Date: Wed, 12 Nov 2014 12:33:08 -0500 (EST) From: cve-assign@...re.org To: krahmer@...e.de Cc: cve-assign@...re.org, oss-security@...ts.openwall.com Subject: Re: CVE-request: systemd-resolved DNS cache poisoning -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 > systemd-resolved contains a caching resolver ... does not implement > any of the hardening recommendations of rfc5452. We have several comments about this. First, systemd-resolved is apparently advertised as a stub resolver (e.g., see the http://www.freedesktop.org/software/systemd/man/systemd-resolved.service.html man page). RFC 5452 is about requirements for a resolver (defined in section 2.1) and -- at least in our interpretation -- specifically does not set any requirements for a stub resolver. Documentation for some other stub resolvers makes explicit statements about security expectations, e.g., http://www.gnu.org/software/adns/ http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=adns.git;a=blob;f=INSTALL adns is a `stub resolver' ... no defence against bad nameservers or fake packets which appear to come from your real nameservers. You MUST use a firewall or other means to block packets which appear to come from these nameservers, but which were actually sent by other, untrusted, entities. See also CVE-2008-4100. The systemd-resolved documentation is apparently less explicit. Is your message attempting to assert that EVERY implementation of a stub resolver must satisfy RFC 5452 requirements, in order to account for the possibility that the configured recursive name servers have security problems, and the possibility that an attacker can communicate directly with the stub resolver? Or does your message mean that there's something unusual about the environments in which systemd-resolved is deployed, such that one or more RFC 5452 requirements become applicable? We're not aware of any standard reference that describes required security properties of a stub resolver. There isn't much in RFC 1123 188.8.131.52(B). RFC 4033 mentions the concept of a security-oblivious stub resolver, suggesting that this is acceptable. Is RFC 5452 section 3 item 3 "The response comes from the same network address to which the question was sent" the single implied requirement of a stub resolver? In other words, a minimally acceptable stub resolver can blindly trust its configured recursive name servers by IP address, but still must discard responses (or document mandatory firewalling to discard responses) from any other source IP addresses? Note that this question is only about a requirement, not about what types of security hardening would be ideally present. It's conceivable that upstream may decide to announce that one or more behaviors were vulnerabilities. CVE assignments may be possible then. This especially applies to the case of implementation errors. We don't currently see a way to do any CVE assignments until after an announcement from upstream. We typically would not have an overarching CVE such as "does not follow RFC 5452 recommendations" even if the product were advertised as a full-service resolver. - -- CVE assignment team, MITRE CVE Numbering Authority M/S M300 202 Burlington Road, Bedford, MA 01730 USA [ PGP key available through http://cve.mitre.org/cve/request_id.html ] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.14 (SunOS) iQEcBAEBAgAGBQJUY5kdAAoJEKllVAevmvmsWOUH/3GcpvpJ1vHFoiwqYzNGj1O6 fYJWbv9hvaDvgpQLBB+Nertc3i5p/uTGXQqBZWUZ5EdZsjUM6Dj0DdIYWAGK59bQ Xut25F3/xL3JPxlshQW4gY3Yc3FIVw+w3C6+dWZqFAQZ/kFB/IMhBSpb3t0OIXZk 3zW1gT6HtnhZ368NaXnNN3Bdtc/Hnf4RAVnzYjf8BnyqHuMQPGH7OnxzR2eId1Bi Y2EYSvtdvDU5CDkx+ataME1spuJMLOjMHjeeFUe+VNuiqa6/DIcmhXMFgM8CnYb3 kttu7Xqydf6pi9hGDsbrVIUJiNiChyoxTeE1I3Grp+sd3CiDGhlosZ5DVpLBDS4= =o1Tu -----END PGP SIGNATURE-----
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