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2 NETCONF Working Group K. Watsen
3 Internet-Draft Juniper Networks
4 Intended status: Standards Track G. Wu
5 Expires: March 24, 2019 Cisco Systems
6 September 20, 2018
8 YANG Groupings for SSH Clients and SSH Servers
9 draft-ietf-netconf-ssh-client-server-07
11 Abstract
13 This document defines three YANG modules: the first defines groupings
14 for a generic SSH client, the second defines groupings for a generic
15 SSH server, and the third defines common identities and groupings
16 used by both the client and the server. It is intended that these
17 groupings will be used by applications using the SSH protocol.
19 Editorial Note (To be removed by RFC Editor)
21 This draft contains many placeholder values that need to be replaced
22 with finalized values at the time of publication. This note
23 summarizes all of the substitutions that are needed. No other RFC
24 Editor instructions are specified elsewhere in this document.
26 This document contains references to other drafts in progress, both
27 in the Normative References section, as well as in body text
28 throughout. Please update the following references to reflect their
29 final RFC assignments:
31 o I-D.ietf-netconf-trust-anchors
33 o I-D.ietf-netconf-keystore
35 Artwork in this document contains shorthand references to drafts in
36 progress. Please apply the following replacements:
38 o "XXXX" --> the assigned RFC value for this draft
40 o "YYYY" --> the assigned RFC value for I-D.ietf-netconf-trust-
41 anchors
43 o "ZZZZ" --> the assigned RFC value for I-D.ietf-netconf-keystore
45 Artwork in this document contains placeholder values for the date of
46 publication of this draft. Please apply the following replacement:
48 o "2018-09-20" --> the publication date of this draft
49 The following Appendix section is to be removed prior to publication:
51 o Appendix A. Change Log
53 Status of This Memo
55 This Internet-Draft is submitted in full conformance with the
56 provisions of BCP 78 and BCP 79.
58 Internet-Drafts are working documents of the Internet Engineering
59 Task Force (IETF). Note that other groups may also distribute
60 working documents as Internet-Drafts. The list of current Internet-
61 Drafts is at https://datatracker.ietf.org/drafts/current/.
63 Internet-Drafts are draft documents valid for a maximum of six months
64 and may be updated, replaced, or obsoleted by other documents at any
65 time. It is inappropriate to use Internet-Drafts as reference
66 material or to cite them other than as "work in progress."
68 This Internet-Draft will expire on March 24, 2019.
70 Copyright Notice
72 Copyright (c) 2018 IETF Trust and the persons identified as the
73 document authors. All rights reserved.
75 This document is subject to BCP 78 and the IETF Trust's Legal
76 Provisions Relating to IETF Documents
77 (https://trustee.ietf.org/license-info) in effect on the date of
78 publication of this document. Please review these documents
79 carefully, as they describe your rights and restrictions with respect
80 to this document. Code Components extracted from this document must
81 include Simplified BSD License text as described in Section 4.e of
82 the Trust Legal Provisions and are provided without warranty as
83 described in the Simplified BSD License.
85 Table of Contents
87 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
88 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
89 3. The SSH Client Model . . . . . . . . . . . . . . . . . . . . 4
90 3.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 4
91 3.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 5
92 3.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 8
93 4. The SSH Server Model . . . . . . . . . . . . . . . . . . . . 12
94 4.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 12
95 4.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 12
96 4.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 16
98 5. The SSH Common Model . . . . . . . . . . . . . . . . . . . . 20
99 5.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 20
100 5.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 21
101 5.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 21
102 6. Security Considerations . . . . . . . . . . . . . . . . . . . 31
103 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32
104 7.1. The IETF XML Registry . . . . . . . . . . . . . . . . . . 32
105 7.2. The YANG Module Names Registry . . . . . . . . . . . . . 32
106 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 33
107 8.1. Normative References . . . . . . . . . . . . . . . . . . 33
108 8.2. Informative References . . . . . . . . . . . . . . . . . 34
109 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 36
110 A.1. 00 to 01 . . . . . . . . . . . . . . . . . . . . . . . . 36
111 A.2. 01 to 02 . . . . . . . . . . . . . . . . . . . . . . . . 36
112 A.3. 02 to 03 . . . . . . . . . . . . . . . . . . . . . . . . 36
113 A.4. 03 to 04 . . . . . . . . . . . . . . . . . . . . . . . . 36
114 A.5. 04 to 05 . . . . . . . . . . . . . . . . . . . . . . . . 37
115 A.6. 05 to 06 . . . . . . . . . . . . . . . . . . . . . . . . 37
116 A.7. 06 to 07 . . . . . . . . . . . . . . . . . . . . . . . . 37
117 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 37
118 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37
120 1. Introduction
122 This document defines three YANG 1.1 [RFC7950] modules: the first
123 defines a grouping for a generic SSH client, the second defines a
124 grouping for a generic SSH server, and the third defines identities
125 and groupings common to both the client and the server. It is
126 intended that these groupings will be used by applications using the
127 SSH protocol [RFC4252], [RFC4253], and [RFC4254]. For instance,
128 these groupings could be used to help define the data model for an
129 OpenSSH [OPENSSH] server or a NETCONF over SSH [RFC6242] based
130 server.
132 The client and server YANG modules in this document each define one
133 grouping, which is focused on just SSH-specific configuration, and
134 specifically avoids any transport-level configuration, such as what
135 ports to listen on or connect to. This affords applications the
136 opportunity to define their own strategy for how the underlying TCP
137 connection is established. For instance, applications supporting
138 NETCONF Call Home [RFC8071] could use the "ssh-server-grouping"
139 grouping for the SSH parts it provides, while adding data nodes for
140 the TCP-level call-home configuration.
142 The modules defined in this document uses groupings defined in
143 [I-D.ietf-netconf-keystore] enabling keys to be either locally
144 defined or a reference to globally configured values.
146 The modules defined in this document optionally support [RFC6187]
147 enabling X.509v3 certificate based host keys and public keys.
149 2. Terminology
151 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
152 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
153 "OPTIONAL" in this document are to be interpreted as described in BCP
154 14 [RFC2119] [RFC8174] when, and only when, they appear in all
155 capitals, as shown here.
157 3. The SSH Client Model
159 3.1. Tree Diagram
161 This section provides a tree diagram [RFC8340] for the "ietf-ssh-
162 client" module that does not have groupings expanded.
164 module: ietf-ssh-client
166 grouping transport-params-grouping
167 +-- transport-params {ssh-client-transport-params-config}?
168 +---u transport-params-grouping
169 grouping client-identity-grouping
170 +-- client-identity
171 +-- username? string
172 +-- (auth-type)
173 +--:(password)
174 | +-- password? string
175 +--:(public-key)
176 | +-- public-key
177 | +---u client-identity-grouping
178 +--:(certificate)
179 +-- certificate {sshcmn:ssh-x509-certs}?
180 +---u client-identity-grouping
181 grouping ssh-client-grouping
182 +---u client-identity-grouping
183 +---u server-auth-grouping
184 +---u transport-params-grouping
185 grouping server-auth-grouping
186 +-- server-auth
187 +-- pinned-ssh-host-keys? ta:pinned-host-keys-ref
188 | {ta:ssh-host-keys}?
189 +-- pinned-ca-certs? ta:pinned-certificates-ref
190 | {sshcmn:ssh-x509-certs,ta:x509-certificates}?
191 +-- pinned-server-certs? ta:pinned-certificates-ref
192 {sshcmn:ssh-x509-certs,ta:x509-certificates}?
194 3.2. Example Usage
196 This section presents two examples showing the ssh-client-grouping
197 populated with some data. These examples are effectively the same
198 except the first configures the client identity using a local key
199 while the second uses a key configured in a keystore. Both examples
200 are consistent with the examples presented in Section 3 of
201 [I-D.ietf-netconf-trust-anchors] and Section 3.2 of
202 [I-D.ietf-netconf-keystore].
204 The following example configures the client identity using a local
205 key:
207 [Note: '\' line wrapping for formatting only]
209
213
214
215 foobar
216
217 ct:rsa1024
219 base64encodedvalue==
220 base64encodedvalue==
221
222
224
225
226 explicitly-trusted-ssh-host-keys
228
230
231
232 algs:ssh-rsa
233
234
235
236 algs:diffie-hellman-group-exchange-sha256
237
238
239
240 algs:aes256-ctr
241 algs:aes192-ctr
242 algs:aes128-ctr
243 algs:aes256-cbc
244 algs:aes192-cbc
245 algs:aes128-cbc
246
247
248 algs:hmac-sha2-256
249 algs:hmac-sha2-512
250
251
253
254 The following example configures the client identity using a key from
255 the keystore:
257 [Note: '\' line wrapping for formatting only]
259
263
264
265 foobar
266
267 ex-rsa-key
268
269
271
272
273 explicitly-trusted-ssh-host-keys
275
277
278
279 algs:ssh-rsa
280
281
282
283 algs:diffie-hellman-group-exchange-sha256
284
285
286
287 algs:aes256-ctr
288 algs:aes192-ctr
289 algs:aes128-ctr
290 algs:aes256-cbc
291 algs:aes192-cbc
292 algs:aes128-cbc
293
294
295 algs:hmac-sha2-256
296 algs:hmac-sha2-512
297
298
300
302 3.3. YANG Module
304 This YANG module has normative references to
305 [I-D.ietf-netconf-trust-anchors], and [I-D.ietf-netconf-keystore].
307 file "ietf-ssh-client@2018-09-20.yang"
308 module ietf-ssh-client {
309 yang-version 1.1;
311 namespace "urn:ietf:params:xml:ns:yang:ietf-ssh-client";
312 prefix "sshc";
314 import ietf-ssh-common {
315 prefix sshcmn;
316 revision-date 2018-09-20; // stable grouping definitions
317 reference
318 "RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
319 }
321 import ietf-trust-anchors {
322 prefix ta;
323 reference
324 "RFC YYYY: YANG Data Model for Global Trust Anchors";
325 }
327 import ietf-keystore {
328 prefix ks;
329 reference
330 "RFC ZZZZ:
331 YANG Data Model for a Centralized Keystore Mechanism";
332 }
334 organization
335 "IETF NETCONF (Network Configuration) Working Group";
337 contact
338 "WG Web:
339 WG List:
341 Author: Kent Watsen
342
344 Author: Gary Wu
345 ";
347 description
348 "This module defines a reusable grouping for a SSH client that
349 can be used as a basis for specific SSH client instances.
351 Copyright (c) 2018 IETF Trust and the persons identified as
352 authors of the code. All rights reserved.
354 Redistribution and use in source and binary forms, with or
355 without modification, is permitted pursuant to, and subject
356 to the license terms contained in, the Simplified BSD
357 License set forth in Section 4.c of the IETF Trust's
358 Legal Provisions Relating to IETF Documents
359 (http://trustee.ietf.org/license-info).
361 This version of this YANG module is part of RFC XXXX; see
362 the RFC itself for full legal notices.";
364 revision "2018-09-20" {
365 description
366 "Initial version";
367 reference
368 "RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
369 }
371 // features
373 feature ssh-client-transport-params-config {
374 description
375 "SSH transport layer parameters are configurable on an SSH
376 client.";
377 }
379 // groupings
381 grouping ssh-client-grouping {
382 description
383 "A reusable grouping for configuring a SSH client without
384 any consideration for how an underlying TCP session is
385 established.";
386 uses client-identity-grouping;
387 uses server-auth-grouping;
388 uses transport-params-grouping;
389 }
391 grouping client-identity-grouping {
392 description
393 "A reusable grouping for configuring a SSH client identity.";
394 container client-identity {
395 description
396 "The credentials used by the client to authenticate to
397 the SSH server.";
398 leaf username {
399 type string;
400 description
401 "The username of this user. This will be the username
402 used, for instance, to log into an SSH server.";
403 }
404 choice auth-type {
405 mandatory true;
406 description
407 "The authentication type.";
408 leaf password {
409 type string;
410 description
411 "A password to be used for client authentication.";
412 }
413 container public-key {
414 uses ks:local-or-keystore-asymmetric-key-grouping;
415 description
416 "A locally-defined or referenced asymmetric key pair
417 to be used for client authentication.";
418 reference
419 "RFC ZZZZ:
420 YANG Data Model for a Centralized Keystore Mechanism";
421 }
422 container certificate {
423 if-feature sshcmn:ssh-x509-certs;
424 uses ks:local-or-keystore-end-entity-certificate-grouping;
425 description
426 "A locally-defined or referenced certificate
427 to be used for client authentication.";
428 reference
429 "RFC ZZZZ
430 YANG Data Model for a Centralized Keystore Mechanism";
431 }
432 } // end auth-type
433 } // end client-identity
434 } // end client-identity-grouping
436 grouping server-auth-grouping {
437 description
438 "A reusable grouping for configuring SSH server
439 authentication.";
440 container server-auth {
441 must 'pinned-ssh-host-keys or pinned-ca-certs or '
442 + 'pinned-server-certs';
443 description
444 "Trusted server identities.";
446 leaf pinned-ssh-host-keys {
447 if-feature "ta:ssh-host-keys";
448 type ta:pinned-host-keys-ref;
449 description
450 "A reference to a list of SSH host keys used by the
451 SSH client to authenticate SSH server host keys.
452 A server host key is authenticated if it is an exact
453 match to a configured SSH host key.";
454 reference
455 "RFC YYYY: YANG Data Model for Global Trust Anchors";
456 }
457 leaf pinned-ca-certs {
458 if-feature sshcmn:ssh-x509-certs;
459 if-feature "ta:x509-certificates";
460 type ta:pinned-certificates-ref;
461 description
462 "A reference to a list of certificate authority (CA)
463 certificates used by the SSH client to authenticate
464 SSH server certificates. A server certificate is
465 authenticated if it has a valid chain of trust to
466 a configured CA certificate.";
467 reference
468 "RFC YYYY: YANG Data Model for Global Trust Anchors";
469 }
471 leaf pinned-server-certs {
472 if-feature sshcmn:ssh-x509-certs;
473 if-feature "ta:x509-certificates";
474 type ta:pinned-certificates-ref;
475 description
476 "A reference to a list of server certificates used by
477 the SSH client to authenticate SSH server certificates.
478 A server certificate is authenticated if it is an
479 exact match to a configured server certificate.";
480 reference
481 "RFC YYYY: YANG Data Model for Global Trust Anchors";
482 }
483 } // end server-auth
484 } // end server-auth-grouping
486 grouping transport-params-grouping {
487 description
488 "A reusable grouping for configuring a SSH transport
489 parameters.";
490 container transport-params {
491 if-feature ssh-client-transport-params-config;
492 description
493 "Configurable parameters of the SSH transport layer.";
495 uses sshcmn:transport-params-grouping;
496 }
497 } // end transport-params-grouping
499 }
500
502 4. The SSH Server Model
504 4.1. Tree Diagram
506 This section provides a tree diagram [RFC8340] for the "ietf-ssh-
507 server" module that does not have groupings expanded.
509 module: ietf-ssh-server
511 grouping transport-params-grouping
512 +-- transport-params {ssh-server-transport-params-config}?
513 +---u transport-params-grouping
514 grouping client-auth-grouping
515 +-- client-cert-auth {sshcmn:ssh-x509-certs}?
516 +-- pinned-ca-certs? ta:pinned-certificates-ref
517 | {ta:x509-certificates}?
518 +-- pinned-client-certs? ta:pinned-certificates-ref
519 {ta:x509-certificates}?
520 grouping server-identity-grouping
521 +-- server-identity
522 +-- host-key* [name]
523 +-- name? string
524 +-- (host-key-type)
525 +--:(public-key)
526 | +-- public-key
527 | +---u server-identity-grouping
528 +--:(certificate)
529 +-- certificate {sshcmn:ssh-x509-certs}?
530 +---u server-identity-grouping
531 grouping ssh-server-grouping
532 +---u server-identity-grouping
533 +---u client-auth-grouping
534 +---u transport-params-grouping
536 4.2. Example Usage
538 This section presents two examples showing the ssh-server-grouping
539 populated with some data. These examples are effectively the same
540 except the first configures the server identity using a local key
541 while the second uses a key configured in a keystore. Both examples
542 are consistent with the examples presented in Section 3 of
544 [I-D.ietf-netconf-trust-anchors] and Section 3.2 of
545 [I-D.ietf-netconf-keystore].
547 The following example configures the server identity using a local
548 key:
550 [Note: '\' line wrapping for formatting only]
552
555
556
557
558 deployment-specific-certificate
559
560 ct:rsa1024
562 base64encodedvalue==
563 base64encodedvalue==
564
565
566
568
569
570 explicitly-trusted-client-ca-certs
572 explicitly-trusted-client-certs
574
576
577
578 algs:ssh-rsa
579
580
581
582 algs:diffie-hellman-group-exchange-sha256
583
584
585
586 algs:aes256-ctr
587 algs:aes192-ctr
588 algs:aes128-ctr
589 algs:aes256-cbc
590 algs:aes192-cbc
591 algs:aes128-cbc
592
593
594 algs:hmac-sha2-256
595 algs:hmac-sha2-512
596
597
599
601 The following example configures the server identity using a key from
602 the keystore:
604 [Note: '\' line wrapping for formatting only]
606
609
610
611
612 deployment-specific-certificate
613
614 ex-rsa-key
615
616
617
619
620
621 explicitly-trusted-client-ca-certs
623 explicitly-trusted-client-certs
625
627
628
629 algs:ssh-rsa
630
631
632
633 algs:diffie-hellman-group-exchange-sha256
634
635
636
637 algs:aes256-ctr
638 algs:aes192-ctr
639 algs:aes128-ctr
640 algs:aes256-cbc
641 algs:aes192-cbc
642 algs:aes128-cbc
643
644
645 algs:hmac-sha2-256
646 algs:hmac-sha2-512
647
648
650
652 4.3. YANG Module
654 This YANG module has normative references to
655 [I-D.ietf-netconf-trust-anchors] and [I-D.ietf-netconf-keystore] and
656 informative references to [RFC4253] and [RFC7317].
658 file "ietf-ssh-server@2018-09-20.yang"
659 module ietf-ssh-server {
660 yang-version 1.1;
662 namespace "urn:ietf:params:xml:ns:yang:ietf-ssh-server";
663 prefix "sshs";
665 import ietf-ssh-common {
666 prefix sshcmn;
667 revision-date 2018-09-20; // stable grouping definitions
668 reference
669 "RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
670 }
672 import ietf-trust-anchors {
673 prefix ta;
674 reference
675 "RFC YYYY: YANG Data Model for Global Trust Anchors";
676 }
678 import ietf-keystore {
679 prefix ks;
680 reference
681 "RFC ZZZZ:
682 YANG Data Model for a Centralized Keystore Mechanism";
683 }
685 organization
686 "IETF NETCONF (Network Configuration) Working Group";
688 contact
689 "WG Web:
690 WG List:
692 Author: Kent Watsen
693
695 Author: Gary Wu
696 ";
698 description
699 "This module defines a reusable grouping for a SSH server that
700 can be used as a basis for specific SSH server instances.
702 Copyright (c) 2018 IETF Trust and the persons identified as
703 authors of the code. All rights reserved.
705 Redistribution and use in source and binary forms, with or
706 without modification, is permitted pursuant to, and subject
707 to the license terms contained in, the Simplified BSD
708 License set forth in Section 4.c of the IETF Trust's
709 Legal Provisions Relating to IETF Documents
710 (http://trustee.ietf.org/license-info).
712 This version of this YANG module is part of RFC XXXX; see
713 the RFC itself for full legal notices.";
715 revision "2018-09-20" {
716 description
717 "Initial version";
718 reference
719 "RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
720 }
722 // features
724 feature ssh-server-transport-params-config {
725 description
726 "SSH transport layer parameters are configurable on an SSH
727 server.";
728 }
730 // groupings
732 grouping ssh-server-grouping {
733 description
734 "A reusable grouping for configuring a SSH server without
735 any consideration for how underlying TCP sessions are
736 established.";
737 uses server-identity-grouping;
738 uses client-auth-grouping;
739 uses transport-params-grouping;
740 }
742 grouping server-identity-grouping {
743 description
744 "A reusable grouping for configuring an SSH server identity.";
745 container server-identity {
746 description
747 "The list of host-keys the SSH server will present when
748 establishing a SSH connection.";
749 list host-key {
750 key name;
751 min-elements 1;
752 ordered-by user;
753 description
754 "An ordered list of host keys the SSH server will use to
755 construct its ordered list of algorithms, when sending
756 its SSH_MSG_KEXINIT message, as defined in Section 7.1
757 of RFC 4253.";
758 reference
759 "RFC 4253: The Secure Shell (SSH) Transport Layer
760 Protocol";
761 leaf name {
762 type string;
763 description
764 "An arbitrary name for this host-key";
765 }
766 choice host-key-type {
767 mandatory true;
768 description
769 "The type of host key being specified";
770 container public-key {
771 uses ks:local-or-keystore-asymmetric-key-grouping;
772 description
773 "A locally-defined or referenced asymmetric key pair
774 to be used for the SSH server's host key.";
775 reference
776 "RFC ZZZZ: YANG Data Model for a Centralized
777 Keystore Mechanism";
778 }
779 container certificate {
780 if-feature sshcmn:ssh-x509-certs;
781 uses
782 ks:local-or-keystore-end-entity-certificate-grouping;
783 description
784 "A locally-defined or referenced end-entity
785 certificate to be used for the SSH server's
786 host key.";
787 reference
788 "RFC ZZZZ: YANG Data Model for a Centralized
789 Keystore Mechanism";
790 }
791 }
792 }
793 } // end server-identity
794 } // end server-identity-grouping
795 grouping client-auth-grouping {
796 description
797 "A reusable grouping for configuring a SSH client
798 authentication.";
799 container client-cert-auth {
800 if-feature sshcmn:ssh-x509-certs;
801 description
802 "A reference to a list of pinned certificate authority (CA)
803 certificates and a reference to a list of pinned client
804 certificates.
806 Note: password and public-key based client authentication
807 are not configured in this YANG module as they are
808 expected to be configured by the ietf-system module
809 defined in RFC 7317.";
810 reference
811 "RFC 7317: A YANG Data Model for System Management";
812 leaf pinned-ca-certs {
813 if-feature "ta:x509-certificates";
814 type ta:pinned-certificates-ref;
815 description
816 "A reference to a list of certificate authority (CA)
817 certificates used by the SSH server to authenticate
818 SSH client certificates. A client certificate is
819 authenticated if it has a valid chain of trust to
820 a configured pinned CA certificate.";
821 reference
822 "RFC YYYY: YANG Data Model for Global Trust Anchors";
823 }
824 leaf pinned-client-certs {
825 if-feature "ta:x509-certificates";
826 type ta:pinned-certificates-ref;
827 description
828 "A reference to a list of client certificates used by
829 the SSH server to authenticate SSH client certificates.
830 A clients certificate is authenticated if it is an
831 exact match to a configured pinned client certificate.";
832 reference
833 "RFC YYYY: YANG Data Model for Global Trust Anchors";
834 }
835 }
836 } // end client-auth-grouping
838 grouping transport-params-grouping {
839 description
840 "A reusable grouping for configuring a SSH transport
841 parameters.";
842 container transport-params {
843 if-feature ssh-server-transport-params-config;
844 description
845 "Configurable parameters of the SSH transport layer.";
846 uses sshcmn:transport-params-grouping;
847 }
848 } // end transport-params-grouping
850 }
851
853 5. The SSH Common Model
855 The SSH common model presented in this section contains identities
856 and groupings common to both SSH clients and SSH servers. The
857 transport-params-grouping can be used to configure the list of SSH
858 transport algorithms permitted by the SSH client or SSH server. The
859 lists of algorithms are ordered such that, if multiple algorithms are
860 permitted by the client, the algorithm that appears first in its list
861 that is also permitted by the server is used for the SSH transport
862 layer connection. The ability to restrict the the algorithms allowed
863 is provided in this grouping for SSH clients and SSH servers that are
864 capable of doing so and may serve to make SSH clients and SSH servers
865 compliant with security policies.
867 Features are defined for algorithms that are OPTIONAL or are not
868 widely supported by popular implementations. Note that the list of
869 algorithms is not exhaustive. As well, some algorithms that are
870 REQUIRED by [RFC4253] are missing, notably "ssh-dss" and "diffie-
871 hellman-group1-sha1" due to their weak security and there being
872 alternatives that are widely supported.
874 5.1. Tree Diagram
876 The following tree diagram [RFC8340] provides an overview of the data
877 model for the "ietf-ssh-common" module.
879 module: ietf-ssh-common
881 grouping transport-params-grouping
882 +-- host-key
883 | +-- host-key-alg* identityref
884 +-- key-exchange
885 | +-- key-exchange-alg* identityref
886 +-- encryption
887 | +-- encryption-alg* identityref
888 +-- mac
889 +-- mac-alg* identityref
891 5.2. Example Usage
893 This following example illustrates how the transport-params-grouping
894 appears when populated with some data.
896
899
900 algs:x509v3-rsa2048-sha256
901 algs:ssh-rsa
902
903
904
905 algs:diffie-hellman-group-exchange-sha256
906
907
908
909 algs:aes256-ctr
910 algs:aes192-ctr
911 algs:aes128-ctr
912 algs:aes256-cbc
913 algs:aes192-cbc
914 algs:aes128-cbc
915
916
917 algs:hmac-sha2-256
918 algs:hmac-sha2-512
919
920
922 5.3. YANG Module
924 This YANG module has normative references to [RFC4253], [RFC4344],
925 [RFC4419], [RFC5656], [RFC6187], and [RFC6668].
927 file "ietf-ssh-common@2018-09-20.yang"
928 module ietf-ssh-common {
929 yang-version 1.1;
931 namespace "urn:ietf:params:xml:ns:yang:ietf-ssh-common";
932 prefix "sshcmn";
934 organization
935 "IETF NETCONF (Network Configuration) Working Group";
937 contact
938 "WG Web:
939 WG List:
941 Author: Kent Watsen
942
944 Author: Gary Wu
945 ";
947 description
948 "This module defines a common features, identities, and
949 groupings for Secure Shell (SSH).
951 Copyright (c) 2018 IETF Trust and the persons identified as
952 authors of the code. All rights reserved.
954 Redistribution and use in source and binary forms, with or
955 without modification, is permitted pursuant to, and subject
956 to the license terms contained in, the Simplified BSD
957 License set forth in Section 4.c of the IETF Trust's
958 Legal Provisions Relating to IETF Documents
959 (http://trustee.ietf.org/license-info).
961 This version of this YANG module is part of RFC XXXX; see
962 the RFC itself for full legal notices.";
964 revision "2018-09-20" {
965 description
966 "Initial version";
967 reference
968 "RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
969 }
971 // features
973 feature ssh-ecc {
974 description
975 "Elliptic Curve Cryptography is supported for SSH.";
976 reference
977 "RFC 5656: Elliptic Curve Algorithm Integration in the
978 Secure Shell Transport Layer";
979 }
981 feature ssh-x509-certs {
982 description
983 "X.509v3 certificates are supported for SSH per RFC 6187.";
984 reference
985 "RFC 6187: X.509v3 Certificates for Secure Shell
986 Authentication";
988 }
990 feature ssh-dh-group-exchange {
991 description
992 "Diffie-Hellman Group Exchange is supported for SSH.";
993 reference
994 "RFC 4419: Diffie-Hellman Group Exchange for the
995 Secure Shell (SSH) Transport Layer Protocol";
996 }
998 feature ssh-ctr {
999 description
1000 "SDCTR encryption mode is supported for SSH.";
1001 reference
1002 "RFC 4344: The Secure Shell (SSH) Transport Layer
1003 Encryption Modes";
1004 }
1006 feature ssh-sha2 {
1007 description
1008 "The SHA2 family of cryptographic hash functions is
1009 supported for SSH.";
1010 reference
1011 "FIPS PUB 180-4: Secure Hash Standard (SHS)";
1012 }
1014 // identities
1016 identity public-key-alg-base {
1017 description
1018 "Base identity used to identify public key algorithms.";
1019 }
1021 identity ssh-dss {
1022 base public-key-alg-base;
1023 description
1024 "Digital Signature Algorithm using SHA-1 as the
1025 hashing algorithm.";
1026 reference
1027 "RFC 4253:
1028 The Secure Shell (SSH) Transport Layer Protocol";
1029 }
1031 identity ssh-rsa {
1032 base public-key-alg-base;
1033 description
1034 "RSASSA-PKCS1-v1_5 signature scheme using SHA-1 as the
1035 hashing algorithm.";
1037 reference
1038 "RFC 4253:
1039 The Secure Shell (SSH) Transport Layer Protocol";
1040 }
1042 identity ecdsa-sha2-nistp256 {
1043 base public-key-alg-base;
1044 if-feature "ssh-ecc and ssh-sha2";
1045 description
1046 "Elliptic Curve Digital Signature Algorithm (ECDSA) using the
1047 nistp256 curve and the SHA2 family of hashing algorithms.";
1048 reference
1049 "RFC 5656: Elliptic Curve Algorithm Integration in the
1050 Secure Shell Transport Layer";
1051 }
1053 identity ecdsa-sha2-nistp384 {
1054 base public-key-alg-base;
1055 if-feature "ssh-ecc and ssh-sha2";
1056 description
1057 "Elliptic Curve Digital Signature Algorithm (ECDSA) using the
1058 nistp384 curve and the SHA2 family of hashing algorithms.";
1059 reference
1060 "RFC 5656: Elliptic Curve Algorithm Integration in the
1061 Secure Shell Transport Layer";
1062 }
1064 identity ecdsa-sha2-nistp521 {
1065 base public-key-alg-base;
1066 if-feature "ssh-ecc and ssh-sha2";
1067 description
1068 "Elliptic Curve Digital Signature Algorithm (ECDSA) using the
1069 nistp521 curve and the SHA2 family of hashing algorithms.";
1070 reference
1071 "RFC 5656: Elliptic Curve Algorithm Integration in the
1072 Secure Shell Transport Layer";
1073 }
1075 identity x509v3-ssh-rsa {
1076 base public-key-alg-base;
1077 if-feature ssh-x509-certs;
1078 description
1079 "RSASSA-PKCS1-v1_5 signature scheme using a public key stored
1080 in an X.509v3 certificate and using SHA-1 as the hashing
1081 algorithm.";
1082 reference
1083 "RFC 6187: X.509v3 Certificates for Secure Shell
1084 Authentication";
1086 }
1088 identity x509v3-rsa2048-sha256 {
1089 base public-key-alg-base;
1090 if-feature "ssh-x509-certs and ssh-sha2";
1091 description
1092 "RSASSA-PKCS1-v1_5 signature scheme using a public key stored
1093 in an X.509v3 certificate and using SHA-256 as the hashing
1094 algorithm. RSA keys conveyed using this format MUST have a
1095 modulus of at least 2048 bits.";
1096 reference
1097 "RFC 6187: X.509v3 Certificates for Secure Shell
1098 Authentication";
1099 }
1101 identity x509v3-ecdsa-sha2-nistp256 {
1102 base public-key-alg-base;
1103 if-feature "ssh-ecc and ssh-x509-certs and ssh-sha2";
1104 description
1105 "Elliptic Curve Digital Signature Algorithm (ECDSA)
1106 using the nistp256 curve with a public key stored in
1107 an X.509v3 certificate and using the SHA2 family of
1108 hashing algorithms.";
1109 reference
1110 "RFC 6187: X.509v3 Certificates for Secure Shell
1111 Authentication";
1112 }
1114 identity x509v3-ecdsa-sha2-nistp384 {
1115 base public-key-alg-base;
1116 if-feature "ssh-ecc and ssh-x509-certs and ssh-sha2";
1117 description
1118 "Elliptic Curve Digital Signature Algorithm (ECDSA)
1119 using the nistp384 curve with a public key stored in
1120 an X.509v3 certificate and using the SHA2 family of
1121 hashing algorithms.";
1122 reference
1123 "RFC 6187: X.509v3 Certificates for Secure Shell
1124 Authentication";
1125 }
1127 identity x509v3-ecdsa-sha2-nistp521 {
1128 base public-key-alg-base;
1129 if-feature "ssh-ecc and ssh-x509-certs and ssh-sha2";
1130 description
1131 "Elliptic Curve Digital Signature Algorithm (ECDSA)
1132 using the nistp521 curve with a public key stored in
1133 an X.509v3 certificate and using the SHA2 family of
1134 hashing algorithms.";
1135 reference
1136 "RFC 6187: X.509v3 Certificates for Secure Shell
1137 Authentication";
1138 }
1140 identity key-exchange-alg-base {
1141 description
1142 "Base identity used to identify key exchange algorithms.";
1143 }
1145 identity diffie-hellman-group14-sha1 {
1146 base key-exchange-alg-base;
1147 description
1148 "Diffie-Hellman key exchange with SHA-1 as HASH and
1149 Oakley Group 14 (2048-bit MODP Group).";
1150 reference
1151 "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
1152 }
1154 identity diffie-hellman-group-exchange-sha1 {
1155 base key-exchange-alg-base;
1156 if-feature ssh-dh-group-exchange;
1157 description
1158 "Diffie-Hellman Group and Key Exchange with SHA-1 as HASH.";
1159 reference
1160 "RFC 4419: Diffie-Hellman Group Exchange for the
1161 Secure Shell (SSH) Transport Layer Protocol";
1162 }
1164 identity diffie-hellman-group-exchange-sha256 {
1165 base key-exchange-alg-base;
1166 if-feature "ssh-dh-group-exchange and ssh-sha2";
1167 description
1168 "Diffie-Hellman Group and Key Exchange with SHA-256 as HASH.";
1169 reference
1170 "RFC 4419: Diffie-Hellman Group Exchange for the
1171 Secure Shell (SSH) Transport Layer Protocol";
1172 }
1174 identity ecdh-sha2-nistp256 {
1175 base key-exchange-alg-base;
1176 if-feature "ssh-ecc and ssh-sha2";
1177 description
1178 "Elliptic Curve Diffie-Hellman (ECDH) key exchange using the
1179 nistp256 curve and the SHA2 family of hashing algorithms.";
1180 reference
1181 "RFC 5656: Elliptic Curve Algorithm Integration in the
1182 Secure Shell Transport Layer";
1183 }
1185 identity ecdh-sha2-nistp384 {
1186 base key-exchange-alg-base;
1187 if-feature "ssh-ecc and ssh-sha2";
1188 description
1189 "Elliptic Curve Diffie-Hellman (ECDH) key exchange using the
1190 nistp384 curve and the SHA2 family of hashing algorithms.";
1191 reference
1192 "RFC 5656: Elliptic Curve Algorithm Integration in the
1193 Secure Shell Transport Layer";
1194 }
1196 identity ecdh-sha2-nistp521 {
1197 base key-exchange-alg-base;
1198 if-feature "ssh-ecc and ssh-sha2";
1199 description
1200 "Elliptic Curve Diffie-Hellman (ECDH) key exchange using the
1201 nistp521 curve and the SHA2 family of hashing algorithms.";
1202 reference
1203 "RFC 5656: Elliptic Curve Algorithm Integration in the
1204 Secure Shell Transport Layer";
1205 }
1207 identity encryption-alg-base {
1208 description
1209 "Base identity used to identify encryption algorithms.";
1210 }
1212 identity triple-des-cbc {
1213 base encryption-alg-base;
1214 description
1215 "Three-key 3DES in CBC mode.";
1216 reference
1217 "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
1218 }
1220 identity aes128-cbc {
1221 base encryption-alg-base;
1222 description
1223 "AES in CBC mode, with a 128-bit key.";
1224 reference
1225 "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
1226 }
1228 identity aes192-cbc {
1229 base encryption-alg-base;
1230 description
1231 "AES in CBC mode, with a 192-bit key.";
1232 reference
1233 "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
1234 }
1236 identity aes256-cbc {
1237 base encryption-alg-base;
1238 description
1239 "AES in CBC mode, with a 256-bit key.";
1240 reference
1241 "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
1242 }
1244 identity aes128-ctr {
1245 base encryption-alg-base;
1246 if-feature ssh-ctr;
1247 description
1248 "AES in SDCTR mode, with 128-bit key.";
1249 reference
1250 "RFC 4344: The Secure Shell (SSH) Transport Layer Encryption
1251 Modes";
1252 }
1254 identity aes192-ctr {
1255 base encryption-alg-base;
1256 if-feature ssh-ctr;
1257 description
1258 "AES in SDCTR mode, with 192-bit key.";
1259 reference
1260 "RFC 4344: The Secure Shell (SSH) Transport Layer Encryption
1261 Modes";
1262 }
1264 identity aes256-ctr {
1265 base encryption-alg-base;
1266 if-feature ssh-ctr;
1267 description
1268 "AES in SDCTR mode, with 256-bit key.";
1269 reference
1270 "RFC 4344: The Secure Shell (SSH) Transport Layer Encryption
1271 Modes";
1272 }
1274 identity mac-alg-base {
1275 description
1276 "Base identity used to identify message authentication
1277 code (MAC) algorithms.";
1279 }
1281 identity hmac-sha1 {
1282 base mac-alg-base;
1283 description
1284 "HMAC-SHA1";
1285 reference
1286 "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
1287 }
1289 identity hmac-sha2-256 {
1290 base mac-alg-base;
1291 if-feature "ssh-sha2";
1292 description
1293 "HMAC-SHA2-256";
1294 reference
1295 "RFC 6668: SHA-2 Data Integrity Verification for the
1296 Secure Shell (SSH) Transport Layer Protocol";
1297 }
1299 identity hmac-sha2-512 {
1300 base mac-alg-base;
1301 if-feature "ssh-sha2";
1302 description
1303 "HMAC-SHA2-512";
1304 reference
1305 "RFC 6668: SHA-2 Data Integrity Verification for the
1306 Secure Shell (SSH) Transport Layer Protocol";
1307 }
1309 // groupings
1311 grouping transport-params-grouping {
1312 description
1313 "A reusable grouping for SSH transport parameters.";
1314 reference
1315 "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
1316 container host-key {
1317 description
1318 "Parameters regarding host key.";
1319 leaf-list host-key-alg {
1320 type identityref {
1321 base public-key-alg-base;
1322 }
1323 ordered-by user;
1324 description
1325 "Acceptable host key algorithms in order of descending
1326 preference.
1328 If this leaf-list is not configured (has zero elements)
1329 the acceptable host key algorithms are implementation-
1330 defined.";
1331 }
1332 }
1333 container key-exchange {
1334 description
1335 "Parameters regarding key exchange.";
1336 leaf-list key-exchange-alg {
1337 type identityref {
1338 base key-exchange-alg-base;
1339 }
1340 ordered-by user;
1341 description
1342 "Acceptable key exchange algorithms in order of descending
1343 preference.
1345 If this leaf-list is not configured (has zero elements)
1346 the acceptable key exchange algorithms are implementation
1347 defined.";
1348 }
1349 }
1350 container encryption {
1351 description
1352 "Parameters regarding encryption.";
1353 leaf-list encryption-alg {
1354 type identityref {
1355 base encryption-alg-base;
1356 }
1357 ordered-by user;
1358 description
1359 "Acceptable encryption algorithms in order of descending
1360 preference.
1362 If this leaf-list is not configured (has zero elements)
1363 the acceptable encryption algorithms are implementation
1364 defined.";
1365 }
1366 }
1367 container mac {
1368 description
1369 "Parameters regarding message authentication code (MAC).";
1370 leaf-list mac-alg {
1371 type identityref {
1372 base mac-alg-base;
1373 }
1374 ordered-by user;
1375 description
1376 "Acceptable MAC algorithms in order of descending
1377 preference.
1379 If this leaf-list is not configured (has zero elements)
1380 the acceptable MAC algorithms are implementation-
1381 defined.";
1382 }
1383 }
1385 } // transport-params-grouping
1387 }
1388
1390 6. Security Considerations
1392 The YANG modules defined in this document are designed to be accessed
1393 via YANG based management protocols, such as NETCONF [RFC6241] and
1394 RESTCONF [RFC8040]. Both of these protocols have mandatory-to-
1395 implement secure transport layers (e.g., SSH, TLS) with mutual
1396 authentication.
1398 The NETCONF access control model (NACM) [RFC8341] provides the means
1399 to restrict access for particular users to a pre-configured subset of
1400 all available protocol operations and content.
1402 Since the modules defined in this document define only groupings,
1403 these considerations are primarily for the designers of other modules
1404 that use these groupings.
1406 There are a number of data nodes defined in the YANG modules that are
1407 writable/creatable/deletable (i.e., config true, which is the
1408 default). These data nodes may be considered sensitive or vulnerable
1409 in some network environments. Write operations (e.g., edit-config)
1410 to these data nodes without proper protection can have a negative
1411 effect on network operations. These are the subtrees and data nodes
1412 and their sensitivity/vulnerability:
1414 /: The entire data tree defined by all the modules defined in this
1415 draft are sensitive to write operations. For instance, the
1416 addition or removal of references to keys, certificates,
1417 trusted anchors, etc., can dramatically alter the implemented
1418 security policy. However, no NACM annotations are applied as
1419 the data SHOULD be editable by users other than a designated
1420 'recovery session'.
1422 Some of the readable data nodes in the YANG modules may be considered
1423 sensitive or vulnerable in some network environments. It is thus
1424 important to control read access (e.g., via get, get-config, or
1425 notification) to these data nodes. These are the subtrees and data
1426 nodes and their sensitivity/vulnerability:
1428 /client-auth/password: This node in the 'ietf-ssh-client' module
1429 is additionally sensitive to read operations such that, in
1430 normal use cases, it should never be returned to a client. The
1431 only time this node should be returned is to support backup/
1432 restore type workflows. However, no NACM annotations are
1433 applied as the data SHOULD be writable by users other than a
1434 designated 'recovery session'.
1436 Some of the RPC operations in this YANG module may be considered
1437 sensitive or vulnerable in some network environments. It is thus
1438 important to control access to these operations. These are the
1439 operations and their sensitivity/vulnerability:
1441 NONE
1443 7. IANA Considerations
1445 7.1. The IETF XML Registry
1447 This document registers three URIs in the IETF XML registry
1448 [RFC3688]. Following the format in [RFC3688], the following
1449 registrations are requested:
1451 URI: urn:ietf:params:xml:ns:yang:ietf-ssh-client
1452 Registrant Contact: The NETCONF WG of the IETF.
1453 XML: N/A, the requested URI is an XML namespace.
1455 URI: urn:ietf:params:xml:ns:yang:ietf-ssh-server
1456 Registrant Contact: The NETCONF WG of the IETF.
1457 XML: N/A, the requested URI is an XML namespace.
1459 URI: urn:ietf:params:xml:ns:yang:ietf-ssh-common
1460 Registrant Contact: The NETCONF WG of the IETF.
1461 XML: N/A, the requested URI is an XML namespace.
1463 7.2. The YANG Module Names Registry
1465 This document registers three YANG modules in the YANG Module Names
1466 registry [RFC7950]. Following the format in [RFC7950], the the
1467 following registrations are requested:
1469 name: ietf-ssh-client
1470 namespace: urn:ietf:params:xml:ns:yang:ietf-ssh-client
1471 prefix: sshc
1472 reference: RFC XXXX
1474 name: ietf-ssh-server
1475 namespace: urn:ietf:params:xml:ns:yang:ietf-ssh-server
1476 prefix: sshs
1477 reference: RFC XXXX
1479 name: ietf-ssh-common
1480 namespace: urn:ietf:params:xml:ns:yang:ietf-ssh-common
1481 prefix: sshcmn
1482 reference: RFC XXXX
1484 8. References
1486 8.1. Normative References
1488 [I-D.ietf-netconf-keystore]
1489 Watsen, K., "YANG Data Model for a Centralized Keystore
1490 Mechanism", draft-ietf-netconf-keystore-06 (work in
1491 progress), September 2018.
1493 [I-D.ietf-netconf-trust-anchors]
1494 Watsen, K., "YANG Data Model for Global Trust Anchors",
1495 draft-ietf-netconf-trust-anchors-01 (work in progress),
1496 September 2018.
1498 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
1499 Requirement Levels", BCP 14, RFC 2119,
1500 DOI 10.17487/RFC2119, March 1997,
1501 .
1503 [RFC4344] Bellare, M., Kohno, T., and C. Namprempre, "The Secure
1504 Shell (SSH) Transport Layer Encryption Modes", RFC 4344,
1505 DOI 10.17487/RFC4344, January 2006,
1506 .
1508 [RFC4419] Friedl, M., Provos, N., and W. Simpson, "Diffie-Hellman
1509 Group Exchange for the Secure Shell (SSH) Transport Layer
1510 Protocol", RFC 4419, DOI 10.17487/RFC4419, March 2006,
1511 .
1513 [RFC5656] Stebila, D. and J. Green, "Elliptic Curve Algorithm
1514 Integration in the Secure Shell Transport Layer",
1515 RFC 5656, DOI 10.17487/RFC5656, December 2009,
1516 .
1518 [RFC6187] Igoe, K. and D. Stebila, "X.509v3 Certificates for Secure
1519 Shell Authentication", RFC 6187, DOI 10.17487/RFC6187,
1520 March 2011, .
1522 [RFC6668] Bider, D. and M. Baushke, "SHA-2 Data Integrity
1523 Verification for the Secure Shell (SSH) Transport Layer
1524 Protocol", RFC 6668, DOI 10.17487/RFC6668, July 2012,
1525 .
1527 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
1528 RFC 7950, DOI 10.17487/RFC7950, August 2016,
1529 .
1531 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
1532 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
1533 May 2017, .
1535 [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
1536 Access Control Model", STD 91, RFC 8341,
1537 DOI 10.17487/RFC8341, March 2018,
1538 .
1540 8.2. Informative References
1542 [OPENSSH] "OpenSSH", 2016, .
1544 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
1545 DOI 10.17487/RFC3688, January 2004,
1546 .
1548 [RFC4252] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
1549 Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
1550 January 2006, .
1552 [RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
1553 Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253,
1554 January 2006, .
1556 [RFC4254] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
1557 Connection Protocol", RFC 4254, DOI 10.17487/RFC4254,
1558 January 2006, .
1560 [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
1561 and A. Bierman, Ed., "Network Configuration Protocol
1562 (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
1563 .
1565 [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
1566 Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
1567 .
1569 [RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for
1570 System Management", RFC 7317, DOI 10.17487/RFC7317, August
1571 2014, .
1573 [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
1574 Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
1575 .
1577 [RFC8071] Watsen, K., "NETCONF Call Home and RESTCONF Call Home",
1578 RFC 8071, DOI 10.17487/RFC8071, February 2017,
1579 .
1581 [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
1582 BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
1583 .
1585 Appendix A. Change Log
1587 A.1. 00 to 01
1589 o Noted that '0.0.0.0' and '::' might have special meanings.
1591 o Renamed "keychain" to "keystore".
1593 A.2. 01 to 02
1595 o Removed the groupings 'listening-ssh-client-grouping' and
1596 'listening-ssh-server-grouping'. Now modules only contain the
1597 transport-independent groupings.
1599 o Simplified the "client-auth" part in the ietf-ssh-client module.
1600 It now inlines what it used to point to keystore for.
1602 o Added cipher suites for various algorithms into new 'ietf-ssh-
1603 common' module.
1605 A.3. 02 to 03
1607 o Removed 'RESTRICTED' enum from 'password' leaf type.
1609 o Added a 'must' statement to container 'server-auth' asserting that
1610 at least one of the various auth mechanisms must be specified.
1612 o Fixed description statement for leaf 'trusted-ca-certs'.
1614 A.4. 03 to 04
1616 o Change title to "YANG Groupings for SSH Clients and SSH Servers"
1618 o Added reference to RFC 6668
1620 o Added RFC 8174 to Requirements Language Section.
1622 o Enhanced description statement for ietf-ssh-server's "trusted-ca-
1623 certs" leaf.
1625 o Added mandatory true to ietf-ssh-client's "client-auth" 'choice'
1626 statement.
1628 o Changed the YANG prefix for module ietf-ssh-common from 'sshcom'
1629 to 'sshcmn'.
1631 o Removed the compression algorithms as they are not commonly
1632 configurable in vendors' implementations.
1634 o Updating descriptions in transport-params-grouping and the
1635 servers's usage of it.
1637 o Now tree diagrams reference ietf-netmod-yang-tree-diagrams
1639 o Updated YANG to use typedefs around leafrefs to common keystore
1640 paths
1642 o Now inlines key and certificates (no longer a leafref to keystore)
1644 A.5. 04 to 05
1646 o Merged changes from co-author.
1648 A.6. 05 to 06
1650 o Updated to use trust anchors from trust-anchors draft (was
1651 keystore draft)
1653 o Now uses new keystore grouping enabling asymmetric key to be
1654 either locally defined or a reference to the keystore.
1656 A.7. 06 to 07
1658 o factored the ssh-[client|server]-groupings into more reusable
1659 groupings.
1661 o added if-feature statements for the new "ssh-host-keys" and
1662 "x509-certificates" features defined in draft-ietf-netconf-trust-
1663 anchors.
1665 Acknowledgements
1667 The authors would like to thank for following for lively discussions
1668 on list and in the halls (ordered by last name): Andy Bierman, Martin
1669 Bjorklund, Benoit Claise, Mehmet Ersue, Balazs Kovacs, David
1670 Lamparter, Alan Luchuk, Ladislav Lhotka, Radek Krejci, Tom Petch,
1671 Juergen Schoenwaelder, Phil Shafer, Sean Turner, Michal Vasko, and
1672 Bert Wijnen.
1674 Authors' Addresses
1676 Kent Watsen
1677 Juniper Networks
1679 EMail: kwatsen@juniper.net
1680 Gary Wu
1681 Cisco Systems
1683 EMail: garywu@cisco.com