This mysterious ssh application

Roberto Aloi <>
Wed Jan 20 20:23:27 CET 2010

Hi all,

I was trying to play a bit with the ssh application and I found some fancy stuff in it.

First of all, I've noticed that the public_key application (required by ssh) was not in the applications list of the ssh application (in the .app.src, I mean).
Since the public_key application was not loaded in my system, it took me a while to understand this (the error in the stack trace was showing something cryptic like: "{no_io_allowed,read_password}").
I've already created and submitted a simple patch on github. I must admit I've read too late the guidelines for submitting patches to Erlang OTP, so I will try to be a better boy the next time.

Second and most important. Reading from the documentation, it seems I can specify a callback module for my SSH connection:

{key_cb, atom() = KeyCallbackModule}

Provide a special call-back module for key handling. The call-back module should be modeled after the ssh_file module. The functions that must be exported are: private_host_rsa_key/2, private_host_dsa_key/2, lookup_host_key/3 and add_host_key/3. This is considered somewhat experimental and will be better documented later on.
---END CITE---

Well, the ssh_file should be a behaviour and it's not.

The functions that are present in the documentation as the ones to be exported seems not to be enough (at least for my app). At least private_identity_key/2 should be included.

Functions like the ssh_auth:publickey_msg/1 refer to the ssh_file module directly, while they should use functions defined in the callback module, if needed.

I actually needed a parametrized module, so I couldn't specify an atom for my key_cb option. Still, I passed the checks and my parameter has been accepted. That was good, but the documentation should be corrected.

I know all this is meant to be an experimental part of the SSH application, but I would like to know if anyone is working on that.

I'll hopefully try to fix some of these as soon I find some spare hours.

Best regards,

Roberto Aloi
Twitter: @prof3ta



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