/src/openssl31/providers/implementations/exchange/ecdh_exch.c

Source (jump to first uncovered line)
/*
 * Copyright 2020-2022 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_MALLOC_FAILURE);
        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) {
        ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
        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 },
    { 0, NULL }
};

Coverage Report

Created: 2025-06-13 06:58

Line	Count	Source (jump to first uncovered line)
1		/*
2		* Copyright 2020-2022 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
83		void ecdh_newctx(void provctx)
84	2.12k	{
85	2.12k	PROV_ECDH_CTX *pectx;
86
87	2.12k	if (!ossl_prov_is_running())
88	0	return NULL;
89
90	2.12k	pectx = OPENSSL_zalloc(sizeof(*pectx));
91	2.12k	if (pectx == NULL)
92	0	return NULL;
93
94	2.12k	pectx->libctx = PROV_LIBCTX_OF(provctx);
95	2.12k	pectx->cofactor_mode = -1;
96	2.12k	pectx->kdf_type = PROV_ECDH_KDF_NONE;
97
98	2.12k	return (void *)pectx;
99	2.12k	}
100
101		static
102		int ecdh_init(void vpecdhctx, void vecdh, const OSSL_PARAM params[])
103	1.56k	{
104	1.56k	PROV_ECDH_CTX pecdhctx = (PROV_ECDH_CTX )vpecdhctx;
105
106	1.56k	if (!ossl_prov_is_running()
107	1.56k	\|\| pecdhctx == NULL
108	1.56k	\|\| vecdh == NULL
109	1.56k	\|\| !EC_KEY_up_ref(vecdh))
110	0	return 0;
111	1.56k	EC_KEY_free(pecdhctx->k);
112	1.56k	pecdhctx->k = vecdh;
113	1.56k	pecdhctx->cofactor_mode = -1;
114	1.56k	pecdhctx->kdf_type = PROV_ECDH_KDF_NONE;
115	1.56k	return ecdh_set_ctx_params(pecdhctx, params)
116	1.56k	&& ossl_ec_check_key(pecdhctx->libctx, vecdh, 1);
117	1.56k	}
118
119		static
120		int ecdh_match_params(const EC_KEY priv, const EC_KEY peer)
121	2.10k	{
122	2.10k	int ret;
123	2.10k	BN_CTX *ctx = NULL;
124	2.10k	const EC_GROUP *group_priv = EC_KEY_get0_group(priv);
125	2.10k	const EC_GROUP *group_peer = EC_KEY_get0_group(peer);
126
127	2.10k	ctx = BN_CTX_new_ex(ossl_ec_key_get_libctx(priv));
128	2.10k	if (ctx == NULL) {
129	0	ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
130	0	return 0;
131	0	}
132	2.10k	ret = group_priv != NULL
133	2.10k	&& group_peer != NULL
134	2.10k	&& EC_GROUP_cmp(group_priv, group_peer, ctx) == 0;
135	2.10k	if (!ret)
136	2.10k	ERR_raise(ERR_LIB_PROV, PROV_R_MISMATCHING_DOMAIN_PARAMETERS);
137	2.10k	BN_CTX_free(ctx);
138	2.10k	return ret;
139	2.10k	}
140
141		static
142		int ecdh_set_peer(void vpecdhctx, void vecdh)
143	1.54k	{
144	1.54k	PROV_ECDH_CTX pecdhctx = (PROV_ECDH_CTX )vpecdhctx;
145
146	1.54k	if (!ossl_prov_is_running()
147	1.54k	\|\| pecdhctx == NULL
148	1.54k	\|\| vecdh == NULL
149	1.54k	\|\| !ecdh_match_params(pecdhctx->k, vecdh)
150	1.54k	\|\| !ossl_ec_check_key(pecdhctx->libctx, vecdh, 1)
151	1.54k	\|\| !EC_KEY_up_ref(vecdh))
152	0	return 0;
153
154	1.54k	EC_KEY_free(pecdhctx->peerk);
155	1.54k	pecdhctx->peerk = vecdh;
156	1.54k	return 1;
157	1.54k	}
158
159		static
160		void ecdh_freectx(void *vpecdhctx)
161	2.12k	{
162	2.12k	PROV_ECDH_CTX pecdhctx = (PROV_ECDH_CTX )vpecdhctx;
163
164	2.12k	EC_KEY_free(pecdhctx->k);
165	2.12k	EC_KEY_free(pecdhctx->peerk);
166
167	2.12k	EVP_MD_free(pecdhctx->kdf_md);
168	2.12k	OPENSSL_clear_free(pecdhctx->kdf_ukm, pecdhctx->kdf_ukmlen);
169
170	2.12k	OPENSSL_free(pecdhctx);
171	2.12k	}
172
173		static
174		void ecdh_dupctx(void vpecdhctx)
175	0	{
176	0	PROV_ECDH_CTX srcctx = (PROV_ECDH_CTX )vpecdhctx;
177	0	PROV_ECDH_CTX *dstctx;
178
179	0	if (!ossl_prov_is_running())
180	0	return NULL;
181
182	0	dstctx = OPENSSL_zalloc(sizeof(*srcctx));
183	0	if (dstctx == NULL)
184	0	return NULL;
185
186	0	dstctx = srcctx;
187
188		/* clear all pointers */
189
190	0	dstctx->k= NULL;
191	0	dstctx->peerk = NULL;
192	0	dstctx->kdf_md = NULL;
193	0	dstctx->kdf_ukm = NULL;
194
195		/* up-ref all ref-counted objects referenced in dstctx */
196
197	0	if (srcctx->k != NULL && !EC_KEY_up_ref(srcctx->k))
198	0	goto err;
199	0	else
200	0	dstctx->k = srcctx->k;
201
202	0	if (srcctx->peerk != NULL && !EC_KEY_up_ref(srcctx->peerk))
203	0	goto err;
204	0	else
205	0	dstctx->peerk = srcctx->peerk;
206
207	0	if (srcctx->kdf_md != NULL && !EVP_MD_up_ref(srcctx->kdf_md))
208	0	goto err;
209	0	else
210	0	dstctx->kdf_md = srcctx->kdf_md;
211
212		/* Duplicate UKM data if present */
213	0	if (srcctx->kdf_ukm != NULL && srcctx->kdf_ukmlen > 0) {
214	0	dstctx->kdf_ukm = OPENSSL_memdup(srcctx->kdf_ukm,
215	0	srcctx->kdf_ukmlen);
216	0	if (dstctx->kdf_ukm == NULL)
217	0	goto err;
218	0	}
219
220	0	return dstctx;
221
222	0	err:
223	0	ecdh_freectx(dstctx);
224	0	return NULL;
225	0	}
226
227		static
228		int ecdh_set_ctx_params(void *vpecdhctx, const OSSL_PARAM params[])
229	1.03k	{
230	1.03k	char name[80] = { '\0' }; /* should be big enough */
231	1.03k	char *str = NULL;
232	1.03k	PROV_ECDH_CTX pectx = (PROV_ECDH_CTX )vpecdhctx;
233	1.03k	const OSSL_PARAM *p;
234
235	1.03k	if (pectx == NULL)
236	0	return 0;
237	1.03k	if (params == NULL)
238	1.03k	return 1;
239
240	0	p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE);
241	0	if (p != NULL) {
242	0	int mode;
243
244	0	if (!OSSL_PARAM_get_int(p, &mode))
245	0	return 0;
246
247	0	if (mode < -1 \|\| mode > 1)
248	0	return 0;
249
250	0	pectx->cofactor_mode = mode;
251	0	}
252
253	0	p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_TYPE);
254	0	if (p != NULL) {
255	0	str = name;
256	0	if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(name)))
257	0	return 0;
258
259	0	if (name[0] == '\0')
260	0	pectx->kdf_type = PROV_ECDH_KDF_NONE;
261	0	else if (strcmp(name, OSSL_KDF_NAME_X963KDF) == 0)
262	0	pectx->kdf_type = PROV_ECDH_KDF_X9_63;
263	0	else
264	0	return 0;
265	0	}
266
267	0	p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_DIGEST);
268	0	if (p != NULL) {
269	0	char mdprops[80] = { '\0' }; /* should be big enough */
270
271	0	str = name;
272	0	if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(name)))
273	0	return 0;
274
275	0	str = mdprops;
276	0	p = OSSL_PARAM_locate_const(params,
277	0	OSSL_EXCHANGE_PARAM_KDF_DIGEST_PROPS);
278
279	0	if (p != NULL) {
280	0	if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(mdprops)))
281	0	return 0;
282	0	}
283
284	0	EVP_MD_free(pectx->kdf_md);
285	0	pectx->kdf_md = EVP_MD_fetch(pectx->libctx, name, mdprops);
286	0	if (pectx->kdf_md == NULL)
287	0	return 0;
288	0	if (!ossl_digest_is_allowed(pectx->libctx, pectx->kdf_md)) {
289	0	EVP_MD_free(pectx->kdf_md);
290	0	pectx->kdf_md = NULL;
291	0	return 0;
292	0	}
293	0	}
294
295	0	p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_OUTLEN);
296	0	if (p != NULL) {
297	0	size_t outlen;
298
299	0	if (!OSSL_PARAM_get_size_t(p, &outlen))
300	0	return 0;
301	0	pectx->kdf_outlen = outlen;
302	0	}
303
304	0	p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_UKM);
305	0	if (p != NULL) {
306	0	void *tmp_ukm = NULL;
307	0	size_t tmp_ukmlen;
308
309	0	if (!OSSL_PARAM_get_octet_string(p, &tmp_ukm, 0, &tmp_ukmlen))
310	0	return 0;
311	0	OPENSSL_free(pectx->kdf_ukm);
312	0	pectx->kdf_ukm = tmp_ukm;
313	0	pectx->kdf_ukmlen = tmp_ukmlen;
314	0	}
315
316	0	return 1;
317	0	}
318
319		static const OSSL_PARAM known_settable_ctx_params[] = {
320		OSSL_PARAM_int(OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE, NULL),
321		OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_TYPE, NULL, 0),
322		OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST, NULL, 0),
323		OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST_PROPS, NULL, 0),
324		OSSL_PARAM_size_t(OSSL_EXCHANGE_PARAM_KDF_OUTLEN, NULL),
325		OSSL_PARAM_octet_string(OSSL_EXCHANGE_PARAM_KDF_UKM, NULL, 0),
326		OSSL_PARAM_END
327		};
328
329		static
330		const OSSL_PARAM ecdh_settable_ctx_params(ossl_unused void vpecdhctx,
331		ossl_unused void *provctx)
332	6	{
333	6	return known_settable_ctx_params;
334	6	}
335
336		static
337		int ecdh_get_ctx_params(void *vpecdhctx, OSSL_PARAM params[])
338	0	{
339	0	PROV_ECDH_CTX pectx = (PROV_ECDH_CTX )vpecdhctx;
340	0	OSSL_PARAM *p;
341
342	0	if (pectx == NULL)
343	0	return 0;
344
345	0	p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE);
346	0	if (p != NULL) {
347	0	int mode = pectx->cofactor_mode;
348
349	0	if (mode == -1) {
350		/* check what is the default for pecdhctx->k */
351	0	mode = EC_KEY_get_flags(pectx->k) & EC_FLAG_COFACTOR_ECDH ? 1 : 0;
352	0	}
353
354	0	if (!OSSL_PARAM_set_int(p, mode))
355	0	return 0;
356	0	}
357
358	0	p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_TYPE);
359	0	if (p != NULL) {
360	0	const char *kdf_type = NULL;
361
362	0	switch (pectx->kdf_type) {
363	0	case PROV_ECDH_KDF_NONE:
364	0	kdf_type = "";
365	0	break;
366	0	case PROV_ECDH_KDF_X9_63:
367	0	kdf_type = OSSL_KDF_NAME_X963KDF;
368	0	break;
369	0	default:
370	0	return 0;
371	0	}
372
373	0	if (!OSSL_PARAM_set_utf8_string(p, kdf_type))
374	0	return 0;
375	0	}
376
377	0	p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_DIGEST);
378	0	if (p != NULL
379	0	&& !OSSL_PARAM_set_utf8_string(p, pectx->kdf_md == NULL
380	0	? ""
381	0	: EVP_MD_get0_name(pectx->kdf_md))){
382	0	return 0;
383	0	}
384
385	0	p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_OUTLEN);
386	0	if (p != NULL && !OSSL_PARAM_set_size_t(p, pectx->kdf_outlen))
387	0	return 0;
388
389	0	p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_UKM);
390	0	if (p != NULL &&
391	0	!OSSL_PARAM_set_octet_ptr(p, pectx->kdf_ukm, pectx->kdf_ukmlen))
392	0	return 0;
393
394	0	return 1;
395	0	}
396
397		static const OSSL_PARAM known_gettable_ctx_params[] = {
398		OSSL_PARAM_int(OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE, NULL),
399		OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_TYPE, NULL, 0),
400		OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST, NULL, 0),
401		OSSL_PARAM_size_t(OSSL_EXCHANGE_PARAM_KDF_OUTLEN, NULL),
402		OSSL_PARAM_DEFN(OSSL_EXCHANGE_PARAM_KDF_UKM, OSSL_PARAM_OCTET_PTR,
403		NULL, 0),
404		OSSL_PARAM_END
405		};
406
407		static
408		const OSSL_PARAM ecdh_gettable_ctx_params(ossl_unused void vpecdhctx,
409		ossl_unused void *provctx)
410	0	{
411	0	return known_gettable_ctx_params;
412	0	}
413
414		static ossl_inline
415		size_t ecdh_size(const EC_KEY *k)
416	4.21k	{
417	4.21k	size_t degree = 0;
418	4.21k	const EC_GROUP *group;
419
420	4.21k	if (k == NULL
421	4.21k	\|\| (group = EC_KEY_get0_group(k)) == NULL)
422	0	return 0;
423
424	4.21k	degree = EC_GROUP_get_degree(group);
425
426	4.21k	return (degree + 7) / 8;
427	4.21k	}
428
429		static ossl_inline
430		int ecdh_plain_derive(void vpecdhctx, unsigned char secret,
431		size_t *psecretlen, size_t outlen)
432	3.09k	{
433	3.09k	PROV_ECDH_CTX pecdhctx = (PROV_ECDH_CTX )vpecdhctx;
434	3.09k	int retlen, ret = 0;
435	3.09k	size_t ecdhsize, size;
436	3.09k	const EC_POINT *ppubkey = NULL;
437	3.09k	EC_KEY *privk = NULL;
438	3.09k	const EC_GROUP *group;
439	3.09k	const BIGNUM *cofactor;
440	3.09k	int key_cofactor_mode;
441
442	3.09k	if (pecdhctx->k == NULL \|\| pecdhctx->peerk == NULL) {
443	0	ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);
444	0	return 0;
445	0	}
446
447	3.09k	ecdhsize = ecdh_size(pecdhctx->k);
448	3.09k	if (secret == NULL) {
449	1.54k	*psecretlen = ecdhsize;
450	1.54k	return 1;
451	1.54k	}
452
453	1.54k	if ((group = EC_KEY_get0_group(pecdhctx->k)) == NULL
454	1.54k	\|\| (cofactor = EC_GROUP_get0_cofactor(group)) == NULL )
455	0	return 0;
456
457		/*
458		* NB: unlike PKCS#3 DH, if outlen is less than maximum size this is not
459		* an error, the result is truncated.
460		*/
461	1.54k	size = outlen < ecdhsize ? outlen : ecdhsize;
462
463		/*
464		* The ctx->cofactor_mode flag has precedence over the
465		* cofactor_mode flag set on ctx->k.
466		*
467		* - if ctx->cofactor_mode == -1, use ctx->k directly
468		* - if ctx->cofactor_mode == key_cofactor_mode, use ctx->k directly
469		* - if ctx->cofactor_mode != key_cofactor_mode:
470		* - if ctx->k->cofactor == 1, the cofactor_mode flag is irrelevant, use
471		* ctx->k directly
472		* - if ctx->k->cofactor != 1, use a duplicate of ctx->k with the flag
473		* set to ctx->cofactor_mode
474		*/
475	1.54k	key_cofactor_mode =
476	1.54k	(EC_KEY_get_flags(pecdhctx->k) & EC_FLAG_COFACTOR_ECDH) ? 1 : 0;
477	1.54k	if (pecdhctx->cofactor_mode != -1
478	1.54k	&& pecdhctx->cofactor_mode != key_cofactor_mode
479	1.54k	&& !BN_is_one(cofactor)) {
480	0	if ((privk = EC_KEY_dup(pecdhctx->k)) == NULL)
481	0	return 0;
482
483	0	if (pecdhctx->cofactor_mode == 1)
484	0	EC_KEY_set_flags(privk, EC_FLAG_COFACTOR_ECDH);
485	0	else
486	0	EC_KEY_clear_flags(privk, EC_FLAG_COFACTOR_ECDH);
487	1.54k	} else {
488	1.54k	privk = pecdhctx->k;
489	1.54k	}
490
491	1.54k	ppubkey = EC_KEY_get0_public_key(pecdhctx->peerk);
492
493	1.54k	retlen = ECDH_compute_key(secret, size, ppubkey, privk, NULL);
494
495	1.54k	if (retlen <= 0)
496	0	goto end;
497
498	1.54k	*psecretlen = retlen;
499	1.54k	ret = 1;
500
501	1.54k	end:
502	1.54k	if (privk != pecdhctx->k)
503	0	EC_KEY_free(privk);
504	1.54k	return ret;
505	1.54k	}
506
507		static ossl_inline
508		int ecdh_X9_63_kdf_derive(void vpecdhctx, unsigned char secret,
509		size_t *psecretlen, size_t outlen)
510	0	{
511	0	PROV_ECDH_CTX pecdhctx = (PROV_ECDH_CTX )vpecdhctx;
512	0	unsigned char *stmp = NULL;
513	0	size_t stmplen;
514	0	int ret = 0;
515
516	0	if (secret == NULL) {
517	0	*psecretlen = pecdhctx->kdf_outlen;
518	0	return 1;
519	0	}
520
521	0	if (pecdhctx->kdf_outlen > outlen) {
522	0	ERR_raise(ERR_LIB_PROV, PROV_R_OUTPUT_BUFFER_TOO_SMALL);
523	0	return 0;
524	0	}
525	0	if (!ecdh_plain_derive(vpecdhctx, NULL, &stmplen, 0))
526	0	return 0;
527	0	if ((stmp = OPENSSL_secure_malloc(stmplen)) == NULL) {
528	0	ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
529	0	return 0;
530	0	}
531	0	if (!ecdh_plain_derive(vpecdhctx, stmp, &stmplen, stmplen))
532	0	goto err;
533
534		/* Do KDF stuff */
535	0	if (!ossl_ecdh_kdf_X9_63(secret, pecdhctx->kdf_outlen,
536	0	stmp, stmplen,
537	0	pecdhctx->kdf_ukm,
538	0	pecdhctx->kdf_ukmlen,
539	0	pecdhctx->kdf_md,
540	0	pecdhctx->libctx, NULL))
541	0	goto err;
542	0	*psecretlen = pecdhctx->kdf_outlen;
543	0	ret = 1;
544
545	0	err:
546	0	OPENSSL_secure_clear_free(stmp, stmplen);
547	0	return ret;
548	0	}
549
550		static
551		int ecdh_derive(void vpecdhctx, unsigned char secret,
552		size_t *psecretlen, size_t outlen)
553	4.21k	{
554	4.21k	PROV_ECDH_CTX pecdhctx = (PROV_ECDH_CTX )vpecdhctx;
555
556	4.21k	switch (pecdhctx->kdf_type) {
557	4.21k	case PROV_ECDH_KDF_NONE:
558	4.21k	return ecdh_plain_derive(vpecdhctx, secret, psecretlen, outlen);
559	0	case PROV_ECDH_KDF_X9_63:
560	0	return ecdh_X9_63_kdf_derive(vpecdhctx, secret, psecretlen, outlen);
561	0	default:
562	0	break;
563	4.21k	}
564	0	return 0;
565	4.21k	}
566
567		const OSSL_DISPATCH ossl_ecdh_keyexch_functions[] = {
568		{ OSSL_FUNC_KEYEXCH_NEWCTX, (void (*)(void))ecdh_newctx },
569		{ OSSL_FUNC_KEYEXCH_INIT, (void (*)(void))ecdh_init },
570		{ OSSL_FUNC_KEYEXCH_DERIVE, (void (*)(void))ecdh_derive },
571		{ OSSL_FUNC_KEYEXCH_SET_PEER, (void (*)(void))ecdh_set_peer },
572		{ OSSL_FUNC_KEYEXCH_FREECTX, (void (*)(void))ecdh_freectx },
573		{ OSSL_FUNC_KEYEXCH_DUPCTX, (void (*)(void))ecdh_dupctx },
574		{ OSSL_FUNC_KEYEXCH_SET_CTX_PARAMS, (void (*)(void))ecdh_set_ctx_params },
575		{ OSSL_FUNC_KEYEXCH_SETTABLE_CTX_PARAMS,
576		(void (*)(void))ecdh_settable_ctx_params },
577		{ OSSL_FUNC_KEYEXCH_GET_CTX_PARAMS, (void (*)(void))ecdh_get_ctx_params },
578		{ OSSL_FUNC_KEYEXCH_GETTABLE_CTX_PARAMS,
579		(void (*)(void))ecdh_gettable_ctx_params },
580		{ 0, NULL }
581		};