Conveying a Certificate Signing Request (CSR) in a Secure Zero Touch Provisioning (SZTP) Bootstrapping RequestWatsen Networkskent+ietf@watsen.netVigil Security, LLChousley@vigilsec.comsn3rdsean@sn3rd.com
Operations
NETCONF Working Groupzerotouchbootstrapsztpztpcsrpkcs#10p10p10crcmccmpThis draft extends the input to 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.Editorial Note (To be removed by RFC Editor)This draft contains many placeholder values that need to be replaced
with finalized values at the time of publication. This note summarizes
all of the substitutions that are needed. No other
RFC Editor instructions are specified elsewhere in this document.Artwork in this document contains shorthand references to drafts in
progress. Please apply the following replacements:
XXXX --> the assigned numerical RFC value for this draft
AAAA --> the assigned RFC value for I-D.ietf-netconf-crypto-types
Artwork in this document contains a placeholder value for the publication date of this
draft. Please apply the following replacement:
2022-03-02 --> the publication date of this draft
This document contains references to other drafts in progress, both in
the Normative References section, as well as in body text throughout.
Please update the following references to reflect their final RFC assignments:
I-D.ietf-netconf-crypto-types
I-D.ietf-netconf-keystore
I-D.ietf-netconf-trust-anchors
IntroductionOverviewThis draft extends the input to the "get-bootstrapping-data" RPC defined in
to include an optional certificate
signing request (CSR) , enabling a
bootstrapping device to additionally obtain an identity
certificate (e.g., an LDevID )
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
bootstrapped device to join the production environment with an
appropriate identity and other attributes in its identity
certificate (e.g., an LDevID).Two YANG 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
around the third grouping.TerminologyThis document uses the following terms from :
Bootstrap Server
Bootstrapping Data
Conveyed Information
Device
Manufacturer
Onboarding Information
Signed Data
This document defines the following new terms:
SZTP-client
The term "SZTP-client" refers to a "device" that is using a
"bootstrap server" as a source of "bootstrapping data".
SZTP-server
The term "SZTP-server" is an alternative term for "bootstrap
server" that is symmetric with the "SZTP-client" term.
Requirements LanguageThe 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
when, and only when, they appear in all capitals, as shown here.ConventionsVarious 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" ModuleThe "ietf-sztp-csr" module is a YANG 1.1
module that augments the "ietf-sztp-bootstrap-server" module defined in
and defines a YANG "structure" that is to be
conveyed in the "error-info" node defined in .Data Model OverviewThe following tree diagram illustrates the
"ietf-sztp-csr" module.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:
The "csr-support" node is used by the SZTP-client to signal
to the SZTP-server that it supports the ability to generate CSRs.
This parameter conveys if the SZTP-client is able to generate a
new asymmetric key and, if so, which key algorithms it supports,
as well as conveys what kinds of CSR structures the SZTP-client
is able to generate.
The "csr-request" structure is used by the SZTP-server to request
the SZTP-client to generate a CSR. This structure is used to
select the key algorithm the SZTP-client should use to generate
a new asymmetric key, if supported, the kind of CSR structure
the SZTP-client should generate and, optionally, the content for
the CSR itself.
The various "csr" nodes are used by the SZTP-client to communicate
a CSR to the SZTP-server.
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 illustrates SZTP's
"get-bootstrapping-data" RPC with the augmentation in place.The following tree diagram illustrates RESTCONF's
"errors" RPC-reply message with the "csr-request" structure in place.Example UsageAn 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. In the example below, the SZTP-client additionally
indicates that it is able to generate keys and provides
a list of key algorithms it supports, as well as provide
a list of certificate formats it supports.REQUESTAssuming 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. In the example below, the SZTP-server specifies
that it wishes the SZTP-client to generate a key using a specific
algorithm and generate a PKCS#10-based CSR containing specific
content.RESPONSEUpon 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:REQUESTAt 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:RESPONSEHow 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
.Below 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
.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 ).
As such, the configuration needs to associate the newly signed certificate
with the existing asymmetric key: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: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 .YANG ModuleThis module augments an RPC defined in . The
module uses a data types and groupings defined in ,
, and .
The module also has an informative reference to .<CODE BEGINS> file "ietf-sztp-csr@2022-03-02.yang"
Authors: Kent Watsen
Russ Housley
Sean Turner ";
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) 2022 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 Revised
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 2022-03-02 {
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 delete any key
generated for 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>The "ietf-ztp-types" ModuleThis section defines a YANG 1.1 module
that defines three YANG groupings, one each for messages sent
between a ZTP-client and ZTP-server. This module is defined
independently of the "ietf-sztp-csr" module so that it's
groupings may be used by bootstrapping protocols other than
SZTP .Data Model OverviewThe following tree diagram illustrates
the three groupings defined in the "ietf-ztp-types" module.YANG ModuleThis module uses a data types and groupings
and . The module has
additional normative references to ,
, , and
, and an informative reference
to .<CODE BEGINS> file "ietf-ztp-types@2022-03-02.yang"
Authors: Kent Watsen
Russ Housley
Sean Turner ";
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.
Copyright (c) 2022 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 Revised
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 2022-03-02 {
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 profiled version of the PKIMessage
that MUST contain a PKIHeader followed by a PKIBody
containing only the ir, cr, kur, or 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 profiled 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 MUST use this structure
to generate its CSR; failure to do so will 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., an IDevID from IEEE 802.1AR).
If the 'AlgorithmIdentifier' field contained inside the
certificate 'SubjectPublicKeyInfo' field does not match
the algorithm identified by the 'selected-algorithm' node,
then the client MUST reject the certificate and raise an
error.";
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 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.
Encoding details are defined in the 'ct:csr'
typedef defined in RFC AAAA.
A raw P10 does not support origin authentication in
the CSR structure. External origin authentication
may be provided via the ZTP-client's authentication
to the ZTP-server at the transport layer (e.g., TLS).";
reference
"RFC 2986: PKCS #10: Certification Request Syntax
Specification
RFC AAAA: YANG Data Types and Groupings for
Cryptography";
}
}
case cmc-csr {
leaf cmc-csr {
type binary;
description
"A profiled 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 initial device identity certificate's
private key for the associated identity certificate'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 branch. The tcr is the
TaggedCertificationRequest and it is the bodyPartId
and the certificateRequest elements. The
certificateRequest is signed with the initial device
identity certificate's private key. The initial device
identity 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 initial device identity certificate's private key
that signs the encapsulated CSR signed by the local
device identity certificate'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 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 is the bodyPartId and
the certificateRequest elements. PKIData contains one
cmsSequence element and no controlSequence, reqSequence,
or otherMsgSequence elements. The certificateRequest
is signed with the local device identity certificate's
private key. The initial device identity 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 local device identity certificate'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 is the bodyPartId and the certificateRequest
elements. The certificateRequest is signed with the
local device identity certificate's private key. The
initial device identity 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 initial device identity certificate's
private key for the associated initial device identity
certificate'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 initial device
identity certificate. The body element contains an ir,
cr, kur, or p10cr CHOICE of type CertificationRequest.
It is signed with the initial device identity
certificate's private key. The extraCerts element
contains the initial device identity certificate,
optionally followed by its certificate chain excluding
the trust anchor.
For asymmetric key-based origin authentication based
on the initial device identity certificate's private
key that signs the encapsulated CSR signed by the local
device identity certificate'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 initial device identity
certificate, the protectionAlg contains the
AlgorithmIdentifier of the used signature algorithm,
and the senderKID contains the subject key identifier
of the initial device identity certificate. The body
element contains an ir, cr, kur, or p10cr CHOICE of
type CertificationRequest. It is signed with the local
device identity certificate's private key. The
protection element contains the digital signature
generated with the initial device identity
certificate's private key. The extraCerts element
contains the initial device identity certificate,
optionally followed by its certificate chain excluding
the trust anchor.
For shared secret-based origin authentication of a
CSR signed by the local device identity certificate'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 an ir, cr, kur, or p10cr CHOICE
of type CertificationRequest. It is signed with the
local device identity certificate'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>Security ConsiderationsThis document builds on top of the solution presented in
and therefore all the Security
Considerations discussed in RFC 8572 apply here as well.For the various CSR formats, when using PKCS#10, the security considerations
in apply, when using CMP, the
security considerations in apply
and, when using CMC, the security considerations in
apply.For the various authentication mechanisms, when using
TLS-level authentication, the security considerations in
apply and, when using HTTP-level
authentication, the security considerations in
apply.SZTP-Client ConsiderationsEnsuring the Integrity of Asymmetric Private KeysThe 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 to
authenticate the device it is issued to.It is RECOMMENDED that devices are manufactured with an HSM
(hardware security module), such as a TPM (trusted platform
module), to generate and 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
is unable to use an HSM to protect the private key, it is
RECOMMENDED to periodically reset the private key (and
associated identity certificates) in order to minimize the
lifetime of unprotected private keys. For instance, an NMS
controller/orchestrator application could periodically prompt
the SZTP-client to generate a new private key and provide a
certificate signing request (CSR) or, alternatively, push
both the key and an identity certificate to the SZTP-client
using, e.g., a PKCS #12 message . In another
example, the SZTP-client could be configured to periodically
reset the configuration to its factory default, thus causing
removal of the private key and associated identity certificates
and re-execution of the SZTP protocol.Reuse of a Manufacturer-generated Private KeyIt is RECOMMENDED that a new private key is generated for each
CSR described in this document.Implementations must randomly generate nonces and private keys.
The use of inadequate pseudo-random number generators (PRNGs) to
generate cryptographic keys can result in little or no security.
An attacker may find it much easier to reproduce the PRNG environment
that produced the keys, searching the resulting small set of
possibilities, rather than brute force searching the whole
key space. As an example of predictable random numbers see
CVE-2008-0166 , and some consequences
of low-entropy random numbers are discussed in Mining Your Ps and Qs
. The generation of quality random
numbers is difficult. ,
, BSI AIS 31 ,
BCP 106 , and others offer valuable
guidance in this area.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 ).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.Replay Attack ProtectionThis 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. Protection
of the private-key information is vital to public-key
cryptography. Disclosure of the private-key material to
another entity can lead to masquerades.Connecting to an Untrusted Bootstrap Server allows SZTP-clients to connect
to untrusted SZTP-servers, by blindly authenticating the
SZTP-server's TLS end-entity certificate.As is discussed in ,
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
, 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 .Selecting the Best Origin Authentication MechanismThe origin of the CSR must 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 CSR 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 ,
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.Clearing the Private Key and Associated CertificateUnlike 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
.SZTP-Server ConsiderationsVerifying Proof of PossessionRegardless if using a new asymmetric key or the bootstrapping
device's manufacturer-generated key (e.g., the IDevID key), the
public key is placed in the CSR and the CSR is signed by that
private key. Proof-of-possession of the private key is verified
by ensuring the signature over the CSR using the public key
placed in the CSR.Verifying Proof of OriginWhen the bootstrapping device's manufacturer-generated
private key (e.g., the IDevID key) is reused for the CSR,
proof-of-origin is verified by validating the IDevID-issuer cert
and ensuring that the CSR uses the same key pair.When the bootstrapping device's manufacturer-generated private key
(e.g., an IDevID key from IEEE 802.1AR) is reused for the CSR, proof-of-origin is
verified by validating the IDevID certification path and ensuring that
the CSR uses the same key pair.When a fresh asymmetric key is used with the CMP or CMC formats, the
authentication is part of the protocols, which could employ either
the manufacturer-generated private key or a shared secret. In addition,
CMP and CMC support processing by a RA before the request is passed
to the CA, which allows for more robust handling of errors.Supporting SZTP-Clients that don't trust the SZTP-Server allows SZTP-clients to connect
to untrusted SZTP-servers, by blindly authenticating the
SZTP-server's TLS end-entity certificate.As is recommended in 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 .Security Considerations for the "ietf-sztp-csr" YANG ModuleThe recommended format for documenting the Security
Considerations for YANG modules is described in . However, this module
only augments two input parameters
into the "get-bootstrapping-data" RPC in , and therefore only needs to point
to the relevant Security Considerations sections in
that RFC.
Security considerations for the "get-bootstrapping-data" RPC
are described in .
Security considerations for the "input" parameters passed inside the
"get-bootstrapping-data" RPC are described in .
Security Considerations for the "ietf-ztp-types" YANG ModuleThe recommended format for documenting the Security
Considerations for YANG modules is described in . 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.IANA ConsiderationsThe "IETF XML" RegistryThis document registers two URIs in the "ns" subregistry of
the IETF XML Registry maintained at
.
Following the format in , the following
registrations are requested:The "YANG Module Names" RegistryThis document registers two YANG modules in the YANG Module
Names registry maintained at
.
Following the format defined in , the below
registrations are requested:ReferencesNormative ReferencesKey words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.PKCS #10: Certification Request Syntax Specification Version 1.7This memo represents a republication of PKCS #10 v1.7 from RSA Laboratories' Public-Key Cryptography Standards (PKCS) series, and change control is retained within the PKCS process. The body of this document, except for the security considerations section, is taken directly from the PKCS #9 v2.0 or the PKCS #10 v1.7 document. This memo provides information for the Internet community.The IETF XML RegistryThis document describes an IANA maintained registry for IETF standards which use Extensible Markup Language (XML) related items such as Namespaces, Document Type Declarations (DTDs), Schemas, and Resource Description Framework (RDF) Schemas.Internet X.509 Public Key Infrastructure Certificate Management Protocol (CMP)This document describes the Internet X.509 Public Key Infrastructure (PKI) Certificate Management Protocol (CMP). Protocol messages are defined for X.509v3 certificate creation and management. CMP provides on-line interactions between PKI components, including an exchange between a Certification Authority (CA) and a client system. [STANDARDS-TRACK]Certificate Management over CMS (CMC)This document defines the base syntax for CMC, a Certificate Management protocol using the Cryptographic Message Syntax (CMS). This protocol addresses two immediate needs within the Internet Public Key Infrastructure (PKI) community:1. The need for an interface to public key certification products and services based on CMS and PKCS #10 (Public Key Cryptography Standard), and2. The need for a PKI enrollment protocol for encryption only keys due to algorithm or hardware design.CMC also requires the use of the transport document and the requirements usage document along with this document for a full definition. [STANDARDS-TRACK]YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. [STANDARDS-TRACK]Hypertext Transfer Protocol (HTTP/1.1): AuthenticationThe Hypertext Transfer Protocol (HTTP) is a stateless application- level protocol for distributed, collaborative, hypermedia information systems. This document defines the HTTP Authentication framework.The YANG 1.1 Data Modeling LanguageYANG is a data modeling language used to model configuration data, state data, Remote Procedure Calls, and notifications for network management protocols. This document describes the syntax and semantics of version 1.1 of the YANG language. YANG version 1.1 is a maintenance release of the YANG language, addressing ambiguities and defects in the original specification. There are a small number of backward incompatibilities from YANG version 1. This document also specifies the YANG mappings to the Network Configuration Protocol (NETCONF).RESTCONF ProtocolThis document describes an HTTP-based protocol that provides a programmatic interface for accessing data defined in YANG, using the datastore concepts defined in the Network Configuration Protocol (NETCONF).Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.The Transport Layer Security (TLS) Protocol Version 1.3This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery.This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations.Secure Zero Touch Provisioning (SZTP)This document presents a technique to securely provision a networking device when it is booting in a factory-default state. Variations in the solution enable it to be used on both public and private networks. The provisioning steps are able to update the boot image, commit an initial configuration, and execute arbitrary scripts to address auxiliary needs. The updated device is subsequently able to establish secure connections with other systems. For instance, a device may establish NETCONF (RFC 6241) and/or RESTCONF (RFC 8040) connections with deployment-specific network management systems.YANG Data Structure ExtensionsThis document describes YANG mechanisms for defining abstract data structures with YANG.Information Technology - ASN.1 encoding rules: Specification of Basic
Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER)International Telecommunication UnionInformative ReferencesIEEE Standard for Local and metropolitan area networks - Secure Device IdentityIEEE SA-Standards BoardNational Vulnerability Database - CVE-2008-0166National Institute of Science and Technology (NIST)Mining Your Ps and Qs: Detection of Widespread Weak Keys in Network DevicesSecurity'12: Proceedings of the 21st USENIX conference on Security symposiumUC San DiegoUniversity of MichiganUniversity of MichiganUniversity of MichiganInformation technology -- Security techniques -- Test and analysis methods for random bit generators within ISO/IEC 19790 and ISO/IEC 15408International Organization for Standardization (ISO)Recommendation for Random Number Generation Using Deterministic Random Bit GeneratorsInformation Technology LaboratoryInformation Technology LaboratoryA proposal for: Functionality classes for random number generators, version 2.0Bundesamt für Sicherheit in der Informationstechnik (BSI)T-Systems GEI GmbHBundesamt für Sicherheit in der Informationstechnik (BSI)Randomness Requirements for SecuritySecurity systems are built on strong cryptographic algorithms that foil pattern analysis attempts. However, the security of these systems is dependent on generating secret quantities for passwords, cryptographic keys, and similar quantities. The use of pseudo-random processes to generate secret quantities can result in pseudo-security. A sophisticated attacker may find it easier to reproduce the environment that produced the secret quantities and to search the resulting small set of possibilities than to locate the quantities in the whole of the potential number space.Choosing random quantities to foil a resourceful and motivated adversary is surprisingly difficult. This document points out many pitfalls in using poor entropy sources or traditional pseudo-random number generation techniques for generating such quantities. It recommends the use of truly random hardware techniques and shows that the existing hardware on many systems can be used for this purpose. It provides suggestions to ameliorate the problem when a hardware solution is not available, and it gives examples of how large such quantities need to be for some applications. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.PKCS #12: Personal Information Exchange Syntax v1.1PKCS #12 v1.1 describes a transfer syntax for personal identity information, including private keys, certificates, miscellaneous secrets, and extensions. Machines, applications, browsers, Internet kiosks, and so on, that support this standard will allow a user to import, export, and exercise a single set of personal identity information. This standard supports direct transfer of personal information under several privacy and integrity modes.This document represents a republication of PKCS #12 v1.1 from RSA Laboratories' Public Key Cryptography Standard (PKCS) series. By publishing this RFC, change control is transferred to the IETF.YANG Tree DiagramsThis document captures the current syntax used in YANG module tree diagrams. The purpose of this document is to provide a single location for this definition. This syntax may be updated from time to time based on the evolution of the YANG language.Guidelines for Authors and Reviewers of Documents Containing YANG Data ModelsThis memo provides guidelines for authors and reviewers of specifications containing YANG modules. Recommendations and procedures are defined, which are intended to increase interoperability and usability of Network Configuration Protocol (NETCONF) and RESTCONF protocol implementations that utilize YANG modules. This document obsoletes RFC 6087.A YANG Data Model for Factory Default SettingsThis document defines a YANG data model with the "factory-reset" RPC to allow clients to reset a server back to its factory default condition. It also defines an optional "factory-default" datastore to allow clients to read the factory default configuration for the device.The YANG data model in this document conforms to the Network Management Datastore Architecture (NMDA) defined in RFC 8342.AcknowledgementsThe authors would like to thank for following for lively
discussions on list and in the halls (ordered by first name):
Benjamin Kaduk,
David von Oheimb,
Dan Romascanu,
Eric Vyncke,
Hendrik Brockhaus,
Guy Fedorkow,
Joe Clarke,
Meral Shirazipour,
Murray Kucherawy,
Rich Salz,
Rob Wilton,
Roman Danyliw,
Qin Wu,
Yaron Sheffer,
and Zaheduzzaman Sarkar.
ContributorsSpecial thanks go to David von Oheimb and Hendrik Brockhaus
for helping with the descriptions for the "cmc-csr" and "cmp-csr"
nodes.