Internet DRAFT - draft-polli-resource-digests-http
draft-polli-resource-digests-http
Network Working Group R. Polli
Internet-Draft
Intended status: Standards Track L. Pardue
Expires: November 24, 2019 May 23, 2019
Resource Digests for HTTP
draft-polli-resource-digests-http-00
Abstract
This document defines the Digest and Want-Digest header fields for
HTTP, thus allowing client and server to negotiate an integrity
checksum of the exchanged resource representation data.
This document obsoletes [RFC3230]. It replaces the term "instance"
with "representation", which makes it consistent with the HTTP
Semantic and Context defined in [RFC7231].
Note to Readers
_RFC EDITOR: please remove this section before publication_
Discussion of this draft takes place on the HTTP working group
mailing list (ietf-http-wg@w3.org), which is archived at
https://lists.w3.org/Archives/Public/ietf-http-wg/ [1].
The source code and issues list for this draft can be found at
https://github.com/ioggstream/draft-polli-resource-digests-http [2].
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
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This Internet-Draft will expire on November 24, 2019.
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Copyright Notice
Copyright (c) 2019 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Brief history of integrity headers . . . . . . . . . . . 4
1.2. This proposal . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4. Notational Conventions . . . . . . . . . . . . . . . . . 5
2. Resource representation and representation-data . . . . . . . 5
3. Digest Algorithm values . . . . . . . . . . . . . . . . . . . 7
3.1. Representation digest . . . . . . . . . . . . . . . . . . 9
3.1.1. digest-algorithm encoding examples . . . . . . . . . 9
4. Header Specifications . . . . . . . . . . . . . . . . . . . . 10
4.1. Want-Digest . . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Digest . . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Deprecate Negotiation of Content-MD5 . . . . . . . . . . . . 11
6. Broken cryptographic algorithms are NOT RECOMMENDED . . . . . 11
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. Unsolicited Digest response . . . . . . . . . . . . . . . 11
7.1.1. Representation data is fully contained in the payload 11
7.1.2. Representation data is not contained in the payload . 12
7.1.3. Representation data is partially contained in the
payload i.e. range request . . . . . . . . . . . . . 12
7.1.4. Digest in both Request and Response. Returned value
depends on representation metadata . . . . . . . . . 13
7.2. Want-Digest solicited digest responses . . . . . . . . . 13
7.2.1. Client request data is fully contained in the payload 13
7.2.2. A client requests an unsupported Digest, the server
MAY reply with an unsupported digest . . . . . . . . 14
7.2.3. A client requests an unsupported Digest, the server
MAY reply with a 400 . . . . . . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
8.1. Digest does not protect the full HTTP message . . . . . . 14
8.2. Broken cryptographic algorithms . . . . . . . . . . . . . 15
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8.3. Digest for end-to-end integrity . . . . . . . . . . . . . 15
8.4. Usage in signatures . . . . . . . . . . . . . . . . . . . 15
8.5. Message Truncation . . . . . . . . . . . . . . . . . . . 16
8.6. Algorithm Agility . . . . . . . . . . . . . . . . . . . . 16
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
9.1. Establish the HTTP Digest Algorithm Values . . . . . . . 16
9.2. The "status" field in the HTTP Digest Algorithm Values . 16
9.3. Obsolete "MD5" Digest Algorithm . . . . . . . . . . . . . 16
9.4. Obsolete "SHA" Digest Algorithm . . . . . . . . . . . . . 16
9.5. The "ID-SHA-256" Digest Algorithm . . . . . . . . . . . . 17
9.6. The "ID-SHA-512" Digest Algorithm . . . . . . . . . . . . 17
9.7. Changes compared to RFC5843 . . . . . . . . . . . . . . . 17
9.8. Want-Digest Header Field Registration . . . . . . . . . . 17
9.9. Digest Header Field Registration . . . . . . . . . . . . 18
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
10.1. Normative References . . . . . . . . . . . . . . . . . . 18
10.2. Informative References . . . . . . . . . . . . . . . . . 20
10.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 21
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 21
Appendix C. FAQ . . . . . . . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction
Integrity protection for HTTP content is multi layered and is usually
achieved across the protocol stack: TCP checksums and TLS record to
name but some.
The HTTP protocol does not provide means to protect the various
message parts. Besides, it might be desirable to add additional
guarantees to the ones provided by the transport layer (eg. HTTPS).
This may be in order to:
o detect programming errors and corruption of stored data;
o address the need for the representation-data to remain unmodified
throughout multiple hops;
o implement signature mechanisms that cover the desired parts of an
HTTP exchange;
o provide additional protection against failures or attack (see
[SRI]).
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1.1. Brief history of integrity headers
The Content-MD5 header field was originally introduced to provide
integrity, but HTTP/1.1 [RFC7231] in appendix-B obsoleted it:
The Content-MD5 header field has been removed because it was
inconsistently implemented with respect to partial responses.
[RFC3230] provided a more flexible solution introducing the concept
of "instance", and the headers "Digest" and "Want-Digest".
1.2. This proposal
The concept of "selected representation" defined in [RFC7231] made
[RFC3230] definitions inconsistent with the current standard. A
refresh was then required.
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
transferred data does require some sort of manipulation to be
considered a representation or conveys a partial representation of a
resource (eg. Range Requests).
Changes are semantically compatible with existing implementations and
better cover both the request and response cases.
The value of "Digest" is calculated on selected representation, which
is tied to the value contained in any "Content-Encoding" or "Content-
Type" header fields. Therefore, a given resource may have multiple
different digest values.
To allow both parties to exchange a Digest of a representation with
no content codings [3] two more algorithms are added ("ID-SHA-256"
and "ID-SHA-512").
1.3. Goals
The goals of this proposal are:
1. Digest coverage for either the resource's "representation data"
or "selected representation data" communicated via HTTP.
2. Support for multiple digest algorithms.
3. Negotiation of the use of digests.
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The goals do not include:
HTTP Message integrity: The digest mechanism described here does not
cover the full HTTP message nor its semantic, as representation
metadata are not included in the checksum.
Header integrity: The digest mechanisms described here cover only
representation and selected representation data, and do not
protect the integrity of associated representation metadata
headers or other message headers.
Authentication: The digest mechanisms described here are not meant
to support authentication of the source of a digest or of a
message or anything else. These mechanisms, therefore, are not a
sufficient defense against many kinds of malicious attacks.
Privacy: Digest mechanisms do not provide message privacy.
Authorization: The digest mechanisms described here are not meant to
support authorization or other kinds of access controls.
1.4. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 ([RFC2119] and [RFC8174]) when, and only when, they appear in all
capitals, as shown here.
The definitions "representation", "selected representation",
"representation data", "representation metadata" and "payload body"
in this document are to be interpreted as described in [RFC7230] and
[RFC7231].
2. Resource representation and representation-data
To avoid inconsistencies, an integrity mechanism for HTTP messages
should decouple the checksum calculation:
o from the payload body - which may be altered by mechanism like
Range Requests or the method (eg. HEAD);
o and from the message body - which depends on "Transfer-Encoding"
and whatever tranformations the intermediaries may apply.
The following examples show how representation metadata, payload
tranformations and method impacts on the message and payload body.
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Here is a gzip-compressed json object
Request:
PUT /entries/1234 HTTP/1.1
Content-Type: application/json
Content-Encoding: gzip
H4sIAItWyFwC/6tWSlSyUlAypANQqgUAREcqfG0AAAA=
Now the same payload body conveys a malformed json object.
Request:
PUT /entries/1234 HTTP/1.1
Content-Type: application/json
H4sIAItWyFwC/6tWSlSyUlAypANQqgUAREcqfG0AAAA=
A Range-Request alters the payload body, conveying a partial
representation.
Request:
GET /entries/1234 HTTP/1.1
Range: bytes=1-7
Response:
HTTP/1.1 206 Partial Content
Content-Encoding: gzip
Content-Type: application/json
Content-Range: bytes=1-7
iwgAla3RXA==
Now the method too alters the payload body.
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Request:
HEAD /entries/1234 HTTP/1.1
Accept: application/json
Accept-Encoding: gzip
Response:
HTTP/1.1 200 OK
Content-Type: application/json
Content-Encoding: gzip
3. Digest Algorithm values
Digest algorithm values are used to indicate a specific digest
computation. For some algorithms, one or more parameters may be
supplied.
digest-algorithm = token
The BNF for "parameter" is as is used in [RFC7230]. All digest-
algorithm values are case-insensitive.
The Internet Assigned Numbers Authority (IANA) acts as a registry for
digest-algorithm values. The registry contains the following tokens.
SHA-256:
* Description: The SHA-256 algorithm [FIPS180-3]. The output of
this algorithm is encoded using the base64 encoding [RFC4648].
* Reference: [FIPS180-3], [RFC4648], this document.
* Status: standard
SHA-512:
* Description: The SHA-512 algorithm [FIPS180-3]. The output of
this algorithm is encoded using the base64 encoding [RFC4648].
* Reference: [FIPS180-3], [RFC4648], this document.
* Status: standard
MD5:
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* Description: The MD5 algorithm, as specified in [RFC1321]. The
output of this algorithm is encoded using the base64 encoding
[RFC4648]. The MD5 algorithm is NOT RECOMMENDED as it's now
vulnerable to collision attacks [CMU-836068].
* Reference: [RFC1321], [RFC4648], this document.
* Status: obsoleted
SHA:
* Description: The SHA-1 algorithm [FIPS180-1]. The output of
this algorithm is encoded using the base64 encoding [RFC4648].
The SHA algorithm is NOT RECOMMENDED as it's now vulnerable to
collision attacks [IACR-2019-459].
* Reference: [FIPS-180-3], [RFC4648], this document.
* Status: obsoleted
UNIXsum:
* Description: The algorithm computed by the UNIX "sum" command,
as defined by the Single UNIX Specification, Version 2 [UNIX].
The output of this algorithm is an ASCII decimal-digit string
representing the 16-bit checksum, which is the first word of
the output of the UNIX "sum" command.
* Reference: [UNIX], this document.
* Status: standard
UNIXcksum:
* Description: The algorithm computed by the UNIX "cksum"
command, as defined by the Single UNIX Specification, Version 2
[UNIX]. The output of this algorithm is an ASCII digit string
representing the 32-bit CRC, which is the first word of the
output of the UNIX "cksum" command.
* Reference: [UNIX], this document.
* Status: standard
To allow sender and recipient to provide a checksum which is
independent from "Content-Encoding", the following additional
algorithms are defined:
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ID-SHA-512:
* Description: The sha-512 digest of the representation-data of
the resource when no content coding is applied (eg. "Content-
Encoding: identity")
* Reference: [FIPS180-3], [RFC4648], this document.
* Status: standard
ID-SHA-256:
* Description: The sha-256 digest of the representation-data of
the resource when no content coding is applied (eg. "Content-
Encoding: identity")
* Reference: [FIPS180-3], [RFC4648], this document.
* Status: standard
If other digest-algorithm values are defined, the associated encoding
MUST either be represented as a quoted string, or MUST NOT include
";" or "," in the character sets used for the encoding.
3.1. Representation digest
A representation digest is the value of the output of a digest
algorithm, together with an indication of the algorithm used (and any
parameters).
representation-data-digest = digest-algorithm "="
<encoded digest output>
As explained in Section 2 the digest is computed on the entire
selected "representation data" of the resource defined in [RFC7231]:
representation-data := Content-Encoding( Content-Type( bits ) )
The encoded digest output uses the encoding format defined for the
specific digest-algorithm.
3.1.1. digest-algorithm encoding examples
The "sha-256" digest-algorithm uses base64 encoding. Note that
digest-algoritm values are case insensitive.
sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
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The "UNIXsum" digest-algorithm uses ASCII string of decimal digits.
UNIXsum=30637
4. Header Specifications
The following headers are defined
4.1. Want-Digest
The Want-Digest message header field indicates the sender's desire to
receive a representation digest on messages associated with the
Request- URI and representation metadata.
Want-Digest = "Want-Digest" ":"
#(digest-algorithm [ ";" "q" "=" qvalue])
If a digest-algorithm is not accompanied by a qvalue, it is treated
as if its associated qvalue were 1.0.
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 non-zero.
If multiple acceptable digest-algorithm values are given, the
sender's preferred digest-algorithm is the one (or ones) with the
highest qvalue.
Examples:
Want-Digest: sha-256
Want-Digest: SHA-256;q=0.3, sha;q=1
4.2. Digest
The Digest header field provides a digest of the representation data
Digest = "Digest" ":" #(representation-data-digest)
"Representation data" might be:
o fully contained in the message body,
o partially-contained in the message body,
o or not at all contained in the message body.
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The resource is specified by the effective Request-URI and any cache-
validator contained in the message.
For example, in a response to a HEAD request, the digest is
calculated using the representation data that would have been
enclosed in the payload body if the same request had been a GET.
Digest can be used in requests too. Returned value depends on the
representation metadata headers.
A Digest header field MAY contain multiple representation-data-digest
values. This could be useful for responses expected to reside in
caches shared by users with different browsers, for example.
A recipient MAY ignore any or all of the representation-data-digests
in a Digest header field.
A sender MAY send a representation-data-digest using a digest-
algorithm without knowing whether the recipient supports the digest-
algorithm, or even knowing that the recipient will ignore it.
...
5. Deprecate Negotiation of Content-MD5
This RFC deprecates the negotiation of Content-MD5 as this header has
been obsoleted by [RFC7231]
6. Broken cryptographic algorithms are NOT RECOMMENDED
The MD5 algorithm is NOT RECOMMENDED as it's now vulnerable to
collision attacks [CMU-836068].
The SHA algorithm is NOT RECOMMENDED as it's now vulnerable to
collision attacks [IACR-2019-459].
7. Examples
7.1. Unsolicited Digest response
7.1.1. Representation data is fully contained in the payload
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Request:
GET /items/123
Response:
HTTP/1.1 200 Ok
Content-Type: application/json
Content-Encoding: identity
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
{"hello": "world"}
7.1.2. Representation data is not contained in the payload
Request:
HEAD /items/123
Response:
HTTP/1.1 200 Ok
Content-Type: application/json
Content-Encoding: identity
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
7.1.3. Representation data is partially contained in the payload i.e.
range request
Request:
GET /items/123
Range: bytes=1-7
Response:
HTTP/1.1 206 Partial Content
Content-Type: application/json
Content-Encoding: identity
Content-Range: bytes 1-7/18
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
"hello"
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7.1.4. Digest in both Request and Response. Returned value depends on
representation metadata
Digest can be used in requests too. Returned value depends on the
representation metadata headers.
Request:
PUT /items/123
Content-Type: application/json
Content-Encoding: identity
Accept-Encoding: br
Digest: sha-256=4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=
{"hello": "world"}
Response:
Content-Type: application/json
Content-Encoding: br
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
b'\x8b\x08\x80{"hello": "world"}\x03'
7.2. Want-Digest solicited digest responses
7.2.1. Client request data is fully contained in the payload
The client requests a digest, preferring sha. The server is free to
reply with sha-256 anyway.
Request:
GET /items/123
Want-Digest: sha-256;q=0.3, sha;q=1
Response:
HTTP/1.1 200 Ok
Content-Type: application/json
Content-Encoding: identity
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
{"hello": "world"}
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7.2.2. A client requests an unsupported Digest, the server MAY reply
with an unsupported digest
The client requests a sha digest only. The server is currently free
to reply with a Digest containing an unsupported algorithm
Request:
GET /items/123
Want-Digest: sha;q=1
Response:
HTTP/1.1 200 Ok
Content-Type: application/json
Content-Encoding: identity
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
{"hello": "world"}
7.2.3. A client requests an unsupported Digest, the server MAY reply
with a 400
The client requests a sha Digest, the server advises for sha-256 and
sha-512
Request:
GET /items/123
Want-Digest: sha;q=1
Response:
HTTP/1.1 400 Bad Request
Want-Digest: sha-256, sha-512
...
8. Security Considerations
8.1. Digest does not protect the full HTTP message
This document specifies a data integrity mechanism that protects HTTP
"representation data", but not HTTP "representation metadata"
headers, from certain kinds of accidental corruption.
While it is not intended as general protection against malicious
tampering with HTTP messages, this goal can be achieved using
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"Digest" together with a transport-layer security mechanism and
digital signatures.
8.2. Broken cryptographic algorithms
Cryptogrphic alorithms are intended to provide a proof of integrity
suited towards cryptographic constructions such as signatures.
However, these rely on collision-resistance for their security proofs
[CMU-836068]. The MD5 and SHA-1 algorithms are vulnerable to
collisions attacks and they are NOT RECOMMENDED.
8.3. Digest for end-to-end integrity
"Digest" alone does not provide end-to-end integrity of HTTP messages
over multiple hops, as it just covers the "representation data" and
not the "representation metadata".
Besides, it allows to protect "representation data" from buggy
manipulation, buggy compression, etc.
Moreover identity digest algorithms (eg. ID-SHA-256 and ID-SHA-512)
allow piecing together a resource from different sources (e.g.
different servers that perhaps apply different content codings)
enabling the user-agent to detect that the application-layer tasks
completed properly, before handing off to say the HTML parser, video
player etc.
Even a simple mechanism for end-to-end validation is thus valuable.
8.4. Usage in signatures
Digital signatures are widely used together with checksums to provide
the certain identification of the origin of a message [NIST800-32].
It's important to note that, being the "Digest" header an hash of a
resource representation, signing only the "Digest" header, without
all the "representation metatada" (eg. the values of "Content-Type"
and "Content-Encoding") may expose the communication to tampering.
"Digest" SHOULD always be used over a connection which provides
integrity at transport layer that protects HTTP headers.
A "Digest" header using NOT RECOMMENDED digest-algorithms SHOULD NOT
be used in signatures.
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8.5. Message Truncation
...
8.6. Algorithm Agility
...
9. IANA Considerations
9.1. Establish the HTTP Digest Algorithm Values
This memo sets this spec to be the establishing document for the HTTP
Digest Algorithm Values [4]
9.2. The "status" field in 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
described below.
Status Specify "standard", "experimental", "historic", "obsoleted",
or "deprecated" according to the type and status of the primary
document in which the algorithm is defined.
9.3. Obsolete "MD5" Digest Algorithm
This memo updates the "MD5" digest algorithm in the HTTP Digest
Algorithm Values [6] registry:
o Digest Algorithm: MD5
o Description: As specified in Section 3.
o Status: As specified in Section 3.
9.4. Obsolete "SHA" Digest Algorithm
This memo updates the "SHA" digest algorithm in the HTTP Digest
Algorithm Values [7] registry:
o Digest Algorithm: SHA
o Description: As specified in Section 3.
o Status: As specified in Section 3.
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9.5. The "ID-SHA-256" Digest Algorithm
This memo registers the "ID-SHA-256" digest algorithm in the HTTP
Digest Algorithm Values [8] registry:
o Digest Algorithm: ID-SHA-256
o Description: As specified in Section 3.
o Status: As specified in Section 3.
9.6. The "ID-SHA-512" Digest Algorithm
This memo registers the "ID-SHA-512" digest algorithm in the HTTP
Digest Algorithm Values [9] registry:
o Digest Algorithm: ID-SHA-512
o Description: As specified in Section 3.
o Status: As specified in Section 3.
9.7. Changes compared to RFC5843
The status has been updated to "obsoleted" for both "SHA" and "MD5",
and their descriptions states that those algorithms are NOT
RECOMMENDED.
The status for all other algorithms have been updated to "standard".
The "ID-SHA-256" and "ID-SHA-512" algorithms have been added to the
registry.
9.8. Want-Digest Header 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
Status: standard
Author/Change controller: IETF
Specification document(s): Section 4.1 of this document
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9.9. 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
Author/Change controller: IETF
Specification document(s): Section 4.2 of this document
10. References
10.1. Normative References
[CMU-836068]
Carnagie Mellon University, Software Engineering
Institute, ., "MD5 Vulnerable to collision attacks",
December 2008, <https://www.kb.cert.org/vuls/id/836068/>.
[FIPS180-1]
Department of Commerce, National., "NIST FIPS 180-1,
Secure Hash Standard", April 1995,
<http://csrc.nist.gov/fips/fip180-1.txt>.
[FIPS180-3]
Department of Commerce, National., "NIST FIPS 180-3,
Secure Hash Standard", October 2008,
<https://csrc.nist.gov/csrc/media/publications/fips/180/3/
archive/2008-10-31/documents/fips180-3_final.pdf>.
[FIPS180-4]
Department of Commerce, National., "NIST FIPS 180-4,
Secure Hash Standard", March 2012,
<http://csrc.nist.gov/publications/fips/fips180-4/
fips-180-4.pdf>.
[IACR-2019-459]
Inria, France; Nanyang Technological University,
Singapore; Temasek Laboratories, Singapore, ., "From
Collisions to Chosen-Prefix Collisions Application to Full
SHA-1", May 2019, <https://eprint.iacr.org/2019/459.pdf>.
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[NIST800-32]
Department of Commerce, National., "Introduction to Public
Key Technology and the Federal PKI Infrastructure",
February 2001,
<https://nvlpubs.nist.gov/nistpubs/Legacy/SP/
nistspecialpublication800-32.pdf>.
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
DOI 10.17487/RFC1321, April 1992,
<https://www.rfc-editor.org/info/rfc1321>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3230] Mogul, J. and A. Van Hoff, "Instance Digests in HTTP",
RFC 3230, DOI 10.17487/RFC3230, January 2002,
<https://www.rfc-editor.org/info/rfc3230>.
[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
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>.
[RFC5789] Dusseault, L. and J. Snell, "PATCH Method for HTTP",
RFC 5789, DOI 10.17487/RFC5789, March 2010,
<https://www.rfc-editor.org/info/rfc5789>.
[RFC5843] Bryan, A., "Additional Hash Algorithms for HTTP Instance
Digests", RFC 5843, DOI 10.17487/RFC5843, April 2010,
<https://www.rfc-editor.org/info/rfc5843>.
[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>.
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[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[UNIX] The Open Group, ., "The Single UNIX Specification, Version
2 - 6 Vol Set for UNIX 98", February 1997.
10.2. Informative References
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000,
<https://www.rfc-editor.org/info/rfc2818>.
[RFC5788] Melnikov, A. and D. Cridland, "IMAP4 Keyword Registry",
RFC 5788, DOI 10.17487/RFC5788, March 2010,
<https://www.rfc-editor.org/info/rfc5788>.
[RFC6962] Laurie, B., Langley, A., and E. Kasper, "Certificate
Transparency", RFC 6962, DOI 10.17487/RFC6962, June 2013,
<https://www.rfc-editor.org/info/rfc6962>.
[RFC7396] Hoffman, P. and J. Snell, "JSON Merge Patch", RFC 7396,
DOI 10.17487/RFC7396, October 2014,
<https://www.rfc-editor.org/info/rfc7396>.
[SRI] Akhawe, D., Braun, F., Marier, F., and J. Weinberger,
"Subresource Integrity", n.d..
10.3. URIs
[1] https://lists.w3.org/Archives/Public/ietf-http-wg/
[2] https://github.com/ioggstream/draft-polli-resource-digests-http
[3] https://tools.ietf.org/html/rfc7231#section-3.1.2.1
[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
[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
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[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
Appendix A. Change Log
RFC EDITOR PLEASE DELETE THIS SECTION.
Appendix B. Acknowledgements
The vast majority of this document is inherited from [RFC3230], so
thanks to J. Mogul and A. Van Hoff for their great work. The
original idea of refreshing this document arose from an interesting
discussion with M. Nottingham, J. Yasskin and M. Thomson when
reviewing the MICE content coding.
Appendix C. FAQ
1. Why remove all references to content-md5?
Those were unnecessary to understanding and using this spec.
2. Why remove references to instance manipulation?
Those were unnecessary for correctly using and applying the spec.
An example with Range Request is more than enough. This doc uses
the term "partial representation" which should group all those
cases.
3. How to use "Digest" with "PATCH" method?
The PATCH verb brings some complexities (eg. about representation
metadata headers, patch document format, ...),
* PATCH entity-headers apply to the patch document and MUST NOT
be applied to the target resource, see [RFC5789], Section 2.
* servers shouldn't assume PATCH semantics for generic media
types like "application/json" but should instead use a proper
content-type, eg [RFC7396]
* a "200 OK" response to a PATCH request would contain the
digest of the patched item, and the etag of the new object.
This behavior - tighly coupled to the application logic -
gives the client low probability of guessing the actual
outcome of this operation (eg. concurrent changes, ...)
4. Why remove references to delta-encoding?
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Unnecessary for a correct implementation of this spec. The
revised spec can be nicely adapted to "delta encoding", but all
the references here to delta encoding don't add anything to this
RFC. Another job would be to refresh delta encoding.
5. Why remove references to Digest Authentication?
This RFC seems to me completely unrelated to Digest
Authentication but for the word "Digest".
6. What changes in "Want-Digest"?
We allow to use the "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?
This RFC updates [RFC5843] which is still delegated for all
algorithms updates, and adds two more algorithms: ID-SHA-256 and
ID-SHA-512 which allows to send a checksum of a resource
representation with no content codings applied.
Authors' Addresses
Roberto Polli
Email: robipolli@gmail.com
Lucas Pardue
Email: lucaspardue.24.7@gmail.com
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