fix: Auto-restore 1:1 chat protection if contact is only forward verified

Follow-up to 3f1dfef0e7. Forward verification is sufficient to have
the 1:1 chat protected, backwards verification is needed to add the contact to verified groups.

src/receive_imf.rs

@@ -1010,7 +1010,7 @@ async fn add_parts(
                             && peerstate.prefer_encrypt == EncryptPreference::Mutual
                             // Check that the contact still has the Autocrypt key same as the
                             // verified key, see also `Peerstate::is_using_verified_key()`.
-                            && contact.is_verified(context).await?;
+                            && contact.is_forward_verified(context).await?;
                     }
                 }
             }

src/test_utils.rs

@@ -1171,29 +1171,42 @@ fn print_logevent(logevent: &LogEvent) {
 }
 
 /// Saves the other account's public key as verified
-/// and peerstate as backwards verified.
-pub(crate) async fn mark_as_verified(this: &TestContext, other: &TestContext) {
+/// and peerstate as backwards verified / not verified.
+pub(crate) async fn mark_as_verified_ex(
+    this: &TestContext,
+    other: &TestContext,
+    last_seen: i64,
+    backward: bool,
+) {
     let mut peerstate = Peerstate::from_header(
         &EncryptHelper::new(other).await.unwrap().get_aheader(),
-        // We have to give 0 as the time, not the current time:
-        // The time is going to be saved in peerstate.last_seen.
-        // The code in `peerstate.rs` then compares `if message_time > self.last_seen`,
-        // and many similar checks in peerstate.rs, and doesn't allow changes otherwise.
-        // Giving the current time would mean that message_time == peerstate.last_seen,
-        // so changes would not be allowed.
-        // This might lead to flaky tests.
-        0,
+        last_seen,
     );
 
     peerstate.verified_key.clone_from(&peerstate.public_key);
     peerstate
         .verified_key_fingerprint
         .clone_from(&peerstate.public_key_fingerprint);
-    peerstate.backward_verified_key_id = Some(this.get_config_i64(Config::KeyId).await.unwrap());
-
+    peerstate.backward_verified_key_id = match backward {
+        true => Some(this.get_config_i64(Config::KeyId).await.unwrap()),
+        false => None,
+    };
     peerstate.save_to_db(&this.sql).await.unwrap();
 }
 
+/// Saves the other account's public key as verified
+/// and peerstate as backwards verified.
+pub(crate) async fn mark_as_verified(this: &TestContext, other: &TestContext) {
+    // We have to give 0 as the time, not the current time: The time is going to be saved in
+    // peerstate.last_seen. The code in `peerstate.rs` then compares `if message_time >
+    // self.last_seen`, and many similar checks in peerstate.rs, and doesn't allow changes
+    // otherwise. Giving the current time would mean that message_time == peerstate.last_seen, so
+    // changes would not be allowed. This might lead to flaky tests.
+    let last_seen = 0;
+    let backward = true;
+    mark_as_verified_ex(this, other, last_seen, backward).await
+}
+
 /// Pops a sync message from alice0 and receives it on alice1. Should be used after an action on
 /// alice0's side that implies sending a sync message.
 pub(crate) async fn sync(alice0: &TestContext, alice1: &TestContext) {

src/tests/verified_chats.rs

@@ -11,8 +11,10 @@ use crate::mimefactory::MimeFactory;
 use crate::mimeparser::SystemMessage;
 use crate::receive_imf::receive_imf;
 use crate::stock_str;
-use crate::test_utils::{get_chat_msg, mark_as_verified, TestContext, TestContextManager};
-use crate::tools::SystemTime;
+use crate::test_utils::{
+    get_chat_msg, mark_as_verified, mark_as_verified_ex, TestContext, TestContextManager,
+};
+use crate::tools::{time, SystemTime};
 use crate::{e2ee, message};
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
@@ -754,11 +756,16 @@ async fn test_message_from_old_dc_setup() -> Result<()> {
     tcm.send_recv(bob, alice, "Now i have it!").await;
     assert_verified(alice, bob, ProtectionStatus::Protected).await;
 
+    // Forward verification should be sufficient to keep the chat protected.
+    let backward = false;
+    mark_as_verified_ex(alice, bob, time() - 1, backward).await;
+
     let msg = alice.recv_msg(&sent_old).await;
     assert!(!msg.get_showpadlock());
     let contact = alice.add_or_lookup_contact(bob).await;
     // The outdated Bob's Autocrypt header isn't applied, so the verification preserves.
-    assert!(contact.is_verified(alice).await.unwrap());
+    assert!(contact.is_forward_verified(alice).await.unwrap());
+    assert!(!contact.is_verified(alice).await.unwrap());
     let chat = alice.get_chat(bob).await;
     assert!(chat.is_protected());
     assert_eq!(chat.is_protection_broken(), false);