/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 1994, Garrett Wollman
 *
 * 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 CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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 "namespace.h"
#include "reentrant.h"
#include <sys/param.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdio.h>
#include <ctype.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <nsswitch.h>
#include <arpa/nameser.h>               /* XXX hack for _res */
#include <resolv.h>                     /* XXX hack for _res */
#include "un-namespace.h"
#include "netdb_private.h"
#ifdef NS_CACHING
#include "nscache.h"
#endif

static int gethostbyname_internal(const char *, int, struct hostent *, char *,
    size_t, struct hostent **, int *, res_state);

/* Host lookup order if nsswitch.conf is broken or nonexistent */
static const ns_src default_src[] = {
        { NSSRC_FILES, NS_SUCCESS },
        { NSSRC_DNS, NS_SUCCESS },
        { 0 }
};
#ifdef NS_CACHING
static int host_id_func(char *, size_t *, va_list, void *);
static int host_marshal_func(char *, size_t *, void *, va_list, void *);
static int host_unmarshal_func(char *, size_t, void *, va_list, void *);
#endif

NETDB_THREAD_ALLOC(hostent)
NETDB_THREAD_ALLOC(hostent_data)
NETDB_THREAD_ALLOC(hostdata)

static void
hostent_free(void *ptr)
{
        free(ptr);
}

static void
hostent_data_free(void *ptr)
{
        struct hostent_data *hed = ptr;

        if (hed == NULL)
                return;
        hed->stayopen = 0;
        _endhosthtent(hed);
        free(hed);
}

static void
hostdata_free(void *ptr)
{
        free(ptr);
}

int
__copy_hostent(struct hostent *he, struct hostent *hptr, char *buf,
    size_t buflen)
{
        char *cp;
        char **ptr;
        int i, n;
        int nptr, len;

        /* Find out the amount of space required to store the answer. */
        nptr = 2; /* NULL ptrs */
        len = (char *)ALIGN(buf) - buf;
        for (i = 0; he->h_addr_list[i]; i++, nptr++) {
                len += he->h_length;
        }
        for (i = 0; he->h_aliases[i]; i++, nptr++) {
                len += strlen(he->h_aliases[i]) + 1;
        }
        len += strlen(he->h_name) + 1;
        len += nptr * sizeof(char*);

        if (len > buflen) {
                errno = ERANGE;
                return (-1);
        }

        /* copy address size and type */
        hptr->h_addrtype = he->h_addrtype;
        n = hptr->h_length = he->h_length;

        ptr = (char **)ALIGN(buf);
        cp = (char *)ALIGN(buf) + nptr * sizeof(char *);

        /* copy address list */
        hptr->h_addr_list = ptr;
        for (i = 0; he->h_addr_list[i]; i++ , ptr++) {
                memcpy(cp, he->h_addr_list[i], n);
                hptr->h_addr_list[i] = cp;
                cp += n;
        }
        hptr->h_addr_list[i] = NULL;
        ptr++;

        /* copy official name */
        n = strlen(he->h_name) + 1;
        strcpy(cp, he->h_name);
        hptr->h_name = cp;
        cp += n;

        /* copy aliases */
        hptr->h_aliases = ptr;
        for (i = 0 ; he->h_aliases[i]; i++) {
                n = strlen(he->h_aliases[i]) + 1;
                strcpy(cp, he->h_aliases[i]);
                hptr->h_aliases[i] = cp;
                cp += n;
        }
        hptr->h_aliases[i] = NULL;

        return (0);
}

#ifdef NS_CACHING
static int
host_id_func(char *buffer, size_t *buffer_size, va_list ap, void *cache_mdata)
{
        res_state statp;
        u_long res_options;

        const int op_id = 1;
        char *str;
        void *addr;
        socklen_t len;
        int type;

        size_t desired_size, size;
        enum nss_lookup_type lookup_type;
        char *p;
        int res = NS_UNAVAIL;

        statp = __res_state();
        res_options = statp->options & (RES_RECURSE | RES_DEFNAMES |
            RES_DNSRCH | RES_NOALIASES | RES_USE_INET6);

        lookup_type = (enum nss_lookup_type)(uintptr_t)cache_mdata;
        switch (lookup_type) {
        case nss_lt_name:
                str = va_arg(ap, char *);
                type = va_arg(ap, int);

                size = strlen(str);
                desired_size = sizeof(res_options) + sizeof(int) +
                    sizeof(enum nss_lookup_type) + sizeof(int) + size + 1;

                if (desired_size > *buffer_size) {
                        res = NS_RETURN;
                        goto fin;
                }

                p = buffer;

                memcpy(p, &res_options, sizeof(res_options));
                p += sizeof(res_options);

                memcpy(p, &op_id, sizeof(int));
                p += sizeof(int);

                memcpy(p, &lookup_type, sizeof(enum nss_lookup_type));
                p += sizeof(int);

                memcpy(p, &type, sizeof(int));
                p += sizeof(int);

                memcpy(p, str, size + 1);

                res = NS_SUCCESS;
                break;
        case nss_lt_id:
                addr = va_arg(ap, void *);
                len = va_arg(ap, socklen_t);
                type = va_arg(ap, int);

                desired_size = sizeof(res_options) + sizeof(int) +
                    sizeof(enum nss_lookup_type) + sizeof(int) +
                    sizeof(socklen_t) + len;

                if (desired_size > *buffer_size) {
                        res = NS_RETURN;
                        goto fin;
                }

                p = buffer;
                memcpy(p, &res_options, sizeof(res_options));
                p += sizeof(res_options);

                memcpy(p, &op_id, sizeof(int));
                p += sizeof(int);

                memcpy(p, &lookup_type, sizeof(enum nss_lookup_type));
                p += sizeof(int);

                memcpy(p, &type, sizeof(int));
                p += sizeof(int);

                memcpy(p, &len, sizeof(socklen_t));
                p += sizeof(socklen_t);

                memcpy(p, addr, len);

                res = NS_SUCCESS;
                break;
        default:
                /* should be unreachable */
                return (NS_UNAVAIL);
        }

fin:
        *buffer_size = desired_size;
        return (res);
}

static int
host_marshal_func(char *buffer, size_t *buffer_size, void *retval, va_list ap,
    void *cache_mdata)
{
        char *str __unused;
        void *addr __unused;
        socklen_t len __unused;
        int type __unused;
        struct hostent *ht;

        struct hostent new_ht;
        size_t desired_size, aliases_size, addr_size, size;
        char *p, **iter;

        switch ((enum nss_lookup_type)(uintptr_t)cache_mdata) {
        case nss_lt_name:
                str = va_arg(ap, char *);
                type = va_arg(ap, int);
                break;
        case nss_lt_id:
                addr = va_arg(ap, void *);
                len = va_arg(ap, socklen_t);
                type = va_arg(ap, int);
                break;
        default:
                /* should be unreachable */
                return (NS_UNAVAIL);
        }
        ht = va_arg(ap, struct hostent *);

        desired_size = _ALIGNBYTES + sizeof(struct hostent) + sizeof(char *);
        if (ht->h_name != NULL)
                desired_size += strlen(ht->h_name) + 1;

        if (ht->h_aliases != NULL) {
                aliases_size = 0;
                for (iter = ht->h_aliases; *iter; ++iter) {
                        desired_size += strlen(*iter) + 1;
                        ++aliases_size;
                }

                desired_size += _ALIGNBYTES +
                    (aliases_size + 1) * sizeof(char *);
        }

        if (ht->h_addr_list != NULL) {
                addr_size = 0;
                for (iter = ht->h_addr_list; *iter; ++iter)
                        ++addr_size;

                desired_size += addr_size * _ALIGN(ht->h_length);
                desired_size += _ALIGNBYTES + (addr_size + 1) * sizeof(char *);
        }

        if (desired_size > *buffer_size) {
                /* this assignment is here for future use */
                *buffer_size = desired_size;
                return (NS_RETURN);
        }

        memcpy(&new_ht, ht, sizeof(struct hostent));
        memset(buffer, 0, desired_size);

        *buffer_size = desired_size;
        p = buffer + sizeof(struct hostent) + sizeof(char *);
        memcpy(buffer + sizeof(struct hostent), &p, sizeof(char *));
        p = (char *)_ALIGN(p);

        if (new_ht.h_name != NULL) {
                size = strlen(new_ht.h_name);
                memcpy(p, new_ht.h_name, size);
                new_ht.h_name = p;
                p += size + 1;
        }

        if (new_ht.h_aliases != NULL) {
                p = (char *)_ALIGN(p);
                memcpy(p, new_ht.h_aliases, sizeof(char *) * aliases_size);
                new_ht.h_aliases = (char **)p;
                p += sizeof(char *) * (aliases_size + 1);

                for (iter = new_ht.h_aliases; *iter; ++iter) {
                        size = strlen(*iter);
                        memcpy(p, *iter, size);
                        *iter = p;
                        p += size + 1;
                }
        }

        if (new_ht.h_addr_list != NULL) {
                p = (char *)_ALIGN(p);
                memcpy(p, new_ht.h_addr_list, sizeof(char *) * addr_size);
                new_ht.h_addr_list = (char **)p;
                p += sizeof(char *) * (addr_size + 1);

                size = _ALIGN(new_ht.h_length);
                for (iter = new_ht.h_addr_list; *iter; ++iter) {
                        memcpy(p, *iter, size);
                        *iter = p;
                        p += size + 1;
                }
        }
        memcpy(buffer, &new_ht, sizeof(struct hostent));
        return (NS_SUCCESS);
}

static int
host_unmarshal_func(char *buffer, size_t buffer_size, void *retval, va_list ap,
    void *cache_mdata)
{
        char *str __unused;
        void *addr __unused;
        socklen_t len __unused;
        int type __unused;
        struct hostent *ht;

        char *p;
        char **iter;
        char *orig_buf;
        size_t orig_buf_size;

        switch ((enum nss_lookup_type)(uintptr_t)cache_mdata) {
        case nss_lt_name:
                str = va_arg(ap, char *);
                type = va_arg(ap, int);
                break;
        case nss_lt_id:
                addr = va_arg(ap, void *);
                len = va_arg(ap, socklen_t);
                type = va_arg(ap, int);
                break;
        default:
                /* should be unreachable */
                return (NS_UNAVAIL);
        }

        ht = va_arg(ap, struct hostent *);
        orig_buf = va_arg(ap, char *);
        orig_buf_size = va_arg(ap, size_t);

        if (orig_buf_size <
            buffer_size - sizeof(struct hostent) - sizeof(char *)) {
                errno = ERANGE;
                return (NS_RETURN);
        }

        memcpy(ht, buffer, sizeof(struct hostent));
        memcpy(&p, buffer + sizeof(struct hostent), sizeof(char *));

        orig_buf = (char *)_ALIGN(orig_buf);
        memcpy(orig_buf, buffer + sizeof(struct hostent) + sizeof(char *) +
            __nss_buf_misalignment(p),
            buffer_size - sizeof(struct hostent) - sizeof(char *) -
            __nss_buf_misalignment(p));
        p = (char *)_ALIGN(p);

        NS_APPLY_OFFSET(ht->h_name, orig_buf, p, char *);
        if (ht->h_aliases != NULL) {
                NS_APPLY_OFFSET(ht->h_aliases, orig_buf, p, char **);

                for (iter = ht->h_aliases; *iter; ++iter)
                        NS_APPLY_OFFSET(*iter, orig_buf, p, char *);
        }

        if (ht->h_addr_list != NULL) {
                NS_APPLY_OFFSET(ht->h_addr_list, orig_buf, p, char **);

                for (iter = ht->h_addr_list; *iter; ++iter)
                        NS_APPLY_OFFSET(*iter, orig_buf, p, char *);
        }

        *((struct hostent **)retval) = ht;
        return (NS_SUCCESS);
}
#endif /* NS_CACHING */

static int
fakeaddr(const char *name, int af, struct hostent *hp, char *buf,
    size_t buflen, res_state statp)
{
        struct hostent_data *hed;
        struct hostent he;

        if ((hed = __hostent_data_init()) == NULL) {
                errno = ENOMEM;
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                return (-1);
        }

        if ((af != AF_INET ||
            inet_aton(name, (struct in_addr *)hed->host_addr) != 1) &&
            inet_pton(af, name, hed->host_addr) != 1) {
                RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
                return (-1);
        }
        strncpy(hed->hostbuf, name, MAXDNAME);
        hed->hostbuf[MAXDNAME] = '\0';
        if (af == AF_INET && (statp->options & RES_USE_INET6) != 0U) {
                _map_v4v6_address((char *)hed->host_addr,
                    (char *)hed->host_addr);
                af = AF_INET6;
        }
        he.h_addrtype = af;
        switch(af) {
        case AF_INET:
                he.h_length = NS_INADDRSZ;
                break;
        case AF_INET6:
                he.h_length = NS_IN6ADDRSZ;
                break;
        default:
                errno = EAFNOSUPPORT;
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                return (-1);
        }
        he.h_name = hed->hostbuf;
        he.h_aliases = hed->host_aliases;
        hed->host_aliases[0] = NULL;
        hed->h_addr_ptrs[0] = (char *)hed->host_addr;
        hed->h_addr_ptrs[1] = NULL;
        he.h_addr_list = hed->h_addr_ptrs;
        if (__copy_hostent(&he, hp, buf, buflen) != 0) {
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                return (-1);
        }
        RES_SET_H_ERRNO(statp, NETDB_SUCCESS);
        return (0);
}

int
gethostbyname_r(const char *name, struct hostent *he, char *buffer,
    size_t buflen, struct hostent **result, int *h_errnop)
{
        res_state statp;

        statp = __res_state();
        if ((statp->options & RES_INIT) == 0 && res_ninit(statp) == -1) {
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                return (-1);
        }
        if (statp->options & RES_USE_INET6) {
                if (fakeaddr(name, AF_INET, he, buffer, buflen, statp) == 0) {
                        *result = he;
                        return (0);
                }
                if (gethostbyname_internal(name, AF_INET6, he, buffer, buflen,
                    result, h_errnop, statp) == 0)
                        return (0);
        }
        return (gethostbyname_internal(name, AF_INET, he, buffer, buflen,
            result, h_errnop, statp));
}

int
gethostbyname2_r(const char *name, int af, struct hostent *he, char *buffer,
    size_t buflen, struct hostent **result, int *h_errnop)
{
        res_state statp;

        statp = __res_state();
        if ((statp->options & RES_INIT) == 0 && res_ninit(statp) == -1) {
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                return (-1);
        }
        return (gethostbyname_internal(name, af, he, buffer, buflen, result,
            h_errnop, statp));
}

int
gethostbyname_internal(const char *name, int af, struct hostent *hp, char *buf,
    size_t buflen, struct hostent **result, int *h_errnop, res_state statp)
{
        const char *cp;
        int rval, ret_errno = 0;
        char abuf[MAXDNAME];

#ifdef NS_CACHING
        static const nss_cache_info cache_info =
                NS_COMMON_CACHE_INFO_INITIALIZER(
                hosts, (void *)nss_lt_name,
                host_id_func, host_marshal_func, host_unmarshal_func);
#endif
        static const ns_dtab dtab[] = {
                NS_FILES_CB(_ht_gethostbyname, NULL)
                { NSSRC_DNS, _dns_gethostbyname, NULL },
                NS_NIS_CB(_nis_gethostbyname, NULL) /* force -DHESIOD */
#ifdef NS_CACHING
                NS_CACHE_CB(&cache_info)
#endif
                { 0 }
        };

        switch (af) {
        case AF_INET:
        case AF_INET6:
                break;
        default:
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                *h_errnop = statp->res_h_errno;
                errno = EAFNOSUPPORT;
                return (-1);
        }

        /*
         * if there aren't any dots, it could be a user-level alias.
         * this is also done in res_query() since we are not the only
         * function that looks up host names.
         */
        if (!strchr(name, '.') &&
            (cp = res_hostalias(statp, name, abuf, sizeof abuf)))
                name = cp;

        if (fakeaddr(name, af, hp, buf, buflen, statp) == 0) {
                *result = hp;
                return (0);
        }

        rval = _nsdispatch((void *)result, dtab, NSDB_HOSTS,
            "gethostbyname2_r", default_src, name, af, hp, buf, buflen,
            &ret_errno, h_errnop);

        if (rval != NS_SUCCESS) {
                errno = ret_errno;
                return ((ret_errno != 0) ? ret_errno : -1);
        }
        return (0);
}

int
gethostbyaddr_r(const void *addr, socklen_t len, int af, struct hostent *hp,
    char *buf, size_t buflen, struct hostent **result, int *h_errnop)
{
        const u_char *uaddr = (const u_char *)addr;
        const struct in6_addr *addr6;
        socklen_t size;
        int rval, ret_errno = 0;
        res_state statp;

#ifdef NS_CACHING
        static const nss_cache_info cache_info =
                NS_COMMON_CACHE_INFO_INITIALIZER(
                hosts, (void *)nss_lt_id,
                host_id_func, host_marshal_func, host_unmarshal_func);
#endif
        static const ns_dtab dtab[] = {
                NS_FILES_CB(_ht_gethostbyaddr, NULL)
                { NSSRC_DNS, _dns_gethostbyaddr, NULL },
                NS_NIS_CB(_nis_gethostbyaddr, NULL) /* force -DHESIOD */
#ifdef NS_CACHING
                NS_CACHE_CB(&cache_info)
#endif
                { 0 }
        };

        statp = __res_state();
        if ((statp->options & RES_INIT) == 0 && res_ninit(statp) == -1) {
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                *h_errnop = statp->res_h_errno;
                return (-1);
        }

        if (af == AF_INET6 && len == NS_IN6ADDRSZ) {
                addr6 = (const struct in6_addr *)addr;
                if (IN6_IS_ADDR_LINKLOCAL(addr6)) {
                        RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
                        *h_errnop = statp->res_h_errno;
                        return (-1);
                }
                if (IN6_IS_ADDR_V4MAPPED(addr6) ||
                    IN6_IS_ADDR_V4COMPAT(addr6)) {
                        /* Unmap. */
                        uaddr += NS_IN6ADDRSZ - NS_INADDRSZ;
                        af = AF_INET;
                        len = NS_INADDRSZ;
                }
        }
        switch (af) {
        case AF_INET:
                size = NS_INADDRSZ;
                break;
        case AF_INET6:
                size = NS_IN6ADDRSZ;
                break;
        default:
                errno = EAFNOSUPPORT;
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                *h_errnop = statp->res_h_errno;
                return (-1);
        }
        if (size != len) {
                errno = EINVAL;
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                *h_errnop = statp->res_h_errno;
                return (-1);
        }

        rval = _nsdispatch((void *)result, dtab, NSDB_HOSTS,
            "gethostbyaddr_r", default_src, uaddr, len, af, hp, buf, buflen,
            &ret_errno, h_errnop);

        if (rval != NS_SUCCESS) {
                errno = ret_errno;
                return ((ret_errno != 0) ? ret_errno : -1);
        }
        return (0);
}

struct hostent *
gethostbyname(const char *name)
{
        struct hostdata *hd;
        struct hostent *rval;
        int ret_h_errno;

        if ((hd = __hostdata_init()) == NULL)
                return (NULL);
        if (gethostbyname_r(name, &hd->host, hd->data, sizeof(hd->data), &rval,
            &ret_h_errno) != 0)
                return (NULL);
        return (rval);
}

struct hostent *
gethostbyname2(const char *name, int af)
{
        struct hostdata *hd;
        struct hostent *rval;
        int ret_h_errno;

        if ((hd = __hostdata_init()) == NULL)
                return (NULL);
        if (gethostbyname2_r(name, af, &hd->host, hd->data, sizeof(hd->data),
            &rval, &ret_h_errno) != 0)
                return (NULL);
        return (rval);
}

struct hostent *
gethostbyaddr(const void *addr, socklen_t len, int af)
{
        struct hostdata *hd;
        struct hostent *rval;
        int ret_h_errno;

        if ((hd = __hostdata_init()) == NULL)
                return (NULL);
        if (gethostbyaddr_r(addr, len, af, &hd->host, hd->data,
            sizeof(hd->data), &rval, &ret_h_errno) != 0)
                return (NULL);
        return (rval);
}

void
sethostent(int stayopen)
{
        struct hostent_data *hed;

        if ((hed = __hostent_data_init()) == NULL)
                return;
        _sethosthtent(stayopen, hed);
        _sethostdnsent(stayopen);
}

void
endhostent(void)
{
        struct hostent_data *hed;

        if ((hed = __hostent_data_init()) == NULL)
                return;
        _endhosthtent(hed);
        _endhostdnsent();
}