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 <inttypes.h>
24 #include <netdb.h>
25 #include <stdlib.h>
26 #include <stdio.h>
27 #include <string.h>
28 #include <syslog.h>
29 #include <unistd.h>
30 #include <asr.h>
31 
32 #include "log.h"
33 #include "smtp_proc.h"
34 
35 struct dnsbl_session;
36 
37 struct dnsbl_query {
38 	struct asr_query *query;
39 	struct event_asr *event;
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 	int set_header;
51 	int logged_mark;
52 	struct dnsbl_query *query;
53 	RB_ENTRY(dnsbl_session) entry;
54 };
55 
56 RB_HEAD(dnsbl_sessions, dnsbl_session) dnsbl_sessions = RB_INITIALIZER(NULL);
57 RB_PROTOTYPE(dnsbl_sessions, dnsbl_session, entry, dnsbl_session_cmp);
58 
59 static char **blacklists = NULL;
60 static size_t nblacklists = 0;
61 static int markspam = 0;
62 
63 void usage(void);
64 void dnsbl_connect(char *, int, struct timespec *, char *, char *, uint64_t,
65     uint64_t, char *, struct inx_addr *);
66 void dnsbl_data(char *, int, struct timespec *, char *, char *, uint64_t,
67     uint64_t);
68 void dnsbl_dataline(char *, int, struct timespec *, char *, char *, uint64_t,
69     uint64_t, char *);
70 void dnsbl_disconnect(char *, int, struct timespec *, char *, char *, uint64_t);
71 void dnsbl_resolve(struct asr_result *, void *);
72 void dnsbl_session_query_done(struct dnsbl_session *);
73 void dnsbl_session_free(struct dnsbl_session *);
74 int dnsbl_session_cmp(struct dnsbl_session *, struct dnsbl_session *);
75 
76 int
77 main(int argc, char *argv[])
78 {
79 	int ch;
80 	int i;
81 	int debug = 0;
82 
83 	while ((ch = getopt(argc, argv, "dm")) != -1) {
84 		switch (ch) {
85 		case 'd':
86 			debug = 1;
87 			break;
88 		case 'm':
89 			markspam = 1;
90 			break;
91 		default:
92 			usage();
93 		}
94 	}
95 
96 	log_init(debug, LOG_MAIL);
97 	if (pledge("stdio dns", NULL) == -1)
98 		fatal("pledge");
99 
100 	if ((nblacklists = argc - optind) == 0)
101 		fatalx("No blacklist specified");
102 
103 	if ((blacklists = calloc(nblacklists, sizeof(*blacklists))) == NULL)
104 		fatal(NULL);
105 	for (i = 0; i < nblacklists; i++)
106 		blacklists[i] = argv[optind + i];
107 
108 	smtp_register_filter_connect(dnsbl_connect);
109 	if (markspam) {
110 		smtp_register_filter_data(dnsbl_data);
111 		smtp_register_filter_dataline(dnsbl_dataline);
112 	}
113 	smtp_in_register_report_disconnect(dnsbl_disconnect);
114 	smtp_run(debug);
115 
116 	return 0;
117 }
118 
119 void
120 dnsbl_connect(char *type, int version, struct timespec *tm, char *direction,
121     char *phase, uint64_t reqid, uint64_t token, char *hostname,
122     struct inx_addr *xaddr)
123 {
124 	struct dnsbl_session *session;
125 	char query[255];
126 	u_char *addr;
127 	int i, try;
128 
129 	if ((session = calloc(1, sizeof(*session))) == NULL)
130 		fatal(NULL);
131 	if ((session->query = calloc(nblacklists, sizeof(*(session->query))))
132 	    == NULL)
133 		fatal(NULL);
134 	session->reqid = reqid;
135 	session->token = token;
136 	session->listed = -1;
137 	session->set_header = 0;
138 	session->logged_mark = 0;
139 	if (inet_ntop(xaddr->af, xaddr->af == AF_INET ?
140 	    (void *)&(xaddr->addr) : (void *)&(xaddr->addr6), session->addr,
141 	    sizeof(session->addr)) == NULL)
142 		fatal("inet_ntop");
143 
144 	RB_INSERT(dnsbl_sessions, &dnsbl_sessions, session);
145 
146 	if (xaddr->af == AF_INET)
147 		addr = (u_char *)&(xaddr->addr);
148 	else
149 		addr = (u_char *)&(xaddr->addr6);
150 	for (i = 0; i < nblacklists; i++) {
151 		if (xaddr->af == AF_INET) {
152 			if (snprintf(query, sizeof(query), "%u.%u.%u.%u.%s",
153 			    addr[3], addr[2], addr[1], addr[0],
154 			    blacklists[i]) >= sizeof(query))
155 				fatalx("Can't create query, domain too long");
156 		} else if (xaddr->af == AF_INET6) {
157 			if (snprintf(query, sizeof(query), "%hhx.%hhx.%hhx.%hhx"
158 			    ".%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx"
159 			    ".%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx"
160 			    ".%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%s",
161 			    (u_char) (addr[15] & 0xf), (u_char) (addr[15] >> 4),
162 			    (u_char) (addr[14] & 0xf), (u_char) (addr[14] >> 4),
163 			    (u_char) (addr[13] & 0xf), (u_char) (addr[13] >> 4),
164 			    (u_char) (addr[12] & 0xf), (u_char) (addr[12] >> 4),
165 			    (u_char) (addr[11] & 0xf), (u_char) (addr[11] >> 4),
166 			    (u_char) (addr[10] & 0xf), (u_char) (addr[10] >> 4),
167 			    (u_char) (addr[9] & 0xf), (u_char) (addr[9] >> 4),
168 			    (u_char) (addr[8] & 0xf), (u_char) (addr[8] >> 4),
169 			    (u_char) (addr[7] & 0xf), (u_char) (addr[8] >> 4),
170 			    (u_char) (addr[6] & 0xf), (u_char) (addr[7] >> 4),
171 			    (u_char) (addr[5] & 0xf), (u_char) (addr[5] >> 4),
172 			    (u_char) (addr[4] & 0xf), (u_char) (addr[4] >> 4),
173 			    (u_char) (addr[3] & 0xf), (u_char) (addr[3] >> 4),
174 			    (u_char) (addr[2] & 0xf), (u_char) (addr[2] >> 4),
175 			    (u_char) (addr[1] & 0xf), (u_char) (addr[1] >> 4),
176 			    (u_char) (addr[0] & 0xf), (u_char) (addr[0] >> 4),
177 			    blacklists[i]) >= sizeof(query))
178 				fatalx( "Can't create query, domain too long");
179 		} else
180 			fatalx("Invalid address family received");
181 
182 		session->query[i].query = gethostbyname_async(query, NULL);
183 		session->query[i].event = event_asr_run(session->query[i].query,
184 		    dnsbl_resolve, &(session->query[i]));
185 		session->query[i].blacklist = i;
186 		session->query[i].session = session;
187 	}
188 }
189 
190 void
191 dnsbl_resolve(struct asr_result *result, void *arg)
192 {
193 	struct dnsbl_query *query = arg;
194 	struct dnsbl_session *session = query->session;
195 	int i, blacklist;
196 
197 	query->resolved = 1;
198 	query->event = NULL;
199 	query->query = NULL;
200 	if (result->ar_hostent != NULL) {
201 		if (!markspam) {
202 			smtp_filter_disconnect(session->reqid, session->token,
203 			    "Listed at %s", blacklists[query->blacklist]);
204 			log_info("%016"PRIx64" listed at %s: rejected",
205 			    session->reqid, blacklists[query->blacklist]);
206 			dnsbl_session_free(session);
207 		} else {
208 			dnsbl_session_query_done(session);
209 			session->listed = query->blacklist;
210 			smtp_filter_proceed(session->reqid, session->token);
211 			/* Delay logging until we have a message */
212 		}
213 		return;
214 	}
215 	if (result->ar_h_errno != HOST_NOT_FOUND) {
216 		smtp_filter_disconnect(session->reqid, session->token,
217 		    "DNS error on %s", blacklists[query->blacklist]);
218 		dnsbl_session_free(session);
219 		return;
220 	}
221 
222 	for (i = 0; i < nblacklists; i++) {
223 		if (!session->query[i].resolved)
224 			return;
225 	}
226 	smtp_filter_proceed(session->reqid, session->token);
227 	log_info("%016"PRIx64" not listed", session->reqid);
228 }
229 
230 void
231 dnsbl_disconnect(char *type, int version, struct timespec *tm, char *direction,
232     char *phase, uint64_t reqid)
233 {
234 	struct dnsbl_session *session, search;
235 
236 	search.reqid = reqid;
237 	if ((session = RB_FIND(dnsbl_sessions, &dnsbl_sessions, &search)) != NULL)
238 		dnsbl_session_free(session);
239 }
240 
241 void
242 dnsbl_data(char *type, int version, struct timespec *tm, char *direction,
243     char *phase, uint64_t reqid, uint64_t token)
244 {
245 	struct dnsbl_session *session, search;
246 
247 	search.reqid = reqid;
248 	session = RB_FIND(dnsbl_sessions, &dnsbl_sessions, &search);
249 
250 	if (session->listed != -1) {
251 		if (!session->logged_mark) {
252 			log_info("%016"PRIx64" listed at %s: Marking as spam",
253 			    session->reqid, blacklists[session->listed]);
254 			session->logged_mark = 1;
255 		}
256 		session->set_header = 1;
257 	}
258 	smtp_filter_proceed(reqid, token);
259 }
260 
261 void
262 dnsbl_dataline(char *type, int version, struct timespec *tm, char *direction,
263     char *phase, uint64_t reqid, uint64_t token, char *line)
264 {
265 	struct dnsbl_session *session, search;
266 
267 	search.reqid = reqid;
268 	session = RB_FIND(dnsbl_sessions, &dnsbl_sessions, &search);
269 
270 	if (session->set_header) {
271 		smtp_filter_dataline(reqid, token, "X-Spam: yes");
272 		smtp_filter_dataline(reqid, token, "X-Spam-DNSBL: Listed at %s",
273 		    blacklists[session->listed]);
274 		session->set_header = 0;
275 		
276 	}
277 	smtp_filter_dataline(reqid, token, "%s", line);
278 }
279 
280 void
281 dnsbl_session_query_done(struct dnsbl_session *session)
282 {
283 	int i;
284 
285 	for (i = 0; i < nblacklists; i++) {
286 		if (!session->query[i].resolved) {
287 			event_asr_abort(session->query[i].event);
288 			session->query[i].resolved = 1;
289 		}
290 	}
291 }
292 
293 void
294 dnsbl_session_free(struct dnsbl_session *session)
295 {
296 	RB_REMOVE(dnsbl_sessions, &dnsbl_sessions, session);
297 	dnsbl_session_query_done(session);
298 	free(session->query);
299 	free(session);
300 }
301 
302 int
303 dnsbl_session_cmp(struct dnsbl_session *s1, struct dnsbl_session *s2)
304 {
305 	return (s1->reqid < s2->reqid ? -1 : s1->reqid > s2->reqid);
306 }
307 
308 __dead void
309 usage(void)
310 {
311 	fprintf(stderr, "usage: %s [-m] blacklist [...]\n",
312 	    getprogname());
313 	exit(1);
314 }
315 
316 RB_GENERATE(dnsbl_sessions, dnsbl_session, entry, dnsbl_session_cmp);