citadel
About: Citadel is an advanced messaging and collaboration system for groupware and BBS applications (preferred OS: Linux).
  Fossies Dox: citadel.tar.gz  ("unofficial" and yet experimental doxygen-generated source code documentation)  

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locate_host.c
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1// Functions which handle hostname/address lookups and resolution
2//
3// Copyright (c) 1987-2024 by the citadel.org team
4//
5// This program is open source software. Use, duplication, or disclosure
6// is subject to the terms of the GNU General Public License, version 3.
7
8#include "sysdep.h"
9#include <string.h>
10#include <stdio.h>
11#include <syslog.h>
12#include <ctype.h>
13#include <netdb.h>
14#include <netinet/in.h>
15#include <arpa/inet.h>
16#include <sys/time.h>
17#include <libcitadel.h>
18
19#include "context.h"
20#ifdef HAVE_RESOLV_H
21#include <arpa/nameser.h>
22#ifdef HAVE_ARPA_NAMESER_COMPAT_H
23#include <arpa/nameser_compat.h>
24#endif
25#include <resolv.h>
26#endif
27
28#include "domain.h"
29#include "locate_host.h"
30
31// START: some missing macros on OpenBSD 3.9
32#ifndef NS_CMPRSFLGS
33#define NS_CMPRSFLGS 0xc0
34#endif
35#if !defined(NS_MAXCDNAME) && defined (MAXCDNAME)
36#define NS_MAXCDNAME MAXCDNAME
37#endif
38#if !defined(NS_INT16SZ) && defined(INT16SZ)
39#define NS_INT16SZ INT16SZ
40#define NS_INT32SZ INT32SZ
41#endif
42#ifndef NS_GET16
43# define NS_GET16 GETSHORT
44#endif
45// END: some missing macros on OpenBSD 3.9
46
47
48// Given an open client socket, return the host name and IP address at the other end.
49// (IPv4 and IPv6 compatible)
50void locate_host(char *tbuf, size_t n, char *abuf, size_t na, int client_socket) {
51 struct sockaddr_in6 clientaddr;
52 unsigned int addrlen = sizeof(clientaddr);
53
54 tbuf[0] = 0;
55 abuf[0] = 0;
56
57 getpeername(client_socket, (struct sockaddr *)&clientaddr, &addrlen);
58 getnameinfo((struct sockaddr *)&clientaddr, addrlen, tbuf, n, NULL, 0, 0);
59 getnameinfo((struct sockaddr *)&clientaddr, addrlen, abuf, na, NULL, 0, NI_NUMERICHOST);
60
61 // Convert IPv6-mapped IPv4 addresses back to traditional dotted quad.
62 //
63 // Other code here, such as the RBL check, will expect IPv4 addresses to be represented
64 // as dotted-quad, even if they come in over a hybrid IPv6/IPv4 socket.
65 if ( (strlen(abuf) > 7) && (!strncasecmp(abuf, "::ffff:", 7)) ) {
66 if (!strcmp(abuf, tbuf)) strcpy(tbuf, &tbuf[7]);
67 strcpy(abuf, &abuf[7]);
68 }
69}
70
71
72// RBL check written by Edward S. Marshall [http://rblcheck.sourceforge.net]
73#define RESULT_SIZE 4096 // What is the longest result text we support?
74int rblcheck_backend(char *domain, char *txtbuf, int txtbufsize) {
75 int a, b, c;
76 char *result = NULL;
77 u_char fixedans[ PACKETSZ ];
78 u_char *answer;
79 int need_to_free_answer = 0;
80 const u_char *cp;
81 u_char *rp;
82 const u_char *cend;
83 const u_char *rend;
84 int len;
85 char *p = NULL;
86 static int res_initted = 0;
87
88 if (!res_initted) { // only have to do this once
89 res_init();
90 res_initted = 1;
91 }
92
93 // Make our DNS query.
94 answer = fixedans;
96 if (txtbuf != NULL) {
97 snprintf(txtbuf, txtbufsize, "System shutting down");
98 }
99 return (1);
100 }
101 len = res_query(domain, C_IN, T_A, answer, PACKETSZ);
102
103 // Was there a problem? If so, the domain doesn't exist.
104 if (len == -1) {
105 if (txtbuf != NULL) {
106 strcpy(txtbuf, "");
107 }
108 return(0);
109 }
110
111 if (len > PACKETSZ) {
112 answer = malloc(len);
113 need_to_free_answer = 1;
114 len = res_query(domain, C_IN, T_A, answer, len);
115 if( len == -1 ) {
116 if (txtbuf != NULL) {
117 snprintf(txtbuf, txtbufsize, "Message rejected due to known spammer source IP address");
118 }
119 if (need_to_free_answer) free(answer);
120 return(1);
121 }
122 }
124 if (txtbuf != NULL) {
125 snprintf(txtbuf, txtbufsize, "System shutting down");
126 }
127 if (need_to_free_answer) free(answer);
128 return (1);
129 }
130
131 result = (char *) malloc(RESULT_SIZE);
132 result[0] = '\0';
133
134 // Make another DNS query for textual data; this shouldn't
135 // be a performance hit, since it'll now be cached at the
136 // nameserver we're using.
137 len = res_query(domain, C_IN, T_TXT, answer, PACKETSZ);
139 if (txtbuf != NULL) {
140 snprintf(txtbuf, txtbufsize, "System shutting down");
141 }
142 if (need_to_free_answer) free(answer);
143 free(result);
144 return (1);
145 }
146
147 // Just in case there's no TXT record...
148 if (len ==(-1)) {
149 if (txtbuf != NULL) {
150 snprintf(txtbuf, txtbufsize, "Message rejected due to known spammer source IP address");
151 }
152 if (need_to_free_answer) free(answer);
153 free(result);
154 return(1);
155 }
156
157 // Skip the header and the address we queried.
158 cp = answer + sizeof( HEADER );
159 while( *cp != '\0' ) {
160 a = *cp++;
161 while( a-- )
162 cp++;
163 }
164
165 // This seems to be a bit of magic data that we need to
166 // skip. I wish there were good online documentation
167 // for programming for libresolv, so I'd know what I'm
168 // skipping here. Anyone reading this, feel free to
169 // enlighten me.
170 cp += 1 + NS_INT16SZ + NS_INT32SZ;
171
172 // Skip the type, class and ttl.
173 cp += (NS_INT16SZ * 2) + NS_INT32SZ;
174
175 // Get the length and end of the buffer.
176 NS_GET16(c, cp);
177 cend = cp + c;
178
179 // Iterate over any multiple answers we might have. In
180 // this context, it's unlikely, but anyway.
181 rp = (u_char *) result;
182 rend = (u_char *) result + RESULT_SIZE - 1;
183 while (cp < cend && rp < rend) {
184 a = *cp++;
185 if (a != 0) {
186 for (b = a; b > 0 && cp < cend && rp < rend; b--) {
187 if (*cp == '\n' || *cp == '"' || *cp == '\\') {
188 *rp++ = '\\';
189 }
190 *rp++ = *cp++;
191 }
192 }
193 }
194 *rp = '\0';
195 if (txtbuf != NULL) {
196 long len;
197 len = snprintf(txtbuf, txtbufsize, "%s", result);
198
199 // Remove nonprintable characters
200 for (p = txtbuf; *p != '\0'; p++) {
201 if (!isprint(*p)) {
202 memmove (p,
203 p + 1,
204 len - (p - txtbuf) - 1);
205 }
206 }
207 }
208 if (need_to_free_answer) free(answer);
209 free(result);
210 return(1);
211}
212
213
214// Check to see if the client host is on some sort of spam list (RBL)
215// If spammer, returns nonzero and places reason in 'message_to_spammer'
216int rbl_check(char *cs_addr, char *message_to_spammer) {
217 char tbuf[256] = "";
218 int suffix_pos = 0;
219 int rbl;
220 int rc;
221 int num_rbl;
222 char rbl_domains[SIZ];
223 char txt_answer[1024];
224 struct timeval tx_start;
225 struct timeval tx_finish;
226
227 rc = 0;
228 strcpy(message_to_spammer, "ok");
229 gettimeofday(&tx_start, NULL); // start a stopwatch for performance timing
230
231 if ((strchr(cs_addr, '.')) && (!strchr(cs_addr, ':'))) {
232 int a1, a2, a3, a4;
233
234 sscanf(cs_addr, "%d.%d.%d.%d", &a1, &a2, &a3, &a4);
235 snprintf(tbuf, sizeof tbuf, "%d.%d.%d.%d.", a4, a3, a2, a1);
236 suffix_pos = strlen(tbuf);
237 }
238 else if ((!strchr(cs_addr, '.')) && (strchr(cs_addr, ':'))) {
239 int num_colons = 0;
240 int i = 0;
241 char workbuf[sizeof tbuf];
242 char *ptr;
243
244 // tedious code to expand and reverse an IPv6 address
245 safestrncpy(tbuf, cs_addr, sizeof tbuf);
246 num_colons = haschar(tbuf, ':');
247 if ((num_colons < 2) || (num_colons > 7))
248 goto finish_rbl; // badly formed address
249
250 // expand the "::" shorthand
251 while (num_colons < 7) {
252 ptr = strstr(tbuf, "::");
253 if (!ptr)
254 goto finish_rbl; // badly formed address
255
256 ++ptr;
257 strcpy(workbuf, ptr);
258 strcpy(ptr, ":");
259 strcat(ptr, workbuf);
260 ++num_colons;
261 }
262
263 // expand to 32 hex characters with no colons
264 strcpy(workbuf, tbuf);
265 strcpy(tbuf, "00000000000000000000000000000000");
266 for (i=0; i<8; ++i) {
267 char tokbuf[5];
268 extract_token(tokbuf, workbuf, i, ':', sizeof tokbuf);
269 memcpy(&tbuf[ (i*4) + (4-strlen(tokbuf)) ], tokbuf, strlen(tokbuf) );
270 }
271 if (strlen(tbuf) != 32) {
272 goto finish_rbl;
273 }
274
275 // now reverse it and add dots
276 strcpy(workbuf, tbuf);
277 for (i=0; i<32; ++i) {
278 tbuf[i*2] = workbuf[31-i];
279 tbuf[(i*2)+1] = '.';
280 }
281 tbuf[64] = 0;
282 suffix_pos = 64;
283 }
284 else {
285 goto finish_rbl; // unknown address format
286 }
287
288 // See if we have any RBL domains configured
289 num_rbl = get_hosts(rbl_domains, "rbl");
290 if (num_rbl < 1)
291 {
292 goto finish_rbl;
293 }
294
295 // Try all configured RBL's
296 for (rbl=0; rbl<num_rbl; ++rbl) {
297 extract_token(&tbuf[suffix_pos], rbl_domains, rbl, '|', (sizeof tbuf - suffix_pos));
298
299 if (rblcheck_backend(tbuf, txt_answer, sizeof txt_answer)) {
300 strcpy(message_to_spammer, txt_answer);
301 syslog(LOG_INFO, "RBL: %s %s", cs_addr, txt_answer);
302 rc = 1;
303 }
304 }
305finish_rbl:
306 // How long did this transaction take?
307 gettimeofday(&tx_finish, NULL);
308
309 syslog(LOG_WARNING, "rbl: %s [%ld.%06ld] %s",
310 cs_addr,
311 ((tx_finish.tv_sec*1000000 + tx_finish.tv_usec) - (tx_start.tv_sec*1000000 + tx_start.tv_usec)) / 1000000,
312 ((tx_finish.tv_sec*1000000 + tx_finish.tv_usec) - (tx_start.tv_sec*1000000 + tx_start.tv_usec)) % 1000000,
313 (rc)?"found":"none found"
314 );
315
316 return rc;
317}
318
319
320// Convert a host name to a dotted quad address.
321// Returns zero on success or nonzero on failure.
322//
323// FIXME this is obviously not IPv6 compatible.
324int hostname_to_dotted_quad(char *addr, char *host) {
325 struct hostent *ch;
326 const char *i;
327 int a1, a2, a3, a4;
328
329 ch = gethostbyname(host);
330 if (ch == NULL) {
331 strcpy(addr, "0.0.0.0");
332 return(1);
333 }
334
335 i = (const char *) ch->h_addr_list[0];
336 a1 = ((*i++) & 0xff);
337 a2 = ((*i++) & 0xff);
338 a3 = ((*i++) & 0xff);
339 a4 = ((*i++) & 0xff);
340 sprintf(addr, "%d.%d.%d.%d", a1, a2, a3, a4);
341 return(0);
342}
int get_hosts(char *mxbuf, char *rectype)
Definition domain.c:33
int hostname_to_dotted_quad(char *addr, char *host)
#define NS_INT32SZ
Definition locate_host.c:40
void locate_host(char *tbuf, size_t n, char *abuf, size_t na, int client_socket)
Definition locate_host.c:50
int rbl_check(char *cs_addr, char *message_to_spammer)
#define NS_INT16SZ
Definition locate_host.c:39
int rblcheck_backend(char *domain, char *txtbuf, int txtbufsize)
Definition locate_host.c:74
#define RESULT_SIZE
Definition locate_host.c:73
#define NS_GET16
Definition locate_host.c:43
void * malloc(unsigned)
void free(void *)
#define SIZ
Definition sysconfig.h:22
int server_shutting_down
Definition threads.c:22