If multiple headers with the same name are present,
we must take the last one.
This is the one that is DKIM-signed if
this header is DKIM-signed at all.
Ideally servers should prevent adding
more From, To and Cc headers by oversigning
them, but unfortunately it is not common
and OpenDKIM in its default configuration
does not oversign any headers.
This protects Bob (the joiner) of sending unexpected-unencrypted messages during an otherwise nicely
running SecureJoin.
If things get stuck, however, we do not want to block communication -- the chat is just
opportunistic as usual, but that needs to be communicated:
1. If Bob's chat with Alice is `Unprotected` and a SecureJoin is started, then add info-message
"Establishing guaranteed end-to-end encryption, please wait..." and let `Chat::can_send()` return
`false`.
2. Once the info-message "Messages are guaranteed to be e2ee from now on" is added, let
`Chat::can_send()` return `true`.
3. If after SECUREJOIN_WAIT_TIMEOUT seconds `2.` did not happen, add another info-message "Could not
yet establish guaranteed end-to-end encryption but you may already send a message" and also let
`Chat::can_send()` return `true`.
Both `2.` and `3.` require the event `ChatModified` being sent out so that UI pick up the change wrt
`Chat::can_send()` (this is the same way how groups become updated wrt `can_send()` changes).
SECUREJOIN_WAIT_TIMEOUT should be 10-20 seconds so that we are reasonably sure that the app remains
active and receiving also on mobile devices. If the app is killed during this time then we may need
to do step 3 for any pending Bob-join chats (right now, Bob can only join one chat at a time).
`a.clone_from(&b)` is equivalent to `a = b.clone()` in functionality,
but can be overridden to reuse the resources of a to avoid unnecessary
allocations.
Let's add a 1-minute tolerance to `Params::MemberListTimestamp`.
This adds to the group membership consistency algo the following properties:
- If remote group membership changes were made by two members in parallel, both of them are applied,
no matter in which order the messages are received.
- If we remove a member locally, only explicit remote member additions/removals made in parallel are
allowed, but not the synchronisation of the member list from "To". Before, if somebody managed to
reply earlier than receiving our removal of a member, we added it back which doesn't look good.
If Subject is multiline-formatted, `mailparse` adds the leading whitespace to it. The solution is to
always remove the leading whitespace, because if Subject isn't multiline-formatted, it never
contains the leading whitespace anyway. But as for the trailing whitespace -- i checked -- it's
never removed, so let's keep this as is.
Before group avatar was sent as an attachment. Let's do the same as with user avatar and send group
avatar as base64. Receiver code uses the same functions for user and chat avatars, so base64 avatars
are supported for most receivers already.
Use sync messages for that as it is done for e.g. Config::Displayname. Maybe we need to remove
avatar synchronisation via usual messages then, but let's think of it a bit.
Currently when a user sets up another device by logging in, a new key is created. If a message is
sent from either device outside, it cannot be decrypted by the other device.
The message is replaced with square bracket error like this:
```
<string name="systemmsg_cannot_decrypt">This message cannot be decrypted.\n\n• It might already help to simply reply to this message and ask the sender to send the message again.\n\n• If you just re-installed Delta Chat then it is best if you re-setup Delta Chat now and choose "Add as second device" or import a backup.</string>
```
(taken from Android repo `res/values/strings.xml`)
If the message is outgoing, it does not help to "simply reply to this message". Instead, we should
add a translatable device message of a special type so UI can link to the FAQ entry about second
device. But let's limit such notifications to 1 per day. And as for the undecryptable message
itself, let it go to Trash if it can't be assigned to a chat by its references.
"Auto-Submitted: auto-replied" messages mustn't be considered as sent by either bots or non-bots,
e.g. MDNs have this header value and it's the same for bots and non-bots.
In particular TLSRPT reports
contain files that may be interesting for admins.
Currently Delta Chat drops the attachment
so message appears as a text message without actual payload.
Before this fix actual contents of the message
reposted by Schleuder is considered a mailing list footer and removed,
not visible even in the "Show Full Message..." view.
With this change there will be two message bubbles,
one for header and one for the contents,
but it is still better than losing the contents completely.
Attempting to parse header part is out of scope for this change.
Before in some places it was correctly calculated by passing the "sent" timestamp to
`calc_sort_timestamp()`, but in other places just the system time was used. In some complex
scenarios like #5088 (restoration of a backup made before a contact verification) it led to wrong
sort timestamps of protection messages and also messages following by them.
But to reduce number of args passed to functions needing to calculate the sort timestamp, add
message timestamps to `struct MimeMessage` which is anyway passed everywhere.
parse_mime_recursive() skips empty text parts,
so there may be no parts as the result of parsing.
In this case an empty part is added.
However, because it is added with parts.push()
rather than add_single_part(),
it is added without a padlock even if the message is encrypted.
`do_add_single_part()` adds padlock (GuaranteeE2EE param)
and should be used to add parts instead.
- Remove "Detected Autocrypt-mime message" logs printed for every incoming Autocrypt message.
- Print only a single line at the beginning of receive_imf with both the Message-ID and seen flag.
- Print Securejoin step only once, inside handle_securejoin_handshake or observe_securejoin_on_other_device.
- Do not log "Not creating ad-hoc group" every time ad-hoc group is not created, log when it is created instead.
- Log ID of the chat where Autocrypt-Gossip for all members is received.
- Do not print "Secure-join requested." for {vg,vc}-request, we already log the step.
- Remove ">>>>>>>>>>>>>>>>>>>>>>>>>" noise from securejoin logs.
If a message is encrypted, but unsigned:
- Don't set `MimeMessage::from_is_signed`.
- Remove "secure-join-fingerprint" and "chat-verified" headers from `MimeMessage`.
- Minor: Preserve "Subject" from the unencrypted top level if there's no "Subject" in the encrypted
part, this message is displayed w/o a padlock anyway.
Apparently it didn't lead to any vulnerabilities because there are checks for
`MimeMessage::signatures.is_empty()` in all necessary places, but still the code looked dangerous,
especially because `from_is_singed` var name didn't correspond to its actual value (it was rather
`from_is_encrypted_maybe_signed`).
This message makes that partial messages do not change the group state.
A simple fix and a comprehensive test is added. This is a follow up to
the former #4841 which took a different approach.
And execute sync messages only if `Config::SyncMsgs` is enabled. Earlier executing was always
enabled, the messages are force-encrypted anyway. But for users it's probably more clear whether a
device is synchronised or not.
