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//! Configuration module for [`MlsGroup`] configurations.
//!
//! ## Building an MlsGroupConfig
//! The [`MlsGroupConfigBuilder`] makes it easy to build configurations for the
//! [`MlsGroup`].
//!
//! ```
//! use openmls::prelude::*;
//!
//! let group_config = MlsGroupConfig::builder()
//! .use_ratchet_tree_extension(true)
//! .build();
//! ```
//!
//! See [`MlsGroupConfigBuilder`](MlsGroupConfigBuilder#implementations) for
//! all options that can be configured.
//!
//! ### Wire format policies
//! Only some combination of possible wire formats are valid within OpenMLS.
//! The [`WIRE_FORMAT_POLICIES`] lists all valid options that can be set.
//!
//! ```
//! use openmls::prelude::*;
//!
//! let group_config = MlsGroupConfig::builder()
//! .wire_format_policy(MIXED_CIPHERTEXT_WIRE_FORMAT_POLICY)
//! .build();
//! ```
use super::*;
use crate::{
group::config::CryptoConfig, key_packages::Lifetime,
tree::sender_ratchet::SenderRatchetConfiguration,
};
use serde::{Deserialize, Serialize};
/// Specifies the configuration parameters for a [`MlsGroup`]. Refer to
/// the [User Manual](https://openmls.tech/book/user_manual/group_config.html) for more information about the different configuration values.
#[derive(Clone, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
pub struct MlsGroupConfig {
/// Defines the wire format policy for outgoing and incoming handshake messages.
/// Application are always encrypted regardless.
pub(crate) wire_format_policy: WireFormatPolicy,
/// Size of padding in bytes
pub(crate) padding_size: usize,
/// Maximum number of past epochs for which application messages
/// can be decrypted. The default is 0.
pub(crate) max_past_epochs: usize,
/// Number of resumtion secrets to keep
pub(crate) number_of_resumption_psks: usize,
/// Flag to indicate the Ratchet Tree Extension should be used
pub(crate) use_ratchet_tree_extension: bool,
/// Required capabilities (extensions and proposal types)
pub(crate) required_capabilities: RequiredCapabilitiesExtension,
/// Senders authorized to send external remove proposals
pub(crate) external_senders: ExternalSendersExtension,
/// Sender ratchet configuration
pub(crate) sender_ratchet_configuration: SenderRatchetConfiguration,
/// Lifetime of the own leaf node
pub(crate) lifetime: Lifetime,
/// Ciphersuite and protocol version
pub(crate) crypto_config: CryptoConfig,
}
impl MlsGroupConfig {
/// Returns a builder for [`MlsGroupConfig`]
pub fn builder() -> MlsGroupConfigBuilder {
MlsGroupConfigBuilder::new()
}
/// Returns the [`MlsGroupConfig`] wire format policy.
pub fn wire_format_policy(&self) -> WireFormatPolicy {
self.wire_format_policy
}
/// Returns the [`MlsGroupConfig`] padding size.
pub fn padding_size(&self) -> usize {
self.padding_size
}
/// Returns the [`MlsGroupConfig`] max past epochs.
pub fn max_past_epochs(&self) -> usize {
self.max_past_epochs
}
/// Returns the [`MlsGroupConfig`] number of resumption psks.
pub fn number_of_resumption_psks(&self) -> usize {
self.number_of_resumption_psks
}
/// Returns the [`MlsGroupConfig`] boolean flag that indicates whether ratchet_tree_extension should be used.
pub fn use_ratchet_tree_extension(&self) -> bool {
self.use_ratchet_tree_extension
}
/// Returns the [`MlsGroupConfig`] sender ratchet configuration.
pub fn sender_ratchet_configuration(&self) -> &SenderRatchetConfiguration {
&self.sender_ratchet_configuration
}
/// Returns the [`MlsGroupConfig`] external senders extension
pub fn external_senders(&self) -> &ExternalSendersExtension {
&self.external_senders
}
/// Returns the [`MlsGroupConfig`] lifetime configuration.
pub fn lifetime(&self) -> &Lifetime {
&self.lifetime
}
/// Returns the [`CryptoConfig`].
pub fn crypto_config(&self) -> &CryptoConfig {
&self.crypto_config
}
#[cfg(any(feature = "test-utils", test))]
pub fn test_default(ciphersuite: Ciphersuite) -> Self {
Self::builder()
.wire_format_policy(WireFormatPolicy::new(
OutgoingWireFormatPolicy::AlwaysPlaintext,
IncomingWireFormatPolicy::Mixed,
))
.crypto_config(CryptoConfig::with_default_version(ciphersuite))
.build()
}
}
/// Builder for an [`MlsGroupConfig`].
#[derive(Default)]
pub struct MlsGroupConfigBuilder {
config: MlsGroupConfig,
}
impl MlsGroupConfigBuilder {
/// Creates a new builder with default values.
pub fn new() -> Self {
MlsGroupConfigBuilder {
config: MlsGroupConfig::default(),
}
}
/// Sets the `wire_format` property of the MlsGroupConfig.
pub fn wire_format_policy(mut self, wire_format_policy: WireFormatPolicy) -> Self {
self.config.wire_format_policy = wire_format_policy;
self
}
/// Sets the `padding_size` property of the MlsGroupConfig.
pub fn padding_size(mut self, padding_size: usize) -> Self {
self.config.padding_size = padding_size;
self
}
/// Sets the `max_past_epochs` property of the MlsGroupConfig.
/// This allows application messages from previous epochs to be decrypted.
///
/// **WARNING**
///
/// This feature enables the storage of message secrets from past epochs.
/// It is a trade-off between functionality and forward secrecy and should only be enabled
/// if the Delivery Service cannot guarantee that application messages will be sent in
/// the same epoch in which they were generated. The number for `max_epochs` should be
/// as low as possible.
pub fn max_past_epochs(mut self, max_past_epochs: usize) -> Self {
self.config.max_past_epochs = max_past_epochs;
self
}
/// Sets the `number_of_resumption_psks` property of the MlsGroupConfig.
pub fn number_of_resumption_psks(mut self, number_of_resumption_psks: usize) -> Self {
self.config.number_of_resumption_psks = number_of_resumption_psks;
self
}
/// Sets the `use_ratchet_tree_extension` property of the MlsGroupConfig.
pub fn use_ratchet_tree_extension(mut self, use_ratchet_tree_extension: bool) -> Self {
self.config.use_ratchet_tree_extension = use_ratchet_tree_extension;
self
}
/// Sets the `sender_ratchet_configuration` property of the MlsGroupConfig.
/// See [`SenderRatchetConfiguration`] for more information.
pub fn sender_ratchet_configuration(
mut self,
sender_ratchet_configuration: SenderRatchetConfiguration,
) -> Self {
self.config.sender_ratchet_configuration = sender_ratchet_configuration;
self
}
/// Sets the `lifetime` property of the MlsGroupConfig.
pub fn lifetime(mut self, lifetime: Lifetime) -> Self {
self.config.lifetime = lifetime;
self
}
/// Sets the `crypto_config` property of the MlsGroupConfig.
pub fn crypto_config(mut self, config: CryptoConfig) -> Self {
self.config.crypto_config = config;
self
}
/// Sets the `external_senders` property of the MlsGroupConfig.
pub fn external_senders(mut self, external_senders: ExternalSendersExtension) -> Self {
self.config.external_senders = external_senders;
self
}
/// Finalizes the builder and retursn an `[MlsGroupConfig`].
pub fn build(self) -> MlsGroupConfig {
self.config
}
}
/// Defines what wire format is acceptable for incoming handshake messages.
/// Note that application messages must always be encrypted.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub enum IncomingWireFormatPolicy {
/// Handshake messages must always be PrivateMessage
AlwaysCiphertext,
/// Handshake messages must always be PublicMessage
AlwaysPlaintext,
/// Handshake messages can either be PrivateMessage or PublicMessage
Mixed,
}
impl IncomingWireFormatPolicy {
pub(crate) fn is_compatible_with(&self, wire_format: WireFormat) -> bool {
match self {
IncomingWireFormatPolicy::AlwaysCiphertext => wire_format == WireFormat::PrivateMessage,
IncomingWireFormatPolicy::AlwaysPlaintext => wire_format == WireFormat::PublicMessage,
IncomingWireFormatPolicy::Mixed => {
wire_format == WireFormat::PrivateMessage
|| wire_format == WireFormat::PublicMessage
}
}
}
}
/// Defines what wire format should be used for outgoing handshake messages.
/// Note that application messages must always be encrypted.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub enum OutgoingWireFormatPolicy {
/// Handshake messages must always be PrivateMessage
AlwaysCiphertext,
/// Handshake messages must always be PublicMessage
AlwaysPlaintext,
}
/// Defines what wire format is desired for outgoing handshake messages.
/// Note that application messages must always be encrypted.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct WireFormatPolicy {
outgoing: OutgoingWireFormatPolicy,
incoming: IncomingWireFormatPolicy,
}
impl WireFormatPolicy {
/// Creates a new wire format policy from an [`OutgoingWireFormatPolicy`]
/// and an [`IncomingWireFormatPolicy`].
#[cfg(any(feature = "test-utils", test))]
pub(crate) fn new(
outgoing: OutgoingWireFormatPolicy,
incoming: IncomingWireFormatPolicy,
) -> Self {
Self { outgoing, incoming }
}
/// Returns a reference to the wire format policy's outgoing wire format policy.
pub fn outgoing(&self) -> OutgoingWireFormatPolicy {
self.outgoing
}
/// Returns a reference to the wire format policy's incoming wire format policy.
pub fn incoming(&self) -> IncomingWireFormatPolicy {
self.incoming
}
}
impl Default for WireFormatPolicy {
fn default() -> Self {
PURE_CIPHERTEXT_WIRE_FORMAT_POLICY
}
}
impl From<OutgoingWireFormatPolicy> for WireFormat {
fn from(outgoing: OutgoingWireFormatPolicy) -> Self {
match outgoing {
OutgoingWireFormatPolicy::AlwaysCiphertext => WireFormat::PrivateMessage,
OutgoingWireFormatPolicy::AlwaysPlaintext => WireFormat::PublicMessage,
}
}
}
/// All valid wire format policy combinations.
/// - [`PURE_PLAINTEXT_WIRE_FORMAT_POLICY`]
/// - [`PURE_CIPHERTEXT_WIRE_FORMAT_POLICY`]
/// - [`MIXED_PLAINTEXT_WIRE_FORMAT_POLICY`]
/// - [`MIXED_CIPHERTEXT_WIRE_FORMAT_POLICY`]
pub const WIRE_FORMAT_POLICIES: [WireFormatPolicy; 4] = [
PURE_PLAINTEXT_WIRE_FORMAT_POLICY,
PURE_CIPHERTEXT_WIRE_FORMAT_POLICY,
MIXED_PLAINTEXT_WIRE_FORMAT_POLICY,
MIXED_CIPHERTEXT_WIRE_FORMAT_POLICY,
];
/// Incoming and outgoing wire formats are always plaintext.
pub const PURE_PLAINTEXT_WIRE_FORMAT_POLICY: WireFormatPolicy = WireFormatPolicy {
outgoing: OutgoingWireFormatPolicy::AlwaysPlaintext,
incoming: IncomingWireFormatPolicy::AlwaysPlaintext,
};
/// Incoming and outgoing wire formats are always ciphertext.
pub const PURE_CIPHERTEXT_WIRE_FORMAT_POLICY: WireFormatPolicy = WireFormatPolicy {
outgoing: OutgoingWireFormatPolicy::AlwaysCiphertext,
incoming: IncomingWireFormatPolicy::AlwaysCiphertext,
};
/// Incoming wire formats can be mixed while outgoing wire formats are always
/// plaintext.
pub const MIXED_PLAINTEXT_WIRE_FORMAT_POLICY: WireFormatPolicy = WireFormatPolicy {
outgoing: OutgoingWireFormatPolicy::AlwaysPlaintext,
incoming: IncomingWireFormatPolicy::Mixed,
};
/// Incoming wire formats can be mixed while outgoing wire formats are always
/// ciphertext.
pub const MIXED_CIPHERTEXT_WIRE_FORMAT_POLICY: WireFormatPolicy = WireFormatPolicy {
outgoing: OutgoingWireFormatPolicy::AlwaysCiphertext,
incoming: IncomingWireFormatPolicy::Mixed,
};