Internet-Draft | JMAP Blob | October 2021 |
Gondwana | Expires 11 April 2022 | [Page] |
The JMAP base protocol (RFC8620) provides the ability to upload and download arbitrary binary data via HTTP POST 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 data types.¶
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Sometimes JMAP ([RFC8620]) interactions require creating a Blob and then referencing it. In the same way that IMAP Literals ([RFC7888]) 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.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
A blob is a sequence of zero or more octets.¶
The JMAP base spec [RFC8620] defines the Blob/copy
method, which
is unchanged by this specfication.¶
This is a standard JMAP set
method.¶
Properties:¶
Exactly one of:¶
Also:¶
Result is:¶
Any other properties identical to those that would be returned in the JSON response of the RFC8620 upload endpoint.¶
SetObject:¶
Any one of¶
OR a blobId source:¶
It is not possible to update a Blob, so any update will result
in a notUpdated
response.¶
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" ]¶
A standard JMAP get with two additional parameters:¶
Properties:¶
Any of¶
If not given, returns data
and size
.¶
The size value is always the number of octets in the blob, regardless of offset and length, while all the data fields contain just the octets within the selected range. If there are no octets within the selected range, the data fields will be the empty string.¶
Example (a blob containing the string "The quick brown fox jumped over the lazy dog!")¶
Method Call: [ "Blob/get", { "accountId" : "account1", "ids" : [ "G6ec94756e3e046be78fcb33953b85b944e70673e", "not-a-blob" ], "properties" : [ "data:asText", "data:asBase64", "data:asHex", "size" ], "offset" : 4, "length" : 9 }, "R1" ] Response: [ "Blob/get", { "accountId" : "account1", "list" : [ { "id" : "G6ec94756e3e046be78fcb33953b85b944e70673e", "data:asText" : "quick bro", "data:asBase64" : "cXVpY2sgYnJvCg==", "data:asHex" : "717569636b2062726f", "size" : 46 } ], "notFound" : [ "not-a-blob" ] }, "R1" ]¶
Given a list of blobIds, this method does a reverse lookup in each of the provided type names to find the list of Ids within that data type 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¶
The id of the account used for the call.¶
A list of type names from the "JMAP Data Types" registry. Only names for which "Can Reference Blobs" is true may be specified, and the capability which defines each type must also be used by the overall JMAP request in which this method is called.¶
If a type name is not known by the server, or the associated capability has not been requested, then the server returns an "unknownDataType" error.¶
A list of blobId values to be looked for.¶
Response¶
A list of BlobInfo objects.¶
BlobInfo Object¶
The Blob Identifier.¶
A map from type name to list of Ids of that data type (e.g. the name "Email" maps to a list of emailIds)¶
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 type name, as it may not be able to know if other data types do reference that blob.¶
e.g.¶
[ "Blob/lookup", { "types": ["Mailbox", "Thread", "Email"], "ids": ["Gd2f81008cf07d2425418f7f02a3ca63a8bc82003", "not-a-blob"] }, "R1" ]¶
Response:¶
[ "Blob/lookup", { "list": [ { "id": "Gd2f81008cf07d2425418f7f02a3ca63a8bc82003", "types": { "Mailbox": ["M54e97373", Mcbe6b662"], "Thread": ["T1530616e"], "Email": ["E16e70a73eb4", "E84b0930cf16"] } } ], "notFound": ["not-a-blob"] }, "R1"]¶
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 server might sometimes return all names empty rather than putting a blobId in the notFound response to a Blob/get, then the server SHOULD always return the same type of response, regardless of whether a blob exists but the user can't access it, or doesn't exist at all. This avoids leaking information about the existence of the blob.¶
The server MUST NOT trust that the data given to a Blob/set is a well formed instance of the specified media type, and if the server attempts to parse the given blob, only hardened parsers designed to deal with arbitrary untrusted data should be used. The server SHOULD NOT reject data on the grounds that it is not a valid specimen of the stated type.¶
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¶
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.¶
IANA is requested to create a new registry "JMAP Data Types" with the initial content:¶
Type Name | Can Reference Blobs | Can use for State Change | Capability | Reference |
---|---|---|---|---|
Core | No | No | urn:ietf:params:jmap:core | [RFC8620] |
PushSubscription | No | No | urn:ietf:params:jmap:core | [RFC8620] |
Mailbox | Yes | Yes | urn:ietf:params:jmap:mail | [RFC8621] |
Thread | Yes | Yes | urn:ietf:params:jmap:mail | [RFC8621] |
Yes | Yes | urn:ietf:params:jmap:mail | [RFC8621] | |
EmailDelivery | No | Yes | urn:ietf:params:jmap:mail | [RFC8621] |
SearchSnippet | No | No | urn:ietf:params:jmap:mail | [RFC8621] |
Identity | No | Yes | urn:ietf:params:jmap:submission | [RFC8621] |
EmailSubmission | No | Yes | urn:ietf:params:jmap:submission | [RFC8621] |
VacationResponse | No | Yes | urn:ietf:params:jmap:vacationresponse | [RFC8621] |
MDN | No | No | urn:ietf:params:jmap:mdn | [RFC9007] |
EDITOR: please remove this section before publication.¶
The source of this document exists on github at: https://github.com/brong/draft-gondwana-jmap-blob/¶
draft-ieft-jmap-blob-02:¶
draft-ieft-jmap-blob-01:¶
draft-ieft-jmap-blob-00:¶
draft-gondwana-jmap-blob-02¶
draft-gondwana-jmap-blob-01¶
draft-gondwana-jmap-blob-00¶
Alexey Melnikov, Ken Murchison, and the JMAP working group at the IETF.¶