ctx->p)
	59	return -EINVAL;
	60
e3fe0ae1 SM	61	if (params->q && params->q_size) {
	62	ctx->q = mpi_read_raw_data(params->q, params->q_size);
	63	if (!ctx->q)
	64	return -EINVAL;
	65	}
	66
802c7f1c	67	ctx->g = mpi_read_raw_data(params->g, params->g_size);
12d41a02	68	if (!ctx->g)
802c7f1c	69	return -EINVAL;
802c7f1c SB	70
	71	return 0;
	72	}
	73
5527dfb6 EB	74	static int dh_set_secret(struct crypto_kpp tfm, const void buf,
5527dfb6 EB	75	unsigned int len)
802c7f1c SB	76	{
	77	struct dh_ctx *ctx = dh_get_ctx(tfm);
	78	struct dh params;
	79
ee34e264	80	/* Free the old MPI key if any */
12d41a02	81	dh_clear_ctx(ctx);
ee34e264	82
802c7f1c	83	if (crypto_dh_decode_key(buf, len, &params) < 0)
12d41a02	84	goto err_clear_ctx;
802c7f1c SB	85
802c7f1c SB	86	if (dh_set_params(ctx, &params) < 0)
12d41a02	87	goto err_clear_ctx;
802c7f1c SB	88
802c7f1c SB	89	ctx->xa = mpi_read_raw_data(params.key, params.key_size);
12d41a02 EB	90	if (!ctx->xa)
12d41a02 EB	91	goto err_clear_ctx;
802c7f1c SB	92
802c7f1c SB	93	return 0;
12d41a02 EB	94
	95	err_clear_ctx:
	96	dh_clear_ctx(ctx);
	97	return -EINVAL;
802c7f1c SB	98	}
802c7f1c SB	99
e3fe0ae1 SM	100	/*
	101	* SP800-56A public key verification:
	102	*
	103	* * If Q is provided as part of the domain paramenters, a full validation
	104	* according to SP800-56A section 5.6.2.3.1 is performed.
	105	*
	106	* * If Q is not provided, a partial validation according to SP800-56A section
	107	* 5.6.2.3.2 is performed.
	108	*/
	109	static int dh_is_pubkey_valid(struct dh_ctx *ctx, MPI y)
	110	{
	111	if (unlikely(!ctx->p))
	112	return -EINVAL;
	113
	114	/*
	115	* Step 1: Verify that 2 <= y <= p - 2.
	116	*
	117	* The upper limit check is actually y < p instead of y < p - 1
	118	* as the mpi_sub_ui function is yet missing.
	119	*/
	120	if (mpi_cmp_ui(y, 1) < 1 \|\| mpi_cmp(y, ctx->p) >= 0)
	121	return -EINVAL;
	122
	123	/* Step 2: Verify that 1 = y^q mod p */
	124	if (ctx->q) {
	125	MPI val = mpi_alloc(0);
	126	int ret;
	127
	128	if (!val)
	129	return -ENOMEM;
	130
	131	ret = mpi_powm(val, y, ctx->q, ctx->p);
	132
	133	if (ret) {
	134	mpi_free(val);
	135	return ret;
	136	}
	137
	138	ret = mpi_cmp_ui(val, 1);
	139
	140	mpi_free(val);
	141
	142	if (ret != 0)
	143	return -EINVAL;
	144	}
	145
	146	return 0;
	147	}
	148
802c7f1c SB	149	static int dh_compute_value(struct kpp_request *req)
	150	{
	151	struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
	152	struct dh_ctx *ctx = dh_get_ctx(tfm);
	153	MPI base, val = mpi_alloc(0);
	154	int ret = 0;
	155	int sign;
	156
	157	if (!val)
	158	return -ENOMEM;
	159
	160	if (unlikely(!ctx->xa)) {
	161	ret = -EINVAL;
	162	goto err_free_val;
	163	}
	164
	165	if (req->src) {
	166	base = mpi_read_raw_from_sgl(req->src, req->src_len);
	167	if (!base) {
8edda7d2	168	ret = -EINVAL;
802c7f1c SB	169	goto err_free_val;
802c7f1c SB	170	}
e3fe0ae1 SM	171	ret = dh_is_pubkey_valid(ctx, base);
e3fe0ae1 SM	172	if (ret)
3fd8093b	173	goto err_free_base;
802c7f1c SB	174	} else {
	175	base = ctx->g;
	176	}
	177
	178	ret = _compute_val(ctx, base, val);
	179	if (ret)
	180	goto err_free_base;
	181
9b45b7bb	182	ret = mpi_write_to_sgl(val, req->dst, req->dst_len, &sign);
802c7f1c SB	183	if (ret)
	184	goto err_free_base;
	185
	186	if (sign < 0)
	187	ret = -EBADMSG;
	188	err_free_base:
	189	if (req->src)
	190	mpi_free(base);
	191	err_free_val:
	192	mpi_free(val);
	193	return ret;
	194	}
	195
7f691050	196	static unsigned int dh_max_size(struct crypto_kpp *tfm)
802c7f1c SB	197	{
	198	struct dh_ctx *ctx = dh_get_ctx(tfm);
	199
	200	return mpi_get_size(ctx->p);
	201	}
	202
	203	static void dh_exit_tfm(struct crypto_kpp *tfm)
	204	{
	205	struct dh_ctx *ctx = dh_get_ctx(tfm);
	206
12d41a02	207	dh_clear_ctx(ctx);
802c7f1c SB	208	}
	209
	210	static struct kpp_alg dh = {
	211	.set_secret = dh_set_secret,
	212	.generate_public_key = dh_compute_value,
	213	.compute_shared_secret = dh_compute_value,
	214	.max_size = dh_max_size,
	215	.exit = dh_exit_tfm,
	216	.base = {
	217	.cra_name = "dh",
	218	.cra_driver_name = "dh-generic",
	219	.cra_priority = 100,
	220	.cra_module = THIS_MODULE,
	221	.cra_ctxsize = sizeof(struct dh_ctx),
	222	},
	223	};
	224
	225	static int dh_init(void)
	226	{
	227	return crypto_register_kpp(&dh);
	228	}
	229
	230	static void dh_exit(void)
	231	{
	232	crypto_unregister_kpp(&dh);
	233	}
	234
c4741b23	235	subsys_initcall(dh_init);
802c7f1c SB	236	module_exit(dh_exit);
	237	MODULE_ALIAS_CRYPTO("dh");
	238	MODULE_LICENSE("GPL");
	239	MODULE_DESCRIPTION("DH generic algorithm");