Internet DRAFT - draft-nottingham-how-did-that-get-into-the-repo
draft-nottingham-how-did-that-get-into-the-repo
Network Working Group M. Nottingham
Internet-Draft 19 October 2020
Intended status: Informational
Expires: 22 April 2021
The secret-token URI Scheme
draft-nottingham-how-did-that-get-into-the-repo-02
Abstract
This document registers the "secret-token" URI scheme, to aid in the
identification of authentication tokens.
Note to Readers
_RFC EDITOR: please remove this section before publication_
The issues list for this draft can be found at
https://github.com/mnot/I-D/labels/how-did-that-get-into-the-repo
(https://github.com/mnot/I-D/labels/how-did-that-get-into-the-repo).
The most recent (often, unpublished) draft is at
https://mnot.github.io/I-D/how-did-that-get-into-the-repo/
(https://mnot.github.io/I-D/how-did-that-get-into-the-repo/).
Recent changes are listed at https://github.com/mnot/I-D/commits/gh-
pages/how-did-that-get-into-the-repo (https://github.com/mnot/I-
D/commits/gh-pages/how-did-that-get-into-the-repo).
See also the draft's current status in the IETF datatracker, at
https://datatracker.ietf.org/doc/draft-nottingham-how-did-that-get-
into-the-repo/ (https://datatracker.ietf.org/doc/draft-nottingham-
how-did-that-get-into-the-repo/).
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-
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. The secret-token URI scheme . . . . . . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Normative References . . . . . . . . . . . . . . . . . . 5
5.2. Informative References . . . . . . . . . . . . . . . . . 5
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
It has become increasingly common to use bearer tokens as an
authentication mechanism in various protocols.
A bearer token is a security token with the property that any party
in possession of the token (a "bearer") can use the token in any way
that any other party in possession of it can. Using a bearer token
does not require a bearer to prove possession of cryptographic key
material (proof-of-possession).
Unfortunately, the number of security incidents involving accidental
disclosure of these tokens has also increased. For example, we now
regularly hear about a developer committing an access token to a
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public source code repository, either because they didn't realise it
was included in the committed code, or because they didn't realise
the implications of its disclosure.
This specification registers the "secret-token" URI scheme to aid
prevention of such accidental disclosures. When tokens are easier to
unambiguously identify, they can trigger warnings in Continuous
Integration systems, or be used in source code repositories
themselves. They can also be scanned for separately.
For example, if cloud.example.net issues access tokens to its clients
for later use, and it does so by formatting them as secret-token
URIs, tokens that "leak" into places that they don't belong are
easier to identify. This could be through a variety of mechanisms;
for example, if repo.example.com can be configured to refuse commits
containing secret-token URIs, it helps its customers avoid accidental
disclosures.
secret-token URIs are intended to aid in identification of generated
secrets like API keys and similar tokens. They are not intended for
use in controlled situations where ephemeral tokens are used, such as
things like Cross-Site Request Forgery (CSRF) tokens.
1.1. Notational Conventions
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 ABNF [RFC5234]. It also uses the pchar rule from
[RFC3986].
2. The secret-token URI scheme
The secret-token URI scheme identifies a token that is intended to be
a secret.
secret-token-URI = secret-token-scheme ":" token
secret-token-scheme = "secret-token"
token = 1*pchar
See [RFC3986], Section 3.3 for a definition of pchar. Disallowed
characters - including non-ASCII characters - MUST be encoded into
UTF-8 [RFC3629] and then percent-encoded ([RFC3986], Section 2.1).
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When a token is both generated and presented for authentication, the
entire URI MUST be used, without changes.
For example, given the URI:
secret-token:E92FB7EB-D882-47A4-A265-A0B6135DC842%20foo
This string (character-for-character, case-sensitive) will both be
issued by the token authority, and required for later access.
Therefore, if the example above were used as a bearer token in
[RFC6750], a client might send:
GET /authenticated/stuff HTTP/1.1
Host: www.example.com
Authorization: Bearer secret-token:E92FB7EB-D882-47A4-A265-A0B6135DC842%20foo
3. IANA Considerations
This document registers the following value in the URI Scheme
registry:
* Scheme name: secret-token
* Status: provisional
* Applications / protocols that use this scheme: none yet
* Contact: iesg@iesg.org
* Change Controller: IESG
* References: (this document)
4. Security Considerations
The token ABNF rule allows tokens as small as one character. This is
not recommended practice; applications should evaluate their
requirements for entropy and issue tokens correspondingly. See
[RFC4086] for more information.
This URI scheme is intended to reduce the incidence of accidental
disclosure; it cannot prevent intentional disclosure.
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If it is difficult to correctly handle secret material, or unclear as
to what the appropriate handling is, users might choose to obfuscate
their secret tokens in order to evade detection (for example,
removing the URI scheme for storage). Mitigating this risk is often
beyond the reach of the system using the secret-token URI, but they
can caution users against such practices, and provide tools to help.
5. References
5.1. 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>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/info/rfc3629>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC5234] 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/info/rfc5234>.
[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>.
5.2. Informative References
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005,
<https://www.rfc-editor.org/info/rfc4086>.
[RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
Framework: Bearer Token Usage", RFC 6750,
DOI 10.17487/RFC6750, October 2012,
<https://www.rfc-editor.org/info/rfc6750>.
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Appendix A. Acknowledgements
The definition of bearer tokens is from [RFC6750].
Author's Address
Mark Nottingham
Prahran VIC
Australia
Email: mnot@mnot.net
URI: https://www.mnot.net/
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