Re: [DNSOP] DNS over DTLS (DNSoD)
On Wed, Apr 23, 2014 at 09:16:29AM -0700,
Paul Hoffman paul.hoff...@vpnc.org wrote
a message of 39 lines which said:
Sure. What were the results of your testing?
I quickly tested with .FR authoritative name servers and both NSD and
BIND seem to silently ignore the incoming request. No response is seen
coming back.
08:08:44.460710 IP (tos 0x0, ttl 64, id 8611, offset 0, flags [DF],
proto UDP (17), length 192)
192.168.1.10.48864 194.0.9.1.53: [udp sum ok] 5886 zoneRef*-|
[0q] 0/0/0 (164)
08:08:45.459519 IP (tos 0x0, ttl 64, id 8612, offset 0, flags [DF],
proto UDP (17), length 192)
192.168.1.10.48864 194.0.9.1.53: [udp sum ok] 5886 zoneRef*-|
[0q] 0/0/256 ar:
^A^@^@M-^K^@^@^@^@^@^@^@M-^KM-~M-^?SXM-*l^P^^^TM-n4^gs^OM-ylMM-S0M-9M-=M-^F_^D^V4^NM-us{^^:^@^@^@XM-@^TM-@^JM-@M-@!^@9^@8^@M-^H^@M-^GM-@^OM-@^E^@5^@M-^DM-@^RM-@^HM-@^\M-@^[^@^V^@^SM-@^MM-@^C^@^JM-@^SM-@^IM-@^_M-@^^^@3^@2^@M-^Z^@M-^Y^@E^@DM-@^NM-@^D^@/^@M-^V^@A^@^U^@^R^@^I^@^T^@^Q^@^H^@^F^@M-^?^A^@^@^I^@#^@^@^@^O^@^A^A.[|domain]
08:08:47.459513 IP (tos 0x0, ttl 64, id 8613, offset 0, flags [DF],
proto UDP (17), length 192)
192.168.1.10.48864 194.0.9.1.53: [udp sum ok] 5886 zoneRef*-|
[0q] 0/0/512 ar:
^A^@^@M-^K^@^@^@^@^@^@^@M-^KM-~M-^?SXM-*l^P^^^TM-n4^gs^OM-ylMM-S0M-9M-=M-^F_^D^V4^NM-us{^^:^@^@^@XM-@^TM-@^JM-@M-@!^@9^@8^@M-^H^@M-^GM-@^OM-@^E^@5^@M-^DM-@^RM-@^HM-@^\M-@^[^@^V^@^SM-@^MM-@^C^@^JM-@^SM-@^IM-@^_M-@^^^@3^@2^@M-^Z^@M-^Y^@E^@DM-@^NM-@^D^@/^@M-^V^@A^@^U^@^R^@^I^@^T^@^Q^@^H^@^F^@M-^?^A^@^@^I^@#^@^@^@^O^@^A^A.[|domain]
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Re: [DNSOP] DNS over DTLS (DNSoD)
-Original Message- From: Paul Vixie [mailto:p...@redbarn.org] Sent: Thursday, April 24, 2014 12:11 AM To: Dan Wing Cc: dnsop@ietf.org; dns-priv...@ietf.org; Prashanth Patil (praspati); Tirumaleswar Reddy (tireddy) Subject: Re: [DNSOP] DNS over DTLS (DNSoD) for reasons well-spoken up-thread, if we're going to add a dns transport, i'd like it to be RFC 6013 style TCP (in which session context can be compressed and retained after FIN for full-window-size restart, and which permits the query to be bundled into the SYN packet), or at a minimum, SCTP. SCTP has problems with Firewall and NAT traversal, hence WebRTC is using SCTP over DTLS over DNS (http://tools.ietf.org/html/draft-ietf-rtcweb-data-channel-08). DNSoD does not require server-side DTLS state, this is achieved by the server sending ticket to the DTLS client using the mechanism explained in RFC 5077. -Tiru DTLS does not solve any of the problems described at https://queue.acm.org/detail.cfm?id=2578510. vixie ___ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
[DNSOP] DNS over DTLS (DNSoD)
For discussion. DNS queries and responses are visible to network elements on the path between the DNS client and its server. These queries and responses can contain privacy-sensitive information which is valuable to protect. An active attacker can send bogus responses causing misdirection of the subsequent connection. To counter passive listening and active attacks, this document proposes the use of Datagram Transport Layer Security (DTLS) for DNS, to protect against passive listeners and certain active attacks. As DNS needs to remain fast, this proposal also discusses mechanisms to reduce DTLS round trips and reduce DTLS handshake size. The proposed mechanism runs over the default DNS port and can also run over an alternate port. http://tools.ietf.org/html/draft-wing-dnsop-dnsodtls -d ___ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
Re: [DNSOP] DNS over DTLS (DNSoD)
TLS seems like a poor choice for any new cryptographic transport, it is a very complicated protocol with a considerable amount of implementation complexity, computational and network costs. DTLS seems poorer still, as it is an adaptation of primitives never intended for datagram transmission. But feedback on the draft: * It's unclear how your protocol would really mitigate an active attacker sending bogus responses. Won't the attacker still be able to disrupt the DTLS session? Allowing session multiplexing by query-id likely amplifies this risk. * In DTLS, the ClientHello is in the plain - this presents opportunities for downgrade attacks and inference making. Considering the proposal advocates for hardcoding the certificate, why not just use a key from the off? * Some nameservers definitely don't just not respond when they get messages they don't understand :/ * Is the entire protocol subject to the simplest downgrade attack of all? Just cause the first server response to be dropped and regular DNS will be used? * How long should session state persist? * The network costs of certificate transmission probably pale in comparison to the computational costs of key negotiation. How should trivial key-exchange ddos attacks be prevented? * TLS Heartbeat messages do not permit asymmetric MTU discovery. On Wed, Apr 23, 2014 at 6:47 AM, Dan Wing d...@danwing.org wrote: For discussion. DNS queries and responses are visible to network elements on the path between the DNS client and its server. These queries and responses can contain privacy-sensitive information which is valuable to protect. An active attacker can send bogus responses causing misdirection of the subsequent connection. To counter passive listening and active attacks, this document proposes the use of Datagram Transport Layer Security (DTLS) for DNS, to protect against passive listeners and certain active attacks. As DNS needs to remain fast, this proposal also discusses mechanisms to reduce DTLS round trips and reduce DTLS handshake size. The proposed mechanism runs over the default DNS port and can also run over an alternate port. http://tools.ietf.org/html/draft-wing-dnsop-dnsodtls -d ___ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop -- Colm ___ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
Re: [DNSOP] DNS over DTLS (DNSoD)
On Apr 23, 2014, at 7:26 AM, Paul Hoffman paul.hoff...@vpnc.org wrote: On Apr 23, 2014, at 6:47 AM, Dan Wing d...@danwing.org wrote: For discussion. DNS queries and responses are visible to network elements on the path between the DNS client and its server. These queries and responses can contain privacy-sensitive information which is valuable to protect. An active attacker can send bogus responses causing misdirection of the subsequent connection. To counter passive listening and active attacks, this document proposes the use of Datagram Transport Layer Security (DTLS) for DNS, to protect against passive listeners and certain active attacks. As DNS needs to remain fast, this proposal also discusses mechanisms to reduce DTLS round trips and reduce DTLS handshake size. The proposed mechanism runs over the default DNS port and can also run over an alternate port. http://tools.ietf.org/html/draft-wing-dnsop-dnsodtls This proposes to run a binary protocol (DTLS) over port 53. It says A DNS client or server that does not implement this specification will not respond to the incoming DTLS packets because they don't parse as DNS packets (the DNS Opcode would be 15, which is undefined). Has anyone run any tests against currently deployed recursive resolvers and authoritative servers to see what they do when sent the initial DTLS packet? Paul, openssl s_client -dtls1 -connect 1.2.3.4:53 -debug substituting 1.2.3.4 for the server you want to test, and in another window do tcpdump port 53. -d ___ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
Re: [DNSOP] DNS over DTLS (DNSoD)
On Apr 23, 2014, at 8:42 AM, Dan Wing dw...@cisco.com wrote: On Apr 23, 2014, at 7:26 AM, Paul Hoffman paul.hoff...@vpnc.org wrote: On Apr 23, 2014, at 6:47 AM, Dan Wing d...@danwing.org wrote: For discussion. DNS queries and responses are visible to network elements on the path between the DNS client and its server. These queries and responses can contain privacy-sensitive information which is valuable to protect. An active attacker can send bogus responses causing misdirection of the subsequent connection. To counter passive listening and active attacks, this document proposes the use of Datagram Transport Layer Security (DTLS) for DNS, to protect against passive listeners and certain active attacks. As DNS needs to remain fast, this proposal also discusses mechanisms to reduce DTLS round trips and reduce DTLS handshake size. The proposed mechanism runs over the default DNS port and can also run over an alternate port. http://tools.ietf.org/html/draft-wing-dnsop-dnsodtls This proposes to run a binary protocol (DTLS) over port 53. It says A DNS client or server that does not implement this specification will not respond to the incoming DTLS packets because they don't parse as DNS packets (the DNS Opcode would be 15, which is undefined). Has anyone run any tests against currently deployed recursive resolvers and authoritative servers to see what they do when sent the initial DTLS packet? Paul, openssl s_client -dtls1 -connect 1.2.3.4:53 -debug substituting 1.2.3.4 for the server you want to test, and in another window do tcpdump port 53. Sure. What were the results of your testing? --Paul Hoffman ___ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
Re: [DNSOP] DNS over DTLS (DNSoD)
On Apr 23, 2014, at 6:47 AM, Dan Wing d...@danwing.org wrote: For discussion. DNS queries and responses are visible to network elements on the path between the DNS client and its server. These queries and responses can contain privacy-sensitive information which is valuable to protect. An active attacker can send bogus responses causing misdirection of the subsequent connection. To counter passive listening and active attacks, this document proposes the use of Datagram Transport Layer Security (DTLS) for DNS, to protect against passive listeners and certain active attacks. As DNS needs to remain fast, this proposal also discusses mechanisms to reduce DTLS round trips and reduce DTLS handshake size. The proposed mechanism runs over the default DNS port and can also run over an alternate port. http://tools.ietf.org/html/draft-wing-dnsop-dnsodtls a: With the need to do all the handshaking, you gain only a little from doing dTLS over UDP rather than TLS over TCP. So why use UDP with all its headaches? Just use TCP and conventional TLS rather than DTLS, especially when you are talking about mucking with the handshake. b: DO NOT USE PORT 53 for this: There are far far too many networks (1%+) that reinterpret DNS requests or just outright block all DNS to non-approved servers, and more still which block non-DNS over DNS. -- Nicholas Weaver it is a tale, told by an idiot, nwea...@icsi.berkeley.edufull of sound and fury, 510-666-2903 .signifying nothing PGP: http://www1.icsi.berkeley.edu/~nweaver/data/nweaver_pub.asc signature.asc Description: Message signed with OpenPGP using GPGMail ___ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
Re: [DNSOP] DNS over DTLS (DNSoD)
for reasons well-spoken up-thread, if we're going to add a dns transport, i'd like it to be RFC 6013 style TCP (in which session context can be compressed and retained after FIN for full-window-size restart, and which permits the query to be bundled into the SYN packet), or at a minimum, SCTP. DTLS does not solve any of the problems described at https://queue.acm.org/detail.cfm?id=2578510. vixie ___ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
Re: [DNSOP] DNS over DTLS (DNSoD)
On Wed, 23 Apr 2014, Nicholas Weaver wrote: b: DO NOT USE PORT 53 for this: There are far far too many networks (1%+) that reinterpret DNS requests or just outright block all DNS to non-approved servers, and more still which block non-DNS over DNS. Yes, I fully agree with this. It was a major objection for me to CurveDNS as well No, I fully disagree with this. Port 53 TCP has a much better chance at working these days than a random other newly assigned port. I'll go get a comfort coffee now. Paul ps. leaning towards custom crypto that fits in DNS formats ___ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
Re: [DNSOP] DNS over DTLS (DNSoD)
On Apr 23, 2014, at 1:00 PM, Paul Wouters p...@nohats.ca wrote: No, I fully disagree with this. Port 53 TCP has a much better chance at working these days than a random other newly assigned port. Not true. Port 53 is far more molested than random: INBOUND firewall rules prevent you from running new services without firewall rule modifications, but outbound blocking is far less common. (Our test port for this is TCP 1947 with Netalyzr). -- Nicholas Weaver it is a tale, told by an idiot, nwea...@icsi.berkeley.edufull of sound and fury, 510-666-2903 .signifying nothing PGP: http://www1.icsi.berkeley.edu/~nweaver/data/nweaver_pub.asc signature.asc Description: Message signed with OpenPGP using GPGMail ___ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
Re: [DNSOP] DNS over DTLS (DNSoD)
I agree that DTLS does not solve any problems for DNS. The basic problem is that DTLS is still based around the notion of a session where the server stores per connection state. So you might as well use TLS for this application. But TLS is not the only option available. Or rather using TLS to secure DNS is not the only option possible. If we use TLS to do a kerberos like key exchange, we can generate a shared secret and a ticket which can then be used to secure all future communications without changing from UDP. We can't run over port 53 (trust me, I tried). But we can nominate the ports to use in the key exchange setup. The resulting protocol works in about 93-98% of network situations (depending on how you measure). So you still need a Web Service backup. But it does work pretty well. On Wed, Apr 23, 2014 at 2:41 PM, Paul Vixie p...@redbarn.org wrote: for reasons well-spoken up-thread, if we're going to add a dns transport, i'd like it to be RFC 6013 style TCP (in which session context can be compressed and retained after FIN for full-window-size restart, and which permits the query to be bundled into the SYN packet), or at a minimum, SCTP. DTLS does not solve any of the problems described at https://queue.acm.org/detail.cfm?id=2578510. vixie ___ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop -- Website: http://hallambaker.com/ ___ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
