/*

 * 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

};