Do not send Done message after receiving a Done

Done messages are supposed to indicate that the verification was
successful and _can be_ finalized. The correct time to send Done events
is after the user has confirmed the verification (after checking the
emoji or similar) and after receiving and checking a mac from the other
party (whatever happens later). Waiting for the other side to send Done
before sending it ourselves does not make sense.

Author: ftilde

crates/matrix-sdk-crypto/src/verification/mod.rs

@@ -31,6 +31,10 @@ use matrix_sdk_common::locks::Mutex;
 #[cfg(feature = "qrcode")]
 pub use qrcode::{QrVerification, ScanError};
 pub use requests::VerificationRequest;
+#[cfg(feature = "qrcode")]
+use ruma::events::key::verification::done::{
+    KeyVerificationDoneEventContent, ToDeviceKeyVerificationDoneEventContent,
+};
 use ruma::{
     api::client::r0::keys::upload_signatures::Request as SignatureUploadRequest,
     events::{
@@ -39,7 +43,6 @@ use ruma::{
                 CancelCode, KeyVerificationCancelEventContent,
                 ToDeviceKeyVerificationCancelEventContent,
             },
-            done::{KeyVerificationDoneEventContent, ToDeviceKeyVerificationDoneEventContent},
             Relation,
         },
         AnyMessageEventContent, AnyToDeviceEventContent,
@@ -243,6 +246,7 @@ pub struct Done {
 }
 
 impl Done {
+    #[cfg(feature = "qrcode")]
     pub fn as_content(&self, flow_id: &FlowId) -> OutgoingContent {
         match flow_id {
             FlowId::ToDevice(t) => AnyToDeviceEventContent::KeyVerificationDone(

crates/matrix-sdk-crypto/src/verification/sas/inner_sas.rs

@@ -335,10 +335,7 @@ impl InnerSas {
             },
             AnyVerificationContent::Done(c) => match self {
                 InnerSas::WaitingForDone(s) => match s.into_done(sender, c) {
-                    Ok(s) => {
-                        let content = s.done_content();
-                        (InnerSas::Done(s), Some(content))
-                    }
+                    Ok(s) => (InnerSas::Done(s), None),
                     Err(s) => {
                         let content = s.as_content();
                         (InnerSas::Cancelled(s), Some(content))

crates/matrix-sdk-crypto/src/verification/sas/sas_state.rs

@@ -1177,10 +1177,6 @@ impl SasState<Done> {
         get_mac_content(&self.inner.lock().unwrap(), &self.ids, &self.verification_flow_id)
     }
 
-    pub fn done_content(&self) -> OutgoingContent {
-        self.state.as_content(self.verification_flow_id.as_ref())
-    }
-
     /// Get the list of verified devices.
     pub fn verified_devices(&self) -> Arc<[ReadOnlyDevice]> {
         self.state.verified_devices.clone()