core_crypto/transaction_context/credential/

mod.rs

mod check;

use std::sync::Arc;

use super::{Error, Result};
use crate::{Credential, CredentialRef, RecursiveError, transaction_context::TransactionContext};

impl TransactionContext {
    /// Add a credential to the database of this session without validating that its client ID matches the session
    /// client id.
    ///
    /// This is rarely useful and should only be used when absolutely necessary. You'll know it if you need it.
    ///
    /// Prefer [`Self::add_credential`].
    pub(crate) fn add_credential_without_clientid_check(&self, mut credential: Credential) -> Result<Arc<Credential>> {
        let inner = self.inner()?;
        let _credential_ref = credential
            .save(&inner.transaction)
            .map_err(RecursiveError::context("saving credential"))?;

        Ok(Arc::new(credential))
    }
    /// Add a credential to the database of this session.
    pub async fn add_credential(&self, credential: Credential) -> Result<CredentialRef> {
        let credential = self.add_credential_producing_arc(credential).await?;
        Ok(CredentialRef::from_credential(&credential))
    }

    /// Add a credential to the database of this session.
    ///
    /// Returns the actual credential instance which was loaded from the DB.
    /// This is a convenience for internal use and should _not_ be propagated across
    /// the FFI boundary. Instead, use [`Self::add_credential`] to produce a [`CredentialRef`].
    pub(crate) async fn add_credential_producing_arc(&self, credential: Credential) -> Result<Arc<Credential>> {
        if *credential.client_id() != self.session().await?.id() {
            return Err(Error::WrongCredential);
        }

        self.add_credential_without_clientid_check(credential)
    }

    /// Remove a credential from the database of this session.
    ///
    /// First checks that the credential is not used in any conversation.
    /// Removes both the credential itself and also any key packages which were generated from it.
    pub async fn remove_credential(&self, credential_ref: &CredentialRef) -> Result<bool> {
        // setup
        if *credential_ref.client_id() != self.session().await?.id() {
            return Err(Error::WrongCredential);
        }

        let inner = self.inner()?;

        // this happens before propagating removal to the keypackages so we can error appropriately
        let removed = credential_ref.delete(&inner.transaction).map_err(|err| -> Error {
            let crate::KeystoreError { source, .. } = &err;
            let Some(core_crypto_keystore::CryptoKeystoreError::DbError(rusqlite_err)) = source.downcast_ref() else {
                return err.into();
            };
            if rusqlite_err
                .sqlite_error_code()
                .is_some_and(|code| code == core_crypto_keystore::RusqliteErrorCode::ConstraintViolation)
            {
                Error::CredentialStillInUse
            } else {
                err.into()
            }
        })?;

        // remove any key packages generated by this credential
        self.remove_key_packages_for(credential_ref).await?;

        Ok(removed)
    }
}

#[cfg(test)]
mod tests {
    use core_crypto_keystore::{
        Sha256Hash,
        entities::{StoredCredential, StoredCredentialPk, StoredKeyPackage},
        traits::FetchFromDatabase as _,
    };
    use openmls::prelude::KeyPackage;

    use super::*;
    use crate::{CertificateBundle, test_utils::*};

    async fn credential_is_stored(session: &SessionContext, credential: &CredentialRef) -> bool {
        session
            .transaction
            .database()
            .unwrap()
            .get::<StoredCredential>(&StoredCredentialPk::new(
                credential.public_key_hash(),
                credential.r#type().into(),
            ))
            .await
            .unwrap()
            .is_some()
    }

    /// How many stored key packages were generated from `credential`.
    async fn count_key_packages_for(session: &SessionContext, credential: &CredentialRef) -> usize {
        session
            .transaction
            .database()
            .unwrap()
            .load_all::<StoredKeyPackage>()
            .await
            .unwrap()
            .into_iter()
            .map(|stored| core_crypto_keystore::deser::<KeyPackage>(&stored.key_package).unwrap())
            .filter(|key_package| {
                Sha256Hash::hash_from(key_package.leaf_node().signature_key().as_slice())
                    == credential.public_key_hash()
            })
            .count()
    }

    /// A credential a conversation still uses cannot be removed, and the refused removal writes nothing: neither the
    /// credential nor the key packages generated from it go missing. Once the conversation moves on to another
    /// credential, the old one can be removed.
    #[apply(all_cred_cipher)]
    async fn credential_in_use_by_a_conversation_cannot_be_removed(case: TestContext) {
        const KEY_PACKAGES: usize = 2;

        let [alice] = case.sessions().await;
        let conversation = case.create_conversation([&alice]).await;
        let credential = alice.initial_credential.clone();

        for _ in 0..KEY_PACKAGES {
            alice.new_keypackage_from_ref(credential.clone(), None).await;
        }
        assert_eq!(count_key_packages_for(&alice, &credential).await, KEY_PACKAGES);

        let result = alice.transaction.remove_credential(&credential).await;
        assert!(
            matches!(result, Err(Error::CredentialStillInUse)),
            "removing a credential in use must fail with `CredentialStillInUse`, but got {result:?}"
        );

        // The caller may catch the error and carry on with this transaction, so the failed removal must not have
        // written anything.
        assert!(
            credential_is_stored(&alice, &credential).await,
            "a refused removal must keep the credential"
        );
        assert_eq!(
            count_key_packages_for(&alice, &credential).await,
            KEY_PACKAGES,
            "a refused removal must keep the key packages generated from the credential"
        );

        // A basic credential is just our client id, so a "new" one for the same client compares equal to the old one
        // and openmls declines to rotate anything. Only x509 can rotate here.
        if !case.is_x509() {
            return;
        }

        let intermediate_ca = alice.x509_chain_unchecked().find_local_intermediate_ca();
        let certificate = CertificateBundle::new_with_default_values(intermediate_ca, None);
        let new_credential = Credential::x509(case.cipher_suite(), certificate).unwrap();
        alice
            .transaction
            .add_credential_without_clientid_check(new_credential.clone())
            .unwrap();
        let new_credential = CredentialRef::from_credential(&new_credential);
        conversation.set_credential_by_ref_notify(&new_credential).await;

        let removed = alice
            .transaction
            .remove_credential(&credential)
            .await
            .expect("a credential no conversation uses any more can be removed");
        assert!(removed, "removal must report that the credential was deleted");
        assert!(!credential_is_stored(&alice, &credential).await);
        assert_eq!(count_key_packages_for(&alice, &credential).await, 0);
    }
}