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2 NETCONF Working Group K. Watsen
3 Internet-Draft Juniper Networks
4 Intended status: Standards Track G. Wu
5 Expires: April 25, 2019 Cisco Systems
6 L. Xia
7 Huawei
8 October 22, 2018
10 YANG Groupings for SSH Clients and SSH Servers
11 draft-ietf-netconf-ssh-client-server-08
13 Abstract
15 This document defines three YANG modules: the first defines groupings
16 for a generic SSH client, the second defines groupings for a generic
17 SSH server, and the third defines common identities and groupings
18 used by both the client and the server. It is intended that these
19 groupings will be used by applications using the SSH protocol.
21 Editorial Note (To be removed by RFC Editor)
23 This draft contains many placeholder values that need to be replaced
24 with finalized values at the time of publication. This note
25 summarizes all of the substitutions that are needed. No other RFC
26 Editor instructions are specified elsewhere in this document.
28 This document contains references to other drafts in progress, both
29 in the Normative References section, as well as in body text
30 throughout. Please update the following references to reflect their
31 final RFC assignments:
33 o I-D.ietf-netconf-trust-anchors
35 o I-D.ietf-netconf-keystore
37 Artwork in this document contains shorthand references to drafts in
38 progress. Please apply the following replacements:
40 o "XXXX" --> the assigned RFC value for this draft
42 o "YYYY" --> the assigned RFC value for I-D.ietf-netconf-trust-
43 anchors
45 o "ZZZZ" --> the assigned RFC value for I-D.ietf-netconf-keystore
47 Artwork in this document contains placeholder values for the date of
48 publication of this draft. Please apply the following replacement:
50 o "2018-10-22" --> the publication date of this draft
52 The following Appendix section is to be removed prior to publication:
54 o Appendix A. Change Log
56 Status of This Memo
58 This Internet-Draft is submitted in full conformance with the
59 provisions of BCP 78 and BCP 79.
61 Internet-Drafts are working documents of the Internet Engineering
62 Task Force (IETF). Note that other groups may also distribute
63 working documents as Internet-Drafts. The list of current Internet-
64 Drafts is at https://datatracker.ietf.org/drafts/current/.
66 Internet-Drafts are draft documents valid for a maximum of six months
67 and may be updated, replaced, or obsoleted by other documents at any
68 time. It is inappropriate to use Internet-Drafts as reference
69 material or to cite them other than as "work in progress."
71 This Internet-Draft will expire on April 25, 2019.
73 Copyright Notice
75 Copyright (c) 2018 IETF Trust and the persons identified as the
76 document authors. All rights reserved.
78 This document is subject to BCP 78 and the IETF Trust's Legal
79 Provisions Relating to IETF Documents
80 (https://trustee.ietf.org/license-info) in effect on the date of
81 publication of this document. Please review these documents
82 carefully, as they describe your rights and restrictions with respect
83 to this document. Code Components extracted from this document must
84 include Simplified BSD License text as described in Section 4.e of
85 the Trust Legal Provisions and are provided without warranty as
86 described in the Simplified BSD License.
88 Table of Contents
90 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
91 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
92 3. The SSH Client Model . . . . . . . . . . . . . . . . . . . . 4
93 3.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 4
94 3.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 5
95 3.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 8
96 4. The SSH Server Model . . . . . . . . . . . . . . . . . . . . 12
97 4.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 12
98 4.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 12
99 4.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 16
100 5. The SSH Common Model . . . . . . . . . . . . . . . . . . . . 20
101 5.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 22
102 5.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 23
103 5.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 23
104 6. Security Considerations . . . . . . . . . . . . . . . . . . . 33
105 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34
106 7.1. The IETF XML Registry . . . . . . . . . . . . . . . . . . 34
107 7.2. The YANG Module Names Registry . . . . . . . . . . . . . 34
108 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 35
109 8.1. Normative References . . . . . . . . . . . . . . . . . . 35
110 8.2. Informative References . . . . . . . . . . . . . . . . . 36
111 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 38
112 A.1. 00 to 01 . . . . . . . . . . . . . . . . . . . . . . . . 38
113 A.2. 01 to 02 . . . . . . . . . . . . . . . . . . . . . . . . 38
114 A.3. 02 to 03 . . . . . . . . . . . . . . . . . . . . . . . . 38
115 A.4. 03 to 04 . . . . . . . . . . . . . . . . . . . . . . . . 38
116 A.5. 04 to 05 . . . . . . . . . . . . . . . . . . . . . . . . 39
117 A.6. 05 to 06 . . . . . . . . . . . . . . . . . . . . . . . . 39
118 A.7. 06 to 07 . . . . . . . . . . . . . . . . . . . . . . . . 39
119 A.8. 07 to 08 . . . . . . . . . . . . . . . . . . . . . . . . 39
120 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 39
121 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40
123 1. Introduction
125 This document defines three YANG 1.1 [RFC7950] modules: the first
126 defines a grouping for a generic SSH client, the second defines a
127 grouping for a generic SSH server, and the third defines identities
128 and groupings common to both the client and the server. It is
129 intended that these groupings will be used by applications using the
130 SSH protocol [RFC4252], [RFC4253], and [RFC4254]. For instance,
131 these groupings could be used to help define the data model for an
132 OpenSSH [OPENSSH] server or a NETCONF over SSH [RFC6242] based
133 server.
135 The client and server YANG modules in this document each define one
136 grouping, which is focused on just SSH-specific configuration, and
137 specifically avoids any transport-level configuration, such as what
138 ports to listen on or connect to. This affords applications the
139 opportunity to define their own strategy for how the underlying TCP
140 connection is established. For instance, applications supporting
141 NETCONF Call Home [RFC8071] could use the "ssh-server-grouping"
142 grouping for the SSH parts it provides, while adding data nodes for
143 the TCP-level call-home configuration.
145 The modules defined in this document uses groupings defined in
146 [I-D.ietf-netconf-keystore] enabling keys to be either locally
147 defined or a reference to globally configured values.
149 The modules defined in this document optionally support [RFC6187]
150 enabling X.509v3 certificate based host keys and public keys.
152 2. Terminology
154 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
155 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
156 "OPTIONAL" in this document are to be interpreted as described in BCP
157 14 [RFC2119] [RFC8174] when, and only when, they appear in all
158 capitals, as shown here.
160 3. The SSH Client Model
162 3.1. Tree Diagram
164 This section provides a tree diagram [RFC8340] for the "ietf-ssh-
165 client" module that does not have groupings expanded.
167 module: ietf-ssh-client
169 grouping transport-params-grouping
170 +-- transport-params {ssh-client-transport-params-config}?
171 +---u transport-params-grouping
172 grouping client-identity-grouping
173 +-- client-identity
174 +-- username? string
175 +-- (auth-type)
176 +--:(password)
177 | +-- password? string
178 +--:(public-key)
179 | +-- public-key
180 | +---u client-identity-grouping
181 +--:(certificate)
182 +-- certificate {sshcmn:ssh-x509-certs}?
183 +---u client-identity-grouping
184 grouping ssh-client-grouping
185 +---u client-identity-grouping
186 +---u server-auth-grouping
187 +---u transport-params-grouping
188 grouping server-auth-grouping
189 +-- server-auth
190 +-- pinned-ssh-host-keys? ta:pinned-host-keys-ref
191 | {ta:ssh-host-keys}?
192 +-- pinned-ca-certs? ta:pinned-certificates-ref
193 | {sshcmn:ssh-x509-certs,ta:x509-certificates}?
194 +-- pinned-server-certs? ta:pinned-certificates-ref
195 {sshcmn:ssh-x509-certs,ta:x509-certificates}?
197 3.2. Example Usage
199 This section presents two examples showing the ssh-client-grouping
200 populated with some data. These examples are effectively the same
201 except the first configures the client identity using a local key
202 while the second uses a key configured in a keystore. Both examples
203 are consistent with the examples presented in Section 3 of
204 [I-D.ietf-netconf-trust-anchors] and Section 3.2 of
205 [I-D.ietf-netconf-keystore].
207 The following example configures the client identity using a local
208 key:
210 [Note: '\' line wrapping for formatting only]
212
216
217
218 foobar
219
220 ct:rsa2048
222 base64encodedvalue==
223 base64encodedvalue==
224
225
227
228
229 explicitly-trusted-ssh-host-keys
231
233
234
235 algs:ssh-rsa
236
237
238
239 algs:diffie-hellman-group-exchange-sha256
240
241
242
243 algs:aes256-ctr
244 algs:aes192-ctr
245 algs:aes128-ctr
246 algs:aes256-cbc
247 algs:aes192-cbc
248 algs:aes128-cbc
249
250
251 algs:hmac-sha2-256
252 algs:hmac-sha2-512
253
254
256
257 The following example configures the client identity using a key from
258 the keystore:
260 [Note: '\' line wrapping for formatting only]
262
266
267
268 foobar
269
270 ex-rsa-key
271
272
274
275
276 explicitly-trusted-ssh-host-keys
278
280
281
282 algs:ssh-rsa
283
284
285
286 algs:diffie-hellman-group-exchange-sha256
287
288
289
290 algs:aes256-ctr
291 algs:aes192-ctr
292 algs:aes128-ctr
293 algs:aes256-cbc
294 algs:aes192-cbc
295 algs:aes128-cbc
296
297
298 algs:hmac-sha2-256
299 algs:hmac-sha2-512
300
301
303
305 3.3. YANG Module
307 This YANG module has normative references to
308 [I-D.ietf-netconf-trust-anchors], and [I-D.ietf-netconf-keystore].
310 file "ietf-ssh-client@2018-10-22.yang"
311 module ietf-ssh-client {
312 yang-version 1.1;
314 namespace "urn:ietf:params:xml:ns:yang:ietf-ssh-client";
315 prefix "sshc";
317 import ietf-ssh-common {
318 prefix sshcmn;
319 revision-date 2018-10-22; // stable grouping definitions
320 reference
321 "RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
322 }
324 import ietf-trust-anchors {
325 prefix ta;
326 reference
327 "RFC YYYY: YANG Data Model for Global Trust Anchors";
328 }
330 import ietf-keystore {
331 prefix ks;
332 reference
333 "RFC ZZZZ:
334 YANG Data Model for a Centralized Keystore Mechanism";
335 }
337 organization
338 "IETF NETCONF (Network Configuration) Working Group";
340 contact
341 "WG Web:
342 WG List:
344 Author: Kent Watsen
345
347 Author: Gary Wu
348 ";
350 description
351 "This module defines a reusable grouping for a SSH client that
352 can be used as a basis for specific SSH client instances.
354 Copyright (c) 2018 IETF Trust and the persons identified as
355 authors of the code. All rights reserved.
357 Redistribution and use in source and binary forms, with or
358 without modification, is permitted pursuant to, and subject
359 to the license terms contained in, the Simplified BSD
360 License set forth in Section 4.c of the IETF Trust's
361 Legal Provisions Relating to IETF Documents
362 (http://trustee.ietf.org/license-info).
364 This version of this YANG module is part of RFC XXXX; see
365 the RFC itself for full legal notices.";
367 revision "2018-10-22" {
368 description
369 "Initial version";
370 reference
371 "RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
372 }
374 // features
376 feature ssh-client-transport-params-config {
377 description
378 "SSH transport layer parameters are configurable on an SSH
379 client.";
380 }
382 // groupings
384 grouping ssh-client-grouping {
385 description
386 "A reusable grouping for configuring a SSH client without
387 any consideration for how an underlying TCP session is
388 established.";
389 uses client-identity-grouping;
390 uses server-auth-grouping;
391 uses transport-params-grouping;
392 }
394 grouping client-identity-grouping {
395 description
396 "A reusable grouping for configuring a SSH client identity.";
397 container client-identity {
398 description
399 "The credentials used by the client to authenticate to
400 the SSH server.";
401 leaf username {
402 type string;
403 description
404 "The username of this user. This will be the username
405 used, for instance, to log into an SSH server.";
406 }
407 choice auth-type {
408 mandatory true;
409 description
410 "The authentication type.";
411 leaf password {
412 type string;
413 description
414 "A password to be used for client authentication.";
415 }
416 container public-key {
417 uses ks:local-or-keystore-asymmetric-key-grouping;
418 description
419 "A locally-defined or referenced asymmetric key pair
420 to be used for client authentication.";
421 reference
422 "RFC ZZZZ:
423 YANG Data Model for a Centralized Keystore Mechanism";
424 }
425 container certificate {
426 if-feature sshcmn:ssh-x509-certs;
427 uses ks:local-or-keystore-end-entity-cert-with-key-grouping;
428 description
429 "A locally-defined or referenced certificate
430 to be used for client authentication.";
431 reference
432 "RFC ZZZZ
433 YANG Data Model for a Centralized Keystore Mechanism";
434 }
435 } // end auth-type
436 } // end client-identity
437 } // end client-identity-grouping
439 grouping server-auth-grouping {
440 description
441 "A reusable grouping for configuring SSH server
442 authentication.";
443 container server-auth {
444 must 'pinned-ssh-host-keys or pinned-ca-certs or '
445 + 'pinned-server-certs';
446 description
447 "Trusted server identities.";
449 leaf pinned-ssh-host-keys {
450 if-feature "ta:ssh-host-keys";
451 type ta:pinned-host-keys-ref;
452 description
453 "A reference to a list of SSH host keys used by the
454 SSH client to authenticate SSH server host keys.
455 A server host key is authenticated if it is an exact
456 match to a configured SSH host key.";
457 reference
458 "RFC YYYY: YANG Data Model for Global Trust Anchors";
459 }
460 leaf pinned-ca-certs {
461 if-feature sshcmn:ssh-x509-certs;
462 if-feature "ta:x509-certificates";
463 type ta:pinned-certificates-ref;
464 description
465 "A reference to a list of certificate authority (CA)
466 certificates used by the SSH client to authenticate
467 SSH server certificates. A server certificate is
468 authenticated if it has a valid chain of trust to
469 a configured CA certificate.";
470 reference
471 "RFC YYYY: YANG Data Model for Global Trust Anchors";
472 }
474 leaf pinned-server-certs {
475 if-feature sshcmn:ssh-x509-certs;
476 if-feature "ta:x509-certificates";
477 type ta:pinned-certificates-ref;
478 description
479 "A reference to a list of server certificates used by
480 the SSH client to authenticate SSH server certificates.
481 A server certificate is authenticated if it is an
482 exact match to a configured server certificate.";
483 reference
484 "RFC YYYY: YANG Data Model for Global Trust Anchors";
485 }
486 } // end server-auth
487 } // end server-auth-grouping
489 grouping transport-params-grouping {
490 description
491 "A reusable grouping for configuring a SSH transport
492 parameters.";
493 container transport-params {
494 if-feature ssh-client-transport-params-config;
495 description
496 "Configurable parameters of the SSH transport layer.";
498 uses sshcmn:transport-params-grouping;
499 }
500 } // end transport-params-grouping
502 }
503
505 4. The SSH Server Model
507 4.1. Tree Diagram
509 This section provides a tree diagram [RFC8340] for the "ietf-ssh-
510 server" module that does not have groupings expanded.
512 module: ietf-ssh-server
514 grouping transport-params-grouping
515 +-- transport-params {ssh-server-transport-params-config}?
516 +---u transport-params-grouping
517 grouping client-auth-grouping
518 +-- client-cert-auth {sshcmn:ssh-x509-certs}?
519 +-- pinned-ca-certs? ta:pinned-certificates-ref
520 | {ta:x509-certificates}?
521 +-- pinned-client-certs? ta:pinned-certificates-ref
522 {ta:x509-certificates}?
523 grouping server-identity-grouping
524 +-- server-identity
525 +-- host-key* [name]
526 +-- name? string
527 +-- (host-key-type)
528 +--:(public-key)
529 | +-- public-key
530 | +---u server-identity-grouping
531 +--:(certificate)
532 +-- certificate {sshcmn:ssh-x509-certs}?
533 +---u server-identity-grouping
534 grouping ssh-server-grouping
535 +---u server-identity-grouping
536 +---u client-auth-grouping
537 +---u transport-params-grouping
539 4.2. Example Usage
541 This section presents two examples showing the ssh-server-grouping
542 populated with some data. These examples are effectively the same
543 except the first configures the server identity using a local key
544 while the second uses a key configured in a keystore. Both examples
545 are consistent with the examples presented in Section 3 of
547 [I-D.ietf-netconf-trust-anchors] and Section 3.2 of
548 [I-D.ietf-netconf-keystore].
550 The following example configures the server identity using a local
551 key:
553 [Note: '\' line wrapping for formatting only]
555
558
559
560
561 deployment-specific-certificate
562
563 ct:rsa2048
565 base64encodedvalue==
566 base64encodedvalue==
567
568
569
571
572
573 explicitly-trusted-client-ca-certs
575 explicitly-trusted-client-certs
577
579
580
581 algs:ssh-rsa
582
583
584
585 algs:diffie-hellman-group-exchange-sha256
586
587
588
589 algs:aes256-ctr
590 algs:aes192-ctr
591 algs:aes128-ctr
592 algs:aes256-cbc
593 algs:aes192-cbc
594 algs:aes128-cbc
595
596
597 algs:hmac-sha2-256
598 algs:hmac-sha2-512
599
600
602
604 The following example configures the server identity using a key from
605 the keystore:
607 [Note: '\' line wrapping for formatting only]
609
612
613
614
615 deployment-specific-certificate
616
617 ex-rsa-key
618
619
620
622
623
624 explicitly-trusted-client-ca-certs
626 explicitly-trusted-client-certs
628
630
631
632 algs:ssh-rsa
633
634
635
636 algs:diffie-hellman-group-exchange-sha256
637
638
639
640 algs:aes256-ctr
641 algs:aes192-ctr
642 algs:aes128-ctr
643 algs:aes256-cbc
644 algs:aes192-cbc
645 algs:aes128-cbc
646
647
648 algs:hmac-sha2-256
649 algs:hmac-sha2-512
650
651
653
655 4.3. YANG Module
657 This YANG module has normative references to
658 [I-D.ietf-netconf-trust-anchors] and [I-D.ietf-netconf-keystore] and
659 informative references to [RFC4253] and [RFC7317].
661 file "ietf-ssh-server@2018-10-22.yang"
662 module ietf-ssh-server {
663 yang-version 1.1;
665 namespace "urn:ietf:params:xml:ns:yang:ietf-ssh-server";
666 prefix "sshs";
668 import ietf-ssh-common {
669 prefix sshcmn;
670 revision-date 2018-10-22; // stable grouping definitions
671 reference
672 "RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
673 }
675 import ietf-trust-anchors {
676 prefix ta;
677 reference
678 "RFC YYYY: YANG Data Model for Global Trust Anchors";
679 }
681 import ietf-keystore {
682 prefix ks;
683 reference
684 "RFC ZZZZ:
685 YANG Data Model for a Centralized Keystore Mechanism";
686 }
688 organization
689 "IETF NETCONF (Network Configuration) Working Group";
691 contact
692 "WG Web:
693 WG List:
695 Author: Kent Watsen
696
698 Author: Gary Wu
699 ";
701 description
702 "This module defines a reusable grouping for a SSH server that
703 can be used as a basis for specific SSH server instances.
705 Copyright (c) 2018 IETF Trust and the persons identified as
706 authors of the code. All rights reserved.
708 Redistribution and use in source and binary forms, with or
709 without modification, is permitted pursuant to, and subject
710 to the license terms contained in, the Simplified BSD
711 License set forth in Section 4.c of the IETF Trust's
712 Legal Provisions Relating to IETF Documents
713 (http://trustee.ietf.org/license-info).
715 This version of this YANG module is part of RFC XXXX; see
716 the RFC itself for full legal notices.";
718 revision "2018-10-22" {
719 description
720 "Initial version";
721 reference
722 "RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
723 }
725 // features
727 feature ssh-server-transport-params-config {
728 description
729 "SSH transport layer parameters are configurable on an SSH
730 server.";
731 }
733 // groupings
735 grouping ssh-server-grouping {
736 description
737 "A reusable grouping for configuring a SSH server without
738 any consideration for how underlying TCP sessions are
739 established.";
740 uses server-identity-grouping;
741 uses client-auth-grouping;
742 uses transport-params-grouping;
743 }
745 grouping server-identity-grouping {
746 description
747 "A reusable grouping for configuring an SSH server identity.";
748 container server-identity {
749 description
750 "The list of host-keys the SSH server will present when
751 establishing a SSH connection.";
752 list host-key {
753 key name;
754 min-elements 1;
755 ordered-by user;
756 description
757 "An ordered list of host keys the SSH server will use to
758 construct its ordered list of algorithms, when sending
759 its SSH_MSG_KEXINIT message, as defined in Section 7.1
760 of RFC 4253.";
761 reference
762 "RFC 4253: The Secure Shell (SSH) Transport Layer
763 Protocol";
764 leaf name {
765 type string;
766 description
767 "An arbitrary name for this host-key";
768 }
769 choice host-key-type {
770 mandatory true;
771 description
772 "The type of host key being specified";
773 container public-key {
774 uses ks:local-or-keystore-asymmetric-key-grouping;
775 description
776 "A locally-defined or referenced asymmetric key pair
777 to be used for the SSH server's host key.";
778 reference
779 "RFC ZZZZ: YANG Data Model for a Centralized
780 Keystore Mechanism";
781 }
782 container certificate {
783 if-feature sshcmn:ssh-x509-certs;
784 uses
785 ks:local-or-keystore-end-entity-cert-with-key-grouping;
786 description
787 "A locally-defined or referenced end-entity
788 certificate to be used for the SSH server's
789 host key.";
790 reference
791 "RFC ZZZZ: YANG Data Model for a Centralized
792 Keystore Mechanism";
793 }
794 }
795 }
796 } // end server-identity
797 } // end server-identity-grouping
798 grouping client-auth-grouping {
799 description
800 "A reusable grouping for configuring a SSH client
801 authentication.";
802 container client-cert-auth {
803 if-feature sshcmn:ssh-x509-certs;
804 description
805 "A reference to a list of pinned certificate authority (CA)
806 certificates and a reference to a list of pinned client
807 certificates.
809 Note: password and public-key based client authentication
810 are not configured in this YANG module as they are
811 expected to be configured by the ietf-system module
812 defined in RFC 7317.";
813 reference
814 "RFC 7317: A YANG Data Model for System Management";
815 leaf pinned-ca-certs {
816 if-feature "ta:x509-certificates";
817 type ta:pinned-certificates-ref;
818 description
819 "A reference to a list of certificate authority (CA)
820 certificates used by the SSH server to authenticate
821 SSH client certificates. A client certificate is
822 authenticated if it has a valid chain of trust to
823 a configured pinned CA certificate.";
824 reference
825 "RFC YYYY: YANG Data Model for Global Trust Anchors";
826 }
827 leaf pinned-client-certs {
828 if-feature "ta:x509-certificates";
829 type ta:pinned-certificates-ref;
830 description
831 "A reference to a list of client certificates used by
832 the SSH server to authenticate SSH client certificates.
833 A clients certificate is authenticated if it is an
834 exact match to a configured pinned client certificate.";
835 reference
836 "RFC YYYY: YANG Data Model for Global Trust Anchors";
837 }
838 }
839 } // end client-auth-grouping
841 grouping transport-params-grouping {
842 description
843 "A reusable grouping for configuring a SSH transport
844 parameters.";
845 container transport-params {
846 if-feature ssh-server-transport-params-config;
847 description
848 "Configurable parameters of the SSH transport layer.";
849 uses sshcmn:transport-params-grouping;
850 }
851 } // end transport-params-grouping
853 }
854
856 5. The SSH Common Model
858 The SSH common model presented in this section contains identities
859 and groupings common to both SSH clients and SSH servers. The
860 transport-params-grouping can be used to configure the list of SSH
861 transport algorithms permitted by the SSH client or SSH server. The
862 lists of algorithms are ordered such that, if multiple algorithms are
863 permitted by the client, the algorithm that appears first in its list
864 that is also permitted by the server is used for the SSH transport
865 layer connection. The ability to restrict the the algorithms allowed
866 is provided in this grouping for SSH clients and SSH servers that are
867 capable of doing so and may serve to make SSH clients and SSH servers
868 compliant with security policies.
870 [I-D.ietf-netconf-crypto-types] defines six categories of
871 cryptographic algorithms (hash-algorithm, symmetric-key-encryption-
872 algorithm, mac-algorithm, asymmetric-key-encryption-algorithm,
873 signature-algorithm, key-negotiation-algorithm) and lists several
874 widely accepted algorithms for each of them. The SSH client and
875 server models use one or more of these algorithms. The SSH common
876 model includes four parameters for configuring its permitted SSH
877 algorithms, which are: host-key-alg, key-exchange-alg, encryption-alg
878 and mac-alg. The following tables are provided, in part, to define
879 the subset of algorithms defined in the crypto-types model used by
880 SSH and, in part, to ensure compatibility of configured SSH
881 cryptographic parameters for configuring its permitted SSH algorithms
882 ("sshcmn" representing SSH common model, and "ct" representing
883 crypto-types model which the SSH client/server model is based on):
885 +-------------------------------+-------------------------------+
886 | sshcmn:host-key-alg | ct:signature-algorithm |
887 +-------------------------------+-------------------------------+
888 | dsa-sha1 | dsa-sha1 |
889 | rsa-pkcs1-sha1 | rsa-pkcs1-sha1 |
890 | rsa-pkcs1-sha256 | rsa-pkcs1-sha256 |
891 | rsa-pkcs1-sha512 | rsa-pkcs1-sha512 |
892 | ecdsa-secp256r1-sha256 | ecdsa-secp256r1-sha256 |
893 | ecdsa-secp384r1-sha384 | ecdsa-secp384r1-sha384 |
894 | ecdsa-secp521r1-sha512 | ecdsa-secp521r1-sha512 |
895 | x509v3-rsa-pkcs1-sha1 | x509v3-rsa-pkcs1-sha1 |
896 | x509v3-rsa2048-pkcs1-sha256 | x509v3-rsa2048-pkcs1-sha1 |
897 | x509v3-ecdsa-secp256r1-sha256 | x509v3-ecdsa-secp256r1-sha256 |
898 | x509v3-ecdsa-secp384r1-sha384 | x509v3-ecdsa-secp384r1-sha384 |
899 | x509v3-ecdsa-secp521r1-sha512 | x509v3-ecdsa-secp521r1-sha512 |
900 +-------------------------------+-------------------------------+
902 Table 1 The SSH Host-key-alg Compatibility Matrix
904 +-------------------------------+-------------------------------+
905 | sshcmn:key-exchange-alg | ct:key-negotiation-algorithm |
906 +-------------------------------+-------------------------------+
907 | diffie-hellman-group14-sha1 | diffie-hellman-group14-sha1 |
908 | diffie-hellman-group14-sha256 | diffie-hellman-group14-sha256 |
909 | diffie-hellman-group15-sha512 | diffie-hellman-group15-sha512 |
910 | diffie-hellman-group16-sha512 | diffie-hellman-group16-sha512 |
911 | diffie-hellman-group17-sha512 | diffie-hellman-group17-sha512 |
912 | diffie-hellman-group18-sha512 | diffie-hellman-group18-sha512 |
913 | ecdh-sha2-secp256r1 | ecdh-sha2-secp256r1 |
914 | ecdh-sha2-secp384r1 | ecdh-sha2-secp384r1 |
915 +-------------------------------+-------------------------------+
917 Table 2 The SSH Key-exchange-alg Compatibility Matrix
919 +-----------------------+---------------------------------------+
920 | sshcmn:encryption-alg | ct:symmetric-key-encryption-algorithm |
921 +-----------------------+---------------------------------------+
922 | aes-128-cbc | aes-128-cbc |
923 | aes-192-cbc | aes-192-cbc |
924 | aes-256-cbc | aes-256-cbc |
925 | aes-128-ctr | aes-128-ctr |
926 | aes-192-ctr | aes-192-ctr |
927 | aes-256-ctr | aes-256-ctr |
928 +-----------------------+---------------------------------------+
930 Table 3 The SSH Encryption-alg Compatibility Matrix
931 +----------------+-------------------+
932 | sshcmn:mac-alg | ct:mac-algorithm |
933 +----------------+-------------------+
934 | hmac-sha1 | hmac-sha1 |
935 | hmac-sha1-96 | hmac-sha1-96 |
936 | hmac-sha2-256 | hmac-sha2-256 |
937 | hmac-sha2-512 | hmac-sha2-512 |
938 +----------------+-------------------+
940 Table 4 The SSH Mac-alg Compatibility Matrix
942 As is seen in the tables above, the names of the "sshcmn" algorithms
943 are all identical to the names of algorithms defined in
944 [I-D.ietf-netconf-crypto-types]. While appearing to be redundant, it
945 is important to realize that not all the algorithms defined in
946 [I-D.ietf-netconf-crypto-types] are supported by SSH. That is, the
947 algorithms supported by SSH are a subset of the algorithms defined in
948 [I-D.ietf-netconf-crypto-types]. The algorithms used by SSH are
949 redefined in this document in order to constrain the algorithms that
950 may be selected to just the ones used by SSH.
952 Features are defined for algorithms that are OPTIONAL or are not
953 widely supported by popular implementations. Note that the list of
954 algorithms is not exhaustive. As well, some algorithms that are
955 REQUIRED by [RFC4253] are missing, notably "ssh-dss" and "diffie-
956 hellman-group1-sha1" due to their weak security and there being
957 alternatives that are widely supported.
959 5.1. Tree Diagram
961 The following tree diagram [RFC8340] provides an overview of the data
962 model for the "ietf-ssh-common" module.
964 module: ietf-ssh-common
966 grouping transport-params-grouping
967 +-- host-key
968 | +-- host-key-alg* identityref
969 +-- key-exchange
970 | +-- key-exchange-alg* identityref
971 +-- encryption
972 | +-- encryption-alg* identityref
973 +-- mac
974 +-- mac-alg* identityref
976 5.2. Example Usage
978 This following example illustrates how the transport-params-grouping
979 appears when populated with some data.
981
984
985 algs:x509v3-rsa2048-sha256
986 algs:ssh-rsa
987
988
989
990 algs:diffie-hellman-group-exchange-sha256
991
992
993
994 algs:aes256-ctr
995 algs:aes192-ctr
996 algs:aes128-ctr
997 algs:aes256-cbc
998 algs:aes192-cbc
999 algs:aes128-cbc
1000
1001
1002 algs:hmac-sha2-256
1003 algs:hmac-sha2-512
1004
1005
1007 5.3. YANG Module
1009 This YANG module has normative references to [RFC4253], [RFC4344],
1010 [RFC4419], [RFC5656], [RFC6187], and [RFC6668].
1012 file "ietf-ssh-common@2018-10-22.yang"
1013 module ietf-ssh-common {
1014 yang-version 1.1;
1016 namespace "urn:ietf:params:xml:ns:yang:ietf-ssh-common";
1017 prefix "sshcmn";
1019 organization
1020 "IETF NETCONF (Network Configuration) Working Group";
1022 contact
1023 "WG Web:
1024 WG List:
1026 Author: Kent Watsen
1027
1029 Author: Gary Wu
1030 ";
1032 description
1033 "This module defines a common features, identities, and
1034 groupings for Secure Shell (SSH).
1036 Copyright (c) 2018 IETF Trust and the persons identified as
1037 authors of the code. All rights reserved.
1039 Redistribution and use in source and binary forms, with or
1040 without modification, is permitted pursuant to, and subject
1041 to the license terms contained in, the Simplified BSD
1042 License set forth in Section 4.c of the IETF Trust's
1043 Legal Provisions Relating to IETF Documents
1044 (http://trustee.ietf.org/license-info).
1046 This version of this YANG module is part of RFC XXXX; see
1047 the RFC itself for full legal notices.";
1049 revision "2018-10-22" {
1050 description
1051 "Initial version";
1052 reference
1053 "RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
1054 }
1056 // features
1058 feature ssh-ecc {
1059 description
1060 "Elliptic Curve Cryptography is supported for SSH.";
1061 reference
1062 "RFC 5656: Elliptic Curve Algorithm Integration in the
1063 Secure Shell Transport Layer";
1064 }
1066 feature ssh-x509-certs {
1067 description
1068 "X.509v3 certificates are supported for SSH per RFC 6187.";
1069 reference
1070 "RFC 6187: X.509v3 Certificates for Secure Shell
1071 Authentication";
1073 }
1075 feature ssh-dh-group-exchange {
1076 description
1077 "Diffie-Hellman Group Exchange is supported for SSH.";
1078 reference
1079 "RFC 4419: Diffie-Hellman Group Exchange for the
1080 Secure Shell (SSH) Transport Layer Protocol";
1081 }
1083 feature ssh-ctr {
1084 description
1085 "SDCTR encryption mode is supported for SSH.";
1086 reference
1087 "RFC 4344: The Secure Shell (SSH) Transport Layer
1088 Encryption Modes";
1089 }
1091 feature ssh-sha2 {
1092 description
1093 "The SHA2 family of cryptographic hash functions is
1094 supported for SSH.";
1095 reference
1096 "FIPS PUB 180-4: Secure Hash Standard (SHS)";
1097 }
1099 // identities
1101 identity public-key-alg-base {
1102 description
1103 "Base identity used to identify public key algorithms.";
1104 }
1106 identity ssh-dss {
1107 base public-key-alg-base;
1108 description
1109 "Digital Signature Algorithm using SHA-1 as the
1110 hashing algorithm.";
1111 reference
1112 "RFC 4253:
1113 The Secure Shell (SSH) Transport Layer Protocol";
1114 }
1116 identity ssh-rsa {
1117 base public-key-alg-base;
1118 description
1119 "RSASSA-PKCS1-v1_5 signature scheme using SHA-1 as the
1120 hashing algorithm.";
1122 reference
1123 "RFC 4253:
1124 The Secure Shell (SSH) Transport Layer Protocol";
1125 }
1127 identity ecdsa-sha2-nistp256 {
1128 base public-key-alg-base;
1129 if-feature "ssh-ecc and ssh-sha2";
1130 description
1131 "Elliptic Curve Digital Signature Algorithm (ECDSA) using the
1132 nistp256 curve and the SHA2 family of hashing algorithms.";
1133 reference
1134 "RFC 5656: Elliptic Curve Algorithm Integration in the
1135 Secure Shell Transport Layer";
1136 }
1138 identity ecdsa-sha2-nistp384 {
1139 base public-key-alg-base;
1140 if-feature "ssh-ecc and ssh-sha2";
1141 description
1142 "Elliptic Curve Digital Signature Algorithm (ECDSA) using the
1143 nistp384 curve and the SHA2 family of hashing algorithms.";
1144 reference
1145 "RFC 5656: Elliptic Curve Algorithm Integration in the
1146 Secure Shell Transport Layer";
1147 }
1149 identity ecdsa-sha2-nistp521 {
1150 base public-key-alg-base;
1151 if-feature "ssh-ecc and ssh-sha2";
1152 description
1153 "Elliptic Curve Digital Signature Algorithm (ECDSA) using the
1154 nistp521 curve and the SHA2 family of hashing algorithms.";
1155 reference
1156 "RFC 5656: Elliptic Curve Algorithm Integration in the
1157 Secure Shell Transport Layer";
1158 }
1160 identity x509v3-ssh-rsa {
1161 base public-key-alg-base;
1162 if-feature ssh-x509-certs;
1163 description
1164 "RSASSA-PKCS1-v1_5 signature scheme using a public key stored
1165 in an X.509v3 certificate and using SHA-1 as the hashing
1166 algorithm.";
1167 reference
1168 "RFC 6187: X.509v3 Certificates for Secure Shell
1169 Authentication";
1171 }
1173 identity x509v3-rsa2048-sha256 {
1174 base public-key-alg-base;
1175 if-feature "ssh-x509-certs and ssh-sha2";
1176 description
1177 "RSASSA-PKCS1-v1_5 signature scheme using a public key stored
1178 in an X.509v3 certificate and using SHA-256 as the hashing
1179 algorithm. RSA keys conveyed using this format MUST have a
1180 modulus of at least 2048 bits.";
1181 reference
1182 "RFC 6187: X.509v3 Certificates for Secure Shell
1183 Authentication";
1184 }
1186 identity x509v3-ecdsa-sha2-nistp256 {
1187 base public-key-alg-base;
1188 if-feature "ssh-ecc and ssh-x509-certs and ssh-sha2";
1189 description
1190 "Elliptic Curve Digital Signature Algorithm (ECDSA)
1191 using the nistp256 curve with a public key stored in
1192 an X.509v3 certificate and using the SHA2 family of
1193 hashing algorithms.";
1194 reference
1195 "RFC 6187: X.509v3 Certificates for Secure Shell
1196 Authentication";
1197 }
1199 identity x509v3-ecdsa-sha2-nistp384 {
1200 base public-key-alg-base;
1201 if-feature "ssh-ecc and ssh-x509-certs and ssh-sha2";
1202 description
1203 "Elliptic Curve Digital Signature Algorithm (ECDSA)
1204 using the nistp384 curve with a public key stored in
1205 an X.509v3 certificate and using the SHA2 family of
1206 hashing algorithms.";
1207 reference
1208 "RFC 6187: X.509v3 Certificates for Secure Shell
1209 Authentication";
1210 }
1212 identity x509v3-ecdsa-sha2-nistp521 {
1213 base public-key-alg-base;
1214 if-feature "ssh-ecc and ssh-x509-certs and ssh-sha2";
1215 description
1216 "Elliptic Curve Digital Signature Algorithm (ECDSA)
1217 using the nistp521 curve with a public key stored in
1218 an X.509v3 certificate and using the SHA2 family of
1219 hashing algorithms.";
1220 reference
1221 "RFC 6187: X.509v3 Certificates for Secure Shell
1222 Authentication";
1223 }
1225 identity key-exchange-alg-base {
1226 description
1227 "Base identity used to identify key exchange algorithms.";
1228 }
1230 identity diffie-hellman-group14-sha1 {
1231 base key-exchange-alg-base;
1232 description
1233 "Diffie-Hellman key exchange with SHA-1 as HASH and
1234 Oakley Group 14 (2048-bit MODP Group).";
1235 reference
1236 "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
1237 }
1239 identity diffie-hellman-group-exchange-sha1 {
1240 base key-exchange-alg-base;
1241 if-feature ssh-dh-group-exchange;
1242 description
1243 "Diffie-Hellman Group and Key Exchange with SHA-1 as HASH.";
1244 reference
1245 "RFC 4419: Diffie-Hellman Group Exchange for the
1246 Secure Shell (SSH) Transport Layer Protocol";
1247 }
1249 identity diffie-hellman-group-exchange-sha256 {
1250 base key-exchange-alg-base;
1251 if-feature "ssh-dh-group-exchange and ssh-sha2";
1252 description
1253 "Diffie-Hellman Group and Key Exchange with SHA-256 as HASH.";
1254 reference
1255 "RFC 4419: Diffie-Hellman Group Exchange for the
1256 Secure Shell (SSH) Transport Layer Protocol";
1257 }
1259 identity ecdh-sha2-nistp256 {
1260 base key-exchange-alg-base;
1261 if-feature "ssh-ecc and ssh-sha2";
1262 description
1263 "Elliptic Curve Diffie-Hellman (ECDH) key exchange using the
1264 nistp256 curve and the SHA2 family of hashing algorithms.";
1265 reference
1266 "RFC 5656: Elliptic Curve Algorithm Integration in the
1267 Secure Shell Transport Layer";
1268 }
1270 identity ecdh-sha2-nistp384 {
1271 base key-exchange-alg-base;
1272 if-feature "ssh-ecc and ssh-sha2";
1273 description
1274 "Elliptic Curve Diffie-Hellman (ECDH) key exchange using the
1275 nistp384 curve and the SHA2 family of hashing algorithms.";
1276 reference
1277 "RFC 5656: Elliptic Curve Algorithm Integration in the
1278 Secure Shell Transport Layer";
1279 }
1281 identity ecdh-sha2-nistp521 {
1282 base key-exchange-alg-base;
1283 if-feature "ssh-ecc and ssh-sha2";
1284 description
1285 "Elliptic Curve Diffie-Hellman (ECDH) key exchange using the
1286 nistp521 curve and the SHA2 family of hashing algorithms.";
1287 reference
1288 "RFC 5656: Elliptic Curve Algorithm Integration in the
1289 Secure Shell Transport Layer";
1290 }
1292 identity encryption-alg-base {
1293 description
1294 "Base identity used to identify encryption algorithms.";
1295 }
1297 identity triple-des-cbc {
1298 base encryption-alg-base;
1299 description
1300 "Three-key 3DES in CBC mode.";
1301 reference
1302 "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
1303 }
1305 identity aes128-cbc {
1306 base encryption-alg-base;
1307 description
1308 "AES in CBC mode, with a 128-bit key.";
1309 reference
1310 "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
1311 }
1313 identity aes192-cbc {
1314 base encryption-alg-base;
1315 description
1316 "AES in CBC mode, with a 192-bit key.";
1317 reference
1318 "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
1319 }
1321 identity aes256-cbc {
1322 base encryption-alg-base;
1323 description
1324 "AES in CBC mode, with a 256-bit key.";
1325 reference
1326 "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
1327 }
1329 identity aes128-ctr {
1330 base encryption-alg-base;
1331 if-feature ssh-ctr;
1332 description
1333 "AES in SDCTR mode, with 128-bit key.";
1334 reference
1335 "RFC 4344: The Secure Shell (SSH) Transport Layer Encryption
1336 Modes";
1337 }
1339 identity aes192-ctr {
1340 base encryption-alg-base;
1341 if-feature ssh-ctr;
1342 description
1343 "AES in SDCTR mode, with 192-bit key.";
1344 reference
1345 "RFC 4344: The Secure Shell (SSH) Transport Layer Encryption
1346 Modes";
1347 }
1349 identity aes256-ctr {
1350 base encryption-alg-base;
1351 if-feature ssh-ctr;
1352 description
1353 "AES in SDCTR mode, with 256-bit key.";
1354 reference
1355 "RFC 4344: The Secure Shell (SSH) Transport Layer Encryption
1356 Modes";
1357 }
1359 identity mac-alg-base {
1360 description
1361 "Base identity used to identify message authentication
1362 code (MAC) algorithms.";
1364 }
1366 identity hmac-sha1 {
1367 base mac-alg-base;
1368 description
1369 "HMAC-SHA1";
1370 reference
1371 "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
1372 }
1374 identity hmac-sha2-256 {
1375 base mac-alg-base;
1376 if-feature "ssh-sha2";
1377 description
1378 "HMAC-SHA2-256";
1379 reference
1380 "RFC 6668: SHA-2 Data Integrity Verification for the
1381 Secure Shell (SSH) Transport Layer Protocol";
1382 }
1384 identity hmac-sha2-512 {
1385 base mac-alg-base;
1386 if-feature "ssh-sha2";
1387 description
1388 "HMAC-SHA2-512";
1389 reference
1390 "RFC 6668: SHA-2 Data Integrity Verification for the
1391 Secure Shell (SSH) Transport Layer Protocol";
1392 }
1394 // groupings
1396 grouping transport-params-grouping {
1397 description
1398 "A reusable grouping for SSH transport parameters.";
1399 reference
1400 "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
1401 container host-key {
1402 description
1403 "Parameters regarding host key.";
1404 leaf-list host-key-alg {
1405 type identityref {
1406 base public-key-alg-base;
1407 }
1408 ordered-by user;
1409 description
1410 "Acceptable host key algorithms in order of descending
1411 preference. The configured host key algorithms should
1412 be compatible with the algorithm used by the configured
1413 private key. Please see Section 5 of RFC XXXX for
1414 valid combinations.
1416 If this leaf-list is not configured (has zero elements)
1417 the acceptable host key algorithms are implementation-
1418 defined.";
1419 reference
1420 "RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
1421 }
1422 }
1423 container key-exchange {
1424 description
1425 "Parameters regarding key exchange.";
1426 leaf-list key-exchange-alg {
1427 type identityref {
1428 base key-exchange-alg-base;
1429 }
1430 ordered-by user;
1431 description
1432 "Acceptable key exchange algorithms in order of descending
1433 preference.
1435 If this leaf-list is not configured (has zero elements)
1436 the acceptable key exchange algorithms are implementation
1437 defined.";
1438 }
1439 }
1440 container encryption {
1441 description
1442 "Parameters regarding encryption.";
1443 leaf-list encryption-alg {
1444 type identityref {
1445 base encryption-alg-base;
1446 }
1447 ordered-by user;
1448 description
1449 "Acceptable encryption algorithms in order of descending
1450 preference.
1452 If this leaf-list is not configured (has zero elements)
1453 the acceptable encryption algorithms are implementation
1454 defined.";
1455 }
1456 }
1457 container mac {
1458 description
1459 "Parameters regarding message authentication code (MAC).";
1461 leaf-list mac-alg {
1462 type identityref {
1463 base mac-alg-base;
1464 }
1465 ordered-by user;
1466 description
1467 "Acceptable MAC algorithms in order of descending
1468 preference.
1470 If this leaf-list is not configured (has zero elements)
1471 the acceptable MAC algorithms are implementation-
1472 defined.";
1473 }
1474 }
1476 } // transport-params-grouping
1478 }
1479
1481 6. Security Considerations
1483 The YANG modules defined in this document are designed to be accessed
1484 via YANG based management protocols, such as NETCONF [RFC6241] and
1485 RESTCONF [RFC8040]. Both of these protocols have mandatory-to-
1486 implement secure transport layers (e.g., SSH, TLS) with mutual
1487 authentication.
1489 The NETCONF access control model (NACM) [RFC8341] provides the means
1490 to restrict access for particular users to a pre-configured subset of
1491 all available protocol operations and content.
1493 Since the modules defined in this document define only groupings,
1494 these considerations are primarily for the designers of other modules
1495 that use these groupings.
1497 There are a number of data nodes defined in the YANG modules that are
1498 writable/creatable/deletable (i.e., config true, which is the
1499 default). These data nodes may be considered sensitive or vulnerable
1500 in some network environments. Write operations (e.g., edit-config)
1501 to these data nodes without proper protection can have a negative
1502 effect on network operations. These are the subtrees and data nodes
1503 and their sensitivity/vulnerability:
1505 /: The entire data tree defined by all the modules defined in this
1506 draft are sensitive to write operations. For instance, the
1507 addition or removal of references to keys, certificates,
1508 trusted anchors, etc., can dramatically alter the implemented
1509 security policy. However, no NACM annotations are applied as
1510 the data SHOULD be editable by users other than a designated
1511 'recovery session'.
1513 Some of the readable data nodes in the YANG modules may be considered
1514 sensitive or vulnerable in some network environments. It is thus
1515 important to control read access (e.g., via get, get-config, or
1516 notification) to these data nodes. These are the subtrees and data
1517 nodes and their sensitivity/vulnerability:
1519 /client-auth/password: This node in the 'ietf-ssh-client' module
1520 is additionally sensitive to read operations such that, in
1521 normal use cases, it should never be returned to a client. The
1522 only time this node should be returned is to support backup/
1523 restore type workflows. However, no NACM annotations are
1524 applied as the data SHOULD be writable by users other than a
1525 designated 'recovery session'.
1527 Some of the RPC operations in this YANG module may be considered
1528 sensitive or vulnerable in some network environments. It is thus
1529 important to control access to these operations. These are the
1530 operations and their sensitivity/vulnerability:
1532 NONE
1534 7. IANA Considerations
1536 7.1. The IETF XML Registry
1538 This document registers three URIs in the "ns" subregistry of the
1539 IETF XML Registry [RFC3688]. Following the format in [RFC3688], the
1540 following registrations are requested:
1542 URI: urn:ietf:params:xml:ns:yang:ietf-ssh-client
1543 Registrant Contact: The NETCONF WG of the IETF.
1544 XML: N/A, the requested URI is an XML namespace.
1545 URI: urn:ietf:params:xml:ns:yang:ietf-ssh-server
1546 Registrant Contact: The NETCONF WG of the IETF.
1547 XML: N/A, the requested URI is an XML namespace.
1548 URI: urn:ietf:params:xml:ns:yang:ietf-ssh-common
1549 Registrant Contact: The NETCONF WG of the IETF.
1550 XML: N/A, the requested URI is an XML namespace.
1552 7.2. The YANG Module Names Registry
1554 This document registers three YANG modules in the YANG Module Names
1555 registry [RFC6020]. Following the format in [RFC6020], the the
1556 following registrations are requested:
1558 name: ietf-ssh-client
1559 namespace: urn:ietf:params:xml:ns:yang:ietf-ssh-client
1560 prefix: sshc
1561 reference: RFC XXXX
1562 name: ietf-ssh-server
1563 namespace: urn:ietf:params:xml:ns:yang:ietf-ssh-server
1564 prefix: sshs
1565 reference: RFC XXXX
1566 name: ietf-ssh-common
1567 namespace: urn:ietf:params:xml:ns:yang:ietf-ssh-common
1568 prefix: sshcmn
1569 reference: RFC XXXX
1571 8. References
1573 8.1. Normative References
1575 [I-D.ietf-netconf-crypto-types]
1576 Watsen, K., "Common YANG Data Types for Cryptography",
1577 draft-ietf-netconf-crypto-types-01 (work in progress),
1578 September 2018.
1580 [I-D.ietf-netconf-keystore]
1581 Watsen, K., "YANG Data Model for a Centralized Keystore
1582 Mechanism", draft-ietf-netconf-keystore-06 (work in
1583 progress), September 2018.
1585 [I-D.ietf-netconf-trust-anchors]
1586 Watsen, K., "YANG Data Model for Global Trust Anchors",
1587 draft-ietf-netconf-trust-anchors-01 (work in progress),
1588 September 2018.
1590 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
1591 Requirement Levels", BCP 14, RFC 2119,
1592 DOI 10.17487/RFC2119, March 1997,
1593 .
1595 [RFC4344] Bellare, M., Kohno, T., and C. Namprempre, "The Secure
1596 Shell (SSH) Transport Layer Encryption Modes", RFC 4344,
1597 DOI 10.17487/RFC4344, January 2006,
1598 .
1600 [RFC4419] Friedl, M., Provos, N., and W. Simpson, "Diffie-Hellman
1601 Group Exchange for the Secure Shell (SSH) Transport Layer
1602 Protocol", RFC 4419, DOI 10.17487/RFC4419, March 2006,
1603 .
1605 [RFC5656] Stebila, D. and J. Green, "Elliptic Curve Algorithm
1606 Integration in the Secure Shell Transport Layer",
1607 RFC 5656, DOI 10.17487/RFC5656, December 2009,
1608 .
1610 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
1611 the Network Configuration Protocol (NETCONF)", RFC 6020,
1612 DOI 10.17487/RFC6020, October 2010,
1613 .
1615 [RFC6187] Igoe, K. and D. Stebila, "X.509v3 Certificates for Secure
1616 Shell Authentication", RFC 6187, DOI 10.17487/RFC6187,
1617 March 2011, .
1619 [RFC6668] Bider, D. and M. Baushke, "SHA-2 Data Integrity
1620 Verification for the Secure Shell (SSH) Transport Layer
1621 Protocol", RFC 6668, DOI 10.17487/RFC6668, July 2012,
1622 .
1624 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
1625 RFC 7950, DOI 10.17487/RFC7950, August 2016,
1626 .
1628 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
1629 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
1630 May 2017, .
1632 [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
1633 Access Control Model", STD 91, RFC 8341,
1634 DOI 10.17487/RFC8341, March 2018,
1635 .
1637 8.2. Informative References
1639 [OPENSSH] "OpenSSH", 2016, .
1641 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
1642 DOI 10.17487/RFC3688, January 2004,
1643 .
1645 [RFC4252] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
1646 Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
1647 January 2006, .
1649 [RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
1650 Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253,
1651 January 2006, .
1653 [RFC4254] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
1654 Connection Protocol", RFC 4254, DOI 10.17487/RFC4254,
1655 January 2006, .
1657 [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
1658 and A. Bierman, Ed., "Network Configuration Protocol
1659 (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
1660 .
1662 [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
1663 Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
1664 .
1666 [RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for
1667 System Management", RFC 7317, DOI 10.17487/RFC7317, August
1668 2014, .
1670 [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
1671 Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
1672 .
1674 [RFC8071] Watsen, K., "NETCONF Call Home and RESTCONF Call Home",
1675 RFC 8071, DOI 10.17487/RFC8071, February 2017,
1676 .
1678 [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
1679 BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
1680 .
1682 Appendix A. Change Log
1684 A.1. 00 to 01
1686 o Noted that '0.0.0.0' and '::' might have special meanings.
1688 o Renamed "keychain" to "keystore".
1690 A.2. 01 to 02
1692 o Removed the groupings 'listening-ssh-client-grouping' and
1693 'listening-ssh-server-grouping'. Now modules only contain the
1694 transport-independent groupings.
1696 o Simplified the "client-auth" part in the ietf-ssh-client module.
1697 It now inlines what it used to point to keystore for.
1699 o Added cipher suites for various algorithms into new 'ietf-ssh-
1700 common' module.
1702 A.3. 02 to 03
1704 o Removed 'RESTRICTED' enum from 'password' leaf type.
1706 o Added a 'must' statement to container 'server-auth' asserting that
1707 at least one of the various auth mechanisms must be specified.
1709 o Fixed description statement for leaf 'trusted-ca-certs'.
1711 A.4. 03 to 04
1713 o Change title to "YANG Groupings for SSH Clients and SSH Servers"
1715 o Added reference to RFC 6668
1717 o Added RFC 8174 to Requirements Language Section.
1719 o Enhanced description statement for ietf-ssh-server's "trusted-ca-
1720 certs" leaf.
1722 o Added mandatory true to ietf-ssh-client's "client-auth" 'choice'
1723 statement.
1725 o Changed the YANG prefix for module ietf-ssh-common from 'sshcom'
1726 to 'sshcmn'.
1728 o Removed the compression algorithms as they are not commonly
1729 configurable in vendors' implementations.
1731 o Updating descriptions in transport-params-grouping and the
1732 servers's usage of it.
1734 o Now tree diagrams reference ietf-netmod-yang-tree-diagrams
1736 o Updated YANG to use typedefs around leafrefs to common keystore
1737 paths
1739 o Now inlines key and certificates (no longer a leafref to keystore)
1741 A.5. 04 to 05
1743 o Merged changes from co-author.
1745 A.6. 05 to 06
1747 o Updated to use trust anchors from trust-anchors draft (was
1748 keystore draft)
1750 o Now uses new keystore grouping enabling asymmetric key to be
1751 either locally defined or a reference to the keystore.
1753 A.7. 06 to 07
1755 o factored the ssh-[client|server]-groupings into more reusable
1756 groupings.
1758 o added if-feature statements for the new "ssh-host-keys" and
1759 "x509-certificates" features defined in draft-ietf-netconf-trust-
1760 anchors.
1762 A.8. 07 to 08
1764 o Added a number of compatibility matricies to Section 5 (thanks
1765 Frank!)
1767 o Claified that any configured "host-key-alg" values need to be
1768 compatible with the configured private key.
1770 Acknowledgements
1772 The authors would like to thank for following for lively discussions
1773 on list and in the halls (ordered by last name): Andy Bierman, Martin
1774 Bjorklund, Benoit Claise, Mehmet Ersue, Balazs Kovacs, David
1775 Lamparter, Alan Luchuk, Ladislav Lhotka, Radek Krejci, Tom Petch,
1776 Juergen Schoenwaelder, Phil Shafer, Sean Turner, Michal Vasko, and
1777 Bert Wijnen.
1779 Authors' Addresses
1781 Kent Watsen
1782 Juniper Networks
1784 EMail: kwatsen@juniper.net
1786 Gary Wu
1787 Cisco Systems
1789 EMail: garywu@cisco.com
1791 Liang Xia
1792 Huawei
1794 EMail: frank.xialiang@huawei.com