Added persistence documentation

docs/source/api/index.rst

@@ -12,4 +12,5 @@ prompt commands or more complicated privilege escalation or persistence methods.
 
     commandparser.rst
     privesc.rst
+    persist.rst
     victim.rst

docs/source/api/persist.rst

@@ -0,0 +1,78 @@
+Persistence Methods
+===================
+
+Persistence methods are implemented through an abstract ``PersistenceMethod`` base class which defines methods
+for installing and removing various persistence methods. The persistence module and associated base classes
+are defined in the ``pwncat/persist/__init__.py`` script.
+
+Persistence methods are loaded using the ``pkgutil`` python module automatically from the ``pwncat/persist``
+subdirectory. Any module implementing a ``Method`` class which inherits from the ``PersistenceMethod``
+base class will be imported as an available persistence method.
+
+Implementing Persistence Methods
+--------------------------------
+
+A persistence method is implemented by creating a new script under the ``pwncat/persist`` directory
+which implements a ``Method`` class. This class must inherit from the ``PersistenceMethod`` base
+class and implement the ``install`` and ``remove`` functions.
+
+A privilege escalation method also defines a few properties as class variables which govern how
+the method is utilized by ``pwncat``. The ``system`` variable is a boolean defining whether this
+persistence method allows access only as ``root`` or is installed on a per-user basis. If this
+item is true, all ``user`` options in further methods are ignored.
+
+The ``name`` variable is used to create user-readable formatted strings representing this persistence
+method. Lastly, the ``local`` variable is a boolean defining whether the persistence method allows
+local escalation to the specified user.
+
+Three methods can be overridden within the ``PersistenceMethod`` base class. The first is the ``install``
+method. This method takes a ``user`` parameter (if not a system method), and should install persistence
+as the specified user. If there is a problem or error during installation, ``PersistenceError`` should
+be raised with a description of the error.
+
+Next, the ``remove`` method must be implemented to undo the actions of the ``install`` method. It takes
+the same ``user`` argument, and upon error should also raise ``PersistenceError``.
+
+Lastly, the ``escalate`` method is only required if ``local`` is true. It should leverage this
+persistence method to gain access shell access as the specified user (again, user should be ignored
+for system methods). This is used as a shortcut in the implementation of the ``privesc`` command
+to utilize local persistence methods to escalate to different users.
+
+Locating and Installing Persistence Methods
+-------------------------------------------
+
+If you would like to programmatically install, remove or locate privilege escalation methods,
+you can use the ``pwncat.victim.persist`` module. This module provides a generic interface
+to enumerate available methods, list installed methods, and locate methods by name.
+
+The ``install`` method takes a method name and an optional user. This will locate the identified
+method and call it's ``install`` routine. If installation is successful, it will register the
+method in the database as installed and also register a corresponding tamper object to track
+the installation. If the method does not exist or failed to install, a ``PersistenceError``
+exception is raised.
+
+The ``register`` method takes the same parameters as the ``install`` method. It will register the
+specified method as being installed but not perform the installation routine. This is useful
+when a module installs a persistence method in a non-standard way and needs to register this
+installation with the framework. For example, the ``privesc`` module may install SSH authorized
+keys via a privesc file writer. If this happens, it will register this persistence with the ``persist``
+module for tracking.
+
+The ``remove`` is the inverse of the ``install`` method, and will completely remove the given
+persistence method.
+
+To find a persistence method by name, you can use the ``find`` method which returns an iterator
+of known persistence methods. The  ``persist`` module is also an iterator which will yield all
+known persistence methods.
+
+The Persistence Module Class
+----------------------------
+
+.. autoclass:: pwncat.persist.Persistence
+    :members:
+
+The Base Persistence Method Class
+---------------------------------
+
+.. autoclass:: pwncat.persist.PersistenceMethod
+    :members:

pwncat/persist/__init__.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 import functools
 import pkgutil
-from typing import Optional, Dict, Iterator
+from typing import Optional, Dict, Iterator, Tuple
 from colorama import Fore
 
 import pwncat
@@ -20,6 +20,13 @@ def persistence_tamper_removal(name: str, user: Optional[str] = None):
 
 
 class Persistence:
+    """
+    This class abstracts the management of persistence methods and is accessible at runtime
+    via ``pwncat.victim.persist``. It provides methods of enumerating available persistence
+    methods, enumerating installed persistence methods, installing methods, and removing
+    methods.
+    """
+
     def __init__(self):
 
         self.methods: Dict[str, "PersistenceMethod"] = {}
@@ -29,8 +36,17 @@ class Persistence:
             self.methods[method.name] = method
 
     def install(self, name: str, user: Optional[str] = None):
-        """ Add persistence as the specified user. If the specified persistence
-        method is system method, the "user" argument is ignored. """
+        """
+        Install the specified method by name. If the specified method is not a system
+        method, ``user`` specifies the user to install this method as. Otherwise, the
+        ``user`` parameter is ignored.
+        
+        This method raises a PersistenceError if installation failed or the given method
+        does not exist.
+        
+        :param name: the name of the persistence method to install
+        :param user: the user to install persistence as
+        """
         try:
             method = next(self.find(name))
         except StopIteration:
@@ -45,9 +61,17 @@ class Persistence:
         self.register(name, user)
 
     def register(self, name: str, user: Optional[str] = None):
-        """ Register a persistence method as pre-installed. This is useful for some privilege escalation
+        """
+        Register a persistence method as pre-installed. This is useful for some privilege escalation
         which automatically adds things equivalent to persistent, but without the
-        persistence module itself (e.g. backdooring /etc/passwd or SSH keys). """
+        persistence module itself (e.g. backdooring /etc/passwd or SSH keys).
+        
+        This method raises a PersistenceError if the given persistence method
+        does not exist.
+        
+        :param name: the method to register as pre-installed
+        :param user: the user the method was installed as
+        """
 
         method = next(self.find(name))
 
@@ -61,47 +85,54 @@ class Persistence:
         )
 
     @property
-    def installed(self) -> Iterator["PersistenceMethod"]:
-        """ Retrieve a list of installed persistence methods """
+    def installed(self) -> Iterator[Tuple[str, "PersistenceMethod"]]:
+        """
+        Enumerate all installed persistence methods.
+        
+        :return: An iterator of tuples of (username,PeristenceMethod)
+        """
         for persist in pwncat.victim.host.persistence:
             yield persist.user, self.methods[persist.method]
 
     @property
-    def available(self) -> Iterator[str]:
-        """ Yield all the known methods """
+    def available(self) -> Iterator["PersistenceMethod"]:
+        """
+        Enumerate all available persistence methods
+        
+        :return: Iterator of available persistence methods
+        """
         yield from self.methods.values()
 
-    def find(
-        self,
-        name: Optional[str] = None,
-        user: Optional[str] = None,
-        installed: bool = False,
-        local: Optional[bool] = None,
-        system: Optional[bool] = None,
-    ) -> Iterator["PersistenceMethod"]:
+    def find(self, name: Optional[str] = None,) -> Iterator["PersistenceMethod"]:
+        """
+        Locate persistence methods matching the given name.
         
+        :param name: the name of the persistence module to locate
+        :return: Iterator of persistence methods matching the name
+        """
         for method in self.methods.values():
             if name is not None and method.name != name:
                 # not the requested method
                 continue
-            if installed:
-                if user is not None or system is None or method.system == system:
-                    if not method.installed(user):
-                        continue
-                else:
-                    # the user was not specified and this module is not a
-                    # system module. We can't check install state, so we
-                    # err on the side of caution here.
-                    continue
-            if local is not None and method.local != local:
-                continue
             # All checks passed. Yield the method.
             yield method
 
     def remove(self, name: str, user: Optional[str] = None, from_tamper: bool = False):
-        """ Remove the specified persistence method from the remote victim
+        """
+        Remove the specified persistence method from the remote victim
         if the given persistence method is a system method, the "user"
-        argument is ignored. """
+        argument is ignored.
+        
+        Raises a ``PersistenceError`` if the given method doesn't exist or removal
+        failed.
+        
+        The ``from_tamper`` parameter should not be used and is only used
+        for internal removal from within the tamper subsystem.
+        
+        :param name: the name of the method to remove
+        :param user: the user which was used to install this method
+        :param from_tamper: whether we are removing from the tamper removal system
+        """
         try:
             method = next(self.find(name))
         except StopIteration:
@@ -138,7 +169,9 @@ class Persistence:
 
 
 class PersistenceMethod:
-    """ Base persistence method class """
+    """ Base persistence method class. The docstring for your method class will
+    become the long-form help for this method (viewable with ``persist -l -m {method-name}``)
+    """
 
     def __init__(self):
         pass
@@ -162,9 +195,21 @@ class PersistenceMethod:
         raise NotImplementedError
 
     def install(self, user: Optional[str] = None):
+        """
+        Install this method of persistence as the given user. Raise a
+        ``PersistenceError`` if installation fails.
+        
+        :param user: the user to install persistence as
+        """
         raise NotImplementedError
 
     def remove(self, user: Optional[str] = None):
+        """
+        Remove this method of persistence as the given user. Raise a
+        ``PersistenceError`` if removal fails.
+        
+        :param user: the user to remove persistence as
+        """
         raise NotImplementedError
 
     def installed(self, user: Optional[str] = None) -> bool: