blossom/buds/01.md

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# BUD-01
## Server requirements and blob retrieval
`draft` `mandatory`
_All pubkeys MUST be in hex format_
## Cross origin headers
Servers MUST set the `Access-Control-Allow-Origin: *` header on all responses to ensure compatibility with applications hosted on other domains.
For [preflight](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#preflighted_requests) (`OPTIONS`) requests,
servers MUST also set, at minimum, the `Access-Control-Allow-Headers: Authorization, *` and `Access-Control-Allow-Methods: GET, PUT,
DELETE` headers.
The header `Access-Control-Max-Age: 86400` MAY be set to cache the results of a preflight request for 24 hours.
## Authorization events
Authorization events are used to identify the users to the server
Authorization events must be generic and must NOT be scoped to specific servers. This allows pubkeys to sign a single event and interact the same way with multiple servers.
Events MUST be kind `24242` and have a `t` tag with a verb of `get`, `upload`, `list`, or `delete`
Events MUST have the `content` set to a human readable string explaining to the user what the events inteded use is. For example `Upload Blob`, `Delete dog-picture.png`, `List Images`, etc
All events MUST have a [NIP-40](https://github.com/nostr-protocol/nips/blob/master/40.md) `expiration` tag set to a unix timestamp at which the event should be considered expired.
Authorization events MAY have multiple `x` tags for endpoints that require a sha256 hash.
Example event:
```json
{
"id": "bb653c815da18c089f3124b41c4b5ec072a40b87ca0f50bbbc6ecde9aca442eb",
"pubkey": "b53185b9f27962ebdf76b8a9b0a84cd8b27f9f3d4abd59f715788a3bf9e7f75e",
"kind": 24242,
"content": "Upload bitcoin.pdf",
"created_at": 1708773959,
"tags": [
["t", "upload"],
// Authorization events MAY have multiple "x" tags
["x", "b1674191a88ec5cdd733e4240a81803105dc412d6c6708d53ab94fc248f4f553"],
["expiration", "1708858680"]
],
"sig": "d0d58c92afb3f4f1925120b99c39cffe77d93e82f488c5f8f482e8f97df75c5357175b5098c338661c37d1074b0a18ab5e75a9df08967bfb200930ec6a76562f"
}
```
Servers must perform the following checks in order to validate the event
1. The `kind` must be `24242`
2. `created_at` must be in the past
3. The `expiration` tag must be set to a Unix timestamp in the future
4. The `t` tag must have a verb matching the intended action of the endpoint
5. Additional checks for specific endpoints. `/upload`, `/delete`, etc
Using the `Authorization` HTTP header, the kind `24242` event MUST be base64 encoded and use the Authorization scheme Nostr
Example HTTP Authorization header:
```
Authorization: Nostr 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
```
## Endpoints
All endpoints MUST be served from the root path (eg. `https://cdn.example.com/upload`, etc). This allows clients to talk to servers interchangeably when uploading or retrieving blobs
## Error Responses
For HTTP `4xx` and `5xx` status codes servers MUST repond with `Content-Type: application/json` and a JSON object containing `message`
The `message` field MUST be human readable and should explain the reason for the error. Optionally servers may include other fields for the client with more information about the error
Example Error response:
```
HTTP/2 401
content-type: application/json; charset=utf-8
content-length: 32
access-control-allow-origin: *
access-control-expose-headers: *
access-control-allow-headers: authorization,*
access-control-allow-methods: get, put, delete
{"message":"Missing Auth event"}
```
## GET /sha256 - Get Blob
The `GET /<sha256>` endpoint MUST return the contents of the blob with the `Content-Type` header set to the appropriate MIME type
The endpoint MUST accept an optional file extension in the URL. ie. `.pdf`, `.png`, etc
If the endpoints returns a 301 or 302 redirect it MUST redirect to a URL containing the same sha256 hash as requested blob.
This ensures that if a user was to copy or reuse the redirect URL it would still contain the original sha256 hash
### Get Authorization (optional)
The server may optionally require authorization when retrieving blobs from the `GET /<sha256>` endpoint
In this case the server MUST perform additional checks on the authorization event
1. A `t` tag MUST be present and set to `get`
2. The event MUST contain either a `server` tag containing the full URL to the server or MUST contain at least one `x` tag matching the sha256 hash of the blob being retrieved
If the client did not send an `Authorization` header the server must respond with the appropriate HTTP status code `401` (Unauthorized)
Example event for retrieving a single blob:
```json
{
"id": "06d4842b9d7f8bf72440471704de4efa9ef8f0348e366d097405573994f66294",
"pubkey": "ec0d11351457798907a3900fe465bfdc3b081be6efeb3d68c4d67774c0bc1f9a",
"kind": 24242,
"content": "Get bitcoin.pdf",
"created_at": 1708771927,
"tags": [
["t", "get"],
["expiration", "1708857340"],
["x", "b1674191a88ec5cdd733e4240a81803105dc412d6c6708d53ab94fc248f4f553"]
],
"sig": "22ecb5116ba143e4c3d6dc4b53d549aed6970ec455f6d25d145e0ad1fd7c0e26c465b2e92d5fdf699c7050fa43e6a41f087ef167208d4f06425f61548168fd7f"
}
```
Example event for retrieving multiple blobs from single server:
```json
{
"id": "d9484f18533d5e36f000f902a45b15a7eecf5fbfcb046789756d57ea87115dc5",
"pubkey": "b5f07faa8d3529f03bd898a23dfb3257bab8d8f5490777c46076ff9647e205dc",
"kind": 24242,
"content": "Get blobs from example.com",
"created_at": 1708771927,
"tags": [
["t", "get"],
["expiration", "1708857340"],
["server", "https://cdn.example.com/"]
],
"sig": "e402ade78e1714d40cd6bd3091bc5f4ada8e904e90301b5a2b9b5f0b6e95ce908d4f22b15e9fb86f8268a2131f8adbb3d1f0e7e7afd1ab0f4f08acb15822a999"
}
```
## HEAD /sha256 - Has Blob
The `HEAD /<sha256>` endpoint MUST respond with either a `200` or `404` status code
The endpoint MUST accept an optional file extension in the URL similar to the `GET /<sha256>` endpoint. ie. `.pdf`, `.png`, etc