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 <errno.h>
21 #include <event.h>
22 #include <netdb.h>
23 #include <stdlib.h>
24 #include <stdio.h>
25 #include <string.h>
26 #include <syslog.h>
27 #include <unistd.h>
28 #include <asr.h>
29 
30 #include "log.h"
31 #include "smtp_proc.h"
32 
33 struct dnsbl_session;
34 
35 struct dnsbl_query {
36 	struct asr_query *query;
37 	struct event_asr *event;
38 	struct event timeout;
39 	int resolved;
40 	int blacklist;
41 	struct dnsbl_session *session;
42 };
43 
44 struct dnsbl_session {
45 	uint64_t reqid;
46 	uint64_t token;
47 	int listed;
48 	struct dnsbl_query *query;
49 	RB_ENTRY(dnsbl_session) entry;
50 };
51 
52 RB_HEAD(dnsbl_sessions, dnsbl_session) dnsbl_sessions = RB_INITIALIZER(NULL);
53 RB_PROTOTYPE(dnsbl_sessions, dnsbl_session, entry, dnsbl_session_cmp);
54 
55 static char **blacklists = NULL;
56 static size_t nblacklists = 0;
57 static int markspam = 0;
58 
59 void usage(void);
60 void dnsbl_connect(char *, int, struct timespec *, char *, char *, uint64_t,
61     uint64_t, char *, struct inx_addr *);
62 void dnsbl_dataline(char *, int, struct timespec *, char *, char *, uint64_t,
63     uint64_t, char *);
64 void dnsbl_disconnect(char *, int, struct timespec *, char *, char *, uint64_t);
65 void dnsbl_resolve(struct asr_result *, void *);
66 void dnsbl_timeout(int, short, void *);
67 void dnsbl_session_query_done(struct dnsbl_session *);
68 void dnsbl_session_free(struct dnsbl_session *);
69 int dnsbl_session_cmp(struct dnsbl_session *, struct dnsbl_session *);
70 
71 int
72 main(int argc, char *argv[])
73 {
74 	int ch;
75 	int i;
76 	int debug = 0;
77 
78 	while ((ch = getopt(argc, argv, "d:m")) != -1) {
79 		switch (ch) {
80 		case 'd':
81 			debug = 1;
82 			break;
83 		case 'm':
84 			markspam = 1;
85 			break;
86 		default:
87 			usage();
88 		}
89 	}
90 
91 	log_init(debug, LOG_MAIL);
92 	if (pledge("stdio dns", NULL) == -1)
93 		fatal("pledge");
94 
95 	if ((nblacklists = argc - optind) == 0)
96 		fatalx("No blacklist specified");
97 
98 	if ((blacklists = calloc(nblacklists, sizeof(*blacklists))) == NULL)
99 		fatal(NULL);
100 	for (i = 0; i < nblacklists; i++)
101 		blacklists[i] = argv[optind + i];
102 
103 	smtp_register_filter_connect(dnsbl_connect);
104 	if (markspam)
105 		smtp_register_filter_dataline(dnsbl_dataline);
106 	smtp_in_register_report_disconnect(dnsbl_disconnect);
107 	smtp_run(debug);
108 
109 	return 0;
110 }
111 
112 void
113 dnsbl_connect(char *type, int version, struct timespec *tm, char *direction,
114     char *phase, uint64_t reqid, uint64_t token, char *hostname,
115     struct inx_addr *xaddr)
116 {
117 	struct dnsbl_session *session;
118 	struct timeval timeout = {1, 0};
119 	char query[255];
120 	u_char *addr;
121 	int i, try;
122 
123 	if ((session = calloc(1, sizeof(*session))) == NULL)
124 		fatal(NULL);
125 	if ((session->query = calloc(nblacklists, sizeof(*(session->query))))
126 	    == NULL)
127 		fatal(NULL);
128 	session->reqid = reqid;
129 	session->token = token;
130 	session->listed = -1;
131 	RB_INSERT(dnsbl_sessions, &dnsbl_sessions, session);
132 
133 	if (xaddr->af == AF_INET)
134 		addr = (u_char *)&(xaddr->addr);
135 	else
136 		addr = (u_char *)&(xaddr->addr6);
137 	for (i = 0; i < nblacklists; i++) {
138 		if (xaddr->af == AF_INET) {
139 			if (snprintf(query, sizeof(query), "%u.%u.%u.%u.%s",
140 			    addr[3], addr[2], addr[1], addr[0],
141 			    blacklists[i]) >= sizeof(query))
142 				fatalx("Can't create query, domain too long");
143 		} else if (xaddr->af == AF_INET6) {
144 			if (snprintf(query, sizeof(query), "%hhx.%hhx.%hhx.%hhx"
145 			    ".%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx"
146 			    ".%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx"
147 			    ".%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%s",
148 			    (u_char) (addr[15] & 0xf), (u_char) (addr[15] >> 4),
149 			    (u_char) (addr[14] & 0xf), (u_char) (addr[14] >> 4),
150 			    (u_char) (addr[13] & 0xf), (u_char) (addr[13] >> 4),
151 			    (u_char) (addr[12] & 0xf), (u_char) (addr[12] >> 4),
152 			    (u_char) (addr[11] & 0xf), (u_char) (addr[11] >> 4),
153 			    (u_char) (addr[10] & 0xf), (u_char) (addr[10] >> 4),
154 			    (u_char) (addr[9] & 0xf), (u_char) (addr[9] >> 4),
155 			    (u_char) (addr[8] & 0xf), (u_char) (addr[8] >> 4),
156 			    (u_char) (addr[7] & 0xf), (u_char) (addr[8] >> 4),
157 			    (u_char) (addr[6] & 0xf), (u_char) (addr[7] >> 4),
158 			    (u_char) (addr[5] & 0xf), (u_char) (addr[5] >> 4),
159 			    (u_char) (addr[4] & 0xf), (u_char) (addr[4] >> 4),
160 			    (u_char) (addr[3] & 0xf), (u_char) (addr[3] >> 4),
161 			    (u_char) (addr[2] & 0xf), (u_char) (addr[2] >> 4),
162 			    (u_char) (addr[1] & 0xf), (u_char) (addr[1] >> 4),
163 			    (u_char) (addr[0] & 0xf), (u_char) (addr[0] >> 4),
164 			    blacklists[i]) >= sizeof(query))
165 				fatalx( "Can't create query, domain too long");
166 		} else
167 			fatalx("Invalid address family received");
168 
169 		session->query[i].query = gethostbyname_async(query, NULL);
170 		session->query[i].event = event_asr_run(session->query[i].query,
171 		    dnsbl_resolve, &(session->query[i]));
172 		session->query[i].blacklist = i;
173 		session->query[i].session = session;
174 		evtimer_set(&(session->query[i].timeout), dnsbl_timeout,
175 		    &(session->query[i]));
176 		evtimer_add(&(session->query[i].timeout), &timeout);
177 	}
178 }
179 
180 void
181 dnsbl_resolve(struct asr_result *result, void *arg)
182 {
183 	struct dnsbl_query *query = arg;
184 	struct dnsbl_session *session = query->session;
185 	int i, blacklist;
186 
187 	query->resolved = 1;
188 	query->event = NULL;
189 	query->query = NULL;
190 	evtimer_del(&(query->timeout));
191 	if (result->ar_hostent != NULL) {
192 		if (!markspam) {
193 			smtp_filter_disconnect(session->reqid, session->token,
194 			    "Listed at %s", blacklists[query->blacklist]);
195 			dnsbl_session_free(session);
196 		} else {
197 			dnsbl_session_query_done(session);
198 			session->listed = query->blacklist;
199 			smtp_filter_proceed(session->reqid, session->token);
200 		}
201 		return;
202 	}
203 	if (result->ar_h_errno != HOST_NOT_FOUND) {
204 		smtp_filter_disconnect(session->reqid, session->token,
205 		    "DNS error on %s", blacklists[query->blacklist]);
206 		dnsbl_session_free(session);
207 		return;
208 	}
209 
210 	for (i = 0; i < nblacklists; i++) {
211 		if (!session->query[i].resolved)
212 			return;
213 	}
214 	smtp_filter_proceed(session->reqid, session->token);
215 	if (!markspam)
216 		dnsbl_session_free(session);
217 }
218 
219 void
220 dnsbl_timeout(int fd, short event, void *arg)
221 {
222 	struct dnsbl_query *query = arg;
223 	struct dnsbl_session *session = query->session;
224 
225 	smtp_filter_disconnect(session->reqid, session->token,
226 	    "DNS timeout on %s", blacklists[query->blacklist]);
227 	dnsbl_session_free(session);
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_dataline(char *type, int version, struct timespec *tm, char *direction,
243     char *phase, uint64_t reqid, uint64_t token, char *line)
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 		smtp_filter_dataline(reqid, token, "X-Spam: yes");
252 		smtp_filter_dataline(reqid, token, "X-Spam-DNSBL: Listed at %s",
253 		    blacklists[session->listed]);
254 		session->listed = -1;
255 	}
256 	smtp_filter_dataline(reqid, token, "%s", line);
257 }
258 
259 void
260 dnsbl_session_query_done(struct dnsbl_session *session)
261 {
262 	int i;
263 
264 	for (i = 0; i < nblacklists; i++) {
265 		if (!session->query[i].resolved) {
266 			event_asr_abort(session->query[i].event);
267 			evtimer_del(&(session->query[i].timeout));
268 		}
269 	}
270 }
271 
272 void
273 dnsbl_session_free(struct dnsbl_session *session)
274 {
275 	RB_REMOVE(dnsbl_sessions, &dnsbl_sessions, session);
276 	dnsbl_session_query_done(session);
277 	free(session->query);
278 	free(session);
279 }
280 
281 int
282 dnsbl_session_cmp(struct dnsbl_session *s1, struct dnsbl_session *s2)
283 {
284 	return (s1->reqid < s2->reqid ? -1 : s1->reqid > s2->reqid);
285 }
286 
287 __dead void
288 usage(void)
289 {
290 	fprintf(stderr, "usage: %s [-m] blacklist [...]\n",
291 	    getprogname());
292 	exit(1);
293 }
294 
295 RB_GENERATE(dnsbl_sessions, dnsbl_session, entry, dnsbl_session_cmp);