Simplify command exception debugging and make stdio work correctly (#251)

* Simplify command exception debugging and make stdio work correctly

* Make isort happy

* Reorganize exception handler, add default case

* Fix print statement

* Attempt to use ipdb where available

* Sort requirements and add ipdb

* Only use pwndbg.stdio in the exception handler

* Documentation, hook pdb.set_trace()

* Do not require ipdb

* Remove import loop, fix accidental call, set python print-stack

* Use the correct values for print-stack

* Use pdb.Pdb for better set_trace()

pwndbg/__init__.py

@@ -56,6 +56,7 @@ import pwndbg.disasm.sparc
 import pwndbg.disasm.x86
 import pwndbg.dt
 import pwndbg.elf
+import pwndbg.exception
 import pwndbg.heap
 import pwndbg.inthook
 import pwndbg.memory
@@ -64,7 +65,6 @@ import pwndbg.proc
 import pwndbg.prompt
 import pwndbg.regs
 import pwndbg.stack
-import pwndbg.stdio
 import pwndbg.typeinfo
 import pwndbg.version
 import pwndbg.vmmap

pwndbg/commands/__init__.py

@@ -6,22 +6,19 @@ from __future__ import print_function
 from __future__ import unicode_literals
 
 import functools
-import traceback
 
 import gdb
 
 import pwndbg.chain
 import pwndbg.color
 import pwndbg.enhance
+import pwndbg.exception
 import pwndbg.hexdump
 import pwndbg.memory
 import pwndbg.regs
-import pwndbg.stdio
 import pwndbg.symbol
 import pwndbg.ui
 
-debug = True
-
 
 class _Command(gdb.Command):
     """Generic command wrapper"""
@@ -48,8 +45,7 @@ class _Command(gdb.Command):
             self.repeat = self.check_repeated(argument, from_tty)
             return self(*argv)
         except TypeError:
-            if debug:
-                print(traceback.format_exc())
+            pwndbg.exception.handle()
             raise
         finally:
             self.repeat = False
@@ -88,14 +84,13 @@ class _Command(gdb.Command):
 
     def __call__(self, *args, **kwargs):
         try:
-            with pwndbg.stdio.stdio:
-                return self.function(*args, **kwargs)
+            return self.function(*args, **kwargs)
         except TypeError as te:
-            print(te)
             print('%r: %s' % (self.function.__name__.strip(),
                               self.function.__doc__.strip()))
+            pwndbg.exception.handle()
         except Exception:
-            print(traceback.format_exc())
+            pwndbg.exception.handle()
 
 
 class _ParsedCommand(_Command):

pwndbg/events.py

@@ -18,7 +18,7 @@ import gdb
 
 import pwndbg.color
 import pwndbg.config
-import pwndbg.stdio
+import pwndbg.exception
 
 
 debug = pwndbg.config.Parameter('debug-events', False, 'display internal event debugging info')
@@ -116,16 +116,14 @@ def connect(func, event_handler, name=''):
 
             objfile_cache.add(path)
 
-        if pause: return
-        with pwndbg.stdio.stdio:
-            try:
-                func()
-            except Exception as e:
-                msg = "Exception during func={}.{} {!r}".format(func.__module__, func.__name__, a)
-                msg = pwndbg.color.red(msg)
-                print(msg, file=sys.stderr)
-                traceback.print_exc()
-                raise e
+        if pause:
+            return
+
+        try:
+            func()
+        except Exception as e:
+            pwndbg.exception.handle()
+            raise e
 
     registered[event_handler].append(caller)
     event_handler.connect(caller)

pwndbg/exception.py

@@ -0,0 +1,65 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+from __future__ import unicode_literals
+
+import functools
+import pdb
+import sys
+import traceback
+
+import gdb
+
+import pwndbg.config
+
+try:
+	import ipdb as pdb
+except ImportError:
+	pass
+
+verbose = pwndbg.config.Parameter('exception-verbose', False, 'whether to print a full stacktracefor exceptions raised in Pwndbg commands')
+debug = pwndbg.config.Parameter('exception-debugger', False, 'whether to debug exceptions raised in Pwndbg commands')
+
+def handle():
+    """Displays an exception to the user, optionally displaying a full traceback
+    and spawning an interactive post-moretem debugger.
+
+    Notes:
+        - ``set exception-verbose on`` enables stack traces.
+        - ``set exception-debugger on`` enables the post-mortem debugger.
+    """
+    # Display the error
+    if debug or verbose:
+        print(traceback.format_exc())
+    else:
+        exc_type, exc_value, exc_traceback = sys.exc_info()
+        print(exc_type, exc_value)
+
+    # Break into the interactive debugger
+    if debug:
+        with pwndbg.stdio.stdio:
+            pdb.post_mortem()
+
+
+
+@functools.wraps(pdb.set_trace)
+def set_trace():
+    """Enable sane debugging in Pwndbg by switching to the "real" stdio.
+    """
+    debugger = pdb.Pdb(stdin=sys.__stdin__,
+                       stdout=sys.__stdout__,
+                       skip=['pwndbg.stdio', 'pwndbg.exception'])
+    debugger.set_trace()
+
+pdb.set_trace = set_trace
+
+@pwndbg.config.Trigger([verbose, debug])
+def update():
+    if verbose or debug:
+        command = 'set python print-stack full'
+    else:
+        command = 'set python print-stack message'
+
+    gdb.execute(command, from_tty=True, to_string=True)

pwndbg/prompt.py

@@ -9,7 +9,6 @@ import gdb
 
 import pwndbg.events
 import pwndbg.memoize
-import pwndbg.stdio
 
 
 hint_msg = 'Loaded %i commands. Type pwndbg [filter] for a list.' % len(pwndbg.commands._Command.commands)
@@ -31,7 +30,6 @@ def prompt_hook(*a):
 
 @pwndbg.memoize.reset_on_stop
 def prompt_hook_on_stop(*a):
-    with pwndbg.stdio.stdio:
-        pwndbg.commands.context.context()
+    pwndbg.commands.context.context()
 
 gdb.prompt_hook = prompt_hook

pwndbg/stdio.py

@@ -19,36 +19,17 @@ import gdb
 import pwndbg.compat
 
 
-def get(fd, mode):
-    if pwndbg.compat.python3:
-        file = io.open(fd, mode=mode, buffering=0)
-
-        kw ={}
-        if pwndbg.compat.python3:
-            kw['write_through']=True
-
-        return io.TextIOWrapper(file, **kw)
-    else:
-        return codecs.open(fd, mode, 'utf-8')
-
-
 class Stdio(object):
     queue = []
 
     def __enter__(self, *a, **kw):
         self.queue.append((sys.stdin, sys.stdout, sys.stderr))
 
-        if pwndbg.compat.python3 or True:
-            sys.stdin  = get('/dev/stdin', 'rb')
-            sys.stdout = get('/dev/stdout', 'wb')
-            sys.stderr = get('/dev/stderr', 'wb')
+        sys.stdin  = sys.__stdin__
+        sys.stdout = sys.__stdout__
+        sys.stderr = sys.__stderr__
 
     def __exit__(self, *a, **kw):
         sys.stdin, sys.stdout, sys.stderr = self.queue.pop()
 
 stdio = Stdio()
-
-if False:
-    sys.stdin  = get(0, 'rb')
-    sys.stdout = get(1, 'wb')
-    sys.stderr = get(2, 'wb')

requirements.txt

@@ -1,11 +1,11 @@
+future
+isort
 pip
-pycparser
 psutil>=3.1.0
-python-ptrace>=0.8
+pycparser
 pyelftools
-isort
-six
-future
+python-ptrace>=0.8
 ROPgadget
+six
 unicorn>=1.0.0
 https://github.com/aquynh/capstone/archive/next.zip#subdirectory=bindings/python