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<pre class="pre meta-info">[<a href="https://datatracker.ietf.org/" title="Document search and retrieval page">Search</a>] [<a href="https://www.ietf.org/archive/id/draft-sandowicz-httpbis-httpa2-00.txt" title="Plaintext version of this document">txt</a>|<a href="https://www.ietf.org/archive/id/draft-sandowicz-httpbis-httpa2-00.html" title="HTML version of this document, from XML2RFC">html</a>|<a href="https://www.ietf.org/archive/id/draft-sandowicz-httpbis-httpa2-00.xml" title="XML source for this document">xml</a>|<a href="https://datatracker.ietf.org/doc/pdf/draft-sandowicz-httpbis-httpa2-00">pdfized</a>|<a href="https://datatracker.ietf.org/doc/draft-sandowicz-httpbis-httpa2/00/bibtex/" title="BibTex entry for this document">bibtex</a>] [<a href="https://datatracker.ietf.org/doc/draft-sandowicz-httpbis-httpa2/" title="Datatracker information for this document">Tracker</a>] [<a href="mailto:[email protected]?subject=draft-sandowicz-httpbis-httpa2" title="Send email to the document authors">Email</a>] [<a href="https://author-tools.ietf.org/api/idnits?url=https://www.ietf.org/archive/id/draft-sandowicz-httpbis-httpa2-00.txt" title="Run an idnits check of this document">Nits</a>]
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<div class="draftcontent"><pre>Network Working Group S. Wang
Internet-Draft G. King
Intended status: Informational N. Li
Expires: 8 April 2023 N. Smith
K. Sandowicz
Intel
5 October 2022
<span class="h1">The Hypertext Transfer Protocol Attestable (HTTPA) Version 2</span>
<span class="h1">draft-sandowicz-httpbis-httpa2-00</span>
Abstract
The Hypertext Transfer Protocol Attestable version 2 (HTTPA/2) is an
HTTP extension. It is a transaction-based protocol agnostic to
Transport Layer Security (TLS) in which the Trusted Execution
Environment (TEE) is considered a new type of requested resource over
the Internet. The original Hypertext Transfer Protocol Attestable
(HTTPA) (referred to as HTTPA/1 in the rest of the document) includes
remote attestation (RA) process onto the HTTPS protocol in the
assumption of using Transport Layer Security (TLS) across the
Internet. In contrast, the design of HTTPA/2 could establish a
trusted (attested) and more secure communication without dependence
on TLS.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of <a href="https://datatracker.ietf.org/doc/html/bcp78">BCP 78</a> and <a href="https://datatracker.ietf.org/doc/html/bcp79">BCP 79</a>.
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 <a href="https://datatracker.ietf.org/drafts/current/">https://datatracker.ietf.org/drafts/current/</a>.
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 8 April 2023.
<span class="grey">Wang, et al. Expires 8 April 2023 [Page 1]</span></pre>
<hr class="noprint"><!--NewPage--><pre class="newpage"><span id="page-2"></span>
<span class="grey">Internet-Draft HTTPA/2 October 2022</span>
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to <a href="https://datatracker.ietf.org/doc/html/bcp78">BCP 78</a> and the IETF Trust's Legal
Provisions Relating to IETF Documents (<a href="https://trustee.ietf.org/license-info">https://trustee.ietf.org/</a>
<a href="https://trustee.ietf.org/license-info">license-info</a>) in effect on the date of publication of this document.
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 Revised BSD License text as
described in Section 4.e of the <a href="https://trustee.ietf.org/license-info">Trust Legal Provisions</a> and are
provided without warranty as described in the Revised BSD License.
Table of Contents
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-1">1</a>. Introduction . . . . . . . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-3">3</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-1.1">1.1</a>. Conventions Used in This Document . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-4">4</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-2">2</a>. Protocol Overview and protocol flow . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-6">6</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-2.1">2.1</a>. Untrusted Request (UtR) . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-7">7</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-2.2">2.2</a>. Attest Request (AtR) . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-7">7</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-2.3">2.3</a>. Trusted Request (TrR) . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-8">8</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-2.4">2.4</a>. Protocol flow . . . . . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-8">8</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-3">3</a>. Protocol Transactions . . . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-11">11</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-3.1">3.1</a>. Preflight Check Phase . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-11">11</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-3.2">3.2</a>. Attest Handshake (AtHS) Phase . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-14">14</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-3.3">3.3</a>. Attest Secret Provisioning (AtSP) Phase . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-22">22</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-3.4">3.4</a>. Trusted Phase Communication . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-25">25</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-3.5">3.5</a>. Changes in Mutual HTTPA/2(mHTTPA) . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-28">28</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-4">4</a>. Security Considerations . . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-28">28</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-4.1">4.1</a>. Layer 7 End-to-End Protection . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-28">28</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-4.2">4.2</a>. Replay Protection . . . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-29">29</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-4.3">4.3</a>. Downgrade Protection . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-29">29</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-4.4">4.4</a>. Privacy Considerations . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-29">29</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-4.5">4.5</a>. Roots of Trust (RoT) . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-30">30</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-5">5</a>. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-30">30</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-6">6</a>. IANA Considerations . . . . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-30">30</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-7">7</a>. References . . . . . . . . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-31">31</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-7.1">7.1</a>. Normative References . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-31">31</a>
<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-7.2">7.2</a>. Informative References . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-31">31</a>
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . <a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#page-33">33</a>
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<span class="h2"><a class="selflink" id="section-1" href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-1">1</a>. Introduction</span>
The HTTPA/1 [<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#ref-I-D-11" title=""HTTPA: HTTPS Attestable Protocol"">I-D-11</a>] defines an HTTP extension to handle requests for
remote attestation, secret provisioning, and private data
transmission, so internet visitors can access a wide variety of
services running in Trusted Execution Environments (TEEs) to handle
their requests with strong assurances.
The HTTPA/1 supports mutual attestation if both client and service
endpoints run inside the TEE. Although HTTPA/1 helps build trust
between L7 endpoints with data-level protection, HTTPA/1 needs TLS to
defend against some specific attacks over the Internet, e.g., replay
attacks and downgrade attacks, these attacks are not vulnerable in
HTTP/2 due to specific improvements for them. Note that TLS cannot
guarantee end-to-end security for the HTTPS message exchange [<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#ref-I-D-1" title=""HTTP Message Signatures draft-ietfhttpbis-message-signatures-08"">I-D-1</a>]
when the TEE-based services (TServices) are hosted behind a TLS
termination gateway or inspection appliance (a.k.a. middle boxes).
Although the TLS can provide Confidentiality, Integrity, and
Authenticity (ConfIntAuth) to help ensure the security of message
exchange for HTTPA/1 protocol, it is not a complete end-to-end
solution for web services at L7. Both HTTPA/1 and TLS need to
generate key material through key exchange and derivation processes.
This requires additional round trips at L5 and increases network
latency. Thus, there is room to optimize the network performance
further and reduce the communication complexity by avoiding the
repetition of key negotiation. Due to the limitation of TLS
mentioned above, a version of HTTPA with message-level security
protection is a natural candidate to address the issues mentioned
above. This document proposes an upgrade protocol, HTTPA/2, which
makes it possible to secure HTTPA transactions without dependence on
TLS. The HTTPA/2 is designed to improve the processes of key
exchange, RA, and secret provisioning. It also enables end-to-end
secure and trustworthy request/response transactions at L7, which is
cryptographically bound to an attestable service base that can be
trusted by internet visitors regardless of the presence of untrusted
TLS termination.
The protocol described in this document focuses on extending the
functionality provided by the HTTPA/1 protocol message formats. This
document alone is sufficient to understand the protocol, and the
HTTPA/1 [<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#ref-I-D-11" title=""HTTPA: HTTPS Attestable Protocol"">I-D-11</a>] could be used as supplemental material.
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<span class="h3"><a class="selflink" id="section-1.1" href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-1.1">1.1</a>. Conventions Used in This Document</span>
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 [BCP 14], [<a href="https://datatracker.ietf.org/doc/html/rfc2119">RFC 2119</a>],
[KEYWORDS].
In addition to those listed above, this document uses the following
terms:
Trusted Execution Environment (TEE):
TEE is an environment where genuine codes are executed on data with
isolation and memory encryption inaccessible to anyone.
Rich Execution Environment (REE):
In contrast to TEE, codes are executed on data without isolation.
Client:
The endpoint initiating the HTTPA connection.
Server:
The endpoint did not initiate the HTTPA connection. In HTTPA/2, it
refers to TEE-based Service (TService) running inside an enclave.
Client-side verifier(c-verifier):
Verifier from the client side.
Server-side verifier(s-verifier):
Verifier from the server side.
Attestation:
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Attestation is the process of demonstrating that a software
executable has been properly instantiated on a platform, thus
establishing a level of confidence in the trustworthiness of a remote
peer.
Attest Quote(AtQ):
AtQ is an opaque data structure signed by a Quoting Service
(QService) with an attestation key (AK). It can be called a quote or
attestation evidence, which is used to establish trustworthiness
through identities.
Attest Base(AtB):
AtB is the totality of computing resources serving client request
handling, including hardware, firmware, software, and access controls
to work together to deliver trustworthy service quality with enforced
security/privacy policy.
Attest header line(AHL)
It refers to the different types of header lines used during the
handshake phase, including Attest Ticket, Attest Binder, etc.
Attest header Field(AHF)
Regarding the HTTP method, we propose a new HTTP method, called
"ATTEST," to perform the transactions of AtHS and AtSP. The HTTP
request using ATTEST method is called AtR. Regarding HTTP header
fields, we propose to augment them with additional ones called Attest
Header Fields (AHFs) prefixed with the string "Attest-." Without
AHFs, it must be a UtR in terms of HTTPA/2.
Attest Ticket(AtT):
AtT is a type of attest header line(AHL) used to ensure the integrity
and authenticity (IntAuth) of AHLs and freshness are protected
cryptographically, except for the AtR of AtHS, the initiating request
for the handshake.
Attest Binder (AtBr):
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AtBr is a type of AHL used to ensure the binding between the HTTPA/2
request and the corresponding response.
Attest Request (AtR)
Regarding the HTTP method, we propose a new HTTP method, called
"ATTEST," to perform the transactions of Attest Handshake(AtHS) and
Attest Secret Provisioning (AtSP). The HTTP request using ATTEST
method is called AtR.
Trusted Computing Base(TCB):
The minimal totality of hardware, software, or firmware must be
trusted for security requirements.
Trusted Cargo(TrC):
TrC is a vehicle to carry confidential information which needs to be
protected by authenticated encryption. It can appear in both HTTPA/2
request and response messages, except for the AtR of AtHS.
Trusted Transport Layer Security(TrTLS):
If users want to protect the entire HTTP message?every bit of the
message, HTTPA/2 can leverage TLSto establish a secure connection at
L5 between the client and its adjacent middle box, which we call
TrTLS.
Preflight
This is the first phase of the HTTPA/2 transactions, and it is a
lightweight HTTP OPTIONS request.
<span class="h2"><a class="selflink" id="section-2" href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-2">2</a>. Protocol Overview and protocol flow</span>
There are three types of requests defined by the HTTPA/2 protocol,
including Un-trusted Request (UtR), Attest Request (AtR), and Trusted
Request (TrR). UtR is used in HTTP(S) transactions; AtR is used in
both transactions of Attest Handshake (AtHS) and Attest Secret
Provisioning (AtSP); TrR is used in the trusted transaction. For
convenience, we refer to the AtR and TrR as "HTTPA/2 request".
Regarding the HTTP method, we propose a new HTTP method, called
"ATTEST," to perform the transactions of AtHS and AtSP. The HTTP
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request using ATTEST method is called AtR. Regarding HTTP header
fields, we propose to augment them with additional ones called Attest
Header Fields (AHFs) prefixed with the string "Attest-." Without
AHFs, it must be a UtR in terms of HTTPA/2.
The AHFs are dedicated to HTTPA traffic. For example, they can be
used to authenticate the identity of HTTPA/2 transactions source,
indicate which AtB to request, convey confidential metadata,
provision secrets, present ticket, etc.
The last one is AHL, and it consists of AHF and its values in a
standard form [<a href="https://datatracker.ietf.org/doc/html/rfc8941" title=""Structured Field Values for HTTP"">RFC8941</a>]. We use it to signify a single piece of
annotated data associated with the current HTTPA/2 request.
<span class="h3"><a class="selflink" id="section-2.1" href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-2.1">2.1</a>. Untrusted Request (UtR)</span>
An untrusted request is for any transactions that are not sensitive.
The UtR is simply an ordinary type of HTTP request, which does not
use the ATTEST method nor contains any AHLs.
Before a UtR reaches a TService, the UtR can be easily eavesdropped
on or tampered with along the communication path. Even protected by
TLS, it can still be attacked when crossing any application gateway
or L7 firewall since those intervening middle-boxes are untrusted and
will terminate TLS connections hop by hop [<a href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#ref-I-D-1" title=""HTTP Message Signatures draft-ietfhttpbis-message-signatures-08"">I-D-1</a>]. Therefore, there
is no guarantee of ConfIntAuth. That's why the TService cannot treat
the request as trustworthy, but it is still possible for TService to
handle UtR if allowed by the service-side policy. Thus, we don't
suggest TService to handle any one of them for the sake of security.
<span class="h3"><a class="selflink" id="section-2.2" href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-2.2">2.2</a>. Attest Request (AtR)</span>
The AtR is a HTTP request equipped with both ATTEST method and AHLs
for AtHS and AtSP. If the corresponding TService did not accept any
AtR, subsequent TrR will no longer be valid to this TService. The
major difference between an AtR used in AtHS and AtSP respectively is
as follows:
1)
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The AtR used in AtHS is designed to request all necessary resources
for handling both types of AtR used in AtSP and AtHS. For example,
one of the most critical resources is AtB, which may be scheduled or
allocated by a server-side resource arbiter. Typically (but not
always), an upfront TService can directly designate itself as the AtB
for this client.
2)
The AtR of AtSP is optional in HTTPA/2 traffic flow since, in some
cases, the TService does not need any AtB-wide secrets provided by
the client to work. In the typical case, TService needs secret
provisioning to configure its working environment, such as connecting
to databases, setup signing keys and certificates, etc. This AtR
must be issued after all TEE resources have been allocated through
the AtHS transaction described above. It's worth noting that this
request is not required to be issued before any TrR.
<span class="h3"><a class="selflink" id="section-2.3" href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-2.3">2.3</a>. Trusted Request (TrR)</span>
The TrR can be issued right after a successful AtHS where an AtB is
allocated. Although TrR does not use ATTEST method, it should
contain AHLs to indicate that it is a TrR, not a UtR. In other
words, the TrR is nothing but an ordinary HTTP request with some
AHLs. Within those AHLs, one of them must be AtB ID to determine
which AtB is targeted in addition to the specified URI. The TrR can
be dispatched to the proper TService to handle this request.
<span class="h3"><a class="selflink" id="section-2.4" href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-2.4">2.4</a>. Protocol flow</span>
As shown in Figure 1, we illustrate those transactions from a client
perspective, including preflight, AtHS, AtSP, and trusted requests in
a workflow diagram. A detailed explanation of each phase is in the
following chapters. In the design of HTTPA/2, only the phase of AtHS
is required. This largely simplifies the interaction between the
client and the TService and improves the overall service experience
for both security and remote attestation.
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+-----+ +-------------+ no
|START|->|go preflight?|--------------+
+-----+ +-------------+ |
| yes |
v |
+---------+ |
|Preflight| |
+---------+ |
| |
v |
+--------+ no +----+ |
|allowed?|----->|STOP| |
+--------+ +----+ |
yes | |
+---------------------+
|
v
+---------+ yes
|attested?|----------------+
+---------+ |
| no |
v |
+----------------+ |
|Attest Handshake| |
+----------------+ |
| |
+---------------------+
| |
v |
+----+ invalid +------------+ |
|STOP|---------->|Attest base?| |
+----+ +------------+ |
| valid |
v |
+-------------------------+--------------+ |
| | | |
v v v |
+--------------+ +-----------+ +-----------+ |
|need base-wide| no | Trusted | | Untrusted | |
| secrets? |--------+ |Transaction| |Transaction| |
+--------------+ | +-----------+ +-----------+ |
| | | | |
v | | | |
+-------------------+ | | | |
|Secret Provisioning| | | | |
+-------------------+ | | | |
| | | | |
v | | | |
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+---------+ no +----+ | | | |
|accepted?|--->|STOP| | | | |
+---------+ +----+ | | | |
| yes | | | |
v v v v |
+-----------------+--------+--------------+ |
| |
v |
+----+ yes +-----------+ no |
|STOP|<--------|terminated?|-----------------------------+
+----+ +-----------+
Figure 1: HTTPA transaction workflow from the client view
The Figure 2 shows the workflow, which can help understand how those
transactions are distinguished in TService.
+-----+
|START|
+--+--+
|
v
+---------------------------+
| |
v |
yes +------+--------+ no |
+---------+ATTEST request?+--------------+ |
| +---------------+ | |
v | |
contained +-----+-+ not contained | |
+----------+base id+------------+ | |
| +-------+ | | |
v v | |
+-------+-----------+ +--------+-------+ | |
|Secret Provisioning| |Attest Handshake| | |
+------+------------+ +---------+------+ | |
| | | |
v v | |
+-----+---+ invalid +----+ +---+-+ fail +----+ | |
|base-wide+---------->+STOP| |base?+------->+STOP| | |
|secrets? | +----+ +--+--+ +----+ | |
+-----+---+ | | |
| valid | allocated | |
v v | |
++-------------------------------+ | |
| | |
| +----------------------------+ |
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| | |
| v |
| contained +---+---+ not contained |
| +---------------+base id+-------------+ |
| | +-------+ | |
| v v |
| +-----+-------------+ yes +---+----+ no |
| |Trusted Transaction| +-----+OPTIONS +----+ |
| +-----+-------------+ | |request?| | |
| | | +--------+ | |
| v v v |
| +-----+-----+ yes +----+ +----+----+ +-------+---+ |
| |terminated?+------>+STOP| |Preflight| | Untrusted | |
| +-----+-----+ +----+ +-----+---+ |Transaction| |
| | | +---------+-+ |
| | v | |
| | no +----+---+ no +----+ | |
| | |allowed?+----->+STOP| | |
| | +----+---+ +----+ | |
| | | yes | |
| | v v |
| | +------------+-------+ |
| | | |
| v v |
| +----------------------------------------+ |
| | |
v v |
+-------------------+---------+ |
| |
v |
+----+ yes +-----+-----+ no |
|STOP+<--------+terminated?+-----------------------------------+
+----+ +-----------+
Figure 2: HTTPA transaction workflow from the TService view
<span class="h2"><a class="selflink" id="section-3" href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-3">3</a>. Protocol Transactions</span>
<span class="h3"><a class="selflink" id="section-3.1" href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-3.1">3.1</a>. Preflight Check Phase</span>
The preflight request uses OPTIONS request to give the web service a
chance to see what the actual AtR looks like before it is made, so
the service can decide whether it is acceptable. In addition, the
client endpoint performs the preflight check as a security measure to
ensure that the visited service can understand the ATTEST method,
AHFs, and its implied security assurance.
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To start HTTPA/2, a preflight request could be issued by a client as
optional to check whether the Web service, specified by URI in the
request line is TEE-aware and prepared for AtHS. If the client is a
web browser, the preflight request can be automatically issued when
the AtR qualifies as "to be preflighted." We need the preflight
transaction because it is a lightweight HTTP OPTIONS [<a href="https://datatracker.ietf.org/doc/html/rfc7231" title=""Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content"">RFC7231</a>]
request, which will not consume a lot of computing resources to
handle compared to the AtR. Caching the preflight result can prevent
re-checking during a specified time window. In the case of out-of-
sync, the TService will result in an invalid signal for HTTPA trusted
requests.
Passing this check does not guarantee that this service can
successfully handle the AtR. For example, the TService may run out
of resources, or the client's cipher suites are not supported, and so
on.
The client can also use the preflight to detect the capabilities of
AtB, without implying any actual actions.
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Client-side Web Client Web TService Server-side
Verifier (HW-TEE,Attester) (HW-TEE,Attester) Verifier
| | | |
| |checkAttestMethod| |
| |---------------->| Optional request: |
| | | Access-Control-Request-Method |
| | | ATTEST |
| | | Access-Control-Request-Headers|
| | | ATTEST-Base-id, |
| | | ATTEST-Ticket, |
| | | ATTEST-Signature.. |
| | |------------------------------>|
| +===================PASS===============================+
| | | | HTTP 200 OK | |
| | | | Allow: ATTEST | |
| | | | Access-Control-Allow-Headers: | |
| | | | ATTEST-Base-id, | |
| | | | ATTEST-Ticket, | |
| | | | ATTEST-Signature... | |
| | | |<------------------------------| |
| | | HTTP 200 OK | | |
| | |<----------------| | |
| +======================================================+
| | | |
| +=================FAILURE==============================+
| | | | | |
| | | HTTP 405 METHOD_NOT_ALLOWED | |
| | |<----------------| | |
| | | | | |
| | | showErros | | |
| | |-------+ | | |
| | | | | | |
| | |<------+ | | |
| +======================================================+
| | | |
Figure 3: Message Flow example for Preflight transaction
As shown in Figure 3, an OPTIONS request should be honored by an
HTTPA/2 compliant TService. The preflight transaction has standard
HFs to specify the method and AHLs which will be sent out later to
the same TService
if they are acceptable. Those HFs are described respectively as
follows:
1. HFs in the request message
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(a) Access-Control-Request-Method
This HF carries a list of methods indicating that ATTEST method will
be used in the next request if the service can support it.
(b) Access-Control-Request-Headers
This HF carries a list of field names indicating that the AHFs will
be included in the next request if the service can support them.
2. HFs in the response message
(a) Allow
This HF carries a list of supported methods by the visiting service.
It must contain the ATTEST method for the client to proceed with AtR;
otherwise, the AtR is not acceptable by this service and will be
denied if received it.
(b) Access-Control-Allow-Headers
This HF carries a list of allowed AHFs. The client needs to check
that all of the requested AHFs should be contained in this resulting
field.
(c) Access-Control-Max-Age
This HF indicates how long the preflight check results can be cached.
<span class="h3"><a class="selflink" id="section-3.2" href="https://datatracker.ietf.org/doc/html/draft-sandowicz-httpbis-httpa2#section-3.2">3.2</a>. Attest Handshake (AtHS) Phase</span>
The AtHS phase contains a core transaction of HTTPA/2. In a single
round trip time (one RTT), the AtR and its response accomplish three
major tasks, including key exchange, AtB allocation, and AtQ
exchange, as shown in Figure 4.
Client-side Web Client Web TService Server-side
Verifier (HW-TEE,Attester) (HW-TEE,Attester) Verifier
| | | |
| | | |
| | genExchangeKeys | +==========ATEST request=========+
| |----+ | |Attest-Version: [versions] |
| | | | |Attest-Date: [GMT] |
| |<---+ | |Attest-Signatures: sigs=[base64]|
| | | |Attest-Policies: [sec policies] |
| +=====OPTIONAL==========+ | |Attest-Base-Creation:[method] |
<span class="grey">Wang, et al. Expires 8 April 2023 [Page 14]</span></pre>
<hr class="noprint"><!--NewPage--><pre class="newpage"><span id="page-15"></span>
<span class="grey">Internet-Draft HTTPA/2 October 2022</span>
| | | genQuotes | | |Attest-Transport: [base64] |
| | |----+ | | |Attest-Random: [base64] |
| | | | | | |Attest-Quotes:quotes=[base64] |
| | |<---+ | | | max-age=[expireTime]|
| +=======================+ | |Attest-Cipher-Suites:[ciphrName]|
| | | |Attest-Supported-Groups[grNames]|
| | | |Attest-Key-Shares: [shared keys]|
| | sendAttestRequest | |Attest-Blocklist:identifie=[ids]|
| |------------------>| +================================+
| | | |
| | +======IF ATTESTING MUTUALLY==========+
| | | | sendQuote | |
| | | |------------------------------>| |
| | | | | |
| | | | getVerifyResult | |
| | | |<------------------------------| |
| | +=====================================+
| | |-------+ |
| | | | allocAttestBase |
| | |<------+ |
| | |-------+ |
| | | | genExchangeKeys |
| | |<------+ |
| | |-------+ |
| | | | genQuotes |
| | |<------+ |
| | |-------+ |
| | | | deriveKeys |
| | getAttestResponse |<------+ |
| sendQuote |<------------------| +=========HTTP 200 OK============+
|<----------| | |Attest-Version: [selected ver] |
| getVerif | | |Attest-Base-Id:[base64] |
| Result | | | max-age=[expireTime]|
|---------->| | |Attest-Transport: [base64] |
| +=====status is not 200=====+ | |Attest-Random: [base64] |
| |=======or unverified=======| | |Attest-Expires: [GMT] |
| | |----+ | | |Attest-Quotes:quotes=[base64] |
| | | | showErrors | | | max-age=[expireTime]|
| | |<---+ | | |Attest-Cipher-Suite:[ciphrNames]|
| +===========================+ | |Attest-Supported-Group:[grNames]|
| | | |Attest-Key-Share: [shared key] |
| |-------+ | |Attest-Secrets:[secrets="base64"|
| | |deriveKeys | | max-age=[expireTime]|
| |<------+ | |Attest-Cargo: [base64] |
| | | +================================+