Bulk Report Submission for Distributed Aggregation Protocol (DAP)

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 21 April 2025.¶

Copyright Notice

Copyright (c) 2024 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. 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 Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶

Table of Contents

1. Introduction

The Distributed Aggregation Protocol (DAP) [DAP] accepts reports from many clients and aggregates them in a manner that protects individual contributions. The core protocol requires that each report be submitted to the DAP leader.¶

The assumption implicit in this design is that reports are submitted directly by clients. This is not necessary for security reasons due to the encryption used (this encryption is necessary for the portion of reports that is intended for DAP helpers). Clients could instead pass their reports to an intermediary for forwarding.¶

Use of an intermediary reduces the availability requirements of aggregators and might remove the need for anonymizing proxy to protect client identity from the server (such as the use of Oblivious HTTP [RFC9458] as described in Section 7.4 of [DAP]). It also creates an opportunity to amortize the overheads involved in report submission.¶

This document defines a bulk submissions endpoint for DAP and defines a report submission format for use with that endpoint.¶

2. 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.¶

3. Bulk Submissions Endpoint

DAP defines the {leader}/tasks/{task-id}/reports resource for report submission for a task. This document extends DAP to define the {leader}/tasks/{task-id}/reports/bulk resource for bulk report submission for a task.¶

Clients can send a HTTP POST request to this resource with a payload in the bulk submission format (Section 4). A bulk request is equivalent to multiple separate submissions.¶

A DAP leader MAY accept bulk submissions at the regular "reports" resource.¶

4. Bulk Submission Format

The "application/dap-bulk-report" format contains a header that encodes extensions that are common to all reports. The header is followed by any number of reports, from which those shared fields are removed.¶

struct {
  Extension common_extensions<0..2^16-1>;
  Report report[REPORT_COUNT];
} BulkReport;

The common_extensions field contains common extensions that are added to the set of public report extensions in each report that follows. Reports that include values for any common extension override the value in the common extension.¶

The header is followed by any number of reports, which are encoded exactly as described in [DAP], except as noted in Section 4.1. The use of REPORT_COUNT in Figure 1 is a small abuse of the TLS syntax to signify that any number of reports are included. This "value" could be any positive integer. Unlike a variable-length field, as denoted with < and >, this format does not require that the size of all included reports be known before constructing a request.¶

struct {
  ReportID report_id;
  Time time;
  Extension extensions<0..2^16-1>; /* new */
} ReportMetadata;

opaque PlaintextInputShare<0..2^32-1>;

/* the old format, for reference:
struct {
  Extension extensions<0..2^16-1>;
  opaque payload<0..2^32-1>;
} PlaintextInputShare;
*/

5. Security Considerations

Report metadata, which would include the extensions if the recommendations in Section 4.1 are adopted, are included in the additional associated data for every report. Bulk submission is therefore strictly a performance optimization as far as the operation of DAP is concerned.¶

The potential for a single client to generate large amounts of work for a DAP service is a serious threat to service availability. Any DAP leader SHOULD implement measures to defend against resource exhaustion attacks through this interface. This might include strong authentication of the requester. The logical entity to make this request is a collector, which is likely to be known to the leader.¶

The addition of public extensions exposes more information to the leader. This might be used by a malicious leader to selectively remove reports. A leader is already able to do this without helper awareness, but the added information might allow this to be more selective.¶

6. IANA Considerations

IANA is requested to register at time of publication the "application/dap-bulk-report" media type in the "Media Types" registry at <https://iana.org/assignments/media-types>, following the procedures of [RFC6838]. That registration includes the following:¶

Type name:

application¶

Subtype name:

dap-bulk-report¶

Required parameters:

N/A¶

Optional parameters:

N/A¶

Encoding considerations:

"binary"¶

Security considerations:

See Section 5¶

Interoperability considerations:

N/A¶

Published specification:

this document¶

Applications that use this media type:

This type identifies a bulk report submission for the Distributed Aggregation Protocol.¶

Fragment identifier considerations:

N/A¶

Additional information:

¶

Magic number(s):

N/A¶

Deprecated alias names for this type:

N/A¶

File extension(s):

N/A¶

Macintosh file type code(s):

N/A¶

Person and email address to contact for further information:

See Authors' Addresses section¶

Intended usage:

COMMON¶

Restrictions on usage:

N/A¶

Author:

See Authors' Addresses section¶

Change controller:

IETF¶

7. References

Acknowledgments

TODO acknowledge.¶

Authors' Addresses