Module framing

Message framing

This module contains framing-related operations for MLS messages, including validation operations. The general structure of the framing process in OpenMLS closely mirrors the one described in Section 7 of the MLS specification. It can be visualized as follows:

                              Proposal        Commit     Application Data
                                 |              |              |
                                 +--------------+--------------+
                                                |
                                                V
                                         FramedContent
                                             |  |                -.
                                             |  |                  |
                                    +--------+  |                  |
                                    |           |                  |
                                    V           |                  +-- Asymmetric
                          FramedContentAuthData |                  |   Sign / Verify
                                    |           |                  |
                                    +--------+  |                  |
                                             |  |                  |
                                             V  V                -'
                                       AuthenticatedContent
                                                |                -.
                                                |                  |
                                                |                  |
                                       +--------+--------+         +-- Symmetric
                                       |                 |         |   Protect / Unprotect
                                       V                 V         |
Welcome  KeyPackage  GroupInfo   PublicMessage    PrivateMessage -'
   |          |          |             |                 |
   |          |          |             |                 |
   +----------+----------+----+--------+-----------------+
                              |
                              V
                          MLSMessage

• MlsMessageIn/MlsMessageOut: Unified message type for incoming & outgoing MLS messages
• ApplicationMessage: Application message received through a ProcessedMessage

Modules

• errors
  Framing errors.

Structs

• ApplicationMessage
  Application message received through a ProcessedMessage.
• MlsMessageIn
  Before use with the MlsGroup API, the message has to be unpacked via extract to yield its MlsMessageBodyIn.
• MlsMessageOut
  An MlsMessageOut is typically returned from an MlsGroup function and meant to be serialized and sent to the DS.
• PrivateMessage
  PrivateMessage is the framing struct for an encrypted PublicMessage. This message format is meant to be sent to and received from the Delivery Service.
• PrivateMessageIn
  PrivateMessage is the framing struct for an encrypted PublicMessage. This message format is meant to be sent to and received from the Delivery Service.
• ProcessedMessage
  A message that has passed all syntax and semantics checks.
• PublicMessage
  PublicMessage is a framing structure for MLS messages. It can contain Proposals, Commits and application messages.
• PublicMessageIn
  PublicMessageIn is a framing structure for MLS messages. It can contain Proposals, Commits and application messages.

Enums

• ContentType
• MlsMessageBodyIn
  MLSMessage (Body)
• MlsMessageBodyOut
  MLSMessage (Body)
• ProcessedMessageContent
  Content of a processed message.
• ProtocolMessage
  Enum containing a message for use with process_message and an MlsGroup. Both PublicMessage and PrivateMessage implement Into<ProtocolMessage>.
• Sender
  All possible sender types according to the MLS protocol spec.
• WireFormat
  Wire format of MLS messages.