Internet DRAFT - draft-privacy-token
draft-privacy-token
Network Working Group T. Pauly
Internet-Draft F. Jacobs
Intended status: Experimental Apple Inc.
Expires: 11 March 2022 C.A. Wood
Cloudflare
7 September 2021
The Privacy Token HTTP Authentication Scheme
draft-privacy-token-01
Abstract
This documents defines an authentication scheme for HTTP called
Privacy Token.
Discussion Venues
This note is to be removed before publishing as an RFC.
Source for this draft and an issue tracker can be found at
https://github.com/tfpauly/privacy-proxy.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 11 March 2022.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
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Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text
as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 2
2. Privacy Token Structure . . . . . . . . . . . . . . . . . . . 2
3. PrivacyToken Authentication Scheme . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Normative References . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
This document defines a new HTTP authentication scheme [RFC7235]
named "PrivacyToken".
This scheme is built to be used to authenticate to proxies, using the
Proxy-Authorization header field, with a blind signature that allows
a proxy to verify that a client has a token signed by a particular
key, but without identifying the client. The initial version of this
scheme is intended to be used with RSA Blind Signatures [RSASIG].
1.1. Requirements
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. Privacy Token Structure
A privacy token is a structure that begins with a single byte that
indicates a version. This document defines version, 1, which
indicates use of private tokens based on RSA Blind Signatures
[RSASIG], and determines the rest of the structure contents.
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struct {
uint8_t version;
uint8_t key_id[32];
uint8_t message[32];
uint8_t signature[Nk];
} Token;
The structure fields are defined as follows:
* "version" is a 1-octet integer. This document defines version 1.
* "key_id" is a collision-resistant hash that identifies the key
used to produce the signature. This is generated as
SHA256(public_key), where public_key is a DER-encoded
SubjectPublicKeyInfo object carrying the public key.
* "message" is a 32-octet random message that is signed by the
signature.
* "signature" is a Nk-octet RSA Blind Signature that covers the
message. For version 1, Nk is indicated by size of the Token
structure and may be 256, 384, or 512. These correspond to RSA
2048, 3072, and 4096 bit keys. Clients implementing version 1
MUST support signature sizes with Nk of 512 and 256.
3. PrivacyToken Authentication Scheme
The "PrivacyToken" authentication scheme defines one parameter,
"token". All unknown or unsupported parameters to "PrivacyToken"
authentication credentials MUST be ignored.
The value of the "token" parameter is a Privacy Token Structure
Section 2, encoded using base64url encoding [RFC4648].
As an example, a Proxy-Authorization field in an HTTP request would
look like:
Proxy-Authorization: PrivacyToken token=abc...
4. Security Considerations
Note that the KeyID is only a hint to identify the public
verification key. With a sufficiently large number of public keys,
KeyID collisions may occur. By approximation, a KeyID collision
between two distinct keys will occur with probability sqrt(p * 2^33).
In such cases, servers SHOULD attempt verification using both keys.
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5. IANA Considerations
This document registers the "PrivacyToken" authentication scheme in
the "Hypertext Transfer Protocol (HTTP) Authentication Scheme
Registry" established by [RFC7235].
Authentication Scheme Name: PrivacyToken
Pointer to specification text: Section 3 of this document
6. 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>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>.
[RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Authentication", RFC 7235,
DOI 10.17487/RFC7235, June 2014,
<https://www.rfc-editor.org/info/rfc7235>.
[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>.
[RSASIG] Denis, F., Jacobs, F., and C. A. Wood, "RSA Blind
Signatures", Work in Progress, Internet-Draft, draft-irtf-
cfrg-rsa-blind-signatures-02, 2 August 2021,
<https://www.ietf.org/archive/id/draft-irtf-cfrg-rsa-
blind-signatures-02.txt>.
Authors' Addresses
Tommy Pauly
Apple Inc.
One Apple Park Way
Cupertino, California 95014,
United States of America
Email: tpauly@apple.com
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Frederic Jacobs
Apple Inc.
One Apple Park Way
Cupertino, California 95014,
United States of America
Email: frederic.jacobs@apple.com
Christopher A. Wood
Cloudflare
Email: caw@heapingbits.net
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