Phish Market Order Management (100 pts)
Funny (449 pts)
Description
What is this funny file? 🤪
Solution
Given .pyc file, at first i tried to decompile using pycdc but it failed. After that i tried to use pycdas to show the opcode of compiled python.
Copy 136 LOAD_NAME 34 : input
138 PUSH_NULL
140 LOAD_CONST 4 : 'Key > '
142 CALL 1
150 LOAD_ATTR 71 : encode
170 CALL 0
178 STORE_NAME 36 : key
180 LOAD_NAME 34 : input
182 PUSH_NULL
184 LOAD_CONST 5 : 'IV > '
186 CALL 1
194 LOAD_ATTR 71 : encode
214 CALL 0
222 STORE_NAME 37 : iv
224 LOAD_NAME 38 : len
226 PUSH_NULL
228 LOAD_NAME 36 : key
230 CALL 1
238 LOAD_CONST 6 : 32
240 COMPARE_OP 88 ( == )
244 POP_JUMP_IF_FALSE 111 (to 468 )
248 LOAD_NAME 38 : len
250 PUSH_NULL
252 LOAD_NAME 37 : iv
254 CALL 1
262 LOAD_CONST 7 : 16
264 COMPARE_OP 88 ( == )
268 POP_JUMP_IF_FALSE 99 (to 468 )
272 LOAD_NAME 4 : unpad
274 PUSH_NULL
276 LOAD_NAME 1 : AES
278 LOAD_ATTR 78 : new
298 PUSH_NULL
300 LOAD_NAME 36 : key
302 LOAD_NAME 1 : AES
304 LOAD_ATTR 80 : MODE_CBC
324 LOAD_NAME 37 : iv
326 CALL 3
334 LOAD_ATTR 83 : decrypt
354 LOAD_CONST 8 : b '\x1fQer\xec\xb6\x05\xee\xc0g/\x82\x0c\xdb\xecZ\x13\xf8\x08\x01\tB:\xe4\xbdkb/r\xba\xf6\xc0\xe9\xe6M\xf7\xa1\x02&\x17p\x7f)\xb4\xe0\xdf\xe8w'
356 CALL 1
364 LOAD_NAME 1 : AES
366 LOAD_ATTR 84 : block_size
386 CALL 2
394 STORE_NAME 43 : decrypted
396 LOAD_CONST 9 : b 'INTIGRITI'
398 LOAD_NAME 43 : decrypted
400 CONTAINS_OP 0 ( in )
404 POP_JUMP_IF_FALSE 30 (to 466 )
408 LOAD_NAME 6 : print
410 PUSH_NULL
412 LOAD_CONST 10 : 'gg'
414 CALL 1
422 POP_TOP
424 LOAD_NAME 6 : print
426 PUSH_NULL
428 LOAD_NAME 43 : decrypted
430 LOAD_ATTR 89 : decode
450 CALL 0
458 CALL 1 Looking at above code we can see that there is 2 input processed (key and iv) and there is no value check. The check only for the length of IV and KEY, after that there will be check for the decrypted value which is the flag. So lets continue the analysis. Right after above code, there is a
Copy 476 STORE_NAME 45 : i_wonder_what_this_decrypts_to
478 LOAD_NAME 4 : unpad
480 PUSH_NULL
482 LOAD_NAME 1 : AES
484 LOAD_ATTR 78 : new
504 PUSH_NULL
506 LOAD_CONST 12 : b '/\xa0\xaa<?\xb54q\xdb\x00\x8e\xfe w\xae\x89\xf3R3\xd7.\x83c\xe6\xb6E\xac|\xfd\x92\x95j'
508 LOAD_NAME 1 : AES
510 LOAD_ATTR 80 : MODE_CBC
530 LOAD_CONST 13 : b '\x1fdu\xae\x8f\x9a\xa5\x8b,\x94\xa0T\xe5ib\xd0'
532 CALL 3
540 LOAD_ATTR 83 : decrypt
560 LOAD_NAME 45 : i_wonder_what_this_decrypts_to
562 CALL 1
570 LOAD_NAME 1 : AES
572 LOAD_ATTR 84 : block_size
592 CALL 2 There is key and iv also ciphertext (i_wonder_what_this_decrypts_to) in the code that can we use to do the decryption. It should be called but never printed, so lets construct by ourself.
Copy from Crypto . Cipher import AES
ct = b'\xc0\xae\x13\x8a\xbb\x0b\xa1\x95\xf9\x8a\xe0\\\xb6\xc8\xd2\x1fHF*\x0bK\x11\xf2\x82\xfcIk\xd2|\xcdf\xd6@c\x17\xe9\xcc\xdd\x98O\xa5;=<\xea\\\x91\xf2\xc0I\x901)\x8bH\xab\xda}g\x95\x0f#<YN\x03\x94n\xd1\xed\xcf\x9a\xc4\xefU\x99\x92\xe7\xf0&^\xd9\xb9\xc7U\x7f\xce\x0eQ;9dU\xf2\x88\x17\xe2\xc0Q\x93&\xeb\x1f\xf9\'"$\x08?\x83~\xb1\xc8HK\x07\xce\xb2\x10\xd1\x9d\x99k\xba)X\xc5\x08\xec\xe7]\x81s\x9b\xdfsl\xad\xbc 8TM\xd9\xa1em;\xec\x03E\xa5EJ\xbaT:\'\xa3\xa9\xf4\xa9\x0b\xadL\xaer\xf1\x84\x02bI\xe3Ym-&\xb6\xae\\c\xa0\xbcJ@\xaf\xf9\x1d\x8bY\xa3\xa5\xe5b\xf3\xf1\x99b\xf2~\xbd\xf3\xd6\xf5m,\x82=u\x98G\x1b\x86s6\xcb\xf8x\xa9\x16\xfc\xe35\xd8\xca\x17K\xa4\xc6\x04d:\xbaN \xed\x15`\x8f\xd1\xe1\xfdHhr\xbc\xb08V\xb8\x8d\x83\x8a\xf2\x8e{\xe0M\xffs=\xfb\x8d;\xdf\xdd\xc1\x0fm\xeb{\xb5\x9bm\x83\xe7\xf9\x91F\xc0C\xdfP\rG\xd6\xfa\xd7Lb\x8eA\xe4\x008\xf2\xad\xd8\x0f\x9d\xb8\xbfM@\xf4\xca\xf4\xb2\xbbi\x0c\xff\x0fu\x9cT\x0b\xf8\x8e\x9c\x1e\xca\xbc\xcd\xaaG\xd9\x17xp\xd1B7\x0f\xe0\x914\xf1\xdb\xeczH\xbbc\xde\xfcyGA/\xce\x86\x91\xec\xe5:\xc1\x03\x8d]\x90J^\xdc\xa9+\x03Xh\xc3\xe9\x1cDxd\x1b\x0fF\x1f\x99\x18\x8e9DA{\x80\xea\xcf\xb0\xeb\xb0K\x8f\xe4\x07\x1f\x8e\x04n\xb8t\xe9\x13R\xf39\xf1\x17\x05\xfb\x00\xf8\xca\xfa}K\xa6\x8e+\xd5\xa9\x04\xb9I\xab+w\x93\xa8\xfek\xd3\x8bJt\xe3\xfea\xa1 \xb7\xb9\xae\x81\xe2:\xfc\x0b\x85\x15\xe4s\xef:xF\xd9\x83\xddi4\x9e6!\xc2\xbaP\\\xb4V6%\xc0"x\xd1\x15\xc1\x07\x10\xd0\xf9\x96\xee\xd6\xf1)\x9e\xe3\xb9\xe3T\xec\xdd\x8alF\x88\x101U\xed\xb8\xbcd\xfc\x02\xb3\xb4B\x04\xd4g\xc8\xc7\x83\x89^^\xc4\xfc\x02\xca\xcd\xb9\xa7\\|yU\xb71\xb4>\xa9\x1dxv4!\\\xe1\xc1\xe0?\xa3\xaf/(\x16\x0b\xcd\xd3\x99S\x0f\xe4\xfd\xa9\\\x17g\x9e\'N^\xca\x9f^\xec~G\xfa\xd9\xc5 R\xb1\x1f\x95\xaa\xe5:\xa7\x9f\xc2\x8bC\x88\xd2\xa1\xff\x83\x94a\x11J\xdb{\x1bb\x1aBs\x18\xef\xa7\xd7\x1e\xc3\xa4\xff\xa9v:M\xb2\xc59\x98\xe4f\x13!\xf5mz\xb1\x15\xdc\xf5x\xd3g\x0e%t\xda\x9aV\x0cQ\xe5Z{s5\xb1C\xe2!\xdf\xc4z\xaa9^/y\x01^\x99\xdb)4\x02,C\x16tQ\xa2Rj\x80f\xc5U\t\xbd\x1d\xaf/\xaf\x9b\x8cv\xd5\n\x0b\xf6$3\x97Ac\xd6\xff\xc0\x86\xe3\xe3\x1d\x87T\x1d\x8b\xab%S\x8a!\x9f\x1b\x9a$\xdb:\xf47\xa7,\x1cY\x9c*\xec\xcbt1\x9c\x9euGs\x18t\xf6\x81\xeb\xe0Dd\xedx\x02\xec"\xab\x80Bh\x03\xcb\x86\xe1*K\xa5O\xa3\xc2,q~\x87\x8a%\xcc%\x0c\xda-9F)\x00\x8b\xbe\x85\x17\xadl\xd2\xb0\x8c\x8e;U*\xfc4\xd6\r>\x04\xbe\x7f\x88\xc7T\xbd0\xa6\xe85\xa9.\x19\x8d\xfa%\x85\n\xe2\x84\xa8&\xcd\'\xb9\xd6\xebK\x8d\x10}\xc2\xd1\xde@9Uf\xa4_\xa2\xb9X\xd6;\xf9I\xcfc\xfc6\x94\xa5\x834\xbeBD\xfa\xfd\xb8.\x82\xfb)a\xf6L\x95V#\x05\xea}6\xe0C\xf7\xf4\xd3\xed\xba\x02v\xe5 \xcch,{\xad\xc7\xfc\xe1\xaf\xb3\x14R\xdb1\x07JK:g8\x8b\x9bw\x17\x1d\x13\x8ff\x8a\x0e\x98\xcd\xc4\xb1e^\x8c\xbai\x05\xa2\x9e\xc9\xd8{ D\x9c\x0f\xc1\x8a\x0b\x92\'\xed \x8f,\x00o\xa3\xb8%X\xa3\xde\xec\xfdu\x1a\xc9\xac\xfd\x1f\xf9<|\xd4G\x1a.\xac^\xfc\xc9I\x1fkG\xe9\xa1\x0e\xd2\x1b\x90\xb7\xfd\xd0.{\x00d6Y\x06\xcb,L\x9a\x82\xb5\xe6\x8f\xedp=\xbf\xbdFP\x88\xdf!\x0f}]\xecK\x0b3\x97f\xf6\'\x90\xe7\x9ex:xE\x9c\xe0\xbe\x14\xc8\x0f\xa3\xc8\xdag1\xe5{\xe1i|=\x14\x81wy\xb8W\xe7?j\x95;p\x1a\x95\xc7#6\xc3\x00\xec8\xae;\xc9\xf7\xcc\x0f\xb4K\x17w\x1f\xc9]\xa8D&\xb1\xacrs\xbeI\xc7\xab\xf29s\x85\xd7\xaf0\xb0|\x13\xa6\x96\x8f\xe2\x97\x84\x8ag\xf3\xb9ow!b\xa8\xd1\x83a[*$\x8a\xfdp\xc2\x7f\xb1f\xd4\x90z\xe3V\x16\xd8\xed\xa2@\n_\xb4\xd2)\xd4\x14\x85\xbay\xf65#3\xbf\x14\xbf\x1a\xb4\xcb\xd9\xc7\x0f\xe8\xa5!\xa0\xae\x00\x9a\xdb\xd8\xfbg\x8f\x99\xca&\x9f\xe7\x0c\xf3\x03\xd3rw\xe2P\x8c\x01\x0b\xa14-U\xb3\x8b?\x94\xfd\xed#\x99w4\xa2\xf7\xfaS\x10\xa5F\xcbY\x1a\xe7\x87I\xed\x02t,|\xb6c\x8f\xa4)\xa7\x8e\xe2\x18<\xaf\x05z g\xda\xa3\x19\xefq\xe4?\x92\xfdj+y}|\xc6\r}\xad\xd8\xecp\x96v\x8ah\x8b_\xec?\xfbpg\xc5\xfe\x9d=\x063\x17\x96\xe2>\xb1\xed-l\x95b\xb6\x81\xebF-\x1b\x12\xc2\x0b\xdeG\xbd\xdc\xe3\xf56u\xfd\x14\x17V\x8c\x87\x17_m?\xf7\xc3\xc2\xf0\x80;\x03\xea\xc9\xfd\x93~\xeff\x9b\xc5\r\x92\x9atb\xf9\x16\x8c&m4\xb5/F@\x12\')\xea\xff\x97\xf5C;\xd7\x08\xa0\xac`\xc5#\x8b\x80\t\xe4\xf1\x99\x81\xc9\xa7g\xe0\xb1\x02)CZVz\xa6\xcb\x84@!\x98\xf9n \xa0e.3\xa3I\xe8\xcd\x8a\x9d\xb6\xdf\x18G\xdd\xf8T6&\xaa\xde\xb6\x9d\xfb\xdb\x17\x00H\xe3Lm|\xc8\x80\xb0\x03\xd1\xd2\xaaw~\xa0\x00P\x1f\x1a_\x8b\t\x81\xc8p\xfa.\xfb\xd8;\x13\xbb\x80$\xe3\xa4\x05*\x91\x9eD$cc\xaf@\x9b\xaa\xb7&\xaf\x1a\xa1L/X\xc8\xafW\xa3\xb6\xd1\r\xa4\xe8\x91 ^4\xd4\xc7V7\xc6\xe4\x11\x12\xe0{x\x85\xbb\x92\x07\xc0\xd3\xec\xf2JcX\xdb\xcd\xda\xae\x80\xfa\x92\xae\xae&\x07\xaf\x86\xf8i\xabai\xed\x0c`'
key = b '/\xa0\xaa<?\xb54q\xdb\x00\x8e\xfe w\xae\x89\xf3R3\xd7.\x83c\xe6\xb6E\xac|\xfd\x92\x95j'
iv = b '\x1fdu\xae\x8f\x9a\xa5\x8b,\x94\xa0T\xe5ib\xd0'
cipher = AES . new (key, AES.MODE_CBC, iv)
print (cipher. decrypt (ct). decode ()) Now come to the part that need us to guess what is the objective that the author want, by reading above text again by again i understand that we need to reconstruct the original code including the position (row and column). Before i got the objective i tried to do analysis on the variable initialized (a-z) and i found that all the values are 0 and the code only put the variable without doing nothing. Now, lets take a look on the opcode again
Copy 32 LOAD_CONST 0 : 0
34 COPY 1
36 STORE_NAME 8 : a
38 COPY 1
40 STORE_NAME 9 : b
42 COPY 1
44 STORE_NAME 10 : c
46 COPY 1
48 STORE_NAME 11 : d
50 COPY 1
52 STORE_NAME 12 : e
54 COPY 1
56 STORE_NAME 13 : f
58 COPY 1
60 STORE_NAME 14 : g
62 COPY 1
64 STORE_NAME 15 : h
66 COPY 1
68 STORE_NAME 16 : i
--------------------------------snip----------------------------------------
600 POP_TOP
602 LOAD_NAME 9 : b
604 POP_TOP
606 LOAD_NAME 25 : r
608 POP_TOP
610 LOAD_NAME 32 : y
612 POP_TOP
614 LOAD_NAME 9 : b
616 POP_TOP
618 LOAD_NAME 12 : e
620 POP_TOP
622 LOAD_NAME 13 : f
624 POP_TOP
626 LOAD_NAME 12 : e
628 POP_TOP
630 LOAD_NAME 17 : j
632 POP_TOP
634 LOAD_NAME 21 : n
636 POP_TOP
638 LOAD_NAME 18 : k
640 POP_TOP
642 LOAD_NAME 16 : i
644 POP_TOP
646 LOAD_NAME 11 : d
648 POP_TOP
650 LOAD_NAME 22 : o
652 POP_TOP
654 LOAD_NAME 26 : s
656 POP_TOP
658 LOAD_NAME 9 : b
660 POP_TOP
662 LOAD_NAME 22 : o
664 POP_TOP
666 LOAD_NAME 14 : g
668 POP_TOP
670 LOAD_NAME 28 : u
--------------------------------snip---------------------------------------- The code above that i said it does nothing. During the disassembling process of the pyc file using pycdas, i found there is option --pycode-extra and it will show Line Number Table like below
By trying to do the dis with our own code i found that Line Number table consist information about column and row, which is that all we need to solve this challenge. Below is my flow for solving the challenge.
save dis output from line 24 until line 30
reconstruct the original code by knowing each variable location (row and col)
print the map to get the key
get the value for each iv coordinate
Copy import marshal
import types
f = open ( 'funny.pyc' , 'rb' )
f . read ( 16 )
code_object = marshal . load (f)
list_col = []
for i in code_object . co_positions ():
if i [ 0 ] != None :
if i [ 0 ] <= 30 and i [ 0 ] >= 24 :
list_col . append (i)
mapp = [[ ' ' for j in range ( 600 ) ] for i in range ( 7 ) ]
counter = - 1
f2 = open ( "output2.dis" , "r" ). read (). split ( "\n" )
for i in range ( len (list_col)):
assert list_col [ i ] [ 3 ] - list_col [ i ] [ 2 ] == 1
if f2 [ i ]. split ( " " ) [ 2 ] != "" :
counter += 1
if "LOAD_NAME" in f2 [ i ]:
mapp [ counter ] [list_col [ i ] [ 2 ]] = f2 [ i ]. split ( "(" ) [ - 1 ][ 0 ]
if mapp [ counter ] [list_col [ i ] [ 2 ] + 1 ] != ' ' :
print ( "what" )
exit ()
else :
mapp [ counter ] [list_col [ i ] [ 2 ] + 1 ] = ';'
for i in mapp :
print ( '' . join (i)) For the IV just add the following code in the end
Copy coord_iv = [( 476 , 6 ) , ( 468 , 5 ) , ( 282 , 6 ) , ( 506 , 6 ) , ( 420 , 3 ) , ( 492 , 0 ) , ( 192 , 6 ) , ( 56 , 6 ) , ( 144 , 3 ) , ( 324 , 0 ) , ( 360 , 1 ) , ( 352 , 6 ) , ( 30 , 1 ) , ( 260 , 0 ) , ( 298 , 1 ) , ( 480 , 3 )]
iv = ""
for i in coord_iv :
iv += mapp [ i [ 1 ]] [i [ 0 ] ]
print (iv) Last, just decrypt it.
Copy from Crypto . Cipher import AES
key = b 'P05IT1ON4L_INF0RM4TION_1S_GR34T_'
iv = b 'xqamhngxojmobdnh'
ct = b '\x1fQer\xec\xb6\x05\xee\xc0g/\x82\x0c\xdb\xecZ\x13\xf8\x08\x01\tB:\xe4\xbdkb/r\xba\xf6\xc0\xe9\xe6M\xf7\xa1\x02&\x17p\x7f)\xb4\xe0\xdf\xe8w'
cipher = AES . new (key, AES.MODE_CBC, iv)
print (cipher. decrypt (ct)) Flag: INTIGRITI{y0u_7ruly_4r3_7h3_pyc_p4r51n6_m4573r}
