mirror of https://github.com/vacp2p/rfc.git
124 lines
6.2 KiB
Markdown
124 lines
6.2 KiB
Markdown
---
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slug: 8
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title: 8/WAKU-MAIL
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name: Waku Mailserver
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status: stable
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editor: Andrea Maria Piana <andreap@status.im>
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contributors:
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- Adam Babik <adam@status.im>
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- Dean Eigenmann <dean@status.im>
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- Oskar Thorén <oskar@status.im>
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---
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## Abstract
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In this specification, we describe Mailservers. These are nodes responsible for archiving envelopes and delivering them to peers on-demand.
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## Specification
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A node which wants to provide mailserver functionality MUST store envelopes from incoming Messages packets (Waku packet-code `0x01`). The envelopes can be stored in any format, however they MUST be serialized and deserialized to the Waku envelope format.
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A mailserver SHOULD store envelopes for all topics to be generally useful for any peer, however for specific use cases it MAY store envelopes for a subset of topics.
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### Requesting Historic Envelopes
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In order to request historic envelopes, a node MUST send a packet P2P Request (`0x7e`) to a peer providing mailserver functionality. This packet requires one argument which MUST be a Waku envelope.
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In the Waku envelope's payload section, there MUST be RLP-encoded information about the details of the request:
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```abnf
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; UNIX time in seconds; oldest requested envelope's creation time
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lower = 4OCTET
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; UNIX time in seconds; newest requested envelope's creation time
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upper = 4OCTET
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; array of Waku topics encoded in a bloom filter to filter envelopes
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bloom = 64OCTET
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; unsigned integer limiting the number of returned envelopes
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limit = 4OCTET
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; array of a cursor returned from the previous request (optional)
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cursor = *OCTET
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; List of topics interested in
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topics = "[" *1000topic "]"
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; 4 bytes of arbitrary data
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topic = 4OCTET
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payload-without-topic = "[" lower upper bloom limit [ cursor ] "]"
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payload-with-topic = "[" lower upper bloom limit cursor [ topics ] "]"
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payload = payload-with-topic | payload-without-topic
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```
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The `Cursor` field SHOULD be filled in if a number of envelopes between `Lower` and `Upper` is greater than `Limit` so that the requester can send another request using the obtained `Cursor` value. What exactly is in the `Cursor` is up to the implementation. The requester SHOULD NOT use a `Cursor` obtained from one mailserver in a request to another mailserver because the format or the result MAY be different.
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The envelope MUST be encrypted with a symmetric key agreed between the requester and Mailserver.
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If `Topics` is used the `Cursor` field MUST be specified for the argument order to be unambiguous. However, it MAY be set to `null`. `Topics` is used to specify which topics a node is interested in. If `Topics` is not empty, a mailserver MUST only send envelopes that belong to a topic from `Topics` list and `Bloom` value MUST be ignored.
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### Receiving Historic Envelopes
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Historic envelopes MUST be sent to a peer as a packet with a P2P Message code (`0x7f`) followed by an array of Waku envelopes. A Mailserver MUST limit the amount of messages sent, either by the `Limit` specified in the request or limited to the maximum [RLPx packet size](./waku#maximum-packet-size), whichever limit comes first.
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In order to receive historic envelopes from a mailserver, a node MUST trust the selected mailserver, that is allow to receive expired packets with the P2P Message code. By default, such packets are discarded.
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Received envelopes MUST be passed through the Whisper envelope pipelines so that they are picked up by registered filters and passed to subscribers.
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For a requester, to know that all envelopes have been sent by mailserver, it SHOULD handle P2P Request Complete code (`0x7d`). This code is followed by a list with:
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```abnf
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; array with a Keccak-256 hash of the envelope containing the original request.
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request-id = 32OCTET
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; array with a Keccak-256 hash of the last sent envelope for the request.
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last-envelope-hash = 32OCTET
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; array of a cursor returned from the previous request (optional)
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cursor = *OCTET
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payload = "[" request-id last-envelope-hash [ cursor ] "]"
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```
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If `Cursor` is not empty, it means that not all envelopes were sent due to the set `Limit` in the request. One or more consecutive requests MAY be sent with `Cursor` field filled in in order to receive the rest of the envelopes.
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### Security considerations
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There are several security considerations to take into account when running or interacting with Mailservers. Chief among them are: scalability, DDoS-resistance and privacy.
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**Mailserver High Availability requirement:**
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A mailserver has to be online to receive envelopes for other nodes, this puts a high availability requirement on it.
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**Mailserver client privacy:**
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A mailserver client fetches archival envelopes from a mailserver through a direct connection.
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In this direct connection, the client discloses its IP/ID as well as the topics/ bloom filter it is interested in to the mailserver.
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The collection of such information allows the mailserver to link clients' IP/IDs to their topic interests and build a profile for each client over time.
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As such, the mailserver client has to trust the mailserver with this level of information.
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A similar concern exists for the light nodes and their direct peers which is discussed in the security considerations of [6/WAKU1](/spec/7).
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**Mailserver trusted connection:**
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A mailserver has a direct TCP connection, which means they are trusted to send traffic. This means a malicious or malfunctioning mailserver can overwhelm an individual node.
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## Changelog
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| Version | Comment |
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| :--------------------------------------------------------------------------------------------: | ------- |
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| [1.0.0](https://github.com/vacp2p/specs/commit/bc7e75ebb2e45d2cbf6ab27352c113e666df37c8) | marked stable as it is in use. |
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| 0.2.0 | Add topic interest to reduce bandwidth usage |
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| [0.1.0](https://github.com/vacp2p/specs/blob/06d4c736c920526472a507e5d842212843a112ed/wms.md) | Initial Release |
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### Difference between wms 0.1 and wms 0.2
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- `topics` option
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## Copyright
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Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).
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