blossom/buds/06.md

BUD-06

Upload requirements

draft optional

Defines how clients can verify if the upload can be completed before sending the blob to the server. This mechanism helps prevent unnecessary traffic to other endpoints by rejecting files based on their hash, size, MIME type or other server-specific requirements.

HEAD /upload - Upload requirements

The HEAD /upload endpoint MUST use the Content-Digest, X-Content-Type and X-Content-Length headers sent by client to get the SHA-256 hash, MIME type and size of the blob that will be uploaded, returning a HTTP status code and a custom header X-Upload-Message to indicate some human readable message about the upload requirements.

Headers

• Content-Digest: A string formatted as sha-256=:<base64digest>:, where <base64digest> is the base64-encoded SHA-256 hash of the blob.
• X-Content-Length: An integer that represents the blob size in bytes.
• X-Content-Type: A string that specifies the fblobile's MIME type, like application/pdf or image/png.
• X-Upload-Message: A human readable message that explains the reason why the upload cannot proceed.

Examples

Example request from the client:

X-Content-Type: application/pdf
X-Content-Length: 184292
Content-Digest: SHA-256=:88a74d0b866c8ba79251a11fe5ac807839226870e77355f02eaf68b156522576:

Example response from the server if the upload can be done:

HTTP/1.1 200 OK

If the upload cannot proceed, the server MUST return an appropriate HTTP status code and a custom header X-Upload-Message with a human readable error message.

Some examples of error messages:

HTTP/1.1 400 Bad Request
X-Upload-Message: Invalid Content-Digest header format. Expected format: sha-256=:<hash>:

HTTP/1.1 413 Content Too Large
X-Upload-Message: File too large. Max allowed size is 100MB

HTTP/1.1 415 Unsupported Media Type
X-Upload-Message: Unsupported file type.