1 /*
2  * Copyright (c) 2019 Martijn van Duren <martijn@openbsd.org>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 #include <sys/tree.h>
17 #include <sys/types.h>
18 #include <sys/socket.h>
19 
20 #include <arpa/inet.h>
21 #include <errno.h>
22 #include <event.h>
23 #include <netdb.h>
24 #include <stdlib.h>
25 #include <stdio.h>
26 #include <string.h>
27 #include <syslog.h>
28 #include <unistd.h>
29 #include <asr.h>
30 
31 #include "log.h"
32 #include "smtp_proc.h"
33 
34 struct dnsbl_session;
35 
36 struct dnsbl_query {
37 	struct asr_query *query;
38 	struct event_asr *event;
39 	struct event timeout;
40 	int resolved;
41 	int blacklist;
42 	struct dnsbl_session *session;
43 };
44 
45 struct dnsbl_session {
46 	uint64_t reqid;
47 	uint64_t token;
48 	char addr[INET6_ADDRSTRLEN];
49 	int listed;
50 	struct dnsbl_query *query;
51 	RB_ENTRY(dnsbl_session) entry;
52 };
53 
54 RB_HEAD(dnsbl_sessions, dnsbl_session) dnsbl_sessions = RB_INITIALIZER(NULL);
55 RB_PROTOTYPE(dnsbl_sessions, dnsbl_session, entry, dnsbl_session_cmp);
56 
57 static char **blacklists = NULL;
58 static size_t nblacklists = 0;
59 static int markspam = 0;
60 
61 void usage(void);
62 void dnsbl_connect(char *, int, struct timespec *, char *, char *, uint64_t,
63     uint64_t, char *, struct inx_addr *);
64 void dnsbl_dataline(char *, int, struct timespec *, char *, char *, uint64_t,
65     uint64_t, char *);
66 void dnsbl_disconnect(char *, int, struct timespec *, char *, char *, uint64_t);
67 void dnsbl_resolve(struct asr_result *, void *);
68 void dnsbl_timeout(int, short, void *);
69 void dnsbl_session_query_done(struct dnsbl_session *);
70 void dnsbl_session_free(struct dnsbl_session *);
71 int dnsbl_session_cmp(struct dnsbl_session *, struct dnsbl_session *);
72 
73 int
74 main(int argc, char *argv[])
75 {
76 	int ch;
77 	int i;
78 	int debug = 0;
79 
80 	while ((ch = getopt(argc, argv, "dm")) != -1) {
81 		switch (ch) {
82 		case 'd':
83 			debug = 1;
84 			break;
85 		case 'm':
86 			markspam = 1;
87 			break;
88 		default:
89 			usage();
90 		}
91 	}
92 
93 	log_init(debug, LOG_MAIL);
94 	if (pledge("stdio dns", NULL) == -1)
95 		fatal("pledge");
96 
97 	if ((nblacklists = argc - optind) == 0)
98 		fatalx("No blacklist specified");
99 
100 	if ((blacklists = calloc(nblacklists, sizeof(*blacklists))) == NULL)
101 		fatal(NULL);
102 	for (i = 0; i < nblacklists; i++)
103 		blacklists[i] = argv[optind + i];
104 
105 	smtp_register_filter_connect(dnsbl_connect);
106 	if (markspam)
107 		smtp_register_filter_dataline(dnsbl_dataline);
108 	smtp_in_register_report_disconnect(dnsbl_disconnect);
109 	smtp_run(debug);
110 
111 	return 0;
112 }
113 
114 void
115 dnsbl_connect(char *type, int version, struct timespec *tm, char *direction,
116     char *phase, uint64_t reqid, uint64_t token, char *hostname,
117     struct inx_addr *xaddr)
118 {
119 	struct dnsbl_session *session;
120 	struct timeval timeout = {1, 0};
121 	char query[255];
122 	u_char *addr;
123 	int i, try;
124 
125 	if ((session = calloc(1, sizeof(*session))) == NULL)
126 		fatal(NULL);
127 	if ((session->query = calloc(nblacklists, sizeof(*(session->query))))
128 	    == NULL)
129 		fatal(NULL);
130 	session->reqid = reqid;
131 	session->token = token;
132 	session->listed = -1;
133 	if (inet_ntop(xaddr->af, xaddr->af == AF_INET ?
134 	    (void *)&(xaddr->addr) : (void *)&(xaddr->addr6), session->addr,
135 	    sizeof(session->addr)) == NULL)
136 		fatal("inet_ntop");
137 
138 	RB_INSERT(dnsbl_sessions, &dnsbl_sessions, session);
139 
140 	if (xaddr->af == AF_INET)
141 		addr = (u_char *)&(xaddr->addr);
142 	else
143 		addr = (u_char *)&(xaddr->addr6);
144 	for (i = 0; i < nblacklists; i++) {
145 		if (xaddr->af == AF_INET) {
146 			if (snprintf(query, sizeof(query), "%u.%u.%u.%u.%s",
147 			    addr[3], addr[2], addr[1], addr[0],
148 			    blacklists[i]) >= sizeof(query))
149 				fatalx("Can't create query, domain too long");
150 		} else if (xaddr->af == AF_INET6) {
151 			if (snprintf(query, sizeof(query), "%hhx.%hhx.%hhx.%hhx"
152 			    ".%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx"
153 			    ".%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx"
154 			    ".%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%s",
155 			    (u_char) (addr[15] & 0xf), (u_char) (addr[15] >> 4),
156 			    (u_char) (addr[14] & 0xf), (u_char) (addr[14] >> 4),
157 			    (u_char) (addr[13] & 0xf), (u_char) (addr[13] >> 4),
158 			    (u_char) (addr[12] & 0xf), (u_char) (addr[12] >> 4),
159 			    (u_char) (addr[11] & 0xf), (u_char) (addr[11] >> 4),
160 			    (u_char) (addr[10] & 0xf), (u_char) (addr[10] >> 4),
161 			    (u_char) (addr[9] & 0xf), (u_char) (addr[9] >> 4),
162 			    (u_char) (addr[8] & 0xf), (u_char) (addr[8] >> 4),
163 			    (u_char) (addr[7] & 0xf), (u_char) (addr[8] >> 4),
164 			    (u_char) (addr[6] & 0xf), (u_char) (addr[7] >> 4),
165 			    (u_char) (addr[5] & 0xf), (u_char) (addr[5] >> 4),
166 			    (u_char) (addr[4] & 0xf), (u_char) (addr[4] >> 4),
167 			    (u_char) (addr[3] & 0xf), (u_char) (addr[3] >> 4),
168 			    (u_char) (addr[2] & 0xf), (u_char) (addr[2] >> 4),
169 			    (u_char) (addr[1] & 0xf), (u_char) (addr[1] >> 4),
170 			    (u_char) (addr[0] & 0xf), (u_char) (addr[0] >> 4),
171 			    blacklists[i]) >= sizeof(query))
172 				fatalx( "Can't create query, domain too long");
173 		} else
174 			fatalx("Invalid address family received");
175 
176 		session->query[i].query = gethostbyname_async(query, NULL);
177 		session->query[i].event = event_asr_run(session->query[i].query,
178 		    dnsbl_resolve, &(session->query[i]));
179 		session->query[i].blacklist = i;
180 		session->query[i].session = session;
181 		evtimer_set(&(session->query[i].timeout), dnsbl_timeout,
182 		    &(session->query[i]));
183 		evtimer_add(&(session->query[i].timeout), &timeout);
184 	}
185 }
186 
187 void
188 dnsbl_resolve(struct asr_result *result, void *arg)
189 {
190 	struct dnsbl_query *query = arg;
191 	struct dnsbl_session *session = query->session;
192 	int i, blacklist;
193 
194 	query->resolved = 1;
195 	query->event = NULL;
196 	query->query = NULL;
197 	evtimer_del(&(query->timeout));
198 	if (result->ar_hostent != NULL) {
199 		if (!markspam) {
200 			smtp_filter_disconnect(session->reqid, session->token,
201 			    "Listed at %s", blacklists[query->blacklist]);
202 			log_info("Rejected %s: listed at %s", session->addr,
203 			    blacklists[query->blacklist]);
204 			dnsbl_session_free(session);
205 		} else {
206 			dnsbl_session_query_done(session);
207 			session->listed = query->blacklist;
208 			smtp_filter_proceed(session->reqid, session->token);
209 			log_info("Marked as spam %s: listed at %s", session->addr,
210 			    blacklists[query->blacklist]);
211 		}
212 		return;
213 	}
214 	if (result->ar_h_errno != HOST_NOT_FOUND) {
215 		smtp_filter_disconnect(session->reqid, session->token,
216 		    "DNS error on %s", blacklists[query->blacklist]);
217 		dnsbl_session_free(session);
218 		return;
219 	}
220 
221 	for (i = 0; i < nblacklists; i++) {
222 		if (!session->query[i].resolved)
223 			return;
224 	}
225 	smtp_filter_proceed(session->reqid, session->token);
226 	log_info("%s not listed", session->addr);
227 	if (!markspam)
228 		dnsbl_session_free(session);
229 }
230 
231 void
232 dnsbl_timeout(int fd, short event, void *arg)
233 {
234 	struct dnsbl_query *query = arg;
235 	struct dnsbl_session *session = query->session;
236 
237 	smtp_filter_disconnect(session->reqid, session->token,
238 	    "DNS timeout on %s", blacklists[query->blacklist]);
239 	dnsbl_session_free(session);
240 }
241 
242 void
243 dnsbl_disconnect(char *type, int version, struct timespec *tm, char *direction,
244     char *phase, uint64_t reqid)
245 {
246 	struct dnsbl_session *session, search;
247 
248 	search.reqid = reqid;
249 	if ((session = RB_FIND(dnsbl_sessions, &dnsbl_sessions, &search)) != NULL)
250 		dnsbl_session_free(session);
251 }
252 
253 void
254 dnsbl_dataline(char *type, int version, struct timespec *tm, char *direction,
255     char *phase, uint64_t reqid, uint64_t token, char *line)
256 {
257 	struct dnsbl_session *session, search;
258 
259 	search.reqid = reqid;
260 	session = RB_FIND(dnsbl_sessions, &dnsbl_sessions, &search);
261 
262 	if (session->listed != -1) {
263 		smtp_filter_dataline(reqid, token, "X-Spam: yes");
264 		smtp_filter_dataline(reqid, token, "X-Spam-DNSBL: Listed at %s",
265 		    blacklists[session->listed]);
266 		session->listed = -1;
267 	}
268 	smtp_filter_dataline(reqid, token, "%s", line);
269 }
270 
271 void
272 dnsbl_session_query_done(struct dnsbl_session *session)
273 {
274 	int i;
275 
276 	for (i = 0; i < nblacklists; i++) {
277 		if (!session->query[i].resolved) {
278 			event_asr_abort(session->query[i].event);
279 			evtimer_del(&(session->query[i].timeout));
280 		}
281 	}
282 }
283 
284 void
285 dnsbl_session_free(struct dnsbl_session *session)
286 {
287 	RB_REMOVE(dnsbl_sessions, &dnsbl_sessions, session);
288 	dnsbl_session_query_done(session);
289 	free(session->query);
290 	free(session);
291 }
292 
293 int
294 dnsbl_session_cmp(struct dnsbl_session *s1, struct dnsbl_session *s2)
295 {
296 	return (s1->reqid < s2->reqid ? -1 : s1->reqid > s2->reqid);
297 }
298 
299 __dead void
300 usage(void)
301 {
302 	fprintf(stderr, "usage: %s [-m] blacklist [...]\n",
303 	    getprogname());
304 	exit(1);
305 }
306 
307 RB_GENERATE(dnsbl_sessions, dnsbl_session, entry, dnsbl_session_cmp);