diff options
| -rw-r--r-- | src/resolve/resolved-dns-dnssec.c | 107 |
1 files changed, 97 insertions, 10 deletions
diff --git a/src/resolve/resolved-dns-dnssec.c b/src/resolve/resolved-dns-dnssec.c index 46dcae68ba..2ede907e25 100644 --- a/src/resolve/resolved-dns-dnssec.c +++ b/src/resolve/resolved-dns-dnssec.c @@ -1220,14 +1220,23 @@ static int nsec3_hashed_domain(const DnsResourceRecord *nsec3, const char *domai return hashed_size; } -/* See RFC 5155, Section 8 */ +/* See RFC 5155, Section 8 + * First try to find a NSEC3 record that matches our query precisely, if that fails, find the closest + * enclosure. Secondly, find a proof that there is no closer enclosure and either a proof that there + * is no wildcard domain as a direct descendant of the closest enclosure, or find an NSEC3 record that + * matches the wildcard domain. + * + * Based on this we can prove either the existence of the record in @key, or NXDOMAIN or NODATA, or + * that there is no proof either way. The latter is the case if a the proof of non-existence of a given + * name uses an NSEC3 record with the opt-out bit set. Lastly, if we are given insufficient NSEC3 records + * to conclude anything we indicate this by returning NO_RR. */ static int dnssec_test_nsec3(DnsAnswer *answer, DnsResourceKey *key, DnssecNsecResult *result, bool *authenticated) { - _cleanup_free_ char *next_closer_domain = NULL; + _cleanup_free_ char *next_closer_domain = NULL, *wildcard = NULL, *wildcard_domain = NULL; const char *zone, *p, *pp = NULL; - DnsResourceRecord *rr, *enclosure_rr, *suffix_rr; + DnsResourceRecord *rr, *enclosure_rr, *suffix_rr, *wildcard_rr = NULL; DnsAnswerFlags flags; int hashed_size, r; - bool a; + bool a, no_closer = false, no_wildcard = false, optout = false; assert(key); assert(result); @@ -1345,6 +1354,18 @@ found_closest_encloser: return 0; } + /* Prove that there is no next closer and whether or not there is a wildcard domain. */ + + wildcard = strappend("*.", p); + if (!wildcard) + return -ENOMEM; + + r = nsec3_hashed_domain(enclosure_rr, wildcard, zone, &wildcard_domain); + if (r < 0) + return r; + if (r != hashed_size) + return -EBADMSG; + r = nsec3_hashed_domain(enclosure_rr, pp, zone, &next_closer_domain); if (r < 0) return r; @@ -1373,16 +1394,82 @@ found_closest_encloser: return r; if (r > 0) { if (rr->nsec3.flags & 1) - *result = DNSSEC_NSEC_OPTOUT; - else - *result = DNSSEC_NSEC_NXDOMAIN; + optout = true; - *authenticated = a && (flags & DNS_ANSWER_AUTHENTICATED); - return 1; + a = a && (flags & DNS_ANSWER_AUTHENTICATED); + + no_closer = true; + } + + r = dns_name_equal(DNS_RESOURCE_KEY_NAME(rr->key), wildcard_domain); + if (r < 0) + return r; + if (r > 0) { + a = a && (flags & DNS_ANSWER_AUTHENTICATED); + + wildcard_rr = rr; + } + + r = dns_name_between(DNS_RESOURCE_KEY_NAME(rr->key), wildcard_domain, next_hashed_domain); + if (r < 0) + return r; + if (r > 0) { + if (rr->nsec3.flags & 1) + /* This only makes sense if we have a wildcard delegation, which is + * very unlikely, see RFC 4592, Section 4.2, but we cannot rely on + * this not happening, so hence cannot simply conclude NXDOMAIN as + * we would wish */ + optout = true; + + a = a && (flags & DNS_ANSWER_AUTHENTICATED); + + no_wildcard = true; } } - *result = DNSSEC_NSEC_NO_RR; + if (wildcard_rr && no_wildcard) + return -EBADMSG; + + if (!no_closer) { + *result = DNSSEC_NSEC_NO_RR; + + return 0; + } + + if (wildcard_rr) { + /* A wildcard exists that matches our query. */ + if (optout) + /* This is not specified in any RFC to the best of my knowledge, but + * if the next closer enclosure is covered by an opt-out NSEC3 RR + * it means that we cannot prove that the source of synthesis is + * correct, as there may be a closer match. */ + *result = DNSSEC_NSEC_OPTOUT; + else if (bitmap_isset(wildcard_rr->nsec3.types, key->type)) + *result = DNSSEC_NSEC_FOUND; + else if (bitmap_isset(wildcard_rr->nsec3.types, DNS_TYPE_CNAME)) + *result = DNSSEC_NSEC_CNAME; + else + *result = DNSSEC_NSEC_NODATA; + } else { + if (optout) + /* The RFC only specifies that we have to care for optout for NODATA for + * DS records. However, children of an insecure opt-out delegation should + * also be considered opt-out, rather than verified NXDOMAIN. + * Note that we do not require a proof of wildcard non-existence if the + * next closer domain is covered by an opt-out, as that would not provide + * any additional information. */ + *result = DNSSEC_NSEC_OPTOUT; + else if (no_wildcard) + *result = DNSSEC_NSEC_NXDOMAIN; + else { + *result = DNSSEC_NSEC_NO_RR; + + return 0; + } + } + + *authenticated = a; + return 0; } |