1 #include "common.h"
2 #include <ndb.h>
3 #include "smtp.h"	/* to publish dial_string_parse */
4 #include <ip.h>
5 #include <thread.h>
6 
7 enum
8 {
9 	Nmx=	16,
10 	Maxstring=	256
11 };
12 
13 typedef struct Mx	Mx;
14 struct Mx
15 {
16 	char host[256];
17 	char ip[24];
18 	int pref;
19 };
20 static Mx mx[Nmx];
21 
22 Ndb *db;
23 extern int debug;
24 
25 static int	mxlookup(DS*, char*);
26 static int	compar(const void*, const void*);
27 static int	callmx(DS*, char*, char*);
28 static void expand_meta(DS *ds);
29 extern int	cistrcmp(char*, char*);
30 
31 /* Taken from imapdial, replaces tlsclient call with stunnel */
32 static int
33 smtpdial(char *server)
34 {
35 	int p[2];
36 	int fd[3];
37 	char *tmp;
38 	char *fpath;
39 
40 	if(pipe(p) < 0)
41 		return -1;
42 	fd[0] = dup(p[0], -1);
43 	fd[1] = dup(p[0], -1);
44 	fd[2] = dup(2, -1);
45 #ifdef PLAN9PORT
46 	tmp = smprint("%s:587", server);
47 	fpath = searchpath("stunnel3");
48 	if (!fpath) {
49 		werrstr("stunnel not found. it is required for tls support.");
50 		return -1;
51 	}
52 	if(threadspawnl(fd, fpath, "stunnel", "-n", "smtp" , "-c", "-r", tmp, nil) < 0) {
53 #else
54 	tmp = smprint("tcp!%s!587", server);
55 	if(threadspawnl(fd, "/bin/tlsclient", "tlsclient", tmp, nil) < 0){
56 #endif
57 		free(tmp);
58 		close(p[0]);
59 		close(p[1]);
60 		close(fd[0]);
61 		close(fd[1]);
62 		close(fd[2]);
63 		return -1;
64 	}
65 	free(tmp);
66 	close(p[0]);
67 	return p[1];
68 }
69 
70 int
71 mxdial(char *addr, char *ddomain, char *gdomain)
72 {
73 	int fd;
74 	DS ds;
75 	char err[Errlen];
76 
77 	addr = netmkaddr(addr, 0, "smtp");
78 	dial_string_parse(addr, &ds);
79 
80 	/* try connecting to destination or any of it's mail routers */
81 	fd = callmx(&ds, addr, ddomain);
82 
83 	/* try our mail gateway */
84 	rerrstr(err, sizeof(err));
85 	if(fd < 0 && gdomain && strstr(err, "can't translate") != 0)
86 		fd = dial(netmkaddr(gdomain, 0, "smtp"), 0, 0, 0);
87 
88 	return fd;
89 }
90 
91 static int
92 timeout(void *v, char *msg)
93 {
94 	USED(v);
95 
96 	if(strstr(msg, "alarm"))
97 		return 1;
98 	return 0;
99 }
100 
101 /*
102  *  take an address and return all the mx entries for it,
103  *  most preferred first
104  */
105 static int
106 callmx(DS *ds, char *dest, char *domain)
107 {
108 	int fd, i, nmx;
109 	char addr[Maxstring];
110 
111 	/* get a list of mx entries */
112 	nmx = mxlookup(ds, domain);
113 	if(nmx < 0){
114 		/* dns isn't working, don't just dial */
115 		return -1;
116 	}
117 	if(nmx == 0){
118 		if(debug)
119 			fprint(2, "mxlookup returns nothing\n");
120 		return dial(dest, 0, 0, 0);
121 	}
122 
123 	/* refuse to honor loopback addresses given by dns */
124 	for(i = 0; i < nmx; i++){
125 		if(strcmp(mx[i].ip, "127.0.0.1") == 0){
126 			if(debug)
127 				fprint(2, "mxlookup returns loopback\n");
128 			werrstr("illegal: domain lists 127.0.0.1 as mail server");
129 			return -1;
130 		}
131 	}
132 
133 	/* sort by preference */
134 	if(nmx > 1)
135 		qsort(mx, nmx, sizeof(Mx), compar);
136 
137 	if(debug){
138 		for(i=0; i<nmx; i++)
139 			print("%s %d\n", mx[i].host, mx[i].pref);
140 	}
141 	/* dial each one in turn */
142 	for(i = 0; i < nmx; i++){
143 #ifdef PLAN9PORT
144 		snprint(addr, sizeof(addr), "%s", mx[i].host);
145 #else
146 		snprint(addr, sizeof(addr), "%s!%s!%s", ds->proto,
147 			mx[i].host, ds->service);
148 #endif
149 		if(debug)
150 			fprint(2, "mxdial trying %s (%d)\n", addr, i);
151 		atnotify(timeout, 1);
152 		alarm(10*1000);
153 #ifdef PLAN9PORT
154 		fd = smtpdial(addr);
155 #else
156 		fd = dial(addr, 0, 0, 0);
157 #endif
158 		alarm(0);
159 		atnotify(timeout, 0);
160 		if(fd >= 0)
161 			return fd;
162 	}
163 	return -1;
164 }
165 
166 /*
167  *  use dns to resolve the mx request
168  */
169 static int
170 mxlookup(DS *ds, char *domain)
171 {
172 	int i, n, nmx;
173 	Ndbtuple *t, *tmx, *tpref, *tip;
174 
175 	strcpy(domain, ds->host);
176 	ds->netdir = "/net";
177 	nmx = 0;
178 	if((t = dnsquery(nil, ds->host, "mx")) != nil){
179 		for(tmx=t; (tmx=ndbfindattr(tmx->entry, nil, "mx")) != nil && nmx<Nmx; ){
180 			for(tpref=tmx->line; tpref != tmx; tpref=tpref->line){
181 				if(strcmp(tpref->attr, "pref") == 0){
182 					strncpy(mx[nmx].host, tmx->val, sizeof(mx[n].host)-1);
183 					mx[nmx].pref = atoi(tpref->val);
184 					nmx++;
185 					break;
186 				}
187 			}
188 		}
189 		ndbfree(t);
190 	}
191 
192 	/*
193 	 * no mx record? try name itself.
194 	 */
195 	/*
196 	 * BUG? If domain has no dots, then we used to look up ds->host
197 	 * but return domain instead of ds->host in the list.  Now we return
198 	 * ds->host.  What will this break?
199 	 */
200 	if(nmx == 0){
201 		mx[0].pref = 1;
202 		strncpy(mx[0].host, ds->host, sizeof(mx[0].host));
203 		nmx++;
204 	}
205 
206 	/*
207 	 * look up all ip addresses
208 	 */
209 	for(i = 0; i < nmx; i++){
210 		if((t = dnsquery(nil, mx[i].host, "ip")) == nil)
211 			goto no;
212 		if((tip = ndbfindattr(t, nil, "ip")) == nil){
213 			ndbfree(t);
214 			goto no;
215 		}
216 		strncpy(mx[i].ip, tip->val, sizeof(mx[i].ip)-1);
217 		ndbfree(t);
218 		continue;
219 
220 	no:
221 		/* remove mx[i] and go around again */
222 		nmx--;
223 		mx[i] = mx[nmx];
224 		i--;
225 	}
226 	return nmx;
227 }
228 
229 static int
230 compar(const void *a, const void *b)
231 {
232 	return ((Mx*)a)->pref - ((Mx*)b)->pref;
233 }
234 
235 /* break up an address to its component parts */
236 void
237 dial_string_parse(char *str, DS *ds)
238 {
239 	char *p, *p2;
240 
241 	strncpy(ds->buf, str, sizeof(ds->buf));
242 	ds->buf[sizeof(ds->buf)-1] = 0;
243 
244 	p = strchr(ds->buf, '!');
245 	if(p == 0) {
246 		ds->netdir = 0;
247 		ds->proto = "net";
248 		ds->host = ds->buf;
249 	} else {
250 		if(*ds->buf != '/'){
251 			ds->netdir = 0;
252 			ds->proto = ds->buf;
253 		} else {
254 			for(p2 = p; *p2 != '/'; p2--)
255 				;
256 			*p2++ = 0;
257 			ds->netdir = ds->buf;
258 			ds->proto = p2;
259 		}
260 		*p = 0;
261 		ds->host = p + 1;
262 	}
263 	ds->service = strchr(ds->host, '!');
264 	if(ds->service)
265 		*ds->service++ = 0;
266 	if(*ds->host == '$')
267 		expand_meta(ds);
268 }
269 
270 static void
271 expand_meta(DS *ds)
272 {
273 	static Ndb *db;
274 	Ndbs s;
275 	char *sys, *smtpserver;
276 
277 	/* can't ask cs, so query database directly. */
278 	sys = sysname();
279 	if(db == nil)
280 		db = ndbopen(0);
281 	smtpserver = ndbgetvalue(db, &s, "sys", sys, "smtp", nil);
282 	snprint(ds->host, 128, "%s", smtpserver);
283 }