diff options
Diffstat (limited to '')
| -rw-r--r-- | debian/patches/CVE-2022-40188.patch | 160 |
1 files changed, 160 insertions, 0 deletions
diff --git a/debian/patches/CVE-2022-40188.patch b/debian/patches/CVE-2022-40188.patch new file mode 100644 index 0000000..29edd74 --- /dev/null +++ b/debian/patches/CVE-2022-40188.patch @@ -0,0 +1,160 @@ +From: Chris Lamb <lamby@debian.org> +Date: Thu, 6 Oct 2022 14:12:26 -0700 +Subject: [PATCH] lib/zonecut + iterator: limit large NS sets + +rom f6577a20e493c7fbdac124d7544bf1846b084185 Mon Sep 17 00:00:00 2001 + +rom f6577a20e493c7fbdac124d7544bf1846b084185 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Vladim=C3=ADr=20=C4=8Cun=C3=A1t?= <vladimir.cunat@nic.cz> +Date: Wed, 17 Aug 2022 16:34:06 +0200 +Subject: [PATCH] lib/zonecut + iterator: limit large NS sets + +It's a mitigation for CVE-2022-40188 and similar DoS attempts. +It's using really trivial approaches, at least for now. +--- + lib/layer/iterate.c | 15 +++++++++++++++ + lib/zonecut.c | 33 +++++++++++++++++++++++++++++++-- + lib/zonecut.h | 2 ++ + 3 files changed, 48 insertions(+), 2 deletions(-) + +diff --git a/lib/layer/iterate.c b/lib/layer/iterate.c +index cf57cc5..f7dd630 100644 +--- a/lib/layer/iterate.c ++++ b/lib/layer/iterate.c +@@ -193,6 +193,8 @@ static int update_nsaddr(const knot_rrset_t *rr, struct kr_query *query, int *gl + 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) +@@ -227,6 +229,10 @@ static void fetch_glue(knot_pkt_t *pkt, const knot_dname_t *ns, bool in_bailiwic + 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; + } + } + } +@@ -427,6 +433,7 @@ static int process_authority(knot_pkt_t *pkt, struct kr_request *req) + 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); +@@ -438,6 +445,11 @@ static int process_authority(knot_pkt_t *pkt, struct kr_request *req) + 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, +@@ -465,6 +477,9 @@ static int process_authority(knot_pkt_t *pkt, struct kr_request *req) + 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 && +diff --git a/lib/zonecut.c b/lib/zonecut.c +index 5e54d97..cc25062 100644 +--- a/lib/zonecut.c ++++ b/lib/zonecut.c +@@ -299,6 +299,7 @@ int kr_zonecut_set_sbelt(struct kr_context *ctx, struct kr_zonecut *cut) + + /** Fetch address for zone cut. Any rank is accepted (i.e. glue as well). */ + static addrset_info_t fetch_addr(pack_t *addrs, const knot_dname_t *ns, uint16_t rrtype, ++ int *addr_budget, + knot_mm_t *mm_pool, const struct kr_query *qry) + // LATER(optim.): excessive data copying + { +@@ -332,6 +333,12 @@ static addrset_info_t fetch_addr(pack_t *addrs, const knot_dname_t *ns, uint16_t + return AI_UNKNOWN; + } + ++ *addr_budget -= cached_rr.rrs.count - 1; ++ if (*addr_budget < 0) { ++ cached_rr.rrs.count += *addr_budget; ++ *addr_budget = 0; ++ } ++ + /* Reserve memory in *addrs. Implementation detail: + * pack_t cares for lengths, so we don't store those in the data. */ + const size_t pack_extra_size = knot_rdataset_size(&cached_rr.rrs) +@@ -406,6 +413,20 @@ static int fetch_ns(struct kr_context *ctx, struct kr_zonecut *cut, + return ret; + } + ++ /* Consider at most 13 first NSs (like root). It's a trivial approach ++ * to limit our resources when choosing NSs. Otherwise DoS might be viable. ++ * We're not aware of any reasonable use case for having many NSs. */ ++ if (ns_rds.count > 13) { ++ auto_free char *name_txt = kr_dname_text(name); ++ VERBOSE_MSG(qry, "NS %s too large, reducing from %d names\n", ++ name_txt, (int)ns_rds.count); ++ ns_rds.count = 13; ++ } ++ /* Also trivially limit the total address count: ++ * first A and first AAAA are for free per NS, ++ * but the rest get a shared small limit and get skipped if exhausted. */ ++ int addr_budget = 8; ++ + /* Insert name servers for this zone cut, addresses will be looked up + * on-demand (either from cache or iteratively) */ + bool all_bad = true; /**< All NSs (seen so far) are in a bad state. */ +@@ -431,10 +452,10 @@ static int fetch_ns(struct kr_context *ctx, struct kr_zonecut *cut, + unsigned reputation = (cached) ? *cached : 0; + infos[0] = (reputation & KR_NS_NOIP4) || qry->flags.NO_IPV4 + ? AI_REPUT +- : fetch_addr(*pack, ns_name, KNOT_RRTYPE_A, cut->pool, qry); ++ : fetch_addr(*pack, ns_name, KNOT_RRTYPE_A, &addr_budget, cut->pool, qry); + infos[1] = (reputation & KR_NS_NOIP6) || qry->flags.NO_IPV6 + ? AI_REPUT +- : fetch_addr(*pack, ns_name, KNOT_RRTYPE_AAAA, cut->pool, qry); ++ : fetch_addr(*pack, ns_name, KNOT_RRTYPE_AAAA, &addr_budget, cut->pool, qry); + + #if 0 /* rather unlikely to be useful unless changing some zcut code */ + WITH_VERBOSE(qry) { +@@ -480,6 +501,14 @@ static int fetch_ns(struct kr_context *ctx, struct kr_zonecut *cut, + VERBOSE_MSG(qry, "cut %s: all NSs bad, count = %d\n", + name_txt, (int)ns_rds.count); + } } ++ ++ assert(addr_budget >= 0); ++ if (addr_budget <= 0) { ++ auto_free char *name_txt = kr_dname_text(name); ++ VERBOSE_MSG(qry, "NS %s have too many addresses together, reduced\n", ++ name_txt); ++ } ++ + knot_rdataset_clear(&ns_rds, cut->pool); + return all_bad ? ELOOP : kr_ok(); + } +diff --git a/lib/zonecut.h b/lib/zonecut.h +index 2808c66..70dd4df 100644 +--- a/lib/zonecut.h ++++ b/lib/zonecut.h +@@ -151,6 +151,8 @@ int kr_zonecut_set_sbelt(struct kr_context *ctx, struct kr_zonecut *cut); + /** + * Populate zone cut address set from cache. + * ++ * The size is limited to avoid possibility of doing too much CPU work. ++ * + * @param ctx resolution context (to fetch data from LRU caches) + * @param cut zone cut to be populated + * @param name QNAME to start finding zone cut for |