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peda.py
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# PEDA - Python Exploit Development Assistance for GDB
#
# Copyright (C) 2012 Long Le Dinh <longld at vnsecurity.net>
#
# License: see LICENSE file for details
#
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import re
import os
import sys
import shlex
import string
import time
import signal
import traceback
import codecs
# point to absolute path of peda.py
PEDAFILE = os.path.abspath(os.path.expanduser(__file__))
if os.path.islink(PEDAFILE):
PEDAFILE = os.readlink(PEDAFILE)
sys.path.insert(0, os.path.dirname(PEDAFILE) + "/lib/")
# Use six library to provide Python 2/3 compatibility
import six
from six.moves import range
from six.moves import input
try:
import six.moves.cPickle as pickle
except ImportError:
import pickle
from skeleton import *
from shellcode import *
from utils import *
import config
from nasm import *
if sys.version_info.major is 3:
from urllib.request import urlopen
from urllib.parse import urlencode
pyversion = 3
else:
from urllib import urlopen
from urllib import urlencode
pyversion = 2
REGISTERS = {
8 : ["al", "ah", "bl", "bh", "cl", "ch", "dl", "dh"],
16: ["ax", "bx", "cx", "dx"],
32: ["eax", "ebx", "ecx", "edx", "esi", "edi", "ebp", "esp", "eip"],
64: ["rax", "rbx", "rcx", "rdx", "rsi", "rdi", "rbp", "rsp", "rip",
"r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15"]
}
###########################################################################
class PEDA(object):
"""
Class for actual functions of PEDA commands
"""
def __init__(self):
self.SAVED_COMMANDS = {} # saved GDB user's commands
####################################
# GDB Interaction / Misc Utils #
####################################
def execute(self, gdb_command):
"""
Wrapper for gdb.execute, catch the exception so it will not stop python script
Args:
- gdb_command (String)
Returns:
- True if execution succeed (Bool)
"""
try:
gdb.execute(gdb_command)
return True
except Exception as e:
if config.Option.get("debug") == "on":
msg('Exception (%s): %s' % (gdb_command, e), "red")
traceback.print_exc()
return False
def execute_redirect(self, gdb_command, silent=False):
"""
Execute a gdb command and capture its output
Args:
- gdb_command (String)
- silent: discard command's output, redirect to /dev/null (Bool)
Returns:
- output of command (String)
"""
result = None
#init redirection
if silent:
logfd = open(os.path.devnull, "r+")
else:
logfd = tmpfile()
logname = logfd.name
gdb.execute('set logging off') # prevent nested call
gdb.execute('set height 0') # disable paging
gdb.execute('set logging file %s' % logname)
gdb.execute('set logging overwrite on')
gdb.execute('set logging redirect on')
gdb.execute('set logging on')
try:
gdb.execute(gdb_command)
gdb.flush()
gdb.execute('set logging off')
if not silent:
logfd.flush()
result = logfd.read()
logfd.close()
except Exception as e:
gdb.execute('set logging off') #to be sure
if config.Option.get("debug") == "on":
msg('Exception (%s): %s' % (gdb_command, e), "red")
traceback.print_exc()
logfd.close()
if config.Option.get("verbose") == "on":
msg(result)
return result
def parse_and_eval(self, exp):
"""
Work around implementation for gdb.parse_and_eval with enhancements
Args:
- exp: expression to evaluate (String)
Returns:
- value of expression
"""
regs = sum(REGISTERS.values(), [])
for r in regs:
if "$"+r not in exp and "e"+r not in exp and "r"+r not in exp:
exp = exp.replace(r, "$%s" % r)
p = re.compile("(.*)\[(.*)\]") # DWORD PTR [esi+eax*1]
matches = p.search(exp)
if not matches:
p = re.compile("(.*).s:(0x.*)") # DWORD PTR ds:0xdeadbeef
matches = p.search(exp)
if matches:
mod = "w"
if "BYTE" in matches.group(1):
mod = "b"
elif "QWORD" in matches.group(1):
mod = "g"
elif "DWORD" in matches.group(1):
mod = "w"
elif "WORD" in matches.group(1):
mod = "h"
out = self.execute_redirect("x/%sx %s" % (mod, matches.group(2)))
if not out:
return None
else:
return out.split(":\t")[-1].strip()
else:
out = self.execute_redirect("print %s" % exp)
if not out:
return None
else:
out = gdb.history(0).__str__()
out = out.encode('ascii', 'ignore')
out = decode_string_escape(out)
return out.strip()
def string_to_argv(self, str):
"""
Convert a string to argv list, pre-processing register and variable values
Args:
- str: input string (String)
Returns:
- argv list (List)
"""
try:
str = str.encode('ascii', 'ignore')
except:
pass
args = list(map(lambda x: decode_string_escape(x), shlex.split(str.decode())))
# need more processing here
for idx, a in enumerate(args):
a = a.strip(",")
if a.startswith("$"): # try to get register/variable value
v = self.parse_and_eval(a)
if v != None and v != "void":
if v.startswith("0x"): # int
args[idx] = v.split()[0] # workaround for 0xdeadbeef <symbol+x>
else: # string, complex data
args[idx] = v
elif a.startswith("+"): # relative value to prev arg
adder = to_int(self.parse_and_eval(a[1:]))
if adder is not None:
args[idx] = "%s" % to_hex(to_int(args[idx-1]) + adder)
elif is_math_exp(a):
try:
v = eval("%s" % a)
# XXX hack to avoid builtin functions/types
if not isinstance(v, six.string_types + six.integer_types):
continue
args[idx] = "%s" % (to_hex(v) if to_int(v) != None else v)
except:
pass
if config.Option.get("verbose") == "on":
msg(args)
return args
################################
# GDB User-Defined Helpers #
################################
def save_user_command(self, cmd):
"""
Save user-defined command and deactivate it
Args:
- cmd: user-defined command (String)
Returns:
- True if success to save (Bool)
"""
commands = self.execute_redirect("show user %s" % cmd)
if not commands:
return False
commands = "\n".join(commands.splitlines()[1:])
commands = "define %s\n" % cmd + commands + "end\n"
self.SAVED_COMMANDS[cmd] = commands
tmp = tmpfile()
tmp.write("define %s\nend\n" % cmd)
tmp.flush()
result = self.execute("source %s" % tmp.name)
tmp.close()
return result
def define_user_command(self, cmd, code):
"""
Define a user-defined command, overwrite the old content
Args:
- cmd: user-defined command (String)
- code: gdb script code to append (String)
Returns:
- True if success to define (Bool)
"""
commands = "define %s\n" % cmd + code + "\nend\n"
tmp = tmpfile(is_binary_file=False)
tmp.write(commands)
tmp.flush()
result = self.execute("source %s" % tmp.name)
tmp.close()
return result
def append_user_command(self, cmd, code):
"""
Append code to a user-defined command, define new command if not exist
Args:
- cmd: user-defined command (String)
- code: gdb script code to append (String)
Returns:
- True if success to append (Bool)
"""
commands = self.execute_redirect("show user %s" % cmd)
if not commands:
return self.define_user_command(cmd, code)
# else
commands = "\n".join(commands.splitlines()[1:])
if code in commands:
return True
commands = "define %s\n" % cmd + commands + code + "\nend\n"
tmp = tmpfile()
tmp.write(commands)
tmp.flush()
result = self.execute("source %s" % tmp.name)
tmp.close()
return result
def restore_user_command(self, cmd):
"""
Restore saved user-defined command
- cmd: user-defined command (String)
Returns:
- True if success to restore (Bool)
"""
if cmd == "all":
commands = "\n".join(self.SAVED_COMMANDS.values())
self.SAVED_COMMANDS = {}
else:
if cmd not in self.SAVED_COMMANDS:
return False
else:
commands = self.SAVED_COMMANDS[cmd]
self.SAVED_COMMANDS.pop(cmd)
tmp = tmpfile()
tmp.write(commands)
tmp.flush()
result = self.execute("source %s" % tmp.name)
tmp.close()
return result
def run_gdbscript_code(self, code):
"""
Run basic gdbscript code as it is typed in interactively
Args:
- code: gdbscript code, lines are splitted by "\n" or ";" (String)
Returns:
- True if success to run (Bool)
"""
tmp = tmpfile()
tmp.write(code.replace(";", "\n"))
tmp.flush()
result = self.execute("source %s" % tmp.name)
tmp.close()
return result
#########################
# Debugging Helpers #
#########################
@memoized
def is_target_remote(self):
"""
Check if current target is remote
Returns:
- True if target is remote (Bool)
"""
out = self.execute_redirect("info program")
if out and "serial line" in out: # remote target
return True
return False
@memoized
def getfile(self):
"""
Get exec file of debugged program
Returns:
- full path to executable file (String)
"""
result = None
out = self.execute_redirect('info files')
if out and '"' in out:
p = re.compile(".*exec file:\s*`(.*)'")
m = p.search(out)
if m:
result = m.group(1)
else: # stripped file, get symbol file
p = re.compile("Symbols from \"([^\"]*)")
m = p.search(out)
if m:
result = m.group(1)
return result
def get_status(self):
"""
Get execution status of debugged program
Returns:
- current status of program (String)
STOPPED - not being run
BREAKPOINT - breakpoint hit
SIGXXX - stopped by signal XXX
UNKNOWN - unknown, not implemented
"""
status = "UNKNOWN"
out = self.execute_redirect("info program")
for line in out.splitlines():
if line.startswith("It stopped"):
if "signal" in line: # stopped by signal
status = line.split("signal")[1].split(",")[0].strip()
break
if "breakpoint" in line: # breakpoint hit
status = "BREAKPOINT"
break
if "not being run" in line:
status = "STOPPED"
break
return status
@memoized
def getpid(self):
"""
Get PID of the debugged process
Returns:
- pid (Int)
"""
out = None
status = self.get_status()
if not status or status == "STOPPED":
return None
if self.is_target_remote(): # remote target
ctx = config.Option.get("context")
config.Option.set("context", None)
try:
out = self.execute_redirect("call getpid()")
except:
pass
config.Option.set("context", ctx)
if out is None:
return None
else:
out = self.execute_redirect("print $")
if out:
return to_int(out.split("=")[1])
else:
return None
pid = gdb.selected_inferior().pid
return int(pid) if pid else None
def getos(self):
"""
Get running OS info
Returns:
- os version (String)
"""
# TODO: get remote os by calling uname()
return os.uname()[0]
@memoized
def getarch(self):
"""
Get architecture of debugged program
Returns:
- tuple of architecture info (arch (String), bits (Int))
"""
arch = "unknown"
bits = 32
out = self.execute_redirect('maintenance info sections ?').splitlines()
for line in out:
if "file type" in line:
arch = line.split()[-1][:-1]
break
if "64" in arch:
bits = 64
return (arch, bits)
def intsize(self):
"""
Get dword size of debugged program
Returns:
- size (Int)
+ intsize = 4/8 for 32/64-bits arch
"""
(arch, bits) = self.getarch()
return bits // 8
def getregs(self, reglist=None):
"""
Get value of some or all registers
Returns:
- dictionary of {regname(String) : value(Int)}
"""
if reglist:
reglist = reglist.replace(",", " ")
else:
reglist = ""
regs = self.execute_redirect("info registers %s" % reglist)
if not regs:
return None
result = {}
if regs:
for r in regs.splitlines():
r = r.split()
if len(r) > 1 and to_int(r[1]) is not None:
result[r[0]] = to_int(r[1])
return result
def getreg(self, register):
"""
Get value of a specific register
Args:
- register: register name (String)
Returns:
- register value (Int)
"""
r = register.lower()
regs = self.execute_redirect("info registers %s" % r)
if regs:
regs = regs.splitlines()
if len(regs) > 1:
return None
else:
result = to_int(regs[0].split()[1])
return result
return None
def set_breakpoint(self, location, temp=0, hard=0):
"""
Wrapper for GDB break command
- location: target function or address (String ot Int)
Returns:
- True if can set breakpoint
"""
cmd = "break"
if hard:
cmd = "h" + cmd
if temp:
cmd = "t" + cmd
if to_int(location) is not None:
return peda.execute("%s *0x%x" % (cmd, to_int(location)))
else:
return peda.execute("%s %s" % (cmd, location))
def get_breakpoint(self, num):
"""
Get info of a specific breakpoint
TODO: support catchpoint, watchpoint
Args:
- num: breakpoint number
Returns:
- tuple (Num(Int), Type(String), Disp(Bool), Enb(Bool), Address(Int), What(String), commands(String))
"""
out = self.execute_redirect("info breakpoints %d" % num)
if not out or "No breakpoint" in out:
return None
lines = out.splitlines()[1:]
# breakpoint regex
p = re.compile("^(\d*)\s*(.*breakpoint)\s*(keep|del)\s*(y|n)\s*(0x[^ ]*)\s*(.*)")
m = p.match(lines[0])
if not m:
# catchpoint/watchpoint regex
p = re.compile("^(\d*)\s*(.*point)\s*(keep|del)\s*(y|n)\s*(.*)")
m = p.match(lines[0])
if not m:
return None
else:
(num, type, disp, enb, what) = m.groups()
addr = ''
else:
(num, type, disp, enb, addr, what) = m.groups()
disp = True if disp == "keep" else False
enb = True if enb == "y" else False
addr = to_int(addr)
m = re.match("in.*at(.*:\d*)", what)
if m:
what = m.group(1)
else:
if addr: # breakpoint
what = ""
commands = ""
if len(lines) > 1:
for line in lines[1:]:
if "already hit" in line: continue
commands += line + "\n"
return (num, type, disp, enb, addr, what, commands.rstrip())
def get_breakpoints(self):
"""
Get list of current breakpoints
Returns:
- list of tuple (Num(Int), Type(String), Disp(Bool), Nnb(Bool), Address(Int), commands(String))
"""
result = []
out = self.execute_redirect("info breakpoints")
if not out:
return []
bplist = []
for line in out.splitlines():
m = re.match("^(\d*).*", line)
if m and to_int(m.group(1)):
bplist += [to_int(m.group(1))]
for num in bplist:
r = self.get_breakpoint(num)
if r:
result += [r]
return result
def save_breakpoints(self, filename):
"""
Save current breakpoints to file as a script
Args:
- filename: target file (String)
Returns:
- True if success to save (Bool)
"""
# use built-in command for gdb 7.2+
result = self.execute_redirect("save breakpoints %s" % filename)
if result == '':
return True
bplist = self.get_breakpoints()
if not bplist:
return False
try:
fd = open(filename, "w")
for (num, type, disp, enb, addr, what, commands) in bplist:
m = re.match("(.*)point", type)
if m:
cmd = m.group(1).split()[-1]
else:
cmd = "break"
if "hw" in type and cmd == "break":
cmd = "h" + cmd
if "read" in type:
cmd = "r" + cmd
if "acc" in type:
cmd = "a" + cmd
if not disp:
cmd = "t" + cmd
if what:
location = what
else:
location = "*0x%x" % addr
text = "%s %s" % (cmd, location)
if commands:
if "stop only" not in commands:
text += "\ncommands\n%s\nend" % commands
else:
text += commands.split("stop only", 1)[1]
fd.write(text + "\n")
fd.close()
return True
except:
return False
def get_config_filename(self, name):
filename = peda.getfile()
if not filename:
filename = peda.getpid()
if not filename:
filename = 'unknown'
filename = os.path.basename("%s" % filename)
tmpl_name = config.Option.get(name)
if tmpl_name:
return tmpl_name.replace("#FILENAME#", filename)
else:
return "peda-%s-%s" % (name, filename)
def save_session(self, filename=None):
"""
Save current working gdb session to file as a script
Args:
- filename: target file (String)
Returns:
- True if success to save (Bool)
"""
session = ""
if not filename:
filename = self.get_config_filename("session")
# exec-wrapper
out = self.execute_redirect("show exec-wrapper")
wrapper = out.split('"')[1]
if wrapper:
session += "set exec-wrapper %s\n" % wrapper
try:
# save breakpoints
self.save_breakpoints(filename)
fd = open(filename, "a+")
fd.write("\n" + session)
fd.close()
return True
except:
return False
def restore_session(self, filename=None):
"""
Restore previous saved working gdb session from file
Args:
- filename: source file (String)
Returns:
- True if success to restore (Bool)
"""
if not filename:
filename = self.get_config_filename("session")
# temporarily save and clear breakpoints
tmp = tmpfile()
self.save_breakpoints(tmp.name)
self.execute("delete")
result = self.execute("source %s" % filename)
if not result:
self.execute("source %s" % tmp.name)
tmp.close()
return result
@memoized
def assemble(self, asmcode, bits=None):
"""
Assemble ASM instructions using NASM
- asmcode: input ASM instructions, multiple instructions are separated by ";" (String)
Returns:
- bin code (raw bytes)
"""
if bits is None:
(arch, bits) = self.getarch()
return Nasm.assemble(asmcode, bits)
def disassemble(self, *arg):
"""
Wrapper for disassemble command
- arg: args for disassemble command
Returns:
- text code (String)
"""
code = ""
modif = ""
arg = list(arg)
if len(arg) > 1:
if "/" in arg[0]:
modif = arg[0]
arg = arg[1:]
if len(arg) == 1 and to_int(arg[0]) != None:
arg += [to_hex(to_int(arg[0]) + 32)]
self.execute("set disassembly-flavor intel")
out = self.execute_redirect("disassemble %s %s" % (modif, ",".join(arg)))
if not out:
return None
else:
code = out
return code
@memoized
def prev_inst(self, address, count=1):
"""
Get previous instructions at an address
Args:
- address: address to get previous instruction (Int)
- count: number of instructions to read (Int)
Returns:
- list of tuple (address(Int), code(String))
"""
result = []
backward = 64+16*count
for i in range(backward):
if self.getpid() and not self.is_address(address-backward+i):
continue
code = self.execute_redirect("disassemble %s, %s" % (to_hex(address-backward+i), to_hex(address+1)))
if code and ("%x" % address) in code:
lines = code.strip().splitlines()[1:-1]
if len(lines) > count and "(bad)" not in " ".join(lines):
for line in lines[-count-1:-1]:
(addr, code) = line.split(":", 1)
addr = re.search("(0x[^ ]*)", addr).group(1)
result += [(to_int(addr), code)]
return result
return None
@memoized
def current_inst(self, address):
"""
Parse instruction at an address
Args:
- address: address to get next instruction (Int)
Returns:
- tuple of (address(Int), code(String))
"""
out = self.execute_redirect("x/i 0x%x" % address)
if not out:
return None
(addr, code) = out.split(":", 1)
addr = re.search("(0x[^ ]*)", addr).group(1)
addr = to_int(addr)
code = code.strip()
return (addr, code)
@memoized
def next_inst(self, address, count=1):
"""
Get next instructions at an address
Args:
- address: address to get next instruction (Int)
- count: number of instructions to read (Int)
Returns:
- - list of tuple (address(Int), code(String))
"""
result = []
code = self.execute_redirect("x/%di 0x%x" % (count+1, address))
if not code:
return None
lines = code.strip().splitlines()
for i in range(1, count+1):
(addr, code) = lines[i].split(":", 1)
addr = re.search("(0x[^ ]*)", addr).group(1)
result += [(to_int(addr), code)]
return result
@memoized
def disassemble_around(self, address, count=8):
"""
Disassemble instructions nearby current PC or an address
Args:
- address: start address to disassemble around (Int)
- count: number of instructions to disassemble
Returns:
- text code (String)
"""
count = min(count, 256)
pc = address
if pc is None:
return None
# check if address is reachable
if not self.execute_redirect("x/x 0x%x" % pc):
return None
prev_code = self.prev_inst(pc, count//2-1)
if prev_code:
start = prev_code[0][0]
else:
start = pc
if start == pc:
count = count//2
code = self.execute_redirect("x/%di 0x%x" % (count, start))
if "0x%x" % pc not in code:
code = self.execute_redirect("x/%di 0x%x" % (count//2, pc))
return code.rstrip()
@memoized
def xrefs(self, search="", filename=None):
"""
Search for all call references or data access to a function/variable
Args:
- search: function or variable to search for (String)
- filename: binary/library to search (String)
Returns:
- list of tuple (address(Int), asm instruction(String))
"""
result = []
if not filename:
filename = self.getfile()
if not filename:
return None
vmap = self.get_vmmap(filename)
elfbase = vmap[0][0] if vmap else 0
if to_int(search) is not None:
search = "%x" % to_int(search)
search_data = 1
if search == "":
search_data = 0
out = execute_external_command("%s -M intel -z --prefix-address -d '%s' | grep '%s'" % (config.OBJDUMP, filename, search))
for line in out.splitlines():
if not line: continue
addr = to_int("0x" + line.split()[0].strip())
if not addr: continue
# update with runtime values
if addr < elfbase:
addr += elfbase
out = self.execute_redirect("x/i 0x%x" % addr)
if out:
line = out
p = re.compile("\s*(0x[^ ]*).*?:\s*([^ ]*)\s*(.*)")
else:
p = re.compile("(.*?)\s*<.*?>\s*([^ ]*)\s*(.*)")
m = p.search(line)
if m:
(address, opcode, opers) = m.groups()
if "call" in opcode and search in opers:
result += [(addr, line.strip())]
if search_data:
if "mov" in opcode and search in opers:
result += [(addr, line.strip())]
return result
def _get_function_args_32(self, code, argc=None):
"""
Guess the number of arguments passed to a function - i386
"""
if not argc:
argc = 0
p = re.compile(".*mov.*\[esp(.*)\],")
matches = p.findall(code)
if matches:
l = len(matches)
for v in matches:
if v.startswith("+"):
offset = to_int(v[1:])
if offset is not None and (offset//4) > l:
continue
argc += 1
else: # try with push style
argc = code.count("push")
argc = min(argc, 6)
if argc == 0:
return []
args = []
sp = self.getreg("sp")
mem = self.dumpmem(sp, sp+4*argc)
for i in range(argc):
args += [struct.unpack("<L", mem[i*4:(i+1)*4])[0]]
return args
def _get_function_args_64(self, code, argc=None):
"""
Guess the number of arguments passed to a function - x86_64
"""
# just retrieve max 6 args
arg_order = ["rdi", "rsi", "rdx", "rcx", "r8", "r9"]
p = re.compile(":\s*([^ ]*)\s*(.*),")
matches = p.findall(code)
regs = [r for (_, r) in matches]
p = re.compile(("di|si|dx|cx|r8|r9"))
m = p.findall(" ".join(regs))
m = list(set(m)) # uniqify
argc = 0
if "si" in m and "di" not in m: # dirty fix
argc += 1
argc += m.count("di")
if argc > 0:
argc += m.count("si")