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Diffstat (limited to 'lib/layer/iterate.c')
| -rw-r--r-- | lib/layer/iterate.c | 1254 |
1 files changed, 1254 insertions, 0 deletions
diff --git a/lib/layer/iterate.c b/lib/layer/iterate.c new file mode 100644 index 0000000..dfb7c87 --- /dev/null +++ b/lib/layer/iterate.c @@ -0,0 +1,1254 @@ +/* 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; + } + } +} + +static void ede_passthru(const knot_pkt_t *pkt, struct kr_request *req) +{ + const uint8_t *ede_raw = pkt->edns_opts ? + pkt->edns_opts->ptr[KNOT_EDNS_OPTION_EDE] : NULL; + if (!ede_raw) return; + kr_require(ede_raw[0] * 256 + ede_raw[1] == KNOT_EDNS_OPTION_EDE); + uint16_t ede_len = ede_raw[2] * 256 + ede_raw[3]; + if (ede_len < 2) return; + uint16_t ede_code = ede_raw[4] * 256 + ede_raw[5]; + if (ede_code >= KNOT_EDNS_EDE_INDETERMINATE // long range of DNSSEC codes + && ede_code <= KNOT_EDNS_EDE_NSEC_MISS) { + kr_request_set_extended_error(req, ede_code, "V5T7: forwarded EDE code"); + } +} + +/** 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; + if (query->flags.FORWARD) { + /* additionally pass some of the EDE codes through */ + ede_passthru(pkt, req); + } + 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 |