X.509 Certificate Extension for 5G Network Function TypesVigil Security, LLCHerndonVAUnited States of Americahousley@vigilsec.comsn3rdWashingtonDCUnited States of Americasean@sn3rd.comEricssonKistaSwedenjohn.mattsson@ericsson.comEricssonSaint Laurent, QCCanadadaniel.migault@ericsson.com
Security
lampsDigital CertificateThis document specifies the certificate extension for including
Network Function Types (NFTypes) for the 5G System in X.509 v3 public
key certificates as profiled in RFC 5280.Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by
the Internet Engineering Steering Group (IESG). Further
information on Internet Standards is available in Section 2 of
RFC 7841.
Information about the current status of this document, any
errata, and how to provide feedback on it may be obtained at
.
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Table of Contents
. Introduction
. Terminology
. Network Function Types Certificate Extension
. ASN.1 Module
. Security Considerations
. Privacy Considerations
. IANA Considerations
. References
. Normative References
. Informative References
. NFType Strings
. Example Certificate Containing a NFTypes Extension
Acknowledgements
Authors' Addresses
IntroductionThe 3rd Generation Partnership Project (3GPP) has specified several
Network Functions (NFs) as part of the service-based architecture within
the 5G System. There are 56 NF Types defined for 3GPP Release 17; they
are listed in Table 6.1.6.3.3-1 of , and each NF type is
identified by a short ASCII string.Operators of 5G Systems make use of an internal PKI to identify
interface instances in the NFs in a 5G System. X.509 v3 public key
certificates are used, and the primary function of a
certificate is to bind a public key to the identity of an entity that
holds the corresponding private key, known as the certificate subject.
The certificate subject and the SubjectAltName certificate extension can
be used to support identity-based access control decisions.This document specifies the NFTypes certificate extension to support
role-based access control decisions by providing a list of NF Types
associated with the certificate subject. The NFTypes certificate
extension can be used by operators of 5G Systems or later.TerminologyThe 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.Network Function Types Certificate ExtensionThis section specifies the NFTypes certificate extension, which provides
a list of NF Types associated with the certificate subject.The NFTypes certificate extension MAY be included in public key certificates
. The NFTypes certificate extension MUST be identified by the
following object identifier:
id-pe-nftype OBJECT IDENTIFIER ::=
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-pe(1) 34 }
This extension MUST NOT be marked critical.The NFTypes extension MUST have the following syntax:
NFTypes ::= SEQUENCE SIZE (1..MAX) OF NFType
NFType ::= IA5String (SIZE (1..32))
The NFTypes MUST contain at least one NFType.Each NFType MUST contain only an ASCII string; however, the
string MUST NOT include control characters (values 0 through 31),
the space character (value 32), or the delete character (value 127).Each NFType MUST contain at least one ASCII character and
MUST NOT contain more than 32 ASCII characters.The NFTypes MUST NOT contain the same NFType more than once.If the NFTypes contain more than one NFType, the NFTypes
MUST appear in ascending lexicographic order using the ASCII values.The NFType uses the IA5String type to permit inclusion of the underscore
character ('_'), which is not part of the PrintableString character set.ASN.1 ModuleThis section provides an ASN.1 Module for the NFTypes
certificate extension, and it follows the conventions established
in and .
NFTypeCertExtn
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-nftype(106) }
DEFINITIONS IMPLICIT TAGS ::=
BEGIN
IMPORTS
EXTENSION
FROM PKIX-CommonTypes-2009 -- RFC 5912
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-pkixCommon-02(57) } ;
-- NFTypes Certificate Extension
ext-NFType EXTENSION ::= {
SYNTAX NFTypes
IDENTIFIED BY id-pe-nftype }
-- NFTypes Certificate Extension OID
id-pe-nftype OBJECT IDENTIFIER ::=
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-pe(1) 34 }
-- NFTypes Certificate Extension Syntax
NFTypes ::= SEQUENCE SIZE (1..MAX) OF NFType
NFType ::= IA5String (SIZE (1..32))
END
Security ConsiderationsThe security considerations of are applicable to this document.Some of the ASCII strings that specify the NF Types are standard. See
for values defined in 3GPP Release 17. Additionally, an operator MAY
assign its own NF Types for use in their own network. Since the NF Type
is used for role-based access control decisions, an operator-assigned
NF Type MUST NOT overlap with a value already defined in the commonly
defined set. Use of the same ASCII string by two different operators
for different roles could lead to confusion or incorrect access control
decisions. The mechanism for an operator to determine whether an ASCII
string associated with a NF Type is unique across operators is outside
the scope of this document.The certificate extension supports many different forms of role-based
access control to support the diversity of activities that NFs are
trusted to perform in the overall system. Different levels of confidence
that the NFTypes were properly assigned might be needed to contribute to the
overall security of the 5G System. For example, more confidence might be
needed to make access control decisions related to a scarce resource than
implementation of filtering policies. As a result, different operators
might have different trust models for the NFTypes certificate extension.Privacy ConsiderationsIn some security protocols, such as TLS 1.2 , certificates are
exchanged in the clear. In other security protocols, such as TLS 1.3 ,
the certificates are encrypted. The inclusion of the NFTypes certificate extension
can help an observer determine which systems are of most interest based on
the plaintext certificate transmission.IANA ConsiderationsFor the NFTypes certificate extension defined in , IANA has
assigned an object identifier (OID) for the certificate extension. The
OID for the certificate extension has been allocated in the "SMI Security
for PKIX Certificate Extension" registry (1.3.6.1.5.5.7.1).For the ASN.1 Module defined in , IANA has assigned an
OID for the module identifier. The OID for the module
has been allocated in the "SMI Security for PKIX Module Identifier"
registry (1.3.6.1.5.5.7.0).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.Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) ProfileThis memo profiles the X.509 v3 certificate and X.509 v2 certificate revocation list (CRL) for use in the Internet. An overview of this approach and model is provided as an introduction. The X.509 v3 certificate format is described in detail, with additional information regarding the format and semantics of Internet name forms. Standard certificate extensions are described and two Internet-specific extensions are defined. A set of required certificate extensions is specified. The X.509 v2 CRL format is described in detail along with standard and Internet-specific extensions. An algorithm for X.509 certification path validation is described. An ASN.1 module and examples are provided in the appendices. [STANDARDS-TRACK]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.Technical Specification Group Core Network and Terminals; 5G System; Network Function Repository Services; Stage 3 (Release 17)3rd Generation Partnership Project3GPP TS:29.510 V17.8.0Technical Specification Group Services and System Aspects; Network Domain Security (NDS); Authentication Framework (AF) (Release 17)3rd Generation Partnership Project3GPP TS:33.310 V17.5.0Information technology -- Abstract Syntax Notation One (ASN.1): Specification of basic notationITU-TITU-T Recommendation X.680ISO/IEC 8824-1:2021Informative ReferencesThe Transport Layer Security (TLS) Protocol Version 1.2This document specifies Version 1.2 of the Transport Layer Security (TLS) protocol. The TLS protocol provides communications security over the Internet. The protocol allows client/server applications to communicate in a way that is designed to prevent eavesdropping, tampering, or message forgery. [STANDARDS-TRACK]New ASN.1 Modules for the Public Key Infrastructure Using X.509 (PKIX)The Public Key Infrastructure using X.509 (PKIX) certificate format, and many associated formats, are expressed using ASN.1. The current ASN.1 modules conform to the 1988 version of ASN.1. This document updates those ASN.1 modules to conform to the 2002 version of ASN.1. There are no bits-on-the-wire changes to any of the formats; this is simply a change to the syntax. This document is not an Internet Standards Track specification; it is published for informational purposes.Additional New ASN.1 Modules for the Cryptographic Message Syntax (CMS) and the Public Key Infrastructure Using X.509 (PKIX)The Cryptographic Message Syntax (CMS) format, and many associated formats, are expressed using ASN.1. The current ASN.1 modules conform to the 1988 version of ASN.1. This document updates some auxiliary ASN.1 modules to conform to the 2008 version of ASN.1; the 1988 ASN.1 modules remain the normative version. There are no bits- on-the-wire changes to any of the formats; this is simply a change to the syntax. This document is not an Internet Standards Track specification; it is published for informational purposes.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.Technical Specification Group Core Network and Terminals; 5G System; Common Data Types for Service Based Interfaces; Stage 3 (Release 17)3rd Generation Partnership Project3GPP TS:29.571 V17.8.0NFType StringsTable 6.1.6.3.3-1 of defines the ASCII strings for the
NF Types specified in 3GPP documents; these enumeration values in 3GPP Release 17 are listed below in
ascending lexicographic order. This list is not exhaustive.
"5G_DDNMF" "LMF" "PKMF"
"5G_EIR" "MBSF" "SCEF"
"AANF" "MBSTF" "SCP"
"ADRF" "MB_SMF" "SCSAS"
"AF" "MB_UPF" "SCSCF"
"AMF" "MFAF" "SEPP"
"AUSF" "MME" "SMF"
"BSF" "MNPF" "SMSF"
"CBCF" "N3IWF" "SMS_GMSC"
"CEF" "NEF" "SMS_IWMSC"
"CHF" "NRF" "SOR_AF"
"DCCF" "NSACF" "SPAF"
"DRA" "NSSAAF" "TSCTSF"
"EASDF" "NSSF" "UCMF"
"GBA_BSF" "NSWOF" "UDM"
"GMLC" "NWDAF" "UDR"
"HSS" "PANF" "UDSF"
"ICSCF" "PCF" "UPF"
"IMS_AS" "PCSCF"
Example Certificate Containing a NFTypes ExtensionThe example certificate conforms to the certificate profile in
Table 6.1.3c.3-1 of . In addition, the NFTypes
certificate is included with only one NFType, and it is "AMF". The
SubjectAltName certificate extension contains a fully qualified domain
name (FQDN) and a uniformResourceIdentifier, which carries the
NF Instance ID as specified in Clause 5.3.2 of .
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
The following shows the example certificate. The values on the left
are the ASN.1 tag (in hexadecimal) and the length (in decimal).
30 720: SEQUENCE {
30 598: SEQUENCE {
A0 3: [0] {
02 1: INTEGER 2
: }
02 20: INTEGER
: 0C 3E 68 E3 8C C4 75 F4 A0 85 3D A1 30 AF 8F FC
: 48 C6 1E 5A
30 10: SEQUENCE {
06 8: OBJECT IDENTIFIER ecdsaWithSHA384 (1 2 840 10045 4 3 3)
: }
30 21: SEQUENCE {
31 19: SET {
30 17: SEQUENCE {
06 3: OBJECT IDENTIFIER organizationName (2 5 4 10)
0C 10: UTF8String 'Example CA'
: }
: }
: }
30 30: SEQUENCE {
17 13: UTCTime 29/11/2022 18:14:58 GMT
17 13: UTCTime 29/11/2023 18:14:58 GMT
: }
30 57: SEQUENCE {
31 11: SET {
30 9: SEQUENCE {
06 3: OBJECT IDENTIFIER countryName (2 5 4 6)
13 2: PrintableString 'US'
: }
: }
31 42: SET {
30 40: SEQUENCE {
06 3: OBJECT IDENTIFIER organizationName (2 5 4 10)
13 33: PrintableString '5gc.mnc400.mcc311.3gppnetwork.org'
: }
: }
: }
30 118: SEQUENCE {
30 16: SEQUENCE {
06 7: OBJECT IDENTIFIER ecPublicKey (1 2 840 10045 2 1)
06 5: OBJECT IDENTIFIER secp384r1 (1 3 132 0 34)
: }
03 98: BIT STRING
: 04 C9 E8 81 47 23 AF 37 AB F2 49 8E C2 54 7C 48
: 91 16 A1 90 EA E2 83 18 9D 28 A8 33 FA C0 48 51
: 02 EB F2 13 2C F9 A6 04 66 CF FE CC CD ED 7E B3
: 5A 9C 9C F5 3D 9A 8D 6F AC 85 BD AE 32 A1 6F F1
: E6 F0 7F 53 3E F9 CC 43 00 91 0A D2 AF 08 3F 74
: 32 45 AF 73 F1 BC AB 20 81 A4 29 AC DF 33 4E 24
: E8
: }
A3 321: [3] {
30 317: SEQUENCE {
30 19: SEQUENCE {
06 8: OBJECT IDENTIFIER nfTypes (1 3 6 1 5 5 7 1 34)
04 7: OCTET STRING, encapsulates {
30 5: SEQUENCE {
16 3: IA5String 'AMF'
: }
: }
: }
30 23: SEQUENCE {
06 3: OBJECT IDENTIFIER certificatePolicies (2 5 29 32)
04 16: OCTET STRING, encapsulates {
30 14: SEQUENCE {
30 12: SEQUENCE {
06 10: OBJECT IDENTIFIER '2 16 840 1 101 3 2 1 48 48'
: }
: }
: }
: }
30 14: SEQUENCE {
06 3: OBJECT IDENTIFIER keyUsage (2 5 29 15)
01 1: BOOLEAN TRUE
04 4: OCTET STRING, encapsulates {
03 2: BIT STRING 7 unused bits
: '1'B (bit 0)
: }
: }
30 19: SEQUENCE {
06 3: OBJECT IDENTIFIER extKeyUsage (2 5 29 37)
04 12: OCTET STRING, encapsulates {
30 10: SEQUENCE {
06 8: OBJECT IDENTIFIER clientAuth (1 3 6 1 5 5 7 3 2)
: }
: }
: }
30 29: SEQUENCE {
06 3: OBJECT IDENTIFIER subjectKeyIdentifier (2 5 29 14)
04 22: OCTET STRING, encapsulates {
04 20: OCTET STRING
: 4C 67 92 A0 C1 89 58 9F CF 39 98 A2 03 E7 96 5C
: 13 39 C8 07
: }
: }
30 31: SEQUENCE {
06 3: OBJECT IDENTIFIER authorityKeyIdentifier (2 5 29 35)
04 24: OCTET STRING, encapsulates {
30 22: SEQUENCE {
80 20: [0]
: 88 7F A2 04 E9 0B 6A 8D 74 76 FA 9F F1 0A D4 61
: E0 FA B3 35
: }
: }
: }
30 49: SEQUENCE {
06 3: OBJECT IDENTIFIER cRLDistributionPoints (2 5 29 31)
04 42: OCTET STRING, encapsulates {
30 40: SEQUENCE {
30 38: SEQUENCE {
A0 36: [0] {
A0 34: [0] {
86 32: [6] 'http://example.com/exampleca.crl'
: }
: }
: }
: }
: }
: }
30 117: SEQUENCE {
06 3: OBJECT IDENTIFIER subjectAltName (2 5 29 17)
01 1: BOOLEAN TRUE
04 107: OCTET STRING, encapsulates {
30 105: SEQUENCE {
82 56: [2]
: 'amf1.cluster1.net2.amf.5gc.mnc400.mcc311.3gppnet'
: 'work.org'
86 45: [6]
: 'urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6'
: }
: }
: }
: }
: }
: }
30 10: SEQUENCE {
06 8: OBJECT IDENTIFIER ecdsaWithSHA384 (1 2 840 10045 4 3 3)
: }
03 104: BIT STRING, encapsulates {
30 101: SEQUENCE {
02 48: INTEGER
: 4B 50 12 EB 7D 91 E9 64 88 C2 0C 47 E4 33 91 23
: 46 22 E4 77 D0 BA F6 DD FB 5A AC B8 BD C0 CA 77
: 65 12 09 61 08 1A 01 67 3A 82 67 F7 31 50 29 ED
02 49: INTEGER
: 00 A3 28 60 0B 70 E6 CA E4 36 31 3E 66 0E 82 A8
: 49 1F F5 FD 9B 6A 71 65 B5 1B 8F 6D 3A 78 07 45
: EB 6B 3E 73 FE 39 F7 34 33 CC F5 AB 5A 48 75 31
: 39
: }
: }
: }
AcknowledgementsMany thanks to , , , ,
, and for their review, comments, and assistance.Authors' AddressesVigil Security, LLCHerndonVAUnited States of Americahousley@vigilsec.comsn3rdWashingtonDCUnited States of Americasean@sn3rd.comEricssonKistaSwedenjohn.mattsson@ericsson.comEricssonSaint Laurent, QCCanadadaniel.migault@ericsson.com