fix: never encrypt {vc,vg}-request

Even if 1:1 chat with alice is protected,
we should send vc-request unencrypted.
This happens if Alice changed the key
and QR-code Bob scans contains fingerprint
that is different from the verified fingerprint.
Sending vc-request encrypted to the old key
does not help because Alice is not able
to decrypt it in this case.

deltachat-rpc-client/tests/test_securejoin.py

@@ -164,6 +164,21 @@ def test_qr_readreceipt(acfactory) -> None:
     assert not bob.get_chat_by_contact(bob_contact_charlie)
 
 
+def test_setup_contact_resetup(acfactory) -> None:
+    """Tests that setup contact works after Alice resets the device and changes the key."""
+    alice, bob = acfactory.get_online_accounts(2)
+
+    qr_code, _svg = alice.get_qr_code()
+    bob.secure_join(qr_code)
+    bob.wait_for_securejoin_joiner_success()
+
+    alice = acfactory.resetup_account(alice)
+
+    qr_code, _svg = alice.get_qr_code()
+    bob.secure_join(qr_code)
+    bob.wait_for_securejoin_joiner_success()
+
+
 def test_verified_group_recovery(acfactory) -> None:
     """Tests verified group recovery by reverifying a member and sending a message in a group."""
     ac1, ac2, ac3 = acfactory.get_online_accounts(3)

src/mimefactory.rs

@@ -338,18 +338,11 @@ impl<'a> MimeFactory<'a> {
     fn should_force_plaintext(&self) -> bool {
         match &self.loaded {
             Loaded::Message { chat } => {
-                if chat.is_protected() {
-                    false
-                } else if chat.typ == Chattype::Broadcast {
-                    // encryption may disclose recipients;
-                    // this is probably a worse issue than not opportunistically (!) encrypting
-                    true
-                } else {
-                    self.msg
-                        .param
-                        .get_bool(Param::ForcePlaintext)
-                        .unwrap_or_default()
-                }
+                self.msg
+                    .param
+                    .get_bool(Param::ForcePlaintext)
+                    .unwrap_or_default()
+                    || chat.typ == Chattype::Broadcast
             }
             Loaded::Mdn { .. } => false,
         }