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INSECURE when NSEC3 iteration count too high 

Fix from Wouter's review
This commit is contained in:
Willem Toorop 2015-07-07 22:33:53 +02:00
parent 4b53d70199
commit e48b0c7fd7
1 changed files with 102 additions and 38 deletions
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122
src/dnssec.c
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@ -210,6 +210,9 @@
/* Maximum number of canonical name redirections for one name */
#define MAX_CNAMES 100
#define SIGNATURE_VERIFIED 0x10000
#define NSEC3_ITERATION_COUNT_HIGH 0x20000
/******************* Frequently Used Utility Functions *********************
*****************************************************************************/
@ -497,7 +500,7 @@ typedef struct getdns_rrset {
uint16_t rr_type;
uint8_t *pkt;
size_t pkt_len;
uint8_t name_spc[];
uint8_t name_spc[1];
} getdns_rrset;
typedef struct rrtype_iter {
@ -1460,6 +1463,41 @@ static uint8_t *name2nsec3_label(
return NULL;
}
static int nsec3_iteration_count_high(rrtype_iter *dnskey, getdns_rrset *nsec3)
{
rrtype_iter rr_spc, *rr;
size_t bits;
/* No NSEC3, then iteration count is not too high */
if (nsec3->rr_type != GETDNS_RRTYPE_NSEC3)
return 0;
/* Enough space to at least read algorithm field?
* Without key data iteration count is definitely too high.
*/
if (dnskey->rr_i.nxt < dnskey->rr_i.rr_type + 14)
return 1;
if (/* Initialize rr for getting NSEC3 rdata fields */
!(rr = rrtype_iter_init(&rr_spc, nsec3))
/* Check for available space to get rdata fields */
|| rr->rr_i.rr_type + 14 > rr->rr_i.nxt)
return 1;
bits = ldns_rr_dnskey_key_size_raw(dnskey->rr_i.rr_type + 10,
dnskey->rr_i.nxt - dnskey->rr_i.rr_type - 10,
dnskey->rr_i.rr_type[13]);
if (bits > 2048)
return gldns_read_uint16(rr->rr_i.rr_type + 12) > 2500;
else if (bits > 1024)
return gldns_read_uint16(rr->rr_i.rr_type + 12) > 500;
else
return gldns_read_uint16(rr->rr_i.rr_type + 12) > 150;
}
/* Returns whether dnskey signed rrset. If the rrset was a valid wildcard
* expansion, nc_name will point to the next closer part of the name in rrset.
*/
@ -1512,7 +1550,14 @@ static int dnskey_signed_rrset(
debug_sec_print_rr("key ", &dnskey->rr_i);
debug_sec_print_rrset("signed ", rrset);
return 0x10000 | keytag; /* in case keytag == 0 */
/* Signal insecurity by too high nsec3 iteration
* count with NSEC3_ITERATION_COUNT_HIGH
* bit in return value.
*/
return ( nsec3_iteration_count_high(dnskey, rrset)
? NSEC3_ITERATION_COUNT_HIGH
: SIGNATURE_VERIFIED
) | keytag;
}
}
return 0;
@ -1618,7 +1663,7 @@ static int ds_authenticates_keys(getdns_rrset *ds_set, getdns_rrset *dnskey_set)
debug_sec_print_rrset(
"keyset authenticated: ", dnskey_set);
return 0x10000 | keytag; /* In case keytag == 0 */
return SIGNATURE_VERIFIED | keytag;
}
debug_sec_print_rrset(
"keyset failed authentication: ", dnskey_set);
@ -1768,28 +1813,35 @@ static int find_nsec_covering_name(
; i ; i = rrset_iter_next(i)) {
if ((n = rrset_iter_value(i))->rr_type == GETDNS_RRTYPE_NSEC3
&& nsec3_covers_name(n, name, opt_out)
/* Get the bitmap rdata field */
&& (nsec_rr = rrtype_iter_init(&nsec_spc, n))
&& (bitmap = priv_getdns_rdf_iter_init_at(
&bitmap_spc, &nsec_rr->rr_i, 5))
&& (keytag = a_key_signed_rrset(dnskey, n))
&& ( keytag & NSEC3_ITERATION_COUNT_HIGH
|| ( nsec3_covers_name(n, name, opt_out)
/* NSEC should cover, but not match name...
* Unless it is wildcard match, but then we have to check
* that rrset->rr_type is not enlisted, because otherwise
* it should have matched the wildcard.
* Unless it is wildcard match, but then we have to
* check that rrset->rr_type is not enlisted,
* because otherwise it should have matched the
* wildcard.
*
* Also no CNAME... cause that should have matched too.
*/
&& ( !nsec3_matches_name(n, name)
|| ( name[0] == 1 && name[1] == (uint8_t)'*'
&& !bitmap_has_type(bitmap, rrset->rr_type)
&& !bitmap_has_type(bitmap, GETDNS_RRTYPE_CNAME)
&& !bitmap_has_type(bitmap,
GETDNS_RRTYPE_CNAME)
)
)
&& (keytag = a_key_signed_rrset(dnskey, n))) {
)
)
) {
debug_sec_print_rrset("NSEC3: ", n);
debug_sec_print_dname("covered: ", name);
@ -1869,10 +1921,13 @@ static int nsec3_find_next_closer(
* (if we came here via getdns_validate_dnssec) in which case
* rcode is always NOERROR.
*/
if (my_opt_out)
if (my_opt_out || keytag & NSEC3_ITERATION_COUNT_HIGH)
return keytag;
nc_name += *nc_name + 1;
if (_dname_len(nc_name) > sizeof(wc_name) - 2)
return 0;
else
(void) memcpy(wc_name + 2, nc_name, _dname_len(nc_name));
return find_nsec_covering_name(dnskey, rrset, wc_name, opt_out);
@ -1882,8 +1937,10 @@ static int nsec3_find_next_closer(
* Does a key from keyset dnskey prove the nonexistence of the (name, type)
* tuple in rrset?
*
* On success returns the keytag (+0x10000) of the key that signed the proof.
* Or else returns 0.
* On success returns the keytag + SIGNATURE_VERIFIED (0x10000) of the key
* that signed the proof.
* Or in case there were NSEC3's with too high iteration count for the
* verifying key: it returns keytag + NSEC3_ITERATION_COUNT_HIGH (0x20000)
*/
static int key_proves_nonexistance(
getdns_rrset *keyset, getdns_rrset *rrset, int *opt_out)
@ -1960,8 +2017,7 @@ static int key_proves_nonexistance(
*
* - Or a wildcard match without the type. The wildcard owner name
* match has special handing in the find_nsec_covering_name function.
* We still expect a NSEC covering the name though. For names with
* label < '*' there will thus be two NSECs. (is this true?)
* We still expect a NSEC covering the name though.
*/
/* The NSEC Name error case
@ -2021,7 +2077,12 @@ static int key_proves_nonexistance(
}
debug_sec_print_dname("Closest Encloser: ", ce_name);
memcpy(wc_name + 2, ce_name, _dname_len(ce_name));
if (_dname_len(ce_name) > sizeof(wc_name) - 2)
return 0;
else
(void) memcpy(wc_name+2, ce_name, _dname_len(ce_name));
debug_sec_print_dname(" Wildcard: ", wc_name);
return find_nsec_covering_name(keyset, rrset, wc_name, NULL);
@ -2075,13 +2136,12 @@ static int key_proves_nonexistance(
|| !bitmap_has_type(bitmap, GETDNS_RRTYPE_NS)
|| bitmap_has_type(bitmap, GETDNS_RRTYPE_SOA))
/* The qname must match the NSEC3!
* (expensive tests done last)
*/
&& nsec3_matches_name(ce, rrset->name)
/* It must have a valid signature */
&& (keytag = a_key_signed_rrset(keyset, ce))
/* And it must have a valid signature */
&& (keytag = a_key_signed_rrset(keyset, ce))) {
/* The qname must match the NSEC3 */
&& ( keytag & NSEC3_ITERATION_COUNT_HIGH
|| nsec3_matches_name(ce, rrset->name))) {
debug_sec_print_rrset("NSEC3 No Data for: ", rrset);
return keytag;
@ -2092,10 +2152,9 @@ static int key_proves_nonexistance(
* There are a few NSEC NODATA cases where qname doesn't match
* NSEC->name:
*
* - NSEC3 ownername match for qtype != NSEC3 (TODO?)
* - NSEC3 ownername match for qtype == NSEC3 (TODO?)
* - Wildcard NODATA (wildcard owner name match has special handing
* find_nsec_covering_name())
* - Opt-In DS NODATA (TODO, don't understand yet)
*/
/* The NSEC3 Name error case
@ -2124,21 +2183,25 @@ static int key_proves_nonexistance(
* here (instead of bogus) when DS is also missing.
* Should we not have followed the delegation then
* too?
* The NSEC could come from a parent zone!
*
*/
|| bitmap_has_type(bitmap, GETDNS_RRTYPE_DNAME)
|| ( bitmap_has_type(bitmap, GETDNS_RRTYPE_NS)
&& !bitmap_has_type(bitmap, GETDNS_RRTYPE_SOA)
)
|| !nsec3_matches_name(ce, ce_name)
|| !a_key_signed_rrset(keyset, ce))
|| !(keytag = a_key_signed_rrset(keyset, ce))
|| ( !(keytag & NSEC3_ITERATION_COUNT_HIGH)
&& !nsec3_matches_name(ce, ce_name)))
continue;
debug_sec_print_rrset("Closest Encloser: ", ce);
debug_sec_print_dname("Closest Encloser: ", ce_name);
debug_sec_print_dname(" Next closer: ", nc_name);
if ((keytag = nsec3_find_next_closer(
if ( keytag & NSEC3_ITERATION_COUNT_HIGH
|| (keytag = nsec3_find_next_closer(
keyset, rrset, nc_name, opt_out)))
return keytag;
@ -2180,7 +2243,7 @@ static int chain_node_get_trusted_keys(
node->dnskey_signer = keytag;
return GETDNS_DNSSEC_SECURE;
}
/* ta is ZSK */
/* ta is parent's ZSK */
if ((keytag = key_proves_nonexistance(ta, &node->ds, NULL))) {
node->ds_signer = keytag;
return GETDNS_DNSSEC_INSECURE;
@ -2252,7 +2315,8 @@ static int chain_head_validate_with_ta(chain_head *head, getdns_rrset *ta)
} else if ((keytag = key_proves_nonexistance(
keys, &head->rrset, &opt_out))) {
head->signer = keytag;
return opt_out ? GETDNS_DNSSEC_INSECURE : GETDNS_DNSSEC_SECURE;
return opt_out || (keytag & NSEC3_ITERATION_COUNT_HIGH)
? GETDNS_DNSSEC_INSECURE : GETDNS_DNSSEC_SECURE;
}
return GETDNS_DNSSEC_BOGUS;
}