citadel
About: Citadel is an advanced messaging and collaboration system for groupware and BBS applications (preferred OS: Linux).
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locate_host.c
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1/*
2 * Functions which handle hostname/address lookups and resolution
3 *
4 * Copyright (c) 1987-2019 by the citadel.org team
5 *
6 * This program is open source software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License, version 3.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 */
14
15#include "sysdep.h"
16#include <string.h>
17#include <stdio.h>
18#include <syslog.h>
19#include <ctype.h>
20#include <netdb.h>
21#include <netinet/in.h>
22#include <arpa/inet.h>
23#include <libcitadel.h>
24
25#include "context.h"
26#ifdef HAVE_RESOLV_H
27#include <arpa/nameser.h>
28#ifdef HAVE_ARPA_NAMESER_COMPAT_H
29#include <arpa/nameser_compat.h>
30#endif
31#include <resolv.h>
32#endif
33
34#include "domain.h"
35#include "locate_host.h"
36
37/* START: some missing macros on OpenBSD 3.9 */
38#ifndef NS_CMPRSFLGS
39#define NS_CMPRSFLGS 0xc0
40#endif
41#if !defined(NS_MAXCDNAME) && defined (MAXCDNAME)
42#define NS_MAXCDNAME MAXCDNAME
43#endif
44#if !defined(NS_INT16SZ) && defined(INT16SZ)
45#define NS_INT16SZ INT16SZ
46#define NS_INT32SZ INT32SZ
47#endif
48#ifndef NS_GET16
49# define NS_GET16 GETSHORT
50#endif
51/* END: some missing macros on OpenBSD 3.9 */
52
53
54/*
55 * Given an open client socket, return the host name and IP address at the other end.
56 * (IPv4 and IPv6 compatible)
57 */
58void locate_host(char *tbuf, size_t n, char *abuf, size_t na, int client_socket)
59{
60 struct sockaddr_in6 clientaddr;
61 unsigned int addrlen = sizeof(clientaddr);
62
63 tbuf[0] = 0;
64 abuf[0] = 0;
65
66 getpeername(client_socket, (struct sockaddr *)&clientaddr, &addrlen);
67 getnameinfo((struct sockaddr *)&clientaddr, addrlen, tbuf, n, NULL, 0, 0);
68 getnameinfo((struct sockaddr *)&clientaddr, addrlen, abuf, na, NULL, 0, NI_NUMERICHOST);
69
70 /* Convert IPv6-mapped IPv4 addresses back to traditional dotted quad.
71 *
72 * Other code here, such as the RBL check, will expect IPv4 addresses to be represented
73 * as dotted-quad, even if they come in over a hybrid IPv6/IPv4 socket.
74 */
75 if ( (strlen(abuf) > 7) && (!strncasecmp(abuf, "::ffff:", 7)) ) {
76 if (!strcmp(abuf, tbuf)) strcpy(tbuf, &tbuf[7]);
77 strcpy(abuf, &abuf[7]);
78 }
79}
80
81
82/*
83 * RBL check written by Edward S. Marshall [http://rblcheck.sourceforge.net]
84 */
85#define RESULT_SIZE 4096 /* What is the longest result text we support? */
86int rblcheck_backend(char *domain, char *txtbuf, int txtbufsize) {
87 int a, b, c;
88 char *result = NULL;
89 u_char fixedans[ PACKETSZ ];
90 u_char *answer;
91 int need_to_free_answer = 0;
92 const u_char *cp;
93 u_char *rp;
94 const u_char *cend;
95 const u_char *rend;
96 int len;
97 char *p = NULL;
98 static int res_initted = 0;
99
100 if (!res_initted) { /* only have to do this once */
101 res_init();
102 res_initted = 1;
103 }
104
105 /* Make our DNS query. */
106 answer = fixedans;
108 if (txtbuf != NULL) {
109 snprintf(txtbuf, txtbufsize, "System shutting down");
110 }
111 return (1);
112 }
113 len = res_query(domain, C_IN, T_A, answer, PACKETSZ);
114
115 /* Was there a problem? If so, the domain doesn't exist. */
116 if (len == -1) {
117 if (txtbuf != NULL) {
118 strcpy(txtbuf, "");
119 }
120 return(0);
121 }
122
123 if (len > PACKETSZ) {
124 answer = malloc(len);
125 need_to_free_answer = 1;
126 len = res_query(domain, C_IN, T_A, answer, len);
127 if( len == -1 ) {
128 if (txtbuf != NULL) {
129 snprintf(txtbuf, txtbufsize, "Message rejected due to known spammer source IP address");
130 }
131 if (need_to_free_answer) free(answer);
132 return(1);
133 }
134 }
136 if (txtbuf != NULL) {
137 snprintf(txtbuf, txtbufsize, "System shutting down");
138 }
139 if (need_to_free_answer) free(answer);
140 return (1);
141 }
142
143 result = (char *) malloc(RESULT_SIZE);
144 result[0] = '\0';
145
146 /* Make another DNS query for textual data; this shouldn't
147 * be a performance hit, since it'll now be cached at the
148 * nameserver we're using.
149 */
150 len = res_query(domain, C_IN, T_TXT, answer, PACKETSZ);
152 if (txtbuf != NULL) {
153 snprintf(txtbuf, txtbufsize, "System shutting down");
154 }
155 if (need_to_free_answer) free(answer);
156 free(result);
157 return (1);
158 }
159
160 /* Just in case there's no TXT record... */
161 if (len ==(-1)) {
162 if (txtbuf != NULL) {
163 snprintf(txtbuf, txtbufsize, "Message rejected due to known spammer source IP address");
164 }
165 if (need_to_free_answer) free(answer);
166 free(result);
167 return(1);
168 }
169
170 /* Skip the header and the address we queried. */
171 cp = answer + sizeof( HEADER );
172 while( *cp != '\0' ) {
173 a = *cp++;
174 while( a-- )
175 cp++;
176 }
177
178 /* This seems to be a bit of magic data that we need to
179 * skip. I wish there were good online documentation
180 * for programming for libresolv, so I'd know what I'm
181 * skipping here. Anyone reading this, feel free to
182 * enlighten me.
183 */
184 cp += 1 + NS_INT16SZ + NS_INT32SZ;
185
186 /* Skip the type, class and ttl. */
187 cp += (NS_INT16SZ * 2) + NS_INT32SZ;
188
189 /* Get the length and end of the buffer. */
190 NS_GET16(c, cp);
191 cend = cp + c;
192
193 /* Iterate over any multiple answers we might have. In
194 * this context, it's unlikely, but anyway.
195 */
196 rp = (u_char *) result;
197 rend = (u_char *) result + RESULT_SIZE - 1;
198 while (cp < cend && rp < rend) {
199 a = *cp++;
200 if (a != 0) {
201 for (b = a; b > 0 && cp < cend && rp < rend; b--) {
202 if (*cp == '\n' || *cp == '"' || *cp == '\\') {
203 *rp++ = '\\';
204 }
205 *rp++ = *cp++;
206 }
207 }
208 }
209 *rp = '\0';
210 if (txtbuf != NULL) {
211 long len;
212 len = snprintf(txtbuf, txtbufsize, "%s", result);
213
214 /* Remove nonprintable characters */
215 for (p = txtbuf; *p != '\0'; p++) {
216 if (!isprint(*p)) {
217 memmove (p,
218 p + 1,
219 len - (p - txtbuf) - 1);
220 }
221 }
222 }
223 if (need_to_free_answer) free(answer);
224 free(result);
225 return(1);
226}
227
228
229/*
230 * Check to see if the client host is on some sort of spam list (RBL)
231 * If spammer, returns nonzero and places reason in 'message_to_spammer'
232 */
233int rbl_check(char *cs_addr, char *message_to_spammer)
234{
235 char tbuf[256] = "";
236 int suffix_pos = 0;
237 int rbl;
238 int rc;
239 int num_rbl;
240 char rbl_domains[SIZ];
241 char txt_answer[1024];
242 struct timeval tx_start;
243 struct timeval tx_finish;
244
245 rc = 0;
246 strcpy(message_to_spammer, "ok");
247 gettimeofday(&tx_start, NULL); /* start a stopwatch for performance timing */
248
249 if ((strchr(cs_addr, '.')) && (!strchr(cs_addr, ':'))) {
250 int a1, a2, a3, a4;
251
252 sscanf(cs_addr, "%d.%d.%d.%d", &a1, &a2, &a3, &a4);
253 snprintf(tbuf, sizeof tbuf, "%d.%d.%d.%d.", a4, a3, a2, a1);
254 suffix_pos = strlen(tbuf);
255 }
256 else if ((!strchr(cs_addr, '.')) && (strchr(cs_addr, ':'))) {
257 int num_colons = 0;
258 int i = 0;
259 char workbuf[sizeof tbuf];
260 char *ptr;
261
262 /* tedious code to expand and reverse an IPv6 address */
263 safestrncpy(tbuf, cs_addr, sizeof tbuf);
264 num_colons = haschar(tbuf, ':');
265 if ((num_colons < 2) || (num_colons > 7))
266 goto finish_rbl; /* badly formed address */
267
268 /* expand the "::" shorthand */
269 while (num_colons < 7) {
270 ptr = strstr(tbuf, "::");
271 if (!ptr)
272 goto finish_rbl; /* badly formed address */
273
274 ++ptr;
275 strcpy(workbuf, ptr);
276 strcpy(ptr, ":");
277 strcat(ptr, workbuf);
278 ++num_colons;
279 }
280
281 /* expand to 32 hex characters with no colons */
282 strcpy(workbuf, tbuf);
283 strcpy(tbuf, "00000000000000000000000000000000");
284 for (i=0; i<8; ++i) {
285 char tokbuf[5];
286 extract_token(tokbuf, workbuf, i, ':', sizeof tokbuf);
287 memcpy(&tbuf[ (i*4) + (4-strlen(tokbuf)) ], tokbuf, strlen(tokbuf) );
288 }
289 if (strlen(tbuf) != 32) {
290 goto finish_rbl;
291 }
292
293 /* now reverse it and add dots */
294 strcpy(workbuf, tbuf);
295 for (i=0; i<32; ++i) {
296 tbuf[i*2] = workbuf[31-i];
297 tbuf[(i*2)+1] = '.';
298 }
299 tbuf[64] = 0;
300 suffix_pos = 64;
301 }
302 else {
303 goto finish_rbl; /* unknown address format */
304 }
305
306 /* See if we have any RBL domains configured */
307 num_rbl = get_hosts(rbl_domains, "rbl");
308 if (num_rbl < 1)
309 {
310 goto finish_rbl;
311 }
312
313 /* Try all configured RBL's */
314 for (rbl=0; rbl<num_rbl; ++rbl) {
315 extract_token(&tbuf[suffix_pos], rbl_domains, rbl, '|', (sizeof tbuf - suffix_pos));
316
317 if (rblcheck_backend(tbuf, txt_answer, sizeof txt_answer)) {
318 strcpy(message_to_spammer, txt_answer);
319 syslog(LOG_INFO, "RBL: %s %s", cs_addr, txt_answer);
320 rc = 1;
321 }
322 }
323finish_rbl:
324 /* How long did this transaction take? */
325 gettimeofday(&tx_finish, NULL);
326
327 syslog(LOG_WARNING, "rbl: %s [%ld.%06ld] %s",
328 cs_addr,
329 ((tx_finish.tv_sec*1000000 + tx_finish.tv_usec) - (tx_start.tv_sec*1000000 + tx_start.tv_usec)) / 1000000,
330 ((tx_finish.tv_sec*1000000 + tx_finish.tv_usec) - (tx_start.tv_sec*1000000 + tx_start.tv_usec)) % 1000000,
331 (rc)?"found":"none found"
332 );
333
334 return rc;
335}
336
337
338/*
339 * Convert a host name to a dotted quad address.
340 * Returns zero on success or nonzero on failure.
341 *
342 * FIXME this is obviously not IPv6 compatible.
343 */
344int hostname_to_dotted_quad(char *addr, char *host) {
345 struct hostent *ch;
346 const char *i;
347 int a1, a2, a3, a4;
348
349 ch = gethostbyname(host);
350 if (ch == NULL) {
351 strcpy(addr, "0.0.0.0");
352 return(1);
353 }
354
355 i = (const char *) ch->h_addr_list[0];
356 a1 = ((*i++) & 0xff);
357 a2 = ((*i++) & 0xff);
358 a3 = ((*i++) & 0xff);
359 a4 = ((*i++) & 0xff);
360 sprintf(addr, "%d.%d.%d.%d", a1, a2, a3, a4);
361 return(0);
362}
int get_hosts(char *mxbuf, char *rectype)
Definition: domain.c:39
int hostname_to_dotted_quad(char *addr, char *host)
Definition: locate_host.c:344
#define NS_INT32SZ
Definition: locate_host.c:46
void locate_host(char *tbuf, size_t n, char *abuf, size_t na, int client_socket)
Definition: locate_host.c:58
int rbl_check(char *cs_addr, char *message_to_spammer)
Definition: locate_host.c:233
#define NS_INT16SZ
Definition: locate_host.c:45
int rblcheck_backend(char *domain, char *txtbuf, int txtbufsize)
Definition: locate_host.c:86
#define RESULT_SIZE
Definition: locate_host.c:85
#define NS_GET16
Definition: locate_host.c:49
void * malloc(size_t)
void free(void *)
int snprintf(char *buf, size_t max, const char *fmt,...)
Definition: snprintf.c:69
#define SIZ
Definition: sysconfig.h:33
int server_shutting_down
Definition: threads.c:31