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fix: apply_group_changes(): Forbid membership changes from possible non-members (#3782)

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It can be not good for membership consistency if we missed a message adding a member, but improves
security because nobody can add themselves to a group from now on.
This commit is contained in:
iequidoo
2023-09-10 21:20:26 -03:00
committed by iequidoo
parent 7a359f6318
commit 9bd7ab7280
2 changed files with 28 additions and 16 deletions
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30
src/receive_imf.rs
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@@ -1665,17 +1665,19 @@ async fn apply_group_changes(
false
};
// Whether to allow any changes to the member list at all. Just reject old group changes.
let allow_member_list_changes = chat_id
.update_timestamp(context, Param::MemberListTimestamp, sent_timestamp)
.await?;
let is_from_in_chat = !chat::is_contact_in_chat(context, chat_id, ContactId::SELF).await?
|| chat::is_contact_in_chat(context, chat_id, from_id).await?;
let is_from_in_chat = chat::is_contact_in_chat(context, chat_id, from_id).await?;
// Reject group membership changes from non-members and old changes.
let allow_member_list_changes = is_from_in_chat
&& chat_id
.update_timestamp(context, Param::MemberListTimestamp, sent_timestamp)
.await?;
// Whether to rebuild the member list from scratch.
let recreate_member_list = allow_member_list_changes && {
let recreate_member_list = {
// Recreate member list if the message comes from a MUA as these messages do _not_ set add/remove headers.
(is_from_in_chat && !mime_parser.has_chat_version())
!mime_parser.has_chat_version()
// Always recreate membership list if SELF has been added. The older versions of DC
// don't always set "In-Reply-To" to the latest message they sent, but to the latest
// delivered message (so it's a race), so we have this heuristic here.
@@ -1686,6 +1688,14 @@ async fn apply_group_changes(
Some(reply_to) => rfc724_mid_exists(context, reply_to).await?.is_none(),
None => false,
}
} && {
if !allow_member_list_changes {
info!(
context,
"Ignoring a try to recreate member list of {chat_id} by {from_id}.",
);
}
allow_member_list_changes
};
if let Some(removed_addr) = mime_parser.get_header(HeaderDef::ChatGroupMemberRemoved) {
@@ -1792,12 +1802,6 @@ async fn apply_group_changes(
// Recreate the member list.
if recreate_member_list {
if !is_from_in_chat {
warn!(
context,
"Contact {from_id} modifies group chat {chat_id} member list possibly not being a member."
);
}
// Only delete old contacts if the sender is not a classical MUA user:
// Classical MUA users usually don't intend to remove users from an email
// thread, so if they removed a recipient then it was probably by accident.