1 /*++
2 /* NAME
3 /* smtp_unalias 3
4 /* SUMMARY
5 /* replace host/domain alias by official name
6 /* SYNOPSIS
7 /* #include "smtp.h"
8 /*
9 /* const char *smtp_unalias_name(name)
10 /* const char *name;
11 /*
12 /* VSTRING *smtp_unalias_addr(result, addr)
13 /* VSTRING *result;
14 /* const char *addr;
15 /* DESCRIPTION
16 /* smtp_unalias_name() looks up A or MX records for the specified
17 /* name and returns the official name provided in the reply. When
18 /* no A or MX record is found, the result is a copy of the input.
19 /* In order to improve performance, smtp_unalias_name() remembers
20 /* results in a private cache, so a name is looked up only once.
21 /*
22 /* smtp_unalias_addr() returns the input address, which is in
23 /* RFC 821 quoted form, after replacing the domain part by the
24 /* official name as found by smtp_unalias_name(). When the input
25 /* contains no domain part, the result is a copy of the input.
26 /* LICENSE
27 /* .ad
28 /* .fi
29 /* The Secure Mailer license must be distributed with this software.
30 /* AUTHOR(S)
31 /* Wietse Venema
32 /* IBM T.J. Watson Research
33 /* P.O. Box 704
34 /* Yorktown Heights, NY 10598, USA
35 /*--*/
36
37 /* System library. */
38
39 #include <sys_defs.h>
40 #include <sys/socket.h>
41 #include <netinet/in.h>
42 #include <arpa/inet.h>
43 #include <stdlib.h>
44 #include <netdb.h>
45 #include <string.h>
46
47 /* Utility library. */
48
49 #include <htable.h>
50 #include <vstring.h>
51 #include <msg.h>
52
53 /* DNS library. */
54
55 #include <dns.h>
56
57 /* Application-specific. */
58
59 #include "smtp.h"
60
61 static int smtp_unalias_flags;
62
63 /* smtp_unalias_name - look up the official host or domain name. */
64
smtp_unalias_name(const char * name)65 const char *smtp_unalias_name(const char *name)
66 {
67 static HTABLE *cache;
68 VSTRING *fqdn;
69 char *result;
70
71 if (*name == '[')
72 return (name);
73
74 /*
75 * Initialize the cache on the fly. The smtp client is designed to exit
76 * after servicing a limited number of requests, so there is no need to
77 * prevent the cache from growing too large, or to expire old entries.
78 */
79 if (cache == 0)
80 cache = htable_create(10);
81
82 /*
83 * Look up the fqdn. If none is found use the query name instead, so that
84 * we won't lose time looking up the same bad name again.
85 */
86 if ((result = htable_find(cache, name)) == 0) {
87 fqdn = vstring_alloc(10);
88 if (dns_lookup_l(name, smtp_unalias_flags, (DNS_RR **) 0, fqdn,
89 (VSTRING *) 0, DNS_REQ_FLAG_NONE, T_MX, T_A,
90 #ifdef HAS_IPV6
91 T_AAAA,
92 #endif
93 0) != DNS_OK)
94 vstring_strcpy(fqdn, name);
95 htable_enter(cache, name, result = vstring_export(fqdn));
96 }
97 return (result);
98 }
99
100 /* smtp_unalias_addr - rewrite aliases in domain part of address */
101
smtp_unalias_addr(VSTRING * result,const char * addr)102 VSTRING *smtp_unalias_addr(VSTRING *result, const char *addr)
103 {
104 char *at;
105 const char *fqdn;
106
107 if ((at = strrchr(addr, '@')) == 0 || at[1] == 0) {
108 vstring_strcpy(result, addr);
109 } else {
110 fqdn = smtp_unalias_name(at + 1);
111 vstring_strncpy(result, addr, at - addr + 1);
112 vstring_strcat(result, fqdn);
113 }
114 return (result);
115 }
116
117 #ifdef TEST
118
119 /*
120 * Test program - read address from stdin, print result on stdout.
121 */
122
123 #include <vstring_vstream.h>
124
main(int unused_argc,char ** unused_argv)125 int main(int unused_argc, char **unused_argv)
126 {
127 VSTRING *addr = vstring_alloc(10);
128 VSTRING *result = vstring_alloc(10);
129
130 smtp_unalias_flags |= RES_DEBUG;
131
132 while (vstring_fgets_nonl(addr, VSTREAM_IN)) {
133 smtp_unalias_addr(result, vstring_str(addr));
134 vstream_printf("%s -> %s\n", vstring_str(addr), vstring_str(result));
135 vstream_fflush(VSTREAM_OUT);
136 }
137 vstring_free(addr);
138 vstring_free(result);
139 return (0);
140 }
141
142 #endif
143