Settings > Notifications > Notification Content > Show: "Name Only" or "No Name or Content"
I've had this enabled to prevent sensitive messages from appearing in full whilst showing someone something on my phone, but I guess this is an added benefit as well.
It's a mode of the phone that is supposed to prevent cyber attacks, more so than "normal mode" I suppose, since it's supposed to limit features in the name of security. This seems like a variant of such attack, so seems like it should protect against it
However, if this is important to you then you want Signal to stop telling Android to make the notifications. If it doesn't exist nobody will accidentally make it available.
Deleting that history is good to know about after the fact, but preferably lets just not create the problem.
"Signal’s settings include an option that prevents the actual message content from being previewed in notifications. However, it appears the defendant did not have that setting enabled, which, in turn, seemingly allowed the system to store the content in the database."
Not sure if it's exactly the same, but I had to add a When notification arrives with <message>, do <action> event trigger in my Crank macOS app (https://lowtechguys.com/crank) so I can show you how to do it on macOS:
HOURS=6
EPOCH_DIFF=978307200
SINCE=$(echo "$(date +%s) - $EPOCH_DIFF - $HOURS * 3600" | bc)
sqlite3 ~/Library/Group\ Containers/group.com.apple.usernoted/db2/db \
"SELECT r.delivered_date, COALESCE(a.identifier, 'unknown'), hex(r.data)
FROM record r
LEFT JOIN app a ON r.app_id = a.app_id
WHERE r.delivered_date > $SINCE
ORDER BY r.delivered_date ASC;" \
| while IFS='|' read -r cfdate bundle hexdata; do
date -r $(echo "$cfdate + $EPOCH_DIFF" | bc | cut -d. -f1) '+%Y-%m-%d %H:%M:%S'
echo " app: $bundle"
echo "$hexdata" | xxd -r -p > /tmp/notif.plist
plutil -p /tmp/notif.plist 2>/dev/null \
| grep -E '"(titl|title|subt|subtitle|body|message)"' \
| sed 's/^ */ /'
echo "---"
done
Basically, notifications are in an sqlite db at ~/Library/Group Containers/group.com.apple.usernoted/db2/db and are stored as plist blobs.
In recent years, filesystem paths for system services have started to converge for both macOS and iOS so I'm thinking with jailbreak you could get read access to that database and get the same data out of it.
On android there are apps that let you see the history - i use NotiStar occasionally to see if i unwittingly dismissed important notifications. And i believe there are apps/settings that help you clear the history from the device.
But this is a reminder that these centralized notification infrastructure (FCM and APNs) store notification content (if the app is told to send content in it - signal with option enabled wouldn't send content) even if we clear local history these middleman still hold it
Larping about security and complaining about companies responding to court orders only gets you so far. Its way more useful to look at what actually happens in reality.
I wonder why Apple doesn't 'just' delete the notification data associated with the app from the internal database when the user deletes the app? It seems like asking for problems to just keep old notification content around forever.
It's one of those problems where as soon as someone notices, it's crazy that no one noticed. I can't imagine this not being overhauled going forward. It's just a bad way to operate and now it's news.
On Android, when I use WhatsApp and have notifications for groups turned off, I can still see that they arrive briefly and then get removed (the icon top left vanishes). I wonder often, if this is a way to push all group message content into an unencrypted data trace as well - for the same use case.
If the notification has the data, then yes. It's trivial to create an app that listens to notifications; Samsung even has one themselves called NotiStar that replicates the notification history feature that Android normally has.
I thought Signal didn’t show message previews by default and you had to go in and enable it? I’ve never had message previews in my Signal and I don’t remember changing anything. Maybe when they introduced the feature, you could pick but they strongly suggested it not showing?
iOS stores the previously displayed notifications in an internal database, which was used to access the data. It’s outside of Signal’s control, they recommend disabling showing notification content in their settings to prevent this attack vector
You can choose what to show in the notification and there is an option to include the message, so I'm guessing that allowed some unencrypted incoming messages to be read.
Sibling comment explains. The notification does arrive encrypted and is decrypted by an app extension (by Signal), however, if the message preview is shown, it is stored unencrypted by iOS. It is that storage that is accessed.
There needs to be a bit more "group chat" control in Signal messages, wherein you could enforce certain settings for certain chats regardless of the phone settings. You could have group chats that would enforce not showing more information in the notifications, while others would still allow it.
I think it fits in pretty well with Signal. As it stands, a group chat can control when a message is automatically deleted for everyone, so everyone can rely on that being a shared setting. That's an intentional design decision. There's no individual opt-out.
An individual can disable name or content in notifications in iOS, or set "mute messages" for a chat to prevent notifications from appearing for that specific chat, but there's nothing that gives group members any assurance that other group members are doing that.
But it would be pretty well in line with the "I trust my contact with this communication, but only if they're not systematically misled to copy it to readily exploitable insecure storage" line of thinking.
Since the purposes of the program are pretty heavy on private communication, I'm inclined to think that takes precedence here, especially considering the consequences for dropping default message previews versus adding default reveal of supposedly private information.
Right. It's purely a protection against MitM snooping. The app has to have the messages in plaintext to display to you via whatever mechanism the OS uses. Seems obvious, but also not, at the same time.
I've found other ways Signal can leak information, even with disappearing messages. It's not the total install-and-be-done privacy screen that some people think it is, and requires a little effort at the user end to fill in a few gaps.
I've had this enabled to prevent sensitive messages from appearing in full whilst showing someone something on my phone, but I guess this is an added benefit as well.
Critical distinction, as merely changing OS notification settings will simply prevent notification content from being displayed on-screen.
Settings > Notifications > Messages > Show
Deleting that history is good to know about after the fact, but preferably lets just not create the problem.
"Signal’s settings include an option that prevents the actual message content from being previewed in notifications. However, it appears the defendant did not have that setting enabled, which, in turn, seemingly allowed the system to store the content in the database."
Second, how can I see this notification history?
In recent years, filesystem paths for system services have started to converge for both macOS and iOS so I'm thinking with jailbreak you could get read access to that database and get the same data out of it.
But this is a reminder that these centralized notification infrastructure (FCM and APNs) store notification content (if the app is told to send content in it - signal with option enabled wouldn't send content) even if we clear local history these middleman still hold it
If you drop a settings widget on your home screen, it will let you choose a specific area, including notifications.
I don't know if the output is the complete database.
Android > Settings > Notifications > Manage > Notification History
Court cases are the real way to audit security.
Larping about security and complaining about companies responding to court orders only gets you so far. Its way more useful to look at what actually happens in reality.
0. https://www.404media.co/fbi-extracts-suspects-deleted-signal...
They rest who "evaluate their threat models" can practice Spy-life-gymnastics by disabling it from Signal.
An individual can disable name or content in notifications in iOS, or set "mute messages" for a chat to prevent notifications from appearing for that specific chat, but there's nothing that gives group members any assurance that other group members are doing that.
Since the purposes of the program are pretty heavy on private communication, I'm inclined to think that takes precedence here, especially considering the consequences for dropping default message previews versus adding default reveal of supposedly private information.
I've found other ways Signal can leak information, even with disappearing messages. It's not the total install-and-be-done privacy screen that some people think it is, and requires a little effort at the user end to fill in a few gaps.
"To use the Signal desktop app, Signal must first be installed on your phone."