-
Notifications
You must be signed in to change notification settings - Fork 3
/
Copy pathdraft-reddy-add-iot-byod-bootstrap-01.txt
1008 lines (715 loc) · 43.4 KB
/
draft-reddy-add-iot-byod-bootstrap-01.txt
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
ADD WG T. Reddy
Internet-Draft McAfee
Intended status: Standards Track D. Wing
Expires: November 6, 2020 Citrix
M. Richardson
Sandelman Software Works
M. Boucadair
Orange
May 5, 2020
A Bootstrapping Procedure to Discover and Authenticate DNS-over-TLS and
DNS-over-HTTPS Servers for IoT and BYOD Devices
draft-reddy-add-iot-byod-bootstrap-00
Abstract
This document specifies mechanisms to bootstrap endpoints (e.g.,
hosts, IoT devices) to discover and authenticate DNS-over-TLS and
DNS-over-HTTPS servers provided by a local network for IoT/BYOD
devices in Enterprise networks.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 6, 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
Reddy, et al. Expires November 6, 2020 [Page 1]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Bootstrapping Endpoint Devices . . . . . . . . . . . . . . . 6
4.1. Bootstrapping BYOD . . . . . . . . . . . . . . . . . . . 6
5. Bootstrapping IoT Devices . . . . . . . . . . . . . . . . . . 8
6. Connection Handshake and Service Invocation . . . . . . . . . 9
7. EST Service Discovery Procedure . . . . . . . . . . . . . . . 10
8. Network Reattachment . . . . . . . . . . . . . . . . . . . . 10
9. Privacy Considerations . . . . . . . . . . . . . . . . . . . 12
10. Security Considerations . . . . . . . . . . . . . . . . . . . 12
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
11.1. Service Name for EST . . . . . . . . . . . . . . . . . . 13
11.2. Service Name for DoH . . . . . . . . . . . . . . . . . . 13
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
13.1. Normative References . . . . . . . . . . . . . . . . . . 13
13.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
Traditionally a caching DNS server has been provided by local
networks. This provides benefits such as low latency to reach that
DNS server (owing to its network proximity to the endpoint).
However, if an endpoint is configured to use Internet-hosted or
public DNS-over-TLS (DoT) [RFC7858] or DNS-over-HTTPS (DoH) [RFC8484]
servers, any available local DNS server cannot serve DNS requests
from local endpoints. If public DNS servers are used instead of
using local DNS servers, some operational problems can occur such as
those listed below:
o "Split DNS" [RFC2775] to use the special internal-only domain
names (e.g., "internal.example.com") in enterprise networks will
not work, and ".local" and "home.arpa" names cannot be locally
resolved in home networks.
o Content Delivery Networks (CDNs) that map traffic based on DNS may
lose the ability to direct end-user traffic to a nearby service-
specific cluster in cases where a DNS service is being used that
Reddy, et al. Expires November 6, 2020 [Page 2]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
is not affiliated with the local network and which does not send
"EDNS Client Subnet" (ECS) information [RFC7871] to the CDN's DNS
authorities [CDN].
If public DNS servers are used instead of local DNS servers, the
following discusses the impacts on network-based security:
o Various network security services are provided by Enterprise
networks to protect endpoints (e.g,. Hosts, IoT devices).
Network-based security solutions such as firewalls (FW) and
Intrusion Prevention Systems (IPS) rely on network traffic
inspection to implement perimeter-based security policies. The
network security services may for example prevent malware
download, block known malicious URLs, enforce use of strong
ciphers, stop data exfiltration, etc. These network security
services act on DNS requests originating from endpoints. However,
if an endpoint is configured to use public DoH/DoT servers,
network security services cannot act on DNS requests from these
endpoints.
o In order to act on DNS requests from endpoints, network security
services can block DoT traffic by dropping outgoing packets to
destination port 853. Identifying DoH traffic is far more
challenging than DoT traffic. Network security services may try
to identify the domains offering DoH servers, and DoH traffic can
be blocked by dropping outgoing packets to these domains. If an
endpoint has enabled strict privacy profile (Section 5 of
[RFC8310]), and the network security service blocks the traffic to
the public DNS server, the DNS service won't be available to the
endpoint and ultimately the endpoint cannot access Internet-
reachable services.
o If an endpoint has enabled opportunistic privacy profile
(Section 5 of [RFC8310]), and the network security service blocks
traffic to the public DNS server, the endpoint will either
fallback to an encrypted connection without authenticating the DNS
server provided by the local network or fallback to clear text
DNS, and cannot exchange encrypted DNS messages.
If the network security service fails to block DoH/DoT traffic, this
can compromise the endpoint security; some of the potential security
threats are listed below:
o The network security service cannot prevent an endpoint from
accessing malicious domains.
o If the endpoint is an IoT device which is configured to use public
DoH/DoT servers, and if a policy enforcement point in the local
Reddy, et al. Expires November 6, 2020 [Page 3]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
network is programmed using, for example, a Manufacturer Usage
Description (MUD) file [RFC8520] by a MUD manager to only allow
intended communications to and from the IoT device, the policy
enforcement point cannot enforce the network Access Control List
(ACL) rules based on domain names (Section 8 of [RFC8520]).
If the network security service successfully blocks DoT and DoH
traffic, this can still compromise the endpoint security and privacy;
some of the potential security threats are listed below:
o Networks are susceptible to internal attacks as discussed in
Section 3.2 of [I-D.arkko-farrell-arch-model-t]. An internal
attacker can modify the DNS responses to re-direct the client to
malicious servers.
o Pervasive monitoring of DNS traffic.
In addition, the local network's DNS server is advertised using DHCP/
RA which is insecure and also provides no mechanism to securely
authenticate the DNS server. To overcome the above threats, this
document specifies a mechanism to bootstrap endpoints to discover and
authenticate the DoT and DoH servers provided by their local network.
The overall procedure can be structured into the following steps:
o Bootstrapping (Section 4) is necessary only when connecting to a
new network or when the network's DNS certificate has changed.
Bootstrapping procedure authenticates the Enrollment over Secure
Transport (EST) [RFC7030] server to the endpoint. After
authenticating the EST server, DNS server certificate used by the
local network is downloaded to the endpoint. This DNS server
certificate enables subsequent authenticated encrypted
communication with the local DNS server (e.g., DoH) during in the
connection phase.
o Connection handshake and service invocation (Section 6): The DNS
client initiates a TLS handshake with the DNS server learned in
the discovery phase, and validates the DNS server's identity using
the credentials obtained in the bootstrapping phase.
Note: The strict and opportunistic privacy profiles as defined in
[RFC8310] only applies to DoT protocol, there has been no such
distinction made for DoH protocol.
2. Scope
The problems discussed in Section 1 will be encountered in Enterprise
networks. Typically Enterprise networks do not assume that all
devices in their network are managed by the IT team or Mobile Device
Reddy, et al. Expires November 6, 2020 [Page 4]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
Management (MDM) devices, especially in the quite common BYOD ("Bring
Your Own Device") scenario. The mechanisms specified in this
document can be used by BYOD devices to discover and authenticate DoT
and DoH servers provided by the Enterprise network. This mechanism
can also be used by IoT devices (managed by IT team) after onboarding
to discover and authenticate DoT and DoH servers provided by the
Enterprise network.
Wireless LAN as frequently deployed is vulnerable to various attacks
([Evil-Twin],[Krack] and [Dragonblood]). Because of these attacks,
only cryptographically authenticated communications are trusted on
Wireless LAN networks. This means information provided by such
networks via DHCP, DHCPv6, or RA (e.g., NTP server, DNS server,
default domain) are untrusted because DHCP and RA are not
authenticated. [I-D.btw-add-home] discusses DoH/DoT server discovery
using DHCP/RA but requires the DoH/DoT server to be pre-configured in
the endpoint (OS or Browser) or the DNS client must be able
cryptographically identify it is connecting to a DoT/DoH server
hosted by a specific organization (e.g., ISP or Enterprise) (see
[I-D.reddy-add-server-policy-selection]) to prevent the client from
connecting to a attackers server.
Users have to indicate to their system in some way that they desire
bootstrapping to be performed only when connecting to a specific
network (e.g., organization for which a user works or a user works
temporarily within another corporation), similar to the way users
disable VPN connection in specific network (e.g., Enterprise network)
and enable VPN connection by default in other networks. If the
discovered DNS server meets the privacy preserving data policy
requirements of the user, the user can select to use the discovered
DoT and DoH servers.
3. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
This document makes use of the terms defined in [RFC8499] and
[I-D.ietf-dnsop-terminology-ter].
'DoH/DoT' refers to DNS-over-HTTPS and/or DNS-over-TLS.
Reddy, et al. Expires November 6, 2020 [Page 5]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
4. Bootstrapping Endpoint Devices
If a device is managed by an enterprise's IT department, the device
can be configured to use Enterprise-provided DoH/DoT servers. This
configuration might be manual or rely upon whatever deployed device
management tool in an Enterprise. For example, customizing Firefox
using Group Policy to use the Enterprise DoH server is discussed in
[Firefox-Policy] for Windows and MacOS, and setting Chrome policies
is discussed in [Chrome-Policy] and [Chrome-DoH].
If mobile device management (MDM) (e.g, [MDM-Apple]) is used to
secure BYOD, MDM can be used to configure OS/browser with the
Enterprise provided DoH/DoT server. If an endpoint is on-boarded,
for example, using Over-The-Air (OTA) enrollment [OTA] to provision
the device with a certificate and configuration profile, the
configuration profile can include the authentication domain name
(ADN) of the DoH/DoT server. The OS/Browser can use the
configuration profile to use the Enterprise provided DoH/DoT server.
In this case, MDM is not installed on the device.
4.1. Bootstrapping BYOD
This section focuses on bootstrapping Bring your own device (BYOD) to
discover and authenticate DoH/DoT server provided by the enterprise
network but without MDM or configuration profile on the endpoint. If
an endpoint uses the credentials (username and password) provided by
the IT admin to mutually authenticate to the Enterprise WLAN Access
Point (e.g., PEAP-MSCHAPv2 [PEAP], EAP-pwd [RFC8146], EAP-PSK
[RFC4764]), the following steps can be used to securely bootstrap the
endpoint with the authentication domain name (ADN, defined in
[RFC8310]) and DNS server certificate of the local network's DoH/DoT
server:
1. The endpoint authenticates to the local network and discovers the
Enrollment over Secure Transport (EST) [RFC7030] server using the
procedure discussed in Section 7.
2. The endpoint establishes provisional TLS connection with that EST
server, i.e., the endpoint provisionally accepts the unverified
TLS server certificate. However, the endpoint MUST authenticate
the EST server before it accepts the DNS server certificate. The
endpoint either uses password-based authenticated key exchange
(PAKE) with TLS 1.3 [I-D.barnes-tls-pake] as an authentication
method or uses the mutual authentication protocol for HTTP
[RFC8120] to authenticate the discovered EST server.
As a reminder, PAKE is an authentication method that allows the
use of usernames and passwords over unencrypted channels without
Reddy, et al. Expires November 6, 2020 [Page 6]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
revealing the passwords to an eavesdropper. Similarly, the
mutual authentication for HTTP is based on PAKE and provides
mutual authentication between an HTTP client and an HTTP server
using username and password as credentials. The cryptographic
algorithms to use with the mutual authentication protocol for
HTTP are defined in [RFC8121].
Note that the Crypto Forum Research Group (cfrg) has selected
draft-haase-cpace and draft-krawczyk-cfrg-opaque drafts to
recommend for balanced and augmented password-based authenticated
key establishment in IETF protocols. This step will be further
updated.
3. The endpoint needs to use PAKE scheme to perform authentication
the first time it connects to an EST server. If the EST server
authentication is successful, the server's identity can be used
to authenticate subsequent TLS connections to that EST server.
The endpoint configures the reference identifier for the EST
server using the DNS-ID identifier type in the EST server
certificate. On subsequent connections to the EST server, the
endpoint MUST validate the EST server certificate using the
Implict Trust Anchor database (i.e, the EST server certificate
must pass PKIX certification path validation [RFC6125]) and match
the reference identifier against the EST server's identity
according to the rules specified in Section 6.4 of [RFC6125].
4. The endpoint learns the End-Entity certificates [RFC8295] from
the EST server. The certificate provisioned to the DNS server in
the local network will be treated as a End-Entity certificate.
As a reminder, the End-Entity certificates must be validated by
the endpoint using an authorized trust anchor (Section 3.2 of
[RFC8295]). The endpoint needs to identify the certificate
provisioned to the DNS server. The SRV-ID identifier type
[RFC6125] within subjectAltName entry MUST be used to identify
the DNS server certificate.
For example, DNS server certificate will include SRV-ID "_domain-
s.example.net" along with DNS-ID "example.net". The SRV service
label "domain-s" is defined in Section 6 of [RFC7858] for DoT
protocol. The SRV service label "doh" is defined in Section 11
for DoH protocol.
5. The endpoint configures the authentication domain name (ADN)
(defined in [RFC8310]) for the DNS server from the DNS-ID
identifier type within subjectAltName entry in the DNS server
certificate. The DNS server certificate is associated with the
ADN to be matched with the certificate given by the DNS server in
Reddy, et al. Expires November 6, 2020 [Page 7]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
TLS. To some extent, this approach is similar to certificate
usage PKIX-EE(1) defined in [RFC7671].
Figure 1 illustrates a sequence diagram for bootstrapping an endpoint
with the local network's ADN and DNS server certificate.
+----------+ +--------+ +--------+
| Endpoint | | EST | | DNS |
| | | Server | | Server |
+----------+ +--------+ +--------+
| DNS-SD query to discover the EST server | |
|-------------------------------------------------------->|
| | |
| optional: mDNS query to | |
| discover the EST server | |
|--------------------------------------------->| |
| | |
| Establish provisional TLS connection | |
|<-------------------------------------------->| |
| | |
| PAKE scheme to authenticate the EST server | |
|<-------------------------------------------->| |
| | |
[Generate reference identifier for the EST server | |
to compare with the EST server certificate | |
in subsequent TLS connections] | |
| | |
| Get EE certificates | |
|--------------------------------------------->| |
| | |
[Identify the DNS server certificate in EE | |
certificates to match with the certificate | |
by the DNS server in TLS handshake] | |
| |
[Configure ADN and associate DNS server certificate] | |
| | |
Figure 1: Bootstrapping Endpoint Devices
5. Bootstrapping IoT Devices
The following steps explain the mechanism to bootstrap IoT devices
supporting Bootstrapping Remote Secure Key Infrastructures (BRSKI)
discussed in [I-D.ietf-anima-bootstrapping-keyinfra] with local
network's CA certificates, ADN and DNS server certificate:
o Bootstrapping Remote Secure Key Infrastructures (BRSKI) discussed
in [I-D.ietf-anima-bootstrapping-keyinfra] provides a solution for
Reddy, et al. Expires November 6, 2020 [Page 8]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
secure automated bootstrap of devices. BRSKI specifies means to
provision credentials on devices to be used to operationally
access networks. In addition, BRSKI provides an automated
mechanism for the bootstrap distribution of CA certificates from
the EST server. The IoT device can use BRSKI to bootstrap the IoT
device using the IoT manufacturer provisioned X.509 certificate,
in combination with a registrar provided by the local network and
IoT device manufacturer's authorizing service (MASA):
1. The IoT device authenticates to the local network using the
IoT manufacturer provisioned X.509 certificate. The IoT
device can request and get a voucher from the MASA service via
the registrar. The voucher is signed by the MASA service and
includes the local network's CA public key.
2. The IoT device validates the signed voucher using the
manufacturer installed trust anchor associated with the MASA,
stores the CA's public key and validates the provisional TLS
connection to the registrar.
3. The IoT device requests the full EST distribution of current
CA certificates (Section 5.9.1 in
[I-D.ietf-anima-bootstrapping-keyinfra]) from the registrar
operating as a BRSKI-EST server. The IoT devices stores the
CA certificates as Explicit Trust Anchor database entries.
The IoT device uses the Explicit Trust Anchor database to
validate the DNS server certificate.
4. The IoT device learns the End-Entity certificates from the
BRSKI-EST server. The certificate provisioned to the DNS
server in the local network will be treated as an End-Entity
certificate. The IoT device needs to identify the certificate
provisioned to the DNS server. The SRV-ID identifier type
within subjectAltName entry MUST be used to identify the DNS
server certificate (see Step 4 in Section 4.1).
5. The endpoint configures the ADN for the DNS server from the
DNS-ID identifier type within subjectAltName entry in the DNS
server certificate. The DNS server certificate is associated
with the ADN to be matched with the certificate given by the
DNS server in TLS.
6. Connection Handshake and Service Invocation
The DNS client resolves the ADN using the mechanism discussed in
Section 7.2 of [RFC8310]. The DNS client initiates TLS handshake
with the DNS server, the DNS server presents its certificate in
ServerHello message, and the DNS client MUST match the DNS server
Reddy, et al. Expires November 6, 2020 [Page 9]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
certificate downloaded in Step 4 in Section 4.1 or Section 5 with the
certificate provided by the DNS server in TLS handshake. If the
match is successful, the DNS client MUST validate the server
certificate using an authorized trust anchor.
If the match is successful and server certificate is successfully
validated, the client continues with the connection as normal.
Otherwise, the client MUST treat the server certificate validation
failure as a non-recoverable error. If the DNS client cannot reach
or establish an authenticated and encrypted connection with the
privacy-enabling DNS server provided by the local network, the DNS
client can fallback to a privacy-enabling public DNS server.
The DoH client contacts that DoH resolver to retrieve the list of
supported DoH services using the well-known URI defined in
[I-D.btw-add-rfc8484-clarification].
7. EST Service Discovery Procedure
An EST client discovers the EST server in the local network by using
DNS-based Service Discovery (DNS-SD) [RFC6763] or Multicast DNS
(mDNS) [RFC6762]. The <Domain> portion specifies the DNS sub-domain
where the service instance is registered. It may be "local.",
indicating the mDNS local domain, or it may be a conventional domain
name such as "example.com.". The <Service> portion of the EST
service instance name MUST be "_est._tcp".
A EST client application can proactively discover an EST server being
advertised in the site by multicasting a PTR query to the following:
"_est._tcp.local"
An EST server can send out gratuitous multicast DNS answer packets
whenever it starts up, wakes from sleep, or detects a change in EST
server configuration. EST client application can receive these
gratuitous packets and cache information contained in them.
8. Network Reattachment
On subsequent attachments to the network, the endpoint initiates TLS
handshake with the DoH/DoT server (configured in Step 5 of
Section 4.1 or Section 5) and follows the mechanism discussed in
Section 6 to validate the DNS server certificate.
If the DNS server certificate is invalid (e.g., revoked or expired),
the endpoint discovers and initiates TLS handshake with the EST
server, and uses the validation techniques described in [RFC6125] to
compare the reference identifier (created in Step 2 of Section 4.1 in
Reddy, et al. Expires November 6, 2020 [Page 10]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
this document) to the EST server certificate and verifies the entire
certification path as per [RFC5280]. The endpoint then gets the DNS
server certificate from the EST server. If the DNS-ID identifier
type within subjectAltName entry in the DNS server certificate does
not match the configured ADN, the ADN is replaced with the DNS-ID
identifier type. The DNS server certificate associated with the ADN
is replaced with the one provided by the EST server. The endpoint
initiates TLS handshake with the newly discovered ADN and follows the
mechanism discussed in Section 6 to validate the DNS server
certificate.
Figure 2 illustrates a sequence diagram for re-configuring an
endpoint with ADN and local network's DNS server certificate on
subsequent attachments to the network.
+----------+ +--------+ +--------+
| Endpoint | | EST | | DNS |
| | | Server | | Server |
+----------+ +--------+ +--------+
| DNS-SD query to discover the EST server | |
|-------------------------------------------------------->|
| | |
| optional: mDNS query to | |
| discover the EST server | |
|--------------------------------------------->| |
| | |
| Establish TLS connection | |
| and validate EST server certificate | |
|<-------------------------------------------->| |
| | |
| Get EE certificates | |
|<-------------------------------------------->| |
| | |
[Identify the DNS server certificate in EE | |
certificates to match with the certificate | |
by the DNS server in TLS handshake] | |
| |
[Re-configure ADN and associate DNS server certificate]| |
| | |
Figure 2: Bootstrapping Endpoint Devices on subsequent attachments to
the network
Reddy, et al. Expires November 6, 2020 [Page 11]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
9. Privacy Considerations
[RFC7626] discusses DNS privacy considerations in both "on the wire"
(Section 2.4 of [RFC7626]) and "in the server" (Section 2.5 of
[RFC7626] contexts. The mechanism defined in
[I-D.reddy-add-server-policy-selection] can be used by the DNS server
to communicate its privacy statement URL and filtering policy to a
DNS client. This communication is cryptographically signed to attest
to its authenticity. By evaluating the DNS privacy statement,
filtering policy and the signatory, the client can use the discovered
DNS server if it meets privacy preserving data policy and filtering
requirements of the user.
10. Security Considerations
The bootstrapping procedure to obtain the certificate of the local
network's DNS server uses a client identity and password to
authenticate the EST server using PAKE schemes. Security
considerations such as those discussed in [I-D.barnes-tls-pake] or
[RFC8120] and [RFC8121] need to be taken into consideration.
Users cannot be expected to enable or disable the bootstrapping or
the discovery procedure as they switch networks. Thus, it is
RECOMMENDED that users indicate to their system in some way that they
desire bootstrapping to be performed when connecting to a specific
network, similar to the way users disable VPN connection in specific
network (e.g., Enterprise network) and enable VPN connection by
default in other networks.
If an endpoint has enabled strict privacy profile, and the network
security service blocks the traffic to the privacy-enabling public
DNS server, a hard failure occurs and the user is notified. The user
has a choice to switch to another network or if the user trusts the
network, the user can enable strict privacy profile with the DoH/DoT
server discovered in the network instead of downgrading to
opportunistic privacy profile.
The primary attacks against the methods described in Section 7 are
the ones that would lead to impersonation of a EST server and
spoofing the DNS response to indicate that the network does not
support any EST server. To protect against DNS-vectored attacks,
secured DNS (DNSSEC) can be used to ensure the validity of the DNS
records received. Impersonation of the EST server is prevented by
authenticating the EST server using the PAKE scheme. The PAKE scheme
is only used once to configure the reference identifier of the EST
server and the server certificate is validated for subsequent TLS
connections to the EST server.
Reddy, et al. Expires November 6, 2020 [Page 12]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
Security considerations in [I-D.ietf-anima-bootstrapping-keyinfra]
need to be taken into consideration for IoT devices.
11. IANA Considerations
11.1. Service Name for EST
IANA is requested to allocate the following service name from the
registry available at: https://www.iana.org/assignments/service-
names-port-numbers/service-names-port-numbers.xhtml.
Service Name: est
Port Number: N/A
Transport Protocol(s): TCP
Description: Enrollment over Secure Transport (EST)
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>
Reference: [ThisDocument]
11.2. Service Name for DoH
IANA is requested to allocate the following service name from the
registry available at: https://www.iana.org/assignments/service-
names-port-numbers/service-names-port-numbers.xhtml.
Service Name: doh
Port Number: N/A
Transport Protocol(s): TCP
Description: DNS-over-HTTPS
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>
Reference: [ThisDocument]
12. Acknowledgments
Thanks to Joe Hildebrand, Harsha Joshi, Shashank Jain, Patrick
McManus, Bob Harold, Livingood Jason, Winfield Alister, Eliot Lear,
Stephane Bortzmeyer, Ted Lemon and Sara Dickinson for the discussion
and comments.
13. References
13.1. Normative References
Reddy, et al. Expires November 6, 2020 [Page 13]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
[I-D.ietf-anima-bootstrapping-keyinfra]
Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
keyinfra-41 (work in progress), April 2020.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <https://www.rfc-editor.org/info/rfc6125>.
[RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
DOI 10.17487/RFC6762, February 2013,
<https://www.rfc-editor.org/info/rfc6762>.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
<https://www.rfc-editor.org/info/rfc6763>.
[RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
"Enrollment over Secure Transport", RFC 7030,
DOI 10.17487/RFC7030, October 2013,
<https://www.rfc-editor.org/info/rfc7030>.
[RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
and P. Hoffman, "Specification for DNS over Transport
Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
2016, <https://www.rfc-editor.org/info/rfc7858>.
[RFC8121] Oiwa, Y., Watanabe, H., Takagi, H., Maeda, K., Hayashi,
T., and Y. Ioku, "Mutual Authentication Protocol for HTTP:
Cryptographic Algorithms Based on the Key Agreement
Mechanism 3 (KAM3)", RFC 8121, DOI 10.17487/RFC8121, April
2017, <https://www.rfc-editor.org/info/rfc8121>.
Reddy, et al. Expires November 6, 2020 [Page 14]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8295] Turner, S., "EST (Enrollment over Secure Transport)
Extensions", RFC 8295, DOI 10.17487/RFC8295, January 2018,
<https://www.rfc-editor.org/info/rfc8295>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>.
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/info/rfc8499>.
13.2. Informative References
[CDN] "End-User Mapping: Next Generation Request Routing for
Content Delivery", 2015,
<https://conferences.sigcomm.org/sigcomm/2015/pdf/papers/
p167.pdf>.
[Chrome-DoH]
The Unicode Consortium, "Chrome DNS over HTTPS (aka DoH)",
<https://www.chromium.org/developers/dns-over-https>.
[Chrome-Policy]
The Unicode Consortium, "Chrome policies for users or
browsers", <https://support.google.com/chrome/a/
answer/2657289?hl=en>.
[Dragonblood]
The Unicode Consortium, "Dragonblood: Analyzing the
Dragonfly Handshake of WPA3 and EAP-pwd",
<https://papers.mathyvanhoef.com/dragonblood.pdf>.
[Evil-Twin]
The Unicode Consortium, "Evil twin (wireless networks)",
<https://en.wikipedia.org/wiki/
Evil_twin_(wireless_networks)>.
[Firefox-Policy]
"Policy templates for Firefox",
<https://github.com/mozilla/policy-templates/blob/master/
README.md#dnsoverhttps>.
Reddy, et al. Expires November 6, 2020 [Page 15]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
[I-D.arkko-farrell-arch-model-t]
Arkko, J. and S. Farrell, "Challenges and Changes in the
Internet Threat Model", draft-arkko-farrell-arch-model-
t-04 (work in progress), July 2020.
[I-D.barnes-tls-pake]
Barnes, R. and O. Friel, "Usage of PAKE with TLS 1.3",
draft-barnes-tls-pake-04 (work in progress), July 2018.
[I-D.btw-add-home]
Boucadair, M., Reddy.K, T., Wing, D., and N. Cook,
"Encrypted DNS Discovery and Deployment Considerations for
Home Networks", draft-btw-add-home-07 (work in progress),
July 2020.
[I-D.btw-add-rfc8484-clarification]
Boucadair, M., Cook, N., Reddy.K, T., and D. Wing,
"Supporting Redirection for DNS Queries over HTTPS (DoH)",
draft-btw-add-rfc8484-clarification-02 (work in progress),
July 2020.
[I-D.ietf-dnsop-terminology-ter]
Hoffman, P., "Terminology for DNS Transports and
Location", draft-ietf-dnsop-terminology-ter-01 (work in
progress), February 2020.
[I-D.reddy-add-server-policy-selection]
Reddy.K, T., Wing, D., Richardson, M., and M. Boucadair,
"DNS Server Selection: DNS Server Information with
Assertion Token", draft-reddy-add-server-policy-
selection-03 (work in progress), June 2020.
[Krack] The Unicode Consortium, "Key Reinstallation Attacks",
2017, <https://www.krackattacks.com/>.
[MDM-Apple]
Apple, "Mobile Device Management",
<https://developer.apple.com/documentation/
devicemanagement>.
[OTA] Apple, "Over-the-Air Profile Delivery Concepts", <https://
developer.apple.com/library/archive/documentation/Networki
ngInternet/Conceptual/iPhoneOTAConfiguration/OTASecurity/
OTASecurity.html>.
Reddy, et al. Expires November 6, 2020 [Page 16]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
[PEAP] Microsoft, "[MS-PEAP]: Protected Extensible Authentication
Protocol (PEAP)", <https://docs.microsoft.com/en-
us/openspecs/windows_protocols/ms-peap/5308642b-90c9-4cc4-
beec-fb367325c0f9>.
[RFC2775] Carpenter, B., "Internet Transparency", RFC 2775,
DOI 10.17487/RFC2775, February 2000,
<https://www.rfc-editor.org/info/rfc2775>.
[RFC4764] Bersani, F. and H. Tschofenig, "The EAP-PSK Protocol: A
Pre-Shared Key Extensible Authentication Protocol (EAP)
Method", RFC 4764, DOI 10.17487/RFC4764, January 2007,
<https://www.rfc-editor.org/info/rfc4764>.
[RFC7626] Bortzmeyer, S., "DNS Privacy Considerations", RFC 7626,
DOI 10.17487/RFC7626, August 2015,
<https://www.rfc-editor.org/info/rfc7626>.
[RFC7671] Dukhovni, V. and W. Hardaker, "The DNS-Based
Authentication of Named Entities (DANE) Protocol: Updates
and Operational Guidance", RFC 7671, DOI 10.17487/RFC7671,
October 2015, <https://www.rfc-editor.org/info/rfc7671>.
[RFC7871] Contavalli, C., van der Gaast, W., Lawrence, D., and W.
Kumari, "Client Subnet in DNS Queries", RFC 7871,
DOI 10.17487/RFC7871, May 2016,
<https://www.rfc-editor.org/info/rfc7871>.
[RFC8120] Oiwa, Y., Watanabe, H., Takagi, H., Maeda, K., Hayashi,
T., and Y. Ioku, "Mutual Authentication Protocol for
HTTP", RFC 8120, DOI 10.17487/RFC8120, April 2017,
<https://www.rfc-editor.org/info/rfc8120>.
[RFC8146] Harkins, D., "Adding Support for Salted Password Databases
to EAP-pwd", RFC 8146, DOI 10.17487/RFC8146, April 2017,
<https://www.rfc-editor.org/info/rfc8146>.
[RFC8310] Dickinson, S., Gillmor, D., and T. Reddy, "Usage Profiles
for DNS over TLS and DNS over DTLS", RFC 8310,
DOI 10.17487/RFC8310, March 2018,
<https://www.rfc-editor.org/info/rfc8310>.
[RFC8520] Lear, E., Droms, R., and D. Romascanu, "Manufacturer Usage
Description Specification", RFC 8520,
DOI 10.17487/RFC8520, March 2019,
<https://www.rfc-editor.org/info/rfc8520>.
Reddy, et al. Expires November 6, 2020 [Page 17]
Internet-DrDoT/DoH server discovery for for BYOD/IoT devices May 2020
Authors' Addresses
Tirumaleswar Reddy
McAfee, Inc.
Embassy Golf Link Business Park
Bangalore, Karnataka 560071
India
Email: kondtir@gmail.com
Dan Wing
Citrix Systems, Inc.
USA
Email: dwing-ietf@fuggles.com
Michael C. Richardson
Sandelman Software Works
USA
Email: mcr+ietf@sandelman.ca
Mohamed Boucadair
Orange
Rennes 35000
France
Email: mohamed.boucadair@orange.com