ssh tube: replaced nonexistent key with str(e) in error handling method to get proper error message displayed in stacktrace

[findus]

When using gdb.debug with the ssh tube, exception message are not printed correctly, with the change the error message gets printed without triggering a second exception:

Current:

 During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/findus/repos/pwncollege/program_security/shellcode_injection/./level13.py", line 35, in <module>
    p = gdb.debug(["sudo", "-u", "root", "/challenge/babyshell-level-13"], cwd='/', ssh=s)
  File "/usr/lib/python3.13/site-packages/pwnlib/context/__init__.py", line 1582, in setter
    return function(*a, **kw)
  File "/usr/lib/python3.13/site-packages/pwnlib/gdb.py", line 676, in debug
    port = _gdbserver_port(gdbserver, ssh)
  File "/usr/lib/python3.13/site-packages/pwnlib/gdb.py", line 391, in _gdbserver_port
    remote   = ssh.connect_remote('127.0.0.1', port)
  File "/usr/lib/python3.13/site-packages/pwnlib/tubes/ssh.py", line 1147, in connect_remote
    return ssh_connecter(self, host, port, timeout, level=self.level)
  File "/usr/lib/python3.13/site-packages/pwnlib/tubes/ssh.py", line 453, in __init__
    self.exception(e.message)
                   ^^^^^^^^^
AttributeError: 'ChannelException' object has no attribute 'message'

With Fix:

[ERROR] ChannelException(1, 'Administratively prohibited')
    Traceback (most recent call last):
      File "/usr/lib/python3.13/site-packages/pwnlib/tubes/ssh.py", line 453, in __init__
        self.sock = parent.transport.open_channel('direct-tcpip', (host, port), ('127.0.0.1', 0))
                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/usr/lib/python3.13/site-packages/paramiko/transport.py", line 1136, in open_channel
        raise e
    paramiko.ssh_exception.ChannelException: ChannelException(1, 'Administratively prohibited')
Traceback (most recent call last):
  File "/home/findus/repos/pwncollege/program_security/shellcode_injection/./level13.py", line 35, in <module>
    p = gdb.debug(args=["sudo", "-u", "root", "/challenge/babyshell-level-13"], cwd='/', ssh=s)
  File "/usr/lib/python3.13/site-packages/pwnlib/context/__init__.py", line 1582, in setter
    return function(*a, **kw)
  File "/usr/lib/python3.13/site-packages/pwnlib/gdb.py", line 676, in debug
    port = _gdbserver_port(gdbserver, ssh)
  File "/usr/lib/python3.13/site-packages/pwnlib/gdb.py", line 391, in _gdbserver_port
    remote   = ssh.connect_remote('127.0.0.1', port)
  File "/usr/lib/python3.13/site-packages/pwnlib/tubes/ssh.py", line 1150, in connect_remote
    return ssh_connecter(self, host, port, timeout, level=self.level)
  File "/usr/lib/python3.13/site-packages/pwnlib/tubes/ssh.py", line 456, in __init__
    self.exception(str(e))
    ~~~~~~~~~~~~~~^^^^^^^^
  File "/usr/lib/python3.13/site-packages/pwnlib/tubes/ssh.py", line 453, in __init__
    self.sock = parent.transport.open_channel('direct-tcpip', (host, port), ('127.0.0.1', 0))
                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.13/site-packages/paramiko/transport.py", line 1136, in open_channel
    raise e
paramiko.ssh_exception.ChannelException: ChannelException(1, 'Administratively prohibited')

[Arusekk]

It looks like self.exception does not log anything but falls back to __getattr__. This is unfortunate, as calling self.exception opens another channel then I suppose.

[findus]

The lower stacktrace is kinda weird, the "self.sock = parent.transport.open_channel" call isn't a new channel invocation, its just the old (first) one.

the self.exception call in the ssh_connector class and not in the ssh class, so __getattr__ should not get invoked at all.

[peace-maker]

Thank you!