/*
* Copyright (c) 1998-2004, 2006, 2010, 2020-2023 Proofpoint, 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 8.205 2013-11-22 20:51:55 ca Exp $ (with name server)")
#else
SM_RCSID("@(#)$Id: domain.c,v 8.205 2013-11-22 20:51:55 ca Exp $ (without name server)")
#endif
#include <sm/sendmail.h>
#if NAMED_BIND
# include <arpa/inet.h>
# include "sm_resolve.h"
# if DANE
# include <tls.h>
# ifndef SM_NEG_TTL
# define SM_NEG_TTL 60 /* "negative" TTL */
# endif
# endif
#if USE_EAI
#include <unicode/uidna.h>
#endif
# ifndef MXHOSTBUFSIZE
# define MXHOSTBUFSIZE (128 * MAXMXHOSTS)
# endif
static char MXHostBuf[MXHOSTBUFSIZE];
# if (MXHOSTBUFSIZE < 2) || (MXHOSTBUFSIZE >= INT_MAX/2)
ERROR: _MXHOSTBUFSIZE is out of range
# endif
# ifndef MAXDNSRCH
# define MAXDNSRCH 6 /* number of possible domains to search */
# endif
# ifndef RES_DNSRCH_VARIABLE
# define RES_DNSRCH_VARIABLE _res.dnsrch
# endif
# ifndef HFIXEDSZ
# define HFIXEDSZ 12 /* sizeof(HEADER) */
# endif
# define MAXCNAMEDEPTH 10 /* maximum depth of CNAME recursion */
# if defined(__RES) && (__RES >= 19940415)
# define RES_UNC_T char *
# else
# define RES_UNC_T unsigned char *
# endif
static int mxrand __P((char *));
static int fallbackmxrr __P((int, unsigned short *, char **));
# if DANE
static void tlsa_rr_print __P((const unsigned char *, unsigned int));
static void
tlsa_rr_print(rr, len)
const unsigned char *rr;
unsigned int len;
{
unsigned int i, l;
if (!tTd(8, 2))
return;
sm_dprintf("len=%u, %02x-%02x-%02x",
len, (int)rr[0], (int)rr[1], (int)rr[2]);
l = tTd(8, 8) ? len : 4;
for (i = 3; i < l; i++)
sm_dprintf(":%02X", (int)rr[i]);
sm_dprintf("\n");
}
/*
** TLSA_RR_CMP -- Compare two TLSA RRs
**
** Parameters:
** rr1 -- TLSA RR (entry to be added)
** l1 -- length of rr1
** rr2 -- TLSA RR
** l2 -- length of rr2
**
** Returns:
** 0: rr1 == rr2
** 1: rr1 is unsupported
*/
static int tlsa_rr_cmp __P((unsigned char *, int, unsigned char *, int));
static int
tlsa_rr_cmp(rr1, l1, rr2, l2)
unsigned char *rr1;
int l1;
unsigned char *rr2;
int l2;
{
/* temporary #if while investigating the implications of the alternative */
#if FULL_COMPARE
unsigned char r1, r2;
int cmp;
#endif /* FULL_COMPARE */
SM_REQUIRE(NULL != rr1);
SM_REQUIRE(NULL != rr2);
SM_REQUIRE(l1 > 3);
SM_REQUIRE(l2 > 3);
#if FULL_COMPARE
/*
** certificate usage
** 3: cert/fp must match
** 2: cert/fp must be trust anchor
*/
/* preference[]: lower value: higher preference */
r1 = rr1[0];
r2 = rr2[0];
if (r1 != r2)
{
int preference[] = { 3, 2, 1, 0 };
SM_ASSERT(r1 <= SM_ARRAY_SIZE(preference));
SM_ASSERT(r2 <= SM_ARRAY_SIZE(preference));
return preference[r1] - preference[r2];
}
/*
** selector:
** 0: full cert
** 1: fp
*/
r1 = rr1[1];
r2 = rr2[1];
if (r1 != r2)
{
int preference[] = { 1, 0 };
SM_ASSERT(r1 <= SM_ARRAY_SIZE(preference));
SM_ASSERT(r2 <= SM_ARRAY_SIZE(preference));
return preference[r1] - preference[r2];
}
/*
** matching type:
** 0 -- Exact match
** 1 -- SHA-256 hash
** 2 -- SHA-512 hash
*/
r1 = rr1[2];
r2 = rr2[2];
if (r1 != r2)
{
int preference[] = { 2, 0, 1 };
SM_ASSERT(r1 <= SM_ARRAY_SIZE(preference));
SM_ASSERT(r2 <= SM_ARRAY_SIZE(preference));
return preference[r1] - preference[r2];
}
/* not the same length despite the same type? */
if (l1 != l2)
return 1;
cmp = memcmp(rr1, rr2, l1);
if (0 == cmp)
return 0;
return 1;
#else /* FULL_COMPARE */
/* identical? */
if (l1 == l2 && 0 == memcmp(rr1, rr2, l1))
return 0;
/* new entry is unsupported? -> append */
if (TLSA_UNSUPP == dane_tlsa_chk(rr1, l1, "", false))
return 1;
/* current entry is unsupported? -> insert new one */
if (TLSA_UNSUPP == dane_tlsa_chk(rr2, l2, "", false))
return -1;
/* default: preserve order */
return 1;
#endif /* FULL_COMPARE */
}
/*
** TLSAINSERT -- Insert a TLSA RR
**
** Parameters:
** dane_tlsa -- dane_tlsa entry
** rr -- TLSA RR
** pn -- (point to) number of entries
**
** Returns:
** SM_SUCCESS: rr inserted
** SM_NOTDONE: rr not inserted: exists
** SM_FULL: rr not inserted: no space left
*/
static int tlsainsert __P((dane_tlsa_P, RESOURCE_RECORD_T *, int *));
static int
tlsainsert(dane_tlsa, rr, pn)
dane_tlsa_P dane_tlsa;
RESOURCE_RECORD_T *rr;
int *pn;
{
int i, l1, ret;
unsigned char *r1;
SM_ASSERT(pn != NULL);
SM_ASSERT(*pn <= MAX_TLSA_RR);
r1 = rr->rr_u.rr_data;
l1 = rr->rr_size;
ret = SM_SUCCESS;
for (i = 0; i < *pn; i++)
{
int r, j;
r = tlsa_rr_cmp(r1, l1, dane_tlsa->dane_tlsa_rr[i],
dane_tlsa->dane_tlsa_len[i]);
if (0 == r)
{
if (tTd(8, 80))
sm_dprintf("func=tlsainsert, i=%d, n=%d, status=exists\n", i, *pn);
ret = SM_NOTDONE;
goto done;
}
if (r > 0)
continue;
if (*pn + 1 >= MAX_TLSA_RR)
{
j = MAX_TLSA_RR - 1;
SM_FREE(dane_tlsa->dane_tlsa_rr[j]);
dane_tlsa->dane_tlsa_len[j] = 0;
}
else
(*pn)++;
for (j = MAX_TLSA_RR - 2; j >= i; j--)
{
dane_tlsa->dane_tlsa_rr[j + 1] = dane_tlsa->dane_tlsa_rr[j];
dane_tlsa->dane_tlsa_len[j + 1] = dane_tlsa->dane_tlsa_len[j];
}
SM_ASSERT(i < MAX_TLSA_RR);
dane_tlsa->dane_tlsa_rr[i] = r1;
dane_tlsa->dane_tlsa_len[i] = l1;
if (tTd(8, 80))
sm_dprintf("func=tlsainsert, i=%d, n=%d, status=inserted\n", i, *pn);
goto added;
}
if (*pn + 1 <= MAX_TLSA_RR)
{
dane_tlsa->dane_tlsa_rr[*pn] = r1;
dane_tlsa->dane_tlsa_len[*pn] = l1;
(*pn)++;
if (tTd(8, 80))
sm_dprintf("func=tlsainsert, n=%d, status=appended\n", *pn);
}
else
{
if (tTd(8, 80))
sm_dprintf("func=tlsainsert, n=%d, status=full\n", *pn);
return SM_FULL;
}
added:
/* hack: instead of copying the data, just "take it over" */
rr->rr_u.rr_data = NULL;
done:
return ret;
}
/*
** TLSAADD -- add TLSA records to dane_tlsa entry
**
** Parameters:
** name -- key for stab entry (for debugging output)
** dr -- DNS reply
** dane_tlsa -- dane_tlsa entry
** dnsrc -- DNS lookup return code (h_errno)
** nr -- current number of TLSA records in dane_tlsa entry
** pttl -- (pointer to) TTL (in/out)
** level -- recursion level (CNAMEs)
**
** Returns:
** new number of TLSA records
**
** NOTE: the array for TLSA RRs could be "full" which is not
** handled well (yet).
*/
static int tlsaadd __P((const char *, DNS_REPLY_T *, dane_tlsa_P, int, int,
unsigned int *, int));
static int
tlsaadd(name, dr, dane_tlsa, dnsrc, nr, pttl, level)
const char *name;
DNS_REPLY_T *dr;
dane_tlsa_P dane_tlsa;
int dnsrc;
int nr;
unsigned int *pttl;
int level;
{
RESOURCE_RECORD_T *rr;
unsigned int ttl;
int nprev;
if (dnsrc != 0)
{
if (tTd(8, 2))
sm_dprintf("tlsaadd, name=%s, prev=%d, dnsrc=%d\n",
name, dane_tlsa->dane_tlsa_dnsrc, dnsrc);
/* check previous error and keep the "most important" one? */
dane_tlsa->dane_tlsa_dnsrc = dnsrc;
# if DNSSEC_TEST
if (tTd(8, 110))
*pttl = tTdlevel(8)-110; /* how to make this an option? */
else
# endif
/* "else" in #if code above */
*pttl = SM_NEG_TTL;
return nr;
}
if (dr == NULL)
return nr;
if (dr->dns_r_h.ad != 1 && Dane == DANE_SECURE) /* not secure? */
return nr;
ttl = *pttl;
/* first: try to find TLSA records */
nprev = nr;
for (rr = dr->dns_r_head; rr != NULL; rr = rr->rr_next)
{
int tlsa_chk, r;
if (rr->rr_type != T_TLSA)
{
if (rr->rr_type != T_CNAME && tTd(8, 8))
sm_dprintf("tlsaadd: name=%s, type=%s\n", name,
dns_type_to_string(rr->rr_type));
continue;
}
tlsa_chk = dane_tlsa_chk(rr->rr_u.rr_data, rr->rr_size, name,
true);
if (TLSA_UNSUPP == tlsa_chk)
TLSA_SET_FL(dane_tlsa, TLSAFLUNS);
if (!TLSA_IS_VALID(tlsa_chk))
continue;
if (TLSA_IS_SUPPORTED(tlsa_chk))
TLSA_SET_FL(dane_tlsa, TLSAFLSUP);
/*
** Note: rr_u.rr_data might be NULL after tlsainsert()
** for nice debug output: print the data into a string
** and then use it after tlsainsert().
*/
if (tTd(8, 2))
{
sm_dprintf("tlsaadd: name=%s, nr=%d, ", name, nr);
tlsa_rr_print(rr->rr_u.rr_data, rr->rr_size);
}
r = tlsainsert(dane_tlsa, rr, &nr);
if (SM_FULL == r)
TLSA_SET_FL(dane_tlsa, TLSAFL2MANY);
if (tTd(8, 2))
sm_dprintf("tlsainsert=%d, nr=%d\n", r, nr);
/* require some minimum TTL? */
if (ttl > rr->rr_ttl && rr->rr_ttl > 0)
ttl = rr->rr_ttl;
}
if (tTd(8, 2))
{
unsigned int ui;
SM_ASSERT(nr <= MAX_TLSA_RR);
for (ui = 0; ui < (unsigned int)nr; ui++)
{
sm_dprintf("tlsaadd: name=%s, ui=%u, ", name, ui);
tlsa_rr_print(dane_tlsa->dane_tlsa_rr[ui],
dane_tlsa->dane_tlsa_len[ui]);
}
}
if (TLSA_IS_FL(dane_tlsa, TLSAFL2MANY))
{
if (tTd(8, 20))
sm_dprintf("tlsaadd: name=%s, rr=%p, nr=%d, toomany=%d\n", name, rr, nr, TLSA_IS_FL(dane_tlsa, TLSAFL2MANY));
}
/* second: check for CNAME records, but only if no TLSA RR was added */
for (rr = dr->dns_r_head; rr != NULL && nprev == nr; rr = rr->rr_next)
{
DNS_REPLY_T *drc;
int err, herr;
if (rr->rr_type != T_CNAME)
continue;
if (level > 1)
{
if (tTd(8, 2))
sm_dprintf("tlsaadd: name=%s, CNAME=%s, level=%d\n",
name, rr->rr_u.rr_txt, level);
continue;
}
drc = dns_lookup_int(rr->rr_u.rr_txt, C_IN, T_TLSA, 0, 0,
Dane == DANE_SECURE ? SM_RES_DNSSEC : 0,
RR_RAW, &err, &herr);
if (tTd(8, 2))
sm_dprintf("tlsaadd: name=%s, CNAME=%s, level=%d, dr=%p, ad=%d, err=%d, herr=%d\n",
name, rr->rr_u.rr_txt, level,
(void *)drc, drc != NULL ? drc->dns_r_h.ad : -1,
err, herr);
nprev = nr = tlsaadd(name, drc, dane_tlsa, herr, nr, pttl,
level + 1);
dns_free_data(drc);
drc = NULL;
}
if (TLSA_IS_FL(dane_tlsa, TLSAFLUNS) &&
!TLSA_IS_FL(dane_tlsa, TLSAFLSUP) && LogLevel > 9)
{
sm_syslog(LOG_NOTICE, NOQID,
"TLSA=%s, records=%d%s",
name, nr, ONLYUNSUPTLSARR);
}
*pttl = ttl;
return nr;
}
/*
** GETTLSA -- get TLSA records for named host using DNS
**
** Parameters:
** host -- host
** name -- name for stab entry key (if NULL: host)
** pste -- (pointer to) stab entry (output)
** flags -- TLSAFL*
** mxttl -- TTL of MX (or host)
** port -- port number used in TLSA queries (_PORT._tcp.)
**
** Returns:
** The number of TLSA records found.
** <0 if there is an internal failure.
**
** Side effects:
** Enters TLSA RRs into stab().
** If the DNS lookup fails temporarily, an "empty" entry is
** created with that DNS error code.
*/
int
gettlsa(host, name, pste, flags, mxttl, port)
char *host;
char *name;
STAB **pste;
unsigned long flags;
unsigned int mxttl;
unsigned int port;
{
DNS_REPLY_T *dr;
dane_tlsa_P dane_tlsa;
STAB *ste;
time_t now;
unsigned int ttl;
int n_rrs, len, err, herr;
bool isrname, expired;
char nbuf[MAXDNAME];
char key[MAXDNAME];
SM_REQUIRE(host != NULL);
if (pste != NULL)
*pste = NULL;
if ('\0' == *host)
return 0;
expired = false;
isrname = NULL == name;
if (isrname)
name = host;
/*
** If host->MX lookup was not secure then do not look up TLSA RRs.
** Note: this is currently a hack: TLSAFLADMX is used as input flag,
** it is (SHOULD!) NOT stored in dane_tlsa->dane_tlsa_flags
*/
if (DANE_SECURE == Dane && 0 == (TLSAFLADMX & flags) &&
0 != (TLSAFLNEW & flags))
{
if (tTd(8, 2))
sm_dprintf("gettlsa: host=%s, flags=%#lx, no ad but Dane=Secure\n",
host, flags);
return 0;
}
now = 0;
n_rrs = 0;
dr = NULL;
dane_tlsa = NULL;
len = strlen(name);
if (len > 1 && name[len - 1] == '.')
{
len--;
name[len] = '\0';
}
else
len = -1;
if (0 == port || tTd(66, 101))
port = 25;
(void) sm_snprintf(key, sizeof(key), "_%u.%s", port, name);
ste = stab(key, ST_TLSA_RR, ST_FIND);
if (tTd(8, 2))
sm_dprintf("gettlsa: host=%s, %s, ste=%p, pste=%p, flags=%#lx, port=%d\n",
host, isrname ? "" : name, (void *)ste, (void *)pste,
flags, port);
if (ste != NULL)
dane_tlsa = ste->s_tlsa;
#if 0
// /* Do not reload TLSA RRs if the MX RRs were not securely retrieved. */
// if (pste != NULL
// && dane_tlsa != NULL && TLSA_IS_FL(dane_tlsa, TLSAFLNOADMX)
// && DANE_SECURE == Dane)
// goto end;
#endif
if (ste != NULL)
{
SM_ASSERT(dane_tlsa != NULL);
now = curtime();
if (tTd(8, 20))
sm_dprintf("gettlsa: host=%s, found-ste=%p, ste_flags=%#lx, expired=%d\n", host, ste, ste->s_tlsa->dane_tlsa_flags, dane_tlsa->dane_tlsa_exp <= now);
if (dane_tlsa->dane_tlsa_exp <= now
&& 0 == (TLSAFLNOEXP & flags))
{
dane_tlsa_clr(dane_tlsa);
expired = true;
}
else
{
n_rrs = dane_tlsa->dane_tlsa_n;
goto end;
}
}
/* get entries if none exist yet? */
if ((0 == (TLSAFLNEW & flags)) && !expired)
goto end;
if (dane_tlsa == NULL)
{
dane_tlsa = (dane_tlsa_P) sm_malloc(sizeof(*dane_tlsa));
if (dane_tlsa == NULL)
{
n_rrs = -ENOMEM;
goto end;
}
memset(dane_tlsa, '\0', sizeof(*dane_tlsa));
}
/* There are flags to store -- just set those, do nothing else. */
if (TLSA_STORE_FL(flags))
{
dane_tlsa->dane_tlsa_flags = flags;
ttl = mxttl > 0 ? mxttl: SM_DEFAULT_TTL;
goto done;
}
(void) sm_snprintf(nbuf, sizeof(nbuf), "_%u._tcp.%s", port, host);
dr = dns_lookup_int(nbuf, C_IN, T_TLSA, 0, 0,
(TLSAFLADMX & flags) ? SM_RES_DNSSEC : 0,
RR_RAW, &err, &herr);
if (tTd(8, 2))
{
#if 0
/* disabled -- what to do with these two counters? log them "somewhere"? */
// if (NULL != dr && tTd(8, 12))
// {
// RESOURCE_RECORD_T *rr;
// unsigned int ntlsarrs, usable;
//
// ntlsarrs = usable = 0;
// for (rr = dr->dns_r_head; rr != NULL; rr = rr->rr_next)
// {
// int tlsa_chk;
//
// if (rr->rr_type != T_TLSA)
// continue;
// ++ntlsarrs;
// tlsa_chk = dane_tlsa_chk(rr->rr_u.rr_data,
// rr->rr_size, name, false);
// if (TLSA_IS_SUPPORTED(tlsa_chk))
// ++usable;
//
// }
// sm_dprintf("gettlsa: host=%s, ntlsarrs=%u, usable\%u\n", host, ntlsarrs, usable);
// }
#endif /* 0 */
sm_dprintf("gettlsa: host=%s, dr=%p, ad=%d, err=%d, herr=%d\n",
host, (void *)dr,
dr != NULL ? dr->dns_r_h.ad : -1, err, herr);
}
ttl = UINT_MAX;
n_rrs = tlsaadd(key, dr, dane_tlsa, herr, n_rrs, &ttl, 0);
/* no valid entries found? */
if (n_rrs == 0 && !TLSA_RR_TEMPFAIL(dane_tlsa))
{
if (tTd(8, 2))
sm_dprintf("gettlsa: host=%s, n_rrs=%d, herr=%d, status=NOT_ADDED\n",
host, n_rrs, dane_tlsa->dane_tlsa_dnsrc);
goto cleanup;
}
done:
dane_tlsa->dane_tlsa_n = n_rrs;
if (!isrname)
{
SM_FREE(dane_tlsa->dane_tlsa_sni);
dane_tlsa->dane_tlsa_sni = sm_strdup(host);
}
if (NULL == ste)
{
ste = stab(key, ST_TLSA_RR, ST_ENTER);
if (NULL == ste)
goto error;
}
ste->s_tlsa = dane_tlsa;
if (now == 0)
now = curtime();
dane_tlsa->dane_tlsa_exp = now + SM_MIN(ttl, SM_DEFAULT_TTL);
dns_free_data(dr);
dr = NULL;
goto end;
error:
if (tTd(8, 2))
sm_dprintf("gettlsa: host=%s, key=%s, status=error\n", host, key);
n_rrs = -1;
cleanup:
if (NULL == ste)
dane_tlsa_free(dane_tlsa);
dns_free_data(dr);
dr = NULL;
end:
if (pste != NULL && ste != NULL)
*pste = ste;
if (len > 0)
host[len] = '.';
return n_rrs;
}
# endif /* DANE */
/*
** 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 (SM_IS_EMPTY(host))
return 0;
# endif /* 0 */
if (NumFallbackMXHosts > 0 && renew > curtime())
return NumFallbackMXHosts;
/*
** For DANE we need to invoke getmxrr() to get the TLSA RRs.
** Hack: don't do that if its not a FQHN (e.g., [localhost])
** This also triggers for IPv4 addresses, but not IPv6!
*/
if (host[0] == '[' && (!Dane || strchr(host, '.') == NULL))
{
fbhosts[0] = host;
NumFallbackMXHosts = 1;
}
else
{
/* free old data */
for (i = 0; i < NumFallbackMXHosts; i++)
sm_free(fbhosts[i]);
/*
** Get new data.
** Note: passing 0 as port is not correct but we cannot
** determine the port number as there is no mailer.
*/
NumFallbackMXHosts = getmxrr(host, fbhosts, NULL,
# if DANE
(DANE_SECURE == Dane) ? ISAD :
# endif
0, &rcode, &ttl, 0, NULL);
renew = curtime() + ttl;
for (i = 0; i < NumFallbackMXHosts; i++)
fbhosts[i] = newstr(fbhosts[i]);
}
if (NumFallbackMXHosts == NULLMX)
NumFallbackMXHosts = 0;
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;
}
# if USE_EAI
/*
** HN2ALABEL -- convert hostname in U-label format to A-label format
**
** Parameters:
** hostname -- hostname in U-label format
**
** Returns:
** hostname in A-label format in a local static buffer.
** It must be copied before the function is called again.
*/
const char *
hn2alabel(hostname)
const char *hostname;
{
UErrorCode error = U_ZERO_ERROR;
UIDNAInfo info = UIDNA_INFO_INITIALIZER;
UIDNA *idna;
static char buf[MAXNAME_I]; /* XXX ??? */
if (str_is_print(hostname))
return hostname;
idna = uidna_openUTS46(UIDNA_NONTRANSITIONAL_TO_ASCII, &error);
(void) uidna_nameToASCII_UTF8(idna, hostname, strlen(hostname),
buf, sizeof(buf) - 1,
&info, &error);
uidna_close(idna);
return buf;
}
# endif /* USE_EAI */
/*
** GETMXRR -- get MX resource records for a domain
**
** Parameters:
** host -- the name of the host to MX [must be x]
** 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.
** flags -- flags:
** DROPLOCALHOST -- If true, all MX records less preferred
** than the local host (as determined by $=w) will
** be discarded.
** TRYFALLBACK -- add also fallback MX host?
** ISAD -- host lookup was secure?
** rcode -- a pointer to an EX_ status code.
** pttl -- pointer to return TTL (can be NULL).
** port -- port number used in TLSA queries (_PORT._tcp.)
** pad -- (output parameter, pointer to) AD flag (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, flags, rcode, pttl, port, pad)
char *host;
char **mxhosts;
unsigned short *mxprefs;
unsigned int flags;
int *rcode;
int *pttl;
int port;
int *pad;
{
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;
bool ad;
bool seennullmx = false;
extern int res_query __P((const char *, int, int, u_char *, int));
extern int res_search __P((const char *, int, int , u_char *, int));
# if DANE
bool cname2mx;
char qname[MAXNAME]; /* EAI: copy of host: ok? */
unsigned long old_options = 0;
# endif
if (tTd(8, 2))
sm_dprintf("getmxrr(%s, droplocalhost=%d, flags=%X, port=%d)\n",
host, (flags & DROPLOCALHOST) != 0, flags, port);
ad = (flags & ISAD) != 0;
*rcode = EX_OK;
if (pttl != NULL)
*pttl = SM_DEFAULT_TTL;
if (*host == '\0')
return 0;
# if DANE
cname2mx = false;
qname[0] = '\0';
old_options = _res.options;
if (ad)
_res.options |= SM_RES_DNSSEC;
# endif
if ((fallbackMX != NULL && (flags & DROPLOCALHOST) != 0 &&
wordinclass(fallbackMX, 'w')) || (flags & TRYFALLBACK) == 0)
{
/* 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 DANE
/*
** NOTE: This only works if nocanonify is used,
** otherwise the name is already rewritten.
*/
/* always or only when "needed"? */
if (DANE_ALWAYS == Dane || (ad && DANE_SECURE == Dane))
(void) sm_strlcpy(qname, host, sizeof(qname));
# endif /* DANE */
# if USE_EAI
if (!str_is_print(host))
{
/* XXX memory leak? */
host = sm_rpool_strdup_x(CurEnv->e_rpool, hn2alabel(host));
}
# endif /* USE_EAI */
/*
** 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;
# if DNSSEC_TEST
if (tTd(8, 110))
resfunc = tstdns_search;
# endif
errno = 0;
hp = (HEADER *)&answer;
n = (*resfunc)(host, C_IN, T_MX, (unsigned char *) &answer,
sizeof(answer));
if (n < 0)
{
if (tTd(8, 1))
# if DNSSEC_TEST
sm_dprintf("getmxrr: res_search(%s) failed (errno=%d (%s), h_errno=%d (%s))\n",
host, errno, strerror(errno),
h_errno, herrno2txt(h_errno));
# else
sm_dprintf("getmxrr: res_search(%s) failed, h_errno=%d\n",
host, h_errno);
# endif
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 returns failure w/ h_errno=0 */
# endif
/* 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 */
nmx = fallbackmxrr(nmx, prefs, mxhosts);
goto done;
}
/* 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 */
goto error;
}
ad = ad && hp->ad;
if (tTd(8, 2))
sm_dprintf("getmxrr(%s), hp=%p, ad=%d\n", host, (void*)hp, ad);
if (pad != NULL)
*pad = ad;
/* avoid problems after truncation in tcp packets */
if (n > sizeof(answer))
n = sizeof(answer);
/* find first satisfactory 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 DANE
if (type == T_CNAME)
cname2mx = true;
# endif
if (type != T_MX)
{
if ((tTd(8, 8) || _res.options & RES_DEBUG)
# if DANE
&& type != T_RRSIG
# endif
)
sm_dprintf("unexpected answer type %s, size %d\n",
dns_type_to_string(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);
/* Support for RFC7505 "MX 0 ." */
if (pref == 0 && *bp == '\0')
seennullmx = true;
if (wordinclass(bp, 'w'))
{
if (tTd(8, 3))
sm_dprintf("found localhost (%s) in MX list, pref=%d\n",
bp, pref);
if ((flags & DROPLOCALHOST) != 0)
{
if (!seenlocal || pref < localpref)
localpref = pref;
seenlocal = true;
continue;
}
weight[nmx] = 0;
}
else
weight[nmx] = mxrand(bp);
prefs[nmx] = pref;
mxhosts[nmx++] = bp;
# if DANE
if (CHK_DANE(Dane) && port >= 0)
{
int nrr;
unsigned long flags;
flags = TLSAFLNEW;
if (pad != NULL && *pad)
flags |= TLSAFLADMX;
if (tTd(8, 20))
sm_dprintf("getmxrr: 1: host=%s, mx=%s, flags=%#lx\n", host, bp, flags);
nrr = gettlsa(bp, NULL, NULL, flags, ttl, port);
/* Only check qname if no TLSA RRs were found */
if (0 == nrr && cname2mx && '\0' != qname[0] &&
strcmp(qname, bp))
{
if (tTd(8, 20))
sm_dprintf("getmxrr: 2: host=%s, qname=%s, flags=%#lx\n", host, qname, flags);
gettlsa(qname, bp, NULL, flags, ttl, port);
/* XXX is this the right ad flag? */
}
}
# endif
/*
** Note: n can be 0 for something like:
** host MX 0 .
** See RFC 7505
*/
bp += n;
if (0 == n || bp[-1] != '.')
{
*bp++ = '.';
n++;
}
*bp++ = '\0';
if (buflen < n + 1)
{
/* don't want to wrap buflen */
break;
}
buflen -= n + 1;
}
/* Support for RFC7505 "MX 0 ." */
if (seennullmx && nmx == 1)
{
if (tTd(8, 4))
sm_dprintf("getmxrr: Null MX record found, domain doesn't accept mail (RFC7505)\n");
*rcode = EX_UNAVAILABLE;
return NULLMX;
}
/* 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_STRCASEEQ(mxhosts[i], mxhosts[i + 1]))
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;
goto error;
}
# 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;
goto error;
}
# endif /* NETINET6 */
}
}
if (h == NULL)
{
*rcode = EX_CONFIG;
syserr("MX list for %s points back to %s",
host, MyHostName);
goto error;
}
# if NETINET6
freehostent(h);
h = NULL;
# endif
}
if (strlen(host) >= sizeof(MXHostBuf))
{
*rcode = EX_CONFIG;
syserr("Host name %s too long",
shortenstring(host, MAXSHORTSTR));
goto error;
}
(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
/* 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
{
# if USE_EAI
char *hn;
hn = MXHostBuf + 1;
if (!str_is_print(hn))
{
const char *ahn;
ahn = hn2alabel(hn);
if (strlen(ahn) >= sizeof(MXHostBuf) - 1)
{
*rcode = EX_CONFIG;
syserr("Encoded host name %s too long",
shortenstring(ahn, MAXSHORTSTR));
goto error;
}
(void) sm_strlcpy(hn, ahn, sizeof(MXHostBuf) - 1);
}
# endif /* USE_EAI */
trycanon = true;
mxhosts[0]++;
}
}
}
if (trycanon &&
(n = getcanonname(mxhosts[0], sizeof(MXHostBuf) - 2, false,
pttl)) != HOST_NOTFOUND)
{
/* XXX MXHostBuf == "" ? is that possible? */
bp = &MXHostBuf[strlen(MXHostBuf)];
if (bp[-1] != '.')
{
*bp++ = '.';
*bp = '\0';
}
nmx = 1;
# if DANE
if (tTd(8, 3))
sm_dprintf("getmxrr=%s, getcanonname=%d\n",
mxhosts[0], n);
if (CHK_DANE(Dane) && port >= 0)
{
int nrr;
unsigned long flags;
unsigned int cttl;
if (pttl != NULL)
cttl = *pttl;
else if (ttl > 0)
cttl = ttl;
else
cttl = SM_DEFAULT_TTL;
flags = TLSAFLNEW;
if (ad && HOST_SECURE == n)
{
flags |= TLSAFLADMX;
if (pad != NULL)
*pad = ad;
}
if (TTD(8, 20))
sm_dprintf("getmxrr: 3: host=%s, mx=%s, flags=%#lx, ad=%d\n",
host, mxhosts[0], flags, ad);
nrr = gettlsa(mxhosts[0], NULL, NULL, flags,
cttl, port);
/*
** Only check qname if no TLSA RRs were found
** XXX: what about (temp) DNS errors?
*/
if (0 == nrr && '\0' != qname[0] &&
strcmp(qname, mxhosts[0]))
{
gettlsa(qname, mxhosts[0], NULL, flags,
cttl, port);
if (tTd(8, 20))
sm_dprintf("getmxrr: 4: host=%s, qname=%s, flags=%#lx\n", host, qname, flags);
/* XXX is this the right ad flag? */
}
}
# endif
}
}
/* if we have a default lowest preference, include that */
if (fallbackMX != NULL && !seenlocal)
{
/* TODO: DNSSEC status of fallbacks */
nmx = fallbackmxrr(nmx, prefs, mxhosts);
}
done:
# if DANE
_res.options = old_options;
# endif
return nmx;
error:
# if DANE
_res.options = old_options;
# endif
return -1;
}
/*
** 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
char *p;
char buf[PSBUFSIZE / 2];
# endif
_res.options &= ~(RES_DNSRCH|RES_DEFNAMES);
nmx = getmxrr(name, mxhosts, NULL, 0, statp, NULL, -1, 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
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:
** >0 -- if the host was found.
** 0 -- otherwise.
*/
int
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, ret, type, qtype, initial, loopcnt, ttl, sli;
char **domain;
char *dp;
char *mxmatch;
bool amatch, gotmx, ad;
char nbuf[SM_MAX(MAXPACKET, MAXDNAME*2+2)];
# if DNSSEC_TEST
# define ADDSL 1 /* NameSearchList may add another entry to searchlist! */
# else
# define ADDSL 0
# endif
char *searchlist[MAXDNSRCH + 2 + ADDSL];
# define SLSIZE SM_ARRAY_SIZE(searchlist)
int (*resqdomain) __P((const char *, const char *, int, int, unsigned char *, int));
# if DANE
unsigned long old_options = 0;
# endif
ttl = 0;
gotmx = false;
ad = true;
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 HOST_NOTFOUND;
}
# if DANE
old_options = _res.options;
if (DANE_SECURE == Dane)
_res.options |= SM_RES_DNSSEC;
# endif
*statp = EX_OK;
resqdomain = res_querydomain;
# if DNSSEC_TEST
if (tTd(8, 110))
resqdomain = tstdns_querydomain;
# endif
/*
** 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.
*/
sli = 0;
if (n > 0)
searchlist[sli++] = "";
# if DNSSEC_TEST
if (NameSearchList != NULL)
{
SM_ASSERT(sli < SLSIZE);
searchlist[sli++] = NameSearchList;
}
# endif
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 && sli < SLSIZE;
ret++)
searchlist[sli++] = *domain++;
}
else if (n == 0 && bitset(RES_DEFNAMES, _res.options))
{
SM_ASSERT(sli < SLSIZE);
searchlist[sli++] = _res.defdname;
}
else if (*cp == '.')
{
*cp = '\0';
}
SM_ASSERT(sli < SLSIZE);
searchlist[sli] = 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
qtype = initial;
for (sli = 0; sli < SLSIZE; )
{
dp = searchlist[sli];
if (NULL == dp)
break;
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
qtype == T_A ? "A" :
qtype == T_MX ? "MX" :
"???");
errno = 0;
hp = (HEADER *) &answer;
ret = (*resqdomain)(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)
goto error;
}
else
goto error;
}
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 */
sli++;
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.
*/
ap = (unsigned char *) &answer + HFIXEDSZ;
eom = (unsigned char *) &answer + ret;
if (0 == hp->ad)
ad = false;
/* 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;
goto error;
}
}
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
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;
goto error;
}
/* 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
if (qtype == T_A && !gotmx && (trymx || *dp == '\0'))
qtype = T_MX;
else
{
qtype = initial;
sli++;
}
}
/* if nothing was found, we are done */
if (mxmatch == NULL)
{
if (*statp == EX_OK)
*statp = EX_NOHOST;
goto error;
}
/*
** 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;
# if DANE
_res.options = old_options;
# endif
return ad ? HOST_SECURE : HOST_OK;
error:
# if DANE
_res.options = old_options;
# endif
return HOST_NOTFOUND;
}
#endif /* NAMED_BIND */