diff options
Diffstat (limited to 'src/resolve')
| -rw-r--r-- | src/resolve/resolved-dns-dnssec.c | 21 | ||||
| -rw-r--r-- | src/resolve/resolved-dns-dnssec.h | 9 | ||||
| -rw-r--r-- | src/resolve/resolved-dns-transaction.c | 19 |
3 files changed, 41 insertions, 8 deletions
diff --git a/src/resolve/resolved-dns-dnssec.c b/src/resolve/resolved-dns-dnssec.c index f63cd9b..71a915f 100644 --- a/src/resolve/resolved-dns-dnssec.c +++ b/src/resolve/resolved-dns-dnssec.c @@ -27,8 +27,9 @@ DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(EC_KEY*, EC_KEY_free, NULL); /* Permit a maximum clock skew of 1h 10min. This should be enough to deal with DST confusion */ #define SKEW_MAX (1*USEC_PER_HOUR + 10*USEC_PER_MINUTE) -/* Maximum number of NSEC3 iterations we'll do. RFC5155 says 2500 shall be the maximum useful value */ -#define NSEC3_ITERATIONS_MAX 2500 +/* Maximum number of NSEC3 iterations we'll do. RFC5155 says 2500 shall be the maximum useful value, but + * RFC9276 ยง 3.2 says that we should reduce the acceptable iteration count */ +#define NSEC3_ITERATIONS_MAX 100 /* * The DNSSEC Chain of trust: @@ -1176,6 +1177,7 @@ int dnssec_verify_rrset_search( DnsResourceRecord **ret_rrsig) { bool found_rrsig = false, found_invalid = false, found_expired_rrsig = false, found_unsupported_algorithm = false; + unsigned nvalidations = 0; DnsResourceRecord *rrsig; int r; @@ -1221,6 +1223,14 @@ int dnssec_verify_rrset_search( if (realtime == USEC_INFINITY) realtime = now(CLOCK_REALTIME); + /* Have we seen an unreasonable number of invalid signaures? */ + if (nvalidations > DNSSEC_INVALID_MAX) { + if (ret_rrsig) + *ret_rrsig = NULL; + *result = DNSSEC_TOO_MANY_VALIDATIONS; + return (int) nvalidations; + } + /* Yay, we found a matching RRSIG with a matching * DNSKEY, awesome. Now let's verify all entries of * the RRSet against the RRSIG and DNSKEY @@ -1230,6 +1240,8 @@ int dnssec_verify_rrset_search( if (r < 0) return r; + nvalidations++; + switch (one_result) { case DNSSEC_VALIDATED: @@ -1240,7 +1252,7 @@ int dnssec_verify_rrset_search( *ret_rrsig = rrsig; *result = one_result; - return 0; + return (int) nvalidations; case DNSSEC_INVALID: /* If the signature is invalid, let's try another @@ -1287,7 +1299,7 @@ int dnssec_verify_rrset_search( if (ret_rrsig) *ret_rrsig = NULL; - return 0; + return (int) nvalidations; } int dnssec_has_rrsig(DnsAnswer *a, const DnsResourceKey *key) { @@ -2571,6 +2583,7 @@ static const char* const dnssec_result_table[_DNSSEC_RESULT_MAX] = { [DNSSEC_FAILED_AUXILIARY] = "failed-auxiliary", [DNSSEC_NSEC_MISMATCH] = "nsec-mismatch", [DNSSEC_INCOMPATIBLE_SERVER] = "incompatible-server", + [DNSSEC_TOO_MANY_VALIDATIONS] = "too-many-validations", }; DEFINE_STRING_TABLE_LOOKUP(dnssec_result, DnssecResult); diff --git a/src/resolve/resolved-dns-dnssec.h b/src/resolve/resolved-dns-dnssec.h index 954bb3e..29b9013 100644 --- a/src/resolve/resolved-dns-dnssec.h +++ b/src/resolve/resolved-dns-dnssec.h @@ -9,12 +9,13 @@ typedef enum DnssecVerdict DnssecVerdict; #include "resolved-dns-rr.h" enum DnssecResult { - /* These five are returned by dnssec_verify_rrset() */ + /* These six are returned by dnssec_verify_rrset() */ DNSSEC_VALIDATED, DNSSEC_VALIDATED_WILDCARD, /* Validated via a wildcard RRSIG, further NSEC/NSEC3 checks necessary */ DNSSEC_INVALID, DNSSEC_SIGNATURE_EXPIRED, DNSSEC_UNSUPPORTED_ALGORITHM, + DNSSEC_TOO_MANY_VALIDATIONS, /* These two are added by dnssec_verify_rrset_search() */ DNSSEC_NO_SIGNATURE, @@ -45,6 +46,12 @@ enum DnssecVerdict { /* The longest digest we'll ever generate, of all digest algorithms we support */ #define DNSSEC_HASH_SIZE_MAX (MAX(20, 32)) +/* The most invalid signatures we will tolerate for a single rrset */ +#define DNSSEC_INVALID_MAX 5 + +/* The total number of signature validations we will tolerate for a single transaction */ +#define DNSSEC_VALIDATION_MAX 64 + int dnssec_rrsig_match_dnskey(DnsResourceRecord *rrsig, DnsResourceRecord *dnskey, bool revoked_ok); int dnssec_key_match_rrsig(const DnsResourceKey *key, DnsResourceRecord *rrsig); diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c index 1850d45..21326fa 100644 --- a/src/resolve/resolved-dns-transaction.c +++ b/src/resolve/resolved-dns-transaction.c @@ -3172,11 +3172,14 @@ static int dnssec_validate_records( DnsTransaction *t, Phase phase, bool *have_nsec, + unsigned *nvalidations, DnsAnswer **validated) { DnsResourceRecord *rr; int r; + assert(nvalidations); + /* Returns negative on error, 0 if validation failed, 1 to restart validation, 2 when finished. */ DNS_ANSWER_FOREACH(rr, t->answer) { @@ -3218,6 +3221,7 @@ static int dnssec_validate_records( &rrsig); if (r < 0) return r; + *nvalidations += r; log_debug("Looking at %s: %s", strna(dns_resource_record_to_string(rr)), dnssec_result_to_string(result)); @@ -3415,7 +3419,8 @@ static int dnssec_validate_records( DNSSEC_SIGNATURE_EXPIRED, DNSSEC_NO_SIGNATURE)) manager_dnssec_verdict(t->scope->manager, DNSSEC_BOGUS, rr->key); - else /* DNSSEC_MISSING_KEY or DNSSEC_UNSUPPORTED_ALGORITHM */ + else /* DNSSEC_MISSING_KEY, DNSSEC_UNSUPPORTED_ALGORITHM, + or DNSSEC_TOO_MANY_VALIDATIONS */ manager_dnssec_verdict(t->scope->manager, DNSSEC_INDETERMINATE, rr->key); /* This is a primary response to our question, and it failed validation. @@ -3508,13 +3513,21 @@ int dns_transaction_validate_dnssec(DnsTransaction *t) { return r; phase = DNSSEC_PHASE_DNSKEY; - for (;;) { + for (unsigned nvalidations = 0;;) { bool have_nsec = false; - r = dnssec_validate_records(t, phase, &have_nsec, &validated); + r = dnssec_validate_records(t, phase, &have_nsec, &nvalidations, &validated); if (r <= 0) return r; + if (nvalidations > DNSSEC_VALIDATION_MAX) { + /* This reply requires an onerous number of signature validations to verify. Let's + * not waste our time trying, as this shouldn't happen for well-behaved domains + * anyway. */ + t->answer_dnssec_result = DNSSEC_TOO_MANY_VALIDATIONS; + return 0; + } + /* Try again as long as we managed to achieve something */ if (r == 1) continue; |