draft-ietf-httpbis-digest-headers-02.txt   draft-ietf-httpbis-digest-headers-03.txt 
HTTP R. Polli HTTP R. Polli
Internet-Draft Team Digitale, Italian Government Internet-Draft Team Digitale, Italian Government
Intended status: Standards Track L. Pardue Intended status: Standards Track L. Pardue
Expires: September 10, 2020 Cloudflare Expires: March 11, 2021 Cloudflare
March 09, 2020 September 07, 2020
Digest Headers Digest Headers
draft-ietf-httpbis-digest-headers-02 draft-ietf-httpbis-digest-headers-03
Abstract Abstract
This document defines the Digest and Want-Digest header fields for This document defines the HTTP Digest and Want-Digest fields, thus
HTTP, thus allowing client and server to negotiate an integrity allowing client and server to negotiate an integrity checksum of the
checksum of the exchanged resource representation data. exchanged resource representation data.
This document obsoletes RFC 3230. It replaces the term "instance" This document obsoletes RFC 3230. It replaces the term "instance"
with "representation", which makes it consistent with the HTTP with "representation", which makes it consistent with the HTTP
Semantic and Context defined in RFC 7231. Semantic and Context defined in draft-ietf-httpbis-semantics.
Note to Readers Note to Readers
_RFC EDITOR: please remove this section before publication_ _RFC EDITOR: please remove this section before publication_
Discussion of this draft takes place on the HTTP working group Discussion of this draft takes place on the HTTP working group
mailing list (ietf-http-wg@w3.org), which is archived at mailing list (ietf-http-wg@w3.org), which is archived at
https://lists.w3.org/Archives/Public/ietf-http-wg/ [1]. https://lists.w3.org/Archives/Public/ietf-http-wg/ [1].
The source code and issues list for this draft can be found at The source code and issues list for this draft can be found at
skipping to change at page 1, line 48 skipping to change at page 1, line 48
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 10, 2020. This Internet-Draft will expire on March 11, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. A Brief History of Integrity Header Fields . . . . . . . 4 1.1. A Brief History of HTTP Integrity Fields . . . . . . . . 4
1.2. This Proposal . . . . . . . . . . . . . . . . . . . . . . 4 1.2. This Proposal . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.3. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.4. Notational Conventions . . . . . . . . . . . . . . . . . 5 1.4. Notational Conventions . . . . . . . . . . . . . . . . . 5
2. Representation Digest . . . . . . . . . . . . . . . . . . . . 6 2. Representation Digest . . . . . . . . . . . . . . . . . . . . 6
3. The Digest Header Field . . . . . . . . . . . . . . . . . . . 6 3. The Digest Field . . . . . . . . . . . . . . . . . . . . . . 6
4. The Want-Digest Header Field . . . . . . . . . . . . . . . . 7 4. The Want-Digest Field . . . . . . . . . . . . . . . . . . . . 7
5. Digest Algorithm Values . . . . . . . . . . . . . . . . . . . 8 5. Digest Algorithm Values . . . . . . . . . . . . . . . . . . . 8
6. Use of Digest when acting on resources . . . . . . . . . . . 10 6. Use of Digest when acting on resources . . . . . . . . . . . 10
6.1. Digest and PATCH . . . . . . . . . . . . . . . . . . . . 11 6.1. Digest and PATCH . . . . . . . . . . . . . . . . . . . . 11
7. Deprecate Negotiation of Content-MD5 . . . . . . . . . . . . 11 7. Deprecate Negotiation of Content-MD5 . . . . . . . . . . . . 11
8. Relationship to Subresource Integrity (SRI) . . . . . . . . . 11 8. Relationship to Subresource Integrity (SRI) . . . . . . . . . 11
8.1. Supporting Both SRI and Representation Digest . . . . . . 12 8.1. Supporting Both SRI and Representation Digest . . . . . . 12
9. Examples of Unsolicited Digest . . . . . . . . . . . . . . . 13 9. Examples of Unsolicited Digest . . . . . . . . . . . . . . . 13
9.1. Server Returns Full Representation Data . . . . . . . . . 13 9.1. Server Returns Full Representation Data . . . . . . . . . 13
9.2. Server Returns No Representation Data . . . . . . . . . . 13 9.2. Server Returns No Representation Data . . . . . . . . . . 13
9.3. Server Returns Partial Representation Data . . . . . . . 13 9.3. Server Returns Partial Representation Data . . . . . . . 13
9.4. Client and Server Provide Full Representation Data . . . 14 9.4. Client and Server Provide Full Representation Data . . . 14
9.5. Client Provides Full Representation Data, Server Provides 9.5. Client Provides Full Representation Data, Server Provides
No Representation Data . . . . . . . . . . . . . . . . . 15 No Representation Data . . . . . . . . . . . . . . . . . 15
9.6. Client and Server Provide Full Representation Data, 9.6. Client and Server Provide Full Representation Data,
Client Uses id-sha-256. . . . . . . . . . . . . . . . . . 15 Client Uses id-sha-256. . . . . . . . . . . . . . . . . . 15
9.7. POST Response does not Reference the Request URI . . . . 16 9.7. POST Response does not Reference the Request URI . . . . 16
9.8. POST Response Describes the Request Status . . . . . . . 17 9.8. POST Response Describes the Request Status . . . . . . . 16
9.9. Digest with PATCH . . . . . . . . . . . . . . . . . . . . 17 9.9. Digest with PATCH . . . . . . . . . . . . . . . . . . . . 17
9.10. Error responses . . . . . . . . . . . . . . . . . . . . . 18 9.10. Error responses . . . . . . . . . . . . . . . . . . . . . 18
9.11. Use with trailers and transfer coding . . . . . . . . . . 19
10. Examples of Want-Digest Solicited Digest . . . . . . . . . . 19 10. Examples of Want-Digest Solicited Digest . . . . . . . . . . 19
10.1. Server Selects Client's Least Preferred Algorithm . . . 19 10.1. Server Selects Client's Least Preferred Algorithm . . . 20
10.2. Server Selects Algorithm Unsupported by Client . . . . . 20 10.2. Server Selects Algorithm Unsupported by Client . . . . . 20
10.3. Server Does Not Support Client Algorithm and Returns an 10.3. Server Does Not Support Client Algorithm and Returns an
Error . . . . . . . . . . . . . . . . . . . . . . . . . 20 Error . . . . . . . . . . . . . . . . . . . . . . . . . 20
11. Security Considerations . . . . . . . . . . . . . . . . . . . 20 11. Security Considerations . . . . . . . . . . . . . . . . . . . 21
11.1. Digest Does Not Protect the Full HTTP Message . . . . . 20 11.1. Digest Does Not Protect the Full HTTP Message . . . . . 21
11.2. Broken Cryptographic Algorithms . . . . . . . . . . . . 21 11.2. Broken Cryptographic Algorithms . . . . . . . . . . . . 21
11.3. Other Deprecated Algorithms . . . . . . . . . . . . . . 21 11.3. Other Deprecated Algorithms . . . . . . . . . . . . . . 21
11.4. Digest for End-to-End Integrity . . . . . . . . . . . . 21 11.4. Digest for End-to-End Integrity . . . . . . . . . . . . 21
11.5. Digest and Content-Location in responses . . . . . . . . 21 11.5. Digest and Content-Location in responses . . . . . . . . 22
11.6. Usage in signatures . . . . . . . . . . . . . . . . . . 21 11.6. Usage in signatures . . . . . . . . . . . . . . . . . . 22
11.7. Message Truncation . . . . . . . . . . . . . . . . . . . 22 11.7. Usage in trailers . . . . . . . . . . . . . . . . . . . 22
11.8. Algorithm Agility . . . . . . . . . . . . . . . . . . . 22 11.8. Usage with encryption . . . . . . . . . . . . . . . . . 23
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 11.9. Algorithm Agility . . . . . . . . . . . . . . . . . . . 23
12.1. Establish the HTTP Digest Algorithm Values . . . . . . . 22 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
12.2. The "status" Field in the HTTP Digest Algorithm Values . 22 12.1. Establish the HTTP Digest Algorithm Values . . . . . . . 23
12.2. The "status" Field in the HTTP Digest Algorithm Values . 23
12.3. Deprecate "MD5" Digest Algorithm . . . . . . . . . . . . 23 12.3. Deprecate "MD5" Digest Algorithm . . . . . . . . . . . . 23
12.4. Update "CRC32C" Digest Algorithm . . . . . . . . . . . . 23 12.4. Update "UNIXsum" Digest Algorithm . . . . . . . . . . . 24
12.5. Obsolete "SHA" Digest Algorithm . . . . . . . . . . . . 23 12.5. Update "UNIXcksum" Digest Algorithm . . . . . . . . . . 24
12.6. Obsolete "ADLER32" Digest Algorithm . . . . . . . . . . 23 12.6. Update "CRC32c" Digest Algorithm . . . . . . . . . . . . 24
12.7. The "ID-SHA-256" Digest Algorithm . . . . . . . . . . . 24 12.7. Obsolete "SHA" Digest Algorithm . . . . . . . . . . . . 24
12.8. The "ID-SHA-512" Digest Algorithm . . . . . . . . . . . 24 12.8. Obsolete "ADLER32" Digest Algorithm . . . . . . . . . . 25
12.9. Changes compared to RFC5843 . . . . . . . . . . . . . . 24 12.9. Obsolete "contentMD5" token in Digest Algorithm . . . . 25
12.10. Want-Digest Header Field Registration . . . . . . . . . 25 12.10. The "id-sha-256" Digest Algorithm . . . . . . . . . . . 25
12.11. Digest Header Field Registration . . . . . . . . . . . . 25 12.11. The "id-sha-512" Digest Algorithm . . . . . . . . . . . 26
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 12.12. Changes compared to RFC5843 . . . . . . . . . . . . . . 26
13.1. Normative References . . . . . . . . . . . . . . . . . . 25 12.13. Want-Digest Field Registration . . . . . . . . . . . . . 26
13.2. Informative References . . . . . . . . . . . . . . . . . 27 12.14. Digest Header Field Registration . . . . . . . . . . . . 26
13.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 28 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
Appendix A. Resource Representation and Representation-Data . . 28 13.1. Normative References . . . . . . . . . . . . . . . . . . 27
Appendix B. FAQ . . . . . . . . . . . . . . . . . . . . . . . . 30 13.2. Informative References . . . . . . . . . . . . . . . . . 28
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 31 13.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Code Samples . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Appendix A. Resource Representation and Representation-Data . . 30
Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Appendix B. FAQ . . . . . . . . . . . . . . . . . . . . . . . . 32
E.1. Since draft-ietf-httpbis-digest-headers-00 . . . . . . . 32 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 33
E.2. Since draft-ietf-httpbis-digest-headers-01 . . . . . . . 33 Code Samples . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33 Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
E.1. Since draft-ietf-httpbis-digest-headers-00 . . . . . . . 34
E.2. Since draft-ietf-httpbis-digest-headers-01 . . . . . . . 35
E.3. Since draft-ietf-httpbis-digest-headers-02 . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35
1. Introduction 1. Introduction
The core specification of HTTP does not define a means to protect the The core specification of HTTP does not define a means to protect the
integrity of resources. When HTTP messages are transferred between integrity of resources. When HTTP messages are transferred between
endpoints, the protocol might choose to make use of features of the endpoints, the protocol might choose to make use of features of the
lower layer in order to provide some integrity protection; for lower layer in order to provide some integrity protection; for
instance TCP checksums or TLS records [RFC2818]. instance TCP checksums or TLS records [RFC2818].
However, there are cases where relying on this alone is insufficient. However, there are cases where relying on this alone is insufficient.
skipping to change at page 4, line 12 skipping to change at page 4, line 18
of data at rest, be used across multiple hops in order to provide of data at rest, be used across multiple hops in order to provide
end-to-end integrity guarantees, aid fault diagnosis across hops and end-to-end integrity guarantees, aid fault diagnosis across hops and
system boundaries, and can be used to validate integrity when system boundaries, and can be used to validate integrity when
reconstructing a resource fetched using different HTTP connections. reconstructing a resource fetched using different HTTP connections.
This document defines a mechanism that acts on HTTP representation- This document defines a mechanism that acts on HTTP representation-
data. It can be combined with other mechanisms that protect data. It can be combined with other mechanisms that protect
representation-metadata, such as digital signatures, in order to representation-metadata, such as digital signatures, in order to
protect the desired parts of an HTTP exchange in whole or in part. protect the desired parts of an HTTP exchange in whole or in part.
1.1. A Brief History of Integrity Header Fields 1.1. A Brief History of HTTP Integrity Fields
The Content-MD5 header field was originally introduced to provide The Content-MD5 header field was originally introduced to provide
integrity, but HTTP/1.1 ([RFC7231], Appendix B) obsoleted it: integrity, but HTTP/1.1 ([RFC7231], Appendix B) obsoleted it:
The Content-MD5 header field has been removed because it was The Content-MD5 header field has been removed because it was
inconsistently implemented with respect to partial responses. inconsistently implemented with respect to partial responses.
[RFC3230] provided a more flexible solution introducing the concept [RFC3230] provided a more flexible solution introducing the concept
of "instance", and the header fields "Digest" and "Want-Digest". of "instance", and the fields "Digest" and "Want-Digest".
1.2. This Proposal 1.2. This Proposal
The concept of "selected representation" defined in [RFC7231] made The concept of "selected representation" defined in Section 7 of
[RFC3230] definitions inconsistent with the current standard. A [SEMANTICS] makes [RFC3230] definitions inconsistent with current
refresh was then required. HTTP semantics. This document updates the "Digest" and "Want-Digest"
field definitions to align with [SEMANTICS] concepts.
This document updates the "Digest" and "Want-Digest" header field
definitions to align with [RFC7231] concepts.
This approach can be easily adapted to use-cases where the Basing "Digest" on the selected representation makes it
transferred data does require some sort of manipulation to be straightforward to apply it to use-cases where the transferred data
considered a representation or conveys a partial representation of a does require some sort of manipulation to be considered a
resource (eg. Range Requests [RFC7233]). representation, or conveys a partial representation of a resource eg.
Range Requests (see Section 9.3 of [SEMANTICS]).
Changes are semantically compatible with existing implementations and Changes are semantically compatible with existing implementations and
better cover both the request and response cases. better cover both the request and response cases.
The value of "Digest" is calculated on selected representation, which The value of "Digest" is calculated on selected representation, which
is tied to the value contained in any "Content-Encoding" or "Content- is tied to the value contained in any "Content-Encoding" or "Content-
Type" header fields. Therefore, a given resource may have multiple Type" header fields. Therefore, a given resource may have multiple
different digest values. different digest values.
To allow both parties to exchange a Digest of a representation with To allow both parties to exchange a Digest of a representation with
no content codings [3] two more algorithms are added ("ID-SHA-256" no content codings (see Section 7.1.2 of [SEMANTICS]) two more
and "ID-SHA-512"). digest-algorithms are added ("id-sha-256" and "id-sha-512").
1.3. Goals 1.3. Goals
The goals of this proposal are: The goals of this proposal are:
1. Digest coverage for either the resource's "representation data" 1. Digest coverage for either the resource's "representation data"
or "selected representation data" communicated via HTTP. or "selected representation data" communicated via HTTP.
2. Support for multiple digest algorithms. 2. Support for multiple digest-algorithms.
3. Negotiation of the use of digests. 3. Negotiation of the use of digests.
The goals do not include: The goals do not include:
HTTP Message integrity: The digest mechanism described here does not HTTP message integrity: The digest mechanism described here does not
cover the full HTTP message nor its semantic, as representation cover the full HTTP message nor its semantic, as representation
metadata are not included in the checksum. metadata are not included in the checksum.
Header field integrity: The digest mechanisms described here cover HTTP field integrity: The digest mechanisms described here cover
only representation and selected representation data, and do not only representation and selected representation data, and do not
protect the integrity of associated representation metadata or protect the integrity of associated representation metadata or
other message header fields. other message fields.
Authentication: The digest mechanisms described here are not meant Authentication: The digest mechanisms described here are not meant
to support authentication of the source of a digest or of a to support authentication of the source of a digest or of a
message or anything else. These mechanisms, therefore, are not a message or anything else. These mechanisms, therefore, are not a
sufficient defense against many kinds of malicious attacks. sufficient defense against many kinds of malicious attacks.
Privacy: Digest mechanisms do not provide message privacy. Privacy: Digest mechanisms do not provide message privacy.
Authorization: The digest mechanisms described here are not meant to Authorization: The digest mechanisms described here are not meant to
support authorization or other kinds of access controls. support authorization or other kinds of access controls.
1.4. Notational Conventions 1.4. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 ([RFC2119] and [RFC8174]) when, and only when, they appear in all 14 ([RFC2119] and [RFC8174]) when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
This document uses the Augmented BNF defined in [RFC5234] and updated This document uses the Augmented BNF defined in [RFC5234] and updated
by [RFC7405] along with the "#rule" extension defined in Section 7 of by [RFC7405] along with the "#rule" extension defined in Section 5 of
[RFC7230]. [SEMANTICS].
The definitions "representation", "selected representation", The definitions "representation", "selected representation",
"representation data", "representation metadata", and "payload body" "representation data", "representation metadata", and "payload body"
in this document are to be interpreted as described in [RFC7230] and in this document are to be interpreted as described in [SEMANTICS].
[RFC7231].
The definition "validator" in this document is to be interpreted as Algorithm names respect the casing used in their definition document
described in Section 7.2 of [RFC7231]. (eg. SHA-1, CRC32c) whereas digest-algorithm tokens are quoted (eg.
"sha", "crc32c").
2. Representation Digest 2. Representation Digest
The representation digest is an integrity mechanism for HTTP The representation digest is an integrity mechanism for HTTP
resources which uses a checksum that is calculated independently of resources which uses a checksum that is calculated independently of
the payload body and message body. It uses the representation data the payload body (see Section 7.3.3 of [SEMANTICS]). It uses the
(see [RFC7231]), that can be fully or partially contained in the representation data (see Section 7.1 of [SEMANTICS]), that can be
message body, or not contained at all: fully or partially contained in the payload body, or not contained at
all:
representation-data := Content-Encoding( Content-Type( bits ) ) representation-data := Content-Encoding( Content-Type( bits ) )
This takes into account the effect of the HTTP semantics on the This takes into account the effect of the HTTP semantics on the
messages; for example the payload body can be affected by Range messages; for example the payload body can be affected by Range
Requests or methods such as HEAD, while the message body is dependent Requests or methods such as HEAD, while the way the payload body is
on transfer codings and other transformations: Appendix A contains transferred "on the wire" is dependent on other transformations (eg.
several examples to help illustrate those effects. transfer codings for HTTP/1.1 see 6.1 of [HTTP11]): Appendix A
contains several examples to help illustrate those effects.
A representation digest consists of the value of a checksum computed A representation digest consists of the value of a checksum computed
on the entire selected "representation data" of a resource together on the entire selected "representation data" (see Section 7 of
with an indication of the algorithm used (and any parameters) [SEMANTICS]) of a resource identified according to Section 7.3.2 of
[SEMANTICS] together with an indication of the algorithm used (and
any parameters)
representation-data-digest = digest-algorithm "=" representation-data-digest = digest-algorithm "="
<encoded digest output> <encoded digest output>
The checksum is computed using one of the "digest-algorithms" listed The checksum is computed using one of the digest-algorithms listed in
in Section 5 and then encoded in the associated format. Section 5 and then encoded in the associated format.
The example below shows the "sha-256" digest-algorithm which uses The example below shows the "sha-256" digest-algorithm which uses
base64 encoding. base64 encoding.
sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE= sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
3. The Digest Header Field 3. The Digest Field
The Digest header field contains a list of one or more representation The "Digest" field contains a list of one or more representation
digest values as defined in Section 2. It can be used in both digest values as defined in Section 2. It can be used in both
request and response. request and response.
Digest = "Digest" ":" OWS 1#representation-data-digest Digest = "Digest" ":" OWS 1#representation-data-digest
The resource is specified by the effective request URI and any The relationship between "Content-Location" (see Section 7.2.5 of
"validator" contained in the message. [SEMANTICS]) and "Digest" is demonstrated in Section 9.7. A
The relationship between Content-Location (see [RFC7231]
Section 3.1.4.2) and Digest is demonstrated in Section 9.7. A
comprehensive set of examples showing the impacts of representation comprehensive set of examples showing the impacts of representation
metadata, payload transformations and HTTP methods on digest is metadata, payload transformations and HTTP methods on Digest is
provided in Section 9 and Section 10. provided in Section 9 and Section 10.
A Digest header field MAY contain multiple representation-data-digest A "Digest" field MAY contain multiple representation-data-digest
values. This could be useful for responses expected to reside in values. This could be useful for responses expected to reside in
caches shared by users with different browsers, for example. caches shared by users with different browsers, for example.
A recipient MAY ignore any or all of the representation-data-digests A recipient MAY ignore any or all of the representation-data-digests
in a Digest header field. This allows the recipient to choose which in a Digest field. This allows the recipient to choose which digest-
digest-algorithm(s) to use for validation instead of verifying every algorithm(s) to use for validation instead of verifying every
received representation-data-digest. received representation-data-digest.
A sender MAY send a representation-data-digest using a digest- A sender MAY send a representation-data-digest using a digest-
algorithm without knowing whether the recipient supports the digest- algorithm without knowing whether the recipient supports the digest-
algorithm, or even knowing that the recipient will ignore it. algorithm, or even knowing that the recipient will ignore it.
"Digest" can be sent in a trailer section. When using incremental
digest-algorithms this allows the sender and the receiver to
dynamically compute the digest value while streaming the content.
Two examples of its use are Two examples of its use are
Digest: id-sha-512=WZDPaVn/7XgHaAy8pmojAkGWoRx2UFChF41A2svX+TaPm Digest: id-sha-512=WZDPaVn/7XgHaAy8pmojAkGWoRx2UFChF41A2svX+TaPm
AbwAgBWnrIiYllu7BNNyealdVLvRwE\nmTHWXvJwew== AbwAgBWnrIiYllu7BNNyealdVLvRwE\nmTHWXvJwew==
Digest: sha-256=4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=, Digest: sha-256=4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=,
id-sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE= id-sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
4. The Want-Digest Header Field 4. The Want-Digest Field
The Want-Digest message header field indicates the sender's desire to The "Want-Digest" field indicates the sender's desire to receive a
receive a representation digest on messages associated with the representation digest on messages associated with the request URI and
request URI and representation metadata. representation metadata.
Want-Digest = "Want-Digest" ":" OWS 1#want-digest-value Want-Digest = "Want-Digest" ":" OWS 1#want-digest-value
want-digest-value = digest-algorithm [ ";" "q" "=" qvalue] want-digest-value = digest-algorithm [ ";" "q" "=" qvalue]
qvalue = ( "0" [ "." 0*1DIGIT ] ) / qvalue = ( "0" [ "." 0*1DIGIT ] ) /
( "1" [ "." 0*1( "0" ) ] ) ( "1" [ "." 0*1( "0" ) ] )
If a digest-algorithm is not accompanied by a qvalue, it is treated If a digest-algorithm is not accompanied by a "qvalue", it is treated
as if its associated qvalue were 1.0. as if its associated "qvalue" were 1.0.
The sender is willing to accept a digest-algorithm if and only if it The sender is willing to accept a digest-algorithm if and only if it
is listed in a Want-Digest header field of a message, and its qvalue is listed in a "Want-Digest" field of a message, and its "qvalue" is
is non-zero. non-zero.
If multiple acceptable digest-algorithm values are given, the If multiple acceptable digest-algorithm values are given, the
sender's preferred digest-algorithm is the one (or ones) with the sender's preferred digest-algorithm is the one (or ones) with the
highest qvalue. highest "qvalue".
Two examples of its use are Two examples of its use are
Want-Digest: sha-256 Want-Digest: sha-256
Want-Digest: SHA-512;q=0.3, sha-256;q=1, md5;q=0 Want-Digest: sha-512;q=0.3, sha-256;q=1, unixsum;q=0
5. Digest Algorithm Values 5. Digest Algorithm Values
Digest algorithm values are used to indicate a specific digest Digest-algorithm values are used to indicate a specific digest
computation. For some algorithms, one or more parameters can be computation. For some digest-algorithms, one or more parameters can
supplied. be supplied.
digest-algorithm = token digest-algorithm = token
The BNF for "parameter" is as is used in [RFC7230]. All digest- The BNF for "parameter" is defined in Section 5.4.1.4 of [SEMANTICS].
algorithm values are case-insensitive. All digest-algorithm values are case-insensitive but the lower case
is preferred.
The Internet Assigned Numbers Authority (IANA) acts as a registry for The Internet Assigned Numbers Authority (IANA) acts as a registry for
digest-algorithm values. The registry contains the tokens listed digest-algorithm values. The registry contains the tokens listed
below. below.
Some algorithms, although registered, have since been found Some digest-algorithms, although registered, rely on vulnerable
vulnerable: the MD5 algorithm MUST NOT be used due to collision algorithms: the "md5" digest-algorithm MUST NOT be used due to
attacks [CMU-836068] and the SHA algorithm is NOT RECOMMENDED due to collision attacks [CMU-836068] and the "sha" digest-algorithm MUST
collision attacks [IACR-2019-459]. NOT be used due to collision attacks [IACR-2020-014].
SHA-256 sha-256
* Description: The SHA-256 algorithm [RFC6234]. The output of * Description: The SHA-256 algorithm [RFC6234]. The output of
this algorithm is encoded using the base64 encoding [RFC4648]. this algorithm is encoded using the base64 encoding [RFC4648].
* Reference: [RFC6234], [RFC4648], this document. * Reference: [RFC6234], [RFC4648], this document.
* Status: standard * Status: standard
SHA-512 sha-512
* Description: The SHA-512 algorithm [RFC6234]. The output of * Description: The SHA-512 algorithm [RFC6234]. The output of
this algorithm is encoded using the base64 encoding [RFC4648]. this algorithm is encoded using the base64 encoding [RFC4648].
* Reference: [RFC6234], [RFC4648], this document. * Reference: [RFC6234], [RFC4648], this document.
* Status: standard * Status: standard
MD5 md5
* Description: The MD5 algorithm, as specified in [RFC1321]. The * Description: The MD5 algorithm, as specified in [RFC1321]. The
output of this algorithm is encoded using the base64 encoding output of this algorithm is encoded using the base64 encoding
[RFC4648]. This digest-algorithm MUST NOT be used as it's now
[RFC4648]. The MD5 algorithm MUST NOT be used as it's now
vulnerable to collision attacks [CMU-836068]. vulnerable to collision attacks [CMU-836068].
* Reference: [RFC1321], [RFC4648], this document. * Reference: [RFC1321], [RFC4648], this document.
* Status: deprecated * Status: deprecated
SHA sha
* Description: The SHA-1 algorithm [RFC3174]. The output of this * Description: The SHA-1 algorithm [RFC3174]. The output of this
algorithm is encoded using the base64 encoding [RFC4648]. The algorithm is encoded using the base64 encoding [RFC4648]. This
SHA algorithm is NOT RECOMMENDED as it's now vulnerable to digest-algorithm MUST NOT be used as it's now vulnerable to
collision attacks [IACR-2019-459]. collision attacks [IACR-2020-014].
* Reference: [RFC3174], [RFC6234], [RFC4648], this document. * Reference: [RFC3174], [RFC6234], [RFC4648], this document.
* Status: obsoleted * Status: deprecated
UNIXsum unixsum
* Description: The algorithm computed by the UNIX "sum" command, * Description: The algorithm computed by the UNIX "sum" command,
as defined by the Single UNIX Specification, Version 2 [UNIX]. as defined by the Single UNIX Specification, Version 2 [UNIX].
The output of this algorithm is an ASCII decimal-digit string The output of this algorithm is an ASCII decimal-digit string
representing the 16-bit checksum, which is the first word of representing the 16-bit checksum, which is the first word of
the output of the UNIX "sum" command. the output of the UNIX "sum" command.
* Reference: [UNIX], this document. * Reference: [UNIX], this document.
* Status: standard * Status: standard
UNIXcksum unixcksum
* Description: The algorithm computed by the UNIX "cksum" * Description: The algorithm computed by the UNIX "cksum"
command, as defined by the Single UNIX Specification, Version 2 command, as defined by the Single UNIX Specification, Version 2
[UNIX]. The output of this algorithm is an ASCII digit string [UNIX]. The output of this algorithm is an ASCII digit string
representing the 32-bit CRC, which is the first word of the representing the 32-bit CRC, which is the first word of the
output of the UNIX "cksum" command. output of the UNIX "cksum" command.
* Reference: [UNIX], this document. * Reference: [UNIX], this document.
* Status: standard * Status: standard
To allow sender and recipient to provide a checksum which is To allow sender and recipient to provide a checksum which is
independent from "Content-Encoding", the following additional independent from "Content-Encoding", the following additional digest-
algorithms are defined: algorithms are defined:
ID-SHA-512 id-sha-512
* Description: The sha-512 digest of the representation-data of * Description: The sha-512 digest of the representation-data of
the resource when no content coding is applied (eg. "Content- the resource when no content coding is applied
Encoding: identity")
* Reference: [RFC6234], [RFC4648], this document. * Reference: [RFC6234], [RFC4648], this document.
* Status: standard * Status: standard
ID-SHA-256 id-sha-256
* Description: The sha-256 digest of the representation-data of * Description: The sha-256 digest of the representation-data of
the resource when no content coding is applied (eg. "Content- the resource when no content coding is applied
Encoding: identity")
* Reference: [RFC6234], [RFC4648], this document. * Reference: [RFC6234], [RFC4648], this document.
* Status: standard * Status: standard
If other digest-algorithm values are defined, the associated encoding If other digest-algorithm values are defined, the associated encoding
MUST either be represented as a quoted string, or MUST NOT include MUST either be represented as a quoted string, or MUST NOT include
";" or "," in the character sets used for the encoding. ";" or "," in the character sets used for the encoding.
6. Use of Digest when acting on resources 6. Use of Digest when acting on resources
skipping to change at page 11, line 27 skipping to change at page 11, line 32
In PATCH responses the representation digest MUST be computed on the In PATCH responses the representation digest MUST be computed on the
selected representation of the patched resource. selected representation of the patched resource.
"Digest" usage with PATCH is thus very similar to the POST one, but "Digest" usage with PATCH is thus very similar to the POST one, but
with the resource's own semantic partly implied by the method and by with the resource's own semantic partly implied by the method and by
the patch document. the patch document.
7. Deprecate Negotiation of Content-MD5 7. Deprecate Negotiation of Content-MD5
This RFC deprecates the negotiation of Content-MD5 as it has been This RFC deprecates the negotiation of Content-MD5 as it has been
obsoleted by [RFC7231]. obsoleted by [RFC7231]. The "contentMD5" token defined in Section 5
of [RFC3230] MUST NOT be used as a digest-algorithm.
8. Relationship to Subresource Integrity (SRI) 8. Relationship to Subresource Integrity (SRI)
Subresource Integrity [SRI] is an integrity mechanism that shares Subresource Integrity [SRI] is an integrity mechanism that shares
some similarities to the present document's mechanism. However, some similarities to the present document's mechanism. However,
there are differences in motivating factors, threat model and there are differences in motivating factors, threat model and
specification of integrity digest generation, signalling and specification of integrity digest generation, signalling and
validation. validation.
SRI allows a first-party authority to declare an integrity assertion SRI allows a first-party authority to declare an integrity assertion
on a resource served by a first or third party authority. This is on a resource served by a first or third party authority. This is
done via the "integrity" attribute that can be added to "script" or done via the "integrity" attribute that can be added to "script" or
"link" HTML elements. Therefore, the integrity assertion is always "link" HTML elements. Therefore, the integrity assertion is always
made out-of-band to the resource fetch. In contrast, the "Digest" made out-of-band to the resource fetch. In contrast, the "Digest"
header field is supplied in-band alongside the selected field is supplied in-band alongside the selected representation,
representation, meaning that an authority can only declare an meaning that an authority can only declare an integrity assertion for
integrity assertion for itself. Methods to improve the security itself. Methods to improve the security properties of representation
properties of representation digests are presented in Section 11. digests are presented in Section 11. This contrast is interesting
This contrast is interesting because on one hand self-assertion is because on one hand self-assertion is less likely to be affected by
less likely to be affected by coordination problems such as the coordination problems such as the first-party holding stale
first-party holding stale information about the third party, but on information about the third party, but on the other hand the self-
the other hand the self-assertion is only as trustworthy as the assertion is only as trustworthy as the authority that provided it.
authority that provided it.
The SRI "integrity" attribute contains a cryptographic hash algorithm The SRI "integrity" attribute contains a cryptographic hash algorithm
and digest value which is similar to "representation-data-digest" and digest value which is similar to "representation-data-digest"
(see Section 2). The major differences are in serialization format. (see Section 2). The major differences are in serialization format.
The SRI digest value is calculated over the identity encoding of the The SRI digest value is calculated over the identity encoding of the
resource, not the selected representation (as specified for resource, not the selected representation (as specified for
"representation-data-digest" in this document). Section 3.4.5 of "representation-data-digest" in this document). Section 3.4.5 of
[SRI] describes the benefit of the identity approach - the SRI [SRI] describes the benefit of the identity approach - the SRI
"integrity" attribute can contain multiple algorithm-value pairs "integrity" attribute can contain multiple algorithm-value pairs
skipping to change at page 12, line 30 skipping to change at page 12, line 33
Range requests). In contrast, this document specifies handling in Range requests). In contrast, this document specifies handling in
terms that are fully compatible with core HTTP concepts (an example terms that are fully compatible with core HTTP concepts (an example
is provided in Section 9.3). is provided in Section 9.3).
SRI specifies strong requirements on the selection of algorithm for SRI specifies strong requirements on the selection of algorithm for
generation and validation of digests. In contrast, the requirements generation and validation of digests. In contrast, the requirements
in this document are weaker. in this document are weaker.
SRI defines no method for a client to declare an integrity assertion SRI defines no method for a client to declare an integrity assertion
on resources it transfers to a server. In contrast, the "Digest" on resources it transfers to a server. In contrast, the "Digest"
header field can appear on requests. field can appear on requests.
8.1. Supporting Both SRI and Representation Digest 8.1. Supporting Both SRI and Representation Digest
The SRI and Representation Digest mechanisms are different and The SRI and Representation Digest mechanisms are different and
complementary but one is not capable of replacing the other because complementary but one is not capable of replacing the other because
they have different threat, security and implementation properties. they have different threat, security and implementation properties.
A user agent that supports both mechanisms is expected to apply the A user agent that supports both mechanisms is expected to apply the
rules specified for each but since the two mechanisms are rules specified for each but since the two mechanisms are
independent, the ordering is not important. However, a user agent independent, the ordering is not important. However, a user agent
skipping to change at page 13, line 8 skipping to change at page 13, line 8
identity encoding. identity encoding.
There is a chance that a user agent supporting both mechanisms may There is a chance that a user agent supporting both mechanisms may
find one validates successfully while the other fails. This document find one validates successfully while the other fails. This document
specifies no requirements or guidance for user agents that experience specifies no requirements or guidance for user agents that experience
such cases. such cases.
9. Examples of Unsolicited Digest 9. Examples of Unsolicited Digest
The following examples demonstrate interactions where a server The following examples demonstrate interactions where a server
responds with a "Digest" header field even though the client did not responds with a "Digest" field even though the client did not solicit
solicit one using "Want-Digest". one using "Want-Digest".
9.1. Server Returns Full Representation Data 9.1. Server Returns Full Representation Data
Request: Request:
GET /items/123 GET /items/123
Response: Response:
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/json Content-Type: application/json
Content-Encoding: identity
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE= Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
{"hello": "world"} {"hello": "world"}
9.2. Server Returns No Representation Data 9.2. Server Returns No Representation Data
Requests without a payload body can still send a "Digest" field
applying the digest-algorithm to an empty representation.
As there is no content coding applied, the "sha-256" and the "id-sha- As there is no content coding applied, the "sha-256" and the "id-sha-
256" digest-values are the same. 256" digest-values in the response are the same.
Request: Request:
HEAD /items/123 HEAD /items/123 HTTP/1.1
Digest: sha-256=47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=
Response: Response:
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/json Content-Type: application/json
Content-Encoding: identity
Digest: id-sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE= Digest: id-sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
9.3. Server Returns Partial Representation Data 9.3. Server Returns Partial Representation Data
Request: Request:
GET /items/123 GET /items/123
Range: bytes=1-7 Range: bytes=1-7
Response: Response:
HTTP/1.1 206 Partial Content HTTP/1.1 206 Partial Content
Content-Type: application/json Content-Type: application/json
Content-Encoding: identity
Content-Range: bytes 1-7/18 Content-Range: bytes 1-7/18
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE= Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
"hello" "hello"
9.4. Client and Server Provide Full Representation Data 9.4. Client and Server Provide Full Representation Data
The request contains a "Digest" header calculated on the enclosed The request contains a "Digest" field calculated on the enclosed
representation. representation.
It also includes an "Accept-Encoding: br" header field that It also includes an "Accept-Encoding: br" header field that
advertises the client supports brotli encoding. advertises the client supports brotli encoding.
The response includes a "Content-Encoding: br" that indicates the The response includes a "Content-Encoding: br" that indicates the
selected representation is brotli encoded. The "Digest" field-value selected representation is brotli encoded. The "Digest" field-value
is therefore different compared to the request. is therefore different compared to the request.
The response body is displayed as a base64-encoded string because it The response body is displayed as a base64-encoded string because it
contains non-printable characters. contains non-printable characters.
Request: Request:
PUT /items/123 PUT /items/123
Content-Type: application/json Content-Type: application/json
Content-Encoding: identity
Accept-Encoding: br Accept-Encoding: br
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE= Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
{"hello": "world"} {"hello": "world"}
Response: Response:
Content-Type: application/json Content-Type: application/json
Content-Encoding: br Content-Encoding: br
Digest: sha-256=4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo= Digest: sha-256=4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=
skipping to change at page 15, line 17 skipping to change at page 15, line 17
Request "Digest" value is calculated on the enclosed payload. Request "Digest" value is calculated on the enclosed payload.
Response "Digest" value depends on the representation metadata header Response "Digest" value depends on the representation metadata header
fields, including "Content-Encoding: br" even when the response does fields, including "Content-Encoding: br" even when the response does
not contain a payload body. not contain a payload body.
Request: Request:
PUT /items/123 PUT /items/123
Content-Type: application/json Content-Type: application/json
Content-Encoding: identity
Content-Length: 18 Content-Length: 18
Accept-Encoding: br Accept-Encoding: br
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE= Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
{"hello": "world"} {"hello": "world"}
Response: Response:
HTTP/1.1 204 No Content HTTP/1.1 204 No Content
Content-Type: application/json Content-Type: application/json
skipping to change at page 16, line 7 skipping to change at page 15, line 48
o one taking into account the "Content-Encoding". o one taking into account the "Content-Encoding".
As the response body contains non-printable characters, it is As the response body contains non-printable characters, it is
displayed as a base64-encoded string. displayed as a base64-encoded string.
Request: Request:
PUT /items/123 HTTP/1.1 PUT /items/123 HTTP/1.1
Content-Type: application/json Content-Type: application/json
Content-Encoding: identity
Accept-Encoding: br Accept-Encoding: br
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE= Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
{"hello": "world"} {"hello": "world"}
Response: Response:
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/json Content-Type: application/json
Content-Encoding: br Content-Encoding: br
Digest: sha-256=4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=, Digest: sha-256=4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=,
id-sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE= id-sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
iwiAeyJoZWxsbyI6ICJ3b3JsZCJ9Aw== iwiAeyJoZWxsbyI6ICJ3b3JsZCJ9Aw==
skipping to change at page 16, line 29 skipping to change at page 16, line 20
id-sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE= id-sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
iwiAeyJoZWxsbyI6ICJ3b3JsZCJ9Aw== iwiAeyJoZWxsbyI6ICJ3b3JsZCJ9Aw==
9.7. POST Response does not Reference the Request URI 9.7. POST Response does not Reference the Request URI
Request "Digest" value is computed on the enclosed representation Request "Digest" value is computed on the enclosed representation
(see Section 6). (see Section 6).
The representation enclosed in the response refers to the resource The representation enclosed in the response refers to the resource
identified by "Content-Location" (see [RFC7231] Section 3.1.4.2 and identified by "Content-Location" (see [SEMANTICS], Section 7.3.2).
Section 3.1.4.1 point 4).
"Digest" is thus computed on the enclosed representation. "Digest" is thus computed on the enclosed representation.
Request: Request:
POST /books HTTP/1.1 POST /books HTTP/1.1
Content-Type: application/json Content-Type: application/json
Accept: application/json Accept: application/json
Accept-Encoding: identity Accept-Encoding: identity
Digest: sha-256=bWopGGNiZtbVgHsG+I4knzfEJpmmmQHf7RHDXA3o1hQ= Digest: sha-256=bWopGGNiZtbVgHsG+I4knzfEJpmmmQHf7RHDXA3o1hQ=
skipping to change at page 19, line 25 skipping to change at page 19, line 15
HTTP/1.1 404 Not Found HTTP/1.1 404 Not Found
Content-Type: application/problem+json Content-Type: application/problem+json
Digest: sha-256=UJSojgEzqUe4UoHzmNl5d2xkmrW3BOdmvsvWu1uFeu0= Digest: sha-256=UJSojgEzqUe4UoHzmNl5d2xkmrW3BOdmvsvWu1uFeu0=
{ {
"title": "Not Found", "title": "Not Found",
"detail": "Cannot PATCH a non-existent resource", "detail": "Cannot PATCH a non-existent resource",
"status": 404 "status": 404
} }
9.11. Use with trailers and transfer coding
An origin server sends "Digest" in the HTTP trailer, so it can
calculate digest-value while streaming content and thus mitigate
resource consumption. The field value is the same as in Section 9.1
because "Digest" is designed to be independent from the use of one or
more transfer codings (see Section 2).
Request:
GET /items/123
Response:
HTTP/1.1 200 OK
Content-Type: application/json
Transfer-Encoding: chunked
Trailer: Digest
8\r\n
{"hello"\r\n
8
: "world\r\n
2\r\n
"}\r\n
0\r\n
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
10. Examples of Want-Digest Solicited Digest 10. Examples of Want-Digest Solicited Digest
The following examples demonstrate interactions where a client The following examples demonstrate interactions where a client
solicits a "Digest" using "Want-Digest". solicits a "Digest" using "Want-Digest".
10.1. Server Selects Client's Least Preferred Algorithm 10.1. Server Selects Client's Least Preferred Algorithm
The client requests a digest, preferring sha. The server is free to The client requests a digest, preferring "sha". The server is free
reply with sha-256 anyway. to reply with "sha-256" anyway.
Request: Request:
GET /items/123 HTTP/1.1 GET /items/123 HTTP/1.1
Want-Digest: sha-256;q=0.3, sha;q=1 Want-Digest: sha-256;q=0.3, sha;q=1
Response: Response:
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/json Content-Type: application/json
Content-Encoding: identity
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE= Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
{"hello": "world"} {"hello": "world"}
10.2. Server Selects Algorithm Unsupported by Client 10.2. Server Selects Algorithm Unsupported by Client
The client requests a sha digest only. The server is currently free The client requests a sha digest only. The server is currently free
to reply with a Digest containing an unsupported algorithm. to reply with a Digest containing an unsupported algorithm.
Request: Request:
GET /items/123 GET /items/123
Want-Digest: sha;q=1 Want-Digest: sha;q=1
Response: Response:
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/json Content-Type: application/json
Content-Encoding: identity
Digest: id-sha-512=WZDPaVn/7XgHaAy8pmojAkGWoRx2UFChF41A2svX+TaPm Digest: id-sha-512=WZDPaVn/7XgHaAy8pmojAkGWoRx2UFChF41A2svX+TaPm
+AbwAgBWnrIiYllu7BNNyealdVLvRwE\nmTHWXvJwew== +AbwAgBWnrIiYllu7BNNyealdVLvRwE\nmTHWXvJwew==
{"hello": "world"} {"hello": "world"}
10.3. Server Does Not Support Client Algorithm and Returns an Error 10.3. Server Does Not Support Client Algorithm and Returns an Error
The client requests a sha Digest, the server advises for sha-256 and The client requests a sha Digest, the server advises for sha-256 and
sha-512 sha-512
skipping to change at page 20, line 45 skipping to change at page 21, line 18
Response: Response:
HTTP/1.1 400 Bad Request HTTP/1.1 400 Bad Request
Want-Digest: sha-256, sha-512 Want-Digest: sha-256, sha-512
11. Security Considerations 11. Security Considerations
11.1. Digest Does Not Protect the Full HTTP Message 11.1. Digest Does Not Protect the Full HTTP Message
This document specifies a data integrity mechanism that protects HTTP This document specifies a data integrity mechanism that protects HTTP
"representation data", but not HTTP "representation metadata" header "representation data", but not HTTP "representation metadata" fields,
fields, from certain kinds of accidental corruption. from certain kinds of accidental corruption.
"Digest" is not intended as general protection against malicious "Digest" is not intended as general protection against malicious
tampering with HTTP messages, this can be achieved by combining it tampering with HTTP messages, this can be achieved by combining it
with other approaches such as transport-layer security or digital with other approaches such as transport-layer security or digital
signatures. signatures.
11.2. Broken Cryptographic Algorithms 11.2. Broken Cryptographic Algorithms
Cryptographic algorithms are intended to provide a proof of integrity Cryptographic algorithms are intended to provide a proof of integrity
suited towards cryptographic constructions such as signatures. suited towards cryptographic constructions such as signatures.
However, these rely on collision-resistance for their security proofs However, these rely on collision-resistance for their security proofs
[CMU-836068]. The MD5 and SHA-1 algorithms are vulnerable to [CMU-836068]. The "MD5" and "SHA-1" digest algorithms are vulnerable
collisions attacks, so MD5 MUST NOT be used and SHA-1 is NOT to collisions attacks, so they MUST NOT be used with "Digest".
RECOMMENDED for use with "Digest".
11.3. Other Deprecated Algorithms 11.3. Other Deprecated Algorithms
The ADLER32 algorithm defined in [RFC1950] has been deprecated by The ADLER32 algorithm defined in [RFC1950] has been deprecated by
[RFC3309] because under certain conditions it provides weak detection [RFC3309] because under certain conditions it provides weak detection
of errors and is now NOT RECOMMENDED for use with "Digest". of errors and is now NOT RECOMMENDED for use with "Digest".
11.4. Digest for End-to-End Integrity 11.4. Digest for End-to-End Integrity
"Digest" alone does not provide end-to-end integrity of HTTP messages "Digest" alone does not provide end-to-end integrity of HTTP messages
over multiple hops, as it just covers the "representation data" and over multiple hops, as it just covers the "representation data" and
not the "representation metadata". not the "representation metadata".
Besides, it allows to protect "representation data" from buggy Besides, it allows to protect "representation data" from buggy
manipulation, buggy compression, etc. manipulation, buggy compression, etc.
Moreover identity digest algorithms (eg. ID-SHA-256 and ID-SHA-512) Moreover identity digest algorithms (eg. "id-sha-256" and "id-sha-
allow piecing together a resource from different sources (e.g. 512") allow piecing together a resource from different sources (e.g.
different servers that perhaps apply different content codings) different servers that perhaps apply different content codings)
enabling the user-agent to detect that the application-layer tasks enabling the user-agent to detect that the application-layer tasks
completed properly, before handing off to say the HTML parser, video completed properly, before handing off to say the HTML parser, video
player etc. player etc.
Even a simple mechanism for end-to-end validation is thus valuable. Even a simple mechanism for end-to-end validation is thus valuable.
11.5. Digest and Content-Location in responses 11.5. Digest and Content-Location in responses
When a state-changing method returns the "Content-Location" header When a state-changing method returns the "Content-Location" header
field, the enclosed representation refers to the resource identified field, the enclosed representation refers to the resource identified
by its value and "Digest" is computed accordingly. by its value and "Digest" is computed accordingly.
11.6. Usage in signatures 11.6. Usage in signatures
Digital signatures are widely used together with checksums to provide Digital signatures are widely used together with checksums to provide
the certain identification of the origin of a message [NIST800-32]. the certain identification of the origin of a message [NIST800-32].
Such signatures can protect one or more HTTP fields and there are
Such signatures can protect one or more header fields and there are
additional considerations when "Digest" is included in this set. additional considerations when "Digest" is included in this set.
Since the "Digest" header field is a hash of a resource Since the "Digest" field is a hash of a resource representation, it
representation, it explicitly depends on the "representation explicitly depends on the "representation metadata" (eg. the values
metadata" (eg. the values of "Content-Type", "Content-Encoding" etc). of "Content-Type", "Content-Encoding" etc). A signature that
A signature that protects "Digest" but not other "representation protects "Digest" but not other "representation metadata" can expose
metadata" can expose the communication to tampering. For example, an the communication to tampering. For example, an actor could
actor could manipulate the "Content-Type" field-value and cause a manipulate the "Content-Type" field-value and cause a digest
digest validation failure at the recipient, preventing the validation failure at the recipient, preventing the application from
application from accessing the representation. Such an attack accessing the representation. Such an attack consumes the resources
consumes the resources of both endpoints. See also Section 11.5. of both endpoints. See also Section 11.5.
"Digest" SHOULD always be used over a connection which provides "Digest" SHOULD always be used over a connection which provides
integrity at the transport layer that protects HTTP header fields. integrity at the transport layer that protects HTTP fields.
A "Digest" header field using NOT RECOMMENDED digest-algorithms A "Digest" field using NOT RECOMMENDED digest-algorithms SHOULD NOT
SHOULD NOT be used in signatures. be used in signatures.
11.7. Message Truncation Using signatures to protect the "Digest" of an empty representation
allows receiving endpoints to detect if an eventual payload has been
stripped or added.
... 11.7. Usage in trailers
11.8. Algorithm Agility When used in trailers, the receiver gets the digest value after the
payload body and may thus be tempted to process the data before
validating the digest value. Instead, data should only be processed
after validating the Digest.
If received in trailers, "Digest" MUST NOT be discarded; instead it
MAY be merged in the header section (See Section 5.6.2 of
[SEMANTICS]).
Not every digest-algorithm is suitable for trailers, as they may
require to pre-process the whole payload before sending a message
(eg. see [I-D.thomson-http-mice]).
11.8. Usage with encryption
"Digest" may expose information details of encrypted payload when the
checksum is computed on the unencrypted data. An example of that is
the use of the "id-sha-256" digest algorithm in conjuction with the
encrypted content-coding [RFC8188].
11.9. Algorithm Agility
... ...
12. IANA Considerations 12. IANA Considerations
12.1. Establish the HTTP Digest Algorithm Values 12.1. Establish the HTTP Digest Algorithm Values
This memo sets this spec to be the establishing document for the HTTP This memo sets this spec to be the establishing document for the HTTP
Digest Algorithm Values [4] Digest Algorithm Values [3]
12.2. The "status" Field in the HTTP Digest Algorithm Values 12.2. The "status" Field in the HTTP Digest Algorithm Values
This memo adds the field "Status" to the HTTP Digest Algorithm Values This memo adds the field "Status" to the HTTP Digest Algorithm Values
[5] registry. The allowed values for the "Status" fields are [4] registry. The allowed values for the "Status" fields are
described below. described below.
Status Specify "standard", "experimental", "historic", "obsoleted", Status Specify "standard", "experimental", "historic", "obsoleted",
or "deprecated" according to the type and status of the primary or "deprecated" according to the type and status of the primary
document in which the algorithm is defined. document in which the algorithm is defined.
12.3. Deprecate "MD5" Digest Algorithm 12.3. Deprecate "MD5" Digest Algorithm
This memo updates the "MD5" digest algorithm in the HTTP Digest This memo updates the "MD5" digest-algorithm in the HTTP Digest
Algorithm Values [5] registry:
o Digest Algorithm: md5
o Description: As specified in Section 5.
o Status: As specified in Section 5.
12.4. Update "UNIXsum" Digest Algorithm
This memo updates the "UNIXsum" digest algorithm in the HTTP Digest
Algorithm Values [6] registry: Algorithm Values [6] registry:
o Digest Algorithm: MD5 o Digest Algorithm: As specified in Section 5.
o Description: As specified in Section 5. o Description: As specified in Section 5.
o Status: As specified in Section 5. o Status: As specified in Section 5.
12.4. Update "CRC32C" Digest Algorithm 12.5. Update "UNIXcksum" Digest Algorithm
This memo updates the "CRC32c" digest algorithm in the HTTP Digest This memo updates the "UNIXcksum" digest algorithm in the HTTP Digest
Algorithm Values [7] registry: Algorithm Values [7] registry:
o Digest Algorithm: CRC32c o Digest Algorithm: As specified in Section 5.
o Description: As specified in Section 5.
o Status: As specified in Section 5.
12.6. Update "CRC32c" Digest Algorithm
This memo updates the "CRC32c" digest-algorithm in the HTTP Digest
Algorithm Values [8] registry:
o Digest Algorithm: crc32c
o Description: The CRC32c algorithm is a 32-bit cyclic redundancy o Description: The CRC32c algorithm is a 32-bit cyclic redundancy
check. It achieves a better hamming distance (for better error- check. It achieves a better hamming distance (for better error-
detection performance) than many other 32-bit CRC functions. detection performance) than many other 32-bit CRC functions.
Other places it is used include iSCSI and SCTP. The 32-bit output Other places it is used include iSCSI and SCTP. The 32-bit output
is encoded in hexadecimal (using between 1 and 8 ASCII characters is encoded in hexadecimal (using between 1 and 8 ASCII characters
from 0-9, A-F, and a-f; leading 0's are allowed). For example, from 0-9, A-F, and a-f; leading 0's are allowed). For example,
CRC32c=0a72a4df and crc32c=A72A4DF are both valid checksums for crc32c=0a72a4df and crc32c=A72A4DF are both valid checksums for
the 3-byte message "dog". the 3-byte message "dog".
o Reference: [RFC4960] appendix B, this document. o Reference: [RFC4960] appendix B, this document.
o Status: standard. o Status: standard.
12.5. Obsolete "SHA" Digest Algorithm 12.7. Obsolete "SHA" Digest Algorithm
This memo updates the "SHA" digest algorithm in the HTTP Digest
Algorithm Values [8] registry:
o Digest Algorithm: SHA This memo updates the "SHA" digest-algorithm in the HTTP Digest
Algorithm Values [9] registry:
o Digest Algorithm: sha
o Description: As specified in Section 5. o Description: As specified in Section 5.
o Status: As specified in Section 5. o Status: As specified in Section 5.
12.6. Obsolete "ADLER32" Digest Algorithm 12.8. Obsolete "ADLER32" Digest Algorithm
This memo updates the "ADLER32" digest algorithm in the HTTP Digest This memo updates the "ADLER32" digest-algorithm in the HTTP Digest
Algorithm Values [9] registry: Algorithm Values [10] registry:
o Digest Algorithm: adler32
o Digest Algorithm: ADLER32
o Description: The ADLER32 algorithm is a checksum specified in o Description: The ADLER32 algorithm is a checksum specified in
[RFC1950] "ZLIB Compressed Data Format". The 32-bit output is [RFC1950] "ZLIB Compressed Data Format". The 32-bit output is
encoded in hexadecimal (using between 1 and 8 ASCII characters encoded in hexadecimal (using between 1 and 8 ASCII characters
from 0-9, A-F, and a-f; leading 0's are allowed). For example, from 0-9, A-F, and a-f; leading 0's are allowed). For example,
ADLER32=03da0195 and ADLER32=3DA0195 are both valid checksums for adler32=03da0195 and adler32=3DA0195 are both valid checksums for
the 4-byte message "Wiki". This algorithm is obsoleted and SHOULD the 4-byte message "Wiki". This algorithm is obsoleted and SHOULD
NOT be used. NOT be used.
o Status: obsoleted o Status: obsoleted
12.7. The "ID-SHA-256" Digest Algorithm 12.9. Obsolete "contentMD5" token in Digest Algorithm
This memo registers the "ID-SHA-256" digest algorithm in the HTTP This memo adds the "contentMD5" token in the HTTP Digest Algorithm
Digest Algorithm Values [10] registry: Values [11] registry:
o Digest Algorithm: ID-SHA-256 o Digest Algorithm: contentMD5
o Description: Section 5 of [RFC3230] defined the "contentMD5" token
to be used only in Want-Digest. This token is obsoleted and MUST
NOT be used.
o Reference: Section 12.9 of this document, Section 5 of [RFC3230].
o Status: obsoleted
12.10. The "id-sha-256" Digest Algorithm
This memo registers the "id-sha-256" digest algorithm in the HTTP
Digest Algorithm Values [12] registry:
o Digest Algorithm: id-sha-256
o Description: As specified in Section 5. o Description: As specified in Section 5.
o Status: As specified in Section 5. o Status: As specified in Section 5.
12.8. The "ID-SHA-512" Digest Algorithm 12.11. The "id-sha-512" Digest Algorithm
This memo registers the "ID-SHA-512" digest algorithm in the HTTP This memo registers the "id-sha-512" digest algorithm in the HTTP
Digest Algorithm Values [11] registry: Digest Algorithm Values [13] registry:
o Digest Algorithm: ID-SHA-512 o Digest Algorithm: id-sha-512
o Description: As specified in Section 5. o Description: As specified in Section 5.
o Status: As specified in Section 5. o Status: As specified in Section 5.
12.9. Changes compared to RFC5843 12.12. Changes compared to RFC5843
The digest-algorithm values for "MD5", "SHA", "SHA-256", "SHA-512",
"UNIXcksum", "UNIXsum", "ADLER32" and "CRC32c" have been updated to
lowercase.
The status of "MD5" has been updated to "deprecated", and its The status of "MD5" has been updated to "deprecated", and its
description states that this algorithm MUST NOT be used. description states that this algorithm MUST NOT be used.
The status of "SHA" has been updated to "obsoleted", and its The status of "SHA" has been updated to "deprecated", and its
description states that this algorithm is NOT RECOMMENDED. description states that this algorithm MUST NOT be used.
The status for "CRC32C" has been updated to "standard". The status for "CRC2c", "UNIXsum" and "UNIXcksum" has been updated to
"standard".
The "ID-SHA-256" and "ID-SHA-512" algorithms have been added to the The "id-sha-256" and "id-sha-512" algorithms have been added to the
registry. registry.
12.10. Want-Digest Header Field Registration 12.13. Want-Digest Field Registration
This section registers the "Want-Digest" header field in the
"Permanent Message Header Field Names" registry ([RFC3864]).
Header field name: "Want-Digest"
Applicable protocol: http This section registers the "Want-Digest" field in the "Hypertext
Transfer Protocol (HTTP) Field Name Registry" [SEMANTICS].
Status: standard Field name: "Want-Digest"
Author/Change controller: IETF Status: permanent
Specification document(s): Section 4 of this document Specification document(s): Section 4 of this document
12.11. Digest Header Field Registration 12.14. Digest Header Field Registration
This section registers the "Digest" header field in the "Permanent
Message Header Field Names" registry ([RFC3864]).
Header field name: "Digest"
Applicable protocol: http
Status: standard This section registers the "Digest" field in the "Hypertext Transfer
Protocol (HTTP) Field Name Registry" [SEMANTICS].
Author/Change controller: IETF Field name: "Digest"
Status: permanent
Specification document(s): Section 3 of this document Specification document(s): Section 3 of this document
13. References 13. References
13.1. Normative References 13.1. Normative References
[CMU-836068] [CMU-836068]
Carnagie Mellon University, Software Engineering Carnagie Mellon University, Software Engineering
Institute, "MD5 Vulnerable to collision attacks", December Institute, "MD5 Vulnerable to collision attacks", December
2008, <https://www.kb.cert.org/vuls/id/836068/>. 2008, <https://www.kb.cert.org/vuls/id/836068/>.
[IACR-2019-459] [IACR-2020-014]
Leurent, G. and T. Peyrin, "From Collisions to Chosen- Leurent, G. and T. Peyrin, "SHA-1 is a Shambles", January
Prefix Collisions Application to Full SHA-1", May 2019, 2020, <https://eprint.iacr.org/2020/014.pdf>.
<https://eprint.iacr.org/2019/459.pdf>.
[NIST800-32] [NIST800-32]
National Institute of Standards and Technology, U.S. National Institute of Standards and Technology, U.S.
Department of Commerce, "Introduction to Public Key Department of Commerce, "Introduction to Public Key
Technology and the Federal PKI Infrastructure", February Technology and the Federal PKI Infrastructure", February
2001, <https://nvlpubs.nist.gov/nistpubs/Legacy/SP/ 2001, <https://nvlpubs.nist.gov/nistpubs/Legacy/SP/
nistspecialpublication800-32.pdf>. nistspecialpublication800-32.pdf>.
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
DOI 10.17487/RFC1321, April 1992, DOI 10.17487/RFC1321, April 1992,
skipping to change at page 26, line 39 skipping to change at page 28, line 5
[RFC3230] Mogul, J. and A. Van Hoff, "Instance Digests in HTTP", [RFC3230] Mogul, J. and A. Van Hoff, "Instance Digests in HTTP",
RFC 3230, DOI 10.17487/RFC3230, January 2002, RFC 3230, DOI 10.17487/RFC3230, January 2002,
<https://www.rfc-editor.org/info/rfc3230>. <https://www.rfc-editor.org/info/rfc3230>.
[RFC3309] Stone, J., Stewart, R., and D. Otis, "Stream Control [RFC3309] Stone, J., Stewart, R., and D. Otis, "Stream Control
Transmission Protocol (SCTP) Checksum Change", RFC 3309, Transmission Protocol (SCTP) Checksum Change", RFC 3309,
DOI 10.17487/RFC3309, September 2002, DOI 10.17487/RFC3309, September 2002,
<https://www.rfc-editor.org/info/rfc3309>. <https://www.rfc-editor.org/info/rfc3309>.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864,
DOI 10.17487/RFC3864, September 2004,
<https://www.rfc-editor.org/info/rfc3864>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>. <https://www.rfc-editor.org/info/rfc4648>.
[RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol", [RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol",
RFC 4960, DOI 10.17487/RFC4960, September 2007, RFC 4960, DOI 10.17487/RFC4960, September 2007,
<https://www.rfc-editor.org/info/rfc4960>. <https://www.rfc-editor.org/info/rfc4960>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, Specifications: ABNF", STD 68, RFC 5234,
skipping to change at page 27, line 19 skipping to change at page 28, line 27
[RFC5843] Bryan, A., "Additional Hash Algorithms for HTTP Instance [RFC5843] Bryan, A., "Additional Hash Algorithms for HTTP Instance
Digests", RFC 5843, DOI 10.17487/RFC5843, April 2010, Digests", RFC 5843, DOI 10.17487/RFC5843, April 2010,
<https://www.rfc-editor.org/info/rfc5843>. <https://www.rfc-editor.org/info/rfc5843>.
[RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms [RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234, (SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011, DOI 10.17487/RFC6234, May 2011,
<https://www.rfc-editor.org/info/rfc6234>. <https://www.rfc-editor.org/info/rfc6234>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>.
[RFC7233] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed.,
"Hypertext Transfer Protocol (HTTP/1.1): Range Requests",
RFC 7233, DOI 10.17487/RFC7233, June 2014,
<https://www.rfc-editor.org/info/rfc7233>.
[RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF", [RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF",
RFC 7405, DOI 10.17487/RFC7405, December 2014, RFC 7405, DOI 10.17487/RFC7405, December 2014,
<https://www.rfc-editor.org/info/rfc7405>. <https://www.rfc-editor.org/info/rfc7405>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[SEMANTICS]
Fielding, R., Nottingham, M., and J. Reschke, "HTTP
Semantics", draft-ietf-httpbis-semantics-11 (work in
progress), August 2020.
[UNIX] The Open Group, "The Single UNIX Specification, Version 2 [UNIX] The Open Group, "The Single UNIX Specification, Version 2
- 6 Vol Set for UNIX 98", February 1997. - 6 Vol Set for UNIX 98", February 1997.
13.2. Informative References 13.2. Informative References
[HTTP11] Fielding, R., Nottingham, M., and J. Reschke, "HTTP/1.1
Messaging", draft-ietf-httpbis-messaging-11 (work in
progress), August 2020.
[I-D.ietf-httpbis-header-structure]
Nottingham, M. and P. Kamp, "Structured Field Values for
HTTP", draft-ietf-httpbis-header-structure-19 (work in
progress), June 2020.
[I-D.thomson-http-mice]
Thomson, M. and J. Yasskin, "Merkle Integrity Content
Encoding", draft-thomson-http-mice-03 (work in progress),
August 2018.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000, DOI 10.17487/RFC2818, May 2000,
<https://www.rfc-editor.org/info/rfc2818>. <https://www.rfc-editor.org/info/rfc2818>.
[RFC5789] Dusseault, L. and J. Snell, "PATCH Method for HTTP", [RFC5789] Dusseault, L. and J. Snell, "PATCH Method for HTTP",
RFC 5789, DOI 10.17487/RFC5789, March 2010, RFC 5789, DOI 10.17487/RFC5789, March 2010,
<https://www.rfc-editor.org/info/rfc5789>. <https://www.rfc-editor.org/info/rfc5789>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>.
[RFC7396] Hoffman, P. and J. Snell, "JSON Merge Patch", RFC 7396, [RFC7396] Hoffman, P. and J. Snell, "JSON Merge Patch", RFC 7396,
DOI 10.17487/RFC7396, October 2014, DOI 10.17487/RFC7396, October 2014,
<https://www.rfc-editor.org/info/rfc7396>. <https://www.rfc-editor.org/info/rfc7396>.
[RFC7807] Nottingham, M. and E. Wilde, "Problem Details for HTTP [RFC7807] Nottingham, M. and E. Wilde, "Problem Details for HTTP
APIs", RFC 7807, DOI 10.17487/RFC7807, March 2016, APIs", RFC 7807, DOI 10.17487/RFC7807, March 2016,
<https://www.rfc-editor.org/info/rfc7807>. <https://www.rfc-editor.org/info/rfc7807>.
[RFC8188] Thomson, M., "Encrypted Content-Encoding for HTTP",
RFC 8188, DOI 10.17487/RFC8188, June 2017,
<https://www.rfc-editor.org/info/rfc8188>.
[SRI] Akhawe, D., Braun, F., Marier, F., and J. Weinberger, [SRI] Akhawe, D., Braun, F., Marier, F., and J. Weinberger,
"Subresource Integrity", W3C Recommendation REC-SRI- "Subresource Integrity", W3C Recommendation REC-SRI-
20160623, June 2016, 20160623, June 2016,
<https://www.w3.org/TR/2016/REC-SRI-20160623/>. <https://www.w3.org/TR/2016/REC-SRI-20160623/>.
13.3. URIs 13.3. URIs
[1] https://lists.w3.org/Archives/Public/ietf-http-wg/ [1] https://lists.w3.org/Archives/Public/ietf-http-wg/
[2] https://github.com/httpwg/http-extensions [2] https://github.com/httpwg/http-extensions
[3] https://tools.ietf.org/html/rfc7231#section-3.1.2.1 [3] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml
[4] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml [4] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml
[5] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml [5] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml
[6] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml [6] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml
[7] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml [7] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml
[8] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml [8] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml
[9] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml [9] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml
[10] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml [10] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml
[11] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml [11] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml
[12] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml
[13] https://www.iana.org/assignments/http-dig-alg/http-dig-alg.xhtml
[14] https://github.com/httpwg/http-core/
issues/313#issuecomment-584389706
Appendix A. Resource Representation and Representation-Data Appendix A. Resource Representation and Representation-Data
The following examples show how representation metadata, payload The following examples show how representation metadata, payload
transformations and method impacts on the message and payload body. transformations and method impacts on the message and payload body.
When the payload body contains non-printable characters (eg. when it When the payload body contains non-printable characters (eg. when it
is compressed) it is shown as base64-encoded string. is compressed) it is shown as base64-encoded string.
Here is a gzip-compressed json object A request with a json object without any content coding.
Request:
PUT /entries/1234 HTTP/1.1
Content-Type: application/json
{"hello": "world"}
Here is a gzip-compressed json object using a content coding.
Request: Request:
PUT /entries/1234 HTTP/1.1 PUT /entries/1234 HTTP/1.1
Content-Type: application/json Content-Type: application/json
Content-Encoding: gzip Content-Encoding: gzip
H4sIAItWyFwC/6tWSlSyUlAypANQqgUAREcqfG0AAAA= H4sIAItWyFwC/6tWSlSyUlAypANQqgUAREcqfG0AAAA=
Now the same payload body conveys a malformed json object. Now the same payload body conveys a malformed json object.
skipping to change at page 31, line 16 skipping to change at page 32, line 51
the references here to delta encoding don't add anything to this the references here to delta encoding don't add anything to this
RFC. Another job would be to refresh delta encoding. RFC. Another job would be to refresh delta encoding.
5. Why remove references to Digest Authentication? 5. Why remove references to Digest Authentication?
This RFC seems to me completely unrelated to Digest This RFC seems to me completely unrelated to Digest
Authentication but for the word "Digest". Authentication but for the word "Digest".
6. What changes in "Want-Digest"? 6. What changes in "Want-Digest"?
We allow to use the "Want-Digest" in responses to advertise the The contentMD5 token defined in Section 5 of [RFC3230] is
supported digest-algorithms and the inability to accept requests deprecated by Section 7.
with unsupported digest-algorithms.
To clarify that "Digest" and "Want-Digest" can be used in both
requests and responses - [RFC3230] carefully uses "sender" and
"receiver" in their definition - we added examples on using
"Want-Digest" in responses to advertise the supported digest-
algorithms and the inability to accept requests with unsupported
digest-algorithms.
7. Does this spec changes supported algorithms? 7. Does this spec changes supported algorithms?
This RFC updates [RFC5843] which is still delegated for all This RFC updates [RFC5843] which is still delegated for all
algorithms updates, and adds two more algorithms: ID-SHA-256 and algorithms updates, and adds two more algorithms: "id-sha-256"
ID-SHA-512 which allows to send a checksum of a resource and "id-sha-512" which allows to send a checksum of a resource
representation with no content codings applied. representation with no content codings applied. To simplify a
future transition to Structured Fields
[I-D.ietf-httpbis-header-structure] we suggest to use lowercase
for digest-algorithms.
8. What about mid-stream trailers?
While mid-stream trailers [14] are interesting, since this
specification is a rewrite of [RFC3230] we do not think we should
face that. As a first thought, nothing in this document
precludes future work that would find a use for mid-stream
trailers, for example an incremental digest-algorithm. A
document defining such a digest-algorithm is best positioned to
describe how it is used.
Acknowledgements Acknowledgements
The vast majority of this document is inherited from [RFC3230], so The vast majority of this document is inherited from [RFC3230], so
thanks to J. Mogul and A. Van Hoff for their great work. The thanks to J. Mogul and A. Van Hoff for their great work. The
original idea of refreshing this document arose from an interesting original idea of refreshing this document arose from an interesting
discussion with M. Nottingham, J. Yasskin and M. Thomson when discussion with M. Nottingham, J. Yasskin and M. Thomson when
reviewing the MICE content coding. reviewing the MICE content coding.
Code Samples Code Samples
_RFC Editor: Please remove this section before publication._ _RFC Editor: Please remove this section before publication._
How can I generate and validate the Digest values shown in the How can I generate and validate the "Digest" values shown in the
examples throughout this document? examples throughout this document?
The following python3 code can be used to generate digests for json The following python3 code can be used to generate digests for json
objects using SHA algorithms for a range of encodings. Note that objects using SHA algorithms for a range of encodings. Note that
these are formatted as base64. This function could be adapted to these are formatted as base64. This function could be adapted to
other algorithms and should take into account their specific other algorithms and should take into account their specific
formatting rules. formatting rules.
import base64, json, hashlib, brotli import base64, json, hashlib, brotli
skipping to change at page 33, line 19 skipping to change at page 35, line 19
o Digest of error responses is computed on the error representation- o Digest of error responses is computed on the error representation-
data #1004 data #1004
o Effect of HTTP semantics on payload and message body moved to o Effect of HTTP semantics on payload and message body moved to
appendix #1122 appendix #1122
o Editorial refactoring, moving headers sections up. #1109-#1112, o Editorial refactoring, moving headers sections up. #1109-#1112,
#1116, #1117, #1122-#1124 #1116, #1117, #1122-#1124
E.3. Since draft-ietf-httpbis-digest-headers-02
o Deprecate SHA-1 #1154
o Avoid id-* with encrypted content
o Digest is independent from MESSAGING and HTTP/1.1 is not normative
#1215
o Identity is not a valid field value for content-encoding #1223
o Mention trailers #1157
o Reference httpbis-semantics #1156
o Add contentMD5 as an obsoleted digest-algorithm #1249
o Use lowercase digest-algorithms names in the doc and in the
digest-algorithm IANA table.
Authors' Addresses Authors' Addresses
Roberto Polli Roberto Polli
Team Digitale, Italian Government Team Digitale, Italian Government
Email: robipolli@gmail.com Email: robipolli@gmail.com
Lucas Pardue Lucas Pardue
Cloudflare Cloudflare
 End of changes. 138 change blocks. 
261 lines changed or deleted 408 lines changed or added

This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/