HTTP Transport Authentication
draft-schinazi-httpbis-transport-auth-06
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
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|---|---|---|---|
| Authors | David Schinazi , David Oliver | ||
| Last updated | 2022-07-11 | ||
| Replaced by | draft-schinazi-httpbis-unprompted-auth | ||
| RFC stream | (None) | ||
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| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
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draft-schinazi-httpbis-transport-auth-06
HTTPBIS D. Schinazi
Internet-Draft Google LLC
Intended status: Experimental D. Oliver
Expires: 12 January 2023 Guardian Project
11 July 2022
HTTP Transport Authentication
draft-schinazi-httpbis-transport-auth-06
Abstract
Existing HTTP authentication mechanisms are probeable in the sense
that it is possible for an unauthenticated client to probe whether an
origin serves resources that require authentication. It is possible
for an origin to hide the fact that it requires authentication by not
generating Unauthorized status codes, however that only works with
non-cryptographic authentication schemes: cryptographic schemes (such
as signatures or message authentication codes) require a fresh nonce
to be signed, and there is no existing way for the origin to share
such a nonce without exposing the fact that it serves resources that
require authentication. This document proposes a new non-probeable
cryptographic authentication scheme.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at
https://DavidSchinazi.github.io/draft-schinazi-httpbis-transport-
auth/draft-schinazi-httpbis-transport-auth.html. Status information
for this document may be found at https://datatracker.ietf.org/doc/
draft-schinazi-httpbis-transport-auth/.
Discussion of this document takes place on the HTTP Working Group
mailing list (mailto:ietf-http-wg@w3.org), which is archived at
https://lists.w3.org/Archives/Public/ietf-http-wg/.
Source for this draft and an issue tracker can be found at
https://github.com/DavidSchinazi/draft-schinazi-httpbis-transport-
auth.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions and Definitions . . . . . . . . . . . . . . . 3
2. Computing the Authentication Proof . . . . . . . . . . . . . 3
3. Header Field Definition . . . . . . . . . . . . . . . . . . . 4
3.1. The u Directive . . . . . . . . . . . . . . . . . . . . . 4
3.2. The p Directive . . . . . . . . . . . . . . . . . . . . . 4
3.3. The a Directive . . . . . . . . . . . . . . . . . . . . . 4
4. Transport Authentication Schemes . . . . . . . . . . . . . . 4
4.1. Signature . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. HMAC . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Intermediary Considerations . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7.1. Transport-Authentication Header Field . . . . . . . . . . 6
7.2. Transport Authentication Schemes Registry . . . . . . . . 6
7.3. TLS Keying Material Exporter Labels . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 8
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Existing HTTP authentication mechanisms are probeable in the sense
that it is possible for an unauthenticated client to probe whether an
origin serves resources that require authentication. It is possible
for an origin to hide the fact that it requires authentication by not
generating Unauthorized status codes, however that only works with
non-cryptographic authentication schemes: cryptographic schemes (such
as signatures or message authentication codes) require a fresh nonce
to be signed, and there is no existing way for the origin to share
such a nonce without exposing the fact that it serves resources that
require authentication. This document proposes a new non-probeable
cryptographic authentication scheme.
There are scenarios where servers may want to expose the fact that
authentication is required for access to specific resources. This is
left for future work.
1.1. Conventions and Definitions
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.
This document uses the Augmented BNF defined in [ABNF] and updated by
[ABNF2] along with the "#rule" extension defined in Section 5.6.1 of
[HTTP]. The rules below are defined in [HTTP] and [OID].
OWS = <OWS, see {{Section 5.6.3 of HTTP}}>
quoted-string = <quoted-string, see {{Section 5.6.4 of HTTP}}>
token = <token, see {{Section 5.6.2 of HTTP}}>
token68 = <token68, see {{Section 5.6.3 of HTTP}}>
oid = <oid, see {{Section 2 of OID}}>
2. Computing the Authentication Proof
This document only defines Transport Authentication for uses of HTTP
with TLS. This includes any use of HTTP over TLS as typically used
for HTTP/2, or HTTP/3 where the transport protocol uses TLS as its
authentication and key exchange mechanism [QUIC-TLS].
The user agent leverages a TLS keying material exporter [KEY-EXPORT]
to generate a nonce which can be signed using the user-id's key. The
keying material exporter uses a label that starts with the characters
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"EXPORTER-HTTP-Transport-Authentication-" (see Section 4 for the
labels and contexts used by each scheme). The TLS keying material
exporter is used to generate a 32-byte key which is then used as a
nonce.
3. Header Field Definition
The "Transport-Authentication" header allows a user agent to
authenticate its transport connection with an origin server.
Transport-Authentication = tpauth-scheme *( OWS ";" OWS param )
tpauth-scheme = token
param = token "=" ( token / quoted-string )
3.1. The u Directive
The OPTIONAL "u" (user-id) directive specifies the user-id that the
user agent wishes to authenticate. It is encoded using Base64
(Section 4 of [BASE64]).
u = token68
3.2. The p Directive
The OPTIONAL "p" (proof) directive specifies the proof that the user
agent provides to attest to possessing the credential that matches
its user-id. It is encoded using Base64 (Section 4 of [BASE64]).
p = token68
3.3. The a Directive
The OPTIONAL "a" (algorithm) directive specifies the algorithm used
to compute the proof transmitted in the "p" directive.
a = oid
4. Transport Authentication Schemes
The Transport Authentication Framework allows defining Transport
Authentication Schemes, which specify how to authenticate user-ids.
This documents defined the "Signature" and "HMAC" schemes.
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4.1. Signature
The "Signature" Transport Authentication Scheme uses asymmetric
cyptography. User agents possess a user-id and a public/private key
pair, and origin servers maintain a mapping of authorized user-ids to
their associated public keys. When using this scheme, the "u", "p",
and "a" directives are REQUIRED. The TLS keying material export
label for this scheme is "EXPORTER-HTTP-Transport-Authentication-
Signature" and the associated context is empty. The nonce is then
signed using the selected asymmetric signature algorithm and
transmitted as the proof directive.
For example, the user-id "john.doe" authenticating using Ed25519
[ED25519] could produce the following header (lines are folded to
fit):
Transport-Authentication: Signature u="am9obi5kb2U=";
a=1.3.101.112;
p="SW5zZXJ0IHNpZ25hdHVyZSBvZiBub25jZSBoZXJlIHdo
aWNoIHRha2VzIDUxMiBiaXRzIGZvciBFZDI1NTE5IQ=="
4.2. HMAC
The "HMAC" Transport Authentication Scheme uses symmetric
cyptography. User agents possess a user-id and a secret key, and
origin servers maintain a mapping of authorized user-ids to their
associated secret key. When using this scheme, the "u", "p", and "a"
directives are REQUIRED. The TLS keying material export label for
this scheme is "EXPORTER-HTTP-Transport-Authentication-HMAC" and the
associated context is empty. The nonce is then HMACed using the
selected HMAC algorithm and transmitted as the proof directive.
For example, the user-id "john.doe" authenticating using HMAC-SHA-512
[SHA] could produce the following header (lines are folded to fit):
Transport-Authentication: HMAC u="am9obi5kb2U=";
a=2.16.840.1.101.3.4.2.3;
p="SW5zZXJ0IEhNQUMgb2Ygbm9uY2UgaGVyZSB3aGljaCB0YWtl
cyA1MTIgYml0cyBmb3IgU0hBLTUxMiEhISEhIQ=="
5. Intermediary Considerations
Since Transport Authentication authenticates the underlying transport
by leveraging TLS keying material exporters, it cannot be
transparently forwarded by HTTP intermediaries. HTTP intermediaries
that support this specification will validate the authentication
received from the client themselves, then inform the upstream HTTP
server of the presence of valid authentication using some other
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mechanism.
6. Security Considerations
Transport Authentication allows a user-agent to authenticate to an
origin server while guaranteeing freshness and without the need for
the server to transmit a nonce to the user agent. This allows the
server to accept authenticated clients without revealing that it
supports or expects authentication for some resources. It also
allows authentication without the user agent leaking the presence of
authentication to observers due to clear-text TLS Client Hello
extensions.
7. IANA Considerations
7.1. Transport-Authentication Header Field
This document will request IANA to register the following entry in
the "HTTP Field Name" registry maintained at
<https://www.iana.org/assignments/http-fields>:
Field Name: Transport-Authentication
Template: None
Status: provisional (permanent if this document is approved)
Reference: This document
Comments: None
7.2. Transport Authentication Schemes Registry
This document, if approved, requests IANA to create a new "HTTP
Transport Authentication Schemes" Registry. This new registry
contains strings and is covered by the First Come First Served policy
from Section 4.4 of [IANA-POLICY]. Each entry contains an optional
"Reference" field.
It initially contains the following entries:
* Signature
* HMAC
The reference for both is this document.
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7.3. TLS Keying Material Exporter Labels
This document, if approved, requests IANA to register the following
entries in the "TLS Exporter Labels" registry maintained at
https://www.iana.org/assignments/tls-parameters/tls-
parameters.xhtml#exporter-labels (https://www.iana.org/assignments/
tls-parameters/tls-parameters.xhtml#exporter-labels)
* EXPORTER-HTTP-Transport-Authentication-Signature
* EXPORTER-HTTP-Transport-Authentication-HMAC
Both of these entries are listed with the following qualifiers:
DTLS-OK: N
Recommended: Y
Reference: This document
8. References
8.1. Normative References
[ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/rfc/rfc5234>.
[ABNF2] Kyzivat, P., "Case-Sensitive String Support in ABNF",
RFC 7405, DOI 10.17487/RFC7405, December 2014,
<https://www.rfc-editor.org/rfc/rfc7405>.
[BASE64] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/rfc/rfc4648>.
[HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/rfc/rfc9110>.
[IANA-POLICY]
Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/rfc/rfc8126>.
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[KEY-EXPORT]
Rescorla, E., "Keying Material Exporters for Transport
Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705,
March 2010, <https://www.rfc-editor.org/rfc/rfc5705>.
[OID] Mealling, M., "A URN Namespace of Object Identifiers",
RFC 3061, DOI 10.17487/RFC3061, February 2001,
<https://www.rfc-editor.org/rfc/rfc3061>.
[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/rfc/rfc2119>.
[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/rfc/rfc8174>.
8.2. Informative References
[ED25519] Josefsson, S. and J. Schaad, "Algorithm Identifiers for
Ed25519, Ed448, X25519, and X448 for Use in the Internet
X.509 Public Key Infrastructure", RFC 8410,
DOI 10.17487/RFC8410, August 2018,
<https://www.rfc-editor.org/rfc/rfc8410>.
[QUIC-TLS] Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure
QUIC", RFC 9001, DOI 10.17487/RFC9001, May 2021,
<https://www.rfc-editor.org/rfc/rfc9001>.
[SHA] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011,
<https://www.rfc-editor.org/rfc/rfc6234>.
Acknowledgments
The authors would like to thank many members of the IETF community,
as this document is the fruit of many hallway conversations. Using
the OID for the signature and HMAC algorithms was inspired by
Signature Authentication in IKEv2.
Authors' Addresses
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David Schinazi
Google LLC
1600 Amphitheatre Parkway
Mountain View, CA 94043
United States of America
Email: dschinazi.ietf@gmail.com
David M. Oliver
Guardian Project
Email: david@guardianproject.info
URI: https://guardianproject.info
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