Internet DRAFT - draft-rieckers-eapparameterextension
draft-rieckers-eapparameterextension
Network Working Group J. Rieckers
Internet-Draft Uni Bremen
Intended status: Standards Track November 02, 2019
Expires: May 5, 2020
X509v3 EAP Parameter Extension
draft-rieckers-eapparameterextension-00
Abstract
This document specifies an extension to X509v3 certificates for EAP-
TLS servers to mitigate some flaws in the specification to the use of
TLS in EAP as specified in RFC5216. The specified extension enables
clients to decide whether to trust the certificate presented by the
EAP-TLS server by including information implicitly defined by login
credentials or communication context in the server certificate.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
3. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. EAP Parameter Types . . . . . . . . . . . . . . . . . . . . . 4
4.1. Realm Suffix types . . . . . . . . . . . . . . . . . . . 4
4.1.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . 5
4.1.2. Validation . . . . . . . . . . . . . . . . . . . . . 5
4.1.3. CA Requirements . . . . . . . . . . . . . . . . . . . 5
4.2. Identity . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . 5
4.2.2. Validation . . . . . . . . . . . . . . . . . . . . . 6
4.2.3. CA Requirements . . . . . . . . . . . . . . . . . . . 6
4.3. Login Medium . . . . . . . . . . . . . . . . . . . . . . 6
4.3.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . 6
4.3.2. Validation . . . . . . . . . . . . . . . . . . . . . 6
4.3.3. CA Requirements . . . . . . . . . . . . . . . . . . . 6
4.4. Handling of future EAP Parameter Types . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. ASN.1 Modul . . . . . . . . . . . . . . . . . . . . 9
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Logging in with EAP-TLS based methods is a widely used mechanism for
password based login with protocols like RADIUS [RFC2865]. Two
mechanisms used in WPA2-Enterprise areas are EAP-TTLSv0 and EAP-
PEAPv0. Unfortunately, the specification of EAP-TLS does not specify
how the EAP-TLS peer can verify that the certificate presented by the
server is valid apart from the Key Usage identifiers and user set
configuration parameters.
The configuration parameters include especially the information about
the trust anchor and the expected domain.
In contrast to the usage of X509v3 certificates in other contexts,
such as HTTPS, in EAP-TLS the expected name can not be distinguished
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from the context of the communication. This requires users to
configure their supplicants accordingly. Especially in large setups
with private devices this has led to insecure configurations with
insufficient or even wrong name checks. Some security considerations
for EAP-TLS in deployment in eduroam have been named in [RFC7593],
Section 7.1.
The same basic security considerations apply for the certificate
based login methods as they apply for password based methods, but are
not that critical, since an attacker can not gain knowledge of the
supplicant's private key with an attack based on insufficient server
certificate validation done by the peer.
The aim of the extension introduced in this document is to give EAP-
TLS peers an option to check the certificate of the EAP-TLS server
against parameters implicitly defined by the communication context.
2. Definitions
2.1. Requirements 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 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2.2. Terminology
Readers are expected to be familiar with the terms and concepts used
in EAP [RFC3748] and EAP-TLS [RFC5216].
In particular, this document frequently uses the following terms:
EAP-TLS server: The entity that authenticates the clients and is
termination point of the EAP-TLS tunnel.
peer or supplicant: The client that authenticates to the server in
order to gain access to the protected resource.
EAP Identity: The Identity sent by the peer in the first
(unencrypted) EAP Identity Response as specified in [RFC3748]
Section 5.1.
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3. Syntax
TODO
There shall be a ASN.1 module in Appendix A
The EAP Parameter extension has the following format:
id-pe-eapparameter OBJECT IDENTIFIER ::= { id-pe XX }
EAPParameterValues ::= SEQUENCE {
EAPParameterType OBJECT IDENTIFIER,
EAPParameterValue OCTET STRING
}
EAPParameter ::= SEQUENCE OF (1..MAX) EAPParameterValues
The extnValue of the id-pe-eapparameter extension is the ASN.1 DER
encoding of the EAPParameter structure.
The EAP Parameter extension MAY be marked as critical. Certificate
Authorities SHOULD allow both, critical and not critical, in their
application process for a certificate with this extension, so
applicants can choose. Making the extension critical may not be
desirable in the early future after the release of this RFC, but,
when marked critical, it will help forcing users to update their
devices, which might be, at least in the authors opinion, a good
idea. This makes use of the specification of the handling of
critical extensions, specified in [RFC5280]: Any supplicant not
understanding a critical extension MUST reject the certificate if it
does not understand this extension.
4. EAP Parameter Types
This RFC specifies several EAP Parameter Types. Other parameter
types MAY be specified in the future. The handling of new parameters
is described in Section 4.4
4.1. Realm Suffix types
The Realm Suffix types can be used to bind the certificate to a
specific realm. It is either a realm separated by '@'
(EAPPARAMETERBASEOID.1) or a realm separated by '%'
(EAPPARAMETERBASEOID.2)
TODO: Reference to NAI [RFC7542] for Realms. Maybe even remove the
'%' seperated realm, since I have not found any usage. This is only
here because it is in a default configuration file of FreeRADIUS
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TODO: Replace EAPPARAMETERBASEOID with assigned OID
4.1.1. Syntax
The EAPParameterValue for these types is a DER-encoded UTF8String
containing the full realm of the outer username. This is supposed to
be a FQDN. It MAY not be a FQDN for testing purposes but MUST NOT
contain the separator character, depending on the Suffix type. The
value MAY contain one asterisk to indicate a wildcard validity for
all realms under a specific domain. The asterisk MUST be the first
character and MUST be followed by a dot. A certificate containing
only an asterisk and a dot MUST NOT be issued by a trusted
certificate authority.
4.1.2. Validation
To verify the supplicant will compare the sent EAP Identity with the
realm contained in the EAPParameterValue. If the EAPParameterValue
is not in a valid format, the supplicant MUST reject the certificate
and SHOULD send a fatal bad_certificate alert (see [RFC5246],
[RFC8446]). If the value contains an asterisk, the realm part should
be matched as the dnsName of subjectAltName attribute would be
matched.
4.1.3. CA Requirements
A trusted CA MUST validate that the applicant is authorized to
request certificates under the domain represented by the realm. CAs
SHOULD rely additionally on the CAA issuewild DNS value and SHOULD
NOT issue a certificate with this extension if the CAA value forbids
wildcard certificates.
4.2. Identity
EAPPARAMETERBASEOID.3
The Identity Parameter Type can be used to bind the server
certificate to use with a specific EAP Identity.
4.2.1. Syntax
The EAPParameterValue for this type is a DER-encoded UTF8String
containing the full EAP Identity.
The value MAY contain up to two asterisks, one for the local part of
the Identity, one for the realm. This can be used to allow EAP-
Identities with variable parts. If two asterisks are used, the
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certificate extension MUST also contain a EAPParameter for
verification of the Realm (e.g. Realm Suffix, separated by '@')
The asterisk for the realm part follows the same rules as described
in the Realm suffix type.
The asterisk for the local part MAY be at any position.
4.2.2. Validation
To verify this parameter the supplicant has to verify the sent EAP
Identity and the parameter value in the certificate match. The
supplicant SHOULD do this with a case insensitive comparison.
TODO: Here should also be a description how to deal with asterisks.
4.2.3. CA Requirements
The CA requirements for this type depend on the used Identity format.
If the Identity is in a format that would also allow Realm Suffix
Types (e.g. separated by @ or %) for the domain part the same CA
Requirements as for the defined Realm Suffix Types apply. CAs SHOULD
allow the local part to be chosen by the certificate requestor inside
normal parameters.
Globally trusted CAs MUST NOT issue certificates with the Identity
EAP Parameter Type if it does not contain a Realm or the Realm can
not be mapped to a DNS name.
4.3. Login Medium
EAPPARAMETERBASEOID.4
TODO
This is intended to limit the validity of the certificate to e.g.
802.1x authentication
4.3.1. Syntax
4.3.2. Validation
4.3.3. CA Requirements
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4.4. Handling of future EAP Parameter Types
TODO
5. IANA Considerations
TODO: Here the IANA considerations should be updated. The decimal id
of the id-pe-eapparameter will be registered once the draft has
reached a state where proof of concept implementations can be made.
On approval, IANA shall add in the SMI Security for PKIX Certificate
Extension (1.3.6.1.5.5.7.1) registry the following entry:
+----------+--------------------+------------+
| Deciamal | Description | References |
+----------+--------------------+------------+
| XX | id-pe-eapparameter | {this RFC} |
+----------+--------------------+------------+
Additionally the IANA shall install a new registry for PKIX
Certificate Extension EAP Parameter Types for the parameter types
with the following initial content:
+---------+--------------------------------+------------+
| Decimal | Description | References |
+---------+--------------------------------+------------+
| 1 | Realm Suffix, separated by '@' | {this RFC} |
| | | |
| 2 | Realm Suffix, separated by '%' | {this RFC} |
| | | |
| 3 | Identity | {this RFC} |
| | | |
| 4 | Login Medium | {this RFC} |
+---------+--------------------------------+------------+
TODO: Here there may be also defined Realm Prefix Types (e.g.
WINDOWS-NET/username). Obviously this can't be issued by a globally
trusted CA, but might be issued by a company CA
Further EAP Parameter Types may be registered in future. New
registration requests MUST include a detailed description how peers
should validate the given parameter and a detailed description for
Certificate Authorities how they must verify the authorization of a
certificate request with this parameter.
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6. Security Considerations
TODO
There will be security considerations. There are security
considerations which lead to this draft.
Here might be a reference to [RFC4334]. It specifies X509v3
extensions to help the supplicant to choose the client certificate
used for login based on connection parameters such as SSID or Login
Medium.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, Ed., "Extensible Authentication Protocol
(EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004,
<https://www.rfc-editor.org/info/rfc3748>.
[RFC5216] Simon, D., Aboba, B., and R. Hurst, "The EAP-TLS
Authentication Protocol", RFC 5216, DOI 10.17487/RFC5216,
March 2008, <https://www.rfc-editor.org/info/rfc5216>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542,
DOI 10.17487/RFC7542, May 2015,
<https://www.rfc-editor.org/info/rfc7542>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
7.2. Informative References
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)",
RFC 2865, DOI 10.17487/RFC2865, June 2000,
<https://www.rfc-editor.org/info/rfc2865>.
[RFC4334] Housley, R. and T. Moore, "Certificate Extensions and
Attributes Supporting Authentication in Point-to-Point
Protocol (PPP) and Wireless Local Area Networks (WLAN)",
RFC 4334, DOI 10.17487/RFC4334, February 2006,
<https://www.rfc-editor.org/info/rfc4334>.
[RFC7593] Wierenga, K., Winter, S., and T. Wolniewicz, "The eduroam
Architecture for Network Roaming", RFC 7593,
DOI 10.17487/RFC7593, September 2015,
<https://www.rfc-editor.org/info/rfc7593>.
Appendix A. ASN.1 Modul
This is obviously also an open TODO
Acknowledgements
There will be acknowledgements. I haven't done the work all by
myself and a lot of people should and will be listed here for
supporting me in all my work.
Carsten Bormann, ...
Author's Address
Jan-Frederik Rieckers
Universitaet Bremen
Bibliothekstr. 5
Bremen 28359
Germany
Email: rieckers@uni-bremen.de
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