Do not assign group IDs to ad hoc groups

CHANGELOG.md

@@ -29,6 +29,7 @@
 - mark messages as seen on IMAP in batches #3223
 - remove Received: based draft detection heuristic #3230
 - Use pkgconfig for building Python package #2590
+- Do not assign group IDs to ad-hoc groups #2798
 
 
 ## 1.77.0

src/dc_receive_imf.rs

@@ -9,7 +9,6 @@ use mailparse::{parse_mail, SingleInfo};
 use num_traits::FromPrimitive;
 use once_cell::sync::Lazy;
 use regex::Regex;
-use sha2::{Digest, Sha256};
 
 use crate::chat::{self, Chat, ChatId, ChatIdBlocked, ProtectionStatus};
 use crate::config::Config;
@@ -1925,9 +1924,6 @@ async fn create_adhoc_group(
         return Ok(None);
     }
 
-    // Create a new ad-hoc group.
-    let grpid = create_adhoc_grp_id(context, member_ids).await?;
-
     // use subject as initial chat name
     let grpname = mime_parser
         .get_subject()
@@ -1936,7 +1932,7 @@ async fn create_adhoc_group(
     let new_chat_id: ChatId = ChatId::create_multiuser_record(
         context,
         Chattype::Group,
-        &grpid,
+        "", // Ad hoc groups have no ID.
         &grpname,
         create_blocked,
         ProtectionStatus::Unprotected,
@@ -1952,56 +1948,6 @@ async fn create_adhoc_group(
     Ok(Some(new_chat_id))
 }
 
-/// Creates ad-hoc group ID.
-///
-/// Algorithm:
-/// - sort normalized, lowercased, e-mail addresses alphabetically
-/// - put all e-mail addresses into a single string, separate the address by a single comma
-/// - sha-256 this string (without possibly terminating null-characters)
-/// - encode the first 64 bits of the sha-256 output as lowercase hex (results in 16 characters from the set [0-9a-f])
-///
-/// This ensures that different Delta Chat clients generate the same group ID unless some of them
-/// are hidden in BCC. This group ID is sent by DC in the messages sent to this chat,
-/// so having the same ID prevents group split.
-async fn create_adhoc_grp_id(context: &Context, member_ids: &[ContactId]) -> Result<String> {
-    let member_cs = context.get_primary_self_addr().await?.to_lowercase();
-    let query = format!(
-        "SELECT addr FROM contacts WHERE id IN({}) AND id!=?",
-        sql::repeat_vars(member_ids.len())
-    );
-    let mut params = Vec::new();
-    params.extend_from_slice(member_ids);
-    params.push(ContactId::SELF);
-
-    let members = context
-        .sql
-        .query_map(
-            query,
-            rusqlite::params_from_iter(params),
-            |row| row.get::<_, String>(0),
-            |rows| {
-                let mut addrs = rows.collect::<std::result::Result<Vec<_>, _>>()?;
-                addrs.sort();
-                let mut acc = member_cs.clone();
-                for addr in &addrs {
-                    acc += ",";
-                    acc += &addr.to_lowercase();
-                }
-                Ok(acc)
-            },
-        )
-        .await?;
-
-    Ok(hex_hash(&members))
-}
-
-#[allow(clippy::indexing_slicing)]
-fn hex_hash(s: &str) -> String {
-    let bytes = s.as_bytes();
-    let result = Sha256::digest(bytes);
-    hex::encode(&result[..8])
-}
-
 async fn check_verified_properties(
     context: &Context,
     mimeparser: &MimeMessage,
@@ -2272,14 +2218,6 @@ mod tests {
     use crate::message::Message;
     use crate::test_utils::{get_chat_msg, TestContext, TestContextManager};
 
-    #[test]
-    fn test_hex_hash() {
-        let data = "hello world";
-
-        let res = hex_hash(data);
-        assert_eq!(res, "b94d27b9934d3e08");
-    }
-
     #[async_std::test]
     async fn test_grpid_simple() {
         let context = TestContext::new().await;
@@ -4589,6 +4527,30 @@ Second thread."#;
         let bob_second_reply = bob.get_last_msg().await;
         assert_eq!(bob_second_reply.chat_id, bob_second_msg.chat_id);
 
+        // Alice adds Fiona to both ad hoc groups.
+        let fiona = TestContext::new_fiona().await;
+        let (alice_fiona_contact_id, _) = Contact::add_or_lookup(
+            &alice,
+            "Fiona",
+            "fiona@example.net",
+            Origin::IncomingUnknownTo,
+        )
+        .await?;
+
+        chat::add_contact_to_chat(&alice, alice_first_msg.chat_id, alice_fiona_contact_id).await?;
+        let alice_first_invite = alice.pop_sent_msg().await;
+        fiona.recv_msg(&alice_first_invite).await;
+        let fiona_first_invite = fiona.get_last_msg().await;
+
+        chat::add_contact_to_chat(&alice, alice_second_msg.chat_id, alice_fiona_contact_id).await?;
+        let alice_second_invite = alice.pop_sent_msg().await;
+        fiona.recv_msg(&alice_second_invite).await;
+        let fiona_second_invite = fiona.get_last_msg().await;
+
+        // Fiona was added to two separate chats and should see two separate chats, even though they
+        // don't have different group IDs to distinguish them.
+        assert!(fiona_first_invite.chat_id != fiona_second_invite.chat_id);
+
         Ok(())
     }
 

src/mimefactory.rs

@@ -850,9 +850,12 @@ impl<'a> MimeFactory<'a> {
         }
 
         if chat.typ == Chattype::Group {
+            // Send group ID unless it is an ad hoc group that has no ID.
+            if !chat.grpid.is_empty() {
                 headers
                     .protected
                     .push(Header::new("Chat-Group-ID".into(), chat.grpid.clone()));
+            }
 
             let encoded = encode_words(&chat.name);
             headers

src/test_utils.rs

@@ -88,6 +88,13 @@ impl TestContextBuilder {
         self.with_key_pair(bob_keypair())
     }
 
+    /// Configures as fiona@example.net with fixed secret key.
+    ///
+    /// This is a shortcut for `.with_key_pair(bob_keypair()).
+    pub fn configure_fiona(self) -> Self {
+        self.with_key_pair(fiona_keypair())
+    }
+
     /// Configures the new [`TestContext`] with the provided [`KeyPair`].
     ///
     /// This will extract the email address from the key and configure the context with the
@@ -183,6 +190,13 @@ impl TestContext {
         Self::builder().configure_bob().build().await
     }
 
+    /// Creates a new configured [`TestContext`].
+    ///
+    /// This is a shortcut which configures fiona@example.net with a fixed key.
+    pub async fn new_fiona() -> Self {
+        Self::builder().configure_fiona().build().await
+    }
+
     /// Internal constructor.
     ///
     /// `name` is used to identify this context in e.g. log output.  This is useful mostly
@@ -691,6 +705,24 @@ pub fn bob_keypair() -> KeyPair {
     }
 }
 
+/// Load a pre-generated keypair for fiona@example.net from disk.
+///
+/// Like [alice_keypair] but a different key and identity.
+pub fn fiona_keypair() -> key::KeyPair {
+    let addr = EmailAddress::new("fiona@example.net").unwrap();
+    let public = key::SignedPublicKey::from_asc(include_str!("../test-data/key/fiona-public.asc"))
+        .unwrap()
+        .0;
+    let secret = key::SignedSecretKey::from_asc(include_str!("../test-data/key/fiona-secret.asc"))
+        .unwrap()
+        .0;
+    key::KeyPair {
+        addr,
+        public,
+        secret,
+    }
+}
+
 /// Utility to help wait for and retrieve events.
 ///
 /// This buffers the events in order they are emitted.  This allows consuming events in