/src/freebsd/contrib/sendmail/src/domain.c
C | 1147 lines | 774 code | 108 blank | 265 comment | 245 complexity | 5bf8fc1c00624feb55c75e0d7d9b9f62 MD5 | raw file
Possible License(s): CC0-1.0, MIT, LGPL-2.0, LGPL-3.0, WTFPL, GPL-2.0, BSD-2-Clause, AGPL-3.0, CC-BY-SA-3.0, MPL-2.0, JSON, BSD-3-Clause-No-Nuclear-License-2014, LGPL-2.1, CPL-1.0, AGPL-1.0, 0BSD, ISC, Apache-2.0, GPL-3.0, IPL-1.0, MPL-2.0-no-copyleft-exception, BSD-3-Clause
- /*
- * Copyright (c) 1998-2004, 2006, 2010 Sendmail, Inc. and its suppliers.
- * All rights reserved.
- * Copyright (c) 1986, 1995-1997 Eric P. Allman. All rights reserved.
- * Copyright (c) 1988, 1993
- * The Regents of the University of California. All rights reserved.
- *
- * By using this file, you agree to the terms and conditions set
- * forth in the LICENSE file which can be found at the top level of
- * the sendmail distribution.
- *
- */
- #include <sendmail.h>
- #include "map.h"
- #if NAMED_BIND
- SM_RCSID("@(#)$Id: domain.c,v 8.204 2010/06/29 15:35:33 ca Exp $ (with name server)")
- #else /* NAMED_BIND */
- SM_RCSID("@(#)$Id: domain.c,v 8.204 2010/06/29 15:35:33 ca Exp $ (without name server)")
- #endif /* NAMED_BIND */
- #if NAMED_BIND
- # include <arpa/inet.h>
- # ifndef MXHOSTBUFSIZE
- # define MXHOSTBUFSIZE (128 * MAXMXHOSTS)
- # endif /* ! MXHOSTBUFSIZE */
- static char MXHostBuf[MXHOSTBUFSIZE];
- #if (MXHOSTBUFSIZE < 2) || (MXHOSTBUFSIZE >= INT_MAX/2)
- ERROR: _MXHOSTBUFSIZE is out of range
- #endif /* (MXHOSTBUFSIZE < 2) || (MXHOSTBUFSIZE >= INT_MAX/2) */
- # ifndef MAXDNSRCH
- # define MAXDNSRCH 6 /* number of possible domains to search */
- # endif /* ! MAXDNSRCH */
- # ifndef RES_DNSRCH_VARIABLE
- # define RES_DNSRCH_VARIABLE _res.dnsrch
- # endif /* ! RES_DNSRCH_VARIABLE */
- # ifndef NO_DATA
- # define NO_DATA NO_ADDRESS
- # endif /* ! NO_DATA */
- # ifndef HFIXEDSZ
- # define HFIXEDSZ 12 /* sizeof(HEADER) */
- # endif /* ! HFIXEDSZ */
- # define MAXCNAMEDEPTH 10 /* maximum depth of CNAME recursion */
- # if defined(__RES) && (__RES >= 19940415)
- # define RES_UNC_T char *
- # else /* defined(__RES) && (__RES >= 19940415) */
- # define RES_UNC_T unsigned char *
- # endif /* defined(__RES) && (__RES >= 19940415) */
- static int mxrand __P((char *));
- static int fallbackmxrr __P((int, unsigned short *, char **));
- /*
- ** GETFALLBACKMXRR -- get MX resource records for fallback MX host.
- **
- ** We have to initialize this once before doing anything else.
- ** Moreover, we have to repeat this from time to time to avoid
- ** stale data, e.g., in persistent queue runners.
- ** This should be done in a parent process so the child
- ** processes have the right data.
- **
- ** Parameters:
- ** host -- the name of the fallback MX host.
- **
- ** Returns:
- ** number of MX records.
- **
- ** Side Effects:
- ** Populates NumFallbackMXHosts and fbhosts.
- ** Sets renewal time (based on TTL).
- */
- int NumFallbackMXHosts = 0; /* Number of fallback MX hosts (after MX expansion) */
- static char *fbhosts[MAXMXHOSTS + 1];
- int
- getfallbackmxrr(host)
- char *host;
- {
- int i, rcode;
- int ttl;
- static time_t renew = 0;
- #if 0
- /* This is currently done before this function is called. */
- if (host == NULL || *host == '\0')
- return 0;
- #endif /* 0 */
- if (NumFallbackMXHosts > 0 && renew > curtime())
- return NumFallbackMXHosts;
- if (host[0] == '[')
- {
- fbhosts[0] = host;
- NumFallbackMXHosts = 1;
- }
- else
- {
- /* free old data */
- for (i = 0; i < NumFallbackMXHosts; i++)
- sm_free(fbhosts[i]);
- /* get new data */
- NumFallbackMXHosts = getmxrr(host, fbhosts, NULL, false,
- &rcode, false, &ttl);
- renew = curtime() + ttl;
- for (i = 0; i < NumFallbackMXHosts; i++)
- fbhosts[i] = newstr(fbhosts[i]);
- }
- return NumFallbackMXHosts;
- }
- /*
- ** FALLBACKMXRR -- add MX resource records for fallback MX host to list.
- **
- ** Parameters:
- ** nmx -- current number of MX records.
- ** prefs -- array of preferences.
- ** mxhosts -- array of MX hosts (maximum size: MAXMXHOSTS)
- **
- ** Returns:
- ** new number of MX records.
- **
- ** Side Effects:
- ** If FallbackMX was set, it appends the MX records for
- ** that host to mxhosts (and modifies prefs accordingly).
- */
- static int
- fallbackmxrr(nmx, prefs, mxhosts)
- int nmx;
- unsigned short *prefs;
- char **mxhosts;
- {
- int i;
- for (i = 0; i < NumFallbackMXHosts && nmx < MAXMXHOSTS; i++)
- {
- if (nmx > 0)
- prefs[nmx] = prefs[nmx - 1] + 1;
- else
- prefs[nmx] = 0;
- mxhosts[nmx++] = fbhosts[i];
- }
- return nmx;
- }
- /*
- ** GETMXRR -- get MX resource records for a domain
- **
- ** Parameters:
- ** host -- the name of the host to MX.
- ** mxhosts -- a pointer to a return buffer of MX records.
- ** mxprefs -- a pointer to a return buffer of MX preferences.
- ** If NULL, don't try to populate.
- ** droplocalhost -- If true, all MX records less preferred
- ** than the local host (as determined by $=w) will
- ** be discarded.
- ** rcode -- a pointer to an EX_ status code.
- ** tryfallback -- add also fallback MX host?
- ** pttl -- pointer to return TTL (can be NULL).
- **
- ** Returns:
- ** The number of MX records found.
- ** -1 if there is an internal failure.
- ** If no MX records are found, mxhosts[0] is set to host
- ** and 1 is returned.
- **
- ** Side Effects:
- ** The entries made for mxhosts point to a static array
- ** MXHostBuf[MXHOSTBUFSIZE], so the data needs to be copied,
- ** if it must be preserved across calls to this function.
- */
- int
- getmxrr(host, mxhosts, mxprefs, droplocalhost, rcode, tryfallback, pttl)
- char *host;
- char **mxhosts;
- unsigned short *mxprefs;
- bool droplocalhost;
- int *rcode;
- bool tryfallback;
- int *pttl;
- {
- register unsigned char *eom, *cp;
- register int i, j, n;
- int nmx = 0;
- register char *bp;
- HEADER *hp;
- querybuf answer;
- int ancount, qdcount, buflen;
- bool seenlocal = false;
- unsigned short pref, type;
- unsigned short localpref = 256;
- char *fallbackMX = FallbackMX;
- bool trycanon = false;
- unsigned short *prefs;
- int (*resfunc) __P((const char *, int, int, u_char *, int));
- unsigned short prefer[MAXMXHOSTS];
- int weight[MAXMXHOSTS];
- int ttl = 0;
- extern int res_query(), res_search();
- if (tTd(8, 2))
- sm_dprintf("getmxrr(%s, droplocalhost=%d)\n",
- host, droplocalhost);
- *rcode = EX_OK;
- if (pttl != NULL)
- *pttl = SM_DEFAULT_TTL;
- if (*host == '\0')
- return 0;
- if ((fallbackMX != NULL && droplocalhost &&
- wordinclass(fallbackMX, 'w')) || !tryfallback)
- {
- /* don't use fallback for this pass */
- fallbackMX = NULL;
- }
- if (mxprefs != NULL)
- prefs = mxprefs;
- else
- prefs = prefer;
- /* efficiency hack -- numeric or non-MX lookups */
- if (host[0] == '[')
- goto punt;
- /*
- ** If we don't have MX records in our host switch, don't
- ** try for MX records. Note that this really isn't "right",
- ** since we might be set up to try NIS first and then DNS;
- ** if the host is found in NIS we really shouldn't be doing
- ** MX lookups. However, that should be a degenerate case.
- */
- if (!UseNameServer)
- goto punt;
- if (HasWildcardMX && ConfigLevel >= 6)
- resfunc = res_query;
- else
- resfunc = res_search;
- errno = 0;
- n = (*resfunc)(host, C_IN, T_MX, (unsigned char *) &answer,
- sizeof(answer));
- if (n < 0)
- {
- if (tTd(8, 1))
- sm_dprintf("getmxrr: res_search(%s) failed (errno=%d, h_errno=%d)\n",
- host, errno, h_errno);
- switch (h_errno)
- {
- case NO_DATA:
- trycanon = true;
- /* FALLTHROUGH */
- case NO_RECOVERY:
- /* no MX data on this host */
- goto punt;
- case HOST_NOT_FOUND:
- # if BROKEN_RES_SEARCH
- case 0: /* Ultrix resolver retns failure w/ h_errno=0 */
- # endif /* BROKEN_RES_SEARCH */
- /* host doesn't exist in DNS; might be in /etc/hosts */
- trycanon = true;
- *rcode = EX_NOHOST;
- goto punt;
- case TRY_AGAIN:
- case -1:
- /* couldn't connect to the name server */
- if (fallbackMX != NULL)
- {
- /* name server is hosed -- push to fallback */
- return fallbackmxrr(nmx, prefs, mxhosts);
- }
- /* it might come up later; better queue it up */
- *rcode = EX_TEMPFAIL;
- break;
- default:
- syserr("getmxrr: res_search (%s) failed with impossible h_errno (%d)",
- host, h_errno);
- *rcode = EX_OSERR;
- break;
- }
- /* irreconcilable differences */
- return -1;
- }
- /* avoid problems after truncation in tcp packets */
- if (n > sizeof(answer))
- n = sizeof(answer);
- /* find first satisfactory answer */
- hp = (HEADER *)&answer;
- cp = (unsigned char *)&answer + HFIXEDSZ;
- eom = (unsigned char *)&answer + n;
- for (qdcount = ntohs((unsigned short) hp->qdcount);
- qdcount--;
- cp += n + QFIXEDSZ)
- {
- if ((n = dn_skipname(cp, eom)) < 0)
- goto punt;
- }
- /* NOTE: see definition of MXHostBuf! */
- buflen = sizeof(MXHostBuf) - 1;
- SM_ASSERT(buflen > 0);
- bp = MXHostBuf;
- ancount = ntohs((unsigned short) hp->ancount);
- /* See RFC 1035 for layout of RRs. */
- /* XXX leave room for FallbackMX ? */
- while (--ancount >= 0 && cp < eom && nmx < MAXMXHOSTS - 1)
- {
- if ((n = dn_expand((unsigned char *)&answer, eom, cp,
- (RES_UNC_T) bp, buflen)) < 0)
- break;
- cp += n;
- GETSHORT(type, cp);
- cp += INT16SZ; /* skip over class */
- GETLONG(ttl, cp);
- GETSHORT(n, cp); /* rdlength */
- if (type != T_MX)
- {
- if (tTd(8, 8) || _res.options & RES_DEBUG)
- sm_dprintf("unexpected answer type %d, size %d\n",
- type, n);
- cp += n;
- continue;
- }
- GETSHORT(pref, cp);
- if ((n = dn_expand((unsigned char *)&answer, eom, cp,
- (RES_UNC_T) bp, buflen)) < 0)
- break;
- cp += n;
- n = strlen(bp);
- # if 0
- /* Can this happen? */
- if (n == 0)
- {
- if (LogLevel > 4)
- sm_syslog(LOG_ERR, NOQID,
- "MX records for %s contain empty string",
- host);
- continue;
- }
- # endif /* 0 */
- if (wordinclass(bp, 'w'))
- {
- if (tTd(8, 3))
- sm_dprintf("found localhost (%s) in MX list, pref=%d\n",
- bp, pref);
- if (droplocalhost)
- {
- if (!seenlocal || pref < localpref)
- localpref = pref;
- seenlocal = true;
- continue;
- }
- weight[nmx] = 0;
- }
- else
- weight[nmx] = mxrand(bp);
- prefs[nmx] = pref;
- mxhosts[nmx++] = bp;
- bp += n;
- if (bp[-1] != '.')
- {
- *bp++ = '.';
- n++;
- }
- *bp++ = '\0';
- if (buflen < n + 1)
- {
- /* don't want to wrap buflen */
- break;
- }
- buflen -= n + 1;
- }
- /* return only one TTL entry, that should be sufficient */
- if (ttl > 0 && pttl != NULL)
- *pttl = ttl;
- /* sort the records */
- for (i = 0; i < nmx; i++)
- {
- for (j = i + 1; j < nmx; j++)
- {
- if (prefs[i] > prefs[j] ||
- (prefs[i] == prefs[j] && weight[i] > weight[j]))
- {
- register int temp;
- register char *temp1;
- temp = prefs[i];
- prefs[i] = prefs[j];
- prefs[j] = temp;
- temp1 = mxhosts[i];
- mxhosts[i] = mxhosts[j];
- mxhosts[j] = temp1;
- temp = weight[i];
- weight[i] = weight[j];
- weight[j] = temp;
- }
- }
- if (seenlocal && prefs[i] >= localpref)
- {
- /* truncate higher preference part of list */
- nmx = i;
- }
- }
- /* delete duplicates from list (yes, some bozos have duplicates) */
- for (i = 0; i < nmx - 1; )
- {
- if (sm_strcasecmp(mxhosts[i], mxhosts[i + 1]) != 0)
- i++;
- else
- {
- /* compress out duplicate */
- for (j = i + 1; j < nmx; j++)
- {
- mxhosts[j] = mxhosts[j + 1];
- prefs[j] = prefs[j + 1];
- }
- nmx--;
- }
- }
- if (nmx == 0)
- {
- punt:
- if (seenlocal)
- {
- struct hostent *h = NULL;
- /*
- ** If we have deleted all MX entries, this is
- ** an error -- we should NEVER send to a host that
- ** has an MX, and this should have been caught
- ** earlier in the config file.
- **
- ** Some sites prefer to go ahead and try the
- ** A record anyway; that case is handled by
- ** setting TryNullMXList. I believe this is a
- ** bad idea, but it's up to you....
- */
- if (TryNullMXList)
- {
- SM_SET_H_ERRNO(0);
- errno = 0;
- h = sm_gethostbyname(host, AF_INET);
- if (h == NULL)
- {
- if (errno == ETIMEDOUT ||
- h_errno == TRY_AGAIN ||
- (errno == ECONNREFUSED &&
- UseNameServer))
- {
- *rcode = EX_TEMPFAIL;
- return -1;
- }
- # if NETINET6
- SM_SET_H_ERRNO(0);
- errno = 0;
- h = sm_gethostbyname(host, AF_INET6);
- if (h == NULL &&
- (errno == ETIMEDOUT ||
- h_errno == TRY_AGAIN ||
- (errno == ECONNREFUSED &&
- UseNameServer)))
- {
- *rcode = EX_TEMPFAIL;
- return -1;
- }
- # endif /* NETINET6 */
- }
- }
- if (h == NULL)
- {
- *rcode = EX_CONFIG;
- syserr("MX list for %s points back to %s",
- host, MyHostName);
- return -1;
- }
- # if NETINET6
- freehostent(h);
- h = NULL;
- # endif /* NETINET6 */
- }
- if (strlen(host) >= sizeof(MXHostBuf))
- {
- *rcode = EX_CONFIG;
- syserr("Host name %s too long",
- shortenstring(host, MAXSHORTSTR));
- return -1;
- }
- (void) sm_strlcpy(MXHostBuf, host, sizeof(MXHostBuf));
- mxhosts[0] = MXHostBuf;
- prefs[0] = 0;
- if (host[0] == '[')
- {
- register char *p;
- # if NETINET6
- struct sockaddr_in6 tmp6;
- # endif /* NETINET6 */
- /* this may be an MX suppression-style address */
- p = strchr(MXHostBuf, ']');
- if (p != NULL)
- {
- *p = '\0';
- if (inet_addr(&MXHostBuf[1]) != INADDR_NONE)
- {
- nmx++;
- *p = ']';
- }
- # if NETINET6
- else if (anynet_pton(AF_INET6, &MXHostBuf[1],
- &tmp6.sin6_addr) == 1)
- {
- nmx++;
- *p = ']';
- }
- # endif /* NETINET6 */
- else
- {
- trycanon = true;
- mxhosts[0]++;
- }
- }
- }
- if (trycanon &&
- getcanonname(mxhosts[0], sizeof(MXHostBuf) - 2, false, pttl))
- {
- /* XXX MXHostBuf == "" ? is that possible? */
- bp = &MXHostBuf[strlen(MXHostBuf)];
- if (bp[-1] != '.')
- {
- *bp++ = '.';
- *bp = '\0';
- }
- nmx = 1;
- }
- }
- /* if we have a default lowest preference, include that */
- if (fallbackMX != NULL && !seenlocal)
- {
- nmx = fallbackmxrr(nmx, prefs, mxhosts);
- }
- return nmx;
- }
- /*
- ** MXRAND -- create a randomizer for equal MX preferences
- **
- ** If two MX hosts have equal preferences we want to randomize
- ** the selection. But in order for signatures to be the same,
- ** we need to randomize the same way each time. This function
- ** computes a pseudo-random hash function from the host name.
- **
- ** Parameters:
- ** host -- the name of the host.
- **
- ** Returns:
- ** A random but repeatable value based on the host name.
- */
- static int
- mxrand(host)
- register char *host;
- {
- int hfunc;
- static unsigned int seed;
- if (seed == 0)
- {
- seed = (int) curtime() & 0xffff;
- if (seed == 0)
- seed++;
- }
- if (tTd(17, 9))
- sm_dprintf("mxrand(%s)", host);
- hfunc = seed;
- while (*host != '\0')
- {
- int c = *host++;
- if (isascii(c) && isupper(c))
- c = tolower(c);
- hfunc = ((hfunc << 1) ^ c) % 2003;
- }
- hfunc &= 0xff;
- hfunc++;
- if (tTd(17, 9))
- sm_dprintf(" = %d\n", hfunc);
- return hfunc;
- }
- /*
- ** BESTMX -- find the best MX for a name
- **
- ** This is really a hack, but I don't see any obvious way
- ** to generalize it at the moment.
- */
- /* ARGSUSED3 */
- char *
- bestmx_map_lookup(map, name, av, statp)
- MAP *map;
- char *name;
- char **av;
- int *statp;
- {
- int nmx;
- int saveopts = _res.options;
- int i;
- ssize_t len = 0;
- char *result;
- char *mxhosts[MAXMXHOSTS + 1];
- #if _FFR_BESTMX_BETTER_TRUNCATION
- char *buf;
- #else /* _FFR_BESTMX_BETTER_TRUNCATION */
- char *p;
- char buf[PSBUFSIZE / 2];
- #endif /* _FFR_BESTMX_BETTER_TRUNCATION */
- _res.options &= ~(RES_DNSRCH|RES_DEFNAMES);
- nmx = getmxrr(name, mxhosts, NULL, false, statp, false, NULL);
- _res.options = saveopts;
- if (nmx <= 0)
- return NULL;
- if (bitset(MF_MATCHONLY, map->map_mflags))
- return map_rewrite(map, name, strlen(name), NULL);
- if ((map->map_coldelim == '\0') || (nmx == 1))
- return map_rewrite(map, mxhosts[0], strlen(mxhosts[0]), av);
- /*
- ** We were given a -z flag (return all MXs) and there are multiple
- ** ones. We need to build them all into a list.
- */
- #if _FFR_BESTMX_BETTER_TRUNCATION
- for (i = 0; i < nmx; i++)
- {
- if (strchr(mxhosts[i], map->map_coldelim) != NULL)
- {
- syserr("bestmx_map_lookup: MX host %.64s includes map delimiter character 0x%02X",
- mxhosts[i], map->map_coldelim);
- return NULL;
- }
- len += strlen(mxhosts[i]) + 1;
- if (len < 0)
- {
- len -= strlen(mxhosts[i]) + 1;
- break;
- }
- }
- buf = (char *) sm_malloc(len);
- if (buf == NULL)
- {
- *statp = EX_UNAVAILABLE;
- return NULL;
- }
- *buf = '\0';
- for (i = 0; i < nmx; i++)
- {
- int end;
- end = sm_strlcat(buf, mxhosts[i], len);
- if (i != nmx && end + 1 < len)
- {
- buf[end] = map->map_coldelim;
- buf[end + 1] = '\0';
- }
- }
- /* Cleanly truncate for rulesets */
- truncate_at_delim(buf, PSBUFSIZE / 2, map->map_coldelim);
- #else /* _FFR_BESTMX_BETTER_TRUNCATION */
- p = buf;
- for (i = 0; i < nmx; i++)
- {
- size_t slen;
- if (strchr(mxhosts[i], map->map_coldelim) != NULL)
- {
- syserr("bestmx_map_lookup: MX host %.64s includes map delimiter character 0x%02X",
- mxhosts[i], map->map_coldelim);
- return NULL;
- }
- slen = strlen(mxhosts[i]);
- if (len + slen + 2 > sizeof(buf))
- break;
- if (i > 0)
- {
- *p++ = map->map_coldelim;
- len++;
- }
- (void) sm_strlcpy(p, mxhosts[i], sizeof(buf) - len);
- p += slen;
- len += slen;
- }
- #endif /* _FFR_BESTMX_BETTER_TRUNCATION */
- result = map_rewrite(map, buf, len, av);
- #if _FFR_BESTMX_BETTER_TRUNCATION
- sm_free(buf);
- #endif /* _FFR_BESTMX_BETTER_TRUNCATION */
- return result;
- }
- /*
- ** DNS_GETCANONNAME -- get the canonical name for named host using DNS
- **
- ** This algorithm tries to be smart about wildcard MX records.
- ** This is hard to do because DNS doesn't tell is if we matched
- ** against a wildcard or a specific MX.
- **
- ** We always prefer A & CNAME records, since these are presumed
- ** to be specific.
- **
- ** If we match an MX in one pass and lose it in the next, we use
- ** the old one. For example, consider an MX matching *.FOO.BAR.COM.
- ** A hostname bletch.foo.bar.com will match against this MX, but
- ** will stop matching when we try bletch.bar.com -- so we know
- ** that bletch.foo.bar.com must have been right. This fails if
- ** there was also an MX record matching *.BAR.COM, but there are
- ** some things that just can't be fixed.
- **
- ** Parameters:
- ** host -- a buffer containing the name of the host.
- ** This is a value-result parameter.
- ** hbsize -- the size of the host buffer.
- ** trymx -- if set, try MX records as well as A and CNAME.
- ** statp -- pointer to place to store status.
- ** pttl -- pointer to return TTL (can be NULL).
- **
- ** Returns:
- ** true -- if the host matched.
- ** false -- otherwise.
- */
- bool
- dns_getcanonname(host, hbsize, trymx, statp, pttl)
- char *host;
- int hbsize;
- bool trymx;
- int *statp;
- int *pttl;
- {
- register unsigned char *eom, *ap;
- register char *cp;
- register int n;
- HEADER *hp;
- querybuf answer;
- int ancount, qdcount;
- int ret;
- char **domain;
- int type;
- int ttl = 0;
- char **dp;
- char *mxmatch;
- bool amatch;
- bool gotmx = false;
- int qtype;
- int initial;
- int loopcnt;
- char nbuf[SM_MAX(MAXPACKET, MAXDNAME*2+2)];
- char *searchlist[MAXDNSRCH + 2];
- if (tTd(8, 2))
- sm_dprintf("dns_getcanonname(%s, trymx=%d)\n", host, trymx);
- if ((_res.options & RES_INIT) == 0 && res_init() == -1)
- {
- *statp = EX_UNAVAILABLE;
- return false;
- }
- *statp = EX_OK;
- /*
- ** Initialize domain search list. If there is at least one
- ** dot in the name, search the unmodified name first so we
- ** find "vse.CS" in Czechoslovakia instead of in the local
- ** domain (e.g., vse.CS.Berkeley.EDU). Note that there is no
- ** longer a country named Czechoslovakia but this type of problem
- ** is still present.
- **
- ** Older versions of the resolver could create this
- ** list by tearing apart the host name.
- */
- loopcnt = 0;
- cnameloop:
- /* Check for dots in the name */
- for (cp = host, n = 0; *cp != '\0'; cp++)
- if (*cp == '.')
- n++;
- /*
- ** Build the search list.
- ** If there is at least one dot in name, start with a null
- ** domain to search the unmodified name first.
- ** If name does not end with a dot and search up local domain
- ** tree desired, append each local domain component to the
- ** search list; if name contains no dots and default domain
- ** name is desired, append default domain name to search list;
- ** else if name ends in a dot, remove that dot.
- */
- dp = searchlist;
- if (n > 0)
- *dp++ = "";
- if (n >= 0 && *--cp != '.' && bitset(RES_DNSRCH, _res.options))
- {
- /* make sure there are less than MAXDNSRCH domains */
- for (domain = RES_DNSRCH_VARIABLE, ret = 0;
- *domain != NULL && ret < MAXDNSRCH;
- ret++)
- *dp++ = *domain++;
- }
- else if (n == 0 && bitset(RES_DEFNAMES, _res.options))
- {
- *dp++ = _res.defdname;
- }
- else if (*cp == '.')
- {
- *cp = '\0';
- }
- *dp = NULL;
- /*
- ** Now loop through the search list, appending each domain in turn
- ** name and searching for a match.
- */
- mxmatch = NULL;
- initial = T_A;
- # if NETINET6
- if (InetMode == AF_INET6)
- initial = T_AAAA;
- # endif /* NETINET6 */
- qtype = initial;
- for (dp = searchlist; *dp != NULL; )
- {
- if (qtype == initial)
- gotmx = false;
- if (tTd(8, 5))
- sm_dprintf("dns_getcanonname: trying %s.%s (%s)\n",
- host, *dp,
- # if NETINET6
- qtype == T_AAAA ? "AAAA" :
- # endif /* NETINET6 */
- qtype == T_A ? "A" :
- qtype == T_MX ? "MX" :
- "???");
- errno = 0;
- ret = res_querydomain(host, *dp, C_IN, qtype,
- answer.qb2, sizeof(answer.qb2));
- if (ret <= 0)
- {
- int save_errno = errno;
- if (tTd(8, 7))
- sm_dprintf("\tNO: errno=%d, h_errno=%d\n",
- save_errno, h_errno);
- if (save_errno == ECONNREFUSED || h_errno == TRY_AGAIN)
- {
- /*
- ** the name server seems to be down or broken.
- */
- SM_SET_H_ERRNO(TRY_AGAIN);
- if (**dp == '\0')
- {
- if (*statp == EX_OK)
- *statp = EX_TEMPFAIL;
- goto nexttype;
- }
- *statp = EX_TEMPFAIL;
- if (WorkAroundBrokenAAAA)
- {
- /*
- ** Only return if not TRY_AGAIN as an
- ** attempt with a different qtype may
- ** succeed (res_querydomain() calls
- ** res_query() calls res_send() which
- ** sets errno to ETIMEDOUT if the
- ** nameservers could be contacted but
- ** didn't give an answer).
- */
- if (save_errno != ETIMEDOUT)
- return false;
- }
- else
- return false;
- }
- nexttype:
- if (h_errno != HOST_NOT_FOUND)
- {
- /* might have another type of interest */
- # if NETINET6
- if (qtype == T_AAAA)
- {
- qtype = T_A;
- continue;
- }
- else
- # endif /* NETINET6 */
- if (qtype == T_A && !gotmx &&
- (trymx || **dp == '\0'))
- {
- qtype = T_MX;
- continue;
- }
- }
- /* definite no -- try the next domain */
- dp++;
- qtype = initial;
- continue;
- }
- else if (tTd(8, 7))
- sm_dprintf("\tYES\n");
- /* avoid problems after truncation in tcp packets */
- if (ret > sizeof(answer))
- ret = sizeof(answer);
- SM_ASSERT(ret >= 0);
- /*
- ** Appear to have a match. Confirm it by searching for A or
- ** CNAME records. If we don't have a local domain
- ** wild card MX record, we will accept MX as well.
- */
- hp = (HEADER *) &answer;
- ap = (unsigned char *) &answer + HFIXEDSZ;
- eom = (unsigned char *) &answer + ret;
- /* skip question part of response -- we know what we asked */
- for (qdcount = ntohs((unsigned short) hp->qdcount);
- qdcount--;
- ap += ret + QFIXEDSZ)
- {
- if ((ret = dn_skipname(ap, eom)) < 0)
- {
- if (tTd(8, 20))
- sm_dprintf("qdcount failure (%d)\n",
- ntohs((unsigned short) hp->qdcount));
- *statp = EX_SOFTWARE;
- return false; /* ???XXX??? */
- }
- }
- amatch = false;
- for (ancount = ntohs((unsigned short) hp->ancount);
- --ancount >= 0 && ap < eom;
- ap += n)
- {
- n = dn_expand((unsigned char *) &answer, eom, ap,
- (RES_UNC_T) nbuf, sizeof(nbuf));
- if (n < 0)
- break;
- ap += n;
- GETSHORT(type, ap);
- ap += INT16SZ; /* skip over class */
- GETLONG(ttl, ap);
- GETSHORT(n, ap); /* rdlength */
- switch (type)
- {
- case T_MX:
- gotmx = true;
- if (**dp != '\0' && HasWildcardMX)
- {
- /*
- ** If we are using MX matches and have
- ** not yet gotten one, save this one
- ** but keep searching for an A or
- ** CNAME match.
- */
- if (trymx && mxmatch == NULL)
- mxmatch = *dp;
- continue;
- }
- /*
- ** If we did not append a domain name, this
- ** must have been a canonical name to start
- ** with. Even if we did append a domain name,
- ** in the absence of a wildcard MX this must
- ** still be a real MX match.
- ** Such MX matches are as good as an A match,
- ** fall through.
- */
- /* FALLTHROUGH */
- # if NETINET6
- case T_AAAA:
- # endif /* NETINET6 */
- case T_A:
- /* Flag that a good match was found */
- amatch = true;
- /* continue in case a CNAME also exists */
- continue;
- case T_CNAME:
- if (DontExpandCnames)
- {
- /* got CNAME -- guaranteed canonical */
- amatch = true;
- break;
- }
- if (loopcnt++ > MAXCNAMEDEPTH)
- {
- /*XXX should notify postmaster XXX*/
- message("DNS failure: CNAME loop for %s",
- host);
- if (CurEnv->e_message == NULL)
- {
- char ebuf[MAXLINE];
- (void) sm_snprintf(ebuf,
- sizeof(ebuf),
- "Deferred: DNS failure: CNAME loop for %.100s",
- host);
- CurEnv->e_message =
- sm_rpool_strdup_x(
- CurEnv->e_rpool, ebuf);
- }
- SM_SET_H_ERRNO(NO_RECOVERY);
- *statp = EX_CONFIG;
- return false;
- }
- /* value points at name */
- if ((ret = dn_expand((unsigned char *)&answer,
- eom, ap, (RES_UNC_T) nbuf,
- sizeof(nbuf))) < 0)
- break;
- (void) sm_strlcpy(host, nbuf, hbsize);
- /*
- ** RFC 1034 section 3.6 specifies that CNAME
- ** should point at the canonical name -- but
- ** urges software to try again anyway.
- */
- goto cnameloop;
- default:
- /* not a record of interest */
- continue;
- }
- }
- if (amatch)
- {
- /*
- ** Got a good match -- either an A, CNAME, or an
- ** exact MX record. Save it and get out of here.
- */
- mxmatch = *dp;
- break;
- }
- /*
- ** Nothing definitive yet.
- ** If this was a T_A query and we haven't yet found a MX
- ** match, try T_MX if allowed to do so.
- ** Otherwise, try the next domain.
- */
- # if NETINET6
- if (qtype == T_AAAA)
- qtype = T_A;
- else
- # endif /* NETINET6 */
- if (qtype == T_A && !gotmx && (trymx || **dp == '\0'))
- qtype = T_MX;
- else
- {
- qtype = initial;
- dp++;
- }
- }
- /* if nothing was found, we are done */
- if (mxmatch == NULL)
- {
- if (*statp == EX_OK)
- *statp = EX_NOHOST;
- return false;
- }
- /*
- ** Create canonical name and return.
- ** If saved domain name is null, name was already canonical.
- ** Otherwise append the saved domain name.
- */
- (void) sm_snprintf(nbuf, sizeof(nbuf), "%.*s%s%.*s", MAXDNAME, host,
- *mxmatch == '\0' ? "" : ".",
- MAXDNAME, mxmatch);
- (void) sm_strlcpy(host, nbuf, hbsize);
- if (tTd(8, 5))
- sm_dprintf("dns_getcanonname: %s\n", host);
- *statp = EX_OK;
- /* return only one TTL entry, that should be sufficient */
- if (ttl > 0 && pttl != NULL)
- *pttl = ttl;
- return true;
- }
- #endif /* NAMED_BIND */