/*	$OpenBSD: gethostnamadr_async.c,v 1.49 2023/11/22 13:19:31 florian Exp $	*/
/*
 * Copyright (c) 2012 Eric Faurot <eric@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <netdb.h>

#include <asr.h>
#include <ctype.h>
#include <errno.h>
#include <resolv.h> /* for res_hnok */
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>

#include "asr_private.h"

#define MAXALIASES	35
#define MAXADDRS	35

struct hostent_ext {
	struct hostent	 h;
	char		*aliases[MAXALIASES + 1];
	char		*addrs[MAXADDRS + 1];
	char		*end;
	char		*pos;
};

struct netent_ext {
	struct netent	 n;
	char		*aliases[MAXALIASES + 1];
	char		*end;
	char		*pos;
};

static int gethostnamadr_async_run(struct asr_query *, struct asr_result *);
static struct hostent_ext *hostent_alloc(int);
static int hostent_set_cname(struct hostent_ext *, const char *, int);
static int hostent_add_alias(struct hostent_ext *, const char *, int);
static int hostent_add_addr(struct hostent_ext *, const void *, size_t);
static struct hostent_ext *hostent_from_addr(int, const char *, const char *);
static struct hostent_ext *hostent_file_match(FILE *, int, int, const char *,
    int);
static struct hostent_ext *hostent_from_packet(int, int, char *, size_t);
static void netent_from_hostent(struct asr_result *ar);

struct asr_query *
gethostbyname_async(const char *name, void *asr)
{
	return gethostbyname2_async(name, AF_INET, asr);
}
DEF_WEAK(gethostbyname_async);

struct asr_query *
gethostbyname2_async(const char *name, int af, void *asr)
{
	struct asr_ctx	 *ac;
	struct asr_query *as;

	/* the original segfaults */
	if (name == NULL) {
		errno = EINVAL;
		return (NULL);
	}

	ac = _asr_use_resolver(asr);
	if ((as = _asr_async_new(ac, ASR_GETHOSTBYNAME)) == NULL)
		goto abort; /* errno set */
	as->as_run = gethostnamadr_async_run;

	as->as.hostnamadr.family = af;
	if (af == AF_INET)
		as->as.hostnamadr.addrlen = INADDRSZ;
	else if (af == AF_INET6)
		as->as.hostnamadr.addrlen = IN6ADDRSZ;
	as->as.hostnamadr.name = strdup(name);
	if (as->as.hostnamadr.name == NULL)
		goto abort; /* errno set */

	_asr_ctx_unref(ac);
	return (as);

    abort:
	if (as)
		_asr_async_free(as);
	_asr_ctx_unref(ac);
	return (NULL);
}
DEF_WEAK(gethostbyname2_async);

struct asr_query *
gethostbyaddr_async(const void *addr, socklen_t len, int af, void *asr)
{
	struct asr_ctx	 *ac;
	struct asr_query *as;

	ac = _asr_use_resolver(asr);
	as = _gethostbyaddr_async_ctx(addr, len, af, ac);
	_asr_ctx_unref(ac);

	return (as);
}
DEF_WEAK(gethostbyaddr_async);

struct asr_query *
_gethostbyaddr_async_ctx(const void *addr, socklen_t len, int af,
    struct asr_ctx *ac)
{
	struct asr_query *as;

	if ((as = _asr_async_new(ac, ASR_GETHOSTBYADDR)) == NULL)
		goto abort; /* errno set */
	as->as_run = gethostnamadr_async_run;

	as->as.hostnamadr.family = af;
	as->as.hostnamadr.addrlen = len;
	if (len > 0)
		memmove(as->as.hostnamadr.addr, addr, (len > 16) ? 16 : len);

	return (as);

    abort:
	if (as)
		_asr_async_free(as);
	return (NULL);
}

static int
gethostnamadr_async_run(struct asr_query *as, struct asr_result *ar)
{
	struct hostent_ext	*h;
	int			 r, type, saved_errno;
	FILE			*f;
	char			 name[MAXDNAME], *data, addr[16], *c;

    next:
	switch (as->as_state) {

	case ASR_STATE_INIT:

		if (as->as.hostnamadr.family != AF_INET &&
		    as->as.hostnamadr.family != AF_INET6) {
			ar->ar_h_errno = NETDB_INTERNAL;
			ar->ar_errno = EAFNOSUPPORT;
			async_set_state(as, ASR_STATE_HALT);
			break;
		}

		if ((as->as.hostnamadr.family == AF_INET &&
		     as->as.hostnamadr.addrlen != INADDRSZ) ||
		    (as->as.hostnamadr.family == AF_INET6 &&
		     as->as.hostnamadr.addrlen != IN6ADDRSZ)) {
			ar->ar_h_errno = NETDB_INTERNAL;
			ar->ar_errno = EINVAL;
			async_set_state(as, ASR_STATE_HALT);
			break;
		}

		if (as->as_type == ASR_GETHOSTBYNAME) {

			if (as->as.hostnamadr.name[0] == '\0') {
				ar->ar_h_errno = NO_DATA;
				async_set_state(as, ASR_STATE_HALT);
				break;
			}

			/* Name might be an IP address string */
			for (c = as->as.hostnamadr.name; *c; c++)
				if (!isdigit((unsigned char)*c) &&
				     *c != '.' && *c != ':')
					break;
			if (*c == 0 &&
			    inet_pton(as->as.hostnamadr.family,
			    as->as.hostnamadr.name, addr) == 1) {
				h = hostent_from_addr(as->as.hostnamadr.family,
				    as->as.hostnamadr.name, addr);
				if (h == NULL) {
					ar->ar_errno = errno;
					ar->ar_h_errno = NETDB_INTERNAL;
				}
				else {
					ar->ar_hostent = &h->h;
					ar->ar_h_errno = NETDB_SUCCESS;
				}
				async_set_state(as, ASR_STATE_HALT);
				break;
			}

			if (!hnok_lenient(as->as.hostnamadr.name)) {
				ar->ar_h_errno = NETDB_INTERNAL;
				ar->ar_errno = EINVAL;
				async_set_state(as, ASR_STATE_HALT);
				break;
			}

			/*
			 * If hostname is "localhost" or falls within the
			 * ".localhost." domain, use local address.
			 * RFC 6761, 6.3:
			 * 3. Name resolution APIs and libraries SHOULD
			 * recognize localhost names as special and SHOULD
			 * always return the IP loopback address for address
			 * queries and negative responses for all other query
			 * types.  Name resolution APIs SHOULD NOT send queries
			 * for localhost names to their configured caching DNS
			 * server(s).
			 */

			if (_asr_is_localhost(as->as.hostnamadr.name)) {
				inet_pton(as->as.hostnamadr.family,
				    as->as.hostnamadr.family == AF_INET ?
				    "127.0.0.1" : "::1", addr);
				h = hostent_from_addr(as->as.hostnamadr.family,
				    as->as.hostnamadr.name, addr);
				if (h == NULL) {
					ar->ar_errno = errno;
					ar->ar_h_errno = NETDB_INTERNAL;
				}
				else {
					ar->ar_hostent = &h->h;
					ar->ar_h_errno = NETDB_SUCCESS;
				}
				async_set_state(as, ASR_STATE_HALT);
				break;
			}
		}
		async_set_state(as, ASR_STATE_NEXT_DB);
		break;

	case ASR_STATE_NEXT_DB:

		if (_asr_iter_db(as) == -1) {
			async_set_state(as, ASR_STATE_NOT_FOUND);
			break;
		}

		switch (AS_DB(as)) {

		case ASR_DB_DNS:

			/* Create a subquery to do the DNS lookup */

			if (as->as_type == ASR_GETHOSTBYNAME) {
				type = (as->as.hostnamadr.family == AF_INET) ?
				    T_A : T_AAAA;
				as->as_subq = _res_search_async_ctx(
				    as->as.hostnamadr.name,
				    C_IN, type, as->as_ctx);
			} else {
				_asr_addr_as_fqdn(as->as.hostnamadr.addr,
				    as->as.hostnamadr.family,
				    name, sizeof(name));
				as->as_subq = _res_query_async_ctx(
				    name, C_IN, T_PTR, as->as_ctx);
			}

			if (as->as_subq == NULL) {
				ar->ar_errno = errno;
				ar->ar_h_errno = NETDB_INTERNAL;
				async_set_state(as, ASR_STATE_HALT);
				break;
			}

			async_set_state(as, ASR_STATE_SUBQUERY);
			break;

		case ASR_DB_FILE:

			/* Try to find a match in the host file */

			if ((f = fopen(_PATH_HOSTS, "re")) == NULL)
				break;

			if (as->as_type == ASR_GETHOSTBYNAME)
				data = as->as.hostnamadr.name;
			else
				data = as->as.hostnamadr.addr;

			h = hostent_file_match(f, as->as_type,
			    as->as.hostnamadr.family, data,
			    as->as.hostnamadr.addrlen);
			saved_errno = errno;
			fclose(f);
			errno = saved_errno;

			if (h == NULL) {
				if (errno) {
					ar->ar_errno = errno;
					ar->ar_h_errno = NETDB_INTERNAL;
					async_set_state(as, ASR_STATE_HALT);
				}
				/* otherwise not found */
				break;
			}
			ar->ar_hostent = &h->h;
			ar->ar_h_errno = NETDB_SUCCESS;
			async_set_state(as, ASR_STATE_HALT);
			break;
		}
		break;

	case ASR_STATE_SUBQUERY:

		/* Run the DNS subquery. */

		if ((r = asr_run(as->as_subq, ar)) == ASYNC_COND)
			return (ASYNC_COND);

		/* Done. */
		as->as_subq = NULL;

		/*
		 * We either got no packet or a packet without an answer.
		 * Saveguard the h_errno and use the next DB.
		 */
		if (ar->ar_count == 0) {
			free(ar->ar_data);
			as->as.hostnamadr.subq_h_errno = ar->ar_h_errno;
			async_set_state(as, ASR_STATE_NEXT_DB);
			break;
		}

		/* Read the hostent from the packet. */

		h = hostent_from_packet(as->as_type,
		    as->as.hostnamadr.family, ar->ar_data, ar->ar_datalen);
		free(ar->ar_data);
		if (h == NULL) {
			ar->ar_errno = errno;
			ar->ar_h_errno = NETDB_INTERNAL;
			async_set_state(as, ASR_STATE_HALT);
			break;
		}

		if (as->as_type == ASR_GETHOSTBYADDR) {
			if (hostent_add_addr(h, as->as.hostnamadr.addr,
			    as->as.hostnamadr.addrlen) == -1) {
				free(h);
				ar->ar_errno = errno;
				ar->ar_h_errno = NETDB_INTERNAL;
				async_set_state(as, ASR_STATE_HALT);
				break;
			}
		}

		/*
		 * No valid hostname or address found in the dns packet.
		 * Ignore it.
		 */
		if ((as->as_type == ASR_GETHOSTBYNAME &&
		     h->h.h_addr_list[0] == NULL) ||
		    h->h.h_name == NULL) {
			free(h);
			async_set_state(as, ASR_STATE_NEXT_DB);
			break;
		}

		ar->ar_hostent = &h->h;
		ar->ar_h_errno = NETDB_SUCCESS;
		async_set_state(as, ASR_STATE_HALT);
		break;

	case ASR_STATE_NOT_FOUND:
		ar->ar_errno = 0;
		if (as->as.hostnamadr.subq_h_errno)
			ar->ar_h_errno = as->as.hostnamadr.subq_h_errno;
		else
			ar->ar_h_errno = HOST_NOT_FOUND;
		async_set_state(as, ASR_STATE_HALT);
		break;

	case ASR_STATE_HALT:
		if (ar->ar_h_errno == NETDB_SUCCESS &&
		    as->as_flags & ASYNC_GETNET)
			netent_from_hostent(ar);
		if (ar->ar_h_errno) {
			ar->ar_hostent = NULL;
			ar->ar_netent = NULL;
		} else
			ar->ar_errno = 0;
		return (ASYNC_DONE);

	default:
		ar->ar_errno = EOPNOTSUPP;
		ar->ar_h_errno = NETDB_INTERNAL;
		ar->ar_gai_errno = EAI_SYSTEM;
		async_set_state(as, ASR_STATE_HALT);
		break;
	}
	goto next;
}

/*
 * Create a hostent from a numeric address string.
 */
static struct hostent_ext *
hostent_from_addr(int family, const char *name, const char *addr)
{
	struct	 hostent_ext *h;

	if ((h = hostent_alloc(family)) == NULL)
		return (NULL);
	if (hostent_set_cname(h, name, 0) == -1)
		goto fail;
	if (hostent_add_addr(h, addr, h->h.h_length) == -1)
		goto fail;
	return (h);
fail:
	free(h);
	return (NULL);
}

/*
 * Lookup the first matching entry in the hostfile, either by address or by
 * name depending on reqtype, and build a hostent from the line.
 */
static struct hostent_ext *
hostent_file_match(FILE *f, int reqtype, int family, const char *data,
    int datalen)
{
	char	*tokens[MAXTOKEN], addr[16], buf[BUFSIZ + 1];
	struct	 hostent_ext *h;
	int	 n, i;

	for (;;) {
		n = _asr_parse_namedb_line(f, tokens, MAXTOKEN, buf, sizeof(buf));
		if (n == -1) {
			errno = 0; /* ignore errors reading the file */
			return (NULL);
		}

		/* there must be an address and at least one name */
		if (n < 2)
			continue;

		if (reqtype == ASR_GETHOSTBYNAME) {
			for (i = 1; i < n; i++) {
				if (strcasecmp(data, tokens[i]))
					continue;
				if (inet_pton(family, tokens[0], addr) == 1)
					goto found;
			}
		} else {
			if (inet_pton(family, tokens[0], addr) == 1 &&
			    memcmp(addr, data, datalen) == 0)
				goto found;
		}
	}

found:
	if ((h = hostent_alloc(family)) == NULL)
		return (NULL);
	if (hostent_set_cname(h, tokens[1], 0) == -1)
		goto fail;
	for (i = 2; i < n; i ++)
		if (hostent_add_alias(h, tokens[i], 0) == -1)
			goto fail;
	if (hostent_add_addr(h, addr, h->h.h_length) == -1)
		goto fail;
	return (h);
fail:
	free(h);
	return (NULL);
}

/*
 * Fill the hostent from the given DNS packet.
 */
static struct hostent_ext *
hostent_from_packet(int reqtype, int family, char *pkt, size_t pktlen)
{
	struct hostent_ext	*h;
	struct asr_unpack	 p;
	struct asr_dns_header	 hdr;
	struct asr_dns_query	 q;
	struct asr_dns_rr	 rr;
	char			 dname[MAXDNAME];

	if ((h = hostent_alloc(family)) == NULL)
		return (NULL);

	_asr_unpack_init(&p, pkt, pktlen);
	_asr_unpack_header(&p, &hdr);
	for (; hdr.qdcount; hdr.qdcount--)
		_asr_unpack_query(&p, &q);
	strlcpy(dname, q.q_dname, sizeof(dname));

	for (; hdr.ancount; hdr.ancount--) {
		_asr_unpack_rr(&p, &rr);
		if (rr.rr_class != C_IN)
			continue;
		switch (rr.rr_type) {

		case T_CNAME:
			if (reqtype == ASR_GETHOSTBYNAME) {
				if (hostent_add_alias(h, rr.rr_dname, 1) == -1)
					goto fail;
			} else {
				if (strcasecmp(rr.rr_dname, dname) == 0)
					strlcpy(dname, rr.rr.cname.cname,
					    sizeof(dname));
			}
			break;

		case T_PTR:
			if (reqtype != ASR_GETHOSTBYADDR)
				break;
			if (strcasecmp(rr.rr_dname, dname) != 0)
				continue;
			if (hostent_set_cname(h, rr.rr.ptr.ptrname, 1) == -1)
				hostent_add_alias(h, rr.rr.ptr.ptrname, 1);
			break;

		case T_A:
			if (reqtype != ASR_GETHOSTBYNAME)
				break;
			if (family != AF_INET)
				break;
			if (hostent_set_cname(h, rr.rr_dname, 1) == -1)
				;
			if (hostent_add_addr(h, &rr.rr.in_a.addr, 4) == -1)
				goto fail;
			break;

		case T_AAAA:
			if (reqtype != ASR_GETHOSTBYNAME)
				break;
			if (family != AF_INET6)
				break;
			if (hostent_set_cname(h, rr.rr_dname, 1) == -1)
				;
			if (hostent_add_addr(h, &rr.rr.in_aaaa.addr6, 16) == -1)
				goto fail;
			break;
		}
	}

	return (h);
fail:
	free(h);
	return (NULL);
}

static struct hostent_ext *
hostent_alloc(int family)
{
	struct hostent_ext	*h;
	size_t			alloc;

	alloc = sizeof(*h) + 1024;
	if ((h = calloc(1, alloc)) == NULL)
		return (NULL);

	h->h.h_addrtype = family;
	h->h.h_length = (family == AF_INET) ? 4 : 16;
	h->h.h_aliases = h->aliases;
	h->h.h_addr_list = h->addrs;
	h->pos = (char *)(h) + sizeof(*h);
	h->end = h->pos + 1024;

	return (h);
}

static int
hostent_set_cname(struct hostent_ext *h, const char *name, int isdname)
{
	char	buf[MAXDNAME];
	size_t	n;

	if (h->h.h_name)
		return (-1);

	if (isdname) {
		_asr_strdname(name, buf, sizeof buf);
		buf[strlen(buf) - 1] = '\0';
		if (!res_hnok(buf))
			return (-1);
		name = buf;
	}

	n = strlen(name) + 1;
	if (h->pos + n >= h->end)
		return (-1);

	h->h.h_name = h->pos;
	memmove(h->pos, name, n);
	h->pos += n;
	return (0);
}

static int
hostent_add_alias(struct hostent_ext *h, const char *name, int isdname)
{
	char	buf[MAXDNAME];
	size_t	i, n;

	for (i = 0; i < MAXALIASES; i++)
		if (h->aliases[i] == NULL)
			break;
	if (i == MAXALIASES)
		return (0);

	if (isdname) {
		_asr_strdname(name, buf, sizeof buf);
		buf[strlen(buf)-1] = '\0';
		if (!res_hnok(buf))
			return (-1);
		name = buf;
	}

	n = strlen(name) + 1;
	if (h->pos + n >= h->end)
		return (0);

	h->aliases[i] = h->pos;
	memmove(h->pos, name, n);
	h->pos += n;
	return (0);
}

static int
hostent_add_addr(struct hostent_ext *h, const void *addr, size_t size)
{
	int	i;

	for (i = 0; i < MAXADDRS; i++)
		if (h->addrs[i] == NULL)
			break;
	if (i == MAXADDRS)
		return (0);

	if (h->pos + size >= h->end)
		return (0);

	h->addrs[i] = h->pos;
	memmove(h->pos, addr, size);
	h->pos += size;
	return (0);
}

static void
netent_from_hostent(struct asr_result *ar)
{
	struct in_addr		 *addr;
	struct netent_ext	 *n;
	struct hostent_ext	 *h;
	char			**na, **ha;
	size_t			  sz;

	/* Allocate and initialize the output. */
	if ((n = calloc(1, sizeof(*n) + 1024)) == NULL) {
		ar->ar_h_errno = NETDB_INTERNAL;
		ar->ar_errno = errno;
		goto out;
	}
	n->pos = (char *)(n) + sizeof(*n);
	n->end = n->pos + 1024;
	n->n.n_name = n->pos;
	n->n.n_aliases = n->aliases;

	/* Copy the fixed-size data. */
	h = (struct hostent_ext *)ar->ar_hostent;
	addr = (struct in_addr *)h->h.h_addr;
	n->n.n_net = ntohl(addr->s_addr);
	n->n.n_addrtype = h->h.h_addrtype;

	/* Copy the network name. */
	sz = strlen(h->h.h_name) + 1;
	memcpy(n->pos, h->h.h_name, sz);
	n->pos += sz;

	/*
	 * Copy the aliases.
	 * No overflow check is needed because we are merely copying
	 * a part of the data from a structure of the same size.
	 */
	na = n->aliases;
	for (ha = h->aliases; *ha != NULL; ha++) {
		sz = strlen(*ha) + 1;
		memcpy(n->pos, *ha, sz);
		*na++ = n->pos;
		n->pos += sz;
	}
	*na = NULL;

	/* Handle the return values. */
	ar->ar_netent = &n->n;
out:
	free(ar->ar_hostent);
	ar->ar_hostent = NULL;
}