Cannot connect to e-reader via SSH

[levi]

KOReader version: v2023.10
Device: PocketBook TouchHD (PB631)

I followed the Connect to the e-reader via SSH guide to establish an SSH connection between my laptop and my e-reader. First, I enabled login without password in KOReader, but I was still prompted to enter a password. I tried to input an empty string by pressing enter, but it was rejected.

Then, I followed the steps for key authentication, and put both an RSA and ed25519 key in the

/applications/koreader/settings/SSH/authorized_keys

file of KOReader. I'm sure these are correct.

I attached the verbose output of the command I ran to try to get in with my RSA key:

ssh -v -p 2222 -i ~/.ssh/id_touchhd 192.168.0.236

. You can see see

debug1: send_pubkey_test: no mutual signature algorithm

on the bottom that makes me think that RSA is not supported by the SSH server that KOReader is using? Sounds unlikely. Anyway, I tried with ed25519 too:

ssh -v -p 2222 -i id_ed25519_touchhd 192.168.0.236

I don't get the same error here, though I'm still prompted to enter a password.

I did some research, but it seems like I'm the only one with this problem.

Am I missing something? Could this be a device problem? Thanks for the help.

[Kicweed]

Different device and different KOReader version but I've been having SSH problems lately as well:

https://github.com/koreader/koreader/issues/11537

Nice idea using -v with ssh, I'll try it too and see if something useful pops up.

[bitfreak]

Some facts:

The dropbear that comes with KOReader is quite old: Dropbear server v2018.76 with custom patches applied.

• The default port is 2222 not 22 because not all users have root access to their device so they are unable to open any ports under 1000 IIRC.
• Hack option "-n" to disable password checking, probably a similar reason, users might not have a password.
• Keys are made to work with a relative path, for DSA,RSA,ECDSA, but NOT ed25519 because its not implemented.
  • dss settings/SSH/dropbear_dss_host_key
  • rsa settings/SSH/dropbear_rsa_host_key
  • ecdsa settings/SSH/dropbear_ecdsa_host_key
• SSH should be 700 and authorized_keys should be 600 on regular Linux, I don't know if any patches are applied to tackle these prerequisites.
• KEYS should be 600.

If someone can point me to the applied patches, I might be able to compile the latest version v2022.83 with some additional security patches.

[pazos]

The sources: https://github.com/koreader/koreader...party/dropbear

The SSH plugin is considered dead: no longer supported and not recommended. We encourage users to find a better solution for their platform.

It was provided as a last resort option, always better than plain telnet. It is kept to avoid breaking workflows

[bitfreak]

I compiled the latest version, see https://www.mobileread.com/forums/sh...d.php?t=360131