安恒杯二月月赛 抗【疫】练习赛 -re- easy-py
新手一枚,如有错误(不足)请指正,谢谢!!
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题目下载:
链接: https://pan.baidu.com/s/1VAdpObsh0tgw4HLMS-Cfjw 提取码: 2020
pyc文件。将其进行在线反编译
得到python代码
import base64
import string
def caser(flag):
enc1 = ''
for i in flag:
enc1 += chr(ord(i) - 5)
return enc1
def rail(flag):
p1 = ''
p2 = ''
p3 = ''
enc2 = ''
for i in range(len(flag)):
j = i % 3
if j == 0:
p1 += flag[i]
continue
if j == 1:
p2 += flag[i]
continue
p3 += flag[i]
enc2 = p1 + p2 + p3
return enc2
def rep(flag):
table1 = 'qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM'
table2 = 'QWERTYUIOPASDFGHJKLZXCVBNMqwertyuiopasdfghjklzxcvbnm'
table = string.maketrans(table1, table2)
return flag.translate(table, '=')
while True:
flag = raw_input('please input flag to check:')
if rep(base64.b64encode(rail(caser(flag)))) == 'ywjCytmRxI9CycWZngD2ncTDkZqYlJrGmhHCxISUnfWSlgfDlJi':
print 'Success!you got it!'
break
continue
print 'try a gain'
根据代码写脚本
import base64
string = "ywjCytmRxI9CycWZngD2ncTDkZqYlJrGmhHCxISUnfWSlgfDlJi"
flag=""
for i in string:
if ord(i)>=65:
flag += chr(ord(i)^32)
else :
flag += i
flag+='='
flag0=str(base64.b64decode(flag),'utf-8')
flag1=[0]*38
for i in range(len(flag0)):
if((i%13)*3+i//13<len(flag0)):
flag1[(i%13)*3+i//13]=flag0[i]
flag1[(i%13)*3+i//13] = chr(ord(flag1[(i%13)*3+i//13])+5)
print("".join(flag1))
得到flag为flag{ca90f038b900ac91471a3fe9b1e38579}