BUD06 - Upload requirements

README.md

@@ -16,9 +16,10 @@ Blossom Servers expose four endpoints for managing blobs
 
 - `GET /<sha256>` (optional file `.ext`) [BUD-01](./buds/01.md#get-sha256---get-blob)
 - `HEAD /<sha256>` (optional file `.ext`) [BUD-01](./buds/01.md#head-sha256---has-blob)
-- `PUT /upload` [BUD-2](./buds/02.md#put-upload---upload-blob)
+- `PUT /upload` [BUD-02](./buds/02.md#put-upload---upload-blob)
   - `Authentication`: Signed [nostr event](./buds/02.md#upload-authorization-required)
   - Return a blob descriptor
+- `HEAD /upload` [BUD-06](./buds/06.md#head-upload---upload-requirements)
 - `GET /list/<pubkey>` [BUD-02](./buds/02.md#get-listpubkey---list-blobs)
   - Returns an array of blob descriptors
   - `Authentication` _(optional)_: Signed [nostr event](./buds/02.md#list-authorization-optional)

buds/06.md

@@ -0,0 +1,55 @@
+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:
+
+```http
+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
+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
+HTTP/1.1 400 Bad Request
+X-Upload-Message: Invalid Content-Digest header format. Expected format: sha-256=:<hash>:
+```
+
+```http
+HTTP/1.1 413 Content Too Large
+X-Upload-Message: File too large. Max allowed size is 100MB
+```
+
+```http
+HTTP/1.1 415 Unsupported Media Type
+X-Upload-Message: Unsupported file type.
+```