Add pwnlib.config module and documentation (Gallopsled#893)

This adds functionality for user configuration files at ~/.pwn.conf
and /etc/pwn.conf.  Previously this was only used by the pwnlib.log
module, and was entirely undocumented.

This is now documented, and offers an easy mechanism for other parts
of the code to have extension points.

docs/source/config.rst

@@ -0,0 +1,4 @@
+:mod:`pwnlib.config` --- Pwntools Configuration File
+====================================================
+
+.. automodule:: pwnlib.config

docs/source/index.rst

@@ -48,6 +48,7 @@ Each of the ``pwntools`` modules is documented here.
    atexception
    atexit
    constants
+   config
    context
    dynelf
    encoders

pwn/__init__.py

@@ -5,6 +5,7 @@
 
 pwnlib.args.initialize()
 pwnlib.log.install_default_handler()
+pwnlib.config.initialize()
 
 log = pwnlib.log.getLogger('pwnlib.exploit')
 args = pwnlib.args.args

pwnlib/config.py

@@ -0,0 +1,60 @@
+# -*- coding: utf-8 -*-
+"""Allows per-user and per-host configuration of Pwntools settings.
+
+The list of configurable options includes all of the logging symbols
+and colors, as well as all of the default values on the global context
+object.
+
+The configuration file is read from ``~/.pwn.conf`` and ``/etc/pwn.conf``.
+
+The configuration file is only read in ``from pwn import *`` mode, and not
+when used in library mode (``import pwnlib``).  To read the configuration
+file in library mode, invoke :func:`.config.initialize`.
+
+The ``context`` section supports complex types, at least as far as is
+supported by ``pwnlib.util.safeeval.expr``.
+
+::
+
+    [log]
+    success.symbol=😎
+    error.symbol=☠
+    info.color=blue
+
+    [context]
+    adb_port=4141
+    randomize=1
+    timeout=60
+    terminal=['x-terminal-emulator', '-e']
+"""
+from __future__ import absolute_import
+
+import ConfigParser
+import os
+
+registered_configs = {}
+
+def register_config(section, function):
+    """Registers a configuration section.
+
+    Arguments:
+        section(str): Named configuration section
+        function(callable): Function invoked with a dictionary of
+            ``{option: value}`` for the entries in the section.
+    """
+    registered_configs[section] = function
+
+def initialize():
+    """Read the configuration files."""
+    from pwnlib.log import getLogger
+    log = getLogger(__name__)
+
+    c = ConfigParser.ConfigParser()
+    c.read(['/etc/pwn.conf', os.path.expanduser('~/.pwn.conf')])
+
+    for section in c.sections():
+        if section not in registered_configs:
+            log.warn("Unknown configuration section %r" % section)
+            continue
+        settings = dict(c.items(section))
+        registered_configs[section](settings)

pwnlib/context/__init__.py

@@ -21,9 +21,11 @@
 
 import socks
 
+from pwnlib.config import register_config
 from pwnlib.device import Device
 from pwnlib.timeout import Timeout
 
+
 _original_socket = socket.socket
 
 class _devnull(object):
@@ -1343,3 +1345,20 @@ def setter(*a, **kw):
         with context.local(**{k:kw.pop(k) for k,v in kw.items() if isinstance(getattr(ContextType, k, None), property)}):
             return function(*a, **kw)
     return setter
+
+# Read configuration options from the context section
+def update_context_defaults(section):
+    # Circular imports FTW!
+    from pwnlib.util import safeeval
+    from pwnlib.log import getLogger
+    log = getLogger(__name__)
+    for key, value in section.items():
+        if key not in ContextType.defaults:
+            log.warn("Unknown configuration option %r in section %r" % (key, 'context'))
+            continue
+        if isinstance(ContextType.defaults[key], (str, unicode)):
+            value = safeeval.expr(value)
+
+        ContextType.defaults[key] = value
+
+register_config('context', update_context_defaults)

pwnlib/log.py

@@ -103,6 +103,7 @@
 import time
 
 from pwnlib import term
+from pwnlib.config import register_config
 from pwnlib.context import Thread
 from pwnlib.context import context
 from pwnlib.exception import PwnlibException
@@ -132,26 +133,26 @@
     }
 
 
-# permit setting logging colors from a configuration file
-config = os.path.expanduser('~/.pwn.conf')
-if os.path.exists(config):
-    c = ConfigParser.ConfigParser()
-    c.read([config])
-
-    for section in c.sections():
-        if section not in _msgtype_prefixes:
+def read_log_config(settings):
+    log = getLogger(__name__)
+    for key, value in settings.items():
+        if '.' not in key:
+            log.warn("Invalid configuration option %r in section %r" % (key, 'log'))
             continue
 
-        for key, value in c.items(section):
-            if key == 'color':
-                try:
-                    _msgtype_prefixes[section][0] = getattr(text, value)
-                except AttributeError:
-                    pass
+        msgtype, key = key.split('.', 1)
+
+        if key == 'color':
+            current = _msgtype_prefixes[msgtype][0]
+            _msgtype_prefixes[msgtype][0] = getattr(text, value, current)
 
-            elif key == 'symbol':
-                _msgtype_prefixes[section][1] = value
+        elif key == 'symbol':
+            _msgtype_prefixes[msgtype][1] = value
+
+        else:
+            log.warn("Unknown configuration option %r in section %r" % (key, 'log'))
 
+register_config('log', read_log_config)
 
 # the text decoration to use for spinners.  the spinners themselves can be found
 # in the `pwnlib.term.spinners` module