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X11 forwarding not working with ssh -X session #11531

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ericpaulsen opened this issue Jan 9, 2024 · 2 comments · Fixed by #11550
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X11 forwarding not working with ssh -X session #11531

ericpaulsen opened this issue Jan 9, 2024 · 2 comments · Fixed by #11550
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@mafredri
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cli Area: CLI use-case A novel and interesting way to use Coder

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@ericpaulsen
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ericpaulsen commented Jan 9, 2024 •
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experienced on 2.6.0 - repro steps:

  1. Download XQuartz (X client for Mac) to local Mac
  2. Start Coder workspace (K8s pod), install xauth via sudo apt-get update && sudo apt-get install -y xauth
  3. Authenticate to Coder via coder login
  4. Run coder config-ssh to config local SSH config file
  5. Run ssh -X coder.<workspace-name>
  6. Run xeyes (install via sudo apt-get install -y x11-apps)
  7. Observe XQuartz application opening, but no window appears
@ericpaulsen ericpaulsen added cli Area: CLI use-case A novel and interesting way to use Coder bug labels Jan 9, 2024
@mafredri
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mafredri commented Jan 10, 2024 •
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This problem is due to us not managing xauth properly.

If you forward once, you're fine:

❯ ssh -X coder.w

coder@w ~
❯ xauth list
w/unix:0  MIT-MAGIC-COOKIE-1  4e41a3c0aa69172ca2438c185e7f5262

But the second time you do it, there will be two entries:

❯ ssh -X coder.w

coder@w ~
❯ xauth list
w/unix:0  MIT-MAGIC-COOKIE-1  4e41a3c0aa69172ca2438c185e7f5262
w/unix:0  MIT-MAGIC-COOKIE-1  635ea6298f18b17453ce613ed04ea438

The first one will be used, and thus, authentication fails.

The issue can be worked around by running xauth remove w/unix:0 inside the workspace, then reconnecting with -X (ssh -X coder.w).

To fix this, we should:

  • Remove the entry from .Xauthority on disconnect (if the magic cookie still matches?)
  • On connect, if entry is present, remove/update the magic cookie

@ericpaulsen
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@mafredri - thank you. I confirmed the problem and validated the forwarding works with a single magic cookie entry.

mafredri added a commit that referenced this issue Jan 10, 2024
@mafredri
fix(agent/agentssh): fix X11 forwarding by improving Xauthority manag…
df96dcf 
…ement

Fixes #11531
@mafredri mafredri mentioned this issue Jan 10, 2024
Merged
mafredri added a commit that referenced this issue Jan 10, 2024
@mafredri
fix(agent/agentssh): fix X11 forwarding by improving Xauthority manag…
aab6bff 
…ement

Fixes #11531
mafredri added a commit that referenced this issue Jan 10, 2024
@mafredri
fix(agent/agentssh): fix X11 forwarding by improving Xauthority manag…
43d09a5 
…ement

Fixes #11531
mafredri added a commit that referenced this issue Jan 10, 2024
@mafredri
fix(agent/agentssh): fix X11 forwarding by improving Xauthority manag…
63603e0 
…ement

Fixes #11531
mafredri added a commit that referenced this issue Jan 10, 2024
@mafredri
fix(agent/agentssh): fix X11 forwarding by improving Xauthority manag…
b1d53a6 
…ement (#11550)

Fixes #11531
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fix(agent/agentssh): fix X11 forwarding by improving Xauthority management coder/coder
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