Can be reviewed commit-by-commit.
This fixes another silly thing you can do with securejoinv3: show Bob a
QR code with auth token that is a broadcast channel secret of a known
channel, then never respond. Bob will decrypt messages from the channel
and drop them because they are sent by the "wrong" sender.
This can be avoided with domain separation, instead of
encrypting/decrypting securejoinv3 messages directly with auth token,
encrypt/decrypt them with `securejoin/<auth token>` as the secret or
even `securejoinv3/<alice's fingerprint>/<auth token>`. For existing
broadcast channels we cannot do this, but for securejoinv3 that is not
released yet this looks like an improvement that avoids at least this
problem.
Credits to link2xt for noticing the problem.
This also adds Alice's fingerprint to the auth tokens, which
was pretty easy to do. I find it hard to develop an intuition for
whether this is important, or whether we will be annoyed by it in the
future.
**Note:** This means that QR code scans will not work if one of the chat
partners uses a self-compiled core between c724e2981 and merging this PR
here. This is fine; we will just have to tell the other developers to
update their self-compiled cores.
The tests were originally generated with AI and then reworked.
Follow-up to https://github.com/chatmail/core/pull/7754 (c724e29)
This prevents the following attack:
/// Eve is subscribed to a channel and wants to know whether Alice is also subscribed to it.
/// To achieve this, Eve sends a message to Alice
/// encrypted with the symmetric secret of this broadcast channel.
///
/// If Alice sends an answer (or read receipt),
/// then Eve knows that Alice is in the broadcast channel.
///
/// A similar attack would be possible with auth tokens
/// that are also used to symmetrically encrypt messages.
///
/// To prevent this, a message that was unexpectedly
/// encrypted with a symmetric secret must be dropped.
Don't use first-person form in placeholder texts,
as these can be misleading when broadcasted to group.
Additionally ensures that broadcasted system messages
are not localized to not leak locally-set language
to the group chat.
Fixes#7930
Signed-off-by: Jagoda Ślązak <jslazak@jslazak.com>
Close https://github.com/chatmail/core/issues/7396. Before reviewing,
you should read the issue description of
https://github.com/chatmail/core/issues/7396.
I recommend to review with hidden whitespace changes.
TODO:
- [x] Implement the new protocol
- [x] Make Rust tests pass
- [x] Make Python tests pass
- [x] Test it manually on a phone
- [x] Print the sent messages, and check that they look how they should:
[test_secure_join_group_with_mime_printed.txt](https://github.com/user-attachments/files/24800556/test_secure_join_group.txt)
- [x] Fix bug: If Alice has a second device, then Bob's chat won't be
shown yet on that second device. Also, Bob's contact isn't shown in her
contact list. As soon as either party writes something into the chat,
the that shows up and everything is fine. All of this is still a way
better UX than in WhatsApp, where Bob always has to write first 😂
Still, I should fix that.
- This is actually caused by a larger bug: AUTH tokens aren't synced if
there is no corresponding INVITE token.
- Fixed by 6b658a0e0
- [x] Either make a new `auth_tokens` table with a proper UNIQUE bound,
or put a UNIQUE bound on the `tokens` table
- [x] Benchmarking
- [x] TODOs in the code, maybe change naming of the new functions
- [x] Write test for interop with older DC (esp. that the original
securejoin runs if you remove the &v=3 param)
- [x] From a cryptography perspective, is it fine that vc-request is
encrypted with AUTH, rather than a separate secret (like INVITE)?
- [x] Make sure that QR codes without INVITE work, so that we can remove
it eventually
- [x] Self-review, and comment on some of my code changes to explain
what they do
- [x] ~~Maybe use a new table rather than reusing AUTH token.~~ See
https://github.com/chatmail/core/pull/7754#discussion_r2728544725
- [ ] Update documentation; I'll do that in a separate PR. All necessary
information is in the https://github.com/chatmail/core/issues/7396 issue
description
- [ ] Update tests and other code to use the new names (e.g.
`request-pubkey` rather than `request` and `pubkey` rather than
`auth-required`); I'll do that in a follow-up PR
**Backwards compatibility:**
Everything works seamlessly in my tests. If both devices are updated,
then the new protocol is used; otherwise, the old protocol is used. If
there is a not-yet-updated second device, it will correctly observe the
protocol, and mark the chat partner as verified.
Note that I removed the `Auto-Submitted: auto-replied` header from
securejoin messages. We don't need it ourselves, it's a cleartext header
that leaks too much information, and I can't see any reason to have it.
---------
Co-authored-by: iequidoo <117991069+iequidoo@users.noreply.github.com>
fix https://github.com/chatmail/core/issues/7766
Implementation notes:
- Descriptions are only sent with member additions, when the description
is changed, and when promoting a previously-unpromoted group, in order
not to waste bandwith.
- Descriptions are not loaded everytime a chat object is loaded, because
they are only needed for the profile. Instead, they are in their own
table, and can be loaded with their own JsonRPC call.
---------
Co-authored-by: iequidoo <117991069+iequidoo@users.noreply.github.com>
This includes forwarding of long messages. Also this fixes sending, but more likely resending of
forwarded messages for which the original message was deleted, because now we save HTML to the db
immediately when creating a forwarded message.
Co-authored-by: Hocuri <hocuri@gmx.de>
This PR fixes a bug that old channel members were remembered in the
database even after they left the channel. Concretely, they remained in
the `past_members` table that's only meant for groups.
Though it was not a bad bug; we're anyways not cleaning up old contacts.
We currently synchronize "seen" status of messages by setting `\Seen` flag on IMAP and then looking
for new `\Seen` flags using `CONDSTORE` IMAP extension. This approach has multiple disadvantages:
- It requires that the server supports `CONDSTORE` extension. For example Maddy does not support
CONDSTORE yet: https://github.com/foxcpp/maddy/issues/727
- It leaks the seen status to the server without any encryption.
- It requires more than just store-and-forward queues and prevents replacing IMAP with simpler
protocols like POP3 or UUCP or some HTTP-based API for queue polling.
A simpler approach is to send MDNs to self when `Config::BccSelf` (aka multidevice) is enabled,
regardless of whether the message requested and MDN. If MDN was requested and we have MDNs enabled,
then also send to the message sender, but MDN to self is sent regardless of whether read receipts
are actually enabled.
`sync_seen_flags()` and `CONDSTORE` check is better completely removed, maybe after one
release. `store_seen_flags_on_imap()` can be kept for unencrypted non-chat messages.
One potential problem with sending MDNs is that it may trigger ratelimits on some providers and
count as another recipient.
84161f4202 promotes group members to `Origin::IncomingTo` when
accepting it, instead of `CreateChat` as before, but this changes almost nothing because it happens
rarely that the user only accepts a group and writes nothing there soon. Now if a message has
multiple recipients, i.e. it's a 3-or-more-member group, or if it's a broadcast message, we don't
scale up its recipients to `Origin::OutgoingTo`.
Before this PR, when a user with current main sends a large message to a
user with an old Delta Chat (before #7431), the text will be duplicated:
One message will arrive with only the text, and one message with
attachment+text.
This PR changes this - there will be one message with only the text, and
one message with only the attachment.
If we want to guard against lost pre-messages, then we can revert this
PR in a few months, though I'm not sure that's necessary - it's unlikely
that the small pre-message gets lost but the big post-message gets
through.
`chat::set_chat_profile_image()` already checks that the group has grpid, still it makes sense to
check that a message is encrypted when sending, in case if the chat has a profile image in the db
for some reason.
There are quite some unneeded stock strings; this PR removes some of
them. None of these stock strings were actually set by the UI, or even
have translations in Transifex.
- We don't have AEAP anymore.
- The "I added/removed member" and "I left the group" strings are
anyways not meant to be shown to the user. Also, starting to translate
them now would leak the device language.
BREAKING CHANGE: This can theoretically be a breaking change because a
UI could reference one of the removed stock strings, so I marked it as
breaking just in case.
Fix#7435
For most messages, `calc_sort_timestamp()` makes sure that they are at the correct place; esp. that they are not above system messages or other noticed/seen messages.
Most callers of `add_info_msg()`, however, didn't call `calc_sort_timestamp()`, and just used `time()` or `smeared_time()` to get the sort timestamp. Because of this, system messages could sometimes wrongly be sorted above other messages.
This PR fixes this by making the sort timestamp optional in `add_info_msg*()`. If the sort timestamp isn't passed, then the message is sorted to the bottom of the chat. `sent_rcvd_timestamp` is not optional anymore, because we need _some_ timestamp that can be shown to the user (most callers just pass `time()` there).
And enable it by default as the standard Header Protection is backward-compatible.
Also this tests extra IMF header removal when a message has standard Header Protection since now we
can send such messages.
Omit Legacy Display Elements from "text/plain" and "text/html" (implement 4.5.3.{2,3} of
https://www.rfc-editor.org/rfc/rfc9788 "Header Protection for Cryptographically Protected Email").
Follow-up for https://github.com/chatmail/core/pull/7042, part of
https://github.com/chatmail/core/issues/6884.
This will make it possible to create invite-QR codes for broadcast
channels, and make them symmetrically end-to-end encrypted.
- [x] Go through all the changes in #7042, and check which ones I still
need, and revert all other changes
- [x] Use the classical Securejoin protocol, rather than the new 2-step
protocol
- [x] Make the Rust tests pass
- [x] Make the Python tests pass
- [x] Fix TODOs in the code
- [x] Test it, and fix any bugs I find
- [x] I found a bug when exporting all profiles at once fails sometimes,
though this bug is unrelated to channels:
https://github.com/chatmail/core/issues/7281
- [x] Do a self-review (i.e. read all changes, and check if I see some
things that should be changed)
- [x] Have this PR reviewed and merged
- [ ] Open an issue for "TODO: There is a known bug in the securejoin
protocol"
- [ ] Create an issue that outlines how we can improve the Securejoin
protocol in the future (I don't have the time to do this right now, but
want to do it sometime in winter)
- [ ] Write a guide for UIs how to adapt to the changes (see
https://github.com/deltachat/deltachat-android/pull/3886)
## Backwards compatibility
This is not very backwards compatible:
- Trying to join a symmetrically-encrypted broadcast channel with an old
device will fail
- If you joined a symmetrically-encrypted broadcast channel with one
device, and use an old core on the other device, then the other device
will show a mostly empty chat (except for two device messages)
- If you created a broadcast channel in the past, then you will get an
error message when trying to send into the channel:
> The up to now "experimental channels feature" is about to become an officially supported one. By that, privacy will be improved, it will become faster, and less traffic will be consumed.
>
> As we do not guarantee feature-stability for such experiments, this means, that you will need to create the channel again.
>
> Here is what to do:
> • Create a new channel
> • Tap on the channel name
> • Tap on "QR Invite Code"
> • Have all recipients scan the QR code, or send them the link
>
> If you have any questions, please send an email to delta@merlinux.eu or ask at https://support.delta.chat/.
## The symmetric encryption
Symmetric encryption uses a shared secret. Currently, we use AES128 for
encryption everywhere in Delta Chat, so, this is what I'm using for
broadcast channels (though it wouldn't be hard to switch to AES256).
The secret shared between all members of a broadcast channel has 258
bits of entropy (see `fn create_broadcast_shared_secret` in the code).
Since the shared secrets have more entropy than the AES session keys,
it's not necessary to have a hard-to-compute string2key algorithm, so,
I'm using the string2key algorithm `salted`. This is fast enough that
Delta Chat can just try out all known shared secrets. [^1] In order to
prevent DOS attacks, Delta Chat will not attempt to decrypt with a
string2key algorithm other than `salted` [^2].
## The "Securejoin" protocol that adds members to the channel after they
scanned a QR code
This PR uses the classical securejoin protocol, the same that is also
used for group and 1:1 invitations.
The messages sent back and forth are called `vg-request`,
`vg-auth-required`, `vg-request-with-auth`, and `vg-member-added`. I
considered using the `vc-` prefix, because from a protocol-POV, the
distinction between `vc-` and `vg-` isn't important (as @link2xt pointed
out in an in-person discussion), but
1. it would be weird if groups used `vg-` while broadcasts and 1:1 chats
used `vc-`,
2. we don't have a `vc-member-added` message yet, so, this would mean
one more different kind of message
3. we anyways want to switch to a new securejoin protocol soon, which
will be a backwards incompatible change with a transition phase. When we
do this change, we can make everything `vc-`.
[^1]: In a symmetrically encrypted message, it's not visible which
secret was used to encrypt without trying out all secrets. If this does
turn out to be too slow in the future, then we can remember which secret
was used more recently, and and try the most recent secret first. If
this is still too slow, then we can assign a short, non-unique (~2
characters) id to every shared secret, and send it in cleartext. The
receiving Delta Chat will then only try out shared secrets with this id.
Of course, this would leak a little bit of metadata in cleartext, so, I
would like to avoid it.
[^2]: A DOS attacker could send a message with a lot of encrypted
session keys, all of which use a very hard-to-compute string2key
algorithm. Delta Chat would then try to decrypt all of the encrypted
session keys with all of the known shared secrets. In order to prevent
this, as I said, Delta Chat will not attempt to decrypt with a
string2key algorithm other than `salted`
BREAKING CHANGE: A new QR type AskJoinBroadcast; cloning a broadcast
channel is no longer possible; manually adding a member to a broadcast
channel is no longer possible (only by having them scan a QR code)
We already have both rand 0.8 and rand 0.9
in our dependency tree.
We still need rand 0.8 because
public APIs of rPGP 0.17.0 and Iroh 0.35.0
use rand 0.8 types in public APIs,
so it is imported as rand_old.
This mechanism replaces `Chat-Verified` header.
New parameter `_verified=1` in `Autocrypt-Gossip`
header marks that the sender has the gossiped key
verified.
Using `_verified=1` instead of `_verified`
because it is less likely to cause troubles
with existing Autocrypt header parsers.
This is also how https://www.rfc-editor.org/rfc/rfc2045
defines parameter syntax.
With newer Iroh it is possible to obtain
own node address before home relay is selected
and accidentally send own address without relay URL.
It took me some time to debug why Iroh 0.92.0
did not work with iroh-relay 0.92.0
so I'm adding these assertions even
while we still use Iroh 0.35.0.
SDP offer and answer contain newlines.
Without the fix these newlines are not encoded at all
and break the header into multiple headers
or even prevent parsing of the following headers.
- sync declined calls from callee to caller, as usual in all larger
messengers
- introduce the call states "Missed call", "Declined call" and
"Cancelled all" ("Ended call" is gone)
- allow calling end_call()/accept_call() for already ended/accepted
calls, in practise, handling all cornercases is tricky in UI - and the
state needs anyways to be tracked.
- track and show the call duration
the duration calculation depends on local time, but it is displayed only
coarse and is not needed for any state. this can be improved as needed,
timestamps of the corresponding messages are probably better at some
point. or ending device sends its view of the time around. but for the
first throw, it seems good enough
if we finally want that set of states, it can be exposed to a json-info
in a subsequent call, so that the UI can render it more nicely. fallback
strings as follows will stay for now to make adaption in other UI easy,
and for debugging:
<img width="320" alt="IMG_0154"
src="https://github.com/user-attachments/assets/09a89bfb-66f4-4184-b05c-e8040b96cf44"
/>
successor of https://github.com/chatmail/core/pull/6650
