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Applications JMAP jmap The JMAP base protocol (RFC8620) provides the ability to upload and download arbitrary binary data via HTTP PUT and GET on defined endpoint. This binary data is called a "Blob". This extension adds additional ways to create and access Blobs, by making inline method calls within a standard JMAP request. This extension also adds a reverse lookup mechanism to discover where blobs are referenced within other datatypes.

Introduction Sometimes JMAP () interactions require creating a Blob and then referencing it. In the same way that IMAP Literals () were extended to reduce roundtrips for simple data, embedding simple small blobs into the JMAP method stream can reduce roundtrips. Likewise, when fetching an object, it can be useful to also fetch the raw content of that object without a separate roundtrip. Where JMAP is being proxied through a system which applies additional access restrictions, it can be useful to be able to see where a blob is referenced in order to decide whether to allow it to be downloaded.

Conventions Used In This Document 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 when, and only when, they appear in all capitals, as shown here.

Blobs A blob is a sequence of zero or more octets. The JMAP base spec defines the Blob/copy method, which is unchanged by this specfication.

Blob/set This is a standard JMAP set method.

create Properties: Any one of:

• data:asText: String|null
• data:asBase64: String|null
• data:asHex: String|null
• catenate: [SetObject] list of octet sources in order

Also:

• type: String|null

Result is:

• id: Id the blobId
• type: String|null as given in the creation (if any); or detected from content; or null
• size: UnsignedInt as per RFC8620 - the size of the file in Octets

Any other properties identical to those that would be returned in the JSON response of the RFC8620 upload endpoint. SetObject: Any one of

• data:asText: String|null
• data:asBase64: String|null
• data:asHex: String|null

OR a blobId source:

• blobId: Id
• offset: UnsignedInt|null
• length: UnsignedInt|null

update It is not possible to update a Blob, so any update will result in a notUpdated response.

destroy If an uploaded Blob is not referenced by any persistent object, the server SHOULD destroy the object. Some systems use a content-based ID for blobs, so the server MAY respond destroyed and yet that blobId still exist with the same content. Example: Method Call: [ "Blob/set", { "accountId" : "account1", "create" : { "1": { "data:asBase64": "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKA AAAA1BMVEX/AAAZ4gk3AAAAAXRSTlN/gFy0ywAAAApJRE FUeJxjYgAAAAYAAzY3fKgAAAAASUVORK5CYII=", "type" : "image/png" }, }, }, "R1" ] Response: [ "Blob/set", { "accountId" : "account1", "created" : { "1": { "id" : "G4c6751edf9dd6903ff54b792e432fba781271beb", "type" : "image/png", "size" : 95 }, }, }, "R1" ]

Blob/get A standard JMAP get. Properties: Any of

• data:asText
• data:asBase64
• data:asHex
• data selects data:asText if the content is UTF-8, or data:asBase64
• size

If not given, returns data and size. QUESTION: do we want to add range operators?

• offset: UnsignedInt|null
• length: UnsignedInt|null

Returns that range of octets (not characters!) from the blob. Alternative possible syntax - ranges within the properties, e.g: data:asText:0:3000

Blob/lookup Given a list of blobIds, this method does a reverse lookup in each of the provided datatypes to find the list of Ids within that datatype which reference the provided blob. The definition of reference is somewhat loosely defined, but roughly means "you could discover this blobId by looking inside this object", for example if a Mailbox contains an Email which references the blobId, then it references that blobId. Likewise for a Thread. Parameters

• accountId: "Id"

The id of the account used for the call.

• datatypes: [String]

A list of datatype names from the "JMAP Datatypes" registry for which "Can Reference Blobs" is "Yes". The capability which defines each type must also be requested. If a datatype is not known by the server or the associated capability has not been included then the server returns an "unknownDataType" error.

• ids: [Id]

A list of blobId values to be looked for. Response

• list: [BlobInfo]

A list of BlobInfo objects. BlobInfo Object

• id: Id

The Blob Identifier.

• datatypes: DataType[Id List]

A map from datatype to list of Ids of that datatype (e.g. the datatype "Email" maps to a list of emailIds) e.g. [ "Blob/lookup", { "datatypes": ["Mailbox", "Thread", "Email"], "ids": ["Gd2f81008cf07d2425418f7f02a3ca63a8bc82003", "G6f954bcb620f7f50fc8f21426bde3669da3d9067"] }, "R1" ] Response: [ "Blob/lookup", { "list": [ { "id": "Gd2f81008cf07d2425418f7f02a3ca63a8bc82003", "datatypes": { "Mailbox": ["M54e97373", Mcbe6b662"], "Thread": ["T1530616e"], "Email": ["E16e70a73eb4", "E84b0930cf16"] } } ], "notFound": ["G6f954bcb620f7f50fc8f21426bde3669da3d9067"] }, "R1"]

Security considerations TO BE IMPROVED: JSON parsers are not all consistent in handling non-UTF-8 data. JMAP requires that all JSON data be UTF-8 encoded, so servers MUST either return data:asBase64 or isEncodingProblem: true and modify the data to be UTF-8 safe. Servers MUST apply any access controls such that if the authenticated user would be unable to discover the blobId by making queries, then this fact can't be discovered via a Blob/lookup. For example, if an Email exists in a Mailbox which the authenticated user does not have access to see, then that emailId MUST not be returned in a lookup for a blob which is referenced by that email. If a blob is not visible to a user at all, then the server SHOULD return that blobId in the notFound array, however it may also return an empty list for each datatype, as it may not be able to know if other datatypes do reference that blob.

IANA considerations

JMAP Capability registration for "blob" IANA is requested to register the "blob" JMAP Capability as follows: Capability Name: urn:ietf:params:jmap:blob Specification document: this document Intended use: common Change Controller: IETF Security and privacy considerations: this document, Section XXX

JMAP Error Codes Registration for "unknownDataType" IANA is requested to register the "unknownDataType" JMAP Error Code as follows: JMAP Error Code: unknownDataType Intended use: common Change Controller: IETF Reference: this document Description: The server does not recognise this data type, or the capability to enable it was not present.

Creation of "JMAP Datatypes" Registry IANA is requested to create a new registry "JMAP Datatypes" with the initial content:

Datatype name	Can Reference Blobs	Can use for State Change	Capability	Reference
Core	No	No	urn:ietf:params:jmap:core
PushSubscription	No	No	urn:ietf:params:jmap:core
Mailbox	Yes	Yes	urn:ietf:params:jmap:mail
Thread	Yes	Yes	urn:ietf:params:jmap:mail
Email	Yes	Yes	urn:ietf:params:jmap:mail
EmailDelivery	No	Yes	urn:ietf:params:jmap:mail
SearchSnippet	No	No	urn:ietf:params:jmap:mail
Identity	No	Yes	urn:ietf:params:jmap:submission
EmailSubmission	No	Yes	urn:ietf:params:jmap:submission
VacationResponse	No	Yes	urn:ietf:params:jmap:vacationresponse
MDN	No	No	urn:ietf:params:jmap:mdn	[RFC9007]

Acknowledgements TBD

Normative References Informative References