[erlang-bugs] SSH misleading error messages and potential bugs

[Roberto Aloi]

Hi all,

I've been playing around with the SSH application a bit and found the
following three weird behaviours. You can read also read this in Markdown
at:

https://gist.github.com/robertoaloi/8861758

### Misleading error message on ssh_sftp:start_channel/1 in case user does
not have a shell

When starting a SFTP channel towards a system where user does not have a
shell (i.e. it has `/bin/false` or equilvalent assigned in the
`/etc/passwd` a misleading error message is returned to the user:

````
1> test:go().
** exception exit: {normal,{gen_server,call,
                                       [<0.53.0>,
                                        {{timeout,infinity},
                                         wait_for_version_negotiation},
                                        infinity]}}
     in function  gen_server:call/3 (gen_server.erl, line 188)
     in call from ssh_channel:call/3 (ssh_channel.erl, line 88)
     in call from ssh_sftp:start_channel/2 (ssh_sftp.erl, line 93)
     in call from test:connect/1 (test.erl, line 14)
````

Where:

````
-module(test).
-compile(export_all).

go() ->
    ok = application:start(crypto),
    ok = application:start(asn1),
    ok = application:start(public_key),
    ok = application:start(ssh),
    connect("rabbitmq").

connect(Username) ->
    {ok, SSHRef} = ssh:connect("localhost", 22, [{user, Username}]),
    {ok, _SFTPChannelRef} = ssh_sftp:start_channel(SSHRef),
    ok.

````

This has been experienced in both R16B03 and R15B03.

### Crash on SSH connect

On R16B03, when connecting via SSH on OS X Mavericks I get:

````
1> test:go().
** exception error: no match of right hand side value {error,"Internal
error"}
     in function  test:connect/1 (test.erl, line 13)
3>
=ERROR REPORT==== 7-Feb-2014::13:38:06 ===
Erlang ssh connection handler failed with reason: function_clause
, Stacktace: [{ssh_connection_handler,userauth,
                  [{ssh_msg_userauth_pk_ok,<<>>, ...
````

### Internal Crash is not real when using the `key_cb` option

When using the 'key_cb' option on `ssh:connect/3` the user should implement
a series of callback functions. Not implementing them and trying to connect
results in an "internal error" which invites the user to send a bug report.
The undef callback function should be catched and reported as a normal
error, not an internal one.

````
please report this to erlang-bugs@REDACTED
````

Hope this help,
-- 
Roberto Aloi
---
Website: http://roberto-aloi.com
Twitter: @robertoaloi
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