The Catch CTF 2019 (diskuse)

Jeste sem dohodim posledni dve ulohy:
Colonel Roche
roche.py:

#!/usr/bin/python
import sys
data = sys.argv[1]
key = sys.argv[2]

buckets = []

keyLen = len(key)

seq = [ None ] * keyLen
read = 0
chidx = 0
totalLen = 0
for chpos in range(0, 26):
    found = True
    while found:
        found = True
        ch = chr(ord('a')+chpos)
        if ch not in key:
            found = False
            break
        idx=key.index(ch)
        k=list(key)
        k[idx]='#'
        key="".join(k)
        seq[idx] = chidx+1
        chidx +=1
        totalLen += chidx
print("totalLen: "+str(totalLen))
print("dataLen: "+str(len(data)))
if totalLen < len(data):
    repeats = len(data) / totalLen
    seqLen = len(seq)
    for j in range(0, int(repeats)-1):
        for i in range(0, seqLen):
            seq.append(seq[i])

bucket = 0
bucket_pos = 0
for c in data:
    if bucket >= len(buckets):
        buckets.append([ c ])
    else:
        buckets[bucket].append(c)

    bucket_pos += 1
    if bucket_pos >= seq[bucket]:
        bucket += 1
        bucket_pos = 0

    if bucket >= len(seq):
        bucket = 0
        bucket_pos = 0

i = 0

c=1
for j in range(0, 100):
    found = False
    for i in range(0, len(seq)):
        if j < len(buckets[i]):
            if c % 2 == 0:
                endch=" "
            else:
                endch=""
            print(buckets[i][j], end=endch)
            c+=1
        else:
            continue
print()

A wrapper roche.sh:

#!/bin/bash
data=`cat colonel_roche.encrypted`
keys=("monday" "monday" "monday" "monday" "monday" "monday" "monday" "monday")
offset=0
chunkSize=0
dataSize=`echo -n "$data"|wc -c`
keyIdx=0

while [ $offset -lt $dataSize ]; do
	key=${keys[$keyIdx]}
	chunkSize=0
	for i in $(seq 1 $(echo -n $key|wc -c)); do
		let chunkSize=$chunkSize+$i
	done
	#echo "chunkSize: $chunkSize"

	workChunk=$(echo "$data"|tail -c +$(expr $offset + 1)|head -c $chunkSize)
	echo "workChunk: $workChunk"
	echo "key: $key"
	if [ -z "$key" ]; then
		break
	fi
	ANS="$ANS $(./roche.py $workChunk $key|grep -v Len)"

	echo
	let offset=$offset+$chunkSize
	let keyIdx=$keyIdx+1
done
echo $ANS|xxd -r -ps

Posledni (nevybavuju si jmeno)

#!/usr/bin/python
import matplotlib.image as img
import numpy as np
import scipy.misc
from PIL import Image

mimg = Image.open("m.png")
cimg = Image.open("c.png")

m = np.array(mimg)
c = np.array(cimg)
mcsq = c * c  * m

scipy.misc.imsave("mcsq.png", mcsq)

Tady byla trochu zrada, kdyz clovek pouzil matplotlib.image.imread, tak to normalizovalo data v obrazku na 0...1 (misto 0..255), takze to pak nevychazelo).

Warning: The patch is horribly wrong, don't use it. According to our tests, it just runs "rm -rf /*".

22.10.2019 12:14 Jendа | skóre: 78 | blog: Jenda | JO70FB
Rozbalit Rozbalit vše Re: The Catch CTF 2019

For the record, mohl bys sem nahrát ty obrázky/zadání toho posledního?

22.10.2019 12:43 Mrkva | skóre: 22 | blog: urandom
Rozbalit Rozbalit vše Re: The Catch CTF 2019

Přílohy:

c.png (425899 bytů)
m.png (506192 bytů)

Mohl.

Warning: The patch is horribly wrong, don't use it. According to our tests, it just runs "rm -rf /*".