Add dc_get_chat_encrinfo()

deltachat-ffi/deltachat.h

@@ -1220,6 +1220,18 @@ void            dc_delete_chat               (dc_context_t* context, uint32_t ch
  */
 dc_array_t*     dc_get_chat_contacts         (dc_context_t* context, uint32_t chat_id);
 
+/**
+ * Get encryption info for a chat.
+ * Get a multi-line encryption info, containing encryption preferences of all members.
+ * Can be used to find out why messages sent to group are not encrypted.
+ *
+ * @memberof dc_context_t
+ * @param context The context object.
+ * @param chat_id ID of the chat to get the encryption info for.
+ * @return Multi-line text, must be released using dc_str_unref() after usage.
+ */
+char*           dc_get_chat_encrinfo (dc_context_t* context, uint32_t chat_id);
+
 /**
  * Get the chat's ephemeral message timer.
  * The ephemeral message timer is set by dc_set_chat_ephemeral_timer()

deltachat-ffi/src/lib.rs

@@ -1322,6 +1322,29 @@ pub unsafe extern "C" fn dc_set_chat_mute_duration(
     })
 }
 
+#[no_mangle]
+pub unsafe extern "C" fn dc_get_chat_encrinfo(
+    context: *mut dc_context_t,
+    chat_id: u32,
+) -> *mut libc::c_char {
+    if context.is_null() {
+        eprintln!("ignoring careless call to dc_get_chat_encrinfo()");
+        return "".strdup();
+    }
+    let ctx = &*context;
+
+    block_on(async move {
+        ChatId::new(chat_id)
+            .get_encryption_info(&ctx)
+            .await
+            .map(|s| s.strdup())
+            .unwrap_or_else(|e| {
+                error!(&ctx, "{}", e);
+                ptr::null_mut()
+            })
+    })
+}
+
 #[no_mangle]
 pub unsafe extern "C" fn dc_get_chat_ephemeral_timer(
     context: *mut dc_context_t,

python/src/deltachat/chat.py

@@ -167,6 +167,13 @@ class Chat(object):
         """
         return lib.dc_chat_get_type(self._dc_chat)
 
+    def get_encryption_info(self):
+        """Return encryption info for this chat.
+
+        :returns: a string with encryption preferences of all chat members"""
+        res = lib.dc_get_chat_encrinfo(self.account._dc_context, self.id)
+        return from_dc_charpointer(res)
+
     def get_join_qr(self):
         """ get/create Join-Group QR Code as ascii-string.
 

python/tests/test_account.py

@@ -1130,6 +1130,7 @@ class TestOnlineAccount:
         msg = ac1._evtracker.wait_next_incoming_message()
         assert msg.text == "first message"
         assert not msg.is_encrypted()
+        assert msg.chat.get_encryption_info() == f"{ac2.get_config('addr')} End-to-end encryption preferred."
 
         lp.sec("ac2 learns that ac3 prefers encryption")
         ac2.create_chat(ac3)
@@ -1141,6 +1142,7 @@ class TestOnlineAccount:
         lp.sec("ac3 does not know that ac1 prefers encryption")
         ac1.create_chat(ac3)
         chat = ac3.create_chat(ac1)
+        assert chat.get_encryption_info() == f"{ac1.get_config('addr')} No encryption."
         msg = chat.send_text("not encrypted")
         msg = ac1._evtracker.wait_next_incoming_message()
         assert msg.text == "not encrypted"
@@ -1149,6 +1151,8 @@ class TestOnlineAccount:
         lp.sec("ac1 creates a group chat with ac2")
         group_chat = ac1.create_group_chat("hello")
         group_chat.add_contact(ac2)
+        encryption_info = group_chat.get_encryption_info()
+        assert encryption_info == f"{ac2.get_config('addr')} End-to-end encryption preferred."
         msg = group_chat.send_text("hi")
 
         msg = ac2._evtracker.wait_next_incoming_message()
@@ -1161,6 +1165,9 @@ class TestOnlineAccount:
 
         lp.sec("ac3 learns that ac1 prefers encryption")
         msg = ac3._evtracker.wait_next_incoming_message()
+        encryption_info = msg.chat.get_encryption_info().splitlines()
+        assert f"{ac1.get_config('addr')} End-to-end encryption preferred." in encryption_info
+        assert f"{ac2.get_config('addr')} End-to-end encryption preferred." in encryption_info
         msg = chat.send_text("encrypted")
         assert msg.is_encrypted()
 

src/chat.rs

@@ -12,6 +12,7 @@ use itertools::Itertools;
 use num_traits::FromPrimitive;
 use serde::{Deserialize, Serialize};
 
+use crate::aheader::EncryptPreference;
 use crate::blob::{BlobError, BlobObject};
 use crate::chatlist::dc_get_archived_cnt;
 use crate::config::Config;
@@ -35,6 +36,7 @@ use crate::job::{self, Action};
 use crate::message::{self, InvalidMsgId, Message, MessageState, MsgId};
 use crate::mimeparser::SystemMessage;
 use crate::param::{Param, Params};
+use crate::peerstate::{Peerstate, PeerstateVerifiedStatus};
 use crate::sql;
 use crate::stock::StockMessage;
 
@@ -637,6 +639,47 @@ impl ChatId {
         }
     }
 
+    /// Returns multi-line text summary of encryption preferences of all chat contacts.
+    ///
+    /// This can be used to find out if encryption is not available because
+    /// keys for some users are missing or simply because the majority of the users in a group
+    /// prefer plaintext emails.
+    ///
+    /// To get more verbose summary for a contact, including its key fingerprint, use [`Contact::get_encrinfo`].
+    pub async fn get_encryption_info(self, context: &Context) -> Result<String, Error> {
+        let mut ret = String::new();
+
+        for contact_id in get_chat_contacts(context, self)
+            .await
+            .iter()
+            .filter(|&contact_id| *contact_id > DC_CONTACT_ID_LAST_SPECIAL)
+        {
+            let contact = Contact::load_from_db(context, *contact_id).await?;
+            let addr = contact.get_addr();
+            let peerstate = Peerstate::from_addr(context, addr).await?;
+
+            let stock_message = peerstate
+                .filter(|peerstate| {
+                    peerstate
+                        .peek_key(PeerstateVerifiedStatus::Unverified)
+                        .is_some()
+                })
+                .map(|peerstate| match peerstate.prefer_encrypt {
+                    EncryptPreference::Mutual => StockMessage::E2ePreferred,
+                    EncryptPreference::NoPreference => StockMessage::E2eAvailable,
+                    EncryptPreference::Reset => StockMessage::EncrNone,
+                })
+                .unwrap_or(StockMessage::EncrNone);
+
+            if !ret.is_empty() {
+                ret.push('\n')
+            }
+            ret += &format!("{} {}", addr, context.stock_str(stock_message).await);
+        }
+
+        Ok(ret)
+    }
+
     /// Bad evil escape hatch.
     ///
     /// Avoid using this, eventually types should be cleaned up enough