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There are bugs. But Screen itself is running locally and per-user? I could imagine attacking from one tab (window) interacting with another tab but then the us

There are bugs. But Screen itself is running locally and per-user? I could imagine attacking from one tab (window) interacting with another tab but then the user runs already a harmful application. I worry more about everything containing Electron or similar built “web applications”.

kzrdude 2y ago
Screen has multiuser features, two people can share the same screen session
- sam_lowry_ 2y ago
  screen -x
  - ho_schi 2y ago
    This rocks. It is a superpower and I love it :)
- thanatos519 2y ago
  It's such a great feature and even has ACLs. I used to do training with this. Every student got a private username/password to connect to my laptop where their login shell connected to a specific window (to which only that user had access) in a shared screen session. They each had their own little environment to hack in. Then when we were doing exercises and people got stuck, I would put their screen up on the projector so we could discuss their code together.
neilv 2y ago
For example, you start a `screen` session, and within one of those `screen` windows, you SSH to an untrusted remote system, and that remote system can then send arbitrary bytes to be interpreted by `screen`. If there's a bug, it's potentially remote system having arbitrary code execution capability on your local system that's running `screen`, under your UID, and then escalate from there.
- nextos 2y ago
  This is why Linux should be taking things like the xz exploit more seriously and, at least, adopting a solution like firejail or bwrap everywhere. It's not a perfect solution, but it's a step in the right direction towards patching the Unix model, so that programs don't have privileges they don't need. Mobile Linux (Mer / SailfishOS) works this way to mimic app-based architectures. But, unlike Android, it still feels like regular Linux.
  - neilv 2y ago
    `screen` is trickier to sandbox/compartmentalize than some programs, because it needs permission to create and interact with ttys, most often with shells attached to them, and normally those shells can't be restricted.
    - nextos 2y ago
      I know, this is why I said it's not perfect.

kzrdude 2y ago

Screen has multiuser features, two people can share the same screen session

sam_lowry_ 2y ago
screen -x
- ho_schi 2y ago
  This rocks. It is a superpower and I love it :)
thanatos519 2y ago
It's such a great feature and even has ACLs. I used to do training with this. Every student got a private username/password to connect to my laptop where their login shell connected to a specific window (to which only that user had access) in a shared screen session. They each had their own little environment to hack in. Then when we were doing exercises and people got stuck, I would put their screen up on the projector so we could discuss their code together.

neilv 2y ago

For example, you start a `screen` session, and within one of those `screen` windows, you SSH to an untrusted remote system, and that remote system can then send arbitrary bytes to be interpreted by `screen`. If there's a bug, it's potentially remote system having arbitrary code execution capability on your local system that's running `screen`, under your UID, and then escalate from there.

nextos 2y ago
This is why Linux should be taking things like the xz exploit more seriously and, at least, adopting a solution like firejail or bwrap everywhere. It's not a perfect solution, but it's a step in the right direction towards patching the Unix model, so that programs don't have privileges they don't need. Mobile Linux (Mer / SailfishOS) works this way to mimic app-based architectures. But, unlike Android, it still feels like regular Linux.
- neilv 2y ago
  `screen` is trickier to sandbox/compartmentalize than some programs, because it needs permission to create and interact with ttys, most often with shells attached to them, and normally those shells can't be restricted.
  - nextos 2y ago
    I know, this is why I said it's not perfect.