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