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Diffstat (limited to '')
| -rw-r--r-- | lib/dnssec/nsec3.h | 116 |
1 files changed, 116 insertions, 0 deletions
diff --git a/lib/dnssec/nsec3.h b/lib/dnssec/nsec3.h new file mode 100644 index 0000000..a28d3c7 --- /dev/null +++ b/lib/dnssec/nsec3.h @@ -0,0 +1,116 @@ +/* Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz> + * SPDX-License-Identifier: GPL-3.0-or-later + */ + +#pragma once + +#include <libknot/packet/pkt.h> +#include <libknot/rrtype/nsec3.h> +#include <libdnssec/nsec.h> + + +static inline unsigned int kr_nsec3_price(unsigned int iterations, unsigned int salt_len) +{ + // SHA1 works on 64-byte chunks. + // On iterating we hash the salt + 20 bytes of the previous hash. + int chunks_per_iter = (20 + salt_len - 1) / 64 + 1; + return (iterations + 1) * chunks_per_iter; +} + +/** High numbers in NSEC3 iterations don't really help security + * + * ...so we avoid doing all the work. The limit is a current compromise; + * answers using NSEC3 over kr_nsec3_limited* get downgraded to insecure status. + * + https://datatracker.ietf.org/doc/html/rfc9276#name-recommendation-for-validati + */ +static inline bool kr_nsec3_limited(unsigned int iterations, unsigned int salt_len) +{ + const int MAX_ITERATIONS = 50; // limit with short salt length + return kr_nsec3_price(iterations, salt_len) > MAX_ITERATIONS + 1; +} +static inline bool kr_nsec3_limited_rdata(const knot_rdata_t *rd) +{ + return kr_nsec3_limited(knot_nsec3_iters(rd), knot_nsec3_salt_len(rd)); +} +static inline bool kr_nsec3_limited_params(const dnssec_nsec3_params_t *params) +{ + return kr_nsec3_limited(params->iterations, params->salt.size); +} + +/** Return limit on NSEC3 depth. The point is to avoid doing too much work on SHA1. + * + * CVE-2023-50868: NSEC3 closest encloser proof can exhaust CPU + * + * 128 is chosen so that zones with good NSEC3 parameters (giving _price() == 1) + * won't be limited in any way. Performance doesn't seem too bad with that either. + */ +static inline int kr_nsec3_max_depth(const dnssec_nsec3_params_t *params) +{ + return 128 / kr_nsec3_price(params->iterations, params->salt.size); +} + + +/** + * Name error response check (RFC5155 7.2.2). + * @note No RRSIGs are validated. + * @param pkt Packet structure to be processed. + * @param section_id Packet section to be processed. + * @param sname Name to be checked. + * @return 0 or error code. + */ +int kr_nsec3_name_error_response_check(const knot_pkt_t *pkt, knot_section_t section_id, + const knot_dname_t *sname); + +/** + * Wildcard answer response check (RFC5155 7.2.6). + * @param pkt Packet structure to be processed. + * @param section_id Packet section to be processed. + * @param sname Name to be checked. + * @param trim_to_next Number of labels to remove to obtain next closer name. + * @return 0 or error code: + * KNOT_ERANGE - NSEC3 RR that covers a wildcard + * has been found, but has opt-out flag set; + * otherwise - error. + * Too expensive NSEC3 records are skipped, so you probably get kr_error(ENOENT). + */ +int kr_nsec3_wildcard_answer_response_check(const knot_pkt_t *pkt, knot_section_t section_id, + const knot_dname_t *sname, int trim_to_next); + +/** + * Authenticated denial of existence according to RFC5155 8.5 and 8.7. + * @note No RRSIGs are validated. + * @param pkt Packet structure to be processed. + * @param section_id Packet section to be processed. + * @param sname Queried domain name. + * @param stype Queried type. + * @return 0 or error code: + * DNSSEC_NOT_FOUND - neither ds nor nsec records + * were not found. + * KNOT_ERANGE - denial of existence can't be proven + * due to opt-out, otherwise - bogus. + */ +int kr_nsec3_no_data(const knot_pkt_t *pkt, knot_section_t section_id, + const knot_dname_t *sname, uint16_t stype); + +/** + * Referral to unsigned subzone check (RFC5155 8.9). + * @note No RRSIGs are validated. + * @param pkt Packet structure to be processed. + * @return 0 or error code: + * KNOT_ERANGE - denial of existence can't be proven + * due to opt-out. + * EEXIST - ds record was found. + * EINVAL - bogus. + */ +int kr_nsec3_ref_to_unsigned(const knot_pkt_t *pkt); + +/** + * Checks whether supplied NSEC3 RR matches the supplied name and NS type. + * @param nsec3 NSEC3 RR. + * @param name Name to be checked. + * @param type Type to be checked. Only use with NS! TODO + * @return 0 or error code. + */ +int kr_nsec3_matches_name_and_type(const knot_rrset_t *nsec3, + const knot_dname_t *name, uint16_t type); |