/src/openssl33/providers/implementations/exchange/ecdh_exch.c

Source
/*
 * Copyright 2020-2023 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

/*
 * ECDH low level APIs are deprecated for public use, but still ok for
 * internal use.
 */
#include "internal/deprecated.h"

#include <string.h>
#include <openssl/crypto.h>
#include <openssl/evp.h>
#include <openssl/core_dispatch.h>
#include <openssl/core_names.h>
#include <openssl/ec.h>
#include <openssl/params.h>
#include <openssl/err.h>
#include <openssl/proverr.h>
#include "prov/provider_ctx.h"
#include "prov/providercommon.h"
#include "prov/implementations.h"
#include "prov/securitycheck.h"
#include "crypto/ec.h" /* ossl_ecdh_kdf_X9_63() */

static OSSL_FUNC_keyexch_newctx_fn ecdh_newctx;
static OSSL_FUNC_keyexch_init_fn ecdh_init;
static OSSL_FUNC_keyexch_set_peer_fn ecdh_set_peer;
static OSSL_FUNC_keyexch_derive_fn ecdh_derive;
static OSSL_FUNC_keyexch_freectx_fn ecdh_freectx;
static OSSL_FUNC_keyexch_dupctx_fn ecdh_dupctx;
static OSSL_FUNC_keyexch_set_ctx_params_fn ecdh_set_ctx_params;
static OSSL_FUNC_keyexch_settable_ctx_params_fn ecdh_settable_ctx_params;
static OSSL_FUNC_keyexch_get_ctx_params_fn ecdh_get_ctx_params;
static OSSL_FUNC_keyexch_gettable_ctx_params_fn ecdh_gettable_ctx_params;

enum kdf_type {
    PROV_ECDH_KDF_NONE = 0,
    PROV_ECDH_KDF_X9_63
};

/*
 * What's passed as an actual key is defined by the KEYMGMT interface.
 * We happen to know that our KEYMGMT simply passes EC_KEY structures, so
 * we use that here too.
 */

typedef struct {
    OSSL_LIB_CTX *libctx;

    EC_KEY *k;
    EC_KEY *peerk;

    /*
     * ECDH cofactor mode:
     *
     *  . 0  disabled
     *  . 1  enabled
     *  . -1 use cofactor mode set for k
     */
    int cofactor_mode;

    /************
     * ECDH KDF *
     ************/
    /* KDF (if any) to use for ECDH */
    enum kdf_type kdf_type;
    /* Message digest to use for key derivation */
    EVP_MD *kdf_md;
    /* User key material */
    unsigned char *kdf_ukm;
    size_t kdf_ukmlen;
    /* KDF output length */
    size_t kdf_outlen;
} PROV_ECDH_CTX;

static void *ecdh_newctx(void *provctx)
{
    PROV_ECDH_CTX *pectx;

    if (!ossl_prov_is_running())
        return NULL;

    pectx = OPENSSL_zalloc(sizeof(*pectx));
    if (pectx == NULL)
        return NULL;

    pectx->libctx = PROV_LIBCTX_OF(provctx);
    pectx->cofactor_mode = -1;
    pectx->kdf_type = PROV_ECDH_KDF_NONE;

    return (void *)pectx;
}

static int ecdh_init(void *vpecdhctx, void *vecdh, const OSSL_PARAM params[])
{
    PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;

    if (!ossl_prov_is_running()
        || pecdhctx == NULL
        || vecdh == NULL
        || !EC_KEY_up_ref(vecdh))
        return 0;
    EC_KEY_free(pecdhctx->k);
    pecdhctx->k = vecdh;
    pecdhctx->cofactor_mode = -1;
    pecdhctx->kdf_type = PROV_ECDH_KDF_NONE;
    return ecdh_set_ctx_params(pecdhctx, params)
        && ossl_ec_check_key(pecdhctx->libctx, vecdh, 1);
}

static int ecdh_match_params(const EC_KEY *priv, const EC_KEY *peer)
{
    int ret;
    BN_CTX *ctx = NULL;
    const EC_GROUP *group_priv = EC_KEY_get0_group(priv);
    const EC_GROUP *group_peer = EC_KEY_get0_group(peer);

    ctx = BN_CTX_new_ex(ossl_ec_key_get_libctx(priv));
    if (ctx == NULL) {
        ERR_raise(ERR_LIB_PROV, ERR_R_BN_LIB);
        return 0;
    }
    ret = group_priv != NULL
        && group_peer != NULL
        && EC_GROUP_cmp(group_priv, group_peer, ctx) == 0;
    if (!ret)
        ERR_raise(ERR_LIB_PROV, PROV_R_MISMATCHING_DOMAIN_PARAMETERS);
    BN_CTX_free(ctx);
    return ret;
}

static int ecdh_set_peer(void *vpecdhctx, void *vecdh)
{
    PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;

    if (!ossl_prov_is_running()
        || pecdhctx == NULL
        || vecdh == NULL
        || !ecdh_match_params(pecdhctx->k, vecdh)
        || !ossl_ec_check_key(pecdhctx->libctx, vecdh, 1)
        || !EC_KEY_up_ref(vecdh))
        return 0;

    EC_KEY_free(pecdhctx->peerk);
    pecdhctx->peerk = vecdh;
    return 1;
}

static void ecdh_freectx(void *vpecdhctx)
{
    PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;

    EC_KEY_free(pecdhctx->k);
    EC_KEY_free(pecdhctx->peerk);

    EVP_MD_free(pecdhctx->kdf_md);
    OPENSSL_clear_free(pecdhctx->kdf_ukm, pecdhctx->kdf_ukmlen);

    OPENSSL_free(pecdhctx);
}

static void *ecdh_dupctx(void *vpecdhctx)
{
    PROV_ECDH_CTX *srcctx = (PROV_ECDH_CTX *)vpecdhctx;
    PROV_ECDH_CTX *dstctx;

    if (!ossl_prov_is_running())
        return NULL;

    dstctx = OPENSSL_zalloc(sizeof(*srcctx));
    if (dstctx == NULL)
        return NULL;

    *dstctx = *srcctx;

    /* clear all pointers */

    dstctx->k = NULL;
    dstctx->peerk = NULL;
    dstctx->kdf_md = NULL;
    dstctx->kdf_ukm = NULL;

    /* up-ref all ref-counted objects referenced in dstctx */

    if (srcctx->k != NULL && !EC_KEY_up_ref(srcctx->k))
        goto err;
    else
        dstctx->k = srcctx->k;

    if (srcctx->peerk != NULL && !EC_KEY_up_ref(srcctx->peerk))
        goto err;
    else
        dstctx->peerk = srcctx->peerk;

    if (srcctx->kdf_md != NULL && !EVP_MD_up_ref(srcctx->kdf_md))
        goto err;
    else
        dstctx->kdf_md = srcctx->kdf_md;

    /* Duplicate UKM data if present */
    if (srcctx->kdf_ukm != NULL && srcctx->kdf_ukmlen > 0) {
        dstctx->kdf_ukm = OPENSSL_memdup(srcctx->kdf_ukm,
            srcctx->kdf_ukmlen);
        if (dstctx->kdf_ukm == NULL)
            goto err;
    }

    return dstctx;

err:
    ecdh_freectx(dstctx);
    return NULL;
}

static int ecdh_set_ctx_params(void *vpecdhctx, const OSSL_PARAM params[])
{
    char name[80] = { '\0' }; /* should be big enough */
    char *str = NULL;
    PROV_ECDH_CTX *pectx = (PROV_ECDH_CTX *)vpecdhctx;
    const OSSL_PARAM *p;

    if (pectx == NULL)
        return 0;
    if (params == NULL)
        return 1;

    p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE);
    if (p != NULL) {
        int mode;

        if (!OSSL_PARAM_get_int(p, &mode))
            return 0;

        if (mode < -1 || mode > 1)
            return 0;

        pectx->cofactor_mode = mode;
    }

    p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_TYPE);
    if (p != NULL) {
        str = name;
        if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(name)))
            return 0;

        if (name[0] == '\0')
            pectx->kdf_type = PROV_ECDH_KDF_NONE;
        else if (strcmp(name, OSSL_KDF_NAME_X963KDF) == 0)
            pectx->kdf_type = PROV_ECDH_KDF_X9_63;
        else
            return 0;
    }

    p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_DIGEST);
    if (p != NULL) {
        char mdprops[80] = { '\0' }; /* should be big enough */

        str = name;
        if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(name)))
            return 0;

        str = mdprops;
        p = OSSL_PARAM_locate_const(params,
            OSSL_EXCHANGE_PARAM_KDF_DIGEST_PROPS);

        if (p != NULL) {
            if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(mdprops)))
                return 0;
        }

        EVP_MD_free(pectx->kdf_md);
        pectx->kdf_md = EVP_MD_fetch(pectx->libctx, name, mdprops);
        if (pectx->kdf_md == NULL)
            return 0;
        if (!ossl_digest_is_allowed(pectx->libctx, pectx->kdf_md)) {
            EVP_MD_free(pectx->kdf_md);
            pectx->kdf_md = NULL;
            return 0;
        }
    }

    p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_OUTLEN);
    if (p != NULL) {
        size_t outlen;

        if (!OSSL_PARAM_get_size_t(p, &outlen))
            return 0;
        pectx->kdf_outlen = outlen;
    }

    p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_UKM);
    if (p != NULL) {
        void *tmp_ukm = NULL;
        size_t tmp_ukmlen;

        if (!OSSL_PARAM_get_octet_string(p, &tmp_ukm, 0, &tmp_ukmlen))
            return 0;
        OPENSSL_free(pectx->kdf_ukm);
        pectx->kdf_ukm = tmp_ukm;
        pectx->kdf_ukmlen = tmp_ukmlen;
    }

    return 1;
}

static const OSSL_PARAM known_settable_ctx_params[] = {
    OSSL_PARAM_int(OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE, NULL),
    OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_TYPE, NULL, 0),
    OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST, NULL, 0),
    OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST_PROPS, NULL, 0),
    OSSL_PARAM_size_t(OSSL_EXCHANGE_PARAM_KDF_OUTLEN, NULL),
    OSSL_PARAM_octet_string(OSSL_EXCHANGE_PARAM_KDF_UKM, NULL, 0),
    OSSL_PARAM_END
};

static const OSSL_PARAM *ecdh_settable_ctx_params(ossl_unused void *vpecdhctx,
    ossl_unused void *provctx)
{
    return known_settable_ctx_params;
}

static int ecdh_get_ctx_params(void *vpecdhctx, OSSL_PARAM params[])
{
    PROV_ECDH_CTX *pectx = (PROV_ECDH_CTX *)vpecdhctx;
    OSSL_PARAM *p;

    if (pectx == NULL)
        return 0;

    p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE);
    if (p != NULL) {
        int mode = pectx->cofactor_mode;

        if (mode == -1) {
            /* check what is the default for pecdhctx->k */
            mode = EC_KEY_get_flags(pectx->k) & EC_FLAG_COFACTOR_ECDH ? 1 : 0;
        }

        if (!OSSL_PARAM_set_int(p, mode))
            return 0;
    }

    p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_TYPE);
    if (p != NULL) {
        const char *kdf_type = NULL;

        switch (pectx->kdf_type) {
        case PROV_ECDH_KDF_NONE:
            kdf_type = "";
            break;
        case PROV_ECDH_KDF_X9_63:
            kdf_type = OSSL_KDF_NAME_X963KDF;
            break;
        default:
            return 0;
        }

        if (!OSSL_PARAM_set_utf8_string(p, kdf_type))
            return 0;
    }

    p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_DIGEST);
    if (p != NULL
        && !OSSL_PARAM_set_utf8_string(p, pectx->kdf_md == NULL ? "" : EVP_MD_get0_name(pectx->kdf_md))) {
        return 0;
    }

    p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_OUTLEN);
    if (p != NULL && !OSSL_PARAM_set_size_t(p, pectx->kdf_outlen))
        return 0;

    p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_UKM);
    if (p != NULL && !OSSL_PARAM_set_octet_ptr(p, pectx->kdf_ukm, pectx->kdf_ukmlen))
        return 0;

    return 1;
}

static const OSSL_PARAM known_gettable_ctx_params[] = {
    OSSL_PARAM_int(OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE, NULL),
    OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_TYPE, NULL, 0),
    OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST, NULL, 0),
    OSSL_PARAM_size_t(OSSL_EXCHANGE_PARAM_KDF_OUTLEN, NULL),
    OSSL_PARAM_DEFN(OSSL_EXCHANGE_PARAM_KDF_UKM, OSSL_PARAM_OCTET_PTR,
        NULL, 0),
    OSSL_PARAM_END
};

static const OSSL_PARAM *ecdh_gettable_ctx_params(ossl_unused void *vpecdhctx,
    ossl_unused void *provctx)
{
    return known_gettable_ctx_params;
}

static ossl_inline
    size_t
    ecdh_size(const EC_KEY *k)
{
    size_t degree = 0;
    const EC_GROUP *group;

    if (k == NULL
        || (group = EC_KEY_get0_group(k)) == NULL)
        return 0;

    degree = EC_GROUP_get_degree(group);

    return (degree + 7) / 8;
}

static ossl_inline int ecdh_plain_derive(void *vpecdhctx, unsigned char *secret,
    size_t *psecretlen, size_t outlen)
{
    PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;
    int retlen, ret = 0;
    size_t ecdhsize, size;
    const EC_POINT *ppubkey = NULL;
    EC_KEY *privk = NULL;
    const EC_GROUP *group;
    const BIGNUM *cofactor;
    int key_cofactor_mode;

    if (pecdhctx->k == NULL || pecdhctx->peerk == NULL) {
        ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);
        return 0;
    }

    ecdhsize = ecdh_size(pecdhctx->k);
    if (secret == NULL) {
        *psecretlen = ecdhsize;
        return 1;
    }

    if ((group = EC_KEY_get0_group(pecdhctx->k)) == NULL
        || (cofactor = EC_GROUP_get0_cofactor(group)) == NULL)
        return 0;

    /*
     * NB: unlike PKCS#3 DH, if outlen is less than maximum size this is not
     * an error, the result is truncated.
     */
    size = outlen < ecdhsize ? outlen : ecdhsize;

    /*
     * The ctx->cofactor_mode flag has precedence over the
     * cofactor_mode flag set on ctx->k.
     *
     * - if ctx->cofactor_mode == -1, use ctx->k directly
     * - if ctx->cofactor_mode == key_cofactor_mode, use ctx->k directly
     * - if ctx->cofactor_mode != key_cofactor_mode:
     *     - if ctx->k->cofactor == 1, the cofactor_mode flag is irrelevant, use
     *          ctx->k directly
     *     - if ctx->k->cofactor != 1, use a duplicate of ctx->k with the flag
     *          set to ctx->cofactor_mode
     */
    key_cofactor_mode = (EC_KEY_get_flags(pecdhctx->k) & EC_FLAG_COFACTOR_ECDH) ? 1 : 0;
    if (pecdhctx->cofactor_mode != -1
        && pecdhctx->cofactor_mode != key_cofactor_mode
        && !BN_is_one(cofactor)) {
        if ((privk = EC_KEY_dup(pecdhctx->k)) == NULL)
            return 0;

        if (pecdhctx->cofactor_mode == 1)
            EC_KEY_set_flags(privk, EC_FLAG_COFACTOR_ECDH);
        else
            EC_KEY_clear_flags(privk, EC_FLAG_COFACTOR_ECDH);
    } else {
        privk = pecdhctx->k;
    }

    ppubkey = EC_KEY_get0_public_key(pecdhctx->peerk);

    retlen = ECDH_compute_key(secret, size, ppubkey, privk, NULL);

    if (retlen <= 0)
        goto end;

    *psecretlen = retlen;
    ret = 1;

end:
    if (privk != pecdhctx->k)
        EC_KEY_free(privk);
    return ret;
}

static ossl_inline int ecdh_X9_63_kdf_derive(void *vpecdhctx, unsigned char *secret,
    size_t *psecretlen, size_t outlen)
{
    PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;
    unsigned char *stmp = NULL;
    size_t stmplen;
    int ret = 0;

    if (secret == NULL) {
        *psecretlen = pecdhctx->kdf_outlen;
        return 1;
    }

    if (pecdhctx->kdf_outlen > outlen) {
        ERR_raise(ERR_LIB_PROV, PROV_R_OUTPUT_BUFFER_TOO_SMALL);
        return 0;
    }
    if (!ecdh_plain_derive(vpecdhctx, NULL, &stmplen, 0))
        return 0;
    if ((stmp = OPENSSL_secure_malloc(stmplen)) == NULL)
        return 0;
    if (!ecdh_plain_derive(vpecdhctx, stmp, &stmplen, stmplen))
        goto err;

    /* Do KDF stuff */
    if (!ossl_ecdh_kdf_X9_63(secret, pecdhctx->kdf_outlen,
            stmp, stmplen,
            pecdhctx->kdf_ukm,
            pecdhctx->kdf_ukmlen,
            pecdhctx->kdf_md,
            pecdhctx->libctx, NULL))
        goto err;
    *psecretlen = pecdhctx->kdf_outlen;
    ret = 1;

err:
    OPENSSL_secure_clear_free(stmp, stmplen);
    return ret;
}

static int ecdh_derive(void *vpecdhctx, unsigned char *secret,
    size_t *psecretlen, size_t outlen)
{
    PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;

    switch (pecdhctx->kdf_type) {
    case PROV_ECDH_KDF_NONE:
        return ecdh_plain_derive(vpecdhctx, secret, psecretlen, outlen);
    case PROV_ECDH_KDF_X9_63:
        return ecdh_X9_63_kdf_derive(vpecdhctx, secret, psecretlen, outlen);
    default:
        break;
    }
    return 0;
}

const OSSL_DISPATCH ossl_ecdh_keyexch_functions[] = {
    { OSSL_FUNC_KEYEXCH_NEWCTX, (void (*)(void))ecdh_newctx },
    { OSSL_FUNC_KEYEXCH_INIT, (void (*)(void))ecdh_init },
    { OSSL_FUNC_KEYEXCH_DERIVE, (void (*)(void))ecdh_derive },
    { OSSL_FUNC_KEYEXCH_SET_PEER, (void (*)(void))ecdh_set_peer },
    { OSSL_FUNC_KEYEXCH_FREECTX, (void (*)(void))ecdh_freectx },
    { OSSL_FUNC_KEYEXCH_DUPCTX, (void (*)(void))ecdh_dupctx },
    { OSSL_FUNC_KEYEXCH_SET_CTX_PARAMS, (void (*)(void))ecdh_set_ctx_params },
    { OSSL_FUNC_KEYEXCH_SETTABLE_CTX_PARAMS,
        (void (*)(void))ecdh_settable_ctx_params },
    { OSSL_FUNC_KEYEXCH_GET_CTX_PARAMS, (void (*)(void))ecdh_get_ctx_params },
    { OSSL_FUNC_KEYEXCH_GETTABLE_CTX_PARAMS,
        (void (*)(void))ecdh_gettable_ctx_params },
    OSSL_DISPATCH_END
};

Coverage Report

Created: 2025-12-31 06:58

Line	Count	Source
1		/*
2		* Copyright 2020-2023 The OpenSSL Project Authors. All Rights Reserved.
3		*
4		* Licensed under the Apache License 2.0 (the "License"). You may not use
5		* this file except in compliance with the License. You can obtain a copy
6		* in the file LICENSE in the source distribution or at
7		* https://www.openssl.org/source/license.html
8		*/
9
10		/*
11		* ECDH low level APIs are deprecated for public use, but still ok for
12		* internal use.
13		*/
14		#include "internal/deprecated.h"
15
16		#include <string.h>
17		#include <openssl/crypto.h>
18		#include <openssl/evp.h>
19		#include <openssl/core_dispatch.h>
20		#include <openssl/core_names.h>
21		#include <openssl/ec.h>
22		#include <openssl/params.h>
23		#include <openssl/err.h>
24		#include <openssl/proverr.h>
25		#include "prov/provider_ctx.h"
26		#include "prov/providercommon.h"
27		#include "prov/implementations.h"
28		#include "prov/securitycheck.h"
29		#include "crypto/ec.h" /* ossl_ecdh_kdf_X9_63() */
30
31		static OSSL_FUNC_keyexch_newctx_fn ecdh_newctx;
32		static OSSL_FUNC_keyexch_init_fn ecdh_init;
33		static OSSL_FUNC_keyexch_set_peer_fn ecdh_set_peer;
34		static OSSL_FUNC_keyexch_derive_fn ecdh_derive;
35		static OSSL_FUNC_keyexch_freectx_fn ecdh_freectx;
36		static OSSL_FUNC_keyexch_dupctx_fn ecdh_dupctx;
37		static OSSL_FUNC_keyexch_set_ctx_params_fn ecdh_set_ctx_params;
38		static OSSL_FUNC_keyexch_settable_ctx_params_fn ecdh_settable_ctx_params;
39		static OSSL_FUNC_keyexch_get_ctx_params_fn ecdh_get_ctx_params;
40		static OSSL_FUNC_keyexch_gettable_ctx_params_fn ecdh_gettable_ctx_params;
41
42		enum kdf_type {
43		PROV_ECDH_KDF_NONE = 0,
44		PROV_ECDH_KDF_X9_63
45		};
46
47		/*
48		* What's passed as an actual key is defined by the KEYMGMT interface.
49		* We happen to know that our KEYMGMT simply passes EC_KEY structures, so
50		* we use that here too.
51		*/
52
53		typedef struct {
54		OSSL_LIB_CTX *libctx;
55
56		EC_KEY *k;
57		EC_KEY *peerk;
58
59		/*
60		* ECDH cofactor mode:
61		*
62		* . 0 disabled
63		* . 1 enabled
64		* . -1 use cofactor mode set for k
65		*/
66		int cofactor_mode;
67
68		/************
69		* ECDH KDF *
70		************/
71		/* KDF (if any) to use for ECDH */
72		enum kdf_type kdf_type;
73		/* Message digest to use for key derivation */
74		EVP_MD *kdf_md;
75		/* User key material */
76		unsigned char *kdf_ukm;
77		size_t kdf_ukmlen;
78		/* KDF output length */
79		size_t kdf_outlen;
80		} PROV_ECDH_CTX;
81
82		static void ecdh_newctx(void provctx)
83	4.31k	{
84	4.31k	PROV_ECDH_CTX *pectx;
85
86	4.31k	if (!ossl_prov_is_running())
87	0	return NULL;
88
89	4.31k	pectx = OPENSSL_zalloc(sizeof(*pectx));
90	4.31k	if (pectx == NULL)
91	0	return NULL;
92
93	4.31k	pectx->libctx = PROV_LIBCTX_OF(provctx);
94	4.31k	pectx->cofactor_mode = -1;
95	4.31k	pectx->kdf_type = PROV_ECDH_KDF_NONE;
96
97	4.31k	return (void *)pectx;
98	4.31k	}
99
100		static int ecdh_init(void vpecdhctx, void vecdh, const OSSL_PARAM params[])
101	1.27k	{
102	1.27k	PROV_ECDH_CTX pecdhctx = (PROV_ECDH_CTX )vpecdhctx;
103
104	1.27k	if (!ossl_prov_is_running()
105	1.27k	\|\| pecdhctx == NULL
106	1.27k	\|\| vecdh == NULL
107	1.27k	\|\| !EC_KEY_up_ref(vecdh))
108	0	return 0;
109	1.27k	EC_KEY_free(pecdhctx->k);
110	1.27k	pecdhctx->k = vecdh;
111	1.27k	pecdhctx->cofactor_mode = -1;
112	1.27k	pecdhctx->kdf_type = PROV_ECDH_KDF_NONE;
113	1.27k	return ecdh_set_ctx_params(pecdhctx, params)
114	1.27k	&& ossl_ec_check_key(pecdhctx->libctx, vecdh, 1);
115	1.27k	}
116
117		static int ecdh_match_params(const EC_KEY priv, const EC_KEY peer)
118	4.28k	{
119	4.28k	int ret;
120	4.28k	BN_CTX *ctx = NULL;
121	4.28k	const EC_GROUP *group_priv = EC_KEY_get0_group(priv);
122	4.28k	const EC_GROUP *group_peer = EC_KEY_get0_group(peer);
123
124	4.28k	ctx = BN_CTX_new_ex(ossl_ec_key_get_libctx(priv));
125	4.28k	if (ctx == NULL) {
126	0	ERR_raise(ERR_LIB_PROV, ERR_R_BN_LIB);
127	0	return 0;
128	0	}
129	4.28k	ret = group_priv != NULL
130	4.28k	&& group_peer != NULL
131	4.28k	&& EC_GROUP_cmp(group_priv, group_peer, ctx) == 0;
132	4.28k	if (!ret)
133	4.28k	ERR_raise(ERR_LIB_PROV, PROV_R_MISMATCHING_DOMAIN_PARAMETERS);
134	4.28k	BN_CTX_free(ctx);
135	4.28k	return ret;
136	4.28k	}
137
138		static int ecdh_set_peer(void vpecdhctx, void vecdh)
139	1.26k	{
140	1.26k	PROV_ECDH_CTX pecdhctx = (PROV_ECDH_CTX )vpecdhctx;
141
142	1.26k	if (!ossl_prov_is_running()
143	1.26k	\|\| pecdhctx == NULL
144	1.26k	\|\| vecdh == NULL
145	1.26k	\|\| !ecdh_match_params(pecdhctx->k, vecdh)
146	1.26k	\|\| !ossl_ec_check_key(pecdhctx->libctx, vecdh, 1)
147	1.26k	\|\| !EC_KEY_up_ref(vecdh))
148	0	return 0;
149
150	1.26k	EC_KEY_free(pecdhctx->peerk);
151	1.26k	pecdhctx->peerk = vecdh;
152	1.26k	return 1;
153	1.26k	}
154
155		static void ecdh_freectx(void *vpecdhctx)
156	4.31k	{
157	4.31k	PROV_ECDH_CTX pecdhctx = (PROV_ECDH_CTX )vpecdhctx;
158
159	4.31k	EC_KEY_free(pecdhctx->k);
160	4.31k	EC_KEY_free(pecdhctx->peerk);
161
162	4.31k	EVP_MD_free(pecdhctx->kdf_md);
163	4.31k	OPENSSL_clear_free(pecdhctx->kdf_ukm, pecdhctx->kdf_ukmlen);
164
165	4.31k	OPENSSL_free(pecdhctx);
166	4.31k	}
167
168		static void ecdh_dupctx(void vpecdhctx)
169	0	{
170	0	PROV_ECDH_CTX srcctx = (PROV_ECDH_CTX )vpecdhctx;
171	0	PROV_ECDH_CTX *dstctx;
172
173	0	if (!ossl_prov_is_running())
174	0	return NULL;
175
176	0	dstctx = OPENSSL_zalloc(sizeof(*srcctx));
177	0	if (dstctx == NULL)
178	0	return NULL;
179
180	0	dstctx = srcctx;
181
182		/* clear all pointers */
183
184	0	dstctx->k = NULL;
185	0	dstctx->peerk = NULL;
186	0	dstctx->kdf_md = NULL;
187	0	dstctx->kdf_ukm = NULL;
188
189		/* up-ref all ref-counted objects referenced in dstctx */
190
191	0	if (srcctx->k != NULL && !EC_KEY_up_ref(srcctx->k))
192	0	goto err;
193	0	else
194	0	dstctx->k = srcctx->k;
195
196	0	if (srcctx->peerk != NULL && !EC_KEY_up_ref(srcctx->peerk))
197	0	goto err;
198	0	else
199	0	dstctx->peerk = srcctx->peerk;
200
201	0	if (srcctx->kdf_md != NULL && !EVP_MD_up_ref(srcctx->kdf_md))
202	0	goto err;
203	0	else
204	0	dstctx->kdf_md = srcctx->kdf_md;
205
206		/* Duplicate UKM data if present */
207	0	if (srcctx->kdf_ukm != NULL && srcctx->kdf_ukmlen > 0) {
208	0	dstctx->kdf_ukm = OPENSSL_memdup(srcctx->kdf_ukm,
209	0	srcctx->kdf_ukmlen);
210	0	if (dstctx->kdf_ukm == NULL)
211	0	goto err;
212	0	}
213
214	0	return dstctx;
215
216	0	err:
217	0	ecdh_freectx(dstctx);
218	0	return NULL;
219	0	}
220
221		static int ecdh_set_ctx_params(void *vpecdhctx, const OSSL_PARAM params[])
222	658	{
223	658	char name[80] = { '\0' }; /* should be big enough */
224	658	char *str = NULL;
225	658	PROV_ECDH_CTX pectx = (PROV_ECDH_CTX )vpecdhctx;
226	658	const OSSL_PARAM *p;
227
228	658	if (pectx == NULL)
229	0	return 0;
230	658	if (params == NULL)
231	658	return 1;
232
233	0	p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE);
234	0	if (p != NULL) {
235	0	int mode;
236
237	0	if (!OSSL_PARAM_get_int(p, &mode))
238	0	return 0;
239
240	0	if (mode < -1 \|\| mode > 1)
241	0	return 0;
242
243	0	pectx->cofactor_mode = mode;
244	0	}
245
246	0	p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_TYPE);
247	0	if (p != NULL) {
248	0	str = name;
249	0	if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(name)))
250	0	return 0;
251
252	0	if (name[0] == '\0')
253	0	pectx->kdf_type = PROV_ECDH_KDF_NONE;
254	0	else if (strcmp(name, OSSL_KDF_NAME_X963KDF) == 0)
255	0	pectx->kdf_type = PROV_ECDH_KDF_X9_63;
256	0	else
257	0	return 0;
258	0	}
259
260	0	p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_DIGEST);
261	0	if (p != NULL) {
262	0	char mdprops[80] = { '\0' }; /* should be big enough */
263
264	0	str = name;
265	0	if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(name)))
266	0	return 0;
267
268	0	str = mdprops;
269	0	p = OSSL_PARAM_locate_const(params,
270	0	OSSL_EXCHANGE_PARAM_KDF_DIGEST_PROPS);
271
272	0	if (p != NULL) {
273	0	if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(mdprops)))
274	0	return 0;
275	0	}
276
277	0	EVP_MD_free(pectx->kdf_md);
278	0	pectx->kdf_md = EVP_MD_fetch(pectx->libctx, name, mdprops);
279	0	if (pectx->kdf_md == NULL)
280	0	return 0;
281	0	if (!ossl_digest_is_allowed(pectx->libctx, pectx->kdf_md)) {
282	0	EVP_MD_free(pectx->kdf_md);
283	0	pectx->kdf_md = NULL;
284	0	return 0;
285	0	}
286	0	}
287
288	0	p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_OUTLEN);
289	0	if (p != NULL) {
290	0	size_t outlen;
291
292	0	if (!OSSL_PARAM_get_size_t(p, &outlen))
293	0	return 0;
294	0	pectx->kdf_outlen = outlen;
295	0	}
296
297	0	p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_UKM);
298	0	if (p != NULL) {
299	0	void *tmp_ukm = NULL;
300	0	size_t tmp_ukmlen;
301
302	0	if (!OSSL_PARAM_get_octet_string(p, &tmp_ukm, 0, &tmp_ukmlen))
303	0	return 0;
304	0	OPENSSL_free(pectx->kdf_ukm);
305	0	pectx->kdf_ukm = tmp_ukm;
306	0	pectx->kdf_ukmlen = tmp_ukmlen;
307	0	}
308
309	0	return 1;
310	0	}
311
312		static const OSSL_PARAM known_settable_ctx_params[] = {
313		OSSL_PARAM_int(OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE, NULL),
314		OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_TYPE, NULL, 0),
315		OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST, NULL, 0),
316		OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST_PROPS, NULL, 0),
317		OSSL_PARAM_size_t(OSSL_EXCHANGE_PARAM_KDF_OUTLEN, NULL),
318		OSSL_PARAM_octet_string(OSSL_EXCHANGE_PARAM_KDF_UKM, NULL, 0),
319		OSSL_PARAM_END
320		};
321
322		static const OSSL_PARAM ecdh_settable_ctx_params(ossl_unused void vpecdhctx,
323		ossl_unused void *provctx)
324	25	{
325	25	return known_settable_ctx_params;
326	25	}
327
328		static int ecdh_get_ctx_params(void *vpecdhctx, OSSL_PARAM params[])
329	0	{
330	0	PROV_ECDH_CTX pectx = (PROV_ECDH_CTX )vpecdhctx;
331	0	OSSL_PARAM *p;
332
333	0	if (pectx == NULL)
334	0	return 0;
335
336	0	p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE);
337	0	if (p != NULL) {
338	0	int mode = pectx->cofactor_mode;
339
340	0	if (mode == -1) {
341		/* check what is the default for pecdhctx->k */
342	0	mode = EC_KEY_get_flags(pectx->k) & EC_FLAG_COFACTOR_ECDH ? 1 : 0;
343	0	}
344
345	0	if (!OSSL_PARAM_set_int(p, mode))
346	0	return 0;
347	0	}
348
349	0	p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_TYPE);
350	0	if (p != NULL) {
351	0	const char *kdf_type = NULL;
352
353	0	switch (pectx->kdf_type) {
354	0	case PROV_ECDH_KDF_NONE:
355	0	kdf_type = "";
356	0	break;
357	0	case PROV_ECDH_KDF_X9_63:
358	0	kdf_type = OSSL_KDF_NAME_X963KDF;
359	0	break;
360	0	default:
361	0	return 0;
362	0	}
363
364	0	if (!OSSL_PARAM_set_utf8_string(p, kdf_type))
365	0	return 0;
366	0	}
367
368	0	p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_DIGEST);
369	0	if (p != NULL
370	0	&& !OSSL_PARAM_set_utf8_string(p, pectx->kdf_md == NULL ? "" : EVP_MD_get0_name(pectx->kdf_md))) {
371	0	return 0;
372	0	}
373
374	0	p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_OUTLEN);
375	0	if (p != NULL && !OSSL_PARAM_set_size_t(p, pectx->kdf_outlen))
376	0	return 0;
377
378	0	p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_UKM);
379	0	if (p != NULL && !OSSL_PARAM_set_octet_ptr(p, pectx->kdf_ukm, pectx->kdf_ukmlen))
380	0	return 0;
381
382	0	return 1;
383	0	}
384
385		static const OSSL_PARAM known_gettable_ctx_params[] = {
386		OSSL_PARAM_int(OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE, NULL),
387		OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_TYPE, NULL, 0),
388		OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST, NULL, 0),
389		OSSL_PARAM_size_t(OSSL_EXCHANGE_PARAM_KDF_OUTLEN, NULL),
390		OSSL_PARAM_DEFN(OSSL_EXCHANGE_PARAM_KDF_UKM, OSSL_PARAM_OCTET_PTR,
391		NULL, 0),
392		OSSL_PARAM_END
393		};
394
395		static const OSSL_PARAM ecdh_gettable_ctx_params(ossl_unused void vpecdhctx,
396		ossl_unused void *provctx)
397	0	{
398	0	return known_gettable_ctx_params;
399	0	}
400
401		static ossl_inline
402		size_t
403		ecdh_size(const EC_KEY *k)
404	8.57k	{
405	8.57k	size_t degree = 0;
406	8.57k	const EC_GROUP *group;
407
408	8.57k	if (k == NULL
409	8.57k	\|\| (group = EC_KEY_get0_group(k)) == NULL)
410	0	return 0;
411
412	8.57k	degree = EC_GROUP_get_degree(group);
413
414	8.57k	return (degree + 7) / 8;
415	8.57k	}
416
417		static ossl_inline int ecdh_plain_derive(void vpecdhctx, unsigned char secret,
418		size_t *psecretlen, size_t outlen)
419	2.53k	{
420	2.53k	PROV_ECDH_CTX pecdhctx = (PROV_ECDH_CTX )vpecdhctx;
421	2.53k	int retlen, ret = 0;
422	2.53k	size_t ecdhsize, size;
423	2.53k	const EC_POINT *ppubkey = NULL;
424	2.53k	EC_KEY *privk = NULL;
425	2.53k	const EC_GROUP *group;
426	2.53k	const BIGNUM *cofactor;
427	2.53k	int key_cofactor_mode;
428
429	2.53k	if (pecdhctx->k == NULL \|\| pecdhctx->peerk == NULL) {
430	0	ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);
431	0	return 0;
432	0	}
433
434	2.53k	ecdhsize = ecdh_size(pecdhctx->k);
435	2.53k	if (secret == NULL) {
436	1.26k	*psecretlen = ecdhsize;
437	1.26k	return 1;
438	1.26k	}
439
440	1.26k	if ((group = EC_KEY_get0_group(pecdhctx->k)) == NULL
441	1.26k	\|\| (cofactor = EC_GROUP_get0_cofactor(group)) == NULL)
442	0	return 0;
443
444		/*
445		* NB: unlike PKCS#3 DH, if outlen is less than maximum size this is not
446		* an error, the result is truncated.
447		*/
448	1.26k	size = outlen < ecdhsize ? outlen : ecdhsize;
449
450		/*
451		* The ctx->cofactor_mode flag has precedence over the
452		* cofactor_mode flag set on ctx->k.
453		*
454		* - if ctx->cofactor_mode == -1, use ctx->k directly
455		* - if ctx->cofactor_mode == key_cofactor_mode, use ctx->k directly
456		* - if ctx->cofactor_mode != key_cofactor_mode:
457		* - if ctx->k->cofactor == 1, the cofactor_mode flag is irrelevant, use
458		* ctx->k directly
459		* - if ctx->k->cofactor != 1, use a duplicate of ctx->k with the flag
460		* set to ctx->cofactor_mode
461		*/
462	1.26k	key_cofactor_mode = (EC_KEY_get_flags(pecdhctx->k) & EC_FLAG_COFACTOR_ECDH) ? 1 : 0;
463	1.26k	if (pecdhctx->cofactor_mode != -1
464	0	&& pecdhctx->cofactor_mode != key_cofactor_mode
465	0	&& !BN_is_one(cofactor)) {
466	0	if ((privk = EC_KEY_dup(pecdhctx->k)) == NULL)
467	0	return 0;
468
469	0	if (pecdhctx->cofactor_mode == 1)
470	0	EC_KEY_set_flags(privk, EC_FLAG_COFACTOR_ECDH);
471	0	else
472	0	EC_KEY_clear_flags(privk, EC_FLAG_COFACTOR_ECDH);
473	1.26k	} else {
474	1.26k	privk = pecdhctx->k;
475	1.26k	}
476
477	1.26k	ppubkey = EC_KEY_get0_public_key(pecdhctx->peerk);
478
479	1.26k	retlen = ECDH_compute_key(secret, size, ppubkey, privk, NULL);
480
481	1.26k	if (retlen <= 0)
482	0	goto end;
483
484	1.26k	*psecretlen = retlen;
485	1.26k	ret = 1;
486
487	1.26k	end:
488	1.26k	if (privk != pecdhctx->k)
489	0	EC_KEY_free(privk);
490	1.26k	return ret;
491	1.26k	}
492
493		static ossl_inline int ecdh_X9_63_kdf_derive(void vpecdhctx, unsigned char secret,
494		size_t *psecretlen, size_t outlen)
495	0	{
496	0	PROV_ECDH_CTX pecdhctx = (PROV_ECDH_CTX )vpecdhctx;
497	0	unsigned char *stmp = NULL;
498	0	size_t stmplen;
499	0	int ret = 0;
500
501	0	if (secret == NULL) {
502	0	*psecretlen = pecdhctx->kdf_outlen;
503	0	return 1;
504	0	}
505
506	0	if (pecdhctx->kdf_outlen > outlen) {
507	0	ERR_raise(ERR_LIB_PROV, PROV_R_OUTPUT_BUFFER_TOO_SMALL);
508	0	return 0;
509	0	}
510	0	if (!ecdh_plain_derive(vpecdhctx, NULL, &stmplen, 0))
511	0	return 0;
512	0	if ((stmp = OPENSSL_secure_malloc(stmplen)) == NULL)
513	0	return 0;
514	0	if (!ecdh_plain_derive(vpecdhctx, stmp, &stmplen, stmplen))
515	0	goto err;
516
517		/* Do KDF stuff */
518	0	if (!ossl_ecdh_kdf_X9_63(secret, pecdhctx->kdf_outlen,
519	0	stmp, stmplen,
520	0	pecdhctx->kdf_ukm,
521	0	pecdhctx->kdf_ukmlen,
522	0	pecdhctx->kdf_md,
523	0	pecdhctx->libctx, NULL))
524	0	goto err;
525	0	*psecretlen = pecdhctx->kdf_outlen;
526	0	ret = 1;
527
528	0	err:
529	0	OPENSSL_secure_clear_free(stmp, stmplen);
530	0	return ret;
531	0	}
532
533		static int ecdh_derive(void vpecdhctx, unsigned char secret,
534		size_t *psecretlen, size_t outlen)
535	8.57k	{
536	8.57k	PROV_ECDH_CTX pecdhctx = (PROV_ECDH_CTX )vpecdhctx;
537
538	8.57k	switch (pecdhctx->kdf_type) {
539	8.57k	case PROV_ECDH_KDF_NONE:
540	8.57k	return ecdh_plain_derive(vpecdhctx, secret, psecretlen, outlen);
541	0	case PROV_ECDH_KDF_X9_63:
542	0	return ecdh_X9_63_kdf_derive(vpecdhctx, secret, psecretlen, outlen);
543	0	default:
544	0	break;
545	8.57k	}
546	0	return 0;
547	8.57k	}
548
549		const OSSL_DISPATCH ossl_ecdh_keyexch_functions[] = {
550		{ OSSL_FUNC_KEYEXCH_NEWCTX, (void (*)(void))ecdh_newctx },
551		{ OSSL_FUNC_KEYEXCH_INIT, (void (*)(void))ecdh_init },
552		{ OSSL_FUNC_KEYEXCH_DERIVE, (void (*)(void))ecdh_derive },
553		{ OSSL_FUNC_KEYEXCH_SET_PEER, (void (*)(void))ecdh_set_peer },
554		{ OSSL_FUNC_KEYEXCH_FREECTX, (void (*)(void))ecdh_freectx },
555		{ OSSL_FUNC_KEYEXCH_DUPCTX, (void (*)(void))ecdh_dupctx },
556		{ OSSL_FUNC_KEYEXCH_SET_CTX_PARAMS, (void (*)(void))ecdh_set_ctx_params },
557		{ OSSL_FUNC_KEYEXCH_SETTABLE_CTX_PARAMS,
558		(void (*)(void))ecdh_settable_ctx_params },
559		{ OSSL_FUNC_KEYEXCH_GET_CTX_PARAMS, (void (*)(void))ecdh_get_ctx_params },
560		{ OSSL_FUNC_KEYEXCH_GETTABLE_CTX_PARAMS,
561		(void (*)(void))ecdh_gettable_ctx_params },
562		OSSL_DISPATCH_END
563		};