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/types.h>
17 #include <sys/socket.h>
18 
19 #include <arpa/inet.h>
20 #include <errno.h>
21 #include <event.h>
22 #include <inttypes.h>
23 #include <netdb.h>
24 #include <stdlib.h>
25 #include <stdarg.h>
26 #include <stdio.h>
27 #include <string.h>
28 #include <syslog.h>
29 #include <unistd.h>
30 #include <asr.h>
31 
32 #include "opensmtpd.h"
33 
34 struct dnsbl_session;
35 
36 struct dnsbl_query {
37 	struct event_asr *event;
38 	int resolved;
39 	int blacklist;
40 	struct dnsbl_session *session;
41 };
42 
43 struct dnsbl_session {
44 	int listed;
45 	int set_header;
46 	int logged_mark;
47 	struct dnsbl_query *query;
48 	struct osmtpd_ctx *ctx;
49 };
50 
51 static char **blacklists = NULL;
52 static size_t nblacklists = 0;
53 static int markspam = 0;
54 static int verbose = 0;
55 
56 void usage(void);
57 void dnsbl_connect(struct osmtpd_ctx *, const char *,
58     struct sockaddr_storage *);
59 void dnsbl_begin(struct osmtpd_ctx *, uint32_t);
60 void dnsbl_dataline(struct osmtpd_ctx *, const char *);
61 void dnsbl_resolve(struct asr_result *, void *);
62 void dnsbl_session_query_done(struct dnsbl_session *);
63 void *dnsbl_session_new(struct osmtpd_ctx *);
64 void dnsbl_session_free(struct osmtpd_ctx *, void *);
65 
66 int
67 main(int argc, char *argv[])
68 {
69 	int ch;
70 	size_t i;
71 
72 	while ((ch = getopt(argc, argv, "mv")) != -1) {
73 		switch (ch) {
74 		case 'm':
75 			markspam = 1;
76 			break;
77 		case 'v':
78 			verbose = 1;
79 			break;
80 		default:
81 			usage();
82 		}
83 	}
84 
85 	if (pledge("stdio dns", NULL) == -1)
86 		osmtpd_err(1, "pledge");
87 
88 	if ((nblacklists = argc - optind) == 0)
89 		osmtpd_errx(1, "No blacklist specified");
90 
91 	if ((blacklists = calloc(nblacklists, sizeof(*blacklists))) == NULL)
92 		osmtpd_err(1, "malloc");
93 	for (i = 0; i < nblacklists; i++)
94 		blacklists[i] = argv[optind + i];
95 
96 	osmtpd_register_filter_connect(dnsbl_connect);
97 	osmtpd_local_session(dnsbl_session_new, dnsbl_session_free);
98 	if (markspam) {
99 		osmtpd_register_report_begin(1, dnsbl_begin);
100 		osmtpd_register_filter_dataline(dnsbl_dataline);
101 	}
102 	osmtpd_run();
103 
104 	return 0;
105 }
106 
107 void
108 dnsbl_connect(struct osmtpd_ctx *ctx, const char *hostname,
109     struct sockaddr_storage *ss)
110 {
111 	struct dnsbl_session *session = ctx->local_session;
112 	struct asr_query *aq;
113 	char query[255];
114 	u_char *addr;
115 	size_t i;
116 
117 	if (ss->ss_family == AF_INET)
118 		addr = (u_char *)(&(((struct sockaddr_in *)ss)->sin_addr));
119 	else
120 		addr = (u_char *)(&(((struct sockaddr_in6 *)ss)->sin6_addr));
121 	for (i = 0; i < nblacklists; i++) {
122 		if (ss->ss_family == AF_INET) {
123 			if (snprintf(query, sizeof(query), "%u.%u.%u.%u.%s",
124 			    addr[3], addr[2], addr[1], addr[0],
125 			    blacklists[i]) >= (int) sizeof(query))
126 				osmtpd_errx(1,
127 				    "Can't create query, domain too long");
128 		} else if (ss->ss_family == AF_INET6) {
129 			if (snprintf(query, sizeof(query), "%hhx.%hhx.%hhx.%hhx"
130 			    ".%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx"
131 			    ".%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx"
132 			    ".%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%hhx.%s",
133 			    (u_char) (addr[15] & 0xf), (u_char) (addr[15] >> 4),
134 			    (u_char) (addr[14] & 0xf), (u_char) (addr[14] >> 4),
135 			    (u_char) (addr[13] & 0xf), (u_char) (addr[13] >> 4),
136 			    (u_char) (addr[12] & 0xf), (u_char) (addr[12] >> 4),
137 			    (u_char) (addr[11] & 0xf), (u_char) (addr[11] >> 4),
138 			    (u_char) (addr[10] & 0xf), (u_char) (addr[10] >> 4),
139 			    (u_char) (addr[9] & 0xf), (u_char) (addr[9] >> 4),
140 			    (u_char) (addr[8] & 0xf), (u_char) (addr[8] >> 4),
141 			    (u_char) (addr[7] & 0xf), (u_char) (addr[8] >> 4),
142 			    (u_char) (addr[6] & 0xf), (u_char) (addr[7] >> 4),
143 			    (u_char) (addr[5] & 0xf), (u_char) (addr[5] >> 4),
144 			    (u_char) (addr[4] & 0xf), (u_char) (addr[4] >> 4),
145 			    (u_char) (addr[3] & 0xf), (u_char) (addr[3] >> 4),
146 			    (u_char) (addr[2] & 0xf), (u_char) (addr[2] >> 4),
147 			    (u_char) (addr[1] & 0xf), (u_char) (addr[1] >> 4),
148 			    (u_char) (addr[0] & 0xf), (u_char) (addr[0] >> 4),
149 			    blacklists[i]) >= (int) sizeof(query))
150 				osmtpd_errx(1,
151 				    "Can't create query, domain too long");
152 		} else
153 			osmtpd_errx(1, "Invalid address family received");
154 
155 		aq = gethostbyname_async(query, NULL);
156 		session->query[i].event = event_asr_run(aq, dnsbl_resolve,
157 		    &(session->query[i]));
158 		session->query[i].blacklist = i;
159 		session->query[i].session = session;
160 	}
161 }
162 
163 void
164 dnsbl_resolve(struct asr_result *result, void *arg)
165 {
166 	struct dnsbl_query *query = arg;
167 	struct dnsbl_session *session = query->session;
168 	size_t i;
169 
170 	query->resolved = 1;
171 	query->event = NULL;
172 	if (result->ar_hostent != NULL) {
173 		if (!markspam) {
174 			osmtpd_filter_disconnect(session->ctx, "Listed at %s",
175 			    blacklists[query->blacklist]);
176 			fprintf(stderr, "%016"PRIx64" listed at %s: rejected\n",
177 			    session->ctx->reqid, blacklists[query->blacklist]);
178 		} else {
179 			dnsbl_session_query_done(session);
180 			session->listed = query->blacklist;
181 			osmtpd_filter_proceed(session->ctx);
182 			/* Delay logging until we have a message */
183 		}
184 		return;
185 	}
186 	if (result->ar_h_errno != HOST_NOT_FOUND) {
187 		osmtpd_filter_disconnect(session->ctx, "DNS error on %s",
188 		    blacklists[query->blacklist]);
189 		return;
190 	}
191 
192 	for (i = 0; i < nblacklists; i++) {
193 		if (!session->query[i].resolved)
194 			return;
195 	}
196 	osmtpd_filter_proceed(session->ctx);
197 	if (verbose)
198 		fprintf(stderr, "%016"PRIx64" not listed\n",
199 		    session->ctx->reqid);
200 }
201 
202 void
203 dnsbl_begin(struct osmtpd_ctx *ctx, uint32_t msgid)
204 {
205 	struct dnsbl_session *session = ctx->local_session;
206 
207 	if (session->listed != -1) {
208 		if (!session->logged_mark) {
209 			fprintf(stderr, "%016"PRIx64" listed at %s: Marking as "
210 			    "spam\n", ctx->reqid, blacklists[session->listed]);
211 			session->logged_mark = 1;
212 		}
213 		session->set_header = 1;
214 	}
215 }
216 
217 void
218 dnsbl_dataline(struct osmtpd_ctx *ctx, const char *line)
219 {
220 	struct dnsbl_session *session = ctx->local_session;
221 
222 	if (session->set_header) {
223 		osmtpd_filter_dataline(ctx, "X-Spam: yes");
224 		osmtpd_filter_dataline(ctx, "X-Spam-DNSBL: Listed at %s",
225 		    blacklists[session->listed]);
226 		session->set_header = 0;
227 		
228 	}
229 	osmtpd_filter_dataline(ctx, "%s", line);
230 }
231 
232 void
233 dnsbl_session_query_done(struct dnsbl_session *session)
234 {
235 	size_t i;
236 
237 	for (i = 0; i < nblacklists; i++) {
238 		if (!session->query[i].resolved) {
239 			event_asr_abort(session->query[i].event);
240 			session->query[i].resolved = 1;
241 		}
242 	}
243 }
244 
245 void *
246 dnsbl_session_new(struct osmtpd_ctx *ctx)
247 {
248 	struct dnsbl_session *session;
249 
250 	if ((session = calloc(1, sizeof(*session))) == NULL)
251 		osmtpd_err(1, "malloc");
252 	if ((session->query = calloc(nblacklists, sizeof(*(session->query))))
253 	    == NULL)
254 		osmtpd_err(1, "malloc");
255 	session->listed = -1;
256 	session->set_header = 0;
257 	session->logged_mark = 0;
258 	session->ctx = ctx;
259 
260 	return session;
261 }
262 
263 void
264 dnsbl_session_free(struct osmtpd_ctx *ctx, void *data)
265 {
266 	struct dnsbl_session *session = data;
267 
268 	dnsbl_session_query_done(session);
269 	free(session->query);
270 	free(session);
271 }
272 
273 __dead void
274 usage(void)
275 {
276 	fprintf(stderr, "usage: %s [-m] blacklist [...]\n",
277 	    getprogname());
278 	exit(1);
279 }