/*

 * Copyright 2019-2023 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

 */

/*

 * DH 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/core_dispatch.h>

#include <openssl/core_names.h>

#include <openssl/dh.h>

#include <openssl/err.h>

#include <openssl/proverr.h>

#include <openssl/params.h>

#include "prov/providercommon.h"

#include "prov/implementations.h"

#include "prov/provider_ctx.h"

#include "prov/securitycheck.h"

#include "crypto/dh.h"

static OSSL_FUNC_keyexch_newctx_fn dh_newctx;

static OSSL_FUNC_keyexch_init_fn dh_init;

static OSSL_FUNC_keyexch_set_peer_fn dh_set_peer;

static OSSL_FUNC_keyexch_derive_fn dh_derive;

static OSSL_FUNC_keyexch_freectx_fn dh_freectx;

static OSSL_FUNC_keyexch_dupctx_fn dh_dupctx;

static OSSL_FUNC_keyexch_set_ctx_params_fn dh_set_ctx_params;

static OSSL_FUNC_keyexch_settable_ctx_params_fn dh_settable_ctx_params;

static OSSL_FUNC_keyexch_get_ctx_params_fn dh_get_ctx_params;

static OSSL_FUNC_keyexch_gettable_ctx_params_fn dh_gettable_ctx_params;

/*

 * This type is only really used to handle some legacy related functionality.

 * If you need to use other KDF's (such as SSKDF) just use PROV_DH_KDF_NONE

 * here and then create and run a KDF after the key is derived.

 * Note that X942 has 2 variants of key derivation:

 *   (1) DH_KDF_X9_42_ASN1 - which contains an ANS1 encoded object that has

 *   the counter embedded in it.

 *   (2) DH_KDF_X941_CONCAT - which is the same as ECDH_X963_KDF (which can be

 *       done by creating a "X963KDF".

 */

enum kdf_type {

    PROV_DH_KDF_NONE = 0,

    PROV_DH_KDF_X9_42_ASN1

};

/*

 * What's passed as an actual key is defined by the KEYMGMT interface.

 * We happen to know that our KEYMGMT simply passes DH structures, so

 * we use that here too.

 */

typedef struct {

    OSSL_LIB_CTX *libctx;

    DH *dh;

    DH *dhpeer;

    unsigned int pad : 1;

    /* DH KDF */

    /* KDF (if any) to use for DH */

    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;

    char *kdf_cekalg;

} PROV_DH_CTX;

static void *dh_newctx(void *provctx)

{

    PROV_DH_CTX *pdhctx;

    if (!ossl_prov_is_running())

        return NULL;

    pdhctx = OPENSSL_zalloc(sizeof(PROV_DH_CTX));

    if (pdhctx == NULL)

        return NULL;

    pdhctx->libctx = PROV_LIBCTX_OF(provctx);

    pdhctx->kdf_type = PROV_DH_KDF_NONE;

    return pdhctx;

}

static int dh_init(void *vpdhctx, void *vdh, const OSSL_PARAM params[])

{

    PROV_DH_CTX *pdhctx = (PROV_DH_CTX *)vpdhctx;

    if (!ossl_prov_is_running()

            || pdhctx == NULL

            || vdh == NULL

            || !DH_up_ref(vdh))

        return 0;

    DH_free(pdhctx->dh);

    pdhctx->dh = vdh;

    pdhctx->kdf_type = PROV_DH_KDF_NONE;

    return dh_set_ctx_params(pdhctx, params)

           && ossl_dh_check_key(pdhctx->libctx, vdh);

}

/* The 2 parties must share the same domain parameters */

static int dh_match_params(DH *priv, DH *peer)

{

    int ret;

    FFC_PARAMS *dhparams_priv = ossl_dh_get0_params(priv);

    FFC_PARAMS *dhparams_peer = ossl_dh_get0_params(peer);

    ret = dhparams_priv != NULL

          && dhparams_peer != NULL

          && ossl_ffc_params_cmp(dhparams_priv, dhparams_peer, 1);

    if (!ret)

        ERR_raise(ERR_LIB_PROV, PROV_R_MISMATCHING_DOMAIN_PARAMETERS);

    return ret;

}

static int dh_set_peer(void *vpdhctx, void *vdh)

{

    PROV_DH_CTX *pdhctx = (PROV_DH_CTX *)vpdhctx;

    if (!ossl_prov_is_running()

            || pdhctx == NULL

            || vdh == NULL

            || !dh_match_params(vdh, pdhctx->dh)

            || !DH_up_ref(vdh))

        return 0;

    DH_free(pdhctx->dhpeer);

    pdhctx->dhpeer = vdh;

    return 1;

}

static int dh_plain_derive(void *vpdhctx,

                           unsigned char *secret, size_t *secretlen,

                           size_t outlen, unsigned int pad)

{

    PROV_DH_CTX *pdhctx = (PROV_DH_CTX *)vpdhctx;

    int ret;

    size_t dhsize;

    const BIGNUM *pub_key = NULL;

    if (pdhctx->dh == NULL || pdhctx->dhpeer == NULL) {

        ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);

        return 0;

    }

    dhsize = (size_t)DH_size(pdhctx->dh);

    if (secret == NULL) {

        *secretlen = dhsize;

        return 1;

    }

    if (outlen < dhsize) {

        ERR_raise(ERR_LIB_PROV, PROV_R_OUTPUT_BUFFER_TOO_SMALL);

        return 0;

    }

    DH_get0_key(pdhctx->dhpeer, &pub_key, NULL);

    if (pad)

        ret = DH_compute_key_padded(secret, pub_key, pdhctx->dh);

    else

        ret = DH_compute_key(secret, pub_key, pdhctx->dh);

    if (ret <= 0)

        return 0;

    *secretlen = ret;

    return 1;

}

static int dh_X9_42_kdf_derive(void *vpdhctx, unsigned char *secret,

                               size_t *secretlen, size_t outlen)

{

    PROV_DH_CTX *pdhctx = (PROV_DH_CTX *)vpdhctx;

    unsigned char *stmp = NULL;

    size_t stmplen;

    int ret = 0;

    if (secret == NULL) {

        *secretlen = pdhctx->kdf_outlen;

        return 1;

    }

    if (pdhctx->kdf_outlen > outlen) {

        ERR_raise(ERR_LIB_PROV, PROV_R_OUTPUT_BUFFER_TOO_SMALL);

        return 0;

    }

    if (!dh_plain_derive(pdhctx, NULL, &stmplen, 0, 1))

        return 0;

    if ((stmp = OPENSSL_secure_malloc(stmplen)) == NULL)

        return 0;

    if (!dh_plain_derive(pdhctx, stmp, &stmplen, stmplen, 1))

        goto err;

    /* Do KDF stuff */

    if (pdhctx->kdf_type == PROV_DH_KDF_X9_42_ASN1) {

        if (!ossl_dh_kdf_X9_42_asn1(secret, pdhctx->kdf_outlen,

                                    stmp, stmplen,

                                    pdhctx->kdf_cekalg,

                                    pdhctx->kdf_ukm,

                                    pdhctx->kdf_ukmlen,

                                    pdhctx->kdf_md,

                                    pdhctx->libctx, NULL))

            goto err;

    }

    *secretlen = pdhctx->kdf_outlen;

    ret = 1;

err:

    OPENSSL_secure_clear_free(stmp, stmplen);

    return ret;

}

static int dh_derive(void *vpdhctx, unsigned char *secret,

                     size_t *psecretlen, size_t outlen)

{

    PROV_DH_CTX *pdhctx = (PROV_DH_CTX *)vpdhctx;

    if (!ossl_prov_is_running())

        return 0;

    switch (pdhctx->kdf_type) {

        case PROV_DH_KDF_NONE:

            return dh_plain_derive(pdhctx, secret, psecretlen, outlen,

                                   pdhctx->pad);

        case PROV_DH_KDF_X9_42_ASN1:

            return dh_X9_42_kdf_derive(pdhctx, secret, psecretlen, outlen);

        default:

            break;

    }

    return 0;

}

static void dh_freectx(void *vpdhctx)

{

    PROV_DH_CTX *pdhctx = (PROV_DH_CTX *)vpdhctx;

    OPENSSL_free(pdhctx->kdf_cekalg);

    DH_free(pdhctx->dh);

    DH_free(pdhctx->dhpeer);

    EVP_MD_free(pdhctx->kdf_md);

    OPENSSL_clear_free(pdhctx->kdf_ukm, pdhctx->kdf_ukmlen);

    OPENSSL_free(pdhctx);

}

static void *dh_dupctx(void *vpdhctx)

{

    PROV_DH_CTX *srcctx = (PROV_DH_CTX *)vpdhctx;

    PROV_DH_CTX *dstctx;

    if (!ossl_prov_is_running())

        return NULL;

    dstctx = OPENSSL_zalloc(sizeof(*srcctx));

    if (dstctx == NULL)

        return NULL;

    *dstctx = *srcctx;

    dstctx->dh = NULL;

    dstctx->dhpeer = NULL;

    dstctx->kdf_md = NULL;

    dstctx->kdf_ukm = NULL;

    dstctx->kdf_cekalg = NULL;

    if (srcctx->dh != NULL && !DH_up_ref(srcctx->dh))

        goto err;

    else

        dstctx->dh = srcctx->dh;

    if (srcctx->dhpeer != NULL && !DH_up_ref(srcctx->dhpeer))

        goto err;

    else

        dstctx->dhpeer = srcctx->dhpeer;

    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;

    }

    if (srcctx->kdf_cekalg != NULL) {

        dstctx->kdf_cekalg = OPENSSL_strdup(srcctx->kdf_cekalg);

        if (dstctx->kdf_cekalg == NULL)

            goto err;

    }

    return dstctx;

err:

    dh_freectx(dstctx);

    return NULL;

}

static int dh_set_ctx_params(void *vpdhctx, const OSSL_PARAM params[])

{

    PROV_DH_CTX *pdhctx = (PROV_DH_CTX *)vpdhctx;

    const OSSL_PARAM *p;

    unsigned int pad;

    char name[80] = { '\0' }; /* should be big enough */

    char *str = NULL;

    if (pdhctx == NULL)

        return 0;

    if (params == NULL)

        return 1;

    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')

            pdhctx->kdf_type = PROV_DH_KDF_NONE;

        else if (strcmp(name, OSSL_KDF_NAME_X942KDF_ASN1) == 0)

            pdhctx->kdf_type = PROV_DH_KDF_X9_42_ASN1;

        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(pdhctx->kdf_md);

        pdhctx->kdf_md = EVP_MD_fetch(pdhctx->libctx, name, mdprops);

        if (pdhctx->kdf_md == NULL)

            return 0;

        if (!ossl_digest_is_allowed(pdhctx->libctx, pdhctx->kdf_md)) {

            EVP_MD_free(pdhctx->kdf_md);

            pdhctx->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;

        pdhctx->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;

        OPENSSL_free(pdhctx->kdf_ukm);

        pdhctx->kdf_ukm = NULL;

        pdhctx->kdf_ukmlen = 0;

        /* ukm is an optional field so it can be NULL */

        if (p->data != NULL && p->data_size != 0) {

            if (!OSSL_PARAM_get_octet_string(p, &tmp_ukm, 0, &tmp_ukmlen))

                return 0;

            pdhctx->kdf_ukm = tmp_ukm;

            pdhctx->kdf_ukmlen = tmp_ukmlen;

        }

    }

    p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_PAD);

    if (p != NULL) {

        if (!OSSL_PARAM_get_uint(p, &pad))

            return 0;

        pdhctx->pad = pad ? 1 : 0;

    }

    p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_CEK_ALG);

    if (p != NULL) {

        str = name;

        OPENSSL_free(pdhctx->kdf_cekalg);

        pdhctx->kdf_cekalg = NULL;

        if (p->data != NULL && p->data_size != 0) {

            if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(name)))

                return 0;

            pdhctx->kdf_cekalg = OPENSSL_strdup(name);

            if (pdhctx->kdf_cekalg == NULL)

                return 0;

        }

    }

    return 1;

}

static const OSSL_PARAM known_settable_ctx_params[] = {

    OSSL_PARAM_int(OSSL_EXCHANGE_PARAM_PAD, 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_utf8_string(OSSL_KDF_PARAM_CEK_ALG, NULL, 0),

    OSSL_PARAM_END

};

static const OSSL_PARAM *dh_settable_ctx_params(ossl_unused void *vpdhctx,

                                                ossl_unused void *provctx)

{

    return known_settable_ctx_params;

}

static const OSSL_PARAM known_gettable_ctx_params[] = {

    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_utf8_string(OSSL_KDF_PARAM_CEK_ALG, NULL, 0),

    OSSL_PARAM_END

};

static const OSSL_PARAM *dh_gettable_ctx_params(ossl_unused void *vpdhctx,

                                                ossl_unused void *provctx)

{

    return known_gettable_ctx_params;

}

static int dh_get_ctx_params(void *vpdhctx, OSSL_PARAM params[])

{

    PROV_DH_CTX *pdhctx = (PROV_DH_CTX *)vpdhctx;

    OSSL_PARAM *p;

    if (pdhctx == NULL)

        return 0;

    p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_TYPE);

    if (p != NULL) {

        const char *kdf_type = NULL;

        switch (pdhctx->kdf_type) {

            case PROV_DH_KDF_NONE:

                kdf_type = "";

                break;

            case PROV_DH_KDF_X9_42_ASN1:

                kdf_type = OSSL_KDF_NAME_X942KDF_ASN1;

                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, pdhctx->kdf_md == NULL

                                           ? ""

                                           : EVP_MD_get0_name(pdhctx->kdf_md))) {

        return 0;

    }

    p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_OUTLEN);

    if (p != NULL && !OSSL_PARAM_set_size_t(p, pdhctx->kdf_outlen))

        return 0;

    p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_UKM);

    if (p != NULL

        && !OSSL_PARAM_set_octet_ptr(p, pdhctx->kdf_ukm, pdhctx->kdf_ukmlen))

        return 0;

    p = OSSL_PARAM_locate(params, OSSL_KDF_PARAM_CEK_ALG);

    if (p != NULL

            && !OSSL_PARAM_set_utf8_string(p, pdhctx->kdf_cekalg == NULL

                                           ? "" :  pdhctx->kdf_cekalg))

        return 0;

    return 1;

}

const OSSL_DISPATCH ossl_dh_keyexch_functions[] = {

    { OSSL_FUNC_KEYEXCH_NEWCTX, (void (*)(void))dh_newctx },

    { OSSL_FUNC_KEYEXCH_INIT, (void (*)(void))dh_init },

    { OSSL_FUNC_KEYEXCH_DERIVE, (void (*)(void))dh_derive },

    { OSSL_FUNC_KEYEXCH_SET_PEER, (void (*)(void))dh_set_peer },

    { OSSL_FUNC_KEYEXCH_FREECTX, (void (*)(void))dh_freectx },

    { OSSL_FUNC_KEYEXCH_DUPCTX, (void (*)(void))dh_dupctx },

    { OSSL_FUNC_KEYEXCH_SET_CTX_PARAMS, (void (*)(void))dh_set_ctx_params },

    { OSSL_FUNC_KEYEXCH_SETTABLE_CTX_PARAMS,

      (void (*)(void))dh_settable_ctx_params },

    { OSSL_FUNC_KEYEXCH_GET_CTX_PARAMS, (void (*)(void))dh_get_ctx_params },

    { OSSL_FUNC_KEYEXCH_GETTABLE_CTX_PARAMS,

      (void (*)(void))dh_gettable_ctx_params },

    OSSL_DISPATCH_END

};