| Internet-Draft | Conveying a CSR in an SZTP Request | August 2021 |
| Watsen, et al. | Expires 25 February 2022 | [Page] |
This draft extends the "get-bootstrapping-data" RPC defined in RFC 8572 to include an optional certificate signing request (CSR), enabling a bootstrapping device to additionally obtain an identity certificate (e.g., an LDevID, from IEEE 802.1AR) as part of the "onboarding information" response provided in the RPC-reply.¶
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AAAA --> the assigned RFC value for I-D.ietf-netconf-crypto-types¶
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This draft extends the "get-bootstrapping-data" RPC defined in [RFC8572] to include an optional certificate signing request (CSR) [RFC2986], enabling a bootstrapping device to additionally obtain an identity certificate (e.g., an LDevID [Std-802.1AR-2018]) as part of the "onboarding information" response provided in the RPC-reply.¶
The ability to provision an identity certificate that is purpose-built for a production environment during the bootstrapping process removes reliance on the manufacturer CA, and it also enables the bootstraped device to join the production environment with an appropriate identity and other attributes in its LDevID certificate.¶
Two YANG [RFC7950] modules are defined. The "ietf-ztp-types" module defines three YANG groupings for the various messages defined in this document. The "ietf-sztp-csr" module augments two groupings into the "get-bootstrapping-data" RPC and defines a YANG Data Structure [RFC8791] around the third grouping.¶
This document uses the following terms from [RFC8572]:¶
This document defines the following new terms:¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
Various examples used in this document use a placeholder value for binary data that has been base64 encoded (e.g., "BASE64VALUE="). This placeholder value is used as real base64 encoded structures are often many lines long and hence distracting to the example being presented.¶
The "ietf-sztp-csr" module is a YANG 1.1 [RFC7950] module that augments the "ietf-sztp-bootstrap-server" module defined in [RFC8572] and defines a YANG "structure" that is to be conveyed in the "error-info" node defined in Section 7.1 of [RFC8040].¶
The following tree diagram [RFC8340] illustrates the "ietf-sztp-csr" module.¶
module: ietf-sztp-csr
augment /sztp-svr:get-bootstrapping-data/sztp-svr:input:
+---w (msg-type)?
+--:(csr-support)
| +---w csr-support
| +---w key-generation!
| | +---w supported-algorithms
| | +---w algorithm-identifier* binary
| +---w csr-generation
| +---w supported-formats
| +---w format-identifier* identityref
+--:(csr)
+---w (csr-type)
+--:(p10-csr)
| +---w p10-csr? ct:csr
+--:(cmc-csr)
| +---w cmc-csr? binary
+--:(cmp-csr)
+---w cmp-csr? binary
structure: csr-request
+--ro key-generation!
| +--ro selected-algorithm
| +--ro algorithm-identifier binary
+--ro csr-generation
| +--ro selected-format
| +--ro format-identifier identityref
+--ro cert-req-info? ietf-crypto-types:csr-info
¶
The augmentation defines two kinds of parameters that an SZTP-client can send to an SZTP-server. The YANG structure defines one collection of parameters that an SZTP-server can send to an SZTP-client.¶
In the order of their intended use:¶
To further illustrate how the augmentation and structure defined by the "ietf-sztp-csr" module are used, below are two additional tree diagrams showing these nodes placed where they are used.¶
The following tree diagram [RFC8340] illustrates SZTP's "get-bootstrapping-data" RPC with the augmentation in place.¶
=============== NOTE: '\' line wrapping per RFC 8792 ================
module: ietf-sztp-bootstrap-server
rpcs:
+---x get-bootstrapping-data
+---w input
| +---w signed-data-preferred? empty
| +---w hw-model? string
| +---w os-name? string
| +---w os-version? string
| +---w nonce? binary
| +---w (sztp-csr:msg-type)?
| +--:(sztp-csr:csr-support)
| | +---w sztp-csr:csr-support
| | +---w sztp-csr:key-generation!
| | | +---w sztp-csr:supported-algorithms
| | | +---w sztp-csr:algorithm-identifier* bina\
ry
| | +---w sztp-csr:csr-generation
| | +---w sztp-csr:supported-formats
| | +---w sztp-csr:format-identifier* identit\
yref
| +--:(sztp-csr:csr)
| +---w (sztp-csr:csr-type)
| +--:(sztp-csr:p10-csr)
| | +---w sztp-csr:p10-csr? ct:csr
| +--:(sztp-csr:cmc-csr)
| | +---w sztp-csr:cmc-csr? binary
| +--:(sztp-csr:cmp-csr)
| +---w sztp-csr:cmp-csr? binary
+--ro output
+--ro reporting-level? enumeration {onboarding-server}?
+--ro conveyed-information cms
+--ro owner-certificate? cms
+--ro ownership-voucher? cms
¶
The following tree diagram [RFC8340] illustrates RESTCONF's "errors" RPC-reply message with the "csr-request" structure in place.¶
module: ietf-restconf
+--ro errors
+--ro error* []
+--ro error-type enumeration
+--ro error-tag string
+--ro error-app-tag? string
+--ro error-path? instance-identifier
+--ro error-message? string
+--ro error-info
+--ro csr-request
+--ro key-generation!
| +--ro selected-algorithm
| +--ro algorithm-identifier binary
+--ro csr-generation
| +--ro selected-format
| +--ro format-identifier identityref
+--ro cert-req-info? ct:csr-info
¶
An SZTP-client implementing this specification would signal to the bootstrap server its willingness to generate a CSR by including the "csr-support" node in its "get-bootstrapping-data" RPC, as illustrated below.¶
REQUEST¶
=============== NOTE: '\' line wrapping per RFC 8792 ================
POST /restconf/operations/ietf-sztp-bootstrap-server:get-bootstrappi\
ng-data HTTP/1.1
HOST: example.com
Content-Type: application/yang.data+json
{
"ietf-sztp-bootstrap-server:input" : {
"hw-model": "model-x",
"os-name": "vendor-os",
"os-version": "17.3R2.1",
"nonce": "extralongbase64encodedvalue=",
"ietf-sztp-csr:csr-support": {
"key-generation": {
"supported-algorithms": {
"algorithm-identifier": [
"BASE64VALUE1",
"BASE64VALUE2",
"BASE64VALUE3"
]
}
},
"csr-generation": {
"supported-formats": {
"format-identifier": [
"ietf-ztp-types:p10-csr",
"ietf-ztp-types:cmc-csr",
"ietf-ztp-types:cmp-csr"
]
}
}
}
}
}
¶
Assuming the SZTP-server wishes to prompt the SZTP-client to provide a CSR, then it would respond with an HTTP 400 Bad Request error code:¶
RESPONSE¶
HTTP/1.1 400 Bad Request
Date: Sat, 31 Oct 2015 17:02:40 GMT
Server: example-server
Content-Type: application/yang.data+json
{
"ietf-restconf:errors" : {
"error" : [
{
"error-type": "application",
"error-tag": "missing-attribute",
"error-message": "Missing input parameter",
"error-info": {
"ietf-sztp-csr:csr-request": {
"key-generation": {
"selected-algorithm": {
"algorithm-identifier": "BASE64VALUE="
}
},
"csr-generation": {
"selected-format": {
"format-identifier": "ietf-ztp-types:p10-csr"
}
},
"cert-req-info": "BASE64VALUE="
}
}
}
]
}
}
¶
Upon being prompted to provide a CSR, the SZTP-client would POST another "get-bootstrapping-data" request, but this time including one of the "csr" nodes to convey its CSR to the SZTP-server:¶
REQUEST¶
=============== NOTE: '\' line wrapping per RFC 8792 ================
POST /restconf/operations/ietf-sztp-bootstrap-server:get-bootstrappi\
ng-data HTTP/1.1
HOST: example.com
Content-Type: application/yang.data+json
{
"ietf-sztp-bootstrap-server:input" : {
"hw-model": "model-x",
"os-name": "vendor-os",
"os-version": "17.3R2.1",
"nonce": "extralongbase64encodedvalue=",
"ietf-sztp-csr:p10-csr": "BASE64VALUE="
}
}
¶
At this point, it is expected that the SZTP-server, perhaps in conjunction with other systems, such as a backend CA or RA, will validate the CSR's origin and proof-of-possession and, assuming the CSR is approved, issue a signed certificate for the bootstrapping device.¶
The SZTP-server responds with "onboarding-information" (encoded inside the "conveyed-information" node, shown below) containing a signed identity certificate for the CSR provided by the SZTP-client:¶
RESPONSE¶
HTTP/1.1 200 OK
Date: Sat, 31 Oct 2015 17:02:40 GMT
Server: example-server
Content-Type: application/yang.data+json
{
"ietf-sztp-bootstrap-server:output" : {
"reporting-level": "verbose",
"conveyed-information": "BASE64VALUE="
}
}
¶
How the signed certificate is conveyed inside the onboarding information is outside the scope of this document. Some implementations may choose to convey it inside a script (e.g., SZTP's "pre-configuration-script"), while other implementations may choose to convey it inside the SZTP "configuration" node. SZTP onboarding information is described in Section 2.2 of [RFC8572].¶
Following are two examples of conveying the signed certificate inside the "configuration" node. Both examples assume that the SZTP-client understands the "ietf-keystore" module defined in [I-D.ietf-netconf-keystore].¶
This first example illustrates the case where the signed certificate is for the same asymmetric key used by the SZTP-client's manufacturer-generated identity certificate (e.g., an IDevID, from [Std-802.1AR-2018]). As such, the configuration needs to associate the newly signed certificate with the existing asymmetric key:¶
=============== NOTE: '\' line wrapping per RFC 8792 ================
{
"ietf-keystore:keystore": {
"asymmetric-keys": {
"asymmetric-key": [
{
"name": "Manufacturer-Generated Hidden Key",
"public-key-format": "ietf-crypto-types:subject-public-key\
-info-format",
"public-key": "BASE64VALUE=",
"hidden-private-key": [null],
"certificates": {
"certificate": [
{
"name": "Manufacturer-Generated IDevID Cert",
"cert-data": "BASE64VALUE="
},
{
"name": "Newly-Generated LDevID Cert",
"cert-data": "BASE64VALUE="
}
]
}
}
]
}
}
}
¶
This second example illustrates the case where the signed certificate is for a newly generated asymmetric key. As such, the configuration needs to associate the newly signed certificate with the newly generated asymmetric key:¶
=============== NOTE: '\' line wrapping per RFC 8792 ================
{
"ietf-keystore:keystore": {
"asymmetric-keys": {
"asymmetric-key": [
{
"name": "Manufacturer-Generated Hidden Key",
"public-key-format": "ietf-crypto-types:subject-public-key\
-info-format",
"public-key": "BASE64VALUE=",
"hidden-private-key": [null],
"certificates": {
"certificate": [
{
"name": "Manufacturer-Generated IDevID Cert",
"cert-data": "BASE64VALUE="
}
]
}
},
{
"name": "Newly-Generated Hidden Key",
"public-key-format": "ietf-crypto-types:subject-public-key\
-info-format",
"public-key": "BASE64VALUE=",
"hidden-private-key": [null],
"certificates": {
"certificate": [
{
"name": "Newly-Generated LDevID Cert",
"cert-data": "BASE64VALUE="
}
]
}
}
]
}
}
}
¶
In addition to configuring the signed certificate, it is often necessary to also configure the Issuer's signing certificate so that the device (i.e., STZP-client) can authenticate certificates presented by peer devices signed by the same issuer as its own. While outside the scope of this document, one way to do this would be to use the "ietf-truststore" module defined in [I-D.ietf-netconf-trust-anchors].¶
This module augments an RPC defined in [RFC8572]. The module uses a data types and groupings defined in [RFC8572], [RFC8791], and [I-D.ietf-netconf-crypto-types]. The module has additional normative references to [RFC2986], [RFC5272], [RFC4210], and [ITU.X690.2015], and an informative reference to [Std-802.1AR-2018].¶
<CODE BEGINS> file "ietf-sztp-csr@2021-08-24.yang"¶
module ietf-sztp-csr {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-sztp-csr";
prefix sztp-csr;
import ietf-sztp-bootstrap-server {
prefix sztp-svr;
reference
"RFC 8572: Secure Zero Touch Provisioning (SZTP)";
}
import ietf-yang-structure-ext {
prefix sx;
reference
"RFC 8791: YANG Data Structure Extensions";
}
import ietf-ztp-types {
prefix zt;
reference
"RFC XXXX: Conveying a Certificate Signing Request (CSR)
in a Secure Zero Touch Provisioning (SZTP)
Bootstrapping Request";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: http://tools.ietf.org/wg/netconf
WG List: <mailto:netconf@ietf.org>
Authors: Kent Watsen <mailto:kent+ietf@watsen.net>
Russ Housley <mailto:housley@vigilsec.com>
Sean Turner <mailto:sean@sn3rd.com>";
description
"This module augments the 'get-bootstrapping-data' RPC,
defined in the 'ietf-sztp-bootstrap-server' module from
SZTP (RFC 8572), enabling the SZTP-client to obtain a
signed identity certificate (e.g., an LDevID from IEEE
802.1AR) as part of the SZTP onboarding information
response.
Copyright (c) 2021 IETF Trust and the persons identified
as authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with
or without modification, is permitted pursuant to, and
subject to the license terms contained in, the Simplified
BSD License set forth in Section 4.c of the IETF Trust's
Legal Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC
itself for full legal notices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this
document are to be interpreted as described in BCP 14
(RFC 2119) (RFC 8174) when, and only when, they appear
in all capitals, as shown here.";
revision 2021-08-24 {
description
"Initial version";
reference
"RFC XXXX: Conveying a Certificate Signing Request (CSR)
in a Secure Zero Touch Provisioning (SZTP)
Bootstrapping Request";
}
// Protocol-accessible nodes
augment "/sztp-svr:get-bootstrapping-data/sztp-svr:input" {
description
"This augmentation adds the 'csr-support' and 'csr' nodes to
the SZTP (RFC 8572) 'get-bootstrapping-data' request message,
enabling the SZTP-client to obtain an identity certificate
(e.g., an LDevID from IEEE 802.1AR) as part of the onboarding
information response provided by the SZTP-server.
The 'csr-support' node enables the SZTP-client to indicate
that it supports generating certificate signing requests
(CSRs), and to provide details around the CSRs it is able
to generate.
The 'csr' node enables the SZTP-client to relay a CSR to
the SZTP-server.";
reference
"IEEE 802.1AR: IEEE Standard for Local and metropolitan
area networks - Secure Device Identity
RFC 8572: Secure Zero Touch Provisioning (SZTP)";
choice msg-type {
description
"Messages are mutually exclusive.";
case csr-support {
description
"Indicates how the SZTP-client supports generating CSRs.
If present and a SZTP-server wishes to request the
SZTP-client generate a CSR, the SZTP-server MUST
respond with HTTP code 400 Bad Request with an
'ietf-restconf:errors' message having the 'error-tag'
value 'missing-attribute' and the 'error-info' node
containing the 'csr-request' structure described
in this module.";
uses zt:csr-support-grouping;
}
case csr {
description
"Provides the CSR generated by the SZTP-client.
When present, the SZTP-server SHOULD respond with
an SZTP onboarding information message containing
a signed certificate for the conveyed CSR. The
SZTP-server MAY alternatively respond with another
HTTP error containing another 'csr-request', in
which case the SZTP-client MUST invalidate the
previously generated CSR.";
uses zt:csr-grouping;
}
}
}
sx:structure csr-request {
description
"A YANG data structure, per RFC 8791, that specifies
details for the CSR that the ZTP-client is to generate.";
reference
"RFC 8791: YANG Data Structure Extensions";
uses zt:csr-request-grouping;
}
}
¶
<CODE ENDS>¶
This section defines a YANG 1.1 [RFC7950] module that defines three YANG groupings, one each for messages sent between a ZTP-client and ZTP-server. This module is defines independently of the "ietf-sztp-csr" module so that it's groupings may be used by bootstrapping protocols other than SZTP [RFC8572].¶
The following tree diagram [RFC8340] illustrates the three groupings defined in the "ietf-ztp-types" module.¶
module: ietf-ztp-types
grouping csr-support-grouping
+-- csr-support
+-- key-generation!
| +-- supported-algorithms
| +-- algorithm-identifier* binary
+-- csr-generation
+-- supported-formats
+-- format-identifier* identityref
grouping csr-request-grouping
+-- key-generation!
| +-- selected-algorithm
| +-- algorithm-identifier binary
+-- csr-generation
| +-- selected-format
| +-- format-identifier identityref
+-- cert-req-info? ct:csr-info
grouping csr-grouping
+-- (csr-type)
+--:(p10-csr)
| +-- p10-csr? ct:csr
+--:(cmc-csr)
| +-- cmc-csr? binary
+--:(cmp-csr)
+-- cmp-csr? binary
¶
This module uses a data types and groupings [RFC8791] and [I-D.ietf-netconf-crypto-types]. The module has additional normative references to [RFC2986], [RFC4210], [RFC5272], and [ITU.X690.2015], and an informative reference to [Std-802.1AR-2018].¶
<CODE BEGINS> file "ietf-ztp-types@2021-08-24.yang"¶
module ietf-ztp-types {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-ztp-types";
prefix zt;
import ietf-crypto-types {
prefix ct;
reference
"RFC AAAA: YANG Data Types and Groupings for Cryptography";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: http://tools.ietf.org/wg/netconf
WG List: <mailto:netconf@ietf.org>
Authors: Kent Watsen <mailto:kent+ietf@watsen.net>
Russ Housley <mailto:housley@vigilsec.com>
Sean Turner <mailto:sean@sn3rd.com>";
description
"This module defines three groupings that enable
bootstrapping devices to 1) indicate if and how they
support generating CSRs, 2) obtain a request to
generate a CSR, and 3) communicate the requested CSR.
The terms 'IDevID' and 'LDevID' are used herein to
mean 'initial device identifier' and 'local device
identifer'. These terms are defined consistent with
the IEEE 802.1AR specification, though there is no
requirement that a ZTP-client's identity certificate
conform to IEEE 802.1AR.
Copyright (c) 2021 IETF Trust and the persons identified
as authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with
or without modification, is permitted pursuant to, and
subject to the license terms contained in, the Simplified
BSD License set forth in Section 4.c of the IETF Trust's
Legal Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC
itself for full legal notices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this
document are to be interpreted as described in BCP 14
(RFC 2119) (RFC 8174) when, and only when, they appear
in all capitals, as shown here.";
revision 2021-08-24 {
description
"Initial version";
reference
"RFC XXXX: Conveying a Certificate Signing Request (CSR)
in a Secure Zero Touch Provisioning (SZTP)
Bootstrapping Request";
}
identity certificate-request-format {
description
"A base identity for the request formats supported
by the ZTP-client.
Additional derived identities MAY be defined by
future efforts.";
}
identity p10-csr {
base certificate-request-format;
description
"Indicates that the ZTP-client supports generating
requests using the 'CertificationRequest' structure
defined in RFC 2986.";
reference
"RFC 2986: PKCS #10: Certification Request Syntax
Specification Version 1.7";
}
identity cmp-csr {
base certificate-request-format;
description
"Indicates that the ZTP-client supports generating
requests using a constrained version of the PKIMessage
containing a p10cr structure defined in RFC 4210.";
reference
"RFC 4210: Internet X.509 Public Key Infrastructure
Certificate Management Protocol (CMP)";
}
identity cmc-csr {
base certificate-request-format;
description
"Indicates that the ZTP-client supports generating
requests using a constrained version of the 'Full
PKI Request' structure defined in RFC 5272.";
reference
"RFC 5272: Certificate Management over CMS (CMC)";
}
// Protocol-accessible nodes
grouping csr-support-grouping {
description
"A grouping enabling use by other efforts.";
container csr-support {
description
"Enables a ZTP-client to indicate that it supports
generating certificate signing requests (CSRs) and
provides details about the CSRs it is able to
generate.";
container key-generation {
presence
"Indicates that the ZTP-client is capable of
generating a new asymmetric key pair.
If this node is not present, the ZTP-server MAY
request a CSR using the asymmetric key associated
with the device's existing identity certificate
(e.g., an IDevID from IEEE 802.1AR).";
description
"Specifies details for the ZTP-client's ability to
generate a new asymmetric key pair.";
container supported-algorithms {
description
"A list of public key algorithms supported by the
ZTP-client for generating a new asymmetric key.";
leaf-list algorithm-identifier {
type binary;
min-elements 1;
description
"An AlgorithmIdentifier, as defined in RFC 2986,
encoded using ASN.1 distinguished encoding rules
(DER), as specified in ITU-T X.690.";
reference
"RFC 2986: PKCS #10: Certification Request Syntax
Specification Version 1.7
ITU-T X.690:
Information technology - ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER),
Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER).";
}
}
}
container csr-generation {
description
"Specifies details for the ZTP-client's ability to
generate a certificate signing requests.";
container supported-formats {
description
"A list of certificate request formats supported
by the ZTP-client for generating a new key.";
leaf-list format-identifier {
type identityref {
base zt:certificate-request-format;
}
min-elements 1;
description
"A certificate request format supported by the
ZTP-client.";
}
}
}
}
}
grouping csr-request-grouping {
description
"A grouping enabling use by other efforts.";
container key-generation {
presence
"Provided by a ZTP-server to indicate that it wishes
the ZTP-client to generate a new asymmetric key.
This statement is present so the mandatory descendant
nodes do not imply that this node must be configured.";
description
"The key generation parameters selected by the ZTP-server.
This leaf MUST only appear if the ZTP-client's
'csr-support' included the 'key-generation' node.";
container selected-algorithm {
description
"The key algorithm selected by the ZTP-server. The
algorithm MUST be one of the algorithms specified by
the 'supported-algorithms' node in the ZTP-client's
message containing the 'csr-support' structure.";
leaf algorithm-identifier {
type binary;
mandatory true;
description
"An AlgorithmIdentifier, as defined in RFC 2986,
encoded using ASN.1 distinguished encoding rules
(DER), as specified in ITU-T X.690.";
reference
"RFC 2986: PKCS #10: Certification Request Syntax
Specification Version 1.7
ITU-T X.690:
Information technology - ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER),
Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER).";
}
}
}
container csr-generation {
description
"Specifies details for the CSR that the ZTP-client
is to generate.";
container selected-format {
description
"The CSR format selected by the ZTP-server. The
format MUST be one of the formats specified by
the 'supported-formats' node in the ZTP-client's
request message.";
leaf format-identifier {
type identityref {
base zt:certificate-request-format;
}
mandatory true;
description
"A certificate request format to be used by the
ZTP-client.";
}
}
}
leaf cert-req-info {
type ct:csr-info;
description
"A CertificationRequestInfo structure, as defined in
RFC 2986, and modeled via a 'typedef' statement by
RFC AAAA.
Enables the ZTP-server to provide a fully-populated
CertificationRequestInfo structure that the ZTP-client
only needs to sign in order to generate the complete
'CertificationRequest' structure to send to ZTP-server
in its next 'get-bootstrapping-data' request message.
When provided, the ZTP-client SHOULD use this
structure to generate its CSR; failure to do so MAY
result in a 400 Bad Request response containing
another 'csr-request' structure.
When not provided, the ZTP-client SHOULD generate a
CSR using the same structure defined in its existing
identity certificate (e.g., IDevID).
It is an error if the 'AlgorithmIdentifier' field
contained inside the 'SubjectPublicKeyInfo' field
does not match the algorithm identified by the
'selected-algorithm' node.";
reference
"RFC 2986:
PKCS #10: Certification Request Syntax Specification
RFC AAAA:
YANG Data Types and Groupings for Cryptography";
}
}
grouping csr-grouping {
description
"Enables a ZTP-client to convey a certificate signing
request, using the encoding format selected by a
ZTP-server's 'csr-request' response to the ZTP-client's
previously sent 'get-bootstrapping-data' request
containing the 'csr-support' node.";
choice csr-type {
mandatory true;
description
"A choice amongst certificate signing request formats.
Additional formats MAY be augmented into this 'choice'
statement by future efforts.";
case p10-csr {
leaf p10-csr {
type ct:csr;
description
"A CertificationRequest structure, per RFC 2986.";
reference
"RFC 2986: PKCS #10: Certification
Request Syntax Specification";
}
}
case cmc-csr {
leaf cmc-csr {
type binary;
description
"A constrained version of the 'Full PKI Request'
message defined in RFC 5272, encoded using ASN.1
distinguished encoding rules (DER), as specified
in ITU-T X.690.
For asymmetric key-based origin authentication of
a CSR based on the IDevID's private key for the
associated IDevID's public key, the PKIData
contains one reqSequence element and no cmsSequence
or otherMsgSequence elements. The reqSequence is
the TaggedRequest and it is the tcr CHOICE. The
tcr is the TaggedCertificationRequest and it a
bodyPartId and the certificateRequest elements.
The certificateRequest is signed with the IDevID's
private key. The IDevID certificate and optionally
its certificate chain is included in the SignedData
certificates that encapsulates the PKIData.
For asymmetric key-based origin authentication
based on the IDevID's private key that signs the
encapsulated CSR signed by the LDevID's private key,
the PKIData contains one cmsSequence element and no
otherMsgSequence element. The cmsSequence is the
TaggedContentInfo and it includes a bodyPartID
element and a contentInfo. The contentInfo is
a SignedData encapsulating a PKIData with one
reqSequence element and no cmsSequence or
otherMsgSequence elements. The reqSequence is
the TaggedRequest and it is the tcr CHOICE. The
tcr is the TaggedCertificationRequest and it a
bodyPartId and the certificateRequest elements.
The certificateRequest is signed with the LDevID's
private key. The IDevID certificate and optionally
its certificate chain is included in the SignedData
certificates that encapsulates the PKIData.
For shared secret-based origin authentication of a
CSR signed by the LDevID's private key, the PKIData
contains one cmsSequence element and no reqSequence
or otherMsgSequence elements. The cmsSequence is
the TaggedContentInfo and it includes a bodyPartID
element and a contentInfo. The contentInfo is an
AuthenticatedData encapsulating a PKIData with one
reqSequence element and no cmsSequences or
otherMsgSequence elements. The reqSequence is the
TaggedRequest and it is the tcr CHOICE. The tcr is
the TaggedCertificationRequest and it a bodyPartId
and the certificateRequest elements. The
certificateRequest is signed with the LDevID's
private key. The IDevID certificate and optionally
its certificate chain is included in the SignedData
certificates that encapsulates the PKIData.";
reference
"RFC 5272: Certificate Management over CMS (CMC)
ITU-T X.690:
Information technology - ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER),
Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER).";
}
}
case cmp-csr {
leaf cmp-csr {
type binary;
description
"A PKIMessage structure, as defined in RFC 4210,
encoded using ASN.1 distinguished encoding rules
(DER), as specified in ITU-T X.690.
For asymmetric key-based origin authentication of
a CSR based on the IDevID's private key for the
associated IDevID's public key, PKIMessages
contains one PKIMessage with the header and body
elements, no protection element, and should contain
the extraCerts element. The header element contains
the pvno, sender, and recipient elements. The pvno
contains cmp2000, and the sender contains the
subject of the IDevID certificate. The body element
contains a p10cr CHOICE of type CertificationRequet.
It is signed with the IDevID's private key. The
extraCerts element contains the IDevID certificate,
optionally followed by its certificate chain
excluding the trust anchor.
For asymmetric key-based origin authentication
based on the IDevID's private key that signs the
encapsulated CSR signed by the LDevID's private
key, PKIMessages contains one PKIMessage with the
header, body, and protection elements, and should
contain the extraCerts element. The header element
contains the pvno, sender, recipient, protectionAlg,
and optionally senderKID elements. The pvno contains
cmp2000, the sender contains the subject of the
IDevID certificate, the protectionAlg contains the
AlgorithmIdentifier of the used signature algorithm,
and the senderKID contains the subject key
identifier of the IDevID certificate. The body
element contains a p10cr CHOICE of type
CertificationRequet. It is signed with the LDevID's
private key. The protection element contains the
digital signature generated with the IDevID's
private key. The extraCerts element contains the
IDevID certificate, optionally followed by its
certificate chain excluding the trust anchor.
For shared secret-based origin authentication of a
CSR signed by the LDevID's private key, PKIMessages
contains one PKIMessage with the header, body, and
protection element, and no extraCerts element. The
header element contains the pvno, sender, recipient,
protectionAlg, and senderKID elements. The pvno
contains cmp2000, the protectionAlg contains the
AlgorithmIdentifier of the used MAC algorithm, and
the senderKID contains a reference the recipient
can use to identify the shared secret. The body
element contains a p10cr CHOICE of type
CertificationRequet. It is signed with the LDevID's
private key. The protection element contains the
MAC value generated with the shared secret.";
reference
"RFC 4210:
Internet X.509 Public Key Infrastructure
Certificate Management Protocol (CMP)
ITU-T X.690:
Information technology - ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER),
Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER).";
}
}
}
}
}
¶
<CODE ENDS>¶
This document builds on top of the solution presented in [RFC8572] and therefore all the Security Considerations discussed in RFC 8572 apply here as well.¶
The private key the SZTP-client uses for the dynamically-generated identity certificate MUST be protected from inadvertent disclosure in order to prevent identity fraud.¶
The security of this private key is essential in order to ensure the associated identity certificate can be used as a root of trust.¶
It is RECOMMENDED that devices are manufactured with an HSM (hardware security module), such as a TPM (trusted platform module), to generate and forever contain the private key within the security perimeter of the HSM. In such cases, the private key, and its associated certificates, MAY have long validity periods.¶
In cases where the SZTP-client does not possess an HSM, or otherwise is unable to use an HSM for the private key, it is RECOMMENDED to regenerate the private key (and associated identity certificates) periodically. Details for how to generate a new private key and associate a new identity certificate are outside the scope of this document.¶
It is RECOMMENDED that a new private key is generated for each CSR described in this document.¶
This private key SHOULD be protected as well as the built-in private key associated with the SZTP-client's initial device identity certificate (e.g., the IDevID, from [Std-802.1AR-2018]).¶
In cases where it is not possible to generate a new private key that is protected as well as the built-in private key, it is RECOMMENDED to reuse the built-in private key rather than generate a new private key that is not as well protected.¶
This RFC enables an SZTP-client to announce an ability to generate a new key to use for its CSR.¶
When the SZTP-server responds with a request for the SZTP-client to generate a new key, it is essential that the SZTP-client actually generates a new key.¶
Generating a new key each time enables the random bytes used to create the key to also serve the dual-purpose of acting like a "nonce" used in other mechanisms to detect replay attacks.¶
When a fresh public/private key pair is generated for the request, confirmation to the SZTP-client that the response has not been replayed is enabled by the SZTP-client's fresh public key appearing in the signed certificate provided by the SZTP-server.¶
When a public/private key pair associated with the manufacturer-generated identity certificate (e.g., IDevID) is used for the request, there may not be confirmation to the SZTP-client that the response has not been replayed; however, the worst case result is a lost certificate that is associated to the private key known only to the SZTP-client.¶
[RFC8572] allows SZTP-clients to connect to untrusted SZTP-servers, by blindly authenticating the SZTP-server's TLS end-entity certificate.¶
As is discussed in Section 9.5 of [RFC8572], in such cases the SZTP-client MUST assert that the bootstrapping data returned is signed, if the SZTP-client is to trust it.¶
However, the HTTP error message used in this document cannot be signed data, as described in RFC 8572.¶
Therefore, the solution presented in this document cannot be used when the SZTP-client connects to an untrusted SZTP-server.¶
Consistent with the recommendation presented in Section 9.6 of [RFC8572], SZTP-clients SHOULD NOT pass the "csr-support" input parameter to an untrusted SZTP-server. SZTP-clients SHOULD pass instead the "signed-data-preferred" input parameter, as discussed in Appendix B of [RFC8572].¶
A The CSR's origin SHOULD be verified before a certificate is issued.¶
When generating a new key, it is important that the SZTP-client be able to provide additional proof that it was the entity that generated the key.¶
The CMP and CMC certificate request formats defined in this document support origin authentication. A raw PKCS#10 does not support origin authentication.¶
The CMP and CMC request formats support origin authentication using both PKI and shared secret.¶
Typically, only one possible origin authentication mechanism can possibly be used but, in the case that the SZTP-client authenticates itself using both TLS-level (e.g., IDevID) and HTTP-level credentials (e.g., Basic), as is allowed by Section 5.3 of [RFC8572], then the SZTP-client may need to choose between the two options.¶
In the case that the SZTP-client must choose between an asymmetric key option versus a shared secret for origin authentication, it is RECOMMENDED that the SZTP-client choose using the asymmetric key.¶
Unlike a manufacturer-generated identity certificate (e.g., IDevID), the deployment-generated identity certificate (e.g., LDevID) and the associated private key (assuming a new private key was generated for the purpose), are considered user data and SHOULD be cleared whenever the SZTP-client is reset to its factory default state, such as by the "factory-reset" RPC defined in [I-D.ietf-netmod-factory-default].¶
When the bootstrapping device's manufacturer-generated private key (e.g., the IDevID key) is reused for the CSR, proof-of-possession is verified by ensuring the CSR was signed by that key.¶
When a new asymmetric key is used, proof-of-possession may be verified, with the CMP or CMC formats, by ensuring the parent ASN.1 structure containing the CSR is signed by the manufacturer-generated key.¶
[RFC8572] allows SZTP-clients to connect to untrusted SZTP-servers, by blindly authenticating the SZTP-server's TLS end-entity certificate.¶
As is recommended in Section 4.1.4 in this document, in such cases, SZTP-clients SHOULD pass the "signed-data-preferred" input parameter.¶
The reciprocal of this statement is that SZTP-servers, wanting to support SZTP-clients that don't trust them, SHOULD support the "signed-data-preferred" input parameter, as discussed in Appendix B of [RFC8572].¶
The recommended format for documenting the Security Considerations for YANG modules is described in Section 3.7 of [RFC8407]. However, this module only augments two input parameters into the "get-bootstrapping-data" RPC in [RFC8572], and therefore only needs to point to the relevant Security Considerations sections in that RFC.¶
The recommended format for documenting the Security Considerations for YANG modules is described in Section 3.7 of [RFC8407]. However, this module does not define any protocol-accessible nodes (it only defines "identity" and "grouping" statements) and therefore there are no Security considerations to report.¶
This document registers two URIs in the "ns" subregistry of the IETF XML Registry [RFC3688] maintained at https://www.iana.org/assignments/xml-registry/xml-registry.xhtml#ns. Following the format in [RFC3688], the following registrations are requested:¶
URI: urn:ietf:params:xml:ns:yang:ietf-sztp-csr Registrant Contact: The NETCONF WG of the IETF. XML: N/A, the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-ztp-types Registrant Contact: The NETCONF WG of the IETF. XML: N/A, the requested URI is an XML namespace.¶
This document registers two YANG modules in the YANG Module Names registry [RFC6020] maintained at https://www.iana.org/assignments/yang-parameters/yang-parameters.xhtml. Following the format defined in [RFC6020], the below registrations are requested:¶
name: ietf-sztp-csr namespace: urn:ietf:params:xml:ns:yang:ietf-sztp-csr prefix: sztp-csr reference: RFC XXXX name: ietf-ztp-types namespace: urn:ietf:params:xml:ns:yang:ietf-ztp-types prefix: ztp-types reference: RFC XXXX¶
The authors would like to thank for following for lively discussions on list and in the halls (ordered by first name): David von Oheimb, Hendrik Brockhaus, Guy Fedorkow, Joe Clarke, Rich Salz, Rob Wilton, and Qin Wu.¶
Special thanks goes to David von Oheimb and Hendrik Brockhaus for helping with the descriptions for the "cmc-csr" and "cmp-csr" nodes.¶