megolm

Documentation

Overview

megolm provides the ratchet used by the megolm protocol

Index

• Constants
• Variables
• type Ratchet
  • func New(counter uint32, data [RatchetParts * RatchetPartLength]byte) (*Ratchet, error)
  • func NewWithRandom(counter uint32) (*Ratchet, error)
  • func (m *Ratchet) Advance()
  • func (m *Ratchet) AdvanceTo(target uint32)
  • func (r Ratchet) Decrypt(ciphertext []byte, signingkey *crypto.Ed25519PublicKey, ...) ([]byte, error)
  • func (r *Ratchet) Encrypt(plaintext []byte, key *crypto.Ed25519KeyPair) ([]byte, error)
  • func (r Ratchet) PickleAsJSON(key []byte) ([]byte, error)
  • func (r Ratchet) PickleLibOlm(encoder *libolmpickle.Encoder)
  • func (r Ratchet) SessionExportMessage(key crypto.Ed25519PublicKey) ([]byte, error)
  • func (r Ratchet) SessionSharingMessage(key crypto.Ed25519KeyPair) ([]byte, error)
  • func (r *Ratchet) UnpickleAsJSON(pickled, key []byte) error
  • func (r *Ratchet) UnpickleLibOlm(decoder *libolmpickle.Decoder) error

Constants

const (
	RatchetParts      = 4       // number of ratchet parts
	RatchetPartLength = 256 / 8 // length of each ratchet part in bytes
)

Variables

var RatchetCipher = cipher.NewAESSHA256([]byte("MEGOLM_KEYS"))

Types

type Ratchet

type Ratchet struct {
	Data    [RatchetParts * RatchetPartLength]byte `json:"data"`
	Counter uint32                                 `json:"counter"`
}

Ratchet represents the megolm ratchet as described in

https://gitlab.matrix.org/matrix-org/olm/-/blob/master/docs/megolm.md

func New

func New(counter uint32, data [RatchetParts * RatchetPartLength]byte) (*Ratchet, error)

New creates a new ratchet with counter set to counter and the ratchet data set to data.

func NewWithRandom

func NewWithRandom(counter uint32) (*Ratchet, error)

NewWithRandom creates a new ratchet with counter set to counter an the data filled with random values.

func (*Ratchet) Advance

func (m *Ratchet) Advance()

Advance advances the ratchet one step.

func (*Ratchet) AdvanceTo

func (m *Ratchet) AdvanceTo(target uint32)

AdvanceTo advances the ratchet so that the ratchet counter = target

func (Ratchet) Decrypt

func (r Ratchet) Decrypt(ciphertext []byte, signingkey *crypto.Ed25519PublicKey, msg *message.GroupMessage) ([]byte, error)

Decrypt decrypts the ciphertext and verifies the MAC but not the signature.

func (*Ratchet) Encrypt

func (r *Ratchet) Encrypt(plaintext []byte, key *crypto.Ed25519KeyPair) ([]byte, error)

Encrypt encrypts the message in a message.GroupMessage with MAC and signature. The output is base64 encoded.

func (Ratchet) PickleAsJSON

func (r Ratchet) PickleAsJSON(key []byte) ([]byte, error)

PickleAsJSON returns a ratchet as a base64 string encrypted using the supplied key. The unencrypted representation of the Account is in JSON format.

func (Ratchet) PickleLibOlm

func (r Ratchet) PickleLibOlm(encoder *libolmpickle.Encoder)

PickleLibOlm pickles the ratchet into the encoder.

func (Ratchet) SessionExportMessage

func (r Ratchet) SessionExportMessage(key crypto.Ed25519PublicKey) ([]byte, error)

SessionExportMessage creates a message in the session export format.

func (Ratchet) SessionSharingMessage

func (r Ratchet) SessionSharingMessage(key crypto.Ed25519KeyPair) ([]byte, error)

SessionSharingMessage creates a message in the session sharing format.

func (*Ratchet) UnpickleAsJSON

func (r *Ratchet) UnpickleAsJSON(pickled, key []byte) error

UnpickleAsJSON updates a ratchet by a base64 encrypted string using the supplied key. The unencrypted representation has to be in JSON format.

func (*Ratchet) UnpickleLibOlm

func (r *Ratchet) UnpickleLibOlm(decoder *libolmpickle.Decoder) error

UnpickleLibOlm decodes the unencryted value and populates the Ratchet accordingly. It returns the number of bytes read.