[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/fips.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;

	if (fips_enabled) {
		/* SP800-56A rev3 5.7.1.1 check: Validation of shared secret */
		if (req->src) {
			MPI pone;

			/* z <= 1 */
			if (mpi_cmp_ui(val, 1) < 1) {
				ret = -EBADMSG;
				goto err_free_base;
			}

			/* z == p - 1 */
			pone = mpi_alloc(0);

			if (!pone) {
				ret = -ENOMEM;
				goto err_free_base;
			}

			ret = mpi_sub_ui(pone, ctx->p, 1);
			if (!ret && !mpi_cmp(pone, val))
				ret = -EBADMSG;

			mpi_free(pone);

			if (ret)
				goto err_free_base;

		/* SP800-56A rev 3 5.6.2.1.3 key check */
		} else {
			if (dh_is_pubkey_valid(ctx, val)) {
				ret = -EAGAIN;
				goto err_free_val;
			}
		}
	}

	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>
90fa9ae5	12	#include <linux/fips.h>
802c7f1c SB	13	#include <linux/mpi.h>
	14
	15	struct dh_ctx {
e3fe0ae1 SM	16	MPI p; /* Value is guaranteed to be set. */
	17	MPI q; /* Value is optional. */
	18	MPI g; /* Value is guaranteed to be set. */
	19	MPI xa; /* Value is guaranteed to be set. */
802c7f1c SB	20	};
802c7f1c SB	21
12d41a02	22	static void dh_clear_ctx(struct dh_ctx *ctx)
802c7f1c SB	23	{
802c7f1c SB	24	mpi_free(ctx->p);
e3fe0ae1	25	mpi_free(ctx->q);
802c7f1c	26	mpi_free(ctx->g);
802c7f1c	27	mpi_free(ctx->xa);
12d41a02	28	memset(ctx, 0, sizeof(*ctx));
802c7f1c SB	29	}
	30
	31	/*
	32	* If base is g we compute the public key
	33	* ya = g^xa mod p; [RFC2631 sec 2.1.1]
	34	* else if base if the counterpart public key we compute the shared secret
	35	* ZZ = yb^xa mod p; [RFC2631 sec 2.1.1]
	36	*/
	37	static int _compute_val(const struct dh_ctx *ctx, MPI base, MPI val)
	38	{
	39	/* val = base^xa mod p */
	40	return mpi_powm(val, base, ctx->xa, ctx->p);
	41	}
	42
	43	static inline struct dh_ctx dh_get_ctx(struct crypto_kpp tfm)
	44	{
	45	return kpp_tfm_ctx(tfm);
	46	}
	47
	48	static int dh_check_params_length(unsigned int p_len)
	49	{
	50	return (p_len < 1536) ? -EINVAL : 0;
	51	}
	52
	53	static int dh_set_params(struct dh_ctx ctx, struct dh params)
	54	{
802c7f1c SB	55	if (dh_check_params_length(params->p_size << 3))
	56	return -EINVAL;
	57
	58	ctx->p = mpi_read_raw_data(params->p, params->p_size);
	59	if (!ctx->p)
	60	return -EINVAL;
	61
e3fe0ae1 SM	62	if (params->q && params->q_size) {
	63	ctx->q = mpi_read_raw_data(params->q, params->q_size);
	64	if (!ctx->q)
	65	return -EINVAL;
	66	}
	67
802c7f1c	68	ctx->g = mpi_read_raw_data(params->g, params->g_size);
12d41a02	69	if (!ctx->g)
802c7f1c	70	return -EINVAL;
802c7f1c SB	71
	72	return 0;
	73	}
	74
5527dfb6 EB	75	static int dh_set_secret(struct crypto_kpp tfm, const void buf,
5527dfb6 EB	76	unsigned int len)
802c7f1c SB	77	{
	78	struct dh_ctx *ctx = dh_get_ctx(tfm);
	79	struct dh params;
	80
ee34e264	81	/* Free the old MPI key if any */
12d41a02	82	dh_clear_ctx(ctx);
ee34e264	83
802c7f1c	84	if (crypto_dh_decode_key(buf, len, &params) < 0)
12d41a02	85	goto err_clear_ctx;
802c7f1c SB	86
802c7f1c SB	87	if (dh_set_params(ctx, &params) < 0)
12d41a02	88	goto err_clear_ctx;
802c7f1c SB	89
802c7f1c SB	90	ctx->xa = mpi_read_raw_data(params.key, params.key_size);
12d41a02 EB	91	if (!ctx->xa)
12d41a02 EB	92	goto err_clear_ctx;
802c7f1c SB	93
802c7f1c SB	94	return 0;
12d41a02 EB	95
	96	err_clear_ctx:
	97	dh_clear_ctx(ctx);
	98	return -EINVAL;
802c7f1c SB	99	}
802c7f1c SB	100
e3fe0ae1 SM	101	/*
	102	* SP800-56A public key verification:
	103	*
	104	* * If Q is provided as part of the domain paramenters, a full validation
	105	* according to SP800-56A section 5.6.2.3.1 is performed.
	106	*
	107	* * If Q is not provided, a partial validation according to SP800-56A section
	108	* 5.6.2.3.2 is performed.
	109	*/
	110	static int dh_is_pubkey_valid(struct dh_ctx *ctx, MPI y)
	111	{
	112	if (unlikely(!ctx->p))
	113	return -EINVAL;
	114
	115	/*
	116	* Step 1: Verify that 2 <= y <= p - 2.
	117	*
	118	* The upper limit check is actually y < p instead of y < p - 1
	119	* as the mpi_sub_ui function is yet missing.
	120	*/
	121	if (mpi_cmp_ui(y, 1) < 1 \|\| mpi_cmp(y, ctx->p) >= 0)
	122	return -EINVAL;
	123
	124	/* Step 2: Verify that 1 = y^q mod p */
	125	if (ctx->q) {
	126	MPI val = mpi_alloc(0);
	127	int ret;
	128
	129	if (!val)
	130	return -ENOMEM;
	131
	132	ret = mpi_powm(val, y, ctx->q, ctx->p);
	133
	134	if (ret) {
	135	mpi_free(val);
	136	return ret;
	137	}
	138
	139	ret = mpi_cmp_ui(val, 1);
	140
	141	mpi_free(val);
	142
	143	if (ret != 0)
	144	return -EINVAL;
	145	}
	146
	147	return 0;
	148	}
	149
802c7f1c SB	150	static int dh_compute_value(struct kpp_request *req)
	151	{
	152	struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
	153	struct dh_ctx *ctx = dh_get_ctx(tfm);
	154	MPI base, val = mpi_alloc(0);
	155	int ret = 0;
	156	int sign;
	157
	158	if (!val)
	159	return -ENOMEM;
	160
	161	if (unlikely(!ctx->xa)) {
	162	ret = -EINVAL;
	163	goto err_free_val;
	164	}
	165
	166	if (req->src) {
	167	base = mpi_read_raw_from_sgl(req->src, req->src_len);
	168	if (!base) {
8edda7d2	169	ret = -EINVAL;
802c7f1c SB	170	goto err_free_val;
802c7f1c SB	171	}
e3fe0ae1 SM	172	ret = dh_is_pubkey_valid(ctx, base);
e3fe0ae1 SM	173	if (ret)
3fd8093b	174	goto err_free_base;
802c7f1c SB	175	} else {
	176	base = ctx->g;
	177	}
	178
	179	ret = _compute_val(ctx, base, val);
	180	if (ret)
	181	goto err_free_base;
	182
2ed5ba61 SM	183	if (fips_enabled) {
	184	/* SP800-56A rev3 5.7.1.1 check: Validation of shared secret */
	185	if (req->src) {
	186	MPI pone;
	187
	188	/* z <= 1 */
	189	if (mpi_cmp_ui(val, 1) < 1) {
	190	ret = -EBADMSG;
	191	goto err_free_base;
	192	}
	193
	194	/* z == p - 1 */
	195	pone = mpi_alloc(0);
	196
	197	if (!pone) {
	198	ret = -ENOMEM;
	199	goto err_free_base;
	200	}
	201
	202	ret = mpi_sub_ui(pone, ctx->p, 1);
	203	if (!ret && !mpi_cmp(pone, val))
	204	ret = -EBADMSG;
	205
	206	mpi_free(pone);
	207
	208	if (ret)
	209	goto err_free_base;
	210
	211	/* SP800-56A rev 3 5.6.2.1.3 key check */
	212	} else {
	213	if (dh_is_pubkey_valid(ctx, val)) {
	214	ret = -EAGAIN;
	215	goto err_free_val;
	216	}
90fa9ae5	217	}
90fa9ae5 SM	218	}
90fa9ae5 SM	219
9b45b7bb	220	ret = mpi_write_to_sgl(val, req->dst, req->dst_len, &sign);
802c7f1c SB	221	if (ret)
	222	goto err_free_base;
	223
	224	if (sign < 0)
	225	ret = -EBADMSG;
	226	err_free_base:
	227	if (req->src)
	228	mpi_free(base);
	229	err_free_val:
	230	mpi_free(val);
	231	return ret;
	232	}
	233
7f691050	234	static unsigned int dh_max_size(struct crypto_kpp *tfm)
802c7f1c SB	235	{
	236	struct dh_ctx *ctx = dh_get_ctx(tfm);
	237
	238	return mpi_get_size(ctx->p);
	239	}
	240
	241	static void dh_exit_tfm(struct crypto_kpp *tfm)
	242	{
	243	struct dh_ctx *ctx = dh_get_ctx(tfm);
	244
12d41a02	245	dh_clear_ctx(ctx);
802c7f1c SB	246	}
	247
	248	static struct kpp_alg dh = {
	249	.set_secret = dh_set_secret,
	250	.generate_public_key = dh_compute_value,
	251	.compute_shared_secret = dh_compute_value,
	252	.max_size = dh_max_size,
	253	.exit = dh_exit_tfm,
	254	.base = {
	255	.cra_name = "dh",
	256	.cra_driver_name = "dh-generic",
	257	.cra_priority = 100,
	258	.cra_module = THIS_MODULE,
	259	.cra_ctxsize = sizeof(struct dh_ctx),
	260	},
	261	};
	262
	263	static int dh_init(void)
	264	{
	265	return crypto_register_kpp(&dh);
	266	}
	267
	268	static void dh_exit(void)
	269	{
	270	crypto_unregister_kpp(&dh);
	271	}
	272
c4741b23	273	subsys_initcall(dh_init);
802c7f1c SB	274	module_exit(dh_exit);
	275	MODULE_ALIAS_CRYPTO("dh");
	276	MODULE_LICENSE("GPL");
	277	MODULE_DESCRIPTION("DH generic algorithm");