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/* Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz>
* SPDX-License-Identifier: GPL-3.0-or-later
*/
/** @file iterate.c
*
* This builtin module is mainly active in the consume phase.
* Primary responsibilities:
* - Classify the packet as auth/nonauth and change its AA flag accordingly.
* - Pick interesting RRs to kr_request::answ_selected and ::auth_selected,
* NEW: and classify their rank, except for validation status.
* - Update kr_query::zone_cut (in case of referral).
* - Interpret CNAMEs.
* - Prepare the followup query - either inline or as another kr_query
* (CNAME jumps create a new "sibling" query).
*/
#include <sys/time.h>
#include <arpa/inet.h>
#include <contrib/cleanup.h>
#include <libknot/descriptor.h>
#include <libknot/rrtype/rdname.h>
#include <libknot/rrtype/rrsig.h>
#include "lib/layer/iterate.h"
#include "lib/resolve.h"
#include "lib/rplan.h"
#include "lib/defines.h"
#include "lib/selection.h"
#include "lib/module.h"
#include "lib/dnssec/ta.h"
#define VERBOSE_MSG(...) kr_log_q(req->current_query, ITERATOR, __VA_ARGS__)
#define QVERBOSE_MSG(qry, ...) kr_log_q(qry, ITERATOR, __VA_ARGS__)
#define WITH_VERBOSE(qry) if (kr_log_is_debug_qry(ITERATOR, (qry)))
/* Iterator often walks through packet section, this is an abstraction. */
typedef int (*rr_callback_t)(const knot_rrset_t *, unsigned, struct kr_request *);
/** Return minimized QNAME/QTYPE for current zone cut. */
static const knot_dname_t *minimized_qname(struct kr_query *query, uint16_t *qtype)
{
/* Minimization disabled. */
const knot_dname_t *qname = query->sname;
if (qname[0] == '\0' || query->flags.NO_MINIMIZE || query->flags.STUB) {
return qname;
}
/* Minimize name to contain current zone cut + 1 label. */
int cut_labels = knot_dname_labels(query->zone_cut.name, NULL);
int qname_labels = knot_dname_labels(qname, NULL);
while(qname[0] && qname_labels > cut_labels + 1) {
qname = knot_wire_next_label(qname, NULL);
qname_labels -= 1;
}
/* Hide QTYPE if minimized. */
if (qname != query->sname) {
*qtype = KNOT_RRTYPE_NS;
}
return qname;
}
/** Answer is paired to query. */
static bool is_paired_to_query(const knot_pkt_t *answer, struct kr_query *query)
{
uint16_t qtype = query->stype;
const knot_dname_t *qname = minimized_qname(query, &qtype);
/* ID should already match, thanks to session_tasklist_del_msgid()
* in worker_submit(), but it won't hurt to check again. */
return query->id == knot_wire_get_id(answer->wire) &&
knot_wire_get_qdcount(answer->wire) == 1 &&
query->sclass == knot_pkt_qclass(answer) &&
qtype == knot_pkt_qtype(answer) &&
/* qry->secret had been xor-applied to answer already,
* so this also checks for correctness of case randomization */
knot_dname_is_equal(qname, kr_pkt_qname_raw(answer));
}
/** Relaxed rule for AA, either AA=1 or SOA matching zone cut is required. */
static bool is_authoritative(const knot_pkt_t *answer, struct kr_query *query)
{
if (knot_wire_get_aa(answer->wire)) {
return true;
}
const knot_pktsection_t *ns = knot_pkt_section(answer, KNOT_AUTHORITY);
for (unsigned i = 0; i < ns->count; ++i) {
const knot_rrset_t *rr = knot_pkt_rr(ns, i);
if (rr->type == KNOT_RRTYPE_SOA
&& knot_dname_in_bailiwick(rr->owner, query->zone_cut.name) >= 0) {
return true;
}
}
#ifndef STRICT_MODE
/* Last resort to work around broken auths, if the zone cut is at the QNAME. */
if (knot_dname_is_equal(query->zone_cut.name, knot_pkt_qname(answer))) {
return true;
}
#endif
/* Some authoritative servers are hopelessly broken, allow lame answers in permissive mode. */
if (query->flags.PERMISSIVE) {
return true;
}
return false;
}
int kr_response_classify(const knot_pkt_t *pkt)
{
const knot_pktsection_t *an = knot_pkt_section(pkt, KNOT_ANSWER);
switch (knot_wire_get_rcode(pkt->wire)) {
case KNOT_RCODE_NOERROR:
return (an->count == 0) ? PKT_NODATA : PKT_NOERROR;
case KNOT_RCODE_NXDOMAIN:
return PKT_NXDOMAIN;
case KNOT_RCODE_REFUSED:
return PKT_REFUSED;
default:
return PKT_ERROR;
}
}
/** @internal Filter ANY or loopback addresses. */
static bool is_valid_addr(const uint8_t *addr, size_t len)
{
if (len == sizeof(struct in_addr)) {
/* Filter ANY and 127.0.0.0/8 */
uint32_t ip_host; /* Memcpy is safe for unaligned case (on non-x86) */
memcpy(&ip_host, addr, sizeof(ip_host));
ip_host = ntohl(ip_host);
if (ip_host == 0 || (ip_host & 0xff000000) == 0x7f000000) {
return false;
}
} else if (len == sizeof(struct in6_addr)) {
struct in6_addr ip6_mask;
memset(&ip6_mask, 0, sizeof(ip6_mask));
/* All except last byte are zeroed, last byte defines ANY/::1 */
if (memcmp(addr, ip6_mask.s6_addr, sizeof(ip6_mask.s6_addr) - 1) == 0) {
return (addr[len - 1] > 1);
}
}
return true;
}
/** @internal Update NS address from record \a rr. Return _FAIL on error. */
static int update_nsaddr(const knot_rrset_t *rr, struct kr_query *query, int *glue_cnt)
{
if (rr->type == KNOT_RRTYPE_A || rr->type == KNOT_RRTYPE_AAAA) {
const knot_rdata_t *rdata = rr->rrs.rdata;
const int a_len = rr->type == KNOT_RRTYPE_A
? sizeof(struct in_addr) : sizeof(struct in6_addr);
if (a_len != rdata->len) {
QVERBOSE_MSG(query, "<= ignoring invalid glue, length %d != %d\n",
(int)rdata->len, a_len);
return KR_STATE_FAIL;
}
char name_str[KR_DNAME_STR_MAXLEN];
char addr_str[INET6_ADDRSTRLEN];
WITH_VERBOSE(query) {
const int af = (rr->type == KNOT_RRTYPE_A) ? AF_INET : AF_INET6;
knot_dname_to_str(name_str, rr->owner, sizeof(name_str));
name_str[sizeof(name_str) - 1] = 0;
inet_ntop(af, rdata->data, addr_str, sizeof(addr_str));
}
if (!(query->flags.ALLOW_LOCAL) &&
!is_valid_addr(rdata->data, rdata->len)) {
QVERBOSE_MSG(query, "<= ignoring invalid glue for "
"'%s': '%s'\n", name_str, addr_str);
return KR_STATE_CONSUME; /* Ignore invalid addresses */
}
int ret = kr_zonecut_add(&query->zone_cut, rr->owner, rdata->data, rdata->len);
if (ret != 0) {
return KR_STATE_FAIL;
}
++*glue_cnt; /* reduced verbosity */
/* QVERBOSE_MSG(query, "<= using glue for "
"'%s': '%s'\n", name_str, addr_str);
*/
}
return KR_STATE_CONSUME;
}
enum { GLUE_COUNT_THROTTLE = 26 };
/** @internal From \a pkt, fetch glue records for name \a ns, and update the cut etc.
*
* \param glue_cnt the number of accepted addresses (to be incremented)
*/
static void fetch_glue(knot_pkt_t *pkt, const knot_dname_t *ns, bool in_bailiwick,
struct kr_request *req, const struct kr_query *qry, int *glue_cnt)
{
ranked_rr_array_t *selected[] = kr_request_selected(req);
for (knot_section_t i = KNOT_ANSWER; i <= KNOT_ADDITIONAL; ++i) {
const knot_pktsection_t *sec = knot_pkt_section(pkt, i);
for (unsigned k = 0; k < sec->count; ++k) {
const knot_rrset_t *rr = knot_pkt_rr(sec, k);
if (!knot_dname_is_equal(ns, rr->owner)) {
continue;
}
if ((rr->type != KNOT_RRTYPE_A) &&
(rr->type != KNOT_RRTYPE_AAAA)) {
continue;
}
uint8_t rank = (in_bailiwick && i == KNOT_ANSWER)
? (KR_RANK_INITIAL | KR_RANK_AUTH) : KR_RANK_OMIT;
(void) kr_ranked_rrarray_add(selected[i], rr, rank,
false, qry->uid, &req->pool);
if ((rr->type == KNOT_RRTYPE_A) &&
(req->ctx->options.NO_IPV4)) {
QVERBOSE_MSG(qry, "<= skipping IPv4 glue due to network settings\n");
continue;
}
if ((rr->type == KNOT_RRTYPE_AAAA) &&
(req->ctx->options.NO_IPV6)) {
QVERBOSE_MSG(qry, "<= skipping IPv6 glue due to network settings\n");
continue;
}
(void) update_nsaddr(rr, req->current_query, glue_cnt);
/* If we reach limit on total glue addresses,
* we only load the first one per NS name (the one just above). */
if (*glue_cnt > GLUE_COUNT_THROTTLE)
break;
}
}
}
/** Attempt to find glue for given nameserver name (best effort). */
static bool has_glue(knot_pkt_t *pkt, const knot_dname_t *ns)
{
for (knot_section_t i = KNOT_ANSWER; i <= KNOT_ADDITIONAL; ++i) {
const knot_pktsection_t *sec = knot_pkt_section(pkt, i);
for (unsigned k = 0; k < sec->count; ++k) {
const knot_rrset_t *rr = knot_pkt_rr(sec, k);
if (knot_dname_is_equal(ns, rr->owner) &&
(rr->type == KNOT_RRTYPE_A || rr->type == KNOT_RRTYPE_AAAA)) {
return true;
}
}
}
return false;
}
/** @internal Update the cut with another NS(+glue) record.
* @param current_cut is cut name before this packet.
* @return _DONE if cut->name changes, _FAIL on error, and _CONSUME otherwise. */
static int update_cut(knot_pkt_t *pkt, const knot_rrset_t *rr,
struct kr_request *req, const knot_dname_t *current_cut,
int *glue_cnt)
{
struct kr_query *qry = req->current_query;
struct kr_zonecut *cut = &qry->zone_cut;
int state = KR_STATE_CONSUME;
/* New authority MUST be at/below the authority of the current cut;
* also qname must be below new authority;
* otherwise it's a possible cache injection attempt. */
const bool ok = knot_dname_in_bailiwick(rr->owner, current_cut) >= 0
&& knot_dname_in_bailiwick(qry->sname, rr->owner) >= 0;
if (!ok) {
VERBOSE_MSG("<= authority: ns outside bailiwick\n");
qry->server_selection.error(qry, req->upstream.transport, KR_SELECTION_LAME_DELEGATION);
#ifdef STRICT_MODE
return KR_STATE_FAIL;
#else
/* Workaround: ignore out-of-bailiwick NSs for authoritative answers,
* but fail for referrals. This is important to detect lame answers. */
if (knot_pkt_section(pkt, KNOT_ANSWER)->count == 0) {
state = KR_STATE_FAIL;
}
return state;
#endif
}
/* Update zone cut name */
if (!knot_dname_is_equal(rr->owner, cut->name)) {
/* Remember parent cut and descend to new (keep keys and TA). */
struct kr_zonecut *parent = mm_alloc(&req->pool, sizeof(*parent));
if (parent) {
memcpy(parent, cut, sizeof(*parent));
kr_zonecut_init(cut, rr->owner, &req->pool);
cut->key = parent->key;
cut->trust_anchor = parent->trust_anchor;
cut->parent = parent;
} else {
kr_zonecut_set(cut, rr->owner);
}
state = KR_STATE_DONE;
}
/* Fetch glue for each NS */
knot_rdata_t *rdata_i = rr->rrs.rdata;
for (unsigned i = 0; i < rr->rrs.count;
++i, rdata_i = knot_rdataset_next(rdata_i)) {
const knot_dname_t *ns_name = knot_ns_name(rdata_i);
/* Glue is mandatory for NS below zone */
if (knot_dname_in_bailiwick(ns_name, rr->owner) >= 0
&& !has_glue(pkt, ns_name)) {
const char *msg =
"<= authority: missing mandatory glue, skipping NS";
WITH_VERBOSE(qry) {
auto_free char *ns_str = kr_dname_text(ns_name);
VERBOSE_MSG("%s %s\n", msg, ns_str);
}
continue;
}
int ret = kr_zonecut_add(cut, ns_name, NULL, 0);
kr_assert(!ret);
/* Choose when to use glue records. */
const bool in_bailiwick =
knot_dname_in_bailiwick(ns_name, current_cut) >= 0;
bool do_fetch;
if (qry->flags.PERMISSIVE) {
do_fetch = true;
} else if (qry->flags.STRICT) {
/* Strict mode uses only mandatory glue. */
do_fetch = knot_dname_in_bailiwick(ns_name, cut->name) >= 0;
} else {
/* Normal mode uses in-bailiwick glue. */
do_fetch = in_bailiwick;
}
if (do_fetch) {
fetch_glue(pkt, ns_name, in_bailiwick, req, qry, glue_cnt);
}
}
return state;
}
/** Compute rank appropriate for RRs present in the packet.
* @param answer whether the RR is from answer or authority section
* @param is_nonauth: from referral or forwarding (etc.) */
static uint8_t get_initial_rank(const knot_rrset_t *rr, const struct kr_query *qry,
const bool answer, const bool is_nonauth)
{
/* For RRSIGs, ensure the KR_RANK_AUTH flag corresponds to the signed RR. */
uint16_t type = kr_rrset_type_maysig(rr);
if (qry->flags.CACHED) {
return rr->additional ? *(uint8_t *)rr->additional : KR_RANK_OMIT;
/* ^^ Current use case for "cached" RRs without rank: hints module. */
}
if (answer || type == KNOT_RRTYPE_DS
|| type == KNOT_RRTYPE_SOA /* needed for aggressive negative caching */
|| type == KNOT_RRTYPE_NSEC || type == KNOT_RRTYPE_NSEC3) {
/* We almost always want these validated, and it should be possible. */
return KR_RANK_INITIAL | KR_RANK_AUTH;
}
/* Be aggressive: try to validate anything else (almost never extra latency). */
return KR_RANK_TRY;
/* TODO: this classifier of authoritativity may not be perfect yet. */
}
static int pick_authority(knot_pkt_t *pkt, struct kr_request *req, bool to_wire)
{
struct kr_query *qry = req->current_query;
const knot_pktsection_t *ns = knot_pkt_section(pkt, KNOT_AUTHORITY);
const knot_dname_t *zonecut_name = qry->zone_cut.name;
bool referral = !knot_wire_get_aa(pkt->wire);
if (referral) {
/* zone cut already updated by process_authority()
* use parent zonecut name */
zonecut_name = qry->zone_cut.parent ? qry->zone_cut.parent->name : qry->zone_cut.name;
to_wire = false;
}
for (unsigned i = 0; i < ns->count; ++i) {
const knot_rrset_t *rr = knot_pkt_rr(ns, i);
if (rr->rclass != KNOT_CLASS_IN
|| knot_dname_in_bailiwick(rr->owner, zonecut_name) < 0) {
continue;
}
uint8_t rank = get_initial_rank(rr, qry, false,
qry->flags.FORWARD || referral);
int ret = kr_ranked_rrarray_add(&req->auth_selected, rr,
rank, to_wire, qry->uid, &req->pool);
if (ret < 0) {
return ret;
}
}
return kr_ok();
}
static int process_authority(knot_pkt_t *pkt, struct kr_request *req)
{
struct kr_query *qry = req->current_query;
if (kr_fails_assert(!qry->flags.STUB))
return KR_STATE_FAIL;
int result = KR_STATE_CONSUME;
if (qry->flags.FORWARD) {
return result;
}
const knot_pktsection_t *ns = knot_pkt_section(pkt, KNOT_AUTHORITY);
const knot_pktsection_t *an = knot_pkt_section(pkt, KNOT_ANSWER);
#ifdef STRICT_MODE
/* AA, terminate resolution chain. */
if (knot_wire_get_aa(pkt->wire)) {
return KR_STATE_CONSUME;
}
#else
/* Work around servers sending back CNAME with different delegation and no AA. */
if (an->count > 0 && ns->count > 0) {
const knot_rrset_t *rr = knot_pkt_rr(an, 0);
if (rr->type == KNOT_RRTYPE_CNAME) {
return KR_STATE_CONSUME;
}
/* Work around for these NSs which are authoritative both for
* parent and child and mixes data from both zones in single answer */
if (knot_wire_get_aa(pkt->wire) &&
(rr->type == qry->stype) &&
(knot_dname_is_equal(rr->owner, qry->sname))) {
return KR_STATE_CONSUME;
}
}
#endif
/* Remember current bailiwick for NS processing. */
const knot_dname_t *current_zone_cut = qry->zone_cut.name;
bool ns_record_exists = false;
int glue_cnt = 0;
int ns_count = 0;
/* Update zone cut information. */
for (unsigned i = 0; i < ns->count; ++i) {
const knot_rrset_t *rr = knot_pkt_rr(ns, i);
if (rr->type == KNOT_RRTYPE_NS) {
ns_record_exists = true;
int state = update_cut(pkt, rr, req, current_zone_cut, &glue_cnt);
switch(state) {
case KR_STATE_DONE: result = state; break;
case KR_STATE_FAIL: return state; break;
default: /* continue */ break;
}
if (++ns_count >= 13) {
VERBOSE_MSG("<= authority: many glue NSs, skipping the rest\n");
break;
}
} else if (rr->type == KNOT_RRTYPE_SOA
&& knot_dname_in_bailiwick(rr->owner, qry->zone_cut.name) > 0) {
/* SOA below cut in authority indicates different authority,
* but same NS set. */
qry->zone_cut.name = knot_dname_copy(rr->owner, &req->pool);
}
}
/* Nameserver is authoritative for both parent side and the child side of the
* delegation may respond with an NS record in the answer section, and still update
* the zone cut (this e.g. happens on the `nrl.navy.mil.` zone cut).
* By updating the zone cut, we can continue with QNAME minimization,
* as the current code is only able to minimize one label below a zone cut. */
if (!ns_record_exists && knot_wire_get_aa(pkt->wire)) {
for (unsigned i = 0; i < an->count; ++i) {
const knot_rrset_t *rr = knot_pkt_rr(an, i);
if (rr->type == KNOT_RRTYPE_NS
&& knot_dname_in_bailiwick(rr->owner, qry->zone_cut.name) > 0
/* "confusing" NS records can happen e.g. on a CNAME chain */
&& knot_dname_in_bailiwick(qry->sname, rr->owner) >= 0) {
/* NS below cut in authority indicates different authority,
* but same NS set. */
qry->zone_cut.name = knot_dname_copy(rr->owner, &req->pool);
}
}
}
if (glue_cnt) {
VERBOSE_MSG("<= loaded %d glue addresses\n", glue_cnt);
}
if (glue_cnt > GLUE_COUNT_THROTTLE) {
VERBOSE_MSG("<= (some may have been omitted due to being too many)\n");
}
if ((qry->flags.DNSSEC_WANT) && (result == KR_STATE_CONSUME)) {
if (knot_wire_get_aa(pkt->wire) == 0 &&
knot_wire_get_ancount(pkt->wire) == 0 &&
ns_record_exists) {
/* Unhelpful referral
Prevent from validating as an authoritative answer */
result = KR_STATE_DONE;
}
}
/* CONSUME => Unhelpful referral.
* DONE => Zone cut updated. */
return result;
}
static int finalize_answer(knot_pkt_t *pkt, struct kr_request *req)
{
/* Finalize header */
knot_pkt_t *answer = kr_request_ensure_answer(req);
if (answer) {
knot_wire_set_rcode(answer->wire, knot_wire_get_rcode(pkt->wire));
req->state = KR_STATE_DONE;
}
return req->state;
}
static int unroll_cname(knot_pkt_t *pkt, struct kr_request *req, bool referral, const knot_dname_t **cname_ret)
{
struct kr_query *query = req->current_query;
if (kr_fails_assert(!query->flags.STUB))
return KR_STATE_FAIL;
/* Process answer type */
const knot_pktsection_t *an = knot_pkt_section(pkt, KNOT_ANSWER);
const knot_dname_t *cname = NULL;
const knot_dname_t *pending_cname = query->sname;
bool is_final = (query->parent == NULL);
bool strict_mode = (query->flags.STRICT);
query->cname_depth = query->cname_parent ? query->cname_parent->cname_depth : 1;
do {
/* CNAME was found at previous iteration, but records may not follow the correct order.
* Try to find records for pending_cname owner from section start. */
cname = pending_cname;
size_t cname_answ_selected_i = -1;
bool cname_is_occluded = false; /* whether `cname` is in a DNAME's bailiwick */
pending_cname = NULL;
const int cname_labels = knot_dname_labels(cname, NULL);
for (unsigned i = 0; i < an->count; ++i) {
const knot_rrset_t *rr = knot_pkt_rr(an, i);
/* Skip the RR if its owner+type doesn't interest us. */
const uint16_t type = kr_rrset_type_maysig(rr);
const bool type_OK = rr->type == query->stype || type == query->stype
|| type == KNOT_RRTYPE_CNAME;
if (rr->rclass != KNOT_CLASS_IN
|| knot_dname_in_bailiwick(rr->owner, query->zone_cut.name) < 0) {
continue;
}
const bool all_OK = type_OK && knot_dname_is_equal(rr->owner, cname);
const bool to_wire = is_final && !referral;
if (!all_OK && type == KNOT_RRTYPE_DNAME
&& knot_dname_in_bailiwick(cname, rr->owner) >= 1) {
/* This DNAME (or RRSIGs) cover the current target (`cname`),
* so it is interesting and will occlude its CNAME.
* We rely on CNAME being sent along with DNAME
* (mandatory unless YXDOMAIN). */
cname_is_occluded = true;
uint8_t rank = get_initial_rank(rr, query, true,
query->flags.FORWARD || referral);
int ret = kr_ranked_rrarray_add(&req->answ_selected, rr,
rank, to_wire, query->uid, &req->pool);
if (ret < 0) {
return KR_STATE_FAIL;
}
}
if (!all_OK) {
continue;
}
if (rr->type == KNOT_RRTYPE_RRSIG) {
int rrsig_labels = knot_rrsig_labels(rr->rrs.rdata);
if (rrsig_labels > cname_labels) {
/* clearly wrong RRSIG, don't pick it.
* don't fail immediately,
* let validator work. */
continue;
}
if (rrsig_labels < cname_labels) {
query->flags.DNSSEC_WEXPAND = true;
}
}
/* Process records matching current SNAME */
if (!is_final) {
int cnt_ = 0;
int state = update_nsaddr(rr, query->parent, &cnt_);
if (state & KR_STATE_FAIL) {
return state;
}
}
uint8_t rank = get_initial_rank(rr, query, true,
query->flags.FORWARD || referral);
int ret = kr_ranked_rrarray_add(&req->answ_selected, rr,
rank, to_wire, query->uid, &req->pool);
if (ret < 0) {
return KR_STATE_FAIL;
}
cname_answ_selected_i = ret;
/* Select the next CNAME target, but don't jump immediately.
* There can be records for "old" cname (RRSIGs are interesting);
* more importantly there might be a DNAME for `cname_is_occluded`. */
if (query->stype != KNOT_RRTYPE_CNAME && rr->type == KNOT_RRTYPE_CNAME) {
pending_cname = knot_cname_name(rr->rrs.rdata);
if (!pending_cname) {
break;
}
}
}
if (!pending_cname) {
break;
}
if (cname_is_occluded) {
req->answ_selected.at[cname_answ_selected_i]->dont_cache = true;
}
if (++(query->cname_depth) > KR_CNAME_CHAIN_LIMIT) {
VERBOSE_MSG("<= error: CNAME chain exceeded max length %d\n",
/* people count objects from 0, no CNAME = 0 */
(int)KR_CNAME_CHAIN_LIMIT - 1);
return KR_STATE_FAIL;
}
if (knot_dname_is_equal(cname, pending_cname)) {
VERBOSE_MSG("<= error: CNAME chain loop detected\n");
return KR_STATE_FAIL;
}
/* In strict mode, explicitly fetch each CNAME target. */
if (strict_mode) {
cname = pending_cname;
break;
}
/* Information outside bailiwick is not trusted. */
if (knot_dname_in_bailiwick(pending_cname, query->zone_cut.name) < 0) {
cname = pending_cname;
break;
}
/* The validator still can't handle multiple zones in one answer,
* so we only follow if a single label is replaced.
* Forwarding appears to be even more sensitive to this.
* TODO: iteration can probably handle the remaining cases,
* but overall it would be better to have a smarter validator
* (and thus save roundtrips).*/
const int pending_labels = knot_dname_labels(pending_cname, NULL);
if (pending_labels != cname_labels) {
cname = pending_cname;
break;
}
if (knot_dname_matched_labels(pending_cname, cname) != cname_labels - 1
|| query->flags.FORWARD) {
cname = pending_cname;
break;
}
} while (true);
*cname_ret = cname;
return kr_ok();
}
static int process_referral_answer(knot_pkt_t *pkt, struct kr_request *req)
{
const knot_dname_t *cname = NULL;
int state = unroll_cname(pkt, req, true, &cname);
struct kr_query *query = req->current_query;
if (state != kr_ok()) {
query->server_selection.error(query, req->upstream.transport, KR_SELECTION_BAD_CNAME);
return KR_STATE_FAIL;
}
if (!(query->flags.CACHED)) {
/* If not cached (i.e. got from upstream)
* make sure that this is not an authoritative answer
* (even with AA=1) for other layers.
* There can be answers with AA=1,
* empty answer section and NS in authority.
* Clearing of AA prevents them from
* caching in the packet cache.
* If packet already cached, don't touch him. */
knot_wire_clear_aa(pkt->wire);
}
state = pick_authority(pkt, req, false);
return state == kr_ok() ? KR_STATE_DONE : KR_STATE_FAIL;
}
static int process_final(knot_pkt_t *pkt, struct kr_request *req,
const knot_dname_t *cname)
{
const int pkt_class = kr_response_classify(pkt);
struct kr_query *query = req->current_query;
ranked_rr_array_t *array = &req->answ_selected;
for (size_t i = 0; i < array->len; ++i) {
const knot_rrset_t *rr = array->at[i]->rr;
if (!knot_dname_is_equal(rr->owner, cname)) {
continue;
}
if ((rr->rclass != query->sclass) ||
(rr->type != query->stype)) {
continue;
}
const bool to_wire = ((pkt_class & (PKT_NXDOMAIN|PKT_NODATA)) != 0);
const int state = pick_authority(pkt, req, to_wire);
if (state != kr_ok()) {
return KR_STATE_FAIL;
}
if (!array->at[i]->to_wire) {
const size_t last_idx = array->len - 1;
size_t j = i;
ranked_rr_array_entry_t *entry = array->at[i];
/* Relocate record to the end, after current cname */
while (j < last_idx) {
array->at[j] = array->at[j + 1];
++j;
}
array->at[last_idx] = entry;
entry->to_wire = true;
}
return finalize_answer(pkt, req);
}
return kr_ok();
}
static int process_answer(knot_pkt_t *pkt, struct kr_request *req)
{
struct kr_query *query = req->current_query;
/* Response for minimized QNAME. Note that current iterator's minimization
* is only able ask one label below a zone cut.
* NODATA => may be empty non-terminal, retry (found zone cut)
* NOERROR => found zone cut, retry, except the case described below
* NXDOMAIN => parent is zone cut, retry as a workaround for bad authoritatives
*/
const bool is_final = (query->parent == NULL);
const int pkt_class = kr_response_classify(pkt);
const knot_dname_t * pkt_qname = knot_pkt_qname(pkt);
if (!knot_dname_is_equal(pkt_qname, query->sname) &&
(pkt_class & (PKT_NOERROR|PKT_NXDOMAIN|PKT_REFUSED|PKT_NODATA))) {
/* Check for parent server that is authoritative for child zone,
* several CCTLDs where the SLD and TLD have the same name servers */
const knot_pktsection_t *ans = knot_pkt_section(pkt, KNOT_ANSWER);
if ((pkt_class & (PKT_NOERROR)) && ans->count > 0 &&
knot_dname_is_equal(pkt_qname, query->zone_cut.name)) {
VERBOSE_MSG("<= continuing with qname minimization\n");
} else {
/* fall back to disabling minimization */
VERBOSE_MSG("<= retrying with non-minimized name\n");
query->flags.NO_MINIMIZE = true;
}
return KR_STATE_CONSUME;
}
/* This answer didn't improve resolution chain, therefore must be authoritative (relaxed to negative). */
if (!is_authoritative(pkt, query)) {
if (!(query->flags.FORWARD) &&
pkt_class & (PKT_NXDOMAIN|PKT_NODATA)) {
query->server_selection.error(query, req->upstream.transport, KR_SELECTION_LAME_DELEGATION);
VERBOSE_MSG("<= lame response: non-auth sent negative response\n");
return KR_STATE_FAIL;
}
}
const knot_dname_t *cname = NULL;
/* Process answer type */
int state = unroll_cname(pkt, req, false, &cname);
if (state != kr_ok()) {
query->server_selection.error(query, req->upstream.transport, KR_SELECTION_BAD_CNAME);
return state;
}
/* Make sure that this is an authoritative answer (even with AA=0) for other layers */
knot_wire_set_aa(pkt->wire);
/* Either way it resolves current query. */
query->flags.RESOLVED = true;
/* Follow canonical name as next SNAME. */
if (!knot_dname_is_equal(cname, query->sname)) {
/* Check if target record has been already copied */
query->flags.CNAME = true;
if (is_final) {
state = process_final(pkt, req, cname);
if (state != kr_ok()) {
return state;
}
} else if ((query->flags.FORWARD) &&
((query->stype == KNOT_RRTYPE_DS) ||
(query->stype == KNOT_RRTYPE_NS))) {
/* CNAME'ed answer for DS or NS subquery.
* Treat it as proof of zonecut nonexistence. */
return KR_STATE_DONE;
}
VERBOSE_MSG("<= cname chain, following\n");
/* Check if the same query was followed in the same CNAME chain. */
for (const struct kr_query *q = query->cname_parent; q != NULL;
q = q->cname_parent) {
if (q->sclass == query->sclass &&
q->stype == query->stype &&
knot_dname_is_equal(q->sname, cname)) {
VERBOSE_MSG("<= cname chain loop\n");
query->server_selection.error(query, req->upstream.transport, KR_SELECTION_BAD_CNAME);
return KR_STATE_FAIL;
}
}
struct kr_query *next = kr_rplan_push(&req->rplan, query->parent, cname, query->sclass, query->stype);
if (!next) {
return KR_STATE_FAIL;
}
next->flags.AWAIT_CUT = true;
/* Copy transitive flags from original query to CNAME followup. */
next->flags.TRACE = query->flags.TRACE;
next->flags.ALWAYS_CUT = query->flags.ALWAYS_CUT;
/* Original query might have turned minimization off, revert. */
next->flags.NO_MINIMIZE = req->options.NO_MINIMIZE;
if (query->flags.FORWARD) {
next->forward_flags.CNAME = true;
}
next->cname_parent = query;
/* Want DNSSEC if and only if it's possible to secure
* this name (i.e. iff it is covered by a TA) */
if (kr_ta_closest(req->ctx, cname, query->stype)) {
next->flags.DNSSEC_WANT = true;
} else {
next->flags.DNSSEC_WANT = false;
}
if (!(query->flags.FORWARD) ||
(query->flags.DNSSEC_WEXPAND)) {
state = pick_authority(pkt, req, false);
if (state != kr_ok()) {
return KR_STATE_FAIL;
}
}
} else if (!query->parent) {
/* Answer for initial query */
const bool to_wire = ((pkt_class & (PKT_NXDOMAIN|PKT_NODATA)) != 0);
state = pick_authority(pkt, req, to_wire);
if (state != kr_ok()) {
return KR_STATE_FAIL;
}
return finalize_answer(pkt, req);
} else {
/* Answer for sub-query; DS, IP for NS etc.
* It may contains NSEC \ NSEC3 records for
* data non-existence or wc expansion proving.
* If yes, they must be validated by validator.
* If no, authority section is unuseful.
* dnssec\nsec.c & dnssec\nsec3.c use
* rrsets from incoming packet.
* validator uses answer_selected & auth_selected.
* So, if nsec\nsec3 records are present in authority,
* pick_authority() must be called.
* TODO refactor nsec\nsec3 modules to work with
* answer_selected & auth_selected instead of incoming pkt. */
bool auth_is_unuseful = true;
const knot_pktsection_t *ns = knot_pkt_section(pkt, KNOT_AUTHORITY);
for (unsigned i = 0; i < ns->count; ++i) {
const knot_rrset_t *rr = knot_pkt_rr(ns, i);
if (rr->type == KNOT_RRTYPE_NSEC ||
rr->type == KNOT_RRTYPE_NSEC3) {
auth_is_unuseful = false;
break;
}
}
if (!auth_is_unuseful) {
state = pick_authority(pkt, req, false);
if (state != kr_ok()) {
return KR_STATE_FAIL;
}
}
}
return KR_STATE_DONE;
}
/** @internal like process_answer() but for the STUB mode. */
static int process_stub(knot_pkt_t *pkt, struct kr_request *req)
{
struct kr_query *query = req->current_query;
if (kr_fails_assert(query->flags.STUB))
return KR_STATE_FAIL;
/* Pick all answer RRs. */
const knot_pktsection_t *an = knot_pkt_section(pkt, KNOT_ANSWER);
for (unsigned i = 0; i < an->count; ++i) {
const knot_rrset_t *rr = knot_pkt_rr(an, i);
int err = kr_ranked_rrarray_add(&req->answ_selected, rr,
KR_RANK_OMIT | KR_RANK_AUTH, true, query->uid, &req->pool);
/* KR_RANK_AUTH: we don't have the records directly from
* an authoritative source, but we do trust the server and it's
* supposed to only send us authoritative records. */
if (err < 0) {
return KR_STATE_FAIL;
}
}
knot_wire_set_aa(pkt->wire);
query->flags.RESOLVED = true;
/* Pick authority RRs. */
int pkt_class = kr_response_classify(pkt);
const bool to_wire = ((pkt_class & (PKT_NXDOMAIN|PKT_NODATA)) != 0);
int err = pick_authority(pkt, req, to_wire);
if (err != kr_ok()) {
return KR_STATE_FAIL;
}
return finalize_answer(pkt, req);
}
/* State-less single resolution iteration step, not needed. */
static int reset(kr_layer_t *ctx) { return KR_STATE_PRODUCE; }
/* Set resolution context and parameters. */
static int begin(kr_layer_t *ctx)
{
if (ctx->state & (KR_STATE_DONE|KR_STATE_FAIL)) {
return ctx->state;
}
/*
* RFC7873 5.4 extends the QUERY operation code behaviour in order to
* be able to generate requests for server cookies. Such requests have
* QDCOUNT equal to zero and must contain a cookie option.
* Server cookie queries must be handled by the cookie module/layer
* before this layer.
*/
const knot_pkt_t *pkt = ctx->req->qsource.packet;
if (!pkt || knot_wire_get_qdcount(pkt->wire) == 0) {
return KR_STATE_FAIL;
}
struct kr_query *qry = ctx->req->current_query;
/* Avoid any other classes, and avoid any meta-types ~~except for ANY~~. */
if (qry->sclass != KNOT_CLASS_IN
|| (knot_rrtype_is_metatype(qry->stype)
/* && qry->stype != KNOT_RRTYPE_ANY hmm ANY seems broken ATM */)) {
knot_pkt_t *ans = kr_request_ensure_answer(ctx->req);
if (!ans) return ctx->req->state;
knot_wire_set_rcode(ans->wire, KNOT_RCODE_NOTIMPL);
return KR_STATE_FAIL;
}
return reset(ctx);
}
int kr_make_query(struct kr_query *query, knot_pkt_t *pkt)
{
/* Minimize QNAME (if possible). */
uint16_t qtype = query->stype;
const knot_dname_t *qname = minimized_qname(query, &qtype);
/* Form a query for the authoritative. */
knot_pkt_clear(pkt);
int ret = knot_pkt_put_question(pkt, qname, query->sclass, qtype);
if (ret != KNOT_EOK) {
return ret;
}
/* Query built, expect answer. */
query->id = kr_rand_bytes(2);
/* We must respect https://tools.ietf.org/html/rfc7766#section-6.2.1
* - When sending multiple queries over a TCP connection, clients MUST NOT
* reuse the DNS Message ID of an in-flight query on that connection.
*
* So, if query is going to be sent over TCP connection
* this id can be changed to avoid duplication with query that already was sent
* but didn't receive answer yet.
*/
knot_wire_set_id(pkt->wire, query->id);
pkt->parsed = pkt->size;
return kr_ok();
}
static int prepare_query(kr_layer_t *ctx, knot_pkt_t *pkt)
{
if (kr_fails_assert(pkt && ctx))
return KR_STATE_FAIL;
struct kr_request *req = ctx->req;
struct kr_query *query = req->current_query;
if (!query || ctx->state & (KR_STATE_DONE|KR_STATE_FAIL)) {
return ctx->state;
}
/* Make query */
int ret = kr_make_query(query, pkt);
if (ret != 0) {
return KR_STATE_FAIL;
}
WITH_VERBOSE(query) {
KR_DNAME_GET_STR(name_str, query->sname);
KR_RRTYPE_GET_STR(type_str, query->stype);
QVERBOSE_MSG(query, "'%s' type '%s' new uid was assigned .%02u, parent uid .%02u\n",
name_str, type_str, req->rplan.next_uid,
query->parent ? query->parent->uid : 0);
}
query->uid = req->rplan.next_uid;
req->rplan.next_uid += 1;
query->flags.CACHED = false; // in case it got left from earlier (unknown edge case)
return KR_STATE_CONSUME;
}
static bool satisfied_by_additional(const struct kr_query *qry)
{
const bool prereq = !qry->flags.STUB && !qry->flags.FORWARD && qry->flags.NONAUTH;
if (!prereq)
return false;
const struct kr_request *req = qry->request;
for (ssize_t i = req->add_selected.len - 1; i >= 0; --i) {
ranked_rr_array_entry_t *entry = req->add_selected.at[i];
if (entry->qry_uid != qry->uid)
break;
if (entry->rr->type == qry->stype
&& knot_dname_is_equal(entry->rr->owner, qry->sname)) {
return true;
}
}
return false;
}
/** Restrict all RRset TTLs to the specified bounds (if matching qry_uid). */
static void bound_ttls(ranked_rr_array_t *array, uint32_t qry_uid,
uint32_t ttl_min, uint32_t ttl_max)
{
for (ssize_t i = 0; i < array->len; ++i) {
if (array->at[i]->qry_uid != qry_uid)
continue;
uint32_t *ttl = &array->at[i]->rr->ttl;
if (*ttl < ttl_min) {
*ttl = ttl_min;
} else if (*ttl > ttl_max) {
*ttl = ttl_max;
}
}
}
/** Resolve input query or continue resolution with followups.
*
* This roughly corresponds to RFC1034, 5.3.3 4a-d.
*/
static int resolve(kr_layer_t *ctx, knot_pkt_t *pkt)
{
if (kr_fails_assert(pkt && ctx))
return KR_STATE_FAIL;
struct kr_request *req = ctx->req;
struct kr_query *query = req->current_query;
if (!query) {
return ctx->state;
}
query->flags.PKT_IS_SANE = false;
WITH_VERBOSE(query) {
if (query->flags.TRACE) {
auto_free char *pkt_text = kr_pkt_text(pkt);
VERBOSE_MSG("<= answer received:\n%s\n", pkt_text);
}
}
if (query->flags.RESOLVED || query->flags.BADCOOKIE_AGAIN) {
return ctx->state;
}
/* Check for packet processing errors first.
* Note - we *MUST* check if it has at least a QUESTION,
* otherwise it would crash on accessing QNAME. */
/* TODO: some of these erros are probably unreachable
* thanks to getting caught earlier, in particular in worker_submit() */
if (pkt->parsed <= KNOT_WIRE_HEADER_SIZE) {
if (pkt->parsed == KNOT_WIRE_HEADER_SIZE && knot_wire_get_rcode(pkt->wire) == KNOT_RCODE_FORMERR) {
/* This is a special case where we get valid header with FORMERR and nothing else.
* This happens on some authoritatives which don't support EDNS and don't
* bother copying the SECTION QUESTION. */
query->server_selection.error(query, req->upstream.transport, KR_SELECTION_FORMERR);
return KR_STATE_FAIL;
}
VERBOSE_MSG("<= malformed response (parsed %d)\n", (int)pkt->parsed);
query->server_selection.error(query, req->upstream.transport, KR_SELECTION_MALFORMED);
return KR_STATE_FAIL;
} else if (!is_paired_to_query(pkt, query)) {
WITH_VERBOSE(query) {
const char *ns_str =
req->upstream.transport ? kr_straddr(&req->upstream.transport->address.ip) : "(internal)";
VERBOSE_MSG("<= ignoring mismatching response from %s\n",
ns_str ? ns_str : "(kr_straddr failed)");
}
query->server_selection.error(query, req->upstream.transport, KR_SELECTION_MISMATCHED);
return KR_STATE_FAIL;
} else if (knot_wire_get_tc(pkt->wire)) {
VERBOSE_MSG("<= truncated response, failover to TCP\n");
if (query) {
/* Fail if already on TCP. */
if (req->upstream.transport->protocol != KR_TRANSPORT_UDP) {
VERBOSE_MSG("<= TC=1 with TCP, bailing out\n");
query->server_selection.error(query, req->upstream.transport, KR_SELECTION_TRUNCATED);
return KR_STATE_FAIL;
}
query->server_selection.error(query, req->upstream.transport, KR_SELECTION_TRUNCATED);
}
return KR_STATE_CONSUME;
}
/* If exiting above here, there's no sense to put it into packet cache.
* Having "extra bytes" at the end of DNS message is considered SANE here.
* The most important part is to check for spoofing: is_paired_to_query() */
query->flags.PKT_IS_SANE = true;
const knot_lookup_t *rcode = // just for logging but cheaper than a condition
knot_lookup_by_id(knot_rcode_names, knot_wire_get_rcode(pkt->wire));
// We can't return directly from the switch because we have to give feedback to server selection first
int ret = 0;
int selection_error = KR_SELECTION_OK;
/* Check response code. */
switch(knot_wire_get_rcode(pkt->wire)) {
case KNOT_RCODE_NOERROR:
case KNOT_RCODE_NXDOMAIN:
break; /* OK */
case KNOT_RCODE_YXDOMAIN: /* Basically a successful answer; name just doesn't fit. */
if (!kr_request_ensure_answer(req)) {
ret = req->state;
}
knot_wire_set_rcode(req->answer->wire, KNOT_RCODE_YXDOMAIN);
break;
case KNOT_RCODE_REFUSED:
if (query->flags.STUB) {
/* just pass answer through if in stub mode */
break;
}
ret = KR_STATE_FAIL;
selection_error = KR_SELECTION_REFUSED;
break;
case KNOT_RCODE_SERVFAIL:
if (query->flags.STUB) {
/* just pass answer through if in stub mode */
break;
}
ret = KR_STATE_FAIL;
selection_error = KR_SELECTION_SERVFAIL;
break;
case KNOT_RCODE_FORMERR:
ret = KR_STATE_FAIL;
if (knot_pkt_has_edns(pkt)) {
selection_error = KR_SELECTION_FORMERR_EDNS;
} else {
selection_error = KR_SELECTION_FORMERR;
}
break;
case KNOT_RCODE_NOTIMPL:
ret = KR_STATE_FAIL;
selection_error = KR_SELECTION_NOTIMPL;
break;
default:
ret = KR_STATE_FAIL;
selection_error = KR_SELECTION_OTHER_RCODE;
break;
}
/* Check for "extra bytes" is deferred, so that RCODE-based failures take priority. */
if (ret != KR_STATE_FAIL && pkt->parsed < pkt->size) {
VERBOSE_MSG("<= malformed response with %zu extra bytes\n",
pkt->size - pkt->parsed);
ret = KR_STATE_FAIL;
if (selection_error == KR_SELECTION_OK)
selection_error = KR_SELECTION_MALFORMED;
}
if (query->server_selection.initialized) {
query->server_selection.error(query, req->upstream.transport, selection_error);
}
if (ret) {
VERBOSE_MSG("<= rcode: %s\n", rcode ? rcode->name : "??");
return ret;
}
int state;
/* Forwarding/stub mode is special. */
if (query->flags.STUB) {
state = process_stub(pkt, req);
goto rrarray_finalize;
}
/* Resolve authority to see if it's referral or authoritative. */
state = process_authority(pkt, req);
switch(state) {
case KR_STATE_CONSUME: /* Not referral, process answer. */
VERBOSE_MSG("<= rcode: %s\n", rcode ? rcode->name : "??");
state = process_answer(pkt, req);
break;
case KR_STATE_DONE: /* Referral */
state = process_referral_answer(pkt,req);
if (satisfied_by_additional(query)) { /* This is a little hacky.
* We found sufficient information in ADDITIONAL section
* and it was selected for caching in this CONSUME round.
* To make iterator accept the record in a simple way,
* we trigger another cache *reading* attempt
* for the subsequent PRODUCE round.
*/
kr_assert(query->flags.NONAUTH);
query->flags.CACHE_TRIED = false;
VERBOSE_MSG("<= referral response, but cache should stop us short now\n");
} else {
VERBOSE_MSG("<= referral response, follow\n");
}
break;
default:
break;
}
rrarray_finalize:
/* Finish construction of libknot-format RRsets.
* We do this even if dropping the answer, though it's probably useless. */
(void)0;
const struct kr_cache *cache = &req->ctx->cache;
ranked_rr_array_t *selected[] = kr_request_selected(req);
for (knot_section_t i = KNOT_ANSWER; i <= KNOT_ADDITIONAL; ++i) {
ret = kr_ranked_rrarray_finalize(selected[i], query->uid, &req->pool);
if (unlikely(ret))
return KR_STATE_FAIL;
if (!query->flags.CACHED)
bound_ttls(selected[i], query->uid, cache->ttl_min, cache->ttl_max);
}
return state;
}
/** Module implementation. */
int iterate_init(struct kr_module *self)
{
static const kr_layer_api_t layer = {
.begin = &begin,
.reset = &reset,
.consume = &resolve,
.produce = &prepare_query
};
self->layer = &layer;
return kr_ok();
}
KR_MODULE_EXPORT(iterate) /* useless for builtin module, but let's be consistent */
#undef VERBOSE_MSG
|