Add "none" ssh authentication method (#2405)

* Add "none" ssh authentication method

Allow to "disable" ssh authentication if the remote server has it enabled.

Fixes #2380

* Add CHANGELOG

CHANGELOG.md

@@ -84,6 +84,7 @@ The table below shows which release corresponds to each branch, and what date th
 - [#2387][2387] Convert apport_corefile() output from bytes-like object to string
 - [#2388][2388] libcdb: add `offline_only` to `search_by_symbol_offsets`
 - [#2415][2415] Add shellcraft template for IPv6 socket
+- [#2405][2405] Add "none" ssh authentication method
 
 [2360]: https://github.com/Gallopsled/pwntools/pull/2360
 [2356]: https://github.com/Gallopsled/pwntools/pull/2356
@@ -97,6 +98,7 @@ The table below shows which release corresponds to each branch, and what date th
 [2387]: https://github.com/Gallopsled/pwntools/pull/2387
 [2388]: https://github.com/Gallopsled/pwntools/pull/2388
 [2415]: https://github.com/Gallopsled/pwntools/pull/2415
+[2405]: https://github.com/Gallopsled/pwntools/pull/2405
 
 ## 4.13.0 (`beta`)
 

pwnlib/tubes/ssh.py

@@ -573,7 +573,8 @@ class ssh(Timeout, Logger):
 
     def __init__(self, user=None, host=None, port=22, password=None, key=None,
                  keyfile=None, proxy_command=None, proxy_sock=None, level=None,
-                 cache=True, ssh_agent=False, ignore_config=False, raw=False, *a, **kw):
+                 cache=True, ssh_agent=False, ignore_config=False, raw=False, 
+                 auth_none=False, *a, **kw):
         """Creates a new ssh connection.
 
         Arguments:
@@ -587,10 +588,11 @@ def __init__(self, user=None, host=None, port=22, password=None, key=None,
             proxy_sock(str): Use this socket instead of connecting to the host.
             timeout: Timeout, in seconds
             level: Log level
-            cache: Cache downloaded files (by hash/size/timestamp)
-            ssh_agent: If :const:`True`, enable usage of keys via ssh-agent
-            ignore_config: If :const:`True`, disable usage of ~/.ssh/config and ~/.ssh/authorized_keys
-            raw: If :const:`True`, assume a non-standard shell and don't probe the environment
+            cache(bool): Cache downloaded files (by hash/size/timestamp)
+            ssh_agent(bool): If :const:`True`, enable usage of keys via ssh-agent
+            ignore_config(bool): If :const:`True`, disable usage of ~/.ssh/config and ~/.ssh/authorized_keys
+            raw(bool): If :const:`True`, assume a non-standard shell and don't probe the environment
+            auth_none(bool): If :const:`True`, try to authenticate with no authentication methods
 
         NOTE: The proxy_command and proxy_sock arguments is only available if a
         fairly new version of paramiko is used.
@@ -686,6 +688,11 @@ def __init__(self, user=None, host=None, port=22, password=None, key=None,
                            "    To remove the existing entry from your known_hosts and trust the new key, run the following commands:\n"
                            "        $ ssh-keygen -R %(host)s\n"
                            "        $ ssh-keygen -R [%(host)s]:%(port)s" % locals())
+            except paramiko.SSHException as e:
+                if user and auth_none and str(e) == "No authentication methods available":
+                    self.client.get_transport().auth_none(user)
+                else:
+                    raise
 
             self.transport = self.client.get_transport()
             self.transport.use_compression(True)