/*

 * Copyright 2006-2026 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

 */

#include <assert.h>

#include <openssl/cms.h>

#include <openssl/dh.h>

#include <openssl/err.h>

#include <openssl/core_names.h>

#include "internal/sizes.h"

#include "crypto/asn1.h"

#include "crypto/evp.h"

#include "cms_local.h"

static int dh_cms_set_peerkey(EVP_PKEY_CTX *pctx,

    X509_ALGOR *alg, ASN1_BIT_STRING *pubkey)

{

    const ASN1_OBJECT *aoid;

    int atype;

    const void *aval;

    ASN1_INTEGER *public_key = NULL;

    int rv = 0;

    EVP_PKEY *pkpeer = NULL, *pk = NULL;

    BIGNUM *bnpub = NULL;

    const unsigned char *p;

    unsigned char *buf = NULL;

    int plen;

    X509_ALGOR_get0(&aoid, &atype, &aval, alg);

    if (OBJ_obj2nid(aoid) != NID_dhpublicnumber)

        goto err;

    /* Only absent parameters allowed in RFC XXXX */

    if (atype != V_ASN1_UNDEF && atype != V_ASN1_NULL)

        goto err;

    pk = EVP_PKEY_CTX_get0_pkey(pctx);

    if (pk == NULL || !EVP_PKEY_is_a(pk, "DHX"))

        goto err;

    /* Get public key */

    plen = ASN1_STRING_length(pubkey);

    p = ASN1_STRING_get0_data(pubkey);

    if (p == NULL || plen == 0)

        goto err;

    if ((public_key = d2i_ASN1_INTEGER(NULL, &p, plen)) == NULL)

        goto err;

    /*

     * Pad to full p parameter size as that is checked by

     * EVP_PKEY_set1_encoded_public_key()

     */

    plen = EVP_PKEY_get_size(pk);

    if ((bnpub = ASN1_INTEGER_to_BN(public_key, NULL)) == NULL)

        goto err;

    if ((buf = OPENSSL_malloc(plen)) == NULL)

        goto err;

    if (BN_bn2binpad(bnpub, buf, plen) < 0)

        goto err;

    pkpeer = EVP_PKEY_new();

    if (pkpeer == NULL

        || !EVP_PKEY_copy_parameters(pkpeer, pk)

        || !EVP_PKEY_set1_encoded_public_key(pkpeer, buf, plen))

        goto err;

    if (EVP_PKEY_derive_set_peer(pctx, pkpeer) > 0)

        rv = 1;

err:

    ASN1_INTEGER_free(public_key);

    BN_free(bnpub);

    OPENSSL_free(buf);

    EVP_PKEY_free(pkpeer);

    return rv;

}

static int dh_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 *dukm = NULL;

    size_t dukmlen = 0;

    int keylen, plen;

    EVP_CIPHER *kekcipher = NULL;

    EVP_CIPHER_CTX *kekctx;

    const ASN1_OBJECT *aoid;

    const void *parameter = NULL;

    int ptype = 0;

    char name[OSSL_MAX_NAME_SIZE];

    if (!CMS_RecipientInfo_kari_get0_alg(ri, &alg, &ukm))

        goto err;

    X509_ALGOR_get0(&aoid, &ptype, &parameter, alg);

    /*

     * For DH we only have one OID permissible. If ever any more get defined

     * we will need something cleverer.

     */

    if (OBJ_obj2nid(aoid) != NID_id_smime_alg_ESDH) {

        ERR_raise(ERR_LIB_CMS, CMS_R_KDF_PARAMETER_ERROR);

        goto err;

    }

    if (EVP_PKEY_CTX_set_dh_kdf_type(pctx, EVP_PKEY_DH_KDF_X9_42) <= 0

        || EVP_PKEY_CTX_set_dh_kdf_md(pctx, EVP_sha1()) <= 0)

        goto err;

    if (ptype != V_ASN1_SEQUENCE)

        goto err;

    p = ASN1_STRING_get0_data(parameter);

    plen = ASN1_STRING_length(parameter);

    kekalg = d2i_X509_ALGOR(NULL, &p, plen);

    if (kekalg == NULL)

        goto err;

    kekctx = CMS_RecipientInfo_kari_get0_ctx(ri);

    if (kekctx == NULL)

        goto err;

    if (OBJ_obj2txt(name, sizeof(name), kekalg->algorithm, 0) <= 0)

        goto err;

    kekcipher = EVP_CIPHER_fetch(pctx->libctx, name, pctx->propquery);

    if (kekcipher == NULL

        || EVP_CIPHER_get_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_get_key_length(kekctx);

    if (EVP_PKEY_CTX_set_dh_kdf_outlen(pctx, keylen) <= 0)

        goto err;

    /* Use OBJ_nid2obj to ensure we use built in OID that isn't freed */

    if (EVP_PKEY_CTX_set0_dh_kdf_oid(pctx,

            OBJ_nid2obj(EVP_CIPHER_get_type(kekcipher)))

        <= 0)

        goto err;

    if (ukm != NULL) {

        dukmlen = ASN1_STRING_length(ukm);

        dukm = OPENSSL_memdup(ASN1_STRING_get0_data(ukm), dukmlen);

        if (dukm == NULL)

            goto err;

    }

    if (EVP_PKEY_CTX_set0_dh_kdf_ukm(pctx, dukm, dukmlen) <= 0)

        goto err;

    dukm = NULL;

    rv = 1;

err:

    X509_ALGOR_free(kekalg);

    EVP_CIPHER_free(kekcipher);

    OPENSSL_free(dukm);

    return rv;

}

static int dh_cms_decrypt(CMS_RecipientInfo *ri)

{

    EVP_PKEY_CTX *pctx = CMS_RecipientInfo_get0_pkey_ctx(ri);

    if (pctx == NULL)

        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 == NULL || pubkey == NULL)

            return 0;

        if (!dh_cms_set_peerkey(pctx, alg, pubkey)) {

            ERR_raise(ERR_LIB_CMS, CMS_R_PEER_KEY_ERROR);

            return 0;

        }

    }

    /* Set DH derivation parameters and initialise unwrap context */

    if (!dh_cms_set_shared_info(pctx, ri)) {

        ERR_raise(ERR_LIB_CMS, CMS_R_SHARED_INFO_ERROR);

        return 0;

    }

    return 1;

}

static int dh_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, *dukm = NULL;

    int penclen;

    size_t dukmlen = 0;

    int rv = 0;

    int kdf_type, wrap_nid;

    const EVP_MD *kdf_md;

    pctx = CMS_RecipientInfo_get0_pkey_ctx(ri);

    if (pctx == NULL)

        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;

    /* Is everything uninitialised? */

    X509_ALGOR_get0(&aoid, NULL, NULL, talg);

    if (aoid == OBJ_nid2obj(NID_undef)) {

        BIGNUM *bn_pub_key = NULL;

        ASN1_INTEGER *pubk;

        if (!EVP_PKEY_get_bn_param(pkey, OSSL_PKEY_PARAM_PUB_KEY, &bn_pub_key))

            goto err;

        pubk = BN_to_ASN1_INTEGER(bn_pub_key, NULL);

        BN_free(bn_pub_key);

        if (pubk == NULL)

            goto err;

        /* Set the key */

        penclen = i2d_ASN1_INTEGER(pubk, &penc);

        ASN1_INTEGER_free(pubk);

        if (penclen <= 0)

            goto err;

        ASN1_STRING_set0(pubkey, penc, penclen);

        ossl_asn1_string_set_bits_left(pubkey, 0);

        penc = NULL;

        (void)X509_ALGOR_set0(talg, OBJ_nid2obj(NID_dhpublicnumber),

            V_ASN1_UNDEF, NULL); /* cannot fail */

    }

    /* See if custom parameters set */

    kdf_type = EVP_PKEY_CTX_get_dh_kdf_type(pctx);

    if (kdf_type <= 0 || EVP_PKEY_CTX_get_dh_kdf_md(pctx, &kdf_md) <= 0)

        goto err;

    if (kdf_type == EVP_PKEY_DH_KDF_NONE) {

        kdf_type = EVP_PKEY_DH_KDF_X9_42;

        if (EVP_PKEY_CTX_set_dh_kdf_type(pctx, kdf_type) <= 0)

            goto err;

    } else if (kdf_type != EVP_PKEY_DH_KDF_X9_42)

        /* Unknown KDF */

        goto err;

    if (kdf_md == NULL) {

        /* Only SHA1 supported */

        kdf_md = EVP_sha1();

        if (EVP_PKEY_CTX_set_dh_kdf_md(pctx, kdf_md) <= 0)

            goto err;

    } else if (EVP_MD_get_type(kdf_md) != NID_sha1)

        /* Unsupported digest */

        goto err;

    if (!CMS_RecipientInfo_kari_get0_alg(ri, &talg, &ukm))

        goto err;

    /* Get wrap NID */

    ctx = CMS_RecipientInfo_kari_get0_ctx(ri);

    wrap_nid = EVP_CIPHER_CTX_get_type(ctx);

    if (EVP_PKEY_CTX_set0_dh_kdf_oid(pctx, OBJ_nid2obj(wrap_nid)) <= 0)

        goto err;

    keylen = EVP_CIPHER_CTX_get_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_dh_kdf_outlen(pctx, keylen) <= 0)

        goto err;

    if (ukm != NULL) {

        dukmlen = ASN1_STRING_length(ukm);

        dukm = OPENSSL_memdup(ASN1_STRING_get0_data(ukm), dukmlen);

        if (dukm == NULL)

            goto err;

    }

    if (EVP_PKEY_CTX_set0_dh_kdf_ukm(pctx, dukm, dukmlen) <= 0)

        goto err;

    dukm = NULL;

    /*

     * Now need to wrap encoding of wrap AlgorithmIdentifier into parameter

     * of another AlgorithmIdentifier.

     */

    penc = NULL;

    penclen = i2d_X509_ALGOR(wrap_alg, &penc);

    if (penclen <= 0)

        goto err;

    wrap_str = ASN1_STRING_new();

    if (wrap_str == NULL)

        goto err;

    ASN1_STRING_set0(wrap_str, penc, penclen);

    penc = NULL;

    rv = X509_ALGOR_set0(talg, OBJ_nid2obj(NID_id_smime_alg_ESDH),

        V_ASN1_SEQUENCE, wrap_str);

    if (!rv)

        ASN1_STRING_free(wrap_str);

err:

    OPENSSL_free(penc);

    X509_ALGOR_free(wrap_alg);

    OPENSSL_free(dukm);

    return rv;

}

int ossl_cms_dh_envelope(CMS_RecipientInfo *ri, int decrypt)

{

    assert(decrypt == 0 || decrypt == 1);

    if (decrypt == 1)

        return dh_cms_decrypt(ri);

    if (decrypt == 0)

        return dh_cms_encrypt(ri);

    ERR_raise(ERR_LIB_CMS, CMS_R_NOT_SUPPORTED_FOR_THIS_KEY_TYPE);

    return 0;

}