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crypto: Check the recipient and recipient keys for decrypted events.

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This commit is contained in:
Damir Jelić 2020-04-22 15:15:08 +02:00
parent 0eab02a941
commit 27ae8bccb9
1 changed files with 87 additions and 32 deletions
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119
src/crypto/machine.rs
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@ -655,13 +655,13 @@ impl OlmMachine {
async fn try_decrypt_olm_event(
&mut self,
sender: &str,
sender: &UserId,
sender_key: &str,
message: &OlmMessage,
) -> Result<Option<String>> {
let s = self.store.get_sessions(sender_key).await?;
/// We don't have any existing sessions, return early.
// We don't have any existing sessions, return early.
let sessions = if let Some(s) = s {
s
} else {
@ -708,10 +708,10 @@ impl OlmMachine {
async fn decrypt_olm_message(
&mut self,
sender: &str,
sender: &UserId,
sender_key: &str,
message: OlmMessage,
) -> Result<EventResult<ToDeviceEvent>> {
) -> Result<(EventResult<ToDeviceEvent>, String)> {
// First try to decrypt using an existing session.
let plaintext = if let Some(p) = self
.try_decrypt_olm_event(sender, sender_key, &message)
@ -724,8 +724,8 @@ impl OlmMachine {
// Decryption failed with every known session, let's try to create a
// new session.
let mut session = match &message {
/// A new session can only be created using a pre-key message,
/// return with an error if it isn't one.
// A new session can only be created using a pre-key message,
// return with an error if it isn't one.
OlmMessage::Message(_) => {
warn!(
"Failed to decrypt a non-pre-key message with all
@ -736,7 +736,7 @@ impl OlmMachine {
}
OlmMessage::PreKey(m) => {
/// Create the new session.
// Create the new session.
let session = match self
.account
.create_inbound_session(sender_key, m.clone())
@ -753,32 +753,79 @@ impl OlmMachine {
}
};
/// Save the account since we remove the one-time key that
/// was used to create this session.
// Save the account since we remove the one-time key that
// was used to create this session.
self.store.save_account(self.account.clone()).await?;
session
}
};
/// Decrypt our message, this shouldn't fail since we're using a
/// newly created Session.
// Decrypt our message, this shouldn't fail since we're using a
// newly created Session.
let plaintext = session.decrypt(message).await?;
/// Save the new ratcheted state of the session.
// Save the new ratcheted state of the session.
self.store.save_session(session).await?;
plaintext
};
trace!("Successfully decrypted a Olm message: {}", plaintext);
// TODO get the recipient, recipient_keys, and keys out of here
// separately.
// TODO verify that the recipient, recipient_keys match with us.
// TODO verify that the sender in the decrypted event matches the one in
// the unencrypted one.
Ok(serde_json::from_str::<EventResult<ToDeviceEvent>>(
&plaintext,
)?)
Ok(self.parse_decrypted_to_device_event(sender, &plaintext)?)
}
fn parse_decrypted_to_device_event(
&self,
sender: &UserId,
plaintext: &str,
) -> Result<(EventResult<ToDeviceEvent>, String)> {
// TODO make the errors a bit more specific.
let decrypted_json: Value = serde_json::from_str(&plaintext)?;
let encrytped_sender = decrypted_json
.get("sender")
.cloned()
.ok_or(OlmError::MissingCiphertext)?;
let encrytped_sender: UserId = serde_json::from_value(encrytped_sender)?;
let recipient = decrypted_json
.get("recipient")
.cloned()
.ok_or(OlmError::MissingCiphertext)?;
let recipient: UserId = serde_json::from_value(recipient)?;
let recipient_keys: HashMap<KeyAlgorithm, String> = serde_json::from_value(
decrypted_json
.get("recipient_keys")
.cloned()
.ok_or(OlmError::MissingCiphertext)?,
)?;
let keys: HashMap<KeyAlgorithm, String> = serde_json::from_value(
decrypted_json
.get("keys")
.cloned()
.ok_or(OlmError::MissingCiphertext)?,
)?;
if recipient != self.user_id || sender != &encrytped_sender {
return Err(OlmError::MissingCiphertext);
}
if self.account.identity_keys().ed25519()
!= recipient_keys
.get(&KeyAlgorithm::Ed25519)
.ok_or(OlmError::MissingCiphertext)?
{
return Err(OlmError::MissingCiphertext);
}
let signing_key = keys
.get(&KeyAlgorithm::Ed25519)
.ok_or(OlmError::MissingSigningKey)?;
Ok((
serde_json::from_value::<EventResult<ToDeviceEvent>>(decrypted_json)?,
signing_key.to_owned(),
))
}
/// Decrypt a to-device event.
@ -820,16 +867,20 @@ impl OlmMachine {
.map_err(|_| OlmError::UnsupportedOlmType)?;
// Decrypt the OlmMessage and get a Ruma event out of it.
let mut decrypted_event = self
.decrypt_olm_message(&event.sender.to_string(), &content.sender_key, message)
let (mut decrypted_event, signing_key) = self
.decrypt_olm_message(&event.sender, &content.sender_key, message)
.await?;
debug!("Decrypted a to-device event {:?}", decrypted_event);
// Handle the decrypted event, e.g. fetch out megolm sessions out of
// the event.
self.handle_decrypted_to_device_event(&content.sender_key, &mut decrypted_event)
.await?;
self.handle_decrypted_to_device_event(
&content.sender_key,
&signing_key,
&mut decrypted_event,
)
.await?;
Ok(decrypted_event)
} else {
@ -838,14 +889,14 @@ impl OlmMachine {
}
}
async fn add_room_key(&mut self, sender_key: &str, event: &mut ToDeviceRoomKey) -> Result<()> {
async fn add_room_key(
&mut self,
sender_key: &str,
signing_key: &str,
event: &mut ToDeviceRoomKey,
) -> Result<()> {
match event.content.algorithm {
Algorithm::MegolmV1AesSha2 => {
let signing_key = event
.keys
.get("ed25519")
.ok_or(OlmError::MissingSigningKey)?;
let session_key = GroupSessionKey(mem::take(&mut event.content.session_key));
let session = InboundGroupSession::new(
@ -1101,6 +1152,7 @@ impl OlmMachine {
fn add_forwarded_room_key(
&self,
_sender_key: &str,
_signing_key: &str,
_event: &ToDeviceForwardedRoomKey,
) -> Result<()> {
Ok(())
@ -1110,6 +1162,7 @@ impl OlmMachine {
async fn handle_decrypted_to_device_event(
&mut self,
sender_key: &str,
signing_key: &str,
event: &mut EventResult<ToDeviceEvent>,
) -> Result<()> {
let event = if let EventResult::Ok(e) = event {
@ -1120,8 +1173,10 @@ impl OlmMachine {
};
match event {
ToDeviceEvent::RoomKey(e) => self.add_room_key(sender_key, e).await,
ToDeviceEvent::ForwardedRoomKey(e) => self.add_forwarded_room_key(sender_key, e),
ToDeviceEvent::RoomKey(e) => self.add_room_key(sender_key, signing_key, e).await,
ToDeviceEvent::ForwardedRoomKey(e) => {
self.add_forwarded_room_key(sender_key, signing_key, e)
}
_ => {
warn!("Received a unexpected encrypted to-device event");
Ok(())