A Method for Changing Cleartext Passwords in the Extensible Authentication Protocol
draft-zorn-emu-eap-pwc-00

Abstract

The Extensible Authentication Protocol (EAP) provides support for multiple authentication methods. One such method is Generic Token Card (EAP-GTC) which, despite its name, is commonly used to support authentication using cleartext passwords in tunneled EAP methods. EAP-GTC does not provide the ability to change a password (for example, an expired password), however. This document defines the PassWord Change EAP method (EAP-PWC) in order to fill that void in functionality.

Status of this Memo

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This Internet-Draft will expire on September 08, 2011.

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Table of Contents

• 1. Introduction
• 2. Requirements Language
• 3. EAP-PWC
• 4. Security Considerations
• 5. IANA Considerations
• 6. References
• 6.1. Normative References
• 6.2. Informative References
• Author's Address

1. Introduction

The Generic Token Card EAP method (EAP-GTC) [RFC3748] is commonly used to support authentication using cleartext passwords in tunneled EAP methods. However, EAP-GTC does not provide the ability to change a password (for example, one which is about to expire). This document defines the PassWord Change EAP method (EAP-PWC) in order to fill that void in EAP functionality.

2. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

3. EAP-PWC

Description

If the EAP authenticator determines that the password should be changed as a result of the evaluation of the EAP/Identity response, it SHOULD send an EAP-PWC/Request to the peer. The Request contains a pair of displayable messages separated by the NUL character (0x00) and the Response contains the old and new passwords, also separated by a single NUL character. A Response MUST be sent in reply to the Request. The Response MUST be of Type <TBD> (PWC), Nak (Type 3), or Expanded Nak (Type 254) [RFC3748]. The Nak Response indicates the peer's desired authentication Type(s). The EAP-PWC method MUST NOT be used to provide support for cleartext password change in the absence of a protected tunnel with server authentication (e.g., TEAM [I-D.zorn-emu-team]).

Type

<TBD>

Type-Data

The Type-Data field in the Request contains a displayable message concatenated with a single NUL character concatenated with a displayable message. Each of the messages MUST be individually processed according to the rules of the [RFC4013] profile of [RFC3454] before the concatenation is performed. The messages SHALL be considered to be "stored strings" per [RFC3454], and unassigned code points are therefore prohibited. The output SHALL be the binary representation of the processed UTF-8 character string. Prohibited output and unassigned codepoints encountered in SASLprep pre-processing SHALL cause a failure of pre-processing, and the output SHALL NOT be used with EAP-PWC.

The Type-Data field in the Response contains the old password concatenated with a single NUL character concatenated with the new password. Each of the strings MUST be individually processed according to the rules of the [RFC4013] profile of [RFC3454] before the concatenation is performed. The passwords SHALL be considered to be "stored strings" per [RFC3454], and unassigned code points are therefore prohibited. The output SHALL be the binary representation of the processed UTF-8 character string. Prohibited output and unassigned codepoints encountered in SASLprep pre-processing SHALL cause a failure of pre-processing, and the output SHALL NOT be used with EAP-PWC.

Security Claims

Auth. mechanism:

Cleartext password

Ciphersuite negotiation:

No

Mutual authentication:

No

Integrity protection:

No

Replay protection:

No

Confidentiality:

No

Key derivation:

No

Key strength:

N/A

Dictionary attack prot.:

No

Fast reconnect:

No

Crypto binding:

N/A

Session independence:

N/A

Fragmentation:

No

Channel binding:

No

4. Security Considerations

The EAP-PWC method MUST NOT be used in the absence of a cryptographically protected tunnel with server authentication.

5. IANA Considerations

This memo requires IANA to allocate a new EAP method type for EAP-PWC. The placeholder indicated by <TBD> in Section 3 above shall be replaced by the new EAP method type upon assignment by IANA.

6. References

6.1. Normative References

6.2. Informative References

Author's Address