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/*
* checkalias.c -- check to see if two hostnames or IP addresses are equivalent
*
* Copyright 1997 by Eric S. Raymond
* For license terms, see the file COPYING in this directory.
*/
#include "config.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#ifdef HAVE_NET_SOCKET_H
#include <net/socket.h>
#else
#include <sys/socket.h>
#endif
#include <netinet/in.h>
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#include <netdb.h>
#include "i18n.h"
#include "mx.h"
#include "fetchmail.h"
#include "getaddrinfo.h"
#define MX_RETRIES 3
typedef unsigned char address_t[sizeof (struct in_addr)];
static int getaddresses(struct addrinfo **result, const char *name)
{
struct addrinfo hints;
memset(&hints, 0, sizeof(hints));
hints.ai_socktype=SOCK_STREAM;
hints.ai_protocol=PF_UNSPEC;
hints.ai_family=AF_UNSPEC;
return getaddrinfo(name, NULL, &hints, result);
}
/* XXX FIXME: doesn't detect if an IPv6-mapped IPv4 address
* matches a real IPv4 address */
static int compareaddr(const struct addrinfo *a1, const struct addrinfo *a2)
{
if (a1->ai_family != a2->ai_family) return FALSE;
if (a1->ai_addrlen != a2->ai_addrlen) return FALSE;
return (!memcmp(a1->ai_addr, a2->ai_addr, a1->ai_addrlen));
}
static int is_ip_alias(const char *name1,const char *name2)
/*
* Given two hostnames as arguments, returns TRUE if they
* have at least one IP address in common.
* No check is done on errors returned by gethostbyname,
* the calling function does them.
*/
{
int rc = FALSE;
struct addrinfo *res1 = NULL, *res2 = NULL, *ii, *ij;
if (getaddresses(&res1, name1))
goto found;
if (getaddresses(&res2, name2))
goto found;
for (ii = res1 ; ii ; ii = ii -> ai_next) {
for (ij = res2 ; ij ; ij = ij -> ai_next) {
if (compareaddr(ii, ij)) {
rc = TRUE;
goto found;
}
}
}
found:
if (res2)
freeaddrinfo(res2);
if (res1)
freeaddrinfo(res1);
return rc;
}
int is_host_alias(const char *name, struct query *ctl)
/* determine whether name is a DNS alias of the mailserver for this query */
{
struct mxentry *mxp, *mxrecords;
struct idlist *idl;
size_t namelen;
int e;
struct addrinfo hints, *res, *res_st;
struct hostdata *lead_server =
ctl->server.lead_server ? ctl->server.lead_server : &ctl->server;
/*
* The first two checks are optimizations that will catch a good
* many cases.
*
* (1) check against the `true name' deduced from the poll label
* and the via option (if present) at the beginning of the poll cycle.
* Odds are good this will either be the mailserver's FQDN or a suffix of
* it with the mailserver's domain's default host name omitted.
*
* (2) Then check the rest of the `also known as'
* cache accumulated by previous DNS checks. This cache is primed
* by the aka list option.
*
* Any of these on a mail address is definitive. Only if the
* name doesn't match any is it time to call the bind library.
* If this happens odds are good we're looking at an MX name.
*/
if (strcasecmp(lead_server->truename, name) == 0)
return(TRUE);
else if (str_in_list(&lead_server->akalist, name, TRUE))
return(TRUE);
/*
* Now check for a suffix match on the akalist. The theory here is
* that if the user says `aka netaxs.com', we actually want to match
* foo.netaxs.com and bar.netaxs.com.
*/
namelen = strlen(name);
for (idl = lead_server->akalist; idl; idl = idl->next)
{
char *ep;
/*
* Test is >= here because str_in_list() should have caught the
* equal-length case above. Doing it this way guarantees that
* ep[-1] is a valid reference.
*/
if (strlen(idl->id) >= namelen)
continue;
ep = (char *)name + (namelen - strlen(idl->id));
/* a suffix led by . must match */
if (ep[-1] == '.' && !strcasecmp(ep, idl->id))
return(TRUE);
}
if (!ctl->server.dns)
return(FALSE);
#ifndef HAVE_RES_SEARCH
return(FALSE);
#else
/*
* The only code that calls the BIND library is here and in the
* start-of-run probe with gethostbyname(3) under ETRN/Kerberos.
*
* We know DNS service was up at the beginning of the run.
* If it's down, our nameserver has crashed. We don't want to try
* delivering the current message or anything else from the
* current server until it's back up.
*/
memset(&hints, 0, sizeof hints);
hints.ai_family=AF_UNSPEC;
hints.ai_protocol=PF_UNSPEC;
hints.ai_socktype=SOCK_STREAM;
hints.ai_flags=AI_CANONNAME;
e = getaddrinfo(name, NULL, &hints, &res);
if (e == 0)
{
int rr = (strcasecmp(ctl->server.truename, res->ai_canonname) == 0);
freeaddrinfo(res);
if (rr)
goto match;
else if (ctl->server.checkalias && 0 == getaddrinfo(ctl->server.truename, NULL, &hints, &res_st))
{
freeaddrinfo(res_st);
if (outlevel >= O_DEBUG)
report(stdout, GT_("Checking if %s is really the same node as %s\n"),ctl->server.truename,name);
if (is_ip_alias(ctl->server.truename,name) == TRUE)
{
if (outlevel >= O_DEBUG)
report(stdout, GT_("Yes, their IP addresses match\n"));
goto match;
}
if (outlevel >= O_DEBUG)
report(stdout, GT_("No, their IP addresses don't match\n"));
return(FALSE);
} else {
return(FALSE);
}
}
else
switch (e)
{
case EAI_NONAME: /* specified host is unknown */
break;
default:
if (outlevel != O_SILENT)
report_complete(stdout, "\n"); /* terminate the progress message */
report(stderr,
GT_("nameserver failure while looking for '%s' during poll of %s: %s\n"),
name, ctl->server.pollname, gai_strerror(e));
ctl->errcount++;
break;
}
/*
* We're only here if DNS was OK but the gethostbyname() failed
* with a HOST_NOT_FOUND or NO_ADDRESS error.
* Search for a name match on MX records pointing to the server.
*/
h_errno = 0;
if ((mxrecords = getmxrecords(name)) == (struct mxentry *)NULL)
{
switch (h_errno)
{
case HOST_NOT_FOUND: /* specified host is unknown */
#ifdef NO_ADDRESS
case NO_ADDRESS: /* valid, but does not have an IP address */
return(FALSE);
#endif
case NO_RECOVERY: /* non-recoverable name server error */
case TRY_AGAIN: /* temporary error on authoritative server */
default:
report(stderr,
GT_("nameserver failure while looking for `%s' during poll of %s.\n"),
name, ctl->server.pollname);
ctl->errcount++;
break;
}
} else {
for (mxp = mxrecords; mxp->name; mxp++)
if (strcasecmp(ctl->server.truename, mxp->name) == 0
|| is_ip_alias(ctl->server.truename, mxp->name) == TRUE)
goto match;
return(FALSE);
match:;
}
/* add this name to relevant server's `also known as' list */
save_str(&lead_server->akalist, name, 0);
return(TRUE);
#endif /* HAVE_RES_SEARCH */
}
/* checkalias.c ends here */
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