openssl/crypto/ec/ec_ameth.c

/*
 * Copyright 2006-2019 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the OpenSSL license (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
 */

#include <stdio.h>
#include "internal/cryptlib.h"
#include <openssl/x509.h>
#include <openssl/ec.h>
#include <openssl/bn.h>
#include <openssl/cms.h>
#include <openssl/asn1t.h>
#include "crypto/asn1.h"
#include "crypto/evp.h"
#include "ec_lcl.h"

#ifndef OPENSSL_NO_CMS
static int ecdh_cms_decrypt(CMS_RecipientInfo *ri);
static int ecdh_cms_encrypt(CMS_RecipientInfo *ri);
#endif

static int eckey_param2type(int *pptype, void **ppval, EC_KEY *ec_key)
{
    const EC_GROUP *group;
    int nid;
    if (ec_key == NULL || (group = EC_KEY_get0_group(ec_key)) == NULL) {
        ECerr(EC_F_ECKEY_PARAM2TYPE, EC_R_MISSING_PARAMETERS);
        return 0;
    }
    if (EC_GROUP_get_asn1_flag(group)
        && (nid = EC_GROUP_get_curve_name(group)))
        /* we have a 'named curve' => just set the OID */
    {
        *ppval = OBJ_nid2obj(nid);
        *pptype = V_ASN1_OBJECT;
    } else {                    /* explicit parameters */

        ASN1_STRING *pstr = NULL;
        pstr = ASN1_STRING_new();
        if (pstr == NULL)
            return 0;
        pstr->length = i2d_ECParameters(ec_key, &pstr->data);
        if (pstr->length <= 0) {
            ASN1_STRING_free(pstr);
            ECerr(EC_F_ECKEY_PARAM2TYPE, ERR_R_EC_LIB);
            return 0;
        }
        *ppval = pstr;
        *pptype = V_ASN1_SEQUENCE;
    }
    return 1;
}

static int eckey_pub_encode(X509_PUBKEY *pk, const EVP_PKEY *pkey)
{
    EC_KEY *ec_key = pkey->pkey.ec;
    void *pval = NULL;
    int ptype;
    unsigned char *penc = NULL, *p;
    int penclen;

    if (!eckey_param2type(&ptype, &pval, ec_key)) {
        ECerr(EC_F_ECKEY_PUB_ENCODE, ERR_R_EC_LIB);
        return 0;
    }
    penclen = i2o_ECPublicKey(ec_key, NULL);
    if (penclen <= 0)
        goto err;
    penc = OPENSSL_malloc(penclen);
    if (penc == NULL)
        goto err;
    p = penc;
    penclen = i2o_ECPublicKey(ec_key, &p);
    if (penclen <= 0)
        goto err;
    if (X509_PUBKEY_set0_param(pk, OBJ_nid2obj(EVP_PKEY_EC),
                               ptype, pval, penc, penclen))
        return 1;
 err:
    if (ptype == V_ASN1_OBJECT)
        ASN1_OBJECT_free(pval);
    else
        ASN1_STRING_free(pval);
    OPENSSL_free(penc);
    return 0;
}

static EC_KEY *eckey_type2param(int ptype, const void *pval)
{
    EC_KEY *eckey = NULL;
    EC_GROUP *group = NULL;

    if (ptype == V_ASN1_SEQUENCE) {
        const ASN1_STRING *pstr = pval;
        const unsigned char *pm = pstr->data;
        int pmlen = pstr->length;

        if ((eckey = d2i_ECParameters(NULL, &pm, pmlen)) == NULL) {
            ECerr(EC_F_ECKEY_TYPE2PARAM, EC_R_DECODE_ERROR);
            goto ecerr;
        }
    } else if (ptype == V_ASN1_OBJECT) {
        const ASN1_OBJECT *poid = pval;

        /*
         * type == V_ASN1_OBJECT => the parameters are given by an asn1 OID
         */
        if ((eckey = EC_KEY_new()) == NULL) {
            ECerr(EC_F_ECKEY_TYPE2PARAM, ERR_R_MALLOC_FAILURE);
            goto ecerr;
        }
        group = EC_GROUP_new_by_curve_name(OBJ_obj2nid(poid));
        if (group == NULL)
            goto ecerr;
        EC_GROUP_set_asn1_flag(group, OPENSSL_EC_NAMED_CURVE);
        if (EC_KEY_set_group(eckey, group) == 0)
            goto ecerr;
        EC_GROUP_free(group);
    } else {
        ECerr(EC_F_ECKEY_TYPE2PARAM, EC_R_DECODE_ERROR);
        goto ecerr;
    }

    return eckey;

 ecerr:
    EC_KEY_free(eckey);
    EC_GROUP_free(group);
    return NULL;
}

static int eckey_pub_decode(EVP_PKEY *pkey, X509_PUBKEY *pubkey)
{
    const unsigned char *p = NULL;
    const void *pval;
    int ptype, pklen;
    EC_KEY *eckey = NULL;
    X509_ALGOR *palg;

    if (!X509_PUBKEY_get0_param(NULL, &p, &pklen, &palg, pubkey))
        return 0;
    X509_ALGOR_get0(NULL, &ptype, &pval, palg);

    eckey = eckey_type2param(ptype, pval);

    if (!eckey) {
        ECerr(EC_F_ECKEY_PUB_DECODE, ERR_R_EC_LIB);
        return 0;
    }

    /* We have parameters now set public key */
    if (!o2i_ECPublicKey(&eckey, &p, pklen)) {
        ECerr(EC_F_ECKEY_PUB_DECODE, EC_R_DECODE_ERROR);
        goto ecerr;
    }

    EVP_PKEY_assign_EC_KEY(pkey, eckey);
    return 1;

 ecerr:
    EC_KEY_free(eckey);
    return 0;
}

static int eckey_pub_cmp(const EVP_PKEY *a, const EVP_PKEY *b)
{
    int r;
    const EC_GROUP *group = EC_KEY_get0_group(b->pkey.ec);
    const EC_POINT *pa = EC_KEY_get0_public_key(a->pkey.ec),
        *pb = EC_KEY_get0_public_key(b->pkey.ec);
    if (group == NULL || pa == NULL || pb == NULL)
        return -2;
    r = EC_POINT_cmp(group, pa, pb, NULL);
    if (r == 0)
        return 1;
    if (r == 1)
        return 0;
    return -2;
}

static int eckey_priv_decode(EVP_PKEY *pkey, const PKCS8_PRIV_KEY_INFO *p8)
{
    const unsigned char *p = NULL;
    const void *pval;
    int ptype, pklen;
    EC_KEY *eckey = NULL;
    const X509_ALGOR *palg;

    if (!PKCS8_pkey_get0(NULL, &p, &pklen, &palg, p8))
        return 0;
    X509_ALGOR_get0(NULL, &ptype, &pval, palg);

    eckey = eckey_type2param(ptype, pval);

    if (!eckey)
        goto ecliberr;

    /* We have parameters now set private key */
    if (!d2i_ECPrivateKey(&eckey, &p, pklen)) {
        ECerr(EC_F_ECKEY_PRIV_DECODE, EC_R_DECODE_ERROR);
        goto ecerr;
    }

    EVP_PKEY_assign_EC_KEY(pkey, eckey);
    return 1;

 ecliberr:
    ECerr(EC_F_ECKEY_PRIV_DECODE, ERR_R_EC_LIB);
 ecerr:
    EC_KEY_free(eckey);
    return 0;
}

static int eckey_priv_encode(PKCS8_PRIV_KEY_INFO *p8, const EVP_PKEY *pkey)
{
    EC_KEY ec_key = *(pkey->pkey.ec);
    unsigned char *ep, *p;
    int eplen, ptype;
    void *pval;
    unsigned int old_flags;

    if (!eckey_param2type(&ptype, &pval, &ec_key)) {
        ECerr(EC_F_ECKEY_PRIV_ENCODE, EC_R_DECODE_ERROR);
        return 0;
    }

    /* set the private key */

    /*
     * do not include the parameters in the SEC1 private key see PKCS#11
     * 12.11
     */
    old_flags = EC_KEY_get_enc_flags(&ec_key);
    EC_KEY_set_enc_flags(&ec_key, old_flags | EC_PKEY_NO_PARAMETERS);

    eplen = i2d_ECPrivateKey(&ec_key, NULL);
    if (!eplen) {
        ECerr(EC_F_ECKEY_PRIV_ENCODE, ERR_R_EC_LIB);
        return 0;
    }
    ep = OPENSSL_malloc(eplen);
    if (ep == NULL) {
        ECerr(EC_F_ECKEY_PRIV_ENCODE, ERR_R_MALLOC_FAILURE);
        return 0;
    }
    p = ep;
    if (!i2d_ECPrivateKey(&ec_key, &p)) {
        OPENSSL_free(ep);
        ECerr(EC_F_ECKEY_PRIV_ENCODE, ERR_R_EC_LIB);
        return 0;
    }

    if (!PKCS8_pkey_set0(p8, OBJ_nid2obj(NID_X9_62_id_ecPublicKey), 0,
                         ptype, pval, ep, eplen)) {
        OPENSSL_free(ep);
        return 0;
    }

    return 1;
}

static int int_ec_size(const EVP_PKEY *pkey)
{
    return ECDSA_size(pkey->pkey.ec);
}

static int ec_bits(const EVP_PKEY *pkey)
{
    return EC_GROUP_order_bits(EC_KEY_get0_group(pkey->pkey.ec));
}

static int ec_security_bits(const EVP_PKEY *pkey)
{
    int ecbits = ec_bits(pkey);
    if (ecbits >= 512)
        return 256;
    if (ecbits >= 384)
        return 192;
    if (ecbits >= 256)
        return 128;
    if (ecbits >= 224)
        return 112;
    if (ecbits >= 160)
        return 80;
    return ecbits / 2;
}

static int ec_missing_parameters(const EVP_PKEY *pkey)
{
    if (pkey->pkey.ec == NULL || EC_KEY_get0_group(pkey->pkey.ec) == NULL)
        return 1;
    return 0;
}

static int ec_copy_parameters(EVP_PKEY *to, const EVP_PKEY *from)
{
    EC_GROUP *group = EC_GROUP_dup(EC_KEY_get0_group(from->pkey.ec));

    if (group == NULL)
        return 0;
    if (to->pkey.ec == NULL) {
        to->pkey.ec = EC_KEY_new();
        if (to->pkey.ec == NULL)
            goto err;
    }
    if (EC_KEY_set_group(to->pkey.ec, group) == 0)
        goto err;
    EC_GROUP_free(group);
    return 1;
 err:
    EC_GROUP_free(group);
    return 0;
}

static int ec_cmp_parameters(const EVP_PKEY *a, const EVP_PKEY *b)
{
    const EC_GROUP *group_a = EC_KEY_get0_group(a->pkey.ec),
        *group_b = EC_KEY_get0_group(b->pkey.ec);
    if (group_a == NULL || group_b == NULL)
        return -2;
    if (EC_GROUP_cmp(group_a, group_b, NULL))
        return 0;
    else
        return 1;
}

static void int_ec_free(EVP_PKEY *pkey)
{
    EC_KEY_free(pkey->pkey.ec);
}

typedef enum {
    EC_KEY_PRINT_PRIVATE,
    EC_KEY_PRINT_PUBLIC,
    EC_KEY_PRINT_PARAM
} ec_print_t;

static int do_EC_KEY_print(BIO *bp, const EC_KEY *x, int off, ec_print_t ktype)
{
    const char *ecstr;
    unsigned char *priv = NULL, *pub = NULL;
    size_t privlen = 0, publen = 0;
    int ret = 0;
    const EC_GROUP *group;

    if (x == NULL || (group = EC_KEY_get0_group(x)) == NULL) {
        ECerr(EC_F_DO_EC_KEY_PRINT, ERR_R_PASSED_NULL_PARAMETER);
        return 0;
    }

    if (ktype != EC_KEY_PRINT_PARAM && EC_KEY_get0_public_key(x) != NULL) {
        publen = EC_KEY_key2buf(x, EC_KEY_get_conv_form(x), &pub, NULL);
        if (publen == 0)
            goto err;
    }

    if (ktype == EC_KEY_PRINT_PRIVATE && EC_KEY_get0_private_key(x) != NULL) {
        privlen = EC_KEY_priv2buf(x, &priv);
        if (privlen == 0)
            goto err;
    }

    if (ktype == EC_KEY_PRINT_PRIVATE)
        ecstr = "Private-Key";
    else if (ktype == EC_KEY_PRINT_PUBLIC)
        ecstr = "Public-Key";
    else
        ecstr = "ECDSA-Parameters";

    if (!BIO_indent(bp, off, 128))
        goto err;
    if (BIO_printf(bp, "%s: (%d bit)\n", ecstr,
                   EC_GROUP_order_bits(group)) <= 0)
        goto err;

    if (privlen != 0) {
        if (BIO_printf(bp, "%*spriv:\n", off, "") <= 0)
            goto err;
        if (ASN1_buf_print(bp, priv, privlen, off + 4) == 0)
            goto err;
    }

    if (publen != 0) {
        if (BIO_printf(bp, "%*spub:\n", off, "") <= 0)
            goto err;
        if (ASN1_buf_print(bp, pub, publen, off + 4) == 0)
            goto err;
    }

    if (!ECPKParameters_print(bp, group, off))
        goto err;
    ret = 1;
 err:
    if (!ret)
        ECerr(EC_F_DO_EC_KEY_PRINT, ERR_R_EC_LIB);
    OPENSSL_clear_free(priv, privlen);
    OPENSSL_free(pub);
    return ret;
}

static int eckey_param_decode(EVP_PKEY *pkey,
                              const unsigned char **pder, int derlen)
{
    EC_KEY *eckey;

    if ((eckey = d2i_ECParameters(NULL, pder, derlen)) == NULL) {
        ECerr(EC_F_ECKEY_PARAM_DECODE, ERR_R_EC_LIB);
        return 0;
    }
    EVP_PKEY_assign_EC_KEY(pkey, eckey);
    return 1;
}

static int eckey_param_encode(const EVP_PKEY *pkey, unsigned char **pder)
{
    return i2d_ECParameters(pkey->pkey.ec, pder);
}

static int eckey_param_print(BIO *bp, const EVP_PKEY *pkey, int indent,
                             ASN1_PCTX *ctx)
{
    return do_EC_KEY_print(bp, pkey->pkey.ec, indent, EC_KEY_PRINT_PARAM);
}

static int eckey_pub_print(BIO *bp, const EVP_PKEY *pkey, int indent,
                           ASN1_PCTX *ctx)
{
    return do_EC_KEY_print(bp, pkey->pkey.ec, indent, EC_KEY_PRINT_PUBLIC);
}

static int eckey_priv_print(BIO *bp, const EVP_PKEY *pkey, int indent,
                            ASN1_PCTX *ctx)
{
    return do_EC_KEY_print(bp, pkey->pkey.ec, indent, EC_KEY_PRINT_PRIVATE);
}

static int old_ec_priv_decode(EVP_PKEY *pkey,
                              const unsigned char **pder, int derlen)
{
    EC_KEY *ec;

    if ((ec = d2i_ECPrivateKey(NULL, pder, derlen)) == NULL) {
        ECerr(EC_F_OLD_EC_PRIV_DECODE, EC_R_DECODE_ERROR);
        return 0;
    }
    EVP_PKEY_assign_EC_KEY(pkey, ec);
    return 1;
}

static int old_ec_priv_encode(const EVP_PKEY *pkey, unsigned char **pder)
{
    return i2d_ECPrivateKey(pkey->pkey.ec, pder);
}

static int ec_pkey_ctrl(EVP_PKEY *pkey, int op, long arg1, void *arg2)
{
    switch (op) {
    case ASN1_PKEY_CTRL_PKCS7_SIGN:
        if (arg1 == 0) {
            int snid, hnid;
            X509_ALGOR *alg1, *alg2;
            PKCS7_SIGNER_INFO_get0_algs(arg2, NULL, &alg1, &alg2);
            if (alg1 == NULL || alg1->algorithm == NULL)
                return -1;
            hnid = OBJ_obj2nid(alg1->algorithm);
            if (hnid == NID_undef)
                return -1;
            if (!OBJ_find_sigid_by_algs(&snid, hnid, EVP_PKEY_id(pkey)))
                return -1;
            X509_ALGOR_set0(alg2, OBJ_nid2obj(snid), V_ASN1_UNDEF, 0);
        }
        return 1;
#ifndef OPENSSL_NO_CMS
    case ASN1_PKEY_CTRL_CMS_SIGN:
        if (arg1 == 0) {
            int snid, hnid;
            X509_ALGOR *alg1, *alg2;
            CMS_SignerInfo_get0_algs(arg2, NULL, NULL, &alg1, &alg2);
            if (alg1 == NULL || alg1->algorithm == NULL)
                return -1;
            hnid = OBJ_obj2nid(alg1->algorithm);
            if (hnid == NID_undef)
                return -1;
            if (!OBJ_find_sigid_by_algs(&snid, hnid, EVP_PKEY_id(pkey)))
                return -1;
            X509_ALGOR_set0(alg2, OBJ_nid2obj(snid), V_ASN1_UNDEF, 0);
        }
        return 1;

    case ASN1_PKEY_CTRL_CMS_ENVELOPE:
        if (arg1 == 1)
            return ecdh_cms_decrypt(arg2);
        else if (arg1 == 0)
            return ecdh_cms_encrypt(arg2);
        return -2;

    case ASN1_PKEY_CTRL_CMS_RI_TYPE:
        *(int *)arg2 = CMS_RECIPINFO_AGREE;
        return 1;
#endif

    case ASN1_PKEY_CTRL_DEFAULT_MD_NID:
        if (EVP_PKEY_id(pkey) == EVP_PKEY_SM2) {
            /* For SM2, the only valid digest-alg is SM3 */
            *(int *)arg2 = NID_sm3;
        } else {
            *(int *)arg2 = NID_sha256;
        }
        return 1;

    case ASN1_PKEY_CTRL_SET1_TLS_ENCPT:
        return EC_KEY_oct2key(EVP_PKEY_get0_EC_KEY(pkey), arg2, arg1, NULL);

    case ASN1_PKEY_CTRL_GET1_TLS_ENCPT:
        return EC_KEY_key2buf(EVP_PKEY_get0_EC_KEY(pkey),
                              POINT_CONVERSION_UNCOMPRESSED, arg2, NULL);

    default:
        return -2;

    }

}

static int ec_pkey_check(const EVP_PKEY *pkey)
{
    EC_KEY *eckey = pkey->pkey.ec;

    /* stay consistent to what EVP_PKEY_check demands */
    if (eckey->priv_key == NULL) {
        ECerr(EC_F_EC_PKEY_CHECK, EC_R_MISSING_PRIVATE_KEY);
        return 0;
    }

    return EC_KEY_check_key(eckey);
}

static int ec_pkey_public_check(const EVP_PKEY *pkey)
{
    EC_KEY *eckey = pkey->pkey.ec;

    /*
     * Note: it unnecessary to check eckey->pub_key here since
     * it will be checked in EC_KEY_check_key(). In fact, the
     * EC_KEY_check_key() mainly checks the public key, and checks
     * the private key optionally (only if there is one). So if
     * someone passes a whole EC key (public + private), this
     * will also work...
     */

    return EC_KEY_check_key(eckey);
}

static int ec_pkey_param_check(const EVP_PKEY *pkey)
{
    EC_KEY *eckey = pkey->pkey.ec;

    /* stay consistent to what EVP_PKEY_check demands */
    if (eckey->group == NULL) {
        ECerr(EC_F_EC_PKEY_PARAM_CHECK, EC_R_MISSING_PARAMETERS);
        return 0;
    }

    return EC_GROUP_check(eckey->group, NULL);
}

const EVP_PKEY_ASN1_METHOD eckey_asn1_meth = {
    EVP_PKEY_EC,
    EVP_PKEY_EC,
    0,
    "EC",
    "OpenSSL EC algorithm",

    eckey_pub_decode,
    eckey_pub_encode,
    eckey_pub_cmp,
    eckey_pub_print,

    eckey_priv_decode,
    eckey_priv_encode,
    eckey_priv_print,

    int_ec_size,
    ec_bits,
    ec_security_bits,

    eckey_param_decode,
    eckey_param_encode,
    ec_missing_parameters,
    ec_copy_parameters,
    ec_cmp_parameters,
    eckey_param_print,
    0,

    int_ec_free,
    ec_pkey_ctrl,
    old_ec_priv_decode,
    old_ec_priv_encode,

    0, 0, 0,

    ec_pkey_check,
    ec_pkey_public_check,
    ec_pkey_param_check
};

#if !defined(OPENSSL_NO_SM2)
const EVP_PKEY_ASN1_METHOD sm2_asn1_meth = {
   EVP_PKEY_SM2,
   EVP_PKEY_EC,
   ASN1_PKEY_ALIAS
};
#endif

int EC_KEY_print(BIO *bp, const EC_KEY *x, int off)
{
    int private = EC_KEY_get0_private_key(x) != NULL;

    return do_EC_KEY_print(bp, x, off,
                private ? EC_KEY_PRINT_PRIVATE : EC_KEY_PRINT_PUBLIC);
}

int ECParameters_print(BIO *bp, const EC_KEY *x)
{
    return do_EC_KEY_print(bp, x, 4, EC_KEY_PRINT_PARAM);
}

#ifndef OPENSSL_NO_CMS

static int ecdh_cms_set_peerkey(EVP_PKEY_CTX *pctx,
                                X509_ALGOR *alg, ASN1_BIT_STRING *pubkey)
{
    const ASN1_OBJECT *aoid;
    int atype;
    const void *aval;
    int rv = 0;
    EVP_PKEY *pkpeer = NULL;
    EC_KEY *ecpeer = NULL;
    const unsigned char *p;
    int plen;
    X509_ALGOR_get0(&aoid, &atype, &aval, alg);
    if (OBJ_obj2nid(aoid) != NID_X9_62_id_ecPublicKey)
        goto err;
    /* If absent parameters get group from main key */
    if (atype == V_ASN1_UNDEF || atype == V_ASN1_NULL) {
        const EC_GROUP *grp;
        EVP_PKEY *pk;
        pk = EVP_PKEY_CTX_get0_pkey(pctx);
        if (!pk)
            goto err;
        grp = EC_KEY_get0_group(pk->pkey.ec);
        ecpeer = EC_KEY_new();
        if (ecpeer == NULL)
            goto err;
        if (!EC_KEY_set_group(ecpeer, grp))
            goto err;
    } else {
        ecpeer = eckey_type2param(atype, aval);
        if (!ecpeer)
            goto err;
    }
    /* We have parameters now set public key */
    plen = ASN1_STRING_length(pubkey);
    p = ASN1_STRING_get0_data(pubkey);
    if (!p || !plen)
        goto err;
    if (!o2i_ECPublicKey(&ecpeer, &p, plen))
        goto err;
    pkpeer = EVP_PKEY_new();
    if (pkpeer == NULL)
        goto err;
    EVP_PKEY_set1_EC_KEY(pkpeer, ecpeer);
    if (EVP_PKEY_derive_set_peer(pctx, pkpeer) > 0)
        rv = 1;
 err:
    EC_KEY_free(ecpeer);
    EVP_PKEY_free(pkpeer);
    return rv;
}

/* Set KDF parameters based on KDF NID */
static int ecdh_cms_set_kdf_param(EVP_PKEY_CTX *pctx, int eckdf_nid)
{
    int kdf_nid, kdfmd_nid, cofactor;
    const EVP_MD *kdf_md;
    if (eckdf_nid == NID_undef)
        return 0;

    /* Lookup KDF type, cofactor mode and digest */
    if (!OBJ_find_sigid_algs(eckdf_nid, &kdfmd_nid, &kdf_nid))
        return 0;

    if (kdf_nid == NID_dh_std_kdf)
        cofactor = 0;
    else if (kdf_nid == NID_dh_cofactor_kdf)
        cofactor = 1;
    else
        return 0;

    if (EVP_PKEY_CTX_set_ecdh_cofactor_mode(pctx, cofactor) <= 0)
        return 0;

    if (EVP_PKEY_CTX_set_ecdh_kdf_type(pctx, EVP_PKEY_ECDH_KDF_X9_63) <= 0)
        return 0;

    kdf_md = EVP_get_digestbynid(kdfmd_nid);
    if (!kdf_md)
        return 0;

    if (EVP_PKEY_CTX_set_ecdh_kdf_md(pctx, kdf_md) <= 0)
        return 0;
    return 1;
}

static int ecdh_cms_set_shared_info(EVP_PKEY_CTX *pctx, CMS_RecipientInfo *ri)
{
    int rv = 0;

    X509_ALGOR *alg, *kekalg = NULL;
    ASN1_OCTET_STRING *ukm;
    const unsigned char *p;
    unsigned char *der = NULL;
    int plen, keylen;
    const EVP_CIPHER *kekcipher;
    EVP_CIPHER_CTX *kekctx;

    if (!CMS_RecipientInfo_kari_get0_alg(ri, &alg, &ukm))
        return 0;

    if (!ecdh_cms_set_kdf_param(pctx, OBJ_obj2nid(alg->algorithm))) {
        ECerr(EC_F_ECDH_CMS_SET_SHARED_INFO, EC_R_KDF_PARAMETER_ERROR);
        return 0;
    }

    if (alg->parameter->type != V_ASN1_SEQUENCE)
        return 0;

    p = alg->parameter->value.sequence->data;
    plen = alg->parameter->value.sequence->length;
    kekalg = d2i_X509_ALGOR(NULL, &p, plen);
    if (!kekalg)
        goto err;
    kekctx = CMS_RecipientInfo_kari_get0_ctx(ri);
    if (!kekctx)
        goto err;
    kekcipher = EVP_get_cipherbyobj(kekalg->algorithm);
    if (!kekcipher || EVP_CIPHER_mode(kekcipher) != EVP_CIPH_WRAP_MODE)
        goto err;
    if (!EVP_EncryptInit_ex(kekctx, kekcipher, NULL, NULL, NULL))
        goto err;
    if (EVP_CIPHER_asn1_to_param(kekctx, kekalg->parameter) <= 0)
        goto err;

    keylen = EVP_CIPHER_CTX_key_length(kekctx);
    if (EVP_PKEY_CTX_set_ecdh_kdf_outlen(pctx, keylen) <= 0)
        goto err;

    plen = CMS_SharedInfo_encode(&der, kekalg, ukm, keylen);

    if (!plen)
        goto err;

    if (EVP_PKEY_CTX_set0_ecdh_kdf_ukm(pctx, der, plen) <= 0)
        goto err;
    der = NULL;

    rv = 1;
 err:
    X509_ALGOR_free(kekalg);
    OPENSSL_free(der);
    return rv;
}

static int ecdh_cms_decrypt(CMS_RecipientInfo *ri)
{
    EVP_PKEY_CTX *pctx;
    pctx = CMS_RecipientInfo_get0_pkey_ctx(ri);
    if (!pctx)
        return 0;
    /* See if we need to set peer key */
    if (!EVP_PKEY_CTX_get0_peerkey(pctx)) {
        X509_ALGOR *alg;
        ASN1_BIT_STRING *pubkey;
        if (!CMS_RecipientInfo_kari_get0_orig_id(ri, &alg, &pubkey,
                                                 NULL, NULL, NULL))
            return 0;
        if (!alg || !pubkey)
            return 0;
        if (!ecdh_cms_set_peerkey(pctx, alg, pubkey)) {
            ECerr(EC_F_ECDH_CMS_DECRYPT, EC_R_PEER_KEY_ERROR);
            return 0;
        }
    }
    /* Set ECDH derivation parameters and initialise unwrap context */
    if (!ecdh_cms_set_shared_info(pctx, ri)) {
        ECerr(EC_F_ECDH_CMS_DECRYPT, EC_R_SHARED_INFO_ERROR);
        return 0;
    }
    return 1;
}

static int ecdh_cms_encrypt(CMS_RecipientInfo *ri)
{
    EVP_PKEY_CTX *pctx;
    EVP_PKEY *pkey;
    EVP_CIPHER_CTX *ctx;
    int keylen;
    X509_ALGOR *talg, *wrap_alg = NULL;
    const ASN1_OBJECT *aoid;
    ASN1_BIT_STRING *pubkey;
    ASN1_STRING *wrap_str;
    ASN1_OCTET_STRING *ukm;
    unsigned char *penc = NULL;
    int penclen;
    int rv = 0;
    int ecdh_nid, kdf_type, kdf_nid, wrap_nid;
    const EVP_MD *kdf_md;
    pctx = CMS_RecipientInfo_get0_pkey_ctx(ri);
    if (!pctx)
        return 0;
    /* Get ephemeral key */
    pkey = EVP_PKEY_CTX_get0_pkey(pctx);
    if (!CMS_RecipientInfo_kari_get0_orig_id(ri, &talg, &pubkey,
                                             NULL, NULL, NULL))
        goto err;
    X509_ALGOR_get0(&aoid, NULL, NULL, talg);
    /* Is everything uninitialised? */
    if (aoid == OBJ_nid2obj(NID_undef)) {

        EC_KEY *eckey = pkey->pkey.ec;
        /* Set the key */
        unsigned char *p;

        penclen = i2o_ECPublicKey(eckey, NULL);
        if (penclen <= 0)
            goto err;
        penc = OPENSSL_malloc(penclen);
        if (penc == NULL)
            goto err;
        p = penc;
        penclen = i2o_ECPublicKey(eckey, &p);
        if (penclen <= 0)
            goto err;
        ASN1_STRING_set0(pubkey, penc, penclen);
        pubkey->flags &= ~(ASN1_STRING_FLAG_BITS_LEFT | 0x07);
        pubkey->flags |= ASN1_STRING_FLAG_BITS_LEFT;

        penc = NULL;
        X509_ALGOR_set0(talg, OBJ_nid2obj(NID_X9_62_id_ecPublicKey),
                        V_ASN1_UNDEF, NULL);
    }

    /* See if custom parameters set */
    kdf_type = EVP_PKEY_CTX_get_ecdh_kdf_type(pctx);
    if (kdf_type <= 0)
        goto err;
    if (!EVP_PKEY_CTX_get_ecdh_kdf_md(pctx, &kdf_md))
        goto err;
    ecdh_nid = EVP_PKEY_CTX_get_ecdh_cofactor_mode(pctx);
    if (ecdh_nid < 0)
        goto err;
    else if (ecdh_nid == 0)
        ecdh_nid = NID_dh_std_kdf;
    else if (ecdh_nid == 1)
        ecdh_nid = NID_dh_cofactor_kdf;

    if (kdf_type == EVP_PKEY_ECDH_KDF_NONE) {
        kdf_type = EVP_PKEY_ECDH_KDF_X9_63;
        if (EVP_PKEY_CTX_set_ecdh_kdf_type(pctx, kdf_type) <= 0)
            goto err;
    } else
        /* Unknown KDF */
        goto err;
    if (kdf_md == NULL) {
        /* Fixme later for better MD */
        kdf_md = EVP_sha1();
        if (EVP_PKEY_CTX_set_ecdh_kdf_md(pctx, kdf_md) <= 0)
            goto err;
    }

    if (!CMS_RecipientInfo_kari_get0_alg(ri, &talg, &ukm))
        goto err;

    /* Lookup NID for KDF+cofactor+digest */

    if (!OBJ_find_sigid_by_algs(&kdf_nid, EVP_MD_type(kdf_md), ecdh_nid))
        goto err;
    /* Get wrap NID */
    ctx = CMS_RecipientInfo_kari_get0_ctx(ri);
    wrap_nid = EVP_CIPHER_CTX_type(ctx);
    keylen = EVP_CIPHER_CTX_key_length(ctx);

    /* Package wrap algorithm in an AlgorithmIdentifier */

    wrap_alg = X509_ALGOR_new();
    if (wrap_alg == NULL)
        goto err;
    wrap_alg->algorithm = OBJ_nid2obj(wrap_nid);
    wrap_alg->parameter = ASN1_TYPE_new();
    if (wrap_alg->parameter == NULL)
        goto err;
    if (EVP_CIPHER_param_to_asn1(ctx, wrap_alg->parameter) <= 0)
        goto err;
    if (ASN1_TYPE_get(wrap_alg->parameter) == NID_undef) {
        ASN1_TYPE_free(wrap_alg->parameter);
        wrap_alg->parameter = NULL;
    }

    if (EVP_PKEY_CTX_set_ecdh_kdf_outlen(pctx, keylen) <= 0)
        goto err;

    penclen = CMS_SharedInfo_encode(&penc, wrap_alg, ukm, keylen);

    if (!penclen)
        goto err;

    if (EVP_PKEY_CTX_set0_ecdh_kdf_ukm(pctx, penc, penclen) <= 0)
        goto err;
    penc = NULL;

    /*
     * Now need to wrap encoding of wrap AlgorithmIdentifier into parameter
     * of another AlgorithmIdentifier.
     */
    penclen = i2d_X509_ALGOR(wrap_alg, &penc);
    if (!penc || !penclen)
        goto err;
    wrap_str = ASN1_STRING_new();
    if (wrap_str == NULL)
        goto err;
    ASN1_STRING_set0(wrap_str, penc, penclen);
    penc = NULL;
    X509_ALGOR_set0(talg, OBJ_nid2obj(kdf_nid), V_ASN1_SEQUENCE, wrap_str);

    rv = 1;

 err:
    OPENSSL_free(penc);
    X509_ALGOR_free(wrap_alg);
    return rv;
}

#endif