| HTTP Working Group | R. Polli |
| Internet-Draft | Team Digitale, Italian Government |
| Intended status: Standards Track | L. Pardue |
| Expires: September 10, 2020 | Cloudflare |
| March 9, 2020 |
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 RFC 3230. It replaces the term “instance” with “representation”, which makes it consistent with the HTTP Semantic and Context defined in RFC 7231.¶
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 athttps://lists.w3.org/Archives/Public/ietf-http-wg/.¶
The source code and issues list for this draft can be found athttps://github.com/httpwg/http-extensions.¶
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is athttps://datatracker.ietf.org/drafts/current/.¶
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as “work in progress”.¶
This Internet-Draft will expire on September 10, 2020.¶
Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.¶
The core specification of HTTP does not define a means to protect the integrity of resources. When HTTP messages are transferred between endpoints, the protocol might choose to make use of features of the lower layer in order to provide some integrity protection; for instance TCP checksums or TLS records[RFC2818].¶
However, there are cases where relying on this alone is insufficient. An HTTP-level integrity mechanism that operates independent of transfer can be used to detect programming errors and/or corruption of data at rest, be used across multiple hops in order to provide end-to-end integrity guarantees, aid fault diagnosis across hops and system boundaries, and can be used to validate integrity when reconstructing a resource fetched using different HTTP connections.¶
This document defines a mechanism that acts on HTTP representation-data. It can be combined with other mechanisms that protect representation-metadata, such as digital signatures, in order to protect the desired parts of an HTTP exchange in whole or in part.¶
The Content-MD5 header field was originally introduced to provide integrity, but HTTP/1.1 ([RFC7231],Appendix B) obsoleted it:¶
The concept ofselected representation defined in[RFC7231] made[RFC3230] definitions inconsistent with the current standard. A refresh was then required.¶
This document updates theDigest andWant-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[RFC7233]).¶
Changes are semantically compatible with existing implementations and better cover both the request and response cases.¶
The value ofDigest is calculated on selected representation, which is tied to the value contained in anyContent-Encoding orContent-Type header fields. Therefore, a given resource may have multiple different digest values.¶
To allow both parties to exchange a Digest of a representation withno content codings two more algorithms are added (ID-SHA-256 andID-SHA-512).¶
The goals of this proposal are:¶
The goals do not include:¶
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.¶
This document uses the Augmented BNF defined in[RFC5234] and updated by[RFC7405] along with the “#rule” extension defined inSection 7 of[RFC7230].¶
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].¶
The definition “validator” in this document is to be interpreted as described inSection 7.2 of[RFC7231].¶
The representation digest is an integrity mechanism for HTTP resources which uses a checksum that is calculated independently of the payload body and message body. It uses the representation data (see[RFC7231]), that can be fully or partially contained in the message body, or not contained at all:¶
representation-data := Content-Encoding( Content-Type( bits ) )
This takes into account the effect of the HTTP semantics on the messages; for example the payload body can be affected by Range Requests or methods such as HEAD, while the message body is dependent on transfer codings and other transformations:Appendix A contains several examples to help illustrate those effects.¶
A representation digest consists of the value of a checksum computed on the entire selectedrepresentation data of a resource together with an indication of the algorithm used (and any parameters)¶
representation-data-digest = digest-algorithm "=" <encoded digest output>
The checksum is computed using one of thedigest-algorithms listed inSection 5 and then encoded in the associated format.¶
The example below shows thesha-256 digest-algorithm which uses base64 encoding.¶
sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
The Digest header field contains a list of one or more representation digest values as defined inSection 2. It can be used in both request and response.¶
Digest = "Digest" ":" OWS 1#representation-data-digest
The resource is specified by the effective request URI and anyvalidator contained in the message.¶
The relationship between Content-Location (see[RFC7231]Section 3.1.4.2) and Digest is demonstrated inSection 9.7. A comprehensive set of examples showing the impacts of representation metadata, payload transformations and HTTP methods on digest is provided inSection 9 andSection 10.¶
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. This allows the recipient to choose which digest-algorithm(s) to use for validation instead of verifying every received representation-data-digest.¶
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.¶
Two examples of its use are¶
Digest: id-sha-512=WZDPaVn/7XgHaAy8pmojAkGWoRx2UFChF41A2svX+TaPm AbwAgBWnrIiYllu7BNNyealdVLvRwE\nmTHWXvJwew== Digest: sha-256=4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=, id-sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
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" ":" OWS 1#want-digest-value want-digest-value = digest-algorithm [ ";" "q" "=" qvalue] qvalue = ( "0" [ "." 0*1DIGIT ] ) / ( "1" [ "." 0*1( "0" ) ] )
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.¶
Two examples of its use are¶
Want-Digest: sha-256 Want-Digest: SHA-512;q=0.3, sha-256;q=1, md5;q=0
Digest algorithm values are used to indicate a specific digest computation. For some algorithms, one or more parameters can 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 tokens listed below.¶
Some algorithms, although registered, have since been found vulnerable: the MD5 algorithm MUST NOT be used due to collision attacks[CMU-836068] and the SHA algorithm is NOT RECOMMENDED due to collision attacks[IACR-2019-459].¶
To allow sender and recipient to provide a checksum which is independent fromContent-Encoding, the following additional algorithms are defined:¶
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.¶
POST and PATCH requests can appear to convey partial representations but are semantically acting on resources. The enclosed representation, including its metadata refers to that action.¶
In these requests the representation digest MUST be computed on the representation-data of that action. This is the only possible choice because representation digest requires complete representation metadata (seeSection 2).¶
In responses,¶
The latter case might be done according to the HTTP semantics of the given method, for example using theContent-Location header field. In contrast, theLocation header field does not affectDigest because it is not representation metadata.¶
In PATCH requests the representation digest MUST be computed on the patch document because the representation metadata refers to the patch document and not to the target resource (seeSection 2 of[RFC5789]).¶
In PATCH responses the representation digest MUST be computed on the selected representation of the patched resource.¶
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 the patch document.¶
Subresource Integrity[SRI] is an integrity mechanism that shares some similarities to the present document’s mechanism. However, there are differences in motivating factors, threat model and specification of integrity digest generation, signalling and validation.¶
SRI allows a first-party authority to declare an integrity assertion on a resource served by a first or third party authority. This is done via theintegrity attribute that can be added toscript orlink HTML elements. Therefore, the integrity assertion is always made out-of-band to the resource fetch. In contrast, theDigest header field is supplied in-band alongside the selected representation, meaning that an authority can only declare an integrity assertion for itself. Methods to improve the security properties of representation digests are presented inSection 11. This contrast is interesting because on one hand self-assertion is less likely to be affected by coordination problems such as the first-party holding stale information about the third party, but on the other hand the self-assertion is only as trustworthy as the authority that provided it.¶
The SRIintegrity attribute contains a cryptographic hash algorithm and digest value which is similar torepresentation-data-digest (seeSection 2). The major differences are in serialization format.¶
The SRI digest value is calculated over the identity encoding of the resource, not the selected representation (as specified forrepresentation-data-digest in this document). Section 3.4.5 of[SRI] describes the benefit of the identity approach - the SRIintegrity attribute can contain multiple algorithm-value pairs where each applies to a different identity encoded payload. This allows for protection of distinct resources sharing a URL. However, this is a contrast to the design of representation digests, where multipleDigest field-values all protect the same representation.¶
SRI does not specify handling of partial representation data (e.g. Range requests). In contrast, this document specifies handling in terms that are fully compatible with core HTTP concepts (an example is provided inSection 9.3).¶
SRI specifies strong requirements on the selection of algorithm for generation and validation of digests. In contrast, the requirements in this document are weaker.¶
SRI defines no method for a client to declare an integrity assertion on resources it transfers to a server. In contrast, theDigest header field can appear on requests.¶
The SRI and Representation Digest mechanisms are different and complementary but one is not capable of replacing the other because they have different threat, security and implementation properties.¶
A user agent that supports both mechanisms is expected to apply the rules specified for each but since the two mechanisms are independent, the ordering is not important. However, a user agent supporting both could benefit from performing representation digest validation first because it does not always require a conversion into identity encoding.¶
There is a chance that a user agent supporting both mechanisms may find one validates successfully while the other fails. This document specifies no requirements or guidance for user agents that experience such cases.¶
The following examples demonstrate interactions where a server responds with aDigest header field even though the client did not solicit one usingWant-Digest.¶
Request:¶
GET /items/123
Response:¶
HTTP/1.1 200 OKContent-Type: application/jsonContent-Encoding: identityDigest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE={"hello": "world"}As there is no content coding applied, thesha-256 and theid-sha-256 digest-values are the same.¶
Request:¶
HEAD /items/123
Response:¶
HTTP/1.1 200 OKContent-Type: application/jsonContent-Encoding: identityDigest: id-sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
Request:¶
GET /items/123Range: bytes=1-7
Response:¶
HTTP/1.1 206 Partial ContentContent-Type: application/jsonContent-Encoding: identityContent-Range: bytes 1-7/18Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE="hello"
The request contains aDigest header calculated on the enclosed representation.¶
It also includes anAccept-Encoding: br header field that advertises the client supports brotli encoding.¶
The response includes aContent-Encoding: br that indicates the selected representation is brotli encoded. TheDigest field-value is therefore different compared to the request.¶
The response body is displayed as a base64-encoded string because it contains non-printable characters.¶
Request:¶
PUT /items/123Content-Type: application/jsonContent-Encoding: identityAccept-Encoding: brDigest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE={"hello": "world"}Response:¶
Content-Type: application/jsonContent-Encoding: brDigest: sha-256=4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=iwiAeyJoZWxsbyI6ICJ3b3JsZCJ9Aw==
RequestDigest value is calculated on the enclosed payload. ResponseDigest value depends on the representation metadata header fields, includingContent-Encoding: br even when the response does not contain a payload body.¶
Request:¶
PUT /items/123Content-Type: application/jsonContent-Encoding: identityContent-Length: 18Accept-Encoding: brDigest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE={"hello": "world"}Response:¶
HTTP/1.1 204 No ContentContent-Type: application/jsonContent-Encoding: brDigest: sha-256=4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=
The response contains two digest values:¶
As the response body contains non-printable characters, it is displayed as a base64-encoded string.¶
Request:¶
PUT /items/123 HTTP/1.1Content-Type: application/jsonContent-Encoding: identityAccept-Encoding: brDigest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE={"hello": "world"}Response:¶
HTTP/1.1 200 OKContent-Type: application/jsonContent-Encoding: brDigest: sha-256=4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=, id-sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=iwiAeyJoZWxsbyI6ICJ3b3JsZCJ9Aw==
The representation enclosed in the response refers to the resource identified byContent-Location (see[RFC7231]Section 3.1.4.2 and Section 3.1.4.1 point 4).¶
Digest is thus computed on the enclosed representation.¶
Request:¶
POST /books HTTP/1.1Content-Type: application/jsonAccept: application/jsonAccept-Encoding: identityDigest: sha-256=bWopGGNiZtbVgHsG+I4knzfEJpmmmQHf7RHDXA3o1hQ={"title": "New Title"}Response¶
HTTP/1.1 201 CreatedContent-Type: application/jsonDigest: id-sha-256=BZlF2v0IzjuxN01RQ97EUXriaNNLhtI8Chx8Eq+XYSc=Content-Location: /books/123{"id": "123", "title": "New Title"}Note that a204 No Content response without a payload body but with the sameDigest field-value would have been legitimate too.¶
The representation enclosed in the response describes the status of the request, soDigest is computed on that enclosed representation.¶
ResponseDigest has no explicit relation with the resource referenced byLocation.¶
Request:¶
POST /books HTTP/1.1Content-Type: application/jsonAccept: application/jsonAccept-Encoding: identityDigest: sha-256=bWopGGNiZtbVgHsG+I4knzfEJpmmmQHf7RHDXA3o1hQ=Location: /books/123{"title": "New Title"}Response¶
HTTP/1.1 201 CreatedContent-Type: application/jsonDigest: id-sha-256=0o/WKwSfnmIoSlop2LV/ISaBDth05IeW27zzNMUh5l8=Location: /books/123{ "status": "created", "id": "123", "ts": 1569327729, "instance": "/books/123"}This case is analogous to a POST request where the target resource reflects the effective request URI.¶
Digest is calculated on the enclosed payload, which corresponds to the patch document.¶
The responseDigest is computed on the complete representation of the patched resource.¶
Request:¶
PATCH /books/123 HTTP/1.1Content-Type: application/merge-patch+jsonAccept: application/jsonAccept-Encoding: identityDigest: sha-256=bWopGGNiZtbVgHsG+I4knzfEJpmmmQHf7RHDXA3o1hQ={"title": "New Title"}Response:¶
HTTP/1.1 200 OKContent-Type: application/jsonDigest: id-sha-256=BZlF2v0IzjuxN01RQ97EUXriaNNLhtI8Chx8Eq+XYSc={"id": "123", "title": "New Title"}Note that a204 No Content response without a payload body but with the sameDigest field-value would have been legitimate too.¶
In error responses, the representation-data does not necessarily refer to the target resource. Instead it refers to the representation of the error.¶
In the following example a client attempts to patch the resource located at /books/123. However, the resource does not exist and the server generates a 404 response with a body that describes the error in accordance with[RFC7807].¶
The digest of the response is computed on this enclosed representation.¶
Request:¶
PATCH /books/123 HTTP/1.1Content-Type: application/merge-patch+jsonAccept: application/jsonAccept-Encoding: identityDigest: sha-256=bWopGGNiZtbVgHsG+I4knzfEJpmmmQHf7RHDXA3o1hQ={"title": "New Title"}Response:¶
HTTP/1.1 404 Not FoundContent-Type: application/problem+jsonDigest: sha-256=UJSojgEzqUe4UoHzmNl5d2xkmrW3BOdmvsvWu1uFeu0={ "title": "Not Found", "detail": "Cannot PATCH a non-existent resource", "status": 404}The following examples demonstrate interactions where a client solicits aDigest usingWant-Digest.¶
The client requests a digest, preferring sha. The server is free to reply with sha-256 anyway.¶
Request:¶
GET /items/123 HTTP/1.1Want-Digest: sha-256;q=0.3, sha;q=1
Response:¶
HTTP/1.1 200 OKContent-Type: application/jsonContent-Encoding: identityDigest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE={"hello": "world"}The client requests a sha digest only. The server is currently free to reply with a Digest containing an unsupported algorithm.¶
Request:¶
GET /items/123Want-Digest: sha;q=1
Response:¶
HTTP/1.1 200 OKContent-Type: application/jsonContent-Encoding: identityDigest: id-sha-512=WZDPaVn/7XgHaAy8pmojAkGWoRx2UFChF41A2svX+TaPm +AbwAgBWnrIiYllu7BNNyealdVLvRwE\nmTHWXvJwew=={"hello": "world"}The client requests a sha Digest, the server advises for sha-256 and sha-512¶
Request:¶
GET /items/123Want-Digest: sha;q=1
Response:¶
HTTP/1.1 400 Bad RequestWant-Digest: sha-256, sha-512
This document specifies a data integrity mechanism that protects HTTPrepresentation data, but not HTTPrepresentation metadata header fields, from certain kinds of accidental corruption.¶
Digest is not intended as general protection against malicious tampering with HTTP messages, this can be achieved by combining it with other approaches such as transport-layer security or digital signatures.¶
Cryptographic algorithms 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, so MD5 MUST NOT be used and SHA-1 is NOT RECOMMENDED for use withDigest.¶
Digest alone does not provide end-to-end integrity of HTTP messages over multiple hops, as it just covers therepresentation data and not therepresentation metadata.¶
Besides, it allows to protectrepresentation 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.¶
When a state-changing method returns theContent-Location header field, the enclosed representation refers to the resource identified by its value andDigest is computed accordingly.¶
Digital signatures are widely used together with checksums to provide the certain identification of the origin of a message[NIST800-32]. Such signatures can protect one or more header fields and there are additional considerations whenDigest is included in this set.¶
Since theDigest header field is a hash of a resource representation, it explicitly depends on therepresentation metadata (eg. the values ofContent-Type,Content-Encoding etc). A signature that protectsDigest but not otherrepresentation metadata can expose the communication to tampering. For example, an actor could manipulate theContent-Type field-value and cause a digest validation failure at the recipient, preventing the application from accessing the representation. Such an attack consumes the resources of both endpoints. See alsoSection 11.5.¶
Digest SHOULD always be used over a connection which provides integrity at the transport layer that protects HTTP header fields.¶
ADigest header field using NOT RECOMMENDED digest-algorithms SHOULD NOT be used in signatures.¶
…¶
…¶
This memo sets this spec to be the establishing document for theHTTP Digest Algorithm Values¶
This memo adds the field “Status” to theHTTP Digest Algorithm Values registry. The allowed values for the “Status” fields are described below.¶
This memo updates the “MD5” digest algorithm in theHTTP Digest Algorithm Values registry:¶
This memo updates the “CRC32c” digest algorithm in theHTTP Digest Algorithm Values registry:¶
This memo updates the “SHA” digest algorithm in theHTTP Digest Algorithm Values registry:¶
This memo updates the “ADLER32” digest algorithm in theHTTP Digest Algorithm Values registry:¶
This memo registers the “ID-SHA-256” digest algorithm in theHTTP Digest Algorithm Values registry:¶
This memo registers the “ID-SHA-512” digest algorithm in theHTTP Digest Algorithm Values registry:¶
The status of “MD5” has been updated to “deprecated”, and its description states that this algorithm MUST NOT be used.¶
The status of “SHA” has been updated to “obsoleted”, and its description states that this algorithm is NOT RECOMMENDED.¶
The status for “CRC32C” has been updated to “standard”.¶
The “ID-SHA-256” and “ID-SHA-512” algorithms have been added to the registry.¶
This section registers theWant-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¶
This section registers theDigest header field in the “Permanent Message Header Field Names” registry ([RFC3864]).¶
Header field name:Digest¶
Applicable protocol: http¶
Status: standard¶
Author/Change controller: IETF¶
The following examples show how representation metadata, payload transformations and method impacts on the message and payload body. When the payload body contains non-printable characters (eg. when it is compressed) it is shown as base64-encoded string.¶
Here is a gzip-compressed json object¶
Request:¶
PUT /entries/1234 HTTP/1.1Content-Type: application/jsonContent-Encoding: gzipH4sIAItWyFwC/6tWSlSyUlAypANQqgUAREcqfG0AAAA=
Now the same payload body conveys a malformed json object.¶
Request:¶
PUT /entries/1234 HTTP/1.1Content-Type: application/jsonH4sIAItWyFwC/6tWSlSyUlAypANQqgUAREcqfG0AAAA=
A Range-Request alters the payload body, conveying a partial representation.¶
Request:¶
GET /entries/1234 HTTP/1.1Range: bytes=1-7
Response:¶
HTTP/1.1 206 Partial ContentContent-Encoding: gzipContent-Type: application/jsonContent-Range: bytes 1-7/18iwgAla3RXA==
Now the method too alters the payload body.¶
Request:¶
HEAD /entries/1234 HTTP/1.1Accept: application/jsonAccept-Encoding: gzip
Response:¶
HTTP/1.1 200 OKContent-Type: application/jsonContent-Encoding: gzip
Finally the semantics of an HTTP response might decouple the effective request URI from the enclosed representation. In the example response below, theContent-Location header field indicates that the enclosed representation refers to the resource available at/authors/123.¶
Request:¶
POST /authors/ HTTP/1.1Accept: application/jsonContent-Type: application/json{"author": "Camilleri"}Response:¶
HTTP/1.1 201 CreatedContent-Type: application/jsonContent-Location: /authors/123Location: /authors/123{"id": "123", "author": "Camilleri"}RFC Editor: Please remove this section before publication.¶
How can I generate and validate the Digest values shown in the examples throughout this document?¶
The following python3 code can be used to generate digests for json objects using SHA algorithms for a range of encodings. Note that these are formatted as base64. This function could be adapted to other algorithms and should take into account their specific formatting rules.¶
import base64, json, hashlib, brotlidef digest(item, encoding=lambda x: x, algorithm=hashlib.sha256): json_bytes = json.dumps(item).encode() content_encoded = encoding(json_bytes) checksum_bytes = algorithm(content_encoded).digest() return base64.encodebytes(checksum_bytes).strip()item = {"hello": "world"}print("Encoding | digest-algorithm | digest-value")print("Identity | sha256 |", digest(item))# Encoding | digest-algorithm | digest-value# Identity | sha256 | 4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=print("Encoding | digest-algorithm | digest-value")print("Brotli | sha256 |", digest(item, encoding=brotli.compress))# Encoding | digest-algorithm | digest-value# Brotli , sha256 4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=print("Encoding | digest-algorithm | digest-value")print("Identity | sha512 |", digest(item, algorithm=hashlib.sha512))# Encoding | digest-algorithm | digest-value# Identity | sha512 | b'WZDPaVn/7XgHaAy8pmojAkGWoRx2UFChF41A2svX+TaPm+AbwAgBWnrIiYllu7BNNyealdVLvRwE\nmTHWXvJwew==\n'RFC Editor: Please remove this section before publication.¶