/* $OpenBSD: dnssec.c,v 1.28 2021/10/09 18:43:50 deraadt Exp $   */

/*
 * Copyright (c) 2001 Håkan Olsson.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>

#include <openssl/rsa.h>

#ifdef LWRES
#include <lwres/netdb.h>
#include <dns/keyvalues.h>
#else
#include <netdb.h>
#endif

#include "dnssec.h"
#include "exchange.h"
#include "ipsec_num.h"
#include "libcrypto.h"
#include "log.h"
#include "message.h"
#include "transport.h"
#include "util.h"

#ifndef DNS_UFQDN_SEPARATOR
#define DNS_UFQDN_SEPARATOR "._ipsec."
#endif

/* adapted from <dns/rdatastruct.h> / RFC 2535  */
struct dns_rdata_key {
        u_int16_t       flags;
        u_int8_t        protocol;
        u_int8_t        algorithm;
        u_int16_t       datalen;
        unsigned char  *data;
};

void *
dns_get_key(int type, struct message *msg, int *keylen)
{
        struct exchange *exchange = msg->exchange;
        struct rrsetinfo *rr;
        struct dns_rdata_key key_rr;
        char            name[HOST_NAME_MAX+1];
        in_addr_t       ip4;
        u_int8_t        algorithm, *id, *umark;
        size_t          id_len;
        int             ret, i;

        switch (type) {
        case IKE_AUTH_RSA_SIG:
                algorithm = DNS_KEYALG_RSA;
                break;

        case IKE_AUTH_RSA_ENC:
        case IKE_AUTH_RSA_ENC_REV:
                /* XXX Not yet. */
                /* algorithm = DNS_KEYALG_RSA; */
                return 0;

        case IKE_AUTH_DSS:
                /* XXX Not yet. */
                /* algorithm = DNS_KEYALG_DSS; */
                return 0;

        case IKE_AUTH_PRE_SHARED:
        default:
                return 0;
        }

        id = exchange->initiator ? exchange->id_r : exchange->id_i;
        id_len = exchange->initiator ? exchange->id_r_len : exchange->id_i_len;
        bzero(name, sizeof name);

        if (!id || id_len == 0) {
                log_print("dns_get_key: ID is missing");
                return 0;
        }
        /* Exchanges (and SAs) don't carry the ID in ISAKMP form */
        id -= ISAKMP_GEN_SZ;
        id_len += ISAKMP_GEN_SZ - ISAKMP_ID_DATA_OFF;

        switch (GET_ISAKMP_ID_TYPE(id)) {
        case IPSEC_ID_IPV4_ADDR:
                /* We want to lookup a KEY RR in the reverse zone.  */
                if (id_len < sizeof ip4)
                        return 0;
                memcpy(&ip4, id + ISAKMP_ID_DATA_OFF, sizeof ip4);
                snprintf(name, sizeof name, "%d.%d.%d.%d.in-addr.arpa.", ip4
                    >> 24, (ip4 >> 16) & 0xFF, (ip4 >> 8) & 0xFF, ip4 & 0xFF);
                break;

        case IPSEC_ID_IPV6_ADDR:
                /* XXX Not yet. */
                return 0;
                break;

        case IPSEC_ID_FQDN:
                if ((id_len + 1) >= sizeof name)
                        return 0;
                /* ID is not NULL-terminated. Add trailing dot and NULL.  */
                memcpy(name, id + ISAKMP_ID_DATA_OFF, id_len);
                *(name + id_len) = '.';
                *(name + id_len + 1) = '\0';
                break;

        case IPSEC_ID_USER_FQDN:
                /*
                 * Some special handling here. We want to convert the ID
                 * 'user@host.domain' string into 'user._ipsec.host.domain.'.
                 */
                if ((id_len + sizeof(DNS_UFQDN_SEPARATOR)) >= sizeof name)
                        return 0;
                /* Look for the '@' separator.  */
                for (umark = id + ISAKMP_ID_DATA_OFF; (umark - id) < id_len;
                    umark++)
                        if (*umark == '@')
                                break;
                if (*umark != '@') {
                        LOG_DBG((LOG_MISC, 50, "dns_get_key: bad UFQDN ID"));
                        return 0;
                }
                *umark++ = '\0';
                /* id is now terminated. 'umark', however, is not.  */
                snprintf(name, sizeof name, "%s%s", id + ISAKMP_ID_DATA_OFF,
                    DNS_UFQDN_SEPARATOR);
                memcpy(name + strlen(name), umark, id_len - strlen(id) - 1);
                *(name + id_len + sizeof(DNS_UFQDN_SEPARATOR) - 2) = '.';
                *(name + id_len + sizeof(DNS_UFQDN_SEPARATOR) - 1) = '\0';
                break;

        default:
                return 0;
        }

        LOG_DBG((LOG_MISC, 50, "dns_get_key: trying KEY RR for %s", name));
        ret = getrrsetbyname(name, C_IN, T_KEY, 0, &rr);

        if (ret) {
                LOG_DBG((LOG_MISC, 30, "dns_get_key: no DNS responses "
                    "(error %d)", ret));
                return 0;
        }
        LOG_DBG((LOG_MISC, 80,
            "dns_get_key: rrset class %d type %d ttl %d nrdatas %d nrsigs %d",
            rr->rri_rdclass, rr->rri_rdtype, rr->rri_ttl, rr->rri_nrdatas,
            rr->rri_nsigs));

        /* We don't accept unvalidated data. */
        if (!(rr->rri_flags & RRSET_VALIDATED)) {
                LOG_DBG((LOG_MISC, 10, "dns_get_key: "
                    "got unvalidated response"));
                freerrset(rr);
                return 0;
        }
        /* Sanity. */
        if (rr->rri_nrdatas == 0 || rr->rri_rdtype != T_KEY) {
                LOG_DBG((LOG_MISC, 30, "dns_get_key: no KEY RRs received"));
                freerrset(rr);
                return 0;
        }
        bzero(&key_rr, sizeof key_rr);

        /*
         * Find a key with the wanted algorithm, if any.
         * XXX If there are several keys present, we currently only find the
         * first.
         */
        for (i = 0; i < rr->rri_nrdatas && key_rr.datalen == 0; i++) {
                key_rr.flags = ntohs((u_int16_t) * rr->rri_rdatas[i].rdi_data);
                key_rr.protocol = *(rr->rri_rdatas[i].rdi_data + 2);
                key_rr.algorithm = *(rr->rri_rdatas[i].rdi_data + 3);

                if (key_rr.protocol != DNS_KEYPROTO_IPSEC) {
                        LOG_DBG((LOG_MISC, 50, "dns_get_key: ignored "
                            "non-IPsec key"));
                        continue;
                }
                if (key_rr.algorithm != algorithm) {
                        LOG_DBG((LOG_MISC, 50, "dns_get_key: ignored "
                            "key with other alg"));
                        continue;
                }
                key_rr.datalen = rr->rri_rdatas[i].rdi_length - 4;
                if (key_rr.datalen <= 0) {
                        LOG_DBG((LOG_MISC, 50, "dns_get_key: "
                            "ignored bad key"));
                        key_rr.datalen = 0;
                        continue;
                }
                /* This key seems to fit our requirements... */
                key_rr.data = malloc(key_rr.datalen);
                if (!key_rr.data) {
                        log_error("dns_get_key: malloc (%d) failed",
                            key_rr.datalen);
                        freerrset(rr);
                        return 0;
                }
                memcpy(key_rr.data, rr->rri_rdatas[i].rdi_data + 4,
                    key_rr.datalen);
                *keylen = key_rr.datalen;
        }

        freerrset(rr);

        if (key_rr.datalen)
                return key_rr.data;
        return 0;
}

int
dns_RSA_dns_to_x509(u_int8_t *key, int keylen, RSA **rsa_key)
{
        RSA     *rsa;
        int      key_offset;
        u_int8_t e_len;

        if (!key || keylen <= 0) {
                log_print("dns_RSA_dns_to_x509: invalid public key");
                return -1;
        }
        rsa = RSA_new();
        if (rsa == NULL) {
                log_error("dns_RSA_dns_to_x509: "
                    "failed to allocate new RSA struct");
                return -1;
        }
        e_len = *key;
        key_offset = 1;

        if (e_len == 0) {
                if (keylen < 3) {
                        log_print("dns_RSA_dns_to_x509: invalid public key");
                        RSA_free(rsa);
                        return -1;
                }
                e_len = *(key + key_offset++) << 8;
                e_len += *(key + key_offset++);
        }
        if (e_len > (keylen - key_offset)) {
                log_print("dns_RSA_dns_to_x509: invalid public key");
                RSA_free(rsa);
                return -1;
        }
        rsa->e = BN_bin2bn(key + key_offset, e_len, NULL);
        key_offset += e_len;

        /* XXX if (keylen <= key_offset) -> "invalid public key" ? */

        rsa->n = BN_bin2bn(key + key_offset, keylen - key_offset, NULL);

        *rsa_key = rsa;

        LOG_DBG((LOG_MISC, 30, "dns_RSA_dns_to_x509: got %d bits RSA key",
            BN_num_bits(rsa->n)));
        return 0;
}

#if notyet
int
dns_RSA_x509_to_dns(RSA *rsa_key, u_int8_t *key, int *keylen)
{
        return 0;
}
#endif