openmls 0.9.0-rc.1

//! # MlsGroup errors
//!
//! This module defines the public errors that can be returned from all calls
//! to methods of [`MlsGroup`](super::MlsGroup).

// These errors are exposed through `crate::group::errors`.

use openmls_traits::types::Ciphersuite;
use thiserror::Error;

use crate::{
    error::LibraryError,
    extensions::errors::InvalidExtensionError,
    group::{
        errors::{
            CreateAddProposalError, CreateCommitError, MergeCommitError, StageCommitError,
            ValidationError,
        },
        CommitBuilderStageError, CreateGroupContextExtProposalError,
    },
    schedule::errors::PskError,
    treesync::{
        errors::{LeafNodeValidationError, PublicTreeError},
        node::leaf_node::LeafNodeUpdateError,
    },
};

#[cfg(feature = "extensions-draft")]
pub use crate::schedule::application_export_tree::ApplicationExportTreeError;

#[cfg(doc)]
use crate::group::GroupId;

/// New group error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum NewGroupError<StorageError> {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// No matching KeyPackage was found in the key store.
    #[error("No matching KeyPackage was found in the key store.")]
    NoMatchingKeyPackage,
    /// Error accessing the storage.
    #[error("Error accessing the storage.")]
    StorageError(StorageError),
    /// Unsupported proposal type in required capabilities.
    #[error("Unsupported proposal type in required capabilities.")]
    UnsupportedProposalType,
    /// Unsupported extension type in required capabilities.
    #[error("Unsupported extension type in required capabilities.")]
    UnsupportedExtensionType,
    /// Invalid extensions set in configuration
    #[error("Invalid extensions set in configuration")]
    InvalidExtensions(#[from] InvalidExtensionError),
    /// A group with the given [`GroupId`] already exists.
    #[error("A group with the given GroupId already exists.")]
    GroupAlreadyExists,
    /// The ciphersuite is not supported by the crypto provider.
    #[error("Ciphersuite {0:?} is not supported by the crypto provider.")]
    UnsupportedCiphersuite(Ciphersuite),
    /// A virtual-clients processing error occurred.
    #[cfg(feature = "virtual-clients-draft")]
    #[error(transparent)]
    VirtualClientsError(#[from] crate::components::vc_derivation_info::VirtualClientsError),
}

/// An error when deleting past epoch secrets.
#[derive(Error, Debug, PartialEq, Eq, Clone)]
pub enum DeletePastEpochSecretsError<StorageError> {
    /// Error accessing the storage.
    #[error(transparent)]
    StorageError(#[from] StorageError),
}

/// An error when setting the past epoch deletion policy.
#[derive(Error, Debug, PartialEq, Eq, Clone)]
pub enum SetPastEpochDeletionPolicyError<StorageError> {
    /// Error accessing the storage.
    #[error(transparent)]
    StorageError(#[from] StorageError),
}

/// EmptyInput error
#[derive(Error, Debug, PartialEq, Eq, Clone)]
pub enum EmptyInputError {
    /// An empty list of KeyPackages was provided.
    #[error("An empty list of KeyPackages was provided.")]
    AddMembers,
    /// An empty list of KeyPackage references was provided.
    #[error("An empty list of KeyPackage references was provided.")]
    RemoveMembers,
}

/// Group state error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum MlsGroupStateError {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// Tried to use a group after being evicted from it.
    #[error("Tried to use a group after being evicted from it.")]
    UseAfterEviction,
    /// Can't create message because a pending proposal exists.
    #[error("Can't create message because a pending proposal exists.")]
    PendingProposal,
    /// Can't execute operation because a pending commit exists.
    #[error("Can't execute operation because a pending commit exists.")]
    PendingCommit,
    /// Can't execute operation because there is no pending commit.
    #[error("Can't execute operation because there is no pending commit")]
    NoPendingCommit,
    /// Requested pending proposal hasn't been found in local pending proposals
    #[error("Requested pending proposal hasn't been found in local pending proposals.")]
    PendingProposalNotFound,
}

/// Error merging pending commit
#[derive(Error, Debug, PartialEq, Clone)]
pub enum MergePendingCommitError<StorageError> {
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    MlsGroupStateError(#[from] MlsGroupStateError),
    /// See [`MergeCommitError`] for more details.
    #[error(transparent)]
    MergeCommitError(#[from] MergeCommitError<StorageError>),
}

/// Process message error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum PublicProcessMessageError {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// The message's wire format is incompatible with the group's wire format policy.
    #[error("The message's wire format is incompatible with the group's wire format policy.")]
    IncompatibleWireFormat,
    /// See [`ValidationError`] for more details.
    #[error(transparent)]
    ValidationError(#[from] ValidationError),
    /// See [`StageCommitError`] for more details.
    #[error(transparent)]
    InvalidCommit(#[from] StageCommitError),
    /// External application messages are not permitted.
    #[error("External application messages are not permitted.")]
    UnauthorizedExternalApplicationMessage,
    /// External commit messages are not permitted.
    #[error("Commit messages from external senders are not permitted.")]
    UnauthorizedExternalCommitMessage,
    /// The proposal is invalid for the Sender of type [External](crate::prelude::Sender::External)
    #[error("The proposal is invalid for the Sender of type External")]
    UnsupportedProposalType,

    /// The group's GroupContext requires Safe AAD framing, but the message's
    /// `authenticated_data` did not start with a well-formed `SafeAad`.
    #[cfg(feature = "extensions-draft")]
    #[error("malformed SafeAAD prefix in authenticated_data")]
    MalformedSafeAad,
}

/// Process message error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum ProcessMessageError<StorageError> {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// Error writing to storage.
    #[error("Error writing to storage: {0}")]
    StorageError(StorageError),
    /// The message's wire format is incompatible with the group's wire format policy.
    #[error("The message's wire format is incompatible with the group's wire format policy.")]
    IncompatibleWireFormat,
    /// See [`ValidationError`] for more details.
    #[error(transparent)]
    ValidationError(#[from] ValidationError),
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),
    /// See [`StageCommitError`] for more details.
    #[error(transparent)]
    InvalidCommit(#[from] StageCommitError),
    /// External application messages are not permitted.
    #[error("External application messages are not permitted.")]
    UnauthorizedExternalApplicationMessage,
    /// External commit messages are not permitted.
    #[error("Commit messages from external senders are not permitted.")]
    UnauthorizedExternalCommitMessage,
    /// The proposal is invalid for the Sender of type [External](crate::prelude::Sender::External)
    #[error("The proposal is invalid for the Sender of type External")]
    UnsupportedProposalType,
    /// The group's GroupContext requires Safe AAD framing, but the message's
    /// `authenticated_data` did not start with a well-formed `SafeAad`.
    #[cfg(feature = "extensions-draft")]
    #[error("malformed SafeAAD prefix in authenticated_data")]
    MalformedSafeAad,
}

/// Create message error
#[cfg(not(feature = "virtual-clients-draft"))]
#[derive(Error, Debug, PartialEq, Clone)]
pub enum CreateMessageError {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),
}

/// Add members error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum AddMembersError<StorageError> {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// See [`EmptyInputError`] for more details.
    #[error(transparent)]
    EmptyInput(#[from] EmptyInputError),
    /// See [`CreateCommitError`] for more details.
    #[error(transparent)]
    CreateCommitError(#[from] CreateCommitError),
    /// See [`CommitBuilderStageError`] for more details.
    #[error(transparent)]
    CommitBuilderStageError(#[from] CommitBuilderStageError<StorageError>),
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),
    /// Error writing to storage.
    #[error("Error writing to storage")]
    StorageError(StorageError),
}

/// Add members error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum SwapMembersError<StorageError> {
    /// Unable to map the key packages to the given leaf indices.
    #[error("Number of added and removed members is not the same")]
    InvalidInput,

    /// See [`EmptyInputError`] for more details.
    #[error(transparent)]
    EmptyInput(#[from] EmptyInputError),

    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),

    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),

    /// The member that should be removed can not be found.
    #[error("The member that should be removed can not be found.")]
    UnknownMember,

    /// Error writing to storage
    #[error("Error writing to storage: {0}")]
    StorageError(StorageError),

    /// See [`CommitBuilderStageError`] for more details.
    #[error(transparent)]
    CommitBuilderStageError(#[from] CommitBuilderStageError<StorageError>),

    /// See [`CreateCommitError`] for more details.
    #[error(transparent)]
    CreateCommitError(#[from] CreateCommitError),
}

/// Propose add members error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum ProposeAddMemberError<StorageError> {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// The new member does not support all required extensions.
    #[error("The new member does not support all required extensions.")]
    UnsupportedExtensions,
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),
    /// See [`LeafNodeValidationError`] for more details.
    #[error(transparent)]
    LeafNodeValidation(#[from] LeafNodeValidationError),
    /// Error writing to storage
    #[error("Error writing to storage: {0}")]
    StorageError(StorageError),
}

/// Propose remove members error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum ProposeRemoveMemberError<StorageError> {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),
    /// The member that should be removed can not be found.
    #[error("The member that should be removed can not be found.")]
    UnknownMember,
    /// Error writing to storage
    #[error("Error writing to storage: {0}")]
    StorageError(StorageError),
}

/// Remove members error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum RemoveMembersError<StorageError> {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// See [`EmptyInputError`] for more details.
    #[error(transparent)]
    EmptyInput(#[from] EmptyInputError),
    /// See [`CreateCommitError`] for more details.
    #[error(transparent)]
    CreateCommitError(#[from] CreateCommitError),
    /// See [`CommitBuilderStageError`] for more details.
    #[error(transparent)]
    CommitBuilderStageError(#[from] CommitBuilderStageError<StorageError>),
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),
    /// The member that should be removed can not be found.
    #[error("The member that should be removed can not be found.")]
    UnknownMember,
    /// Error writing to storage
    #[error("Error writing to storage: {0}")]
    StorageError(StorageError),
}

/// Leave group error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum LeaveGroupError<StorageError> {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),
    /// An error ocurred while writing to storage
    #[error("An error ocurred while writing to storage")]
    StorageError(StorageError),
    /// SelfRemove not allowed with pure ciphertext outgoing wire format policy.
    #[error("SelfRemove not allowed with pure ciphertext outgoing wire format policy.")]
    CannotSelfRemoveWithPureCiphertext,
}

/// Self update error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum SelfUpdateError<StorageError> {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// See [`CreateCommitError`] for more details.
    #[error(transparent)]
    CreateCommitError(#[from] CreateCommitError),
    /// See [`CommitBuilderStageError`] for more details.
    #[error(transparent)]
    CommitBuilderStageError(#[from] CommitBuilderStageError<StorageError>),
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),
    /// Error accessing the storage.
    #[error("Error accessing the storage.")]
    StorageError(StorageError),
    /// Virtual-clients error.
    #[cfg(feature = "virtual-clients-draft")]
    #[error(transparent)]
    VirtualClientsError(#[from] crate::components::vc_derivation_info::VirtualClientsError),
}

/// Propose self update error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum ProposeSelfUpdateError<StorageError> {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),

    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),
    /// Error accessing storage.
    #[error("Error accessing storage.")]
    StorageError(StorageError),
    /// See [`PublicTreeError`] for more details.
    #[error(transparent)]
    PublicTreeError(#[from] PublicTreeError),
    /// See [`LeafNodeUpdateError`] for more details.
    #[error(transparent)]
    LeafNodeUpdateError(#[from] LeafNodeUpdateError<StorageError>),
    /// The updated leaf node does not support all group context extensions.
    #[error("The updated leaf node does not support all group context extensions.")]
    UnsupportedGroupContextExtensions,
    /// The `leaf_node_parameters.credential_with_key` does not match
    /// `new_signer.credential_with_key` (rotation paths only).
    #[error("Mismatched credential_with_key between leaf_node_parameters and new_signer")]
    InvalidLeafNodeParameters,
    /// The `leaf_node_parameters.credential_with_key` does not match
    /// `new_signer.credential_with_key` (rotation paths only).
    #[error("Mismatched ciphersuite between new_signer and the group")]
    InvalidSignerCiphersuite,
}

/// Commit to pending proposals error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum CommitToPendingProposalsError<StorageError> {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// See [`CreateCommitError`] for more details.
    #[error(transparent)]
    CreateCommitError(#[from] CreateCommitError),
    /// See [`CommitBuilderStageError`] for more details.
    #[error(transparent)]
    CommitBuilderStageError(#[from] CommitBuilderStageError<StorageError>),
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),
    /// Error writing to storage
    #[error("Error writing to storage: {0}")]
    StorageError(StorageError),
}

/// Errors that can happen when exporting a group info object.
#[derive(Error, Debug, PartialEq, Clone)]
pub enum ExportGroupInfoError {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),
    /// See [`InvalidExtensionError`] for more details.
    #[error(transparent)]
    InvalidExtensionError(#[from] InvalidExtensionError),
}

/// Export secret error
#[cfg(feature = "extensions-draft")]
#[derive(Error, Debug, PartialEq, Clone)]
pub enum SafeExportSecretError<StorageError> {
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupState(#[from] MlsGroupStateError),
    /// See [`ApplicationExportTreeError`] for more details.
    #[error(transparent)]
    ApplicationExportTree(#[from] ApplicationExportTreeError),
    /// Group doesn't support application exports.
    #[error("Group doesn't support application exports.")]
    Unsupported,
    /// Storage error
    #[error("Error accessing storage: {0}")]
    Storage(StorageError),
}

/// Error resolving a processed message carrying an unresolved app data commit.
#[cfg(feature = "extensions-draft")]
#[derive(Error, Debug, PartialEq, Clone)]
pub enum ResolveAppDataCommitError {
    /// The processed message does not carry an unresolved app data commit.
    #[error("The processed message does not carry an unresolved app data commit.")]
    NotAnUnresolvedAppDataCommit,
    /// See [`StageCommitError`] for more details.
    #[error(transparent)]
    StageCommit(#[from] StageCommitError),
}

/// Export secret error
#[cfg(feature = "extensions-draft")]
#[derive(Error, Debug, PartialEq, Clone)]
pub enum ProcessedMessageSafeExportSecretError {
    /// See [`StagedSafeExportSecretError`] for more details.
    #[error(transparent)]
    SafeExportSecretError(#[from] StagedSafeExportSecretError),
    /// Processed message is not a commit.
    #[error("Processed message is not a commit.")]
    NotACommit,
}

/// Export secret error
#[cfg(feature = "extensions-draft")]
#[derive(Error, Debug, PartialEq, Clone)]
pub enum PendingSafeExportSecretError<StorageError> {
    /// See [`StagedSafeExportSecretError`] for more details.
    #[error(transparent)]
    SafeExportSecretError(#[from] StagedSafeExportSecretError),
    /// No pending commit.
    #[error("No pending commit.")]
    NoPendingCommit,
    /// Storage error
    #[error("Error accessing storage: {0}")]
    Storage(StorageError),
    /// Only group members can export secrets.
    #[error("Only group members can export secrets.")]
    NotGroupMember,
}

/// Export secret from a pending commit
#[cfg(feature = "extensions-draft")]
#[derive(Error, Debug, PartialEq, Clone)]
pub enum StagedSafeExportSecretError {
    /// Only group members can export secrets.
    #[error("Only group members can export secrets.")]
    NotGroupMember,
    /// See [`ApplicationExportTreeError`] for more details.
    #[error(transparent)]
    ApplicationExportTree(#[from] ApplicationExportTreeError),
    /// Group doesn't support application exports.
    #[error("Group doesn't support application exports.")]
    Unsupported,
}

/// Export secret error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum ExportSecretError {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// The requested key length is too long.
    #[error("The requested key length is too long.")]
    KeyLengthTooLong,
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),
}

/// Propose PSK error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum ProposePskError {
    /// See [`PskError`] for more details.
    #[error(transparent)]
    Psk(#[from] PskError),
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
}

/// Proposal error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum ProposalError<StorageError> {
    /// See [`LibraryError`] for more details.
    #[error(transparent)]
    LibraryError(#[from] LibraryError),
    /// See [`ProposeAddMemberError`] for more details.
    #[error(transparent)]
    ProposeAddMemberError(#[from] ProposeAddMemberError<StorageError>),
    /// See [`CreateAddProposalError`] for more details.
    #[error(transparent)]
    CreateAddProposalError(#[from] CreateAddProposalError),
    /// See [`ProposeSelfUpdateError`] for more details.
    #[error(transparent)]
    ProposeSelfUpdateError(#[from] ProposeSelfUpdateError<StorageError>),
    /// See [`ProposeRemoveMemberError`] for more details.
    #[error(transparent)]
    ProposeRemoveMemberError(#[from] ProposeRemoveMemberError<StorageError>),
    /// See [`MlsGroupStateError`] for more details.
    #[error(transparent)]
    GroupStateError(#[from] MlsGroupStateError),
    /// See [`ValidationError`] for more details.
    #[error(transparent)]
    ValidationError(#[from] ValidationError),
    /// See [`CreateGroupContextExtProposalError`] for more details.
    #[error(transparent)]
    CreateGroupContextExtProposalError(#[from] CreateGroupContextExtProposalError<StorageError>),
    /// See [`InvalidExtensionError`]
    #[error(transparent)]
    InvalidExtension(#[from] InvalidExtensionError),
    /// Error writing proposal to storage.
    #[error("error writing proposal to storage")]
    StorageError(StorageError),
}

/// Remove proposal error
#[derive(Error, Debug, PartialEq, Clone)]
pub enum RemoveProposalError<StorageError> {
    /// Couldn't find the proposal for the given `ProposalRef`.
    #[error("Couldn't find the proposal for the given `ProposalRef`")]
    ProposalNotFound,
    /// Error erasing proposal from storage.
    #[error("error writing proposal to storage")]
    Storage(StorageError),
}

#[cfg(feature = "virtual-clients-draft")]
pub use virtual_clients_draft::*;

#[cfg(feature = "virtual-clients-draft")]
mod virtual_clients_draft {
    use thiserror::Error;

    use super::MlsGroupStateError;
    use crate::error::LibraryError;
    use crate::framing::MessageEncryptionError;
    use crate::group::SafeExportSecretError;
    use crate::tree::secret_tree::SecretTreeError;

    /// Create message error
    #[derive(Error, Debug, PartialEq, Clone)]
    pub enum CreateMessageError<StorageError> {
        /// See [`LibraryError`] for more details.
        #[error(transparent)]
        LibraryError(#[from] LibraryError),
        /// See [`MlsGroupStateError`] for more details.
        #[error(transparent)]
        GroupStateError(#[from] MlsGroupStateError),
        /// See [`MessageEncryptionError`] for more details.
        #[error(transparent)]
        MessageEncryptionError(#[from] MessageEncryptionError<StorageError>),
        /// Error writing to storage.
        #[error("Error writing to storage: {0}")]
        StorageError(StorageError),
    }

    /// Confirm message error
    #[derive(Error, Debug, PartialEq, Clone)]
    pub enum ConfirmMessageError<StorageError> {
        /// See [`SecretTreeError`] for more details.
        #[error(transparent)]
        SecretTreeError(#[from] SecretTreeError),
        /// The requested epoch is newer than the group's current epoch.
        #[error("The requested epoch is newer than the group's current epoch.")]
        FutureEpoch,
        /// Error writing to storage.
        #[error("Error writing to storage: {0}")]
        StorageError(StorageError),
    }

    impl<StorageError> From<ConfirmMessageError<StorageError>> for CreateMessageError<StorageError> {
        fn from(err: ConfirmMessageError<StorageError>) -> Self {
            match err {
                ConfirmMessageError::SecretTreeError(e) => {
                    CreateMessageError::MessageEncryptionError(
                        MessageEncryptionError::SecretTreeError(e),
                    )
                }
                // Unreachable: `create_message` confirms at the current epoch,
                // which never triggers the future-epoch guard.
                ConfirmMessageError::FutureEpoch => CreateMessageError::LibraryError(
                    LibraryError::custom("confirm_application_message reported a future epoch"),
                ),
                ConfirmMessageError::StorageError(e) => CreateMessageError::StorageError(e),
            }
        }
    }

    /// Errors returned by
    /// [`MlsGroup::register_vc_emulation_epoch`](crate::group::MlsGroup::register_vc_emulation_epoch).
    #[derive(Error, Debug, PartialEq, Clone)]
    pub enum RegisterVcEmulationEpochError<StorageError> {
        /// See [`SafeExportSecretError`] for more details.
        #[error(transparent)]
        SafeExportSecret(#[from] SafeExportSecretError<StorageError>),
        /// See [`VirtualClientsError`](crate::components::vc_derivation_info::VirtualClientsError)
        /// for more details.
        #[error(transparent)]
        VirtualClients(#[from] crate::components::vc_derivation_info::VirtualClientsError),
        /// Persisting the derived virtual-clients state to storage failed.
        #[error("Error writing virtual-clients state to storage")]
        Storage(StorageError),
    }
}