[Ohai] WG Action: Formed Oblivious HTTP Application Intermediation (ohai)

[The IESG <[e-mail]>]

A new IETF WG has been formed in the Security Area. The initial 
chartering process was started under the name OHTTP, and subsequently 
the OHTTP BOF was held at IETF 111. The external review was under the 
name OARH. For additional information, please contact the Area Directors 
or the WG Chairs.

Oblivious HTTP Application Intermediation (ohai)
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Current status: Proposed WG

Chairs:
  Richard Barnes <[e-mail]>
  Shivan Sahib <[e-mail]>

Assigned Area Director:
  Francesca Palombini <[e-mail]>

Security Area Directors:
  Benjamin Kaduk <[e-mail]>
  Roman Danyliw <[e-mail]>

Mailing list:
  Address: [e-mail]
  To subscribe: https://www.ietf.org/mailman/listinfo/ohai
  Archive: https://mailarchive.ietf.org/arch/browse/ohai/

Group page: https://datatracker.ietf.org/group/ohai/

Charter: https://datatracker.ietf.org/doc/charter-ietf-ohai/

In a number of different settings, interactions between clients and servers
involve information that could be sensitive when associated with client
identity.  Client-server applications built on HTTP reveal aspects of client
identity to servers through these interactions, especially source addresses.
Even without client identity, a server might be able to build a profile of
client activity by correlating requests from the same client over time.

In HTTP-based applications where the information included in requests does not
need to be correlated, the protocol this working group defines will allow a
supporting server to accept requests via a proxy.  The proxy ensures that the
server cannot see source addressing information for clients, which prevents
servers linking multiple requests from the same client.  Encryption ensures
that the proxy is unable to read requests or responses.  However, if the
proxy and server collude, then neither of these privacy properties hold.

Applications and use cases best suited for this protocol are those that have
discrete, transactional queries that might reveal small amounts of information
that accumulate over time.  Examples include DNS queries, telemetry
submission, and certificate revocation checking. In some of these application
deployments, the relationship between client, server, and cooperating proxy
might be configured out-of-band.

General purpose HTTP applications such as web browsing are not in scope for
the protocol that is to be defined. Broad applicability is limited by
multiple factors, including the need for explicit server support of the
protocol. In contrast, transport-level proxies such as HTTP CONNECT or MASQUE
are a more appropriate mechanism for those use cases, as they allow
connecting to unmodified servers.

The OHAI working group will define a protocol for anonymization of HTTP
requests using a partly-trusted intermediary, a method of encapsulating HTTP
requests and responses that provides protected, low-latency exchanges.  This
protocol will use existing cryptographic primitives to meet these goals.  The
working group will define any data formats necessary to carry encapsulated
requests and responses, plus formats for supplementary material, such as
server keying material, that might be needed to use the protocol.

The OHAI working group will include an applicability statement that documents
the limitations of this design and any usage constraints that are necessary to
ensure that the protocol is secure.  The working group will consider the
operational impact as part of the protocol design and document operational
considerations.

The working group will prioritize work on the core protocol elements as
identified.  In addition, the working group may work on other use cases and
deployment models, including those that involve discovery of proxies or
servers and their key configurations.

The OHAI working group will work closely with other groups that develop the
tools that the protocol depends on (HTTPbis for HTTP, CFRG for HPKE) or that
might use the protocol (DPRIVE and ADD for DNS over HTTPS).

The working group will use draft-thomson-http-oblivious as input.

Milestones:

  Jul 2022 - Submit the protocol draft to the IESG for publication