1/*	$Id: dnsproc.c,v 1.12 2021/12/13 13:30:39 jca Exp $ */
2/*
3 * Copyright (c) 2016 Kristaps Dzonsons <kristaps@bsd.lv>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18#include <sys/socket.h>
19#include <arpa/inet.h>
20
21#include <err.h>
22#include <netdb.h>
23#include <stdio.h>
24#include <stdlib.h>
25#include <string.h>
26#include <unistd.h>
27
28#include "extern.h"
29
30struct	addr {
31	int	 family; /* 4 for PF_INET, 6 for PF_INET6 */
32	char	 ip[INET6_ADDRSTRLEN];
33};
34
35/*
36 * This is a modified version of host_dns in config.c of OpenBSD's ntpd.
37 */
38/*
39 * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
40 *
41 * Permission to use, copy, modify, and distribute this software for any
42 * purpose with or without fee is hereby granted, provided that the above
43 * copyright notice and this permission notice appear in all copies.
44 *
45 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
46 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
47 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
48 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
49 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
50 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
51 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
52 */
53static ssize_t
54host_dns(const char *s, struct addr *vec)
55{
56	struct addrinfo		 hints, *res0, *res;
57	int			 error;
58	ssize_t			 vecsz;
59	struct sockaddr		*sa;
60
61	memset(&hints, 0, sizeof(hints));
62	hints.ai_family = PF_UNSPEC;
63	hints.ai_socktype = SOCK_DGRAM; /* DUMMY */
64	hints.ai_flags = AI_ADDRCONFIG;
65
66	error = getaddrinfo(s, NULL, &hints, &res0);
67
68	if (error == EAI_AGAIN ||
69		/* FIXME */
70#ifndef __FreeBSD__
71	    error == EAI_NODATA ||
72#endif
73	    error == EAI_NONAME)
74		return 0;
75
76	if (error) {
77		warnx("%s: parse error: %s",
78		    s, gai_strerror(error));
79		return -1;
80	}
81
82	for (vecsz = 0, res = res0;
83	    res != NULL && vecsz < MAX_SERVERS_DNS;
84	    res = res->ai_next) {
85		if (res->ai_family != AF_INET &&
86		    res->ai_family != AF_INET6)
87			continue;
88
89		sa = res->ai_addr;
90
91		if (res->ai_family == AF_INET) {
92			vec[vecsz].family = 4;
93			inet_ntop(AF_INET,
94			    &(((struct sockaddr_in *)sa)->sin_addr),
95				vec[vecsz].ip, INET6_ADDRSTRLEN);
96		} else {
97			vec[vecsz].family = 6;
98			inet_ntop(AF_INET6,
99			    &(((struct sockaddr_in6 *)sa)->sin6_addr),
100			    vec[vecsz].ip, INET6_ADDRSTRLEN);
101		}
102
103		dodbg("%s: DNS: %s", s, vec[vecsz].ip);
104		vecsz++;
105	}
106
107	freeaddrinfo(res0);
108	return vecsz;
109}
110
111int
112dnsproc(int nfd)
113{
114	char		*look = NULL, *last = NULL;
115	struct addr	 v[MAX_SERVERS_DNS];
116	int		 rc = 0, cc;
117	long		 lval;
118	ssize_t		 vsz = 0;
119	size_t		 i;
120	enum dnsop	 op;
121
122	if (pledge("stdio dns", NULL) == -1) {
123		warn("pledge");
124		goto out;
125	}
126
127	/*
128	 * This is simple: just loop on a request operation, and each
129	 * time we write back zero or more entries.
130	 * Also do a simple trick and cache the last lookup.
131	 */
132
133	for (;;) {
134		op = DNS__MAX;
135		if ((lval = readop(nfd, COMM_DNS)) == 0)
136			op = DNS_STOP;
137		else if (lval == DNS_LOOKUP)
138			op = lval;
139
140		if (op == DNS__MAX) {
141			warnx("unknown operation from netproc");
142			goto out;
143		} else if (op == DNS_STOP)
144			break;
145
146		if ((look = readstr(nfd, COMM_DNSQ)) == NULL)
147			goto out;
148
149		/*
150		 * Check if we're asked to repeat the lookup.
151		 * If not, request it from host_dns().
152		 */
153
154		if (last == NULL || strcmp(look, last)) {
155			if ((vsz = host_dns(look, v)) < 0)
156				goto out;
157
158			free(last);
159			last = look;
160			look = NULL;
161		} else {
162			free(look);
163			look = NULL;
164		}
165
166		if ((cc = writeop(nfd, COMM_DNSLEN, vsz)) == 0)
167			break;
168		else if (cc < 0)
169			goto out;
170		for (i = 0; i < (size_t)vsz; i++) {
171			if (writeop(nfd, COMM_DNSF, v[i].family) <= 0)
172				goto out;
173			if (writestr(nfd, COMM_DNSA, v[i].ip) <= 0)
174				goto out;
175		}
176	}
177
178	rc = 1;
179out:
180	close(nfd);
181	free(look);
182	free(last);
183	return rc;
184}
185