Github
/
FTL
mirror of
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity
FTL/src/dnsmasq/dnssec.c

2266 lines
64 KiB
C
Raw Blame History

/* dnssec.c is Copyright (c) 2012 Giovanni Bajo <rasky@develer.com>
and Copyright (c) 2012-2023 Simon Kelley
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 dated June, 1991, or
(at your option) version 3 dated 29 June, 2007.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "dnsmasq.h"
#ifdef HAVE_DNSSEC
#define SERIAL_UNDEF -100
#define SERIAL_EQ 0
#define SERIAL_LT -1
#define SERIAL_GT 1
/* Input in presentation format */
static int count_labels(char *name)
{
int i;
char *p;
if (*name == 0)
return 0;
for (p = name, i = 0; *p; p++)
if (*p == '.')
i++;
/* Don't count empty first label. */
return *name == '.' ? i : i+1;
}
/* Implement RFC1982 wrapped compare for 32-bit numbers */
static int serial_compare_32(u32 s1, u32 s2)
{
if (s1 == s2)
return SERIAL_EQ;
if ((s1 < s2 && (s2 - s1) < (1UL<<31)) ||
(s1 > s2 && (s1 - s2) > (1UL<<31)))
return SERIAL_LT;
if ((s1 < s2 && (s2 - s1) > (1UL<<31)) ||
(s1 > s2 && (s1 - s2) < (1UL<<31)))
return SERIAL_GT;
return SERIAL_UNDEF;
}
/* Called at startup. If the timestamp file is configured and exists, put its mtime on
timestamp_time. If it doesn't exist, create it, and set the mtime to 1-1-2015.
return -1 -> Cannot create file.
0 -> not using timestamp, or timestamp exists and is in past.
1 -> timestamp exists and is in future.
*/
static time_t timestamp_time;
int setup_timestamp(void)
{
struct stat statbuf;
daemon->back_to_the_future = 0;
if (!daemon->timestamp_file)
return 0;
if (stat(daemon->timestamp_file, &statbuf) != -1)
{
timestamp_time = statbuf.st_mtime;
check_and_exit:
if (difftime(timestamp_time, time(0)) <= 0)
{
/* time already OK, update timestamp, and do key checking from the start. */
if (utimes(daemon->timestamp_file, NULL) == -1)
my_syslog(LOG_ERR, _("failed to update mtime on %s: %s"), daemon->timestamp_file, strerror(errno));
daemon->back_to_the_future = 1;
return 0;
}
return 1;
}
if (errno == ENOENT)
{
/* NB. for explanation of O_EXCL flag, see comment on pidfile in dnsmasq.c */
int fd = open(daemon->timestamp_file, O_WRONLY | O_CREAT | O_NONBLOCK | O_EXCL, 0666);
if (fd != -1)
{
struct timeval tv[2];
close(fd);
timestamp_time = 1420070400; /* 1-1-2015 */
tv[0].tv_sec = tv[1].tv_sec = timestamp_time;
tv[0].tv_usec = tv[1].tv_usec = 0;
if (utimes(daemon->timestamp_file, tv) == 0)
goto check_and_exit;
}
}
return -1;
}
/* Check whether today/now is between date_start and date_end */
static int is_check_date(unsigned long curtime)
{
/* Checking timestamps may be temporarily disabled */
/* If the current time if _before_ the timestamp
on our persistent timestamp file, then assume the
time if not yet correct, and don't check the
key timestamps. As soon as the current time is
later then the timestamp, update the timestamp
and start checking keys */
if (daemon->timestamp_file)
{
if (daemon->back_to_the_future == 0 && difftime(timestamp_time, curtime) <= 0)
{
if (utimes(daemon->timestamp_file, NULL) != 0)
my_syslog(LOG_ERR, _("failed to update mtime on %s: %s"), daemon->timestamp_file, strerror(errno));
my_syslog(LOG_INFO, _("system time considered valid, now checking DNSSEC signature timestamps."));
daemon->back_to_the_future = 1;
daemon->dnssec_no_time_check = 0;
queue_event(EVENT_RELOAD); /* purge cache */
}
return daemon->back_to_the_future;
}
else
return !daemon->dnssec_no_time_check;
}
/* Return bytes of canonicalised rrdata one by one.
Init state->ip with the RR, and state->end with the end of same.
Init state->op to NULL.
Init state->desc to RR descriptor.
Init state->buff with a MAXDNAME * 2 buffer.
After each call which returns 1, state->op points to the next byte of data.
On returning 0, the end has been reached.
*/
struct rdata_state {
short *desc;
size_t c;
unsigned char *end, *ip, *op;
char *buff;
};
static int get_rdata(struct dns_header *header, size_t plen, struct rdata_state *state)
{
int d;
if (state->op && state->c != 1)
{
state->op++;
state->c--;
return 1;
}
while (1)
{
d = *(state->desc);
if (d == -1)
{
/* all the bytes to the end. */
if ((state->c = state->end - state->ip) != 0)
{
state->op = state->ip;
state->ip = state->end;;
}
else
return 0;
}
else
{
state->desc++;
if (d == (u16)0)
{
/* domain-name, canonicalise */
int len;
if (!extract_name(header, plen, &state->ip, state->buff, 1, 0) ||
(len = to_wire(state->buff)) == 0)
continue;
state->c = len;
state->op = (unsigned char *)state->buff;
}
else
{
/* plain data preceding a domain-name, don't run off the end of the data */
if ((state->end - state->ip) < d)
d = state->end - state->ip;
if (d == 0)
continue;
state->op = state->ip;
state->c = d;
state->ip += d;
}
}
return 1;
}
}
/* Bubble sort the RRset into the canonical order. */
static int sort_rrset(struct dns_header *header, size_t plen, short *rr_desc, int rrsetidx,
unsigned char **rrset, char *buff1, char *buff2)
{
int swap, i, j;
do
{
for (swap = 0, i = 0; i < rrsetidx-1; i++)
{
int rdlen1, rdlen2;
struct rdata_state state1, state2;
/* Note that these have been determined to be OK previously,
so we don't need to check for NULL return here. */
state1.ip = skip_name(rrset[i], header, plen, 10);
state2.ip = skip_name(rrset[i+1], header, plen, 10);
state1.op = state2.op = NULL;
state1.buff = buff1;
state2.buff = buff2;
state1.desc = state2.desc = rr_desc;
state1.ip += 8; /* skip class, type, ttl */
GETSHORT(rdlen1, state1.ip);
if (!CHECK_LEN(header, state1.ip, plen, rdlen1))
return rrsetidx; /* short packet */
state1.end = state1.ip + rdlen1;
state2.ip += 8; /* skip class, type, ttl */
GETSHORT(rdlen2, state2.ip);
if (!CHECK_LEN(header, state2.ip, plen, rdlen2))
return rrsetidx; /* short packet */
state2.end = state2.ip + rdlen2;
/* If the RR has no names in it then canonicalisation
is the identity function and we can compare
the RRs directly. If not we compare the
canonicalised RRs one byte at a time. */
if (*rr_desc == -1)
{
int rdmin = rdlen1 > rdlen2 ? rdlen2 : rdlen1;
int cmp = memcmp(state1.ip, state2.ip, rdmin);
if (cmp > 0 || (cmp == 0 && rdlen1 > rdmin))
{
unsigned char *tmp = rrset[i+1];
rrset[i+1] = rrset[i];
rrset[i] = tmp;
swap = 1;
}
else if (cmp == 0 && (rdlen1 == rdlen2))
{
/* Two RRs are equal, remove one copy. RFC 4034, para 6.3 */
for (j = i+1; j < rrsetidx-1; j++)
rrset[j] = rrset[j+1];
rrsetidx--;
i--;
}
}
else
/* Comparing canonicalised RRs, byte-at-a-time. */
while (1)
{
int ok1, ok2;
ok1 = get_rdata(header, plen, &state1);
ok2 = get_rdata(header, plen, &state2);
if (!ok1 && !ok2)
{
/* Two RRs are equal, remove one copy. RFC 4034, para 6.3 */
for (j = i+1; j < rrsetidx-1; j++)
rrset[j] = rrset[j+1];
rrsetidx--;
i--;
break;
}
else if (ok1 && (!ok2 || *state1.op > *state2.op))
{
unsigned char *tmp = rrset[i+1];
rrset[i+1] = rrset[i];
rrset[i] = tmp;
swap = 1;
break;
}
else if (ok2 && (!ok1 || *state2.op > *state1.op))
break;
/* arrive here when bytes are equal, go round the loop again
and compare the next ones. */
}
}
} while (swap);
return rrsetidx;
}
static unsigned char **rrset = NULL, **sigs = NULL;
/* Get pointers to RRset members and signature(s) for same.
Check signatures, and return keyname associated in keyname. */
static int explore_rrset(struct dns_header *header, size_t plen, int class, int type,
char *name, char *keyname, int *sigcnt, int *rrcnt)
{
static int rrset_sz = 0, sig_sz = 0;
unsigned char *p;
int rrsetidx, sigidx, j, rdlen, res;
int gotkey = 0;
if (!(p = skip_questions(header, plen)))
return 0;
/* look for RRSIGs for this RRset and get pointers to each RR in the set. */
for (rrsetidx = 0, sigidx = 0, j = ntohs(header->ancount) + ntohs(header->nscount);
j != 0; j--)
{
unsigned char *pstart, *pdata;
int stype, sclass, type_covered;
pstart = p;
if (!(res = extract_name(header, plen, &p, name, 0, 10)))
return 0; /* bad packet */
GETSHORT(stype, p);
GETSHORT(sclass, p);
pdata = p;
p += 4; /* TTL */
GETSHORT(rdlen, p);
if (!CHECK_LEN(header, p, plen, rdlen))
return 0;
if (res == 1 && sclass == class)
{
if (stype == type)
{
if (!expand_workspace(&rrset, &rrset_sz, rrsetidx))
return 0;
rrset[rrsetidx++] = pstart;
}
if (stype == T_RRSIG)
{
if (rdlen < 18)
return 0; /* bad packet */
GETSHORT(type_covered, p);
p += 16; /* algo, labels, orig_ttl, sig_expiration, sig_inception, key_tag */
if (gotkey)
{
/* If there's more than one SIG, ensure they all have same keyname */
if (extract_name(header, plen, &p, keyname, 0, 0) != 1)
return 0;
}
else
{
gotkey = 1;
if (!extract_name(header, plen, &p, keyname, 1, 0))
return 0;
/* RFC 4035 5.3.1 says that the Signer's Name field MUST equal
the name of the zone containing the RRset. We can't tell that
for certain, but we can check that the RRset name is equal to
or encloses the signers name, which should be enough to stop
an attacker using signatures made with the key of an unrelated
zone he controls. Note that the root key is always allowed. */
if (*keyname != 0)
{
char *name_start;
for (name_start = name; !hostname_isequal(name_start, keyname); )
if ((name_start = strchr(name_start, '.')))
name_start++; /* chop a label off and try again */
else
return 0;
}
}
if (type_covered == type)
{
if (!expand_workspace(&sigs, &sig_sz, sigidx))
return 0;
sigs[sigidx++] = pdata;
}
p = pdata + 6; /* restore for ADD_RDLEN */
}
}
if (!ADD_RDLEN(header, p, plen, rdlen))
return 0;
}
*sigcnt = sigidx;
*rrcnt = rrsetidx;
return 1;
}
int dec_counter(int *counter, char *message)
{
if ((*counter)-- == 0)
{
my_syslog(LOG_WARNING, "limit exceeded: %s", message ? message : _("per-query crypto work"));
return 1;
}
return 0;
}
/* Validate a single RRset (class, type, name) in the supplied DNS reply
Return code:
STAT_SECURE if it validates.
STAT_SECURE_WILDCARD if it validates and is the result of wildcard expansion.
(In this case *wildcard_out points to the "body" of the wildcard within name.)
STAT_BOGUS signature is wrong, bad packet.
STAT_ABANDONED validation abandoned do to excess resource usage.
STAT_NEED_KEY need DNSKEY to complete validation (name is returned in keyname)
STAT_NEED_DS need DS to complete validation (name is returned in keyname)
If key is non-NULL, use that key, which has the algo and tag given in the params of those names,
otherwise find the key in the cache.
Name is unchanged on exit. keyname is used as workspace and trashed.
Call explore_rrset first to find and count RRs and sigs.
ttl_out is the floor on TTL, based on TTL and orig_ttl and expiration of sig used to validate.
*/
static int validate_rrset(time_t now, struct dns_header *header, size_t plen, int class, int type, int sigidx, int rrsetidx,
char *name, char *keyname, char **wildcard_out, struct blockdata *key, int keylen,
int algo_in, int keytag_in, unsigned long *ttl_out, int *validate_counter)
{
unsigned char *p;
int rdlen, j, name_labels, algo, labels, key_tag, sig_fail_cnt;
struct crec *crecp = NULL;
short *rr_desc = rrfilter_desc(type);
u32 sig_expiration, sig_inception;
int failflags = DNSSEC_FAIL_NOSIG | DNSSEC_FAIL_NYV | DNSSEC_FAIL_EXP | DNSSEC_FAIL_NOKEYSUP;
unsigned long curtime = time(0);
int time_check = is_check_date(curtime);
if (wildcard_out)
*wildcard_out = NULL;
name_labels = count_labels(name); /* For 4035 5.3.2 check */
/* Sort RRset records into canonical order.
Note that at this point keyname and daemon->workspacename buffs are
unused, and used as workspace by the sort. */
rrsetidx = sort_rrset(header, plen, rr_desc, rrsetidx, rrset, daemon->workspacename, keyname);
/* Now try all the sigs to try and find one which validates */
for (sig_fail_cnt = daemon->limit[LIMIT_SIG_FAIL], j = 0; j <sigidx; j++)
{
unsigned char *psav, *sig, *digest;
int i, wire_len, sig_len;
const struct nettle_hash *hash;
void *ctx;
char *name_start;
u32 nsigttl, ttl, orig_ttl;
failflags &= ~DNSSEC_FAIL_NOSIG;
p = sigs[j];
GETLONG(ttl, p);
GETSHORT(rdlen, p); /* rdlen >= 18 checked previously */
psav = p;
p += 2; /* type_covered - already checked */
algo = *p++;
labels = *p++;
GETLONG(orig_ttl, p);
GETLONG(sig_expiration, p);
GETLONG(sig_inception, p);
GETSHORT(key_tag, p);
if (!extract_name(header, plen, &p, keyname, 1, 0))
return STAT_BOGUS;
if (!time_check)
failflags &= ~(DNSSEC_FAIL_NYV | DNSSEC_FAIL_EXP);
else
{
/* We must explicitly check against wanted values, because of SERIAL_UNDEF */
if (serial_compare_32(curtime, sig_inception) == SERIAL_LT)
continue;
else
failflags &= ~DNSSEC_FAIL_NYV;
if (serial_compare_32(curtime, sig_expiration) == SERIAL_GT)
continue;
else
failflags &= ~DNSSEC_FAIL_EXP;
}
if (!(hash = hash_find(algo_digest_name(algo))))
continue;
else
failflags &= ~DNSSEC_FAIL_NOKEYSUP;
if (labels > name_labels ||
!hash_init(hash, &ctx, &digest))
continue;
/* OK, we have the signature record, see if the relevant DNSKEY is in the cache. */
if (!key && !(crecp = cache_find_by_name(NULL, keyname, now, F_DNSKEY)))
return STAT_NEED_KEY;
if (ttl_out)
{
/* 4035 5.3.3 rules on TTLs */
if (orig_ttl < ttl)
ttl = orig_ttl;
if (time_check && difftime(sig_expiration, curtime) < ttl)
ttl = difftime(sig_expiration, curtime);
*ttl_out = ttl;
}
sig = p;
sig_len = rdlen - (p - psav);
nsigttl = htonl(orig_ttl);
hash->update(ctx, 18, psav);
wire_len = to_wire(keyname);
hash->update(ctx, (unsigned int)wire_len, (unsigned char*)keyname);
from_wire(keyname);
#define RRBUFLEN 128 /* Most RRs are smaller than this. */
for (i = 0; i < rrsetidx; ++i)
{
int j;
struct rdata_state state;
u16 len;
unsigned char rrbuf[RRBUFLEN];
p = rrset[i];
if (!extract_name(header, plen, &p, name, 1, 10))
return STAT_BOGUS;
name_start = name;
/* if more labels than in RRsig name, hash *.<no labels in rrsig labels field> 4035 5.3.2 */
if (labels < name_labels)
{
for (j = name_labels - labels; j != 0; j--)
{
while (*name_start != '.' && *name_start != 0)
name_start++;
if (j != 1 && *name_start == '.')
name_start++;
}
if (wildcard_out)
*wildcard_out = name_start+1;
name_start--;
*name_start = '*';
}
wire_len = to_wire(name_start);
hash->update(ctx, (unsigned int)wire_len, (unsigned char *)name_start);
hash->update(ctx, 4, p); /* class and type */
hash->update(ctx, 4, (unsigned char *)&nsigttl);
p += 8; /* skip type, class, ttl */
GETSHORT(rdlen, p);
if (!CHECK_LEN(header, p, plen, rdlen))
return STAT_BOGUS;
/* Optimisation for RR types which need no cannonicalisation.
This includes DNSKEY DS NSEC and NSEC3, which are also long, so
it saves lots of calls to get_rdata, and avoids the pessimal
segmented insertion, even with a small rrbuf[].
If canonicalisation is not needed, a simple insertion into the hash works.
*/
if (*rr_desc == -1)
{
len = htons(rdlen);
hash->update(ctx, 2, (unsigned char *)&len);
hash->update(ctx, rdlen, p);
}
else
{
/* canonicalise rdata and calculate length of same, use
name buffer as workspace for get_rdata. */
state.ip = p;
state.op = NULL;
state.desc = rr_desc;
state.buff = name;
state.end = p + rdlen;
for (j = 0; get_rdata(header, plen, &state); j++)
if (j < RRBUFLEN)
rrbuf[j] = *state.op;
len = htons((u16)j);
hash->update(ctx, 2, (unsigned char *)&len);
/* If the RR is shorter than RRBUFLEN (most of them, in practice)
then we can just digest it now. If it exceeds RRBUFLEN we have to
go back to the start and do it in chunks. */
if (j >= RRBUFLEN)
{
state.ip = p;
state.op = NULL;
state.desc = rr_desc;
for (j = 0; get_rdata(header, plen, &state); j++)
{
rrbuf[j] = *state.op;
if (j == RRBUFLEN - 1)
{
hash->update(ctx, RRBUFLEN, rrbuf);
j = -1;
}
}
}
if (j != 0)
hash->update(ctx, j, rrbuf);
}
}
hash->digest(ctx, hash->digest_size, digest);
/* namebuff used for workspace above, restore to leave unchanged on exit */
p = (unsigned char*)(rrset[0]);
if (!extract_name(header, plen, &p, name, 1, 0))
return STAT_BOGUS;
if (key)
{
if (algo_in == algo && keytag_in == key_tag)
{
if (dec_counter(validate_counter, NULL))
return STAT_ABANDONED;
if (verify(key, keylen, sig, sig_len, digest, hash->digest_size, algo))
return STAT_SECURE;
}
}
else
{
/* iterate through all possible keys 4035 5.3.1 */
for (; crecp; crecp = cache_find_by_name(crecp, keyname, now, F_DNSKEY))
if (crecp->addr.key.algo == algo &&
crecp->addr.key.keytag == key_tag &&
crecp->uid == (unsigned int)class)
{
if (dec_counter(validate_counter, NULL))
return STAT_ABANDONED;
if (verify(crecp->addr.key.keydata, crecp->addr.key.keylen, sig, sig_len, digest, hash->digest_size, algo))
return (labels < name_labels) ? STAT_SECURE_WILDCARD : STAT_SECURE;
/* An attacker can waste a lot of our CPU by setting up a giant DNSKEY RRSET full of failing
keys, all of which we have to try. Since many failing keys is not likely for
a legitimate domain, set a limit on how many can fail. */
if ((daemon->limit[LIMIT_SIG_FAIL] - (sig_fail_cnt + 1)) > (int)daemon->metrics[METRIC_SIG_FAIL_HWM])
daemon->metrics[METRIC_SIG_FAIL_HWM] = daemon->limit[LIMIT_SIG_FAIL] - (sig_fail_cnt + 1);
if (dec_counter(&sig_fail_cnt, _("per-RRSet signature fails")))
return STAT_ABANDONED;
}
}
}
/* If we reach this point, no verifying key was found */
return STAT_BOGUS | failflags | DNSSEC_FAIL_NOKEY;
}
/* The DNS packet is expected to contain the answer to a DNSKEY query.
Put all DNSKEYs in the answer which are valid into the cache.
return codes:
STAT_OK Done, key(s) in cache.
STAT_BOGUS No DNSKEYs found, which can be validated with DS,
or self-sign for DNSKEY RRset is not valid, bad packet.
STAT_ABANDONED resource exhaustion.
STAT_NEED_DS DS records to validate a key not found, name in keyname
*/
int dnssec_validate_by_ds(time_t now, struct dns_header *header, size_t plen, char *name,
char *keyname, int class, int *validate_counter)
{
unsigned char *psave, *p = (unsigned char *)(header+1), *keyaddr;
struct crec *crecp, *recp1;
int rc, j, qtype, qclass, rdlen, flags, algo, keytag, sigcnt, rrcnt;
unsigned long ttl, sig_ttl;
union all_addr a;
int failflags = DNSSEC_FAIL_NODSSUP | DNSSEC_FAIL_NOZONE;
char valid_digest[255];
static unsigned char **cached_digest;
static size_t cached_digest_size = 0;
if (ntohs(header->qdcount) != 1 || RCODE(header) != NOERROR || !extract_name(header, plen, &p, name, 1, 4))
return STAT_BOGUS | DNSSEC_FAIL_NOKEY;
GETSHORT(qtype, p);
GETSHORT(qclass, p);
if (qtype != T_DNSKEY || qclass != class ||
!explore_rrset(header, plen, class, T_DNSKEY, name, keyname, &sigcnt, &rrcnt) ||
rrcnt == 0)
return STAT_BOGUS | DNSSEC_FAIL_NOKEY;
if (sigcnt == 0)
return STAT_BOGUS | DNSSEC_FAIL_NOSIG;
/* See if we have cached a DS record which validates this key */
if (!(crecp = cache_find_by_name(NULL, name, now, F_DS)))
{
strcpy(keyname, name);
return STAT_NEED_DS;
}
/* NOTE, we need to find ONE DNSKEY which matches the DS */
for (j = ntohs(header->ancount); j != 0; j--)
{
/* Ensure we have type, class TTL and length */
if (!(rc = extract_name(header, plen, &p, name, 0, 10)))
return STAT_BOGUS; /* bad packet */
GETSHORT(qtype, p);
GETSHORT(qclass, p);
GETLONG(ttl, p);
GETSHORT(rdlen, p);
if (!CHECK_LEN(header, p, plen, rdlen))
return STAT_BOGUS; /* bad packet */
if (qclass != class || qtype != T_DNSKEY || rc == 2)
{
p += rdlen;
continue;
}
if (rdlen < 5)
return STAT_BOGUS; /* min 1 byte key! */
psave = p;
GETSHORT(flags, p);
if (*p++ != 3)
{
p = psave + rdlen;
continue;
}
algo = *p++;
keyaddr = p;
keytag = dnskey_keytag(algo, flags, keyaddr, rdlen - 4);
p = psave + rdlen;
/* key must have zone key flag set */
if (!(flags & 0x100))
continue;
failflags &= ~DNSSEC_FAIL_NOZONE;
/* clear digest cache. */
memset(valid_digest, 0, sizeof(valid_digest));
for (recp1 = crecp; recp1; recp1 = cache_find_by_name(recp1, name, now, F_DS))
{
void *ctx;
unsigned char *digest, *ds_digest;
const struct nettle_hash *hash;
int wire_len;
if ((recp1->flags & F_NEG) ||
recp1->addr.ds.algo != algo ||
recp1->addr.ds.keytag != keytag ||
recp1->uid != (unsigned int)class)
continue;
if (!(hash = hash_find(ds_digest_name(recp1->addr.ds.digest))))
continue;
failflags &= ~DNSSEC_FAIL_NODSSUP;
if (recp1->addr.ds.keylen != (int)hash->digest_size ||
!(ds_digest = blockdata_retrieve(recp1->addr.ds.keydata, recp1->addr.ds.keylen, NULL)))
continue;
if (valid_digest[recp1->addr.ds.digest])
digest = cached_digest[recp1->addr.ds.digest];
else
{
/* computing a hash is a unit of crypto work. */
if (dec_counter(validate_counter, NULL))
return STAT_ABANDONED;
if (!hash_init(hash, &ctx, &digest))
continue;
wire_len = to_wire(name);
/* Note that digest may be different between DSs, so
we can't move this outside the loop. We keep
copies of each digest we make for this key,
so maximum digest work is O(keys x digests_types)
rather then O(keys x DSs) */
hash->update(ctx, (unsigned int)wire_len, (unsigned char *)name);
hash->update(ctx, (unsigned int)rdlen, psave);
hash->digest(ctx, hash->digest_size, digest);
from_wire(name);
if (recp1->addr.ds.digest >= cached_digest_size)
{
unsigned char **new;
/* whine_malloc zeros memory */
if ((new = whine_malloc((recp1->addr.ds.digest + 5) * sizeof(unsigned char *))))
{
if (cached_digest_size != 0)
{
memcpy(new, cached_digest, cached_digest_size * sizeof(unsigned char *));
free(cached_digest);
}
cached_digest_size = recp1->addr.ds.digest + 5;
cached_digest = new;
}
}
if (recp1->addr.ds.digest < cached_digest_size)
{
if (!cached_digest[recp1->addr.ds.digest])
cached_digest[recp1->addr.ds.digest] = whine_malloc(recp1->addr.ds.keylen);
if (cached_digest[recp1->addr.ds.digest])
{
memcpy(cached_digest[recp1->addr.ds.digest], digest, recp1->addr.ds.keylen);
valid_digest[recp1->addr.ds.digest] = 1;
}
}
}
if (memcmp(ds_digest, digest, recp1->addr.ds.keylen) == 0)
{
/* Found the key validated by a DS record.
Now check the self-sig for the entire key RRset using that key.
Note that validate_rrset() will never return STAT_NEED_KEY here,
since we supply the key it will use as an argument. */
struct blockdata *key;
if (!(key = blockdata_alloc((char *)keyaddr, rdlen - 4)))
break;
rc = validate_rrset(now, header, plen, class, T_DNSKEY, sigcnt, rrcnt, name, keyname,
NULL, key, rdlen - 4, algo, keytag, &sig_ttl, validate_counter);
blockdata_free(key);
if (STAT_ISEQUAL(rc, STAT_ABANDONED))
return rc;
/* can't validate KEY RRset with this key, see if there's another that
will, which is validated by another DS. */
if (!STAT_ISEQUAL(rc, STAT_SECURE))
break;
/* DNSKEY RRset determined to be OK, now cache it. */
cache_start_insert();
p = skip_questions(header, plen);
for (j = ntohs(header->ancount); j != 0; j--)
{
/* Ensure we have type, class TTL and length */
if (!(rc = extract_name(header, plen, &p, name, 0, 10)))
return STAT_BOGUS; /* bad packet */
GETSHORT(qtype, p);
GETSHORT(qclass, p);
GETLONG(ttl, p);
GETSHORT(rdlen, p);
/* TTL may be limited by sig. */
if (sig_ttl < ttl)
ttl = sig_ttl;
if (!CHECK_LEN(header, p, plen, rdlen))
return STAT_BOGUS; /* bad packet */
psave = p;
if (qclass == class && rc == 1 && qtype == T_DNSKEY)
{
if (rdlen < 4)
return STAT_BOGUS; /* min 1 byte key! */
GETSHORT(flags, p);
if (*p++ == 3)
{
algo = *p++;
keytag = dnskey_keytag(algo, flags, p, rdlen - 4);
if (!(key = blockdata_alloc((char*)p, rdlen - 4)))
return STAT_BOGUS;
a.key.keylen = rdlen - 4;
a.key.keydata = key;
a.key.algo = algo;
a.key.keytag = keytag;
a.key.flags = flags;
if (!cache_insert(name, &a, class, now, ttl, F_FORWARD | F_DNSKEY | F_DNSSECOK))
{
blockdata_free(key);
return STAT_BOGUS;
}
a.log.keytag = keytag;
a.log.algo = algo;
if (algo_digest_name(algo))
log_query(F_NOEXTRA | F_KEYTAG | F_UPSTREAM, name, &a, "DNSKEY keytag %hu, algo %hu", 0);
else
log_query(F_NOEXTRA | F_KEYTAG | F_UPSTREAM, name, &a, "DNSKEY keytag %hu, algo %hu (not supported)", 0);
}
}
p = psave + rdlen;
}
/* commit cache insert. */
cache_end_insert();
return STAT_OK;
}
}
}
log_query(F_NOEXTRA | F_UPSTREAM, name, NULL, "BOGUS DNSKEY", 0);
return STAT_BOGUS | failflags;
}
/* The DNS packet is expected to contain the answer to a DS query
Put all DSs in the answer which are valid and have hash and signature algos
we support into the cache.
Also handles replies which prove that there's no DS at this location,
either because the zone is unsigned or this isn't a zone cut. These are
cached too.
If none of the DS's are for supported algos, treat the answer as if
it's a proof of no DS at this location. RFC4035 para 5.2.
return codes:
STAT_OK At least one valid DS found and in cache.
STAT_BOGUS no DS in reply or not signed, fails validation, bad packet.
STAT_NEED_KEY DNSKEY records to validate a DS not found, name in keyname
STAT_NEED_DS DS record needed.
STAT_ABANDONED resource exhaustion.
*/
int dnssec_validate_ds(time_t now, struct dns_header *header, size_t plen, char *name,
char *keyname, int class, int *validate_counter)
{
unsigned char *p = (unsigned char *)(header+1);
int qtype, qclass, rc, i, neganswer = 0, nons = 0, servfail = 0, neg_ttl = 0, found_supported = 0;
int aclass, atype, rdlen, flags;
unsigned long ttl;
union all_addr a;
if (ntohs(header->qdcount) != 1 ||
!(p = skip_name(p, header, plen, 4)))
return STAT_BOGUS;
GETSHORT(qtype, p);
GETSHORT(qclass, p);
if (qtype != T_DS || qclass != class)
return STAT_BOGUS;
/* A SERVFAIL answer has been seen to a DS query not at start of authority,
so treat it as such and continue to search for a DS or proof of no existence
further down the tree. */
if (RCODE(header) == SERVFAIL)
servfail = neganswer = nons = 1;
else
{
rc = dnssec_validate_reply(now, header, plen, name, keyname, NULL, 0, &neganswer, &nons, &neg_ttl, validate_counter);
if (STAT_ISEQUAL(rc, STAT_INSECURE))
{
my_syslog(LOG_WARNING, _("Insecure DS reply received for %s, check domain configuration and upstream DNS server DNSSEC support"), name);
log_query(F_NOEXTRA | F_UPSTREAM, name, NULL, "BOGUS DS - not secure", 0);
return STAT_BOGUS | DNSSEC_FAIL_INDET;
}
p = (unsigned char *)(header+1);
if (!extract_name(header, plen, &p, name, 1, 4))
return STAT_BOGUS;
p += 4; /* qtype, qclass */
/* If the key needed to validate the DS is on the same domain as the DS, we'll
loop getting nowhere. Stop that now. This can happen of the DS answer comes
from the DS's zone, and not the parent zone. */
if (STAT_ISEQUAL(rc, STAT_NEED_KEY) && hostname_isequal(name, keyname))
{
log_query(F_NOEXTRA | F_UPSTREAM, name, NULL, "BOGUS DS", 0);
return STAT_BOGUS;
}
if (!STAT_ISEQUAL(rc, STAT_SECURE))
return rc;
}
if (!neganswer)
{
cache_start_insert();
for (i = 0; i < ntohs(header->ancount); i++)
{
unsigned char *psave;
if (!(rc = extract_name(header, plen, &p, name, 0, 10)))
return STAT_BOGUS; /* bad packet */
GETSHORT(atype, p);
GETSHORT(aclass, p);
GETLONG(ttl, p);
GETSHORT(rdlen, p);
if (!CHECK_LEN(header, p, plen, rdlen))
return STAT_BOGUS; /* bad packet */
psave = p;
if (aclass == class && atype == T_DS && rc == 1)
{
int algo, digest, keytag;
struct blockdata *key;
if (rdlen < 5)
return STAT_BOGUS; /* min 1 byte digest! */
GETSHORT(keytag, p);
algo = *p++;
digest = *p++;
if (!ds_digest_name(digest) || !algo_digest_name(algo))
{
a.log.keytag = keytag;
a.log.algo = algo;
a.log.digest = digest;
log_query(F_NOEXTRA | F_KEYTAG | F_UPSTREAM, name, &a, "DS for keytag %hu, algo %hu, digest %hu (not supported)", 0);
neg_ttl = ttl;
}
else if ((key = blockdata_alloc((char*)p, rdlen - 4)))
{
a.ds.digest = digest;
a.ds.keydata = key;
a.ds.algo = algo;
a.ds.keytag = keytag;
a.ds.keylen = rdlen - 4;
if (!cache_insert(name, &a, class, now, ttl, F_FORWARD | F_DS | F_DNSSECOK))
{
blockdata_free(key);
return STAT_BOGUS;
}
else
{
a.log.keytag = keytag;
a.log.algo = algo;
a.log.digest = digest;
log_query(F_NOEXTRA | F_KEYTAG | F_UPSTREAM, name, &a, "DS for keytag %hu, algo %hu, digest %hu", 0);
found_supported = 1;
}
}
}
p = psave + rdlen;
}
cache_end_insert();
/* Fall through if no supported algo DS found. */
if (found_supported)
return STAT_OK;
}
flags = F_FORWARD | F_DS | F_NEG | F_DNSSECOK;
if (neganswer)
{
if (RCODE(header) == NXDOMAIN)
flags |= F_NXDOMAIN;
/* We only cache validated DS records, DNSSECOK flag hijacked
to store presence/absence of NS. */
if (nons)
flags &= ~F_DNSSECOK;
}
cache_start_insert();
/* Use TTL from NSEC for negative cache entries */
if (!cache_insert(name, NULL, class, now, neg_ttl, flags))
return STAT_BOGUS;
cache_end_insert();
if (neganswer)
log_query(F_NOEXTRA | F_UPSTREAM, name, NULL,
servfail ? "SERVFAIL" : (nons ? "no DS/cut" : "no DS"), 0);
return STAT_OK;
}
/* 4034 6.1 */
static int hostname_cmp(const char *a, const char *b)
{
char *sa, *ea, *ca, *sb, *eb, *cb;
unsigned char ac, bc;
sa = ea = (char *)a + strlen(a);
sb = eb = (char *)b + strlen(b);
while (1)
{
while (sa != a && *(sa-1) != '.')
sa--;
while (sb != b && *(sb-1) != '.')
sb--;
ca = sa;
cb = sb;
while (1)
{
if (ca == ea)
{
if (cb == eb)
break;
return -1;
}
if (cb == eb)
return 1;
ac = (unsigned char) *ca++;
bc = (unsigned char) *cb++;
if (ac >= 'A' && ac <= 'Z')
ac += 'a' - 'A';
if (bc >= 'A' && bc <= 'Z')
bc += 'a' - 'A';
if (ac < bc)
return -1;
else if (ac != bc)
return 1;
}
if (sa == a)
{
if (sb == b)
return 0;
return -1;
}
if (sb == b)
return 1;
ea = --sa;
eb = --sb;
}
}
/* returns 0 on success, or DNSSEC_FAIL_* value on failure. */
static int prove_non_existence_nsec(struct dns_header *header, size_t plen, unsigned char **nsecs, unsigned char **labels, int nsec_count,
char *workspace1_in, char *workspace2, char *name, int type, int *nons)
{
int i, rc, rdlen;
unsigned char *p, *psave;
int offset = (type & 0xff) >> 3;
int mask = 0x80 >> (type & 0x07);
if (nons)
*nons = 1;
/* Find NSEC record that proves name doesn't exist */
for (i = 0; i < nsec_count; i++)
{
char *workspace1 = workspace1_in;
int sig_labels, name_labels;
p = nsecs[i];
if (!extract_name(header, plen, &p, workspace1, 1, 10))
return DNSSEC_FAIL_BADPACKET;
p += 8; /* class, type, TTL */
GETSHORT(rdlen, p);
psave = p;
if (!extract_name(header, plen, &p, workspace2, 1, 0))
return DNSSEC_FAIL_BADPACKET;
/* If NSEC comes from wildcard expansion, use original wildcard
as name for computation. */
sig_labels = *labels[i];
name_labels = count_labels(workspace1);
if (sig_labels < name_labels)
{
int k;
for (k = name_labels - sig_labels; k != 0; k--)
{
while (*workspace1 != '.' && *workspace1 != 0)
workspace1++;
if (k != 1 && *workspace1 == '.')
workspace1++;
}
workspace1--;
*workspace1 = '*';
}
rc = hostname_cmp(workspace1, name);
if (rc == 0)
{
/* 4035 para 5.4. Last sentence */
if (type == T_NSEC || type == T_RRSIG)
return 0;
/* NSEC with the same name as the RR we're testing, check
that the type in question doesn't appear in the type map */
rdlen -= p - psave;
/* rdlen is now length of type map, and p points to it
packet checked to be as long as rdlen implies in prove_non_existence() */
/* If we can prove that there's no NS record, return that information. */
if (nons && rdlen >= 2 && p[0] == 0 && (p[2] & (0x80 >> T_NS)) != 0)
*nons = 0;
if (rdlen >= 2 && p[0] == 0)
{
/* A CNAME answer would also be valid, so if there's a CNAME is should
have been returned. */
if ((p[2] & (0x80 >> T_CNAME)) != 0)
return DNSSEC_FAIL_NONSEC;
/* If the SOA bit is set for a DS record, then we have the
DS from the wrong side of the delegation. For the root DS,
this is expected. */
if (name_labels != 0 && type == T_DS && (p[2] & (0x80 >> T_SOA)) != 0)
return DNSSEC_FAIL_NONSEC;
}
while (rdlen >= 2)
{
if (!CHECK_LEN(header, p, plen, rdlen))
return DNSSEC_FAIL_BADPACKET;
if (p[0] == type >> 8)
{
/* Does the NSEC say our type exists? */
if (offset < p[1] && (p[offset+2] & mask) != 0)
return DNSSEC_FAIL_NONSEC;
break; /* finished checking */
}
rdlen -= p[1];
p += p[1];
}
return 0;
}
else if (rc == -1)
{
/* Normal case, name falls between NSEC name and next domain name,
wrap around case, name falls between NSEC name (rc == -1) and end */
if (hostname_cmp(workspace2, name) >= 0 || hostname_cmp(workspace1, workspace2) >= 0)
return 0;
}
else
{
/* wrap around case, name falls between start and next domain name */
if (hostname_cmp(workspace1, workspace2) >= 0 && hostname_cmp(workspace2, name) >=0 )
return 0;
}
}
return DNSSEC_FAIL_NONSEC;
}
/* return digest length, or zero on error */
static int hash_name(char *in, unsigned char **out, struct nettle_hash const *hash,
unsigned char *salt, int salt_len, int iterations)
{
void *ctx;
unsigned char *digest;
int i;
if (!hash_init(hash, &ctx, &digest))
return 0;
hash->update(ctx, to_wire(in), (unsigned char *)in);
hash->update(ctx, salt_len, salt);
hash->digest(ctx, hash->digest_size, digest);
for(i = 0; i < iterations; i++)
{
hash->update(ctx, hash->digest_size, digest);
hash->update(ctx, salt_len, salt);
hash->digest(ctx, hash->digest_size, digest);
}
from_wire(in);
*out = digest;
return hash->digest_size;
}
/* Decode base32 to first "." or end of string */
static int base32_decode(char *in, unsigned char *out)
{
int oc, on, c, mask, i;
unsigned char *p = out;
for (c = *in, oc = 0, on = 0; c != 0 && c != '.'; c = *++in)
{
if (c >= '0' && c <= '9')
c -= '0';
else if (c >= 'a' && c <= 'v')
c -= 'a', c += 10;
else if (c >= 'A' && c <= 'V')
c -= 'A', c += 10;
else
return 0;
for (mask = 0x10, i = 0; i < 5; i++)
{
if (c & mask)
oc |= 1;
mask = mask >> 1;
if (((++on) & 7) == 0)
*p++ = oc;
oc = oc << 1;
}
}
if ((on & 7) != 0)
return 0;
return p - out;
}
static int check_nsec3_coverage(struct dns_header *header, size_t plen, int digest_len, unsigned char *digest, int type,
char *workspace1, char *workspace2, unsigned char **nsecs, int nsec_count, int *nons, int name_labels)
{
int i, hash_len, salt_len, base32_len, rdlen, flags;
unsigned char *p, *psave;
for (i = 0; i < nsec_count; i++)
if ((p = nsecs[i]))
{
if (!extract_name(header, plen, &p, workspace1, 1, 10) ||
!(base32_len = base32_decode(workspace1, (unsigned char *)workspace2)))
return 0;
p += 8; /* class, type, TTL */
GETSHORT(rdlen, p);
psave = p;
/* packet checked to be as long as implied by rdlen, salt_len and hash_len in prove_non_existence() */
p++; /* algo */
flags = *p++; /* flags */
p += 2; /* iterations */
salt_len = *p++; /* salt_len */
p += salt_len; /* salt */
hash_len = *p++; /* p now points to next hashed name */
if (digest_len == base32_len && hash_len == base32_len)
{
int rc = memcmp(workspace2, digest, digest_len);
if (rc == 0)
{
/* We found an NSEC3 whose hashed name exactly matches the query, so
we just need to check the type map. p points to the RR data for the record.
Note we have packet length up to rdlen bytes checked. */
int offset = (type & 0xff) >> 3;
int mask = 0x80 >> (type & 0x07);
p += hash_len; /* skip next-domain hash */
rdlen -= p - psave;
if (rdlen >= 2 && p[0] == 0)
{
/* If we can prove that there's no NS record, return that information. */
if (nons && (p[2] & (0x80 >> T_NS)) != 0)
*nons = 0;
/* A CNAME answer would also be valid, so if there's a CNAME is should
have been returned. */
if ((p[2] & (0x80 >> T_CNAME)) != 0)
return 0;
/* If the SOA bit is set for a DS record, then we have the
DS from the wrong side of the delegation. For the root DS,
this is expected. */
if (name_labels != 0 && type == T_DS && (p[2] & (0x80 >> T_SOA)) != 0)
return 0;
}
while (rdlen >= 2)
{
if (p[0] == type >> 8)
{
/* Does the NSEC3 say our type exists? */
if (offset < p[1] && (p[offset+2] & mask) != 0)
return 0;
break; /* finished checking */
}
rdlen -= p[1];
p += p[1];
}
return 1;
}
else if (rc < 0)
{
/* Normal case, hash falls between NSEC3 name-hash and next domain name-hash,
wrap around case, name-hash falls between NSEC3 name-hash and end */
if (memcmp(p, digest, digest_len) >= 0 || memcmp(workspace2, p, digest_len) >= 0)
{
if ((flags & 0x01) && nons) /* opt out */
*nons = 0;
return 1;
}
}
else
{
/* wrap around case, name falls between start and next domain name */
if (memcmp(workspace2, p, digest_len) >= 0 && memcmp(p, digest, digest_len) >= 0)
{
if ((flags & 0x01) && nons) /* opt out */
*nons = 0;
return 1;
}
}
}
}
return 0;
}
/* returns 0 on success, or DNSSEC_FAIL_* value on failure. */
static int prove_non_existence_nsec3(struct dns_header *header, size_t plen, unsigned char **nsecs, int nsec_count, char *workspace1,
char *workspace2, char *name, int type, char *wildname, int *nons, int *validate_counter)
{
unsigned char *salt, *p, *digest;
int digest_len, i, iterations, salt_len, base32_len, algo = 0;
struct nettle_hash const *hash;
char *closest_encloser, *next_closest, *wildcard;
if (nons)
*nons = 1;
/* Look though the NSEC3 records to find the first one with
an algorithm we support.
Take the algo, iterations, and salt of that record
as the ones we're going to use, and prune any
that don't match. */
for (i = 0; i < nsec_count; i++)
{
if (!(p = skip_name(nsecs[i], header, plen, 15)))
return DNSSEC_FAIL_BADPACKET; /* bad packet */
p += 10; /* type, class, TTL, rdlen */
algo = *p++;
if ((hash = hash_find(nsec3_digest_name(algo))))
break; /* known algo */
}
/* No usable NSEC3s */
if (i == nsec_count)
return DNSSEC_FAIL_NONSEC;
p++; /* flags */
GETSHORT (iterations, p);
/* Upper-bound iterations, to avoid DoS. RFC 9276 refers. */
if (iterations > daemon->limit[LIMIT_NSEC3_ITERS])
return DNSSEC_FAIL_NSEC3_ITERS;
salt_len = *p++;
salt = p;
/* Now prune so we only have NSEC3 records with same iterations, salt and algo */
for (i = 0; i < nsec_count; i++)
{
unsigned char *nsec3p = nsecs[i];
int this_iter, flags;
nsecs[i] = NULL; /* Speculative, will be restored if OK. */
if (!(p = skip_name(nsec3p, header, plen, 15)))
return 0; /* bad packet */
p += 10; /* type, class, TTL, rdlen */
if (*p++ != algo)
continue;
flags = *p++; /* flags */
/* 5155 8.2 */
if (flags != 0 && flags != 1)
continue;
GETSHORT(this_iter, p);
if (this_iter != iterations)
continue;
if (salt_len != *p++)
continue;
if (memcmp(p, salt, salt_len) != 0)
continue;
/* All match, put the pointer back */
nsecs[i] = nsec3p;
}
if (dec_counter(validate_counter, NULL))
return DNSSEC_FAIL_WORK;
if ((digest_len = hash_name(name, &digest, hash, salt, salt_len, iterations)) == 0)
return DNSSEC_FAIL_NONSEC;
if (check_nsec3_coverage(header, plen, digest_len, digest, type, workspace1, workspace2, nsecs, nsec_count, nons, count_labels(name)))
return 0;
/* Can't find an NSEC3 which covers the name directly, we need the "closest encloser NSEC3"
or an answer inferred from a wildcard record. */
closest_encloser = name;
next_closest = NULL;
do
{
if (*closest_encloser == '.')
closest_encloser++;
if (wildname && hostname_isequal(closest_encloser, wildname))
break;
if (dec_counter(validate_counter, NULL))
return DNSSEC_FAIL_WORK;
if ((digest_len = hash_name(closest_encloser, &digest, hash, salt, salt_len, iterations)) == 0)
return DNSSEC_FAIL_NONSEC;
for (i = 0; i < nsec_count; i++)
if ((p = nsecs[i]))
{
if (!extract_name(header, plen, &p, workspace1, 1, 0))
return DNSSEC_FAIL_BADPACKET;
if (!(base32_len = base32_decode(workspace1, (unsigned char *)workspace2)))
return DNSSEC_FAIL_NONSEC;
if (digest_len == base32_len &&
memcmp(digest, workspace2, digest_len) == 0)
break; /* Gotit */
}
if (i != nsec_count)
break;
next_closest = closest_encloser;
}
while ((closest_encloser = strchr(closest_encloser, '.')));
if (!closest_encloser || !next_closest)
return DNSSEC_FAIL_NONSEC;
/* Look for NSEC3 that proves the non-existence of the next-closest encloser */
if (dec_counter(validate_counter, NULL))
return DNSSEC_FAIL_WORK;
if ((digest_len = hash_name(next_closest, &digest, hash, salt, salt_len, iterations)) == 0)
return DNSSEC_FAIL_NONSEC;
if (!check_nsec3_coverage(header, plen, digest_len, digest, type, workspace1, workspace2, nsecs, nsec_count, NULL, 1))
return DNSSEC_FAIL_NONSEC;
/* Finally, check that there's no seat of wildcard synthesis */
if (!wildname)
{
if (!(wildcard = strchr(next_closest, '.')) || wildcard == next_closest)
return 0;
wildcard--;
*wildcard = '*';
if (dec_counter(validate_counter, NULL))
return DNSSEC_FAIL_WORK;
if ((digest_len = hash_name(wildcard, &digest, hash, salt, salt_len, iterations)) == 0)
return DNSSEC_FAIL_NONSEC;
if (!check_nsec3_coverage(header, plen, digest_len, digest, type, workspace1, workspace2, nsecs, nsec_count, NULL, 1))
return DNSSEC_FAIL_NONSEC;
}
return 0;
}
/* returns 0 on success, or DNSSEC_FAIL_* value on failure. */
static int prove_non_existence(struct dns_header *header, size_t plen, char *keyname, char *name, int qtype, int qclass,
char *wildname, int *nons, int *nsec_ttl, int *validate_counter)
{
static unsigned char **nsecset = NULL, **rrsig_labels = NULL;
static int nsecset_sz = 0, rrsig_labels_sz = 0;
int type_found = 0;
unsigned char *auth_start, *p = skip_questions(header, plen);
int type, class, rdlen, i, nsecs_found;
unsigned long ttl;
/* Move to NS section */
if (!p || !(p = skip_section(p, ntohs(header->ancount), header, plen)))
return DNSSEC_FAIL_BADPACKET;
auth_start = p;
for (nsecs_found = 0, i = 0; i < ntohs(header->nscount); i++)
{
unsigned char *pstart = p;
if (!extract_name(header, plen, &p, daemon->workspacename, 1, 10))
return DNSSEC_FAIL_BADPACKET;
GETSHORT(type, p);
GETSHORT(class, p);
GETLONG(ttl, p);
GETSHORT(rdlen, p);
if (!CHECK_LEN(header, p, plen, rdlen))
return DNSSEC_FAIL_BADPACKET;
if (class == qclass && (type == T_NSEC || type == T_NSEC3))
{
if (nsec_ttl)
{
/* Limit TTL with sig TTL */
if (daemon->rr_status[ntohs(header->ancount) + i] < ttl)
ttl = daemon->rr_status[ntohs(header->ancount) + i];
*nsec_ttl = ttl;
}
/* No mixed NSECing 'round here, thankyouverymuch */
if (type_found != 0 && type_found != type)
return DNSSEC_FAIL_NONSEC;
type_found = type;
if (!expand_workspace(&nsecset, &nsecset_sz, nsecs_found))
return DNSSEC_FAIL_BADPACKET;
if (type == T_NSEC)
{
/* If we're looking for NSECs, find the corresponding SIGs, to
extract the labels value, which we need in case the NSECs
are the result of wildcard expansion.
Note that the NSEC may not have been validated yet
so if there are multiple SIGs, make sure the label value
is the same in all, to avoid be duped by a rogue one.
If there are no SIGs, that's an error */
unsigned char *p1 = auth_start;
int res, j, rdlen1, type1, class1;
if (!expand_workspace(&rrsig_labels, &rrsig_labels_sz, nsecs_found))
return DNSSEC_FAIL_BADPACKET;
rrsig_labels[nsecs_found] = NULL;
for (j = ntohs(header->nscount); j != 0; j--)
{
unsigned char *psav;
if (!(res = extract_name(header, plen, &p1, daemon->workspacename, 0, 10)))
return DNSSEC_FAIL_BADPACKET;
GETSHORT(type1, p1);
GETSHORT(class1, p1);
p1 += 4; /* TTL */
GETSHORT(rdlen1, p1);
psav = p1;
if (!CHECK_LEN(header, p1, plen, rdlen1))
return DNSSEC_FAIL_BADPACKET;
if (res == 1 && class1 == qclass && type1 == T_RRSIG)
{
int type_covered;
if (rdlen1 < 18)
return DNSSEC_FAIL_BADPACKET; /* bad packet */
GETSHORT(type_covered, p1);
if (type_covered == T_NSEC)
{
p1++; /* algo */
/* labels field must be the same in every SIG we find. */
if (!rrsig_labels[nsecs_found])
rrsig_labels[nsecs_found] = p1;
else if (*rrsig_labels[nsecs_found] != *p1) /* algo */
return DNSSEC_FAIL_NONSEC;
}
}
p1 = psav + rdlen1;
}
/* Must have found at least one sig. */
if (!rrsig_labels[nsecs_found])
return DNSSEC_FAIL_NONSEC;
}
else if (type == T_NSEC3)
{
/* Decode the packet structure enough to check that rdlen is big enough
to contain everything other than the type bitmap.
(packet checked to be long enough to contain rdlen above)
We don't need to do any further length checks in check_nes3_coverage()
or prove_non_existence_nsec3() */
int salt_len, hash_len;
unsigned char *psav = p;
if (rdlen < 5)
return DNSSEC_FAIL_BADPACKET;
p += 4; /* algo, flags, iterations */
salt_len = *p++; /* salt_len */
if (rdlen < (6 + salt_len))
return DNSSEC_FAIL_BADPACKET; /* check up to hash_length */
p += salt_len; /* salt */
hash_len = *p++;
if (rdlen < (6 + salt_len + hash_len))
return DNSSEC_FAIL_BADPACKET; /* check to end of next hashed name */
p = psav;
}
nsecset[nsecs_found++] = pstart;
}
p += rdlen;
}
if (type_found == T_NSEC)
return prove_non_existence_nsec(header, plen, nsecset, rrsig_labels, nsecs_found, daemon->workspacename, keyname, name, qtype, nons);
else if (type_found == T_NSEC3)
return prove_non_existence_nsec3(header, plen, nsecset, nsecs_found, daemon->workspacename, keyname, name, qtype, wildname, nons, validate_counter);
else
return DNSSEC_FAIL_NONSEC;
}
/* Check signing status of name.
returns:
STAT_SECURE zone is signed.
STAT_INSECURE zone proved unsigned.
STAT_NEED_DS require DS record of name returned in keyname.
STAT_NEED_KEY require DNSKEY record of name returned in keyname.
name returned unaltered.
*/
static int zone_status(char *name, int class, char *keyname, time_t now)
{
int name_start = strlen(name); /* for when TA is root */
struct crec *crecp;
char *p;
/* First, work towards the root, looking for a trust anchor.
This can either be one configured, or one previously cached.
We can assume, if we don't find one first, that there is
a trust anchor at the root. */
for (p = name; p; p = strchr(p, '.'))
{
if (*p == '.')
p++;
if (cache_find_by_name(NULL, p, now, F_DS))
{
name_start = p - name;
break;
}
}
/* Now work away from the trust anchor */
while (1)
{
strcpy(keyname, &name[name_start]);
if (!(crecp = cache_find_by_name(NULL, keyname, now, F_DS)))
return STAT_NEED_DS;
/* F_DNSSECOK misused in DS cache records to non-existence of NS record.
F_NEG && !F_DNSSECOK implies that we've proved there's no DS record here,
but that's because there's no NS record either, ie this isn't the start
of a zone. We only prove that the DNS tree below a node is unsigned when
we prove that we're at a zone cut AND there's no DS record. */
if (crecp->flags & F_NEG)
{
if (crecp->flags & F_DNSSECOK)
return STAT_INSECURE; /* proved no DS here */
}
else
{
/* If all the DS records have digest and/or sig algos we don't support,
then the zone is insecure. Note that if an algo
appears in the DS, then RRSIGs for that algo MUST
exist for each RRset: 4035 para 2.2 So if we find
a DS here with digest and sig we can do, we're entitled
to assume we can validate the zone and if we can't later,
because an RRSIG is missing we return BOGUS.
*/
do
{
if (crecp->uid == (unsigned int)class &&
ds_digest_name(crecp->addr.ds.digest) &&
algo_digest_name(crecp->addr.ds.algo))
break;
}
while ((crecp = cache_find_by_name(crecp, keyname, now, F_DS)));
if (!crecp)
return STAT_INSECURE;
}
if (name_start == 0)
break;
for (p = &name[name_start-2]; (*p != '.') && (p != name); p--);
if (p != name)
p++;
name_start = p - name;
}
return STAT_SECURE;
}
/* Validate all the RRsets in the answer and authority sections of the reply (4035:3.2.3)
Return code:
STAT_SECURE if it validates.
STAT_INSECURE at least one RRset not validated, because in unsigned zone.
STAT_BOGUS signature is wrong, bad packet, no validation where there should be.
STAT_NEED_KEY need DNSKEY to complete validation (name is returned in keyname, class in *class)
STAT_NEED_DS need DS to complete validation (name is returned in keyname)
STAT_ABANDONED resource exhaustion.
daemon->rr_status points to a char array which corressponds to the RRs in the
answer and auth sections. This is set to >1 for each RR which is validated, and 0 for any which aren't.
When validating replies to DS records, we're only interested in the NSEC{3} RRs in the auth section.
Other RRs in that section missing sigs will not cause am INSECURE reply. We determine this mode
if the nons argument is non-NULL.
*/
int dnssec_validate_reply(time_t now, struct dns_header *header, size_t plen, char *name, char *keyname,
int *class, int check_unsigned, int *neganswer, int *nons, int *nsec_ttl, int *validate_counter)
{
static unsigned char **targets = NULL;
static int target_sz = 0;
unsigned char *ans_start, *p1, *p2;
int type1, class1, rdlen1 = 0, type2, class2, rdlen2, qclass, qtype, targetidx;
int i, j, rc = STAT_INSECURE;
int secure = STAT_SECURE;
int rc_nsec;
/* extend rr_status if necessary */
if (daemon->rr_status_sz < ntohs(header->ancount) + ntohs(header->nscount))
{
unsigned long *new = whine_malloc(sizeof(*daemon->rr_status) * (ntohs(header->ancount) + ntohs(header->nscount) + 64));
if (!new)
return STAT_BOGUS;
free(daemon->rr_status);
daemon->rr_status = new;
daemon->rr_status_sz = ntohs(header->ancount) + ntohs(header->nscount) + 64;
}
memset(daemon->rr_status, 0, sizeof(*daemon->rr_status) * daemon->rr_status_sz);
if (neganswer)
*neganswer = 0;
if (RCODE(header) == SERVFAIL || ntohs(header->qdcount) != 1)
return STAT_BOGUS;
if (RCODE(header) != NXDOMAIN && RCODE(header) != NOERROR)
return STAT_INSECURE;
p1 = (unsigned char *)(header+1);
/* Find all the targets we're looking for answers to.
The zeroth array element is for the query, subsequent ones
for CNAME targets, unless the query is for a CNAME or ANY. */
if (!expand_workspace(&targets, &target_sz, 0))
return STAT_BOGUS;
targets[0] = p1;
targetidx = 1;
if (!extract_name(header, plen, &p1, name, 1, 4))
return STAT_BOGUS;
GETSHORT(qtype, p1);
GETSHORT(qclass, p1);
ans_start = p1;
/* Can't validate an RRSIG query */
if (qtype == T_RRSIG)
return STAT_INSECURE;
if (qtype != T_CNAME && qtype != T_ANY)
for (j = ntohs(header->ancount); j != 0; j--)
{
if (!(p1 = skip_name(p1, header, plen, 10)))
return STAT_BOGUS; /* bad packet */
GETSHORT(type2, p1);
p1 += 6; /* class, TTL */
GETSHORT(rdlen2, p1);
if (type2 == T_CNAME)
{
if (!expand_workspace(&targets, &target_sz, targetidx))
return STAT_BOGUS;
targets[targetidx++] = p1; /* pointer to target name */
}
if (!ADD_RDLEN(header, p1, plen, rdlen2))
return STAT_BOGUS;
}
for (p1 = ans_start, i = 0; i < ntohs(header->ancount) + ntohs(header->nscount); i++)
{
if (i != 0 && !ADD_RDLEN(header, p1, plen, rdlen1))
return STAT_BOGUS;
if (!extract_name(header, plen, &p1, name, 1, 10))
return STAT_BOGUS; /* bad packet */
GETSHORT(type1, p1);
GETSHORT(class1, p1);
p1 += 4; /* TTL */
GETSHORT(rdlen1, p1);
/* Don't try and validate RRSIGs! */
if (type1 == T_RRSIG)
continue;
/* Check if we've done this RRset already */
for (p2 = ans_start, j = 0; j < i; j++)
{
if (!(rc = extract_name(header, plen, &p2, name, 0, 10)))
return STAT_BOGUS; /* bad packet */
GETSHORT(type2, p2);
GETSHORT(class2, p2);
p2 += 4; /* TTL */
GETSHORT(rdlen2, p2);
if (type2 == type1 && class2 == class1 && rc == 1)
break; /* Done it before: name, type, class all match. */
if (!ADD_RDLEN(header, p2, plen, rdlen2))
return STAT_BOGUS;
}
/* Done already: copy the validation status */
if (j != i)
daemon->rr_status[i] = daemon->rr_status[j];
else
{
/* Not done, validate now */
int sigcnt, rrcnt;
char *wildname;
if (!explore_rrset(header, plen, class1, type1, name, keyname, &sigcnt, &rrcnt))
return STAT_BOGUS;
/* No signatures for RRset. We can be configured to assume this is OK and return an INSECURE result. */
if (sigcnt == 0)
{
/* NSEC and NSEC3 records must be signed. We make this assumption elsewhere. */
if (type1 == T_NSEC || type1 == T_NSEC3)
return STAT_BOGUS | DNSSEC_FAIL_NOSIG;
else if (nons && i >= ntohs(header->ancount))
/* If we're validating a DS reply, rather than looking for the value of AD bit,
we only care that NSEC and NSEC3 RRs in the auth section are signed.
Return SECURE even if others (SOA....) are not. */
rc = STAT_SECURE;
else
{
/* unsigned RRsets in auth section are not BOGUS, but do make reply insecure. */
if (check_unsigned && i < ntohs(header->ancount))
{
rc = zone_status(name, class1, keyname, now);
if (STAT_ISEQUAL(rc, STAT_SECURE))
rc = STAT_BOGUS | DNSSEC_FAIL_NOSIG;
if (class)
*class = class1; /* Class for NEED_DS or NEED_KEY */
}
else
rc = STAT_INSECURE;
if (!STAT_ISEQUAL(rc, STAT_INSECURE))
return rc;
}
}
else
{
/* explore_rrset() gives us key name from sigs in keyname.
Can't overwrite name here. */
strcpy(daemon->workspacename, keyname);
rc = zone_status(daemon->workspacename, class1, keyname, now);
if (STAT_ISEQUAL(rc, STAT_BOGUS) || STAT_ISEQUAL(rc, STAT_NEED_KEY) || STAT_ISEQUAL(rc, STAT_NEED_DS))
{
if (class)
*class = class1; /* Class for NEED_DS or NEED_KEY */
return rc;
}
/* Zone is insecure, don't need to validate RRset */
if (STAT_ISEQUAL(rc, STAT_SECURE))
{
unsigned long sig_ttl;
rc = validate_rrset(now, header, plen, class1, type1, sigcnt,
rrcnt, name, keyname, &wildname, NULL, 0, 0, 0, &sig_ttl, validate_counter);
if (STAT_ISEQUAL(rc, STAT_BOGUS) || STAT_ISEQUAL(rc, STAT_NEED_KEY) || STAT_ISEQUAL(rc, STAT_NEED_DS) || STAT_ISEQUAL(rc, STAT_ABANDONED))
{
if (class)
*class = class1; /* Class for DS or DNSKEY */
return rc;
}
/* rc is now STAT_SECURE or STAT_SECURE_WILDCARD */
/* Note that RR is validated */
daemon->rr_status[i] = sig_ttl;
/* Note if we've validated either the answer to the question
or the target of a CNAME. Any not noted will need NSEC or
to be in unsigned space. */
for (j = 0; j <targetidx; j++)
if ((p2 = targets[j]))
{
int rc1;
if (!(rc1 = extract_name(header, plen, &p2, name, 0, 10)))
return STAT_BOGUS; /* bad packet */
if (class1 == qclass && rc1 == 1 && (type1 == T_CNAME || type1 == qtype || qtype == T_ANY ))
targets[j] = NULL;
}
/* An attacker replay a wildcard answer with a different
answer and overlay a genuine RR. To prove this
hasn't happened, the answer must prove that
the genuine record doesn't exist. Check that here.
Note that we may not yet have validated the NSEC/NSEC3 RRsets.
That's not a problem since if the RRsets later fail
we'll return BOGUS then. */
if (STAT_ISEQUAL(rc, STAT_SECURE_WILDCARD) &&
((rc_nsec = prove_non_existence(header, plen, keyname, name, type1, class1, wildname, NULL, NULL, validate_counter))) != 0)
return (rc_nsec & DNSSEC_FAIL_WORK) ? STAT_ABANDONED : (STAT_BOGUS | rc_nsec);
rc = STAT_SECURE;
}
}
}
if (STAT_ISEQUAL(rc, STAT_INSECURE))
secure = STAT_INSECURE;
}
/* OK, all the RRsets validate, now see if we have a missing answer or CNAME target. */
for (j = 0; j <targetidx; j++)
if ((p2 = targets[j]))
{
if (neganswer)
*neganswer = 1;
if (!extract_name(header, plen, &p2, name, 1, 10))
return STAT_BOGUS; /* bad packet */
/* NXDOMAIN or NODATA reply, unanswered question is (name, qclass, qtype) */
/* For anything other than a DS record, this situation is OK if either
the answer is in an unsigned zone, or there's a NSEC records. */
if ((rc_nsec = prove_non_existence(header, plen, keyname, name, qtype, qclass, NULL, nons, nsec_ttl, validate_counter)) != 0)
{
if (rc_nsec & DNSSEC_FAIL_WORK)
return STAT_ABANDONED;
/* Empty DS without NSECS */
if (qtype == T_DS)
return STAT_BOGUS | rc_nsec;
if ((rc_nsec & (DNSSEC_FAIL_NONSEC | DNSSEC_FAIL_NSEC3_ITERS)) &&
!STAT_ISEQUAL((rc = zone_status(name, qclass, keyname, now)), STAT_SECURE))
{
if (class)
*class = qclass; /* Class for NEED_DS or NEED_KEY */
return rc;
}
return STAT_BOGUS | rc_nsec; /* signed zone, no NSECs */
}
}
return secure;
}
/* Compute keytag (checksum to quickly index a key). See RFC4034 */
int dnskey_keytag(int alg, int flags, unsigned char *key, int keylen)
{
if (alg == 1)
{
/* Algorithm 1 (RSAMD5) has a different (older) keytag calculation algorithm.
See RFC4034, Appendix B.1 */
return key[keylen-4] * 256 + key[keylen-3];
}
else
{
unsigned long ac = flags + 0x300 + alg;
int i;
for (i = 0; i < keylen; ++i)
ac += (i & 1) ? key[i] : key[i] << 8;
ac += (ac >> 16) & 0xffff;
return ac & 0xffff;
}
}
size_t dnssec_generate_query(struct dns_header *header, unsigned char *end, char *name, int class,
int type, int edns_pktsz)
{
unsigned char *p;
size_t ret;
header->qdcount = htons(1);
header->ancount = htons(0);
header->nscount = htons(0);
header->arcount = htons(0);
header->hb3 = HB3_RD;
SET_OPCODE(header, QUERY);
/* For debugging, set Checking Disabled, otherwise, have the upstream check too,
this allows it to select auth servers when one is returning bad data. */
header->hb4 = option_bool(OPT_DNSSEC_DEBUG) ? HB4_CD : 0;
/* ID filled in later */
p = (unsigned char *)(header+1);
p = do_rfc1035_name(p, name, NULL);
*p++ = 0;
PUTSHORT(type, p);
PUTSHORT(class, p);
ret = add_do_bit(header, p - (unsigned char *)header, end);
if (find_pseudoheader(header, ret, NULL, &p, NULL, NULL))
PUTSHORT(edns_pktsz, p);
return ret;
}
int errflags_to_ede(int status)
{
/* We can end up with more than one flag set for some errors,
so this encodes a rough priority so the (eg) No sig is reported
before no-unexpired-sig. */
if (status & DNSSEC_FAIL_NYV)
return EDE_SIG_NYV;
else if (status & DNSSEC_FAIL_EXP)
return EDE_SIG_EXP;
else if (status & DNSSEC_FAIL_NOKEYSUP)
return EDE_USUPDNSKEY;
else if (status & DNSSEC_FAIL_NOZONE)
return EDE_NO_ZONEKEY;
else if (status & DNSSEC_FAIL_NOKEY)
return EDE_NO_DNSKEY;
else if (status & DNSSEC_FAIL_NODSSUP)
return EDE_USUPDS;
else if (status & DNSSEC_FAIL_NSEC3_ITERS)
return EDE_UNS_NS3_ITER;
else if (status & DNSSEC_FAIL_NONSEC)
return EDE_NO_NSEC;
else if (status & DNSSEC_FAIL_INDET)
return EDE_DNSSEC_IND;
else if (status & DNSSEC_FAIL_NOSIG)
return EDE_NO_RRSIG;
else
return EDE_UNSET;
}
#endif /* HAVE_DNSSEC */
Reference in New Issue View Git Blame Copy Permalink