]> YANG Groupings for TLS Clients and TLS Servers Watsen Networks
kent+ietf@watsen.net
OPS netconf This document presents four YANG 1.1 modules -- three IETF modules and one supporting IANA module. The three IETF modules are "ietf-tls-common", "ietf-tls-client", and "ietf-tls-server". The "ietf-tls-client" and "ietf-tls-server" modules are the primary productions of this work, supporting the configuration and monitoring of TLS clients and servers. The IANA module is "iana-tls-cipher-suite-algs". This module defines YANG enumerations that provide support for an IANA-maintained algorithm registry.
Introduction This document presents four YANG 1.1 modules -- three IETF modules and one IANA module. The three IETF modules are "ietf-tls-common" (), "ietf-tls-client" (), and "ietf-tls-server" (). The "ietf-tls-client" and "ietf-tls-server" modules are the primary productions of this work, supporting the configuration and monitoring of TLS clients and servers. The groupings defined in this document are expected to be used in conjunction with the groupings defined in an underlying transport-level module, such as the groupings defined in . The transport-level data model enables the configuration of transport-level values such as a remote address, a remote port, a local address, and a local port. The IANA module is "iana-tls-cipher-suite-algs". This module defines YANG enumerations that provide support for an IANA-maintained algorithm registry. IANA used the script in to generate the "iana-tls-cipher-suite-algs" YANG module. This document does not publish the initial version of the module; it is published and maintained by IANA.
Regarding the Three IETF Modules The three IETF modules define features and groupings to model "generic" TLS clients and TLS servers, where "generic" should be interpreted as "least common denominator" rather than "complete." Basic TLS protocol support is afforded by these modules, leaving configuration of advance features to augmentations made by consuming modules. It is intended that the YANG groupings will be used by applications needing to configure TLS client and server protocol stacks. For instance, these groupings are used to help define the data model for HTTPS and clients and servers based on the Network Configuration Protocol (NETCONF) over TLS in and , respectively. The "ietf-tls-client" and "ietf-tls-server" YANG modules each define one grouping, which is focused on just TLS-specific configuration, and specifically avoid any transport-level configuration, such as what ports to listen on or connect to. This affords applications the opportunity to define their own strategy for how the underlying TCP connection is established. For instance, applications supporting NETCONF Call Home could use the "tls-server-grouping" grouping for the TLS parts it provides, while adding data nodes for the TCP-level call-home configuration. Both TLS 1.2 and TLS 1.3 may be configured. TLS 1.2 is obsoleted by TLS 1.3 but is still in common use, and hence its "feature" statement is marked "status deprecated".
Relation to Other RFCs This document presents four YANG modules that are part of a collection of RFCs that work together to ultimately support the configuration of both the clients and servers of the NETCONF and RESTCONF protocols. The dependency relationship between the primary YANG groupings defined in the various RFCs is presented in the diagram below. In some cases, a document may define secondary groupings that introduce dependencies not illustrated in the diagram. The labels in the diagram are shorthand names for the defining RFCs. The citation references for the shorthand names are provided below the diagram. Please note that the arrows in the diagram point from referencer to referenced. For example, the "crypto-types" RFC does not have any dependencies, whilst the "keystore" RFC depends on the "crypto-types" RFC. Labels in Diagram to RFC Mapping
Label in Diagram Originating RFC
crypto-types
truststore
keystore
tcp-client-server
ssh-client-server
tls-client-server RFC 9645
http-client-server
netconf-client-server
restconf-client-server
Specification Language 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 when, and only when, they appear in all capitals, as shown here.
Adherence to the NMDA This document is compliant with the Network Management Datastore Architecture (NMDA) . For instance, as described in and , trust anchors and keys installed during manufacturing are expected to appear in <operational> () and <system> if implemented.
Conventions Various examples in this document use "BASE64VALUE=" as a placeholder value for binary data that has been base64 encoded (per ). This placeholder value is used because real base64-encoded structures are often many lines long and hence distracting to the example being presented. Various examples in this document use the XML encoding. Other encodings, such as JSON , could alternatively be used. Various examples in this document contain long lines that may be folded, as described in [RFC8792].
The "ietf-tls-common" Module The TLS common model presented in this section contains features and groupings common to both TLS clients and TLS servers. The "hello-params-grouping" grouping can be used to configure the list of TLS algorithms permitted by the TLS client or TLS server. The lists of algorithms are ordered such that, if multiple algorithms are permitted by the client, the algorithm that appears first in its list and that is also permitted by the server is used for the TLS transport layer connection. The ability to restrict the algorithms allowed is provided in this grouping for TLS clients and TLS servers that are capable of doing so and that may serve to make TLS clients and TLS servers compliant with local security policies. This model supports both TLS 1.2 and TLS 1.3 . Thus, in order to support both TLS 1.2 and TLS 1.3, the cipher suites part of the "hello-params-grouping" grouping should include the following three parameters for configuring its permitted TLS algorithms: TLS Cipher Suites, TLS SignatureScheme, and TLS Supported Groups.
Data Model Overview This section provides an overview of the "ietf-tls-common" module in terms of its features, identities, and groupings.
Features The following diagram lists all the "feature" statements defined in the "ietf-tls-common" module: The diagram above uses syntax that is similar to but not defined in . Please refer to the YANG module for a description of each feature.
Identities The following diagram illustrates the relationship amongst the "identity" statements defined in the "ietf-tls-common" module: The diagram above uses syntax that is similar to but not defined in . Comments:
  • The diagram shows that there are two base identities.
  • One base identity is used to specify TLS versions. This base identity is "abstract" in the object-oriented programming sense because it defines a "class" of things rather than a specific thing.
  • These base identities are "abstract" in the object-oriented programming sense because they only define a "class" of things rather than a specific thing.
Groupings The "ietf-tls-common" module defines the following "grouping" statement:
  • hello-params-grouping
This grouping is presented in the following subsection.
The "hello-params-grouping" Grouping The following tree diagram illustrates the "hello-params-grouping" grouping: Comments:
  • This grouping is used by both the "tls-client-grouping" and the "tls-server-grouping" groupings defined in Sections and , respectively.
  • This grouping enables client and server configurations to specify the TLS versions and cipher suites that are to be used when establishing TLS sessions.
  • The "cipher-suites" list is "ordered-by user".
Protocol-Accessible Nodes The following tree diagram lists all the protocol-accessible nodes defined in the "ietf-tls-common" module, without expanding the "grouping" statements: Comments:
  • Protocol-accessible nodes are nodes that are accessible when the module is "implemented", as described in .
  • The protocol-accessible nodes for the "ietf-tls-common" module are limited to the "supported-algorithms" container, which is constrained by the "algorithm-discovery" feature, and the "generate-asymmetric-key-pair" RPC, which is constrained by the "asymmetric-key-pair-generation" feature.
  • The "encrypted-by-grouping" grouping is discussed in .
  • The "asymmetric-key-pair-grouping" grouping is discussed in .
Example Usage The following example illustrates the "hello-params-grouping" grouping when populated with some data. tlscmn:tls12 tlscmn:tls13 TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 TLS_RSA_WITH_3DES_EDE_CBC_SHA ]]> The following example illustrates operational state data indicating the TLS algorithms supported by the server. TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 TLS_RSA_WITH_3DES_EDE_CBC_SHA TLS_ECDHE_PSK_WITH_AES_256_GCM_SHA384 TLS_DHE_PSK_WITH_CHACHA20_POLY1305_SHA256 TLS_ECCPWD_WITH_AES_256_GCM_SHA384 TLS_PSK_WITH_AES_256_CCM TLS_PSK_WITH_AES_256_CCM_8 TLS_DHE_PSK_WITH_CAMELLIA_256_CBC_SHA384 TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384 TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA TLS_DH_DSS_WITH_AES_128_GCM_SHA256 ]]> The following example illustrates the "generate-asymmetric-key-pair" RPC. REQUEST TLS_ECDHE_PSK_WITH_AES_128_GCM_SHA256 521 hidden-asymmetric-key ]]> RESPONSE ct:subject-public-key-info-format BASE64VALUE= ct:ec-private-key-format BASE64VALUE= ]]>
YANG Module This YANG module has normative references to , , , , , , and . This YANG module has informative references to and . WG Web: https://datatracker.ietf.org/wg/netconf Author: Kent Watsen Author: Jeff Hartley Author: Gary Wu "; description "This module defines common features and groupings for Transport Layer Security (TLS). 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. Copyright (c) 2024 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 9645 (https://www.rfc-editor.org/info/rfc9645); see the RFC itself for full legal notices."; revision 2024-10-10 { description "Initial version."; reference "RFC 9645: YANG Groupings for TLS Clients and TLS Servers"; } // Features feature tls12 { description "TLS Protocol Version 1.2 is supported. TLS 1.2 is obsolete, and thus it is NOT RECOMMENDED to enable this feature."; reference "RFC 5246: The Transport Layer Security (TLS) Protocol Version 1.2"; } feature tls13 { description "TLS Protocol Version 1.3 is supported."; reference "RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3"; } feature hello-params { description "TLS hello message parameters are configurable."; } feature algorithm-discovery { description "Indicates that the server implements the 'supported-algorithms' container."; } feature asymmetric-key-pair-generation { description "Indicates that the server implements the 'generate-asymmetric-key-pair' RPC."; } // Identities identity tls-version-base { description "Base identity used to identify TLS protocol versions."; } identity tls12 { if-feature "tls12"; base tls-version-base; description "TLS Protocol Version 1.2."; reference "RFC 5246: The Transport Layer Security (TLS) Protocol Version 1.2"; } identity tls13 { if-feature "tls13"; base tls-version-base; description "TLS Protocol Version 1.3."; reference "RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3"; } // Typedefs typedef epsk-supported-hash { type enumeration { enum sha-256 { description "The SHA-256 hash."; } enum sha-384 { description "The SHA-384 hash."; } } description "As per Section 4.2.11 of RFC 8446, the hash algorithm supported by an instance of an External Pre-Shared Key (EPSK)."; reference "RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3"; } // Groupings grouping hello-params-grouping { description "A reusable grouping for TLS hello message parameters."; reference "RFC 5246: The Transport Layer Security (TLS) Protocol Version 1.2 RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3"; container tls-versions { description "Parameters limiting which TLS versions, amongst those enabled by 'features', are presented during the TLS handshake."; leaf min { type identityref { base tls-version-base; } description "If not specified, then there is no configured minimum version."; } leaf max { type identityref { base tls-version-base; } description "If not specified, then there is no configured maximum version."; } } container cipher-suites { description "Parameters regarding cipher suites."; leaf-list cipher-suite { type tlscsa:tls-cipher-suite-algorithm; ordered-by user; description "Acceptable cipher suites in order of descending preference. The configured host key algorithms should be compatible with the algorithm used by the configured private key. Please see Section 5 of RFC 9645 for valid combinations. If this leaf-list is not configured (has zero elements), the acceptable cipher suites are implementation- defined."; reference "RFC 9645: YANG Groupings for TLS Clients and TLS Servers"; } } } // hello-params-grouping // Protocol-accessible Nodes container supported-algorithms { if-feature "algorithm-discovery"; config false; description "A container for a list of cipher suite algorithms supported by the server."; leaf-list supported-algorithm { type tlscsa:tls-cipher-suite-algorithm; description "A cipher suite algorithm supported by the server."; } } rpc generate-asymmetric-key-pair { if-feature "asymmetric-key-pair-generation"; description "Requests the device to generate an 'asymmetric-key-pair' key using the specified key algorithm."; input { leaf algorithm { type tlscsa:tls-cipher-suite-algorithm; mandatory true; description "The cipher suite algorithm that the generated key works with. Implementations derive the public key algorithm from the cipher suite algorithm. For example, cipher suite 'tls-rsa-with-aes-256-cbc-sha256' maps to the RSA public key."; } leaf num-bits { type uint16; description "Specifies the number of bits to create in the key. For RSA keys, the minimum size is 1024 bits, and the default is 3072 bits. Generally, 3072 bits is considered sufficient. DSA keys must be exactly 1024 bits as specified by FIPS 186-2. For elliptical keys, the 'num-bits' value determines the key length of the curve (e.g., 256, 384, or 521), where valid values supported by the server are conveyed via an unspecified mechanism. For some public algorithms, the keys have a fixed length, and thus the 'num-bits' value is not specified."; } container private-key-encoding { description "Indicates how the private key is to be encoded."; choice private-key-encoding { mandatory true; description "A choice amongst optional private key handling."; case cleartext { if-feature "ct:cleartext-private-keys"; leaf cleartext { type empty; description "Indicates that the private key is to be returned as a cleartext value."; } } case encrypted { if-feature "ct:encrypted-private-keys"; container encrypted { description "Indicates that the key is to be encrypted using the specified symmetric or asymmetric key."; uses ks:encrypted-by-grouping; } } case hidden { if-feature "ct:hidden-private-keys"; leaf hidden { type empty; description "Indicates that the private key is to be hidden. Unlike the 'cleartext' and 'encrypt' options, the key returned is a placeholder for an internally stored key. See Section 3 of RFC 9642 ('Support for Built-In Keys') for information about hidden keys."; } } } } } output { choice key-or-hidden { case key { uses ct:asymmetric-key-pair-grouping; } case hidden { leaf location { type instance-identifier; description "The location to where a hidden key was created."; } } description "The output can be either a key (for cleartext and encrypted keys) or the location to where the key was created (for hidden keys)."; } } } // end generate-asymmetric-key-pair } ]]>
The "ietf-tls-client" Module This section defines a YANG 1.1 module called "ietf-tls-client". A high-level overview of the module is provided in . Examples illustrating the module's use are provided in ("Example Usage"). The YANG module itself is defined in .
Data Model Overview This section provides an overview of the "ietf-tls-client" module in terms of its features and groupings.
Features The following diagram lists all the "feature" statements defined in the "ietf-tls-client" module: The diagram above uses syntax that is similar to but not defined in . Please refer to the YANG module for a description of each feature.
Groupings The "ietf-tls-client" module defines the following "grouping" statement:
  • tls-client-grouping
This grouping is presented in the following subsection.
The "tls-client-grouping" Grouping The following tree diagram illustrates the "tls-client-grouping" grouping: Comments:
  • The "client-identity" node, which is optionally configured (as client authentication MAY occur at a higher protocol layer), configures identity credentials, each enabled by a "feature" statement defined in .
  • The "server-authentication" node configures trust anchors for authenticating the TLS server, with each option enabled by a "feature" statement.
  • The "hello-params" node, which must be enabled by a feature, configures parameters for the TLS sessions established by this configuration.
  • The "keepalives" node, which must be enabled by a feature, configures a "presence" container to test the aliveness of the TLS server. The aliveness-test occurs at the TLS protocol layer.
  • For the referenced grouping statement(s):
    • The "inline-or-keystore-end-entity-cert-with-key-grouping" grouping is discussed in .
    • The "inline-or-keystore-asymmetric-key-grouping" grouping is discussed in .
    • The "inline-or-keystore-symmetric-key-grouping" grouping is discussed in .
    • The "inline-or-truststore-certs-grouping" grouping is discussed in .
    • The "inline-or-truststore-public-keys-grouping" grouping is discussed in .
    • The "hello-params-grouping" grouping is discussed in in this document.
Protocol-Accessible Nodes The "ietf-tls-client" module defines only "grouping" statements that are used by other modules to instantiate protocol-accessible nodes. Thus, this module does not itself define any protocol-accessible nodes when implemented.
Example Usage This section presents two examples showing the "tls-client-grouping" grouping populated with some data. These examples are effectively the same except the first configures the client identity using a local key while the second uses a key configured in a keystore. Both examples are consistent with the examples presented in and . The following configuration example uses inline-definitions for the client identity and server authentication: ct:rsa-private-key-format BASE64VALUE= BASE64VALUE= Server Cert Issuer #1 BASE64VALUE= Server Cert Issuer #2 BASE64VALUE= My Application #1 BASE64VALUE= My Application #2 BASE64VALUE= corp-fw1 ct:subject-public-key-info-fo\ rmat BASE64VALUE= corp-fw2 ct:subject-public-key-info-fo\ rmat BASE64VALUE= 30 3 ]]> The following configuration example uses central-keystore-references for the client identity and central-truststore-references for server authentication from the keystore: rsa-asymmetric-key ex-rsa-cert trusted-server-ca-certs trusted-server-ee-certs Raw Public Keys for TLS Se\ rvers 30 3 ]]>
YANG Module This YANG module has normative references to , , , , , , and and informative references to , , , , and . WG Web: https://datatracker.ietf.org/wg/netconf Author: Kent Watsen Author: Jeff Hartley "; description "This module defines reusable groupings for TLS clients that can be used as a basis for specific TLS client instances. 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. Copyright (c) 2024 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 9645 (https://www.rfc-editor.org/info/rfc9645); see the RFC itself for full legal notices."; revision 2024-10-10 { description "Initial version"; reference "RFC 9645: YANG Groupings for TLS Clients and TLS Servers"; } // Features feature tls-client-keepalives { description "Per-socket TLS keepalive parameters are configurable for TLS clients on the server implementing this feature."; } feature client-ident-x509-cert { description "Indicates that the client supports identifying itself using X.509 certificates."; reference "RFC 5280: Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile"; } feature client-ident-raw-public-key { description "Indicates that the client supports identifying itself using raw public keys."; reference "RFC 7250: Using Raw Public Keys in Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)"; } feature client-ident-tls12-psk { if-feature "tlscmn:tls12"; description "Indicates that the client supports identifying itself using TLS 1.2 PSKs (pre-shared or pairwise symmetric keys)."; reference "RFC 4279: Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)"; } feature client-ident-tls13-epsk { if-feature "tlscmn:tls13"; description "Indicates that the client supports identifying itself using TLS 1.3 External PSKs (pre-shared keys)."; reference "RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3"; } feature server-auth-x509-cert { description "Indicates that the client supports authenticating servers using X.509 certificates."; reference "RFC 5280: Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile"; } feature server-auth-raw-public-key { description "Indicates that the client supports authenticating servers using raw public keys."; reference "RFC 7250: Using Raw Public Keys in Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)"; } feature server-auth-tls12-psk { description "Indicates that the client supports authenticating servers using PSKs (pre-shared or pairwise symmetric keys)."; reference "RFC 4279: Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)"; } feature server-auth-tls13-epsk { description "Indicates that the client supports authenticating servers using TLS 1.3 External PSKs (pre-shared keys)."; reference "RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3"; } // Groupings grouping tls-client-grouping { description "A reusable grouping for configuring a TLS client without any consideration for how an underlying TCP session is established. Note that this grouping uses fairly typical descendant node names such that a stack of 'uses' statements will have name conflicts. It is intended that the consuming data model will resolve the issue (e.g., by wrapping the 'uses' statement in a container called 'tls-client-parameters'). This model purposely does not do this itself so as to provide maximum flexibility to consuming models."; container client-identity { nacm:default-deny-write; presence "Indicates that a TLS-level client identity has been configured. This statement is present so the mandatory descendant nodes do not imply that this node must be configured."; description "Identity credentials the TLS client MAY present when establishing a connection to a TLS server. If not configured, then client authentication is presumed to occur in a protocol layer above TLS. When configured, and requested by the TLS server when establishing a TLS session, these credentials are passed in the Certificate message defined in Section 7.4.2 of RFC 5246 and Section 4.4.2 of RFC 8446."; reference "RFC 5246: The Transport Layer Security (TLS) Protocol Version 1.2 RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3 RFC 9642: A YANG Data Model for a Keystore"; choice auth-type { mandatory true; description "A choice amongst authentication types, of which one must be enabled (via its associated 'feature') and selected."; case certificate { if-feature "client-ident-x509-cert"; container certificate { description "Specifies the client identity using a certificate."; uses "ks:inline-or-keystore-end-entity-cert-with-key-" + "grouping" { refine "inline-or-keystore/inline/inline-definition" { must 'not(public-key-format) or derived-from-or-self' + '(public-key-format, "ct:subject-public-key-' + 'info-format")'; } refine "inline-or-keystore/central-keystore/" + "central-keystore-reference/asymmetric-key" { must 'not(deref(.)/../ks:public-key-format) or ' + 'derived-from-or-self(deref(.)/../ks:public-' + 'key-format, "ct:subject-public-key-info-' + 'format")'; } } } } case raw-public-key { if-feature "client-ident-raw-public-key"; container raw-private-key { description "Specifies the client identity using a raw private key."; uses ks:inline-or-keystore-asymmetric-key-grouping { refine "inline-or-keystore/inline/inline-definition" { must 'not(public-key-format) or derived-from-or-self' + '(public-key-format, "ct:subject-public-key-' + 'info-format")'; } refine "inline-or-keystore/central-keystore/" + "central-keystore-reference" { must 'not(deref(.)/../ks:public-key-format) or ' + 'derived-from-or-self(deref(.)/../ks:public-' + 'key-format, "ct:subject-public-key-info-' + 'format")'; } } } } case tls12-psk { if-feature "client-ident-tls12-psk"; container tls12-psk { description "Specifies the client identity using a PSK (pre-shared or pairwise symmetric key)."; uses ks:inline-or-keystore-symmetric-key-grouping; leaf id { type string; description "The key 'psk_identity' value used in the TLS 'ClientKeyExchange' message."; reference "RFC 4279: Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)"; } } } case tls13-epsk { if-feature "client-ident-tls13-epsk"; container tls13-epsk { description "An External Pre-Shared Key (EPSK) is established or provisioned out of band, i.e., not from a TLS connection. An EPSK is a tuple of (Base Key, External Identity, Hash). EPSKs MUST NOT be imported for (D)TLS 1.2 or prior versions. When PSKs are provisioned out of band, the PSK identity and the Key Derivation Function (KDF) hash algorithm to be used with the PSK MUST also be provisioned. The structure of this container is designed to satisfy the requirements in Section 4.2.11 of RFC 8446, the recommendations from Section 6 of RFC 9257, and the EPSK input fields detailed in Section 5.1 of RFC 9258. The base-key is based upon 'ks:inline-or-keystore-symmetric-key-grouping' in order to provide users with flexible and secure storage options."; reference "RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3 RFC 9257: Guidance for External Pre-Shared Key (PSK) Usage in TLS RFC 9258: Importing External Pre-Shared Keys (PSKs) for TLS 1.3"; uses ks:inline-or-keystore-symmetric-key-grouping; leaf external-identity { type string; mandatory true; description "As per Section 4.2.11 of RFC 8446 and Section 4.1 of RFC 9257, a sequence of bytes used to identify an EPSK. A label for a pre-shared key established externally."; reference "RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3 RFC 9257: Guidance for External Pre-Shared Key (PSK) Usage in TLS"; } leaf hash { type tlscmn:epsk-supported-hash; default "sha-256"; description "As per Section 4.2.11 of RFC 8446, for EPSKs, the hash algorithm MUST be set when the PSK is established; otherwise, default to SHA-256 if no such algorithm is defined. The server MUST ensure that it selects a compatible PSK (if any) and cipher suite. Each PSK MUST only be used with a single hash function."; reference "RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3"; } leaf context { type string; description "As per Section 5.1 of RFC 9258, context MUST include the context used to determine the EPSK, if any exists. For example, context may include information about peer roles or identities to mitigate Selfie-style reflection attacks. Since the EPSK is a key derived from an external protocol or a sequence of protocols, context MUST include a channel binding for the deriving protocols (see RFC 5056). The details of this binding are protocol specific and out of scope for this document."; reference "RFC 9258: Importing External Pre-Shared Keys (PSKs) for TLS 1.3"; } leaf target-protocol { type uint16; description "As per Section 3 of RFC 9258, the protocol for which a PSK is imported for use."; reference "RFC 9258: Importing External Pre-Shared Keys (PSKs) for TLS 1.3"; } leaf target-kdf { type uint16; description "As per Section 3 of RFC 9258, the Key Derivation Function (KDF) for which a PSK is imported for use."; reference "RFC 9258: Importing External Pre-Shared Keys (PSKs) for TLS 1.3"; } } } } } // container client-identity container server-authentication { nacm:default-deny-write; must "ca-certs or ee-certs or raw-public-keys or tls12-psks or tls13-epsks"; description "Specifies how the TLS client can authenticate TLS servers. Any combination of credentials is additive and unordered. Note that no configuration is required for authentication based on PSK (pre-shared or pairwise symmetric key) as the key is necessarily the same as configured in the '../client-identity' node."; container ca-certs { if-feature "server-auth-x509-cert"; presence "Indicates that Certification Authority (CA) certificates have been configured. This statement is present so the mandatory descendant nodes do not imply that this node must be configured."; description "A set of CA certificates used by the TLS client to authenticate TLS server certificates. A server certificate is authenticated if it has a valid chain of trust to a configured CA certificate."; reference "RFC 9641: A YANG Data Model for a Truststore"; uses ts:inline-or-truststore-certs-grouping; } container ee-certs { if-feature "server-auth-x509-cert"; presence "Indicates that End-Entity (EE) certificates have been configured. This statement is present so the mandatory descendant nodes do not imply that this node must be configured."; description "A set of server certificates (i.e., EE certificates) used by the TLS client to authenticate certificates presented by TLS servers. A server certificate is authenticated if it is an exact match to a configured server certificate."; reference "RFC 9641: A YANG Data Model for a Truststore"; uses ts:inline-or-truststore-certs-grouping; } container raw-public-keys { if-feature "server-auth-raw-public-key"; presence "Indicates that raw public keys have been configured. This statement is present so the mandatory descendant nodes do not imply that this node must be configured."; description "A set of raw public keys used by the TLS client to authenticate raw public keys presented by the TLS server. A raw public key is authenticated if it is an exact match to a configured raw public key."; reference "RFC 9641: A YANG Data Model for a Truststore"; uses ts:inline-or-truststore-public-keys-grouping { refine "inline-or-truststore/inline/inline-definition/" + "public-key" { must 'derived-from-or-self(public-key-format,' + ' "ct:subject-public-key-info-format")'; } refine "inline-or-truststore/central-truststore/" + "central-truststore-reference" { must 'not(deref(.)/../ts:public-key/ts:public-key-' + 'format[not(derived-from-or-self(., "ct:subject-' + 'public-key-info-format"))])'; } } } leaf tls12-psks { if-feature "server-auth-tls12-psk"; type empty; description "Indicates that the TLS client can authenticate TLS servers using configured PSKs (pre-shared or pairwise symmetric keys). No configuration is required since the PSK value is the same as the PSK value configured in the 'client-identity' node."; } leaf tls13-epsks { if-feature "server-auth-tls13-epsk"; type empty; description "Indicates that the TLS client can authenticate TLS servers using configured External PSKs (pre-shared keys). No configuration is required since the PSK value is the same as the PSK value configured in the 'client-identity' node."; } } // container server-authentication container hello-params { nacm:default-deny-write; if-feature "tlscmn:hello-params"; uses tlscmn:hello-params-grouping; description "Configurable parameters for the TLS hello message."; } // container hello-params container keepalives { nacm:default-deny-write; if-feature "tls-client-keepalives"; description "Configures the keepalive policy for the TLS client."; leaf peer-allowed-to-send { type empty; description "Indicates that the remote TLS server is allowed to send HeartbeatRequest messages, as defined by RFC 6520, to this TLS client."; reference "RFC 6520: Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) Heartbeat Extension"; } container test-peer-aliveness { presence "Indicates that the TLS client proactively tests the aliveness of the remote TLS server."; description "Configures the keepalive policy to proactively test the aliveness of the TLS server. An unresponsive TLS server is dropped after approximately max-wait * max-attempts seconds. The TLS client MUST send HeartbeatRequest messages, as defined in RFC 6520."; reference "RFC 6520: Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) Heartbeat Extension"; leaf max-wait { type uint16 { range "1..max"; } units "seconds"; default "30"; description "Sets the amount of time in seconds, after which a TLS-level message will be sent to test the aliveness of the TLS server if no data has been received from the TLS server."; } leaf max-attempts { type uint8; default "3"; description "Sets the maximum number of sequential keepalive messages that can fail to obtain a response from the TLS server before assuming the TLS server is no longer alive."; } } } } // grouping tls-client-grouping } ]]>
The "ietf-tls-server" Module This section defines a YANG 1.1 module called "ietf-tls-server". A high-level overview of the module is provided in . Examples illustrating the module's use are provided in ("Example Usage"). The YANG module itself is defined in .
Data Model Overview This section provides an overview of the "ietf-tls-server" module in terms of its features and groupings.
Features The following diagram lists all the "feature" statements defined in the "ietf-tls-server" module: The diagram above uses syntax that is similar to but not defined in . Please refer to the YANG module for a description of each feature.
Groupings The "ietf-tls-server" module defines the following "grouping" statement:
  • tls-server-grouping
This grouping is presented in the following subsection.
The "tls-server-grouping" Grouping The following tree diagram illustrates the "tls-server-grouping" grouping: Comments:
  • The "server-identity" node configures identity credentials, each of which is enabled by a "feature".
  • The "client-authentication" node, which is optionally configured (as client authentication MAY occur at a higher protocol layer), configures trust anchors for authenticating the TLS client, with each option enabled by a "feature" statement.
  • The "hello-params" node, which must be enabled by a feature, configures parameters for the TLS sessions established by this configuration.
  • The "keepalives" node, which must be enabled by a feature, configures a flag enabling the TLS client to test the aliveness of the TLS server as well as a "presence" container to test the aliveness of the TLS client. The aliveness-tests occur at the TLS protocol layer.
  • For the referenced grouping statement(s):
    • The "inline-or-keystore-end-entity-cert-with-key-grouping" grouping is discussed in .
    • The "inline-or-keystore-asymmetric-key-grouping" grouping is discussed in .
    • The "inline-or-keystore-symmetric-key-grouping" grouping is discussed in .
    • The "inline-or-truststore-public-keys-grouping" grouping is discussed in .
    • The "inline-or-truststore-certs-grouping" grouping is discussed in .
    • The "hello-params-grouping" grouping is discussed in in this document.
Protocol-Accessible Nodes The "ietf-tls-server" module defines only "grouping" statements that are used by other modules to instantiate protocol-accessible nodes. Thus, this module does not itself define any protocol-accessible nodes when implemented.
Example Usage This section presents two examples showing the "tls-server-grouping" grouping populated with some data. These examples are effectively the same except the first configures the server identity using a local key while the second uses a key configured in a keystore. Both examples are consistent with the examples presented in and . The following configuration example uses inline-definitions for the server identity and client authentication: ct:rsa-private-key-format BASE64VALUE= BASE64VALUE= Identity Cert Issuer #1 BASE64VALUE= Identity Cert Issuer #2 BASE64VALUE= Application #1 BASE64VALUE= Application #2 BASE64VALUE= User A ct:subject-public-key-info-fo\ rmat BASE64VALUE= User B ct:subject-public-key-info-fo\ rmat BASE64VALUE= ]]> The following configuration example uses central-keystore-references for the server identity and central-truststore-references for client authentication from the keystore: rsa-asymmetric-key ex-rsa-cert trusted-client-ca-certs trusted-client-ee-certs Raw Public Keys for TLS Cl\ ients ]]>
YANG Module This YANG module has normative references to , , , , , , and and informative references to , , , , and . WG Web: https://datatracker.ietf.org/wg/netconf Author: Kent Watsen Author: Jeff Hartley "; description "This module defines reusable groupings for TLS servers that can be used as a basis for specific TLS server instances. 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. Copyright (c) 2024 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 9645 (https://www.rfc-editor.org/info/rfc9645); see the RFC itself for full legal notices."; revision 2024-10-10 { description "Initial version."; reference "RFC 9645: YANG Groupings for TLS Clients and TLS Servers"; } // Features feature tls-server-keepalives { description "Per-socket TLS keepalive parameters are configurable for TLS servers on the server implementing this feature."; } feature server-ident-x509-cert { description "Indicates that the server supports identifying itself using X.509 certificates."; reference "RFC 5280: Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile"; } feature server-ident-raw-public-key { description "Indicates that the server supports identifying itself using raw public keys."; reference "RFC 7250: Using Raw Public Keys in Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)"; } feature server-ident-tls12-psk { if-feature "tlscmn:tls12"; description "Indicates that the server supports identifying itself using TLS 1.2 PSKs (pre-shared or pairwise symmetric keys)."; reference "RFC 4279: Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)"; } feature server-ident-tls13-epsk { if-feature "tlscmn:tls13"; description "Indicates that the server supports identifying itself using TLS 1.3 External PSKs (pre-shared keys)."; reference "RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3"; } feature client-auth-supported { description "Indicates that the configuration for how to authenticate clients can be configured herein. TLS-level client authentication may not be needed when client authentication is expected to occur only at another protocol layer."; } feature client-auth-x509-cert { description "Indicates that the server supports authenticating clients using X.509 certificates."; reference "RFC 5280: Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile"; } feature client-auth-raw-public-key { description "Indicates that the server supports authenticating clients using raw public keys."; reference "RFC 7250: Using Raw Public Keys in Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)"; } feature client-auth-tls12-psk { description "Indicates that the server supports authenticating clients using PSKs (pre-shared or pairwise symmetric keys)."; reference "RFC 4279: Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)"; } feature client-auth-tls13-epsk { description "Indicates that the server supports authenticating clients using TLS 1.3 External PSKs (pre-shared keys)."; reference "RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3"; } // Groupings grouping tls-server-grouping { description "A reusable grouping for configuring a TLS server without any consideration for how underlying TCP sessions are established. Note that this grouping uses fairly typical descendant node names such that a stack of 'uses' statements will have name conflicts. It is intended that the consuming data model will resolve the issue (e.g., by wrapping the 'uses' statement in a container called 'tls-server-parameters'). This model purposely does not do this itself so as to provide maximum flexibility to consuming models."; container server-identity { nacm:default-deny-write; description "A locally defined or referenced End-Entity (EE) certificate, including any configured intermediate certificates, that the TLS server will present when establishing a TLS connection in its Certificate message, as defined in Section 7.4.2 of RFC 5246 and Section 4.4.2 of RFC 8446."; reference "RFC 5246: The Transport Layer Security (TLS) Protocol Version 1.2 RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3 RFC 9642: A YANG Data Model for a Keystore"; choice auth-type { mandatory true; description "A choice amongst authentication types, of which one must be enabled (via its associated 'feature') and selected."; case certificate { if-feature "server-ident-x509-cert"; container certificate { description "Specifies the server identity using a certificate."; uses "ks:inline-or-keystore-end-entity-cert-with-key-" + "grouping" { refine "inline-or-keystore/inline/inline-definition" { must 'not(public-key-format) or derived-from-or-self' + '(public-key-format,' + ' "ct:subject-public-' + 'key-info-format")'; } refine "inline-or-keystore/central-keystore/" + "central-keystore-reference/asymmetric-key" { must 'not(deref(.)/../ks:public-key-format) or ' + 'derived-from-or-self(deref(.)/../ks:public-key' + '-format, "ct:subject-public-key-info-format")'; } } } } case raw-private-key { if-feature "server-ident-raw-public-key"; container raw-private-key { description "Specifies the server identity using a raw private key."; uses ks:inline-or-keystore-asymmetric-key-grouping { refine "inline-or-keystore/inline/inline-definition" { must 'not(public-key-format) or derived-from-or-self' + '(public-key-format,' + ' "ct:subject-public-' + 'key-info-format")'; } refine "inline-or-keystore/central-keystore/" + "central-keystore-reference" { must 'not(deref(.)/../ks:public-key-format) or ' + 'derived-from-or-self(deref(.)/../ks:public-key' + '-format, "ct:subject-public-key-info-format")'; } } } } case tls12-psk { if-feature "server-ident-tls12-psk"; container tls12-psk { description "Specifies the server identity using a PSK (pre-shared or pairwise symmetric key)."; uses ks:inline-or-keystore-symmetric-key-grouping; leaf id-hint { type string; description "The key 'psk_identity_hint' value used in the TLS 'ServerKeyExchange' message."; reference "RFC 4279: Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)"; } } } case tls13-epsk { if-feature "server-ident-tls13-epsk"; container tls13-epsk { description "An External Pre-Shared Key (EPSK) is established or provisioned out of band, i.e., not from a TLS connection. An EPSK is a tuple of (Base Key, External Identity, Hash). EPSKs MUST NOT be imported for (D)TLS 1.2 or prior versions. When PSKs are provisioned out of band, the PSK identity and the KDF hash algorithm to be used with the PSK MUST also be provisioned. The structure of this container is designed to satisfy the requirements in Section 4.2.11 of RFC 8446, the recommendations from Section 6 of RFC 9257, and the EPSK input fields detailed in Section 5.1 of RFC 9258. The base-key is based upon 'ks:inline-or-keystore-symmetric-key-grouping' in order to provide users with flexible and secure storage options."; reference "RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3 RFC 9257: Guidance for External Pre-Shared Key (PSK) Usage in TLS RFC 9258: Importing External Pre-Shared Keys (PSKs) for TLS 1.3"; uses ks:inline-or-keystore-symmetric-key-grouping; leaf external-identity { type string; mandatory true; description "As per Section 4.2.11 of RFC 8446 and Section 4.1 of RFC 9257, a sequence of bytes used to identify an EPSK. A label for a pre-shared key established externally."; reference "RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3 RFC 9257: Guidance for External Pre-Shared Key (PSK) Usage in TLS"; } leaf hash { type tlscmn:epsk-supported-hash; default "sha-256"; description "As per Section 4.2.11 of RFC 8446, for EPSKs, the hash algorithm MUST be set when the PSK is established; otherwise, default to SHA-256 if no such algorithm is defined. The server MUST ensure that it selects a compatible PSK (if any) and cipher suite. Each PSK MUST only be used with a single hash function."; reference "RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3"; } leaf context { type string; description "As per Section 5.1 of RFC 9258, context MUST include the context used to determine the EPSK, if any exists. For example, context may include information about peer roles or identities to mitigate Selfie-style reflection attacks. Since the EPSK is a key derived from an external protocol or sequence of protocols, context MUST include a channel binding for the deriving protocols (see RFC 5056). The details of this binding are protocol specific and out of scope for this document."; reference "RFC 9258: Importing External Pre-Shared Keys (PSKs) for TLS 1.3"; } leaf target-protocol { type uint16; description "As per Section 3.1 of RFC 9258, the protocol for which a PSK is imported for use."; reference "RFC 9258: Importing External Pre-Shared Keys (PSKs) for TLS 1.3"; } leaf target-kdf { type uint16; description "As per Section 3 of RFC 9258, the KDF for which a PSK is imported for use."; reference "RFC 9258: Importing External Pre-Shared Keys (PSKs) for TLS 1.3"; } } } } } // container server-identity container client-authentication { if-feature "client-auth-supported"; nacm:default-deny-write; must "ca-certs or ee-certs or raw-public-keys or tls12-psks or tls13-epsks"; presence "Indicates that client authentication is supported (i.e., that the server will request clients send certificates). If not configured, the TLS server SHOULD NOT request that TLS clients provide authentication credentials."; description "Specifies how the TLS server can authenticate TLS clients. Any combination of credentials is additive and unordered. Note that no configuration is required for authentication based on PSK (pre-shared or pairwise symmetric key) as the the key is necessarily the same as configured in the '../server-identity' node."; container ca-certs { if-feature "client-auth-x509-cert"; presence "Indicates that Certification Authority (CA) certificates have been configured. This statement is present so the mandatory descendant nodes do not imply that this node must be configured."; description "A set of CA certificates used by the TLS server to authenticate TLS client certificates. A client certificate is authenticated if it has a valid chain of trust to a configured CA certificate."; reference "RFC 9641: A YANG Data Model for a Truststore"; uses ts:inline-or-truststore-certs-grouping; } container ee-certs { if-feature "client-auth-x509-cert"; presence "Indicates that EE certificates have been configured. This statement is present so the mandatory descendant nodes do not imply that this node must be configured."; description "A set of client certificates (i.e., EE certificates) used by the TLS server to authenticate certificates presented by TLS clients. A client certificate is authenticated if it is an exact match to a configured client certificate."; reference "RFC 9641: A YANG Data Model for a Truststore"; uses ts:inline-or-truststore-certs-grouping; } container raw-public-keys { if-feature "client-auth-raw-public-key"; presence "Indicates that raw public keys have been configured. This statement is present so the mandatory descendant nodes do not imply that this node must be configured."; description "A set of raw public keys used by the TLS server to authenticate raw public keys presented by the TLS client. A raw public key is authenticated if it is an exact match to a configured raw public key."; reference "RFC 9641: A YANG Data Model for a Truststore"; uses ts:inline-or-truststore-public-keys-grouping { refine "inline-or-truststore/inline/inline-definition/" + "public-key" { must 'derived-from-or-self(public-key-format,' + ' "ct:subject-public-key-info-format")'; } refine "inline-or-truststore/central-truststore/" + "central-truststore-reference" { must 'not(deref(.)/../ts:public-key/ts:public-key-' + 'format[not(derived-from-or-self(., "ct:subject-' + 'public-key-info-format"))])'; } } } leaf tls12-psks { if-feature "client-auth-tls12-psk"; type empty; description "Indicates that the TLS server can authenticate TLS clients using configured PSKs (pre-shared or pairwise symmetric keys). No configuration is required since the PSK value is the same as PSK value configured in the 'server-identity' node."; } leaf tls13-epsks { if-feature "client-auth-tls13-epsk"; type empty; description "Indicates that the TLS 1.3 server can authenticate TLS clients using configured External PSKs (pre-shared keys). No configuration is required since the PSK value is the same as PSK value configured in the 'server-identity' node."; } } // container client-authentication container hello-params { nacm:default-deny-write; if-feature "tlscmn:hello-params"; uses tlscmn:hello-params-grouping; description "Configurable parameters for the TLS hello message."; } // container hello-params container keepalives { nacm:default-deny-write; if-feature "tls-server-keepalives"; description "Configures the keepalive policy for the TLS server."; leaf peer-allowed-to-send { type empty; description "Indicates that the remote TLS client is allowed to send HeartbeatRequest messages, as defined by RFC 6520, to this TLS server."; reference "RFC 6520: Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) Heartbeat Extension"; } container test-peer-aliveness { presence "Indicates that the TLS server proactively tests the aliveness of the remote TLS client."; description "Configures the keepalive policy to proactively test the aliveness of the TLS client. An unresponsive TLS client is dropped after approximately max-wait * max-attempts seconds."; leaf max-wait { type uint16 { range "1..max"; } units "seconds"; default "30"; description "Sets the amount of time in seconds, after which a TLS-level message will be sent to test the aliveness of the TLS client if no data has been received from the TLS client."; } leaf max-attempts { type uint8; default "3"; description "Sets the maximum number of sequential keepalive messages that can fail to obtain a response from the TLS client before assuming the TLS client is no longer alive."; } } } // container keepalives } // grouping tls-server-grouping } ]]>
Security Considerations The three IETF YANG modules in this document define groupings and will not be deployed as standalone modules. Their security implications may be context dependent based on their use in other modules. The designers of modules that import these grouping must conduct their own analysis of the security considerations.
Considerations for the "iana-tls-cipher-suite-algs" YANG Module This section is modeled after the template defined in . The "iana-tls-cipher-suite-algs" YANG module defines a data model that is designed to be accessed via YANG-based management protocols, such as NETCONF and RESTCONF . These protocols have mandatory-to-implement secure transport layers (e.g., Secure Shell (SSH) , TLS , and QUIC ) and mandatory-to-implement mutual authentication. The Network Configuration Access Control Model (NACM) provides the means to restrict access for particular users to a preconfigured subset of all available protocol operations and content. This YANG module defines YANG enumerations, for a public IANA-maintained registry. YANG enumerations are not security-sensitive, as they are statically defined in the publicly accessible YANG module. IANA MAY deprecate and/or obsolete enumerations over time as needed to address security issues found in the algorithms. This module does not define any writable nodes, RPCs, actions, or notifications, and thus the security considerations for such are not provided here.
Considerations for the "ietf-tls-common" YANG Module This section is modeled after the template defined in . The "ietf-tls-common" YANG module defines a data model that is designed to be accessed via YANG-based management protocols, such as NETCONF and RESTCONF . These protocols have mandatory-to-implement secure transport layers (e.g., Secure Shell (SSH) , TLS , and QUIC ) and mandatory-to-implement mutual authentication. The Network Configuration Access Control Model (NACM) provides the means to restrict access for particular users to a preconfigured subset of all available protocol operations and content. Please be aware that this YANG module uses groupings from other YANG modules that define nodes that may be considered sensitive or vulnerable in network environments. Please review the Security Considerations for dependent YANG modules for information as to which nodes may be considered sensitive or vulnerable in network environments. None of the readable data nodes defined in this YANG module are considered sensitive or vulnerable in network environments. The NACM "default-deny-all" extension has not been set for any data nodes defined in this module. None of the writable data nodes defined in this YANG module are considered sensitive or vulnerable in network environments. The NACM "default-deny-write" extension has not been set for any data nodes defined in this module. This module defines the "generate-asymmetric-key-pair" RPC that may, if the "ct:cleartext-private-keys" feature is enabled and the client requests it, return the private clear in cleartext form. It is NOT RECOMMENDED for private keys to pass the server's security perimeter. This module does not define any actions or notifications, and thus the security considerations for such are not provided here.
Considerations for the "ietf-tls-client" YANG Module This section is modeled after the template defined in . The "ietf-tls-client" YANG module defines a data model that is designed to be accessed via YANG-based management protocols, such as NETCONF and RESTCONF . These protocols have mandatory-to-implement secure transport layers (e.g., Secure Shell (SSH) , TLS , and QUIC ) and mandatory-to-implement mutual authentication. The Network Configuration Access Control Model (NACM) provides the means to restrict access for particular users to a preconfigured subset of all available protocol operations and content. Please be aware that this YANG module uses groupings from other YANG modules that define nodes that may be considered sensitive or vulnerable in network environments. Please review the Security Considerations for dependent YANG modules for information as to which nodes may be considered sensitive or vulnerable in network environments. None of the readable data nodes defined in this YANG module are considered sensitive or vulnerable in network environments. The NACM "default-deny-all" extension has not been set for any data nodes defined in this module. All the writable data nodes defined by this module may be considered sensitive or vulnerable in some network environments. For instance, any modification to a key or reference to a key may dramatically alter the implemented security policy. For this reason, the NACM extension "default-deny-write" has been set for all data nodes defined in this module. This module does not define any RPCs, actions, or notifications, and thus the security considerations for such are not provided here.
Considerations for the "ietf-tls-server" YANG Module This section is modeled after the template defined in . The "ietf-tls-server" YANG module defines a data model that is designed to be accessed via YANG-based management protocols, such as NETCONF and RESTCONF . These protocols have mandatory-to-implement secure transport layers (e.g., Secure Shell (SSH) , TLS , and QUIC ) and mandatory-to-implement mutual authentication. The Network Configuration Access Control Model (NACM) provides the means to restrict access for particular users to a preconfigured subset of all available protocol operations and content. Please be aware that this YANG module uses groupings from other YANG modules that define nodes that may be considered sensitive or vulnerable in network environments. Please review the Security Considerations for dependent YANG modules for information as to which nodes may be considered sensitive or vulnerable in network environments. None of the readable data nodes defined in this YANG module are considered sensitive or vulnerable in network environments. The NACM "default-deny-all" extension has not been set for any data nodes defined in this module. Please be aware that this module uses the "key" and "private-key" nodes from the "ietf-crypto-types" module , where said nodes have the NACM extension "default-deny-all" set, thus preventing unrestricted read access to the cleartext key values. All the writable data nodes defined by this module may be considered sensitive or vulnerable in some network environments. For instance, any modification to a key or reference to a key may dramatically alter the implemented security policy. For this reason, the NACM extension "default-deny-write" has been set for all data nodes defined in this module. This module does not define any RPCs, actions, or notifications, and thus the security considerations for such are not provided here.
IANA Considerations
The IETF XML Registry IANA has registered the following four URIs in the "ns" registry of the "IETF XML Registry" .
URI:
urn:ietf:params:xml:ns:yang:iana-tls-cipher-suite-algs
Registrant Contact:
The IESG
XML:
N/A; the requested URI is an XML namespace.
URI:
urn:ietf:params:xml:ns:yang:ietf-tls-common
Registrant Contact:
The IESG
XML:
N/A; the requested URI is an XML namespace.
URI:
urn:ietf:params:xml:ns:yang:ietf-tls-client
Registrant Contact:
The IESG
XML:
N/A; the requested URI is an XML namespace.
URI:
urn:ietf:params:xml:ns:yang:ietf-tls-server
Registrant Contact:
The IESG
XML:
N/A; the requested URI is an XML namespace.
The YANG Module Names Registry IANA has registered the following four YANG modules in the "YANG Module Names" registry .
name:
iana-tls-cipher-suite-algs
Maintained by IANA:
Y
namespace:
urn:ietf:params:xml:ns:yang:iana-tls-cipher-suite-algs
prefix:
tlscsa
reference:
RFC 9645
name:
ietf-tls-common
Maintained by IANA:
N
namespace:
urn:ietf:params:xml:ns:yang:ietf-tls-common
prefix:
tlscmn
reference:
RFC 9645
name:
ietf-tls-client
Maintained by IANA:
N
namespace:
urn:ietf:params:xml:ns:yang:ietf-tls-client
prefix:
tlsc
reference:
RFC 9645
name:
ietf-tls-server
Maintained by IANA:
N
namespace:
urn:ietf:params:xml:ns:yang:ietf-tls-server
prefix:
tlss
reference:
RFC 9645
Considerations for the "iana-tls-cipher-suite-algs" YANG Module This section follows the template defined in . IANA used the script in to generate the IANA-maintained "iana-tls-cipher-suite-algs" YANG module. The YANG module is available from the "YANG Parameters" registry . IANA has added the following note to the registry:
New values must not be directly added to the "iana-tls-cipher-suite-algs" YANG module. They must instead be added to the "TLS Cipher Suites" registry in the "Transport Layer Security (TLS) Parameters" registry group .
When a value is added to the "TLS Cipher Suites" registry, a new "enum" statement must be added to the "iana-tls-cipher-suite-algs" YANG module. The "enum" statement, and substatements thereof, should be defined as follows:
enum
Replicates a name from the registry.
value
Contains the decimal value of the IANA-assigned value.
status
Include only if a registration has been deprecated or obsoleted. An IANA "Recommended" value "N" maps to YANG status "deprecated". Since the registry is unable to express a logical "MUST NOT" recommendation, there is no mapping to YANG status "obsolete", which is unfortunate given the moving of single-DES and International Data Encryption Algorithm (IDEA) TLS cipher suites to Historic .
description
Contains "Enumeration for the 'TLS_FOO' algorithm", where "TLS_FOO" is a placeholder for the algorithm's name (e.g., "TLS_PSK_WITH_AES_256_CBC_SHA").
reference
Replicates the reference(s) from the registry with the title of the document(s) added.
Unassigned or reserved values are not present in the module. When the "iana-tls-cipher-suite-algs" YANG module is updated, a new "revision" statement with a unique revision date must be added in front of the existing revision statements. The "revision" must have a "description" statement explaining why the the update occurred and must have a "reference" substatement that points to the document defining the registry update that resulted in this change. For instance: IANA has added the following note to the "TLS Cipher Suites" registry under the "Transport Layer Security (TLS) Parameters" registry group .
When this registry is modified, the YANG module "iana-tls-cipher-suite-algs" must be updated as defined in RFC 9645.
 References Normative References YANG Data Types and Groupings for Cryptography Watsen Networks A YANG Data Model for a Truststore Watsen Networks A YANG Data Model for a Keystore Watsen Networks Secure Hash Standard (SHS) National Institute of Standards and Technology (NIST) Digital Signature Standard (DSS) National Institute of Standards and Technology (NIST) Informative References YANG Groupings for TCP Clients and TCP Servers Watsen Networks Hochschule Esslingen - University of Applied Sciences YANG Groupings for SSH Clients and SSH Servers Watsen Networks TLS Cipher Suites IANA YANG Parameters IANA Extensible Markup Language (XML) 1.0 (Fifth Edition) W3C Recommendation REC-xml-20081126
Script to Generate IANA-Maintained YANG Modules This section is not normative. The Python script contained in this section was used to create the initial IANA-maintained "iana-tls-cipher-suite-algs" YANG module maintained at . Run the script using the command 'python gen-yang-modules.py' to produce the YANG module file in the current directory. Be aware that the script does not attempt to copy the "revision" statements from the previous/current YANG module. Copying the revision statements must be done manually. "; description "This module defines enumerations for the cipher suite algorithms defined in the 'TLS Cipher Suites' registry under the 'Transport Layer Security (TLS) Parameters' registry group maintained by IANA. Copyright (c) 2024 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). The initial version of this YANG module is part of RFC 9645 (https://www.rfc-editor.org/info/rfc9645); see the RFC itself for full legal notices. All versions of this module are published by IANA (https://www.iana.org/assignments/yang-parameters)."; revision DATE { description "This initial version of the module was created using the script defined in RFC 9645 to reflect the contents of the SNAME algorithms registry maintained by IANA."; reference "RFC 9645: YANG Groupings for TLS Clients and TLS Servers"; } typedef tls-HNAME-algorithm { type enumeration { """ # Replacements rep = { "DATE": datetime.today().strftime('%Y-%m-%d'), "YEAR": datetime.today().strftime('%Y'), "SNAME": module["spaced_name"], "HNAME": module["hyphenated_name"], "PREFIX": module["prefix"] } # Do the replacement rep = dict((re.escape(k), v) for k, v in rep.items()) pattern = re.compile("|".join(rep.keys())) text = pattern.sub(lambda m: rep[re.escape(m.group(0))], PREAMBL\ \E_TEMPLATE) # Write preamble into the file f.write(text) def create_module_body(module, f): # Fetch the current CSV file from IANA r = requests.get(module["csv_url"]) assert r.status_code == 200, "Could not get " + module["csv_url"] # Parse each CSV line with StringIO(r.text) as csv_file: csv_reader = csv.DictReader(csv_file) for row in csv_reader: # Skip reserved algs if row["Description"].startswith("Unassigned"): continue # Skip unassigned algs if row["Description"].startswith("Reserved"): continue # Ensure this is the TLS line assert row["Description"].startswith("TLS_"), "Unrecogni\ \zed description: '" + row["Description"] + "'" # Set the 'refs' and 'titles' lists if row["Reference"] == "": pass # skip when the Reference field is empty else: # There may be more than one ref refs = row["Reference"][1:-1] # remove the '[' and \ \']' chars refs = refs.split("][") titles = [] for ref in refs: # Ascertain the ref's title if ref.startswith("RFC"): # Fetch the current BIBTEX entry bibtex_url="https://datatracker.ietf.org/doc\ \/"+ ref.lower() + "/bibtex/" r = requests.get(bibtex_url) assert r.status_code == 200, "Could not GET \ \" + bibtex_url # Append to 'titles' value from the "title" \ \line for item in r.text.split("\n"): if "title =" in item: title = re.sub('.*{{(.*)}}.*', r'\g<\ \1>', item) if title.startswith("ECDHE\_PSK"): title = re.sub("ECDHE\\\\_PSK", \ \"ECDHE_PSK", title) titles.append(re.sub('.*{{(.*)}}.*',\ \ r'\g<1>', title)) break else: raise Exception("RFC title not found") # Insert a space: "RFC9645" --> "RFC 9645" index = refs.index(ref) refs[index] = "RFC " + ref[3:] elif ref == "IESG Action 2018-08-16": # Rewrite the ref value index = refs.index(ref) refs[index] = "IESG Action" # Let title be something descriptive titles.append("IESG Action 2018-08-16") elif ref == "draft-irtf-cfrg-aegis-aead-08": # Manually set the document's title titles.append("The AEGIS Family of Authentic\ \ated Encryption Algorithms") elif ref: raise Exception(f'ref "{ref}" not found') else: raise Exception(f'ref missing: {row}') # Write out the enum f.write(f' enum {row["Description"]} {{\n'); if row["Recommended"] == 'N': f.write(f' status deprecated;\n') f.write(f' description\n') description = f' "Enumeration for the \'{row["D\ \escription"]}\' algorithm.";' description = textwrap.fill(description, width=69, subse\ \quent_indent=" ") f.write(f'{description}\n') f.write(' reference\n') f.write(' "') if row["Reference"] == "": f.write('Missing in IANA registry.') else: ref_len = len(refs) for i in range(ref_len): ref = refs[i] f.write(f'{ref}:\n') title = " " + titles[i] if i == ref_len - 1: title += '";' title = textwrap.fill(title, width=69, subsequen\ \t_indent=" ") f.write(f'{title}') if i != ref_len - 1: f.write('\n ') f.write('\n') f.write(' }\n') def create_module_end(module, f): # Close out the enumeration, typedef, and module f.write(" }\n") f.write(" description\n") f.write(f' "An enumeration for TLS {module["spaced_name"]} \ \algorithms.";\n') f.write(" }\n") f.write('\n') f.write('}\n') def create_module(module): # Install cache for 8x speedup requests_cache.install_cache() # Ascertain the yang module's name yang_module_name = "iana-tls-" + module["hyphenated_name"] + "-a\ \lgs.yang" # Create yang module file with open(yang_module_name, "w") as f: create_module_begin(module, f) create_module_body(module, f) create_module_end(module, f) def main(): for module in MODULES: create_module(module) if __name__ == "__main__": main() ]]>
Acknowledgements The authors would like to thank the following for lively discussions on list and in the halls (ordered by first name): , , , , , , , , , , , , , , , , , , , , , , , , , , , , and .
Contributors Special acknowledgement goes to who contributed the "ietf-tls-common" module and who carefully ensured that references were set correctly throughout.