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67d0ce8843
It has been demonstrated that tolerating an unbounded number of dnssec signature validations is a bad idea. It is easy for a maliciously crafted DNS reply to contain as many keytag collisions as desired, causing us to iterate every dnskey and signature combination in vain. The solution is to impose a maximum number of validations we will tolerate. While collisions are not hard to craft, I still expect they are unlikely in the wild so it should be safe to pick fairly small values. Here two limits are imposed: one on the maximum number of invalid signatures encountered per rrset, and another on the total number of validations performed per transaction.
90 lines
3.3 KiB
C
90 lines
3.3 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#pragma once
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typedef enum DnssecResult DnssecResult;
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typedef enum DnssecVerdict DnssecVerdict;
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#include "dns-domain.h"
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#include "resolved-dns-answer.h"
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#include "resolved-dns-rr.h"
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enum DnssecResult {
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/* These six are returned by dnssec_verify_rrset() */
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DNSSEC_VALIDATED,
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DNSSEC_VALIDATED_WILDCARD, /* Validated via a wildcard RRSIG, further NSEC/NSEC3 checks necessary */
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DNSSEC_INVALID,
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DNSSEC_SIGNATURE_EXPIRED,
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DNSSEC_UNSUPPORTED_ALGORITHM,
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DNSSEC_TOO_MANY_VALIDATIONS,
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/* These two are added by dnssec_verify_rrset_search() */
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DNSSEC_NO_SIGNATURE,
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DNSSEC_MISSING_KEY,
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/* These five are added by the DnsTransaction logic */
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DNSSEC_UNSIGNED,
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DNSSEC_FAILED_AUXILIARY,
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DNSSEC_NSEC_MISMATCH,
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DNSSEC_INCOMPATIBLE_SERVER,
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DNSSEC_UPSTREAM_FAILURE,
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_DNSSEC_RESULT_MAX,
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_DNSSEC_RESULT_INVALID = -EINVAL,
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};
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enum DnssecVerdict {
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DNSSEC_SECURE,
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DNSSEC_INSECURE,
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DNSSEC_BOGUS,
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DNSSEC_INDETERMINATE,
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_DNSSEC_VERDICT_MAX,
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_DNSSEC_VERDICT_INVALID = -EINVAL,
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};
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#define DNSSEC_CANONICAL_HOSTNAME_MAX (DNS_HOSTNAME_MAX + 2)
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/* The longest digest we'll ever generate, of all digest algorithms we support */
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#define DNSSEC_HASH_SIZE_MAX (MAX(20, 32))
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/* The most invalid signatures we will tolerate for a single rrset */
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#define DNSSEC_INVALID_MAX 5
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/* The total number of signature validations we will tolerate for a single transaction */
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#define DNSSEC_VALIDATION_MAX 64
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int dnssec_rrsig_match_dnskey(DnsResourceRecord *rrsig, DnsResourceRecord *dnskey, bool revoked_ok);
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int dnssec_key_match_rrsig(const DnsResourceKey *key, DnsResourceRecord *rrsig);
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int dnssec_verify_rrset(DnsAnswer *answer, const DnsResourceKey *key, DnsResourceRecord *rrsig, DnsResourceRecord *dnskey, usec_t realtime, DnssecResult *result);
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int dnssec_verify_rrset_search(DnsAnswer *answer, const DnsResourceKey *key, DnsAnswer *validated_dnskeys, usec_t realtime, DnssecResult *result, DnsResourceRecord **rrsig);
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int dnssec_verify_dnskey_by_ds(DnsResourceRecord *dnskey, DnsResourceRecord *ds, bool mask_revoke);
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int dnssec_verify_dnskey_by_ds_search(DnsResourceRecord *dnskey, DnsAnswer *validated_ds);
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int dnssec_has_rrsig(DnsAnswer *a, const DnsResourceKey *key);
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uint16_t dnssec_keytag(DnsResourceRecord *dnskey, bool mask_revoke);
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int dnssec_nsec3_hash(DnsResourceRecord *nsec3, const char *name, void *ret);
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typedef enum DnssecNsecResult {
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DNSSEC_NSEC_NO_RR, /* No suitable NSEC/NSEC3 RR found */
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DNSSEC_NSEC_CNAME, /* Didn't find what was asked for, but did find CNAME */
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DNSSEC_NSEC_UNSUPPORTED_ALGORITHM,
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DNSSEC_NSEC_NXDOMAIN,
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DNSSEC_NSEC_NODATA,
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DNSSEC_NSEC_FOUND,
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DNSSEC_NSEC_OPTOUT,
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} DnssecNsecResult;
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int dnssec_nsec_test(DnsAnswer *answer, DnsResourceKey *key, DnssecNsecResult *result, bool *authenticated, uint32_t *ttl);
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int dnssec_test_positive_wildcard(DnsAnswer *a, const char *name, const char *source, const char *zone, bool *authenticated);
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const char* dnssec_result_to_string(DnssecResult m) _const_;
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DnssecResult dnssec_result_from_string(const char *s) _pure_;
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const char* dnssec_verdict_to_string(DnssecVerdict m) _const_;
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DnssecVerdict dnssec_verdict_from_string(const char *s) _pure_;
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