RT-AX88U - 3004.388.8_2 - SSH connection closed after few minutes from reboot

[ardennguyen]

I'm facing issue where dropbear will close the connection and refuse to accept any connection after that, until a reboot.
After a reboot, SSH works fine for a few minutes then close again with no system log alert.

Anyone has same issue?

 

[ColinTaylor]

Make sure you don't have anything on your network that is set to automatically log in via SSH (e.g. home automation device). Also check that you have not enabled SSH access from the WAN (Administration - System).

 

[ardennguyen]

Make sure you don't have anything on your network that is set to automatically log in via SSH (e.g. home automation device). Also check that you have not enabled SSH access from the WAN (Administration - System).

I don't have any device set to log in router's SSH automatically. Also, SSH access is set to "LAN Only", no WAN access.

I found this changelog from dropbear's author's website saying build 2024.84 used on 3004.388.8_2 has some regressions. Link: https://matt.ucc.asn.au/dropbear/CHANGES

Problem is I only noticed this issue today, not sure if it happened before when I upgraded the router firmware.

 

[DJones]

I don't have any device set to log in router's SSH automatically. Also, SSH access is set to "LAN Only", no WAN access.

I found this changelog from dropbear's author's website saying build 2024.84 used on 3004.388.8_2 has some regressions. Link: https://matt.ucc.asn.au/dropbear/CHANGES

Problem is I only noticed this issue today, not sure if it happened before when I upgraded the router firmware.

Might be some useful info here: https://openwrt.org/docs/guide-user/base-system/dropbear

 

[DJones]

Check your ssh client doesn’t also have any inactivity settings.

 

[Ripshod]

It's not your router, it's not the firmware and it's not dropbear (unless your router is somehow infected). What does the system log say when ssh fails? What ssh client are you using? Does sshd ever appear in top/htop? If dropbear gives you time enter "dropbear -V" (without the quotes) to confirm the version.

 

[eibgrad]

What makes this so difficult is that the primary diagnostic tool is the very thing under investigation. I understand telnet is NOT secure, and so having it disabled/hidden by default is understandable. But removing it entirely leaves you w/ no viable options for a case such as this. AFAICT, no console interface w/ ASUS either. Either ssh works or you're screwed.

 

[ardennguyen]

It's not your router, it's not the firmware and it's not dropbear (unless your router is somehow infected). What does the system log say when ssh fails? What ssh client are you using? Does sshd ever appear in top/htop? If dropbear gives you time enter "dropbear -V" (without the quotes) to confirm the version.

- No log in System log, already set to Debug level
- Putty, windows terminal, command prompt all same result
- No sshd, just dropbear
- Let me check the version

 

[ardennguyen]

Check your ssh client doesn’t also have any inactivity settings.

I tried on windows terminal to make sure I did not mess up putty settings. Same issue.

 

[Ripshod]

I'm going to jump the gun here. What Idle Timeout do you have set? (bottom of this screenshot):

 

[ardennguyen]

I'm going to jump the gun here. What Idle Timeout do you have set? (bottom of this screenshot):
View attachment 62136

Before I leave it at 20. From yesterday, I set it to 0.