-
Notifications
You must be signed in to change notification settings - Fork 5
/
Copy pathdtbootstrap-anima-keyinfra-02.txt
2128 lines (1506 loc) · 90.1 KB
/
dtbootstrap-anima-keyinfra-02.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
ANIMA WG M. Pritikin
Internet-Draft Cisco
Intended status: Informational M. Richardson
Expires: September 18, 2016 SSW
M. Behringer
S. Bjarnason
Cisco
March 17, 2016
Bootstrapping Key Infrastructures
draft-ietf-anima-bootstrapping-keyinfra-02
Abstract
This document specifies automated bootstrapping of a key
infrastructure (BSKI) using vendor installed IEEE 802.1AR
manufacturing installed certificates, in combination with a vendor
based service on the Internet. Before being authenticated, a new
device has only link-local connectivity, and does not require a
routable address. When a vendor provides an Internet based service,
devices can be forced to join only specific domains but in limited/
disconnected networks or legacy environments we describe a variety of
options that allow bootstrapping to proceed.
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 http://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 September 18, 2016.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
Pritikin, et al. Expires September 18, 2016 [Page 1]
Internet-Draft Bootstrapping Key Infrastructures March 2016
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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 . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Scope of solution . . . . . . . . . . . . . . . . . . . . 5
1.3. Trust bootstrap . . . . . . . . . . . . . . . . . . . . . 6
2. Architectural Overview . . . . . . . . . . . . . . . . . . . 6
3. Functional Overview . . . . . . . . . . . . . . . . . . . . . 9
3.1. Behavior of a New Entity . . . . . . . . . . . . . . . . 10
3.1.1. Discovery . . . . . . . . . . . . . . . . . . . . . . 12
3.1.2. Identity . . . . . . . . . . . . . . . . . . . . . . 13
3.1.3. Request Join . . . . . . . . . . . . . . . . . . . . 14
3.1.4. Imprint . . . . . . . . . . . . . . . . . . . . . . . 14
3.1.5. Enrollment . . . . . . . . . . . . . . . . . . . . . 15
3.1.6. Being Managed . . . . . . . . . . . . . . . . . . . . 16
3.2. Behavior of a Proxy . . . . . . . . . . . . . . . . . . . 16
3.2.1. CoAP connection to Registrar . . . . . . . . . . . . 16
3.2.2. HTTPS proxy connection to Registrar . . . . . . . . . 17
3.3. Behavior of the Registrar (Bootstrap Server) . . . . . . 18
3.3.1. Entity Authentication . . . . . . . . . . . . . . . . 19
3.3.2. Entity Authorization . . . . . . . . . . . . . . . . 19
3.3.3. Claiming the New Entity . . . . . . . . . . . . . . . 20
3.3.4. Log Verification . . . . . . . . . . . . . . . . . . 20
3.3.5. Forwarding Audit Token plus Configuration . . . . . . 21
3.4. Behavior of the MASA Service . . . . . . . . . . . . . . 21
3.4.1. Issue Authorization Token and Log the event . . . . . 21
3.4.2. Retrieve Audit Entries from Log . . . . . . . . . . . 22
3.5. Leveraging the new key infrastructure / next steps . . . 22
3.5.1. Network boundaries . . . . . . . . . . . . . . . . . 22
3.6. Interactions with Network Access Control . . . . . . . . 22
4. Domain Operator Activities . . . . . . . . . . . . . . . . . 23
4.1. Instantiating the Domain Certification Authority . . . . 23
4.2. Instantiating the Registrar . . . . . . . . . . . . . . . 23
4.3. Accepting New Entities . . . . . . . . . . . . . . . . . 23
4.4. Automatic Enrollment of Devices . . . . . . . . . . . . . 24
4.5. Secure Network Operations . . . . . . . . . . . . . . . . 24
5. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 25
5.1. IEEE 802.1AR as client identity . . . . . . . . . . . . . 27
Pritikin, et al. Expires September 18, 2016 [Page 2]
Internet-Draft Bootstrapping Key Infrastructures March 2016
5.2. EST over CoAP . . . . . . . . . . . . . . . . . . . . . . 28
5.3. Request Audit Token . . . . . . . . . . . . . . . . . . . 28
5.4. Request Audit Token from MASA . . . . . . . . . . . . . . 29
5.5. Basic Configuration Information Package . . . . . . . . . 30
5.6. Request MASA authorization log . . . . . . . . . . . . . 31
6. Reduced security operational modes . . . . . . . . . . . . . 32
6.1. Trust Model . . . . . . . . . . . . . . . . . . . . . . . 32
6.2. New Entity security reductions . . . . . . . . . . . . . 33
6.3. Registrar security reductions . . . . . . . . . . . . . . 33
6.4. MASA security reductions . . . . . . . . . . . . . . . . 34
7. Security Considerations . . . . . . . . . . . . . . . . . . . 34
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 36
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 36
9.1. Normative References . . . . . . . . . . . . . . . . . . 36
9.2. Informative References . . . . . . . . . . . . . . . . . 37
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 38
1. Introduction
To literally "pull yourself up by the bootstraps" is an impossible
action. Similarly the secure establishment of a key infrastructure
without external help is also an impossibility. Today it is accepted
that the initial connections between nodes are insecure, until key
distribution is complete, or that domain-specific keying material is
pre-provisioned on each new device in a costly and non-scalable
manner. This document describes a zero-touch approach to
bootstrapping an entity by securing the initial distribution of key
material using third-party generic keying material, such as a
manufacturer installed IEEE 802.1AR certificate [IDevID], and a
corresponding third-party service on the Internet.
The two sides of an association being bootstrapped authenticate each
other and then determine appropriate authorization. This process is
described as four distinct steps between the existing domain and the
new entity being added:
o New entity authentication: "Who is this? What is its identity?"
o New entity authorization: "Is it mine? Do I want it? What are
the chances it has been compromised?"
o Domain authentication: "What is this domain's claimed identity?"
o Domain authorization: "Should I join it?"
A precise answer to these questions can not be obtained without
leveraging some established key infrastructure(s). A complexity that
this protocol deals with are dealing with devices from a variety of
Pritikin, et al. Expires September 18, 2016 [Page 3]
Internet-Draft Bootstrapping Key Infrastructures March 2016
vendors, and a network infrastructure (the domain) that is operated
by parties that do not have any priviledged relationship with the
device vendors. The domain's decisions are based on the new entity's
authenticated identity, as established by verification of previously
installed credentials such as a manufacturer installed IEEE 802.1AR
certificate, and verified back-end information such as a configured
list of purchased devices or communication with a (unidirectionally)
trusted third-party. The new entity's decisions are made according
to verified communication with a trusted third-party or in a strictly
auditable fashion.
Optimal security is achieved with IEEE 802.1AR certificates on each
new entity, accompanied by a third-party Internet based service for
verification. Bootstrapping concepts run to completion with less
requirements, but are then less secure. A domain can choose to
accept lower levels of security when a trusted third-party is not
available so that bootstrapping proceeds even at the risk of reduced
security. Only the domain can make these decisions based on
administrative input and known behavior of the new entity.
The result of bootstrapping is that a domain specific key
infrastructure is deployed. Since IEEE 802.1AR PKI certificates are
used for identifying the new entity, and the public key of the domain
identity is leveraged during communications with an Internet based
service, which is itself authenticated using HTTPS, bootstrapping of
a domain specific Public Key Infrastructure (PKI) is described.
Sufficient agility to support bootstrapping alternative key
infrastructures (such as symmetric key solutions) is considered
although no such alternate key infrastructure is described.
1.1. 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
[RFC2119].
The following terms are defined for clarity:
DomainID: The domain identity is the 160-bit SHA-1 hash of the BIT
STRING of the subjectPublicKey of the domain trust anchor that is
stored by the Domain CA. This is consistent with the RFC5280
Certification Authority subject key identifier of the Domain CA's
self signed root certificate. (A string value bound to the Domain
CA's self signed root certificate subject and issuer fields is
often colloquially used as a humanized identity value but during
protocol discussions the more exact term as defined here is used).
Pritikin, et al. Expires September 18, 2016 [Page 4]
Internet-Draft Bootstrapping Key Infrastructures March 2016
drop ship: The physical distribution of equipment containing the
"factory default" configuration to a final destination. In zero-
touch scenarios there is no staging or pre-configuration during
drop-ship.
imprint: the process where a device obtains the cryptographic key
material to identity and trust future interactions with a network.
This term is taken from Konrad Lorenz's work in biology with new
ducklings: during a critical period, the duckling would assume
that anything that looks like a mother duck is in fact their
mother. An equivalent for a device is to obtain the fingerprint
of the network's root certification authority certificate. A
device that imprints on an attacker suffers a similar fate to a
duckling that imprints on a hungry wolf. Securely imprinting is a
primary focus of this document.[imprinting].
enrollment: the process where a device presents key material to a
network and acquires a network specific identity. For example
when a certificate signing request is presented to a certification
authority and a certificate is obtained in response.
pledge: the prospective device, which has the identity provided to
at the factory. Neither the device nor the network knows if the
device yet knows if this device belongs with this network. This
is definition 6, according to [pledge]
Audit Token: A signed token from the manufacturer authorized signing
authority indicating that the bootstrapping event has been
successfully logged. This has been referred to as an
"authorization token" indicating that it authorizes bootstrapping
to proceed.
Ownership Voucher: A signed voucher from the vendor vouching that a
specific domain "owns" the new entity as defined in
[I-D.ietf-netconf-zerotouch].
1.2. Scope of solution
Questions have been posed as to whether this solution is suitable in
general for Internet of Things (IoT) networks. In general the answer
is no, but the terminology of [RFC7228] is best used to describe the
boundaries.
The entire solution described in this document is aimed in general at
non-constrained (i.e. class 2+) devices operating on a non-Challenged
network. The entire solution described here is not intended to be
useable as-is by constrained devices operating on challenged networks
(such as 802.15.4 LLNs).
Pritikin, et al. Expires September 18, 2016 [Page 5]
Internet-Draft Bootstrapping Key Infrastructures March 2016
In many target applications, the systems involved are large router
platforms with multi-gigabit inter-connections, mounted in controlled
access data centers. But this solution is not exclusive to the
large, it is intended to scale to thousands of devices located in
hostile environments, such as ISP provided CPE devices which are
drop-shipped to the end user. The situation where an order is
fulfilled from distributed warehouse from a common stock and shipped
directly to the target location at the request of the domain owner is
explicitly supported. That stock ("SKU") could be provided to a
number of potential domain owners, and the eventual domain owner will
not know a-priori which device will go to which location.
Specifically, there are protocol aspects described here which might
result in congestion collapse or energy-exhaustion of intermediate
battery powered routers in an LLN. Those types of networks SHOULD
NOT use this solution. These limitations are predominately related
to the large credential and key sizes required for device
authentication. Defining symmetric key techniques that meet the
operational requirements is out-of-scope but the underlying protocol
operations (TLS handshake and signing structures) have sufficient
algorithm agility to support such techniques when defined.
The imprint protocol described here could, however, be used by non-
energy constrained devices joining a non-constrained network (for
instance, smart light bulbs are usually mains powered, and speak
802.11). It could also be used by non-constrained devices across a
non-energy constrained, but challenged network (such as 802.15.4).
Some aspects are in scope for constrained devices on challenged
networks: the certificate contents, and the process by which the four
questions above are resolved is in scope. It is simply the actual
on-the-wire imprint protocol which is likely inappropriate.
1.3. Trust bootstrap
The imprint protocol results in a secure relationship between the
domain registrar and the new device. If the new device is
sufficiently constrained that the ACE protocol should be leveraged
for operation, (see [I-D.ietf-ace-actors]), and the domain registrar
is also the Client Authorization Server or the Authorization Server,
then it may be appropriate to use this secure channel to exchange ACE
tokens.
2. Architectural Overview
The logical elements of the bootstrapping framework are described in
this section. Figure 1 provides a simplified overview of the
Pritikin, et al. Expires September 18, 2016 [Page 6]
Internet-Draft Bootstrapping Key Infrastructures March 2016
components. Each component is logical and may be combined with other
components as necessary.
.
.+------------------------+
+--------------Drop Ship-------------->.| Vendor Service |
| .+------------------------+
| .| M anufacturer| |
| .| A uthorized |Ownership|
| .| S igning |Tracker |
| .| A uthority | |
| .+--------------+---------+
| .............. ^
V |
+-------+ ............................................|...
| | . | .
| | . +------------+ +-----------+ | .
| | . | | | | | .
| | . | | | <-------+ .
| | . | Proxy | | Registrar | .
| <--------> <-------> | .
| New | . | | | | .
| Entity| . +------------+ +-----+-----+ .
| | . | .
| | . +-----------------+----------+ .
| | . | Domain Certification | .
| | . | Authority | .
+-------+ . | Management and etc | .
. +----------------------------+ .
. .
................................................
"Domain" components
Figure 1
Domain: The set of entities that trust a common key infrastructure
trust anchor. This includes the Proxy, Registrar, Domain
Certificate Authority, Management components and any existing
entity that is already a member of the domain.
Domain CA: The domain Certification Authority (CA) provides
certification functionalities to the domain. At a minimum it
provides certification functionalities to the Registrar and stores
the trust anchor that defines the domain. Optionally, it
certifies all elements.
Pritikin, et al. Expires September 18, 2016 [Page 7]
Internet-Draft Bootstrapping Key Infrastructures March 2016
Registrar: A representative of the domain that is configured,
perhaps autonomically, to decide whether a new device is allowed
to join the domain. The administrator of the domain interfaces
with a Registrar to control this process. Typically a Registrar
is "inside" its domain.
New Entity: A new device or virtual machine or software component
that is not yet part of the domain.
Proxy: A domain entity that helps the New Entity join the domain. A
Proxy facilitates communication for devices that find themselves
in an environment where they are not provided connectivity until
after they are validated as members of the domain. The New Entity
is unaware that they are communicating with a proxy rather than
directly with the Registrar.
MASA Service: A Manufacturer Authorized Signing Authority (MASA)
service on the global Internet. The MASA provides a trusted
repository for audit log information concerning privacy protected
bootstrapping events.
Ownership Tracker An Ownership Tracker service on the global
internet. The Ownership Tracker uses business processes to
accurately track ownership of all devices shipped against domains
that have purchased them. Although optional this component allows
vendors to provide additional value in cases where their sales and
distribution channels allow for accurately tracking of such
ownership.
We assume a multi-vendor network. In such an environment there could
be a MASA or Ownership Tracker for each vendor that supports devices
following this document's specification, or an integrator could
provide a MASA service for all devices. It is unlikely that an
integrator could provide Ownership Tracking services for multiple
vendors.
This document describes a secure zero-touch approach to bootstrapping
a key infrastructure; if certain devices in a network do not support
this approach, they can still be bootstrapped manually. Although
manual deployment is not scalable and is not a focus of this document
the necessary mechanisms are called out in this document to ensure
such edge conditions are covered by the architectural and protocol
models.
Pritikin, et al. Expires September 18, 2016 [Page 8]
Internet-Draft Bootstrapping Key Infrastructures March 2016
3. Functional Overview
Entities behave in an autonomic fashion. They discover each other
and autonomically bootstrap into a key infrastructure delineating the
autonomic domain. See [I-D.irtf-nmrg-autonomic-network-definitions]
for more information.
This section details the state machine and operational flow for each
of the main three entities. The New Entity, the Domain (primarily
the Registrar) and the MASA service.
A representative flow is shown in Figure 2:
+--------+ +-------+ +------------+ +------------+
| New | | Proxy | | Domain | | Vendor |
| Entity | | | | Registrar | | Service |
| | | | | | | (Internet |
+--------+ +-------+ +------------+ +------------+
| | | |
|<-RFC3927 IPv4 adr | | |
or|<-RFC4862 IPv6 adr | | |
| | | |
|-------------------->| | |
| optional: mDNS query| | |
| RFC6763/RFC6762 | | |
| | | |
|<--------------------| | |
| mDNS broadcast | | |
| response or periodic| | |
| | | |
|<------------------->|<----------------->| |
| (d)TLS via the Proxy | |
|<--Registrar TLS server authentication---| |
[PROVISIONAL accept of server cert] | |
P---IEEE 802.1AR client authentication--->| |
P | | |
P---Request Audit Token (include nonce)-->| |
P | | |
P | /---> | |
P | | [accept device?] |
P | | [contact Vendor] |
P | | |--New Entity ID---->|
P | | |--Domain ID-------->|
P | | |--optional:nonce--->|
P | | | [extract DomainID]
P | | | |
P | optional: | [update audit log]
P | |can | |
Pritikin, et al. Expires September 18, 2016 [Page 9]
Internet-Draft Bootstrapping Key Infrastructures March 2016
P | |occur | optional: is |
P | |in | an ownership |
P | |advance | voucher available?
P | | | |
P | | |<-device audit log--|
P | | |<-audit token-------|
P | | | |
P | | |<-optional: --------|
P | \----> | ownership voucher |
P | | |
P | [verify audit log or voucher] |
P | | |
P<--Audit token and/or ownership voucher--| |
[verify response ]| | |
[verify provisional cert ]| | |
| | | |
|---------------------------------------->| |
| Continue with RFC7030 enrollment | |
| using now bidirectionally authenticated | |
| TLS session. | | |
| | | |
| | | |
| | | |
Figure 2
3.1. Behavior of a New Entity
A New Entity that has not yet been bootstrapped attempts to find a
local domain and join it. A New Entity MUST NOT automatically
initiate bootstrapping if it has already been configured.
States of a New Entity are as follows:
Pritikin, et al. Expires September 18, 2016 [Page 10]
Internet-Draft Bootstrapping Key Infrastructures March 2016
+--------------+
| Start |
| |
+------+-------+
|
+------v-------+
| Discover |
+------------> |
| +------+-------+
| |
| +------v-------+
| | Identity |
^------------+ |
| rejected +------+-------+
| |
| +------v-------+
| | Request |
| | Join |
| +------+-------+
| |
| +------v-------+
| | Imprint | Optional
^------------+ <--+Manual input
| Bad Vendor +------+-------+
| response |
| +------v-------+
| | Enroll |
^------------+ |
| Enroll +------+-------+
| Failure |
| +------v-------+
| | Being |
^------------+ Managed |
Factory +--------------+
reset
Figure 3
State descriptions for the New Entity are as follows:
1. Discover a communication channel to the "closest" Registrar.
2. Identify itself. This is done by presenting an IEEE 802.1AR
credentials to the discovered Registrar (via the Proxy) in a
(d)TLS handshake. (Although the Registrar is also authenticated
these credentials are only provisionally accepted at this time).
Pritikin, et al. Expires September 18, 2016 [Page 11]
Internet-Draft Bootstrapping Key Infrastructures March 2016
3. Requests to Join the discovered Registrar. The acceptable
imprint methods are indicated along with a nonce ensuring that
any responses can be associated with this particular
bootstrapping attempt.
4. Imprint on the Registrar. This requires verification of the
vendor service "Audit Token" or the validation of the vendor
service "Ownership Voucher". Either of these responses contains
sufficient information for the New Entity to complete
authentication of the Registrar. (The New Entity can now finish
authentication of the Registrar (d)TLS server certificate)
5. Enroll by accepting the domain specific information from the
Registrar, and by obtaining a domain certificate from the
Registrar using a standard enrollment protocol, e.g. Enrollment
over Secure Transport (EST) [RFC7030].
6. The New Entity is now a member of, and can be managed by, the
domain and will only repeat the discovery aspects of
bootstrapping if it is returned to factory default settings.
The following sections describe each of these steps in more detail.
3.1.1. Discovery
The result of discovery is logically communication with a Proxy
instead of a Domain Registrar but in such a case the proxy
facilitates communication with the actual Domain Registrar in a
manner that is transparent to the New Entity. Therefore or clarity a
Proxy is always assumed.
To discover the Domain Bootstrap Server the New Entity performs the
following actions in this order:
a. MUST: Obtains a local address using either IPv4 or IPv6 methods
as described in [RFC4862] IPv6 Stateless Address
AutoConfiguration or [RFC3927] Dynamic Configuration of IPv4
Link-Local Addresses.
b. MAY: Performs DNS-based Service Discovery [RFC6763] over
Multicast DNS [RFC6762] searching for the service
"_bootstrapks._tcp.local."
c. SHOULD: Listen for an unsolicited broadcast response as described
in [RFC6762]. This allows devices to avoid announcing their
presence via mDNS broadcasts and instead silently join a network
by watching for periodic unsolicited broadcast responses.
Pritikin, et al. Expires September 18, 2016 [Page 12]
Internet-Draft Bootstrapping Key Infrastructures March 2016
d. MAY: Performs DNS-based Service Discovery [RFC6763] over normal
DNS operations. In this case the domain is known so the service
searched for is "_bootstrapks._tcp.example.com".
e. MAY: If no local bootstrapks service is located using the DNS-
based Service Discovery methods the New Entity contacts a well
known vendor provided bootstrapping server by performing a DNS
lookup using a well known URI such as "bootstrapks.vendor-
example.com".
Once a Registrar is discovered (technically a communication channel
through a Proxy) the New Entity communicates with the Registrar using
the bootstrapping protocol defined in Section 5. The current DNS
services returned during each query is maintained until bootstrapping
is completed. If bootstrapping fails and the New Entity returns to
the Discovery state it picks up where it left off and continues
attempting bootstrapping. For example if the first Multicast DNS
_bootstrapks._tcp.local response doesn't work then the second and
third responses are tried. If these fail the New Entity moves on to
normal DNS-based Service Discovery.
Once all discovered services are attempted the device SHOULD return
to Multicast DNS and keep trying. The New Entity may prioritize
selection order as appropriate for the anticipated environment.
[[EDNOTE: An appropriate backoff or rate limiting strategy should be
defined here such that the device doesn't flood the local network
with queries. If the device were to eventually give up -- or at
least have too long between attempts -- a power cycle would restart
the backoff mechanism.]]
3.1.2. Identity
The New Entity identifies itself during the communication protocol
handshake. If the client identity is rejected the New Entity repeats
the Discovery process using the next proxy or discovery method
available.
The bootstrapping protocol server is not authenticated. Thus this
connection is provisional and all data received is untrusted until
sufficiently validated even though it is over a (D)TLS connection.
This is aligned with the existing provisional mode of EST [RFC7030]
during s4.1.1 "Bootstrap Distribution of CA Certificates".
All security associations established are between the new device and
the Bootstrapping server regardless of proxy operations.
Pritikin, et al. Expires September 18, 2016 [Page 13]
Internet-Draft Bootstrapping Key Infrastructures March 2016
3.1.3. Request Join
The New Entity POSTs a request to join the domain to the
Bootstrapping server. This request contains a New Entity generated
nonce and informs the Bootstrapping server which imprint methods the
New Entity will accept.
As indicated in EST [RFC7030] the bootstrapping server MAY redirect
the client to an alternate server. This is most useful in the case
where the New Entity has resorted to a well known vendor URI and is
communicating with the vendor's Registrar directly. In this case the
New Entity has authenticated the Registrar using the local Implicit
Trust Anchor database and can therefore treat the redirect URI as a
trusted URI which can also be validated using the Implicit Trust
Anchor database. Since client authentication occurs during the TLS
handshake the bootstrapping server has sufficient information to
apply appropriate policy concerning which server to redirect to.
The nonce ensures the New Entity can verify that responses are
specific to this bootstrapping attempt. This minimizes the use of
global time and provides a substantial benefit for devices without a
valid clock.
3.1.4. Imprint
The domain trust anchor is received by the New Entity during the
bootstrapping protocol methods in the form of either an Audit Token
containing the domainID or an explicit ownership voucher. The goal
of the imprint state is to securely obtain a copy of this trust
anchor without involving human interaction.
The enrollment protocol EST [RFC7030] details a set of non-autonomic
bootstrapping methods such as:
o using the Implicit Trust Anchor database (not an autonomic
solution because the URL must be securely distributed),
o engaging a human user to authorize the CA certificate using out-
of-band data (not an autonomic solution because the human user is
involved),
o using a configured Explicit TA database (not an autonomic solution
because the distribution of an explicit TA database is not
autonomic),
o and using a Certificate-Less TLS mutual authentication method (not
an autonomic solution because the distribution of symmetric key
material is not autonomic).
Pritikin, et al. Expires September 18, 2016 [Page 14]
Internet-Draft Bootstrapping Key Infrastructures March 2016
This document describes additional autonomic methods:
MASA audit token Audit tokens are obtained by the Registrar from the
MASA service and presented to the New Entity for validation.
These indicate to the New Entity that joining the domain has been
logged by a trusted logging server.
Ownership Voucher Ownership Vouchers are obtained by the Registrar
from the MASA service and explicitly indicate the fully qualified
domain name of the domain the new entity currently belongs to.
The Ownership Voucher is defined in [I-D.ietf-netconf-zerotouch].
Since client authentication occurs during the TLS handshake the
bootstrapping server has sufficient information to apply appropriate
policy concerning which method to use.
An arbitrary basic configuration information package that is signed
by the domain can be delivered alongside the Audit Token or ownership
validation. This information is signed by the domain private keys
and is a one time delivery containing information such as which
enrollment server to communicate with and which management system to
communicate with. It is intended as a limited basic configuration
for these purposes and is not intended to deliver entire final
configuration to the device.
If the autonomic methods fail the New Entity returns to discovery
state and attempts bootstrapping with the next available discovered
Registrar.
3.1.5. Enrollment
As the final step of bootstrapping a Registrar helps to issue a
domain specific credential to the New Entity. For simplicity in this
document, a Registrar primarily facilitates issuing a credential by
acting as an RFC5280 Registration Authority for the Domain
Certification Authority.
Enrollment proceeds as described in Enrollment over Secure Transport
(EST) [RFC7030]. The New Entity contacts the Registrar using EST as
indicated:
o The New Entity is authenticated using the IEEE 802.1AR
credentials.
o The EST section 4.1.3 CA Certificates Response is verified using
either the Audit Token which provided the domain identity -or-
Pritikin, et al. Expires September 18, 2016 [Page 15]
Internet-Draft Bootstrapping Key Infrastructures March 2016
o The EST server is authenticated by using the Ownership Voucher
indicated fully qualified domain name to build the EST URI such
that EST section 4.1.1 bootstrapping using the New Entity implicit
Trust Anchor database can be used.
3.1.6. Being Managed
Functionality to provide generic "configuration" information is
supported. The parsing of this data and any subsequent use of the
data, for example communications with a Network Management System is
out of scope but is expected to occur after bootstrapping enrollment
is complete. This ensures that all communications with management
systems which can divulge local security information (e.g. network
topology or raw key material) is secured using the local credentials
issued during enrollment.
The New Entity uses bootstrapping to join only one domain.
Management by multiple domains is out-of-scope of bootstrapping.
After the device has successfully joined a domain and is being
managed it is plausible that the domain can insert credentials for
other domains depending on the device capabilities.
See Section 3.5.
3.2. Behavior of a Proxy
The role of the Proxy is to facilitate communications. The Proxy
forwards packets between the New Entity and the Registrar that has
been configured on the Proxy. The Proxy does not terminate the
(d)TLS handshake.
In order to permit the proxy functionality to be implemented on the
maximum variety of devices the chosen mechanism SHOULD use the
minimum amount of state on the proxy device. While many devices in
the ANIMA target space will be rather large routers, the proxy
function is likely to be implemented in the control plane CPU such a
device, with available capabilities for the proxy function similar to
many class 2 IoT devices.
The document [I-D.richardson-anima-state-for-joinrouter] provides a
more extensive analysis of the alternative proxy methods.
3.2.1. CoAP connection to Registrar
The proxy MUST implement an IPIP (protocol 41) encapsulation function
for CoAP traffic to the configured UDP port on the registrar. The
proxy does not terminate the CoAP DTLS connection. [[EDNOTE: The
choice of CoAP as the mandatory to implement protocol rather than
Pritikin, et al. Expires September 18, 2016 [Page 16]
Internet-Draft Bootstrapping Key Infrastructures March 2016
HTTP maximizes code reuse on the smallest of devices. Unfortunately
this means this document will have to include the EST over CoAP
details as additional sections. The alternative is to make 'HTTPS
proxy' method the mandatory to implement and provide a less friendly
environment for the smallest of devices. This is a decision we'll
have to see addressed by the broader team.]]
As a result of the Proxy Discovery process in section Section 3.1.1,
the port number exposed by the proxy does not need to be well known,
or require an IANA allocation. The address and port of the Registrar
will be discovered by the GRASP protocol inside the ACP. For the
IPIP encapsulation methods, the port announced by the Proxy MUST be
the same as on the registrar.
The IPIP encapsulation allows the proxy to forward traffic which is
otherwise not to be forwarded, as the traffic between New Node and
Proxy use IPv6 Link Local addresses.
If the Proxy device has more than one interface on which it offers
the proxy function, then it must select a unique IP address per
interface in order so that the proxy can stateless return the reply
packets to the correct link.
3.2.2. HTTPS proxy connection to Registrar
The proxy SHOULD also provide one of: an IPIP encapsulation of HTTP
traffic on TCP port TBD to the registrar, an HTTP proxy which accepts
URLs that reach the Registrar, or a TCP circuit proxy that connects
the New Node to the Registrar.
In order to make the HTTP choice above transparent to the New Node,
the New Node will always initiate an HTTP connection, and will always
send an appropriate CONNECT message to initiate an HTTPS connection
to the registrar. [[EDNOTE: The CONNECT syntax is that the New
Entity specifies the Registrar server in the CONNECT line. See
RFC7231 s4.3.6. We wish the Proxy to override any value with the
locally known-to-the-proxy Registrar address.]]
When the Proxy provides a circuit proxy to the Registrar the
Registrar MUST accept HTTP connections, and be willing to perform an
HTTP proxy (CONNECT) operation to itself, and then initiate HTTPS.
When the Proxy provides a stateless IPIP encapsulation to the
Registrar, then the Registrar will have to perform IPIP
decapsulation, remembering the originating outer IPIP source address
in order to qualify the inner link-local address. Being able to
connect a TCP (HTTP) or UDP (CoAP) socket to a link-local address
with an encapsulated IPIP header requires API extensions beyond
Pritikin, et al. Expires September 18, 2016 [Page 17]
Internet-Draft Bootstrapping Key Infrastructures March 2016
[RFC3542] for UDP use, and requires a form of connection latching
(see section 4.1 of [RFC5386] and all of [RFC5660], except that a
simple IPIP tunnel is used rather than an IPsec tunnel).
3.3. Behavior of the Registrar (Bootstrap Server)
Once a Registrar is established it listens for new entities and
determines if they can join the domain. The registrar delivers any
necessary authorization information to the new device and facilitates
enrollment with the domain PKI.
Registrar behavior is as follows:
Contacted by New Entity
+
|
+-------v----------+
| Entity | fail?
| Authentication +---------+
+-------+----------+ |
| |
+-------v----------+ |
| Entity | fail? |
| Authorization +--------->
+-------+----------+ |
| |
+-------v----------+ |
| Claiming the | fail? |
| Entity +--------->
+-------+----------+ |
| |
+-------v----------+ |
| Log Verification | fail? |
| +--------->
+-------+----------+ |
| |
+-------v----------+ +----v-------+
| Forward | | |
| Audit | | Reject |
| token + config | | Device |
| to the Entity | | |
+------------------+ +------------+
Figure 4