/*

 * 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)];

#ifdef HAVE_RES_SEARCH

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 fm_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)

	fm_freeaddrinfo(res2);

    if (res1)

	fm_freeaddrinfo(res1);

    return rc;

}

#endif

int is_host_alias(const char *name, struct query *ctl, struct addrinfo **res)

/* determine whether name is a DNS alias of the mailserver for this query */

{

#ifdef HAVE_RES_SEARCH

    struct mxentry	*mxp, *mxrecords;

    int			e;

    struct addrinfo	hints, *res_st;

#endif

    struct idlist	*idl;

    size_t		namelen;

    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)

    {

	const 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 = 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

    (void)res;

    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 = fm_getaddrinfo(name, NULL, &hints, res);

    if (e == 0)

    {

	int rr = (strcasecmp(ctl->server.truename, (*res)->ai_canonname) == 0);

	fm_freeaddrinfo(*res); *res = NULL;

	if (rr)

	    goto match;

        else if (ctl->server.checkalias && 0 == fm_getaddrinfo(ctl->server.truename, NULL, &hints, &res_st))

	{

	    fm_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 */