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/*++
/* NAME
/* smtp_unalias 3
/* SUMMARY
/* replace host/domain alias by official name
/* SYNOPSIS
/* #include "smtp.h"
/*
/* const char *smtp_unalias_name(name)
/* const char *name;
/*
/* VSTRING *smtp_unalias_addr(result, addr)
/* VSTRING *result;
/* const char *addr;
/* DESCRIPTION
/* smtp_unalias_name() looks up A or MX records for the specified
/* name and returns the official name provided in the reply. When
/* no A or MX record is found, the result is a copy of the input.
/* In order to improve performance, smtp_unalias_name() remembers
/* results in a private cache, so a name is looked up only once.
/*
/* smtp_unalias_addr() returns the input address, which is in
/* RFC 821 quoted form, after replacing the domain part by the
/* official name as found by smtp_unalias_name(). When the input
/* contains no domain part, the result is a copy of the input.
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/* Wietse Venema
/* IBM T.J. Watson Research
/* P.O. Box 704
/* Yorktown Heights, NY 10598, USA
/*--*/
/* System library. */
#include <sys_defs.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <netdb.h>
#include <string.h>
/* Utility library. */
#include <htable.h>
#include <vstring.h>
#include <msg.h>
/* DNS library. */
#include <dns.h>
/* Application-specific. */
#include "smtp.h"
static int smtp_unalias_flags;
/* smtp_unalias_name - look up the official host or domain name. */
const char *smtp_unalias_name(const char *name)
{
static HTABLE *cache;
VSTRING *fqdn;
char *result;
if (*name == '[')
return (name);
/*
* Initialize the cache on the fly. The smtp client is designed to exit
* after servicing a limited number of requests, so there is no need to
* prevent the cache from growing too large, or to expire old entries.
*/
if (cache == 0)
cache = htable_create(10);
/*
* Look up the fqdn. If none is found use the query name instead, so that
* we won't lose time looking up the same bad name again.
*/
if ((result = htable_find(cache, name)) == 0) {
fqdn = vstring_alloc(10);
if (dns_lookup_l(name, smtp_unalias_flags, (DNS_RR **) 0, fqdn,
(VSTRING *) 0, DNS_REQ_FLAG_NONE, T_MX, T_A,
#ifdef HAS_IPV6
T_AAAA,
#endif
0) != DNS_OK)
vstring_strcpy(fqdn, name);
htable_enter(cache, name, result = vstring_export(fqdn));
}
return (result);
}
/* smtp_unalias_addr - rewrite aliases in domain part of address */
VSTRING *smtp_unalias_addr(VSTRING *result, const char *addr)
{
char *at;
const char *fqdn;
if ((at = strrchr(addr, '@')) == 0 || at[1] == 0) {
vstring_strcpy(result, addr);
} else {
fqdn = smtp_unalias_name(at + 1);
vstring_strncpy(result, addr, at - addr + 1);
vstring_strcat(result, fqdn);
}
return (result);
}
#ifdef TEST
/*
* Test program - read address from stdin, print result on stdout.
*/
#include <vstring_vstream.h>
int main(int unused_argc, char **unused_argv)
{
VSTRING *addr = vstring_alloc(10);
VSTRING *result = vstring_alloc(10);
smtp_unalias_flags |= RES_DEBUG;
while (vstring_fgets_nonl(addr, VSTREAM_IN)) {
smtp_unalias_addr(result, vstring_str(addr));
vstream_printf("%s -> %s\n", vstring_str(addr), vstring_str(result));
vstream_fflush(VSTREAM_OUT);
}
vstring_free(addr);
vstring_free(result);
return (0);
}
#endif
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