rev/picker_3

rev/picker_3/flag.txt

@@ -0,0 +1,5 @@
+# 0x70 0x69 0x63 0x6f 0x43 0x54 0x46 0x7b 0x37 0x68 0x31 0x35 0x5f 0x31 0x35 0x5f 0x77 0x68 0x34 0x37 0x5f 0x77 0x33 0x5f 0x67 0x33 0x37 0x5f 0x77 0x31 0x37 0x68 0x5f 0x75 0x35 0x33 0x72 0x35 0x5f 0x31 0x6e 0x5f 0x63 0x68 0x34 0x72 0x67 0x33 0x5f 0x61 0x31 0x38 0x36 0x66 0x39 0x61 0x63 0x7d
+#
+# (hex to ascii)
+
+picoCTF{7h15_15_wh47_w3_g37_w17h_u53r5_1n_ch4rg3_a186f9ac}

rev/picker_3/output.txt

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+$ nc saturn.picoctf.net 58541
+==> help
+
+This program fixes vulnerabilities in its predecessor by limiting what
+functions can be called to a table of predefined functions. This still puts
+the user in charge, but prevents them from calling undesirable subroutines.
+
+* Enter 'quit' to quit the program.
+* Enter 'help' for this text.
+* Enter 'reset' to reset the table.
+* Enter '1' to execute the first function in the table.
+* Enter '2' to execute the second function in the table.
+* Enter '3' to execute the third function in the table.
+* Enter '4' to execute the fourth function in the table.
+
+Here's the current table:
+
+1: print_table
+2: read_variable
+3: write_variable
+4: getRandomNumber
+==> 3
+Please enter variable name to write: getRandomNumber
+Please enter new value of variable: win
+==> 4
+0x70 0x69 0x63 0x6f 0x43 0x54 0x46 0x7b 0x37 0x68 0x31 0x35 0x5f 0x31 0x35 0x5f 0x77 0x68 0x34 0x37 0x5f 0x77 0x33 0x5f 0x67 0x33 0x37 0x5f 0x77 0x31 0x37 0x68 0x5f 0x75 0x35 0x33 0x72 0x35 0x5f 0x31 0x6e 0x5f 0x63 0x68 0x34 0x72 0x67 0x33 0x5f 0x61 0x31 0x38 0x36 0x66 0x39 0x61 0x63 0x7d

rev/picker_3/picker-III.py

@@ -0,0 +1,198 @@
+
+import re
+
+
+
+USER_ALIVE = True
+FUNC_TABLE_SIZE = 4
+FUNC_TABLE_ENTRY_SIZE = 32
+CORRUPT_MESSAGE = 'Table corrupted. Try entering \'reset\' to fix it'
+
+func_table = ''
+
+def reset_table():
+  global func_table
+
+  # This table is formatted for easier viewing, but it is really one line
+  func_table = \
+'''\
+print_table                     \
+read_variable                   \
+write_variable                  \
+getRandomNumber                 \
+'''
+
+def check_table():
+  global func_table
+
+  if( len(func_table) != FUNC_TABLE_ENTRY_SIZE * FUNC_TABLE_SIZE):
+    return False
+
+  return True
+
+
+def get_func(n):
+  global func_table
+
+  # Check table for viability
+  if( not check_table() ):
+    print(CORRUPT_MESSAGE)
+    return
+
+  # Get function name from table
+  func_name = ''
+  func_name_offset = n * FUNC_TABLE_ENTRY_SIZE
+  for i in range(func_name_offset, func_name_offset+FUNC_TABLE_ENTRY_SIZE):
+    if( func_table[i] == ' '):
+      func_name = func_table[func_name_offset:i]
+      break
+
+  if( func_name == '' ):
+    func_name = func_table[func_name_offset:func_name_offset+FUNC_TABLE_ENTRY_SIZE]
+  
+  return func_name
+
+
+def print_table():
+  # Check table for viability
+  if( not check_table() ):
+    print(CORRUPT_MESSAGE)
+    return
+
+  for i in range(0, FUNC_TABLE_SIZE):
+    j = i + 1
+    print(str(j)+': ' + get_func(i))
+
+
+def filter_var_name(var_name):
+  r = re.search('^[a-zA-Z_][a-zA-Z_0-9]*$', var_name)
+  if r:
+    return True
+  else:
+    return False
+
+
+def read_variable():
+  var_name = input('Please enter variable name to read: ')
+  if( filter_var_name(var_name) ):
+    eval('print('+var_name+')')
+  else:
+    print('Illegal variable name')
+
+
+def filter_value(value):
+  if ';' in value or '(' in value or ')' in value:
+    return False
+  else:
+    return True
+
+
+def write_variable():
+  var_name = input('Please enter variable name to write: ')
+  if( filter_var_name(var_name) ):
+    value = input('Please enter new value of variable: ')
+    if( filter_value(value) ):
+      exec('global '+var_name+'; '+var_name+' = '+value)
+    else:
+      print('Illegal value')
+  else:
+    print('Illegal variable name')
+
+
+def call_func(n):
+  """
+  Calls the nth function in the function table.
+  Arguments:
+    n: The function to call. The first function is 0.
+  """
+
+  # Check table for viability
+  if( not check_table() ):
+    print(CORRUPT_MESSAGE)
+    return
+
+  # Check n
+  if( n < 0 ):
+    print('n cannot be less than 0. Aborting...')
+    return
+  elif( n >= FUNC_TABLE_SIZE ):
+    print('n cannot be greater than or equal to the function table size of '+FUNC_TABLE_SIZE)
+    return
+
+  # Get function name from table
+  func_name = get_func(n)
+
+  # Run the function
+  eval(func_name+'()')
+
+
+def dummy_func1():
+  print('in dummy_func1')
+
+def dummy_func2():
+  print('in dummy_func2')
+
+def dummy_func3():
+  print('in dummy_func3')
+
+def dummy_func4():
+  print('in dummy_func4')
+
+def getRandomNumber():
+  print(4)  # Chosen by fair die roll.
+            # Guaranteed to be random.
+            # (See XKCD)
+
+def win():
+  # This line will not work locally unless you create your own 'flag.txt' in
+  #   the same directory as this script
+  flag = open('flag.txt', 'r').read()
+  #flag = flag[:-1]
+  flag = flag.strip()
+  str_flag = ''
+  for c in flag:
+    str_flag += str(hex(ord(c))) + ' '
+  print(str_flag)
+
+def help_text():
+  print(
+  '''
+This program fixes vulnerabilities in its predecessor by limiting what
+functions can be called to a table of predefined functions. This still puts
+the user in charge, but prevents them from calling undesirable subroutines.
+
+* Enter 'quit' to quit the program.
+* Enter 'help' for this text.
+* Enter 'reset' to reset the table.
+* Enter '1' to execute the first function in the table.
+* Enter '2' to execute the second function in the table.
+* Enter '3' to execute the third function in the table.
+* Enter '4' to execute the fourth function in the table.
+
+Here's the current table:
+  '''
+  )
+  print_table()
+
+
+
+reset_table()
+
+while(USER_ALIVE):
+  choice = input('==> ')
+  if( choice == 'quit' or choice == 'exit' or choice == 'q' ):
+    USER_ALIVE = False
+  elif( choice == 'help' or choice == '?' ):
+    help_text()
+  elif( choice == 'reset' ):
+    reset_table()
+  elif( choice == '1' ):
+    call_func(0)
+  elif( choice == '2' ):
+    call_func(1)
+  elif( choice == '3' ):
+    call_func(2)
+  elif( choice == '4' ):
+    call_func(3)
+  else:
+    print('Did not understand "'+choice+'" Have you tried "help"?')