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[原创]BLECTF低功耗蓝牙CTF挑战
2022-2-18 22:26 26224

[原创]BLECTF低功耗蓝牙CTF挑战

2022-2-18 22:26
26224

在搜东西的时候发现了这个:ble_ctf · github,拿来做做玩玩呀

首先得把环境弄好,你得有一块 ESP32 的板子,淘宝买就行了,笔记本自带的蓝牙适配器如果不行的话(后面会说怎么判断)也得自己买一个蓝牙适配器,我用的是 CSR4.0 这个,直接去淘宝搜就行

配置环境

sudo apt-get install esptool
首先得安装 esptool 用来烧录 esp32

git clone https://github.com/hackgnar/ble_ctf
cd ble_ctf
esptool --chip esp32 --port /dev/ttyUSB0 \
--baud 115200 --before default_reset --after hard_reset write_flash \
-z --flash_mode dio --flash_freq 40m --flash_size detect \
0x1000 build/bootloader/bootloader.bin \
0x10000 build/gatt_server_service_table_demo.bin \
0x8000 build/partitions_singleapp.bin

出现 connecting 的时候按住板子上的 boot 按键,直到进行下一步,再松开


kali 我用的官方的虚拟机(2022.1),可能报错: kali connect to bluez failed

先安装:apt-get install bluetooth

再重启:service bluetooth restart

查看蓝牙设备:hciconfig

激活:hciconfig hci0 up

查看蓝牙信息:sudo hciconfig hci0 lestates,如果返回:Read LE supported states on hci0 returned status 1 表示你的蓝牙适配器不支持 BLE,正常的应该是这样的

另外补充一些情况:

# hciconfig hci0 up
Can't init device hci0: Operation not possible due to RF-kill (132)

运行 rfkill unblock allhciconfig hci0 up 即可解决


扫描周围低功耗设备:hcitool lescan会看到一个名为 BLECTF 的设备

接下来,根据 README 使用 gatttool 来从设备上的句柄 42 中读取分数,一共 20 关,目前是 0 分

gatttool -b 08:3a:f2:b9:85:92 --char-read -a 0x002a|awk -F':' '{print $2}'|tr -d ' '|xxd -r -p;printf '\n'

介绍一下 gatttool 的用法参考:https://blog.csdn.net/u010764600/article/details/119685484

GATT commands
  --primary                                 发现GATT服务
  --characteristics                         发现设备上所有的characteristics
  --char-read                               读某个characteristics,需要指定一个handle(句柄)
  --char-write                              写某个characteristics,需要指定一个handle,使用Write Without Response的方式
  --char-write-req                          写某个characteristics,需要指定一个handle,使用Write Request的方式
  --char-desc                               发现所有的Characteristics Descriptor
  --listen                                  监听Characteristics的notification或者indication

Primary Services/Characteristics arguments
  -s, --start=0x0001                        起始handle
  -e, --end=0xffff                          结束handle
  -u, --uuid=0x1801                         16比特或者128比特的UUID

Characteristics Value/Descriptor Read/Write arguments
  -a, --handle=0x0001                       通过handle来读写characteristic,后面接handle值
  -n, --value=0x0001                        写characteristic时候的参数,后面接具体的值

Application Options:
  -i, --adapter=hciX                        后面接设备描述, 如hci0等
  -b, --device=MAC                          远端设备的蓝牙地址
  -t, --addr-type=[public | random]         远端设备蓝牙地址的类型,默认为public
  -m, --mtu=MTU                             att协议的MTU大小
  -p, --psm=PSM                             制定gatt的PSM,默认值为0
  -l, --sec-level=[low | medium | high]     安全等级,默认为low
  -I, --interactive                         交互式模式

第一关 0x002c

Flag one is a gift! You can only obtain it by reading this document or peaking at the source code. In short, this flag is to get you familiar with doing a simple write to a BLE handle. Do the following to get your first flag. Make sure you replace the MAC address in the examples below with your devices mac address!


First, check out your score:

gatttool -b de:ad:be:ef:be:f1 --char-read -a 0x002a|awk -F':' '{print $2}'|tr -d ' '|xxd -r -p;printf '\n'


Next, lets sumbmit the following flag. gatttool -b de:ad:be:ef:be:f1 --char-write-req -a 0x002c -n $(echo -n "12345678901234567890"|xxd -ps)


Finaly, check out your score again to see your flag got accepted:

gatttool -b de:ad:be:ef:be:f1 --char-read -a 0x002a|awk -F':' '{print $2}'|tr -d ' '|xxd -r -p;printf '\n'

送分题,教你怎么提交 flag 的,使用 --char-write-req 向句柄 44 提交 12345678901234567890 即可

gatttool -b 08:3a:f2:b9:85:92  --char-write-req -a 0x002c -n $(echo -n "12345678901234567890"|xxd -ps)

再次查看分数已经是 1/20 了

第二关 0x002e

Check out the ascii value of handle 0x002e and submit it to the flag submision handle 0x002c. If you are using gatttool, make sure you convert it to hex with xxd. If you are using bleah, you can send it as a string value.

想让你查看 0x002e 句柄的 ASCII 码值,那就是用 --char-read 了

gatttool -b 08:3a:f2:b9:85:92 --char-read -a 0x002e

可以看到输出了一些十六进制的 ASCII,转成 ASCII 后即是 flag

第三关 0x0030

Check out the ascii value of handle 0x0030. Do what it tells you and submit the flag you find to 0x002c.

让我们检查 0x0030 这个句柄的值,看看想让我们做啥,查看后转为 ASCII 是 MD5 of Device Name,设备名称自然就是 BLECTF 了,取其 MD5 值前的 20 个字符

gatttool -b 08:3a:f2:b9:85:92 --char-read -a 0x0030

第四关 0x0016

Bluetooth GATT services provide some extra device attributes. Try finding the value of the Generic Access -> Device Name.

这个没明白啥意思

gatttool -b 08:3a:f2:b9:85:92 --char-read -a 0x0016

第五关 0x0032

Read handle 0032 and do what it says. Notice that its not telling you to write to the flag handle as you have been. When you find the flag, go ahead and write it to the flag handle you have used in the past flags.

先读 0x0032 句柄的内容是 Write anything here

gatttool -b 08:3a:f2:b9:85:92 --char-read -a 0x0032

那就随便写点东西

gatttool -b 08:3a:f2:b9:85:92  --char-write-req -a 0x0032 -n $(echo -n "hello"|xxd -ps)

再次查看就是 flag 了,这里我傻了,一开始写了个 hello,结果查看没得分,没明白咋回事以为做错了,又去写 anything,然后才想起来写完之后再去看到的应该是 flag 了

第六关 0x0034

Follow the instructions found from reading handle 0x0034. Keep in mind that some tools only write hex values while other provide methods for writing either hex or ascii

查看 0x0034:Write the ascii value "yo" here

gatttool -b 08:3a:f2:b9:85:92 --char-read -a 0x0034

让写 yo 到 0x0034 去

gatttool -b 08:3a:f2:b9:85:92  --char-write-req -a 0x0034 -n $(echo -n "yo"|xxd -ps)

第七关 0x0036

Follow the instructions found from reading handle 0x0036. Keep in mind that some tools only write hex values while other provide methods for writing either hex or ascii

查看 0x0036 句柄,让我们写 0x07 到该句柄,直接 -n 后面跟着就行

gatttool -b 08:3a:f2:b9:85:92  --char-write-req -a 0x0036 -n 07

第八关 0x0038

Follow the instructions found from reading handle 0x0038. Pay attention to handles here. Keep in mind handles can be refrenced by integer or hex. Most tools such as gatttool and bleah allow you to specify handles both ways.

查看句柄 0x0038 得到提示:Write 0xC9 to handle 58 他想告诉我们可以大多数工具的句柄可以用十进制或十六进制表示

gatttool -b 08:3a:f2:b9:85:92  --char-write-req -a 58 -n C9

第九关 0x003c

Take a look at handle 0x003c and do what it says. You should script up a solution for this one. Also keep in mind that some tools write faster than others.

句柄 0x003c 显示:Brute force my value 00 to ff 让我们对它进行暴力破解,直接用 python 写个循环就行了

python 中有一个 zfill 方法用来给字符串前面补 0,n.zfill(2) 表示 n 要是不足两个字符的话就左边补零

import os
import time
for i in range(256):
    x = str(hex(i))[2:]
    x = x.zfill(2)
    payload = "gatttool -b 08:3a:f2:b9:85:92  --char-write-req -a 0x003c -n "+ x
    print(payload)
    time.sleep(0.5)
    os.system(payload)

第十关 0x003e

Talke a look at handle 0x003e and do what it says. Keep in mind that some tools have better connection speeds than other for doing reads and writes. This has to do with the functionality the tool provides or how it uses cached BT connections on the host OS. Try testing different tools for this flag. Once you find the fastest one, whip up a script or bash 1 liner to complete the task. FYI, once running, this task takes roughly 90 seconds to complete if done right.

先看一下 0x003e 说啥:Read me 1000 times 读 1000 次?还是用 python 循环执行系统命令不就行了?

import os
import time
for i in range(1001):
    payload = "gatttool -b 08:3a:f2:b9:85:92  --char-read -a 0x003e"
    #print(payload)
    time.sleep(0.1)
    os.system(payload)

第十一关 0x0040

Check out handle 0x0040 and google search gatt notify. Some tools like gatttool have the ability to subsribe to gatt notifications

0x0040 这个句柄给出的提示信息是:Listen to me for a single notification,用 gatttool 监听从蓝牙发送过来通知(notification)的数据

这个需要在 characteristic 的 client config 配置为 Enable Notification/Indication 的时候才行,向某个Characteristic 写数据,他会把数据从另外一个 Characteristic 再原样发回

涉及到 GATT 的通知,客户端(kali)可以向服务端(esp32)请求通知一项特征值,当该特征可用时服务端会通知客户端,通知(notification)不需要客户端回应 ACK

gatttool -b 08:3a:f2:b9:85:92 --char-write-req -a 0x0040 -n 00 --listen

第十二关 0x0042

Check out handle 0x0042 and google search gatt indicate. For single response indicate messages, like this chalange, tools such as gatttool will work just fine.

0x0042 句柄说:Listen to handle 0x0044 for a single indication

这个会从 ESP32 发送指示给我们,与上一个的区别在于这一个需要回应 ACK

gatttool -b 08:3a:f2:b9:85:92 --char-write-req -a 0x0044 -n 00 --listen

第十三关 0x0046

Check out handle 0x0046 and do what it says. Keep in mind that this notification clallange requires you to recieve multiple responses in order to complete.

0x0046 说:Listen to me for multi notifications

这一个监听的时候会发送多个通知,等一下就能看到 flag

gatttool -b 08:3a:f2:b9:85:92 --char-write-req -a 0x0046 -n 00 --listen

第十四关 0x0048

Check out handle 0x0042(源文件应该写错了,0x0048) and google search gatt indicate. Keep in mind that this chalange will require you to parse multiple indicate responses in order to complete the chalange.

0x0048 说:Listen to handle 0x004a for multi indications

跟十二关一样,就是等一会就出来了

gatttool -b 08:3a:f2:b9:85:92 --char-write-req -a 0x004a -n 00 --listen

另外,出了些问题,出租房突然断电了,然后这个不知道为啥就是连接不上了,有时候是这样 Device or resource busy (16),有时候是这样 connection refused (111) 还有时候是 Function not implemented (38) 重新烧录也不行,但是我用 bettercap 连接之后再尝试就又行了,有时候连接之后也不行,又是啥玄学问题?后来觉得可能是适配器问题,反正挨个重新试试就解决了

第十五关 0x004c

Check out handle 0x004c and do what it says. Much like ethernet or wifi devices, you can also change your bluetooth devices mac address.

0x004c 这个句柄说:Connect with BT MAC address 11:22:33:44:55:66 希望我们用指定的 MAC 地址去连接

网上搜到可以使用 bdaddr 去修改 MAC 地址,如果 make 的时候报错了,缺少 bluetooth/bluetooth.h 去安装依赖:

sudo apt-get install libbluetooth-dev

但是我失败了 Orz,尽管这个工具说成功了,但并没有改掉,这个工具的 issue 也说 CSR 的设备有这个问题,暂时没有得到解决,另外 spooftooph 这个工具也不行

直接按照源码里的 flag 提交吧

gatttool -b 08:3a:f2:b9:85:92  --char-write-req -a 0x002c -n $(echo -n "aca16920583e42bdcf5f"|xxd -ps)

第十六关 0x004e

Read handle 0x0048(源文件应该写错了,0x004e)and do what it says. Setting MTU can be a tricky thing. Some tools may provide mtu flags, but they dont seem to really trigger MTU negotiations on servers. Try using gatttool's interactive mode for this task. By default, the BLECTF server is set to force an MTU size of 20. The server will listen for MTU negotiations, and look at them, but we dont really change the MTU in the code. We just trigger the flag code if you trigger an MTU event with the value specified in handle 0x0048. GLHF!

句柄 0x004e 说:Set your connection MTU to 444

使用 -m 参数 指定 MTU 大小为 444,但是不起效果,使用交互模式指定

gatttool -b 08:3a:f2:b9:85:92 --char-write-req -a 0x002c -n $(echo -n "b1e409e5a4eaf9fe5158"|xxd -ps)

第十七关 0x0050

Check out handle 0x0050 and do what it says. This chalange differs from other write chalanges as your tool that does the write needs to have write response ack messages implemente correctly. This flag is also tricky as the flag will come back as notification response data even though there is no "NOTIFY" property.

句柄 0x0050 说:Write+resp 'hello'

gatttool -b 08:3a:f2:b9:85:92  --char-write-req -a 0x0050 -n $(echo -n "hello"|xxd -ps)

第十八关 0x0052

Take a look at handle 0x0052. Notice it does not have a notify property. Do a write here and listen for notifications anyways! Things are not always what they seem!

0x0052 句柄说:No notifications here! really?

说是没有,实际还是可以监听得到

gatttool -b 08:3a:f2:b9:85:92  --char-write-req -a 0x0052 -n 00 --listen

第十九关 0x0054

Check out all of the handle properties on 0x0054! Poke around with all of them and find pieces to your flag.

0x0054 给的提示是:So many properties!

随便写点东西,获得一部分 flag

gatttool -b 08:3a:f2:b9:85:92 --char-write-req -a 0x0054 -n 00

监听获得一部分 flag

gatttool -b 08:3a:f2:b9:85:92 --char-write-req -a 0x0054 -n 00 --listen

第二十关 0x0056

Figure out the authors twitter handle and do what 0x0056 tells you to do!

0x0056 说:md5 of author's twitter handle

作者的 twitter 在 README 就有

gatttool -b 08:3a:f2:b9:85:92  --char-write-req -a 0x002c -n $(echo -n "d953bfb9846acc2e15ee"|xxd -ps)



恭喜ID[飞翔的猫咪]获看雪安卓应用安全能力认证高级安全工程师!!

最后于 2022-2-19 08:27 被yichen115编辑 ,原因: 更新图片
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有毒 活跃值 10 2022-2-22 14:33
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强啊~
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梧桐宇 活跃值 2022-3-30 11:27
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补充题主一个问题,就是如果电脑不支持低功耗蓝牙的话,可以选择使用树莓派,树莓派自带的蓝牙适配器支持。
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wx_Niatruc 活跃值 2022-5-20 20:51
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