Add docs on passing SSH through to container (#5019)

* Add docs on passing SSH through to container

Wasn't clear how to pass SSH connections through the container, found a
few blog posts which described roughly the same procedure I've
documented here.

Credit should really go to:

* https://blog.sakuragawa.moe/gitea-in-docker-container-and-sharing-ssh-with-host/
* http://www.ateijelo.com/blog/2016/07/09/share-port-22-between-docker-gogs-ssh-and-local-system

Signed-off-by: Dane Elwell <dane.elwell@ukfast.co.uk>

* Add note to resolve @lafriks feedback
This commit is contained in:
Dane 2019-01-05 17:53:23 +00:00 committed by techknowlogick
parent 6311e4ce6a
commit cbc14df16a
1 changed files with 64 additions and 0 deletions

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@ -280,3 +280,67 @@ docker-compose pull
# Start a new container, automatically removes old one
docker-compose up -d
```
# SSH Container Passthrough
Since SSH is running inside the container, you'll have to pass SSH from the host to the
container if you wish to use SSH support. If you wish to do this without running the container
SSH on a non-standard port (or move your host port to a non-standard port) you can forward
SSH connections destined for the container with a little extra setup.
This guide assumes that you have created a user on the host called `git` which shares the same
UID/GID as the container values `USER_UID`/`USER_GID`. You should also create the directory
`/var/lib/gitea` on the host, owned by the `git` user and mounted in the container, e.g.
```
services:
server:
image: gitea/gitea:latest
environment:
- USER_UID=1000
- USER_GID=1000
restart: always
networks:
- gitea
volumes:
- /var/lib/gitea:/data
ports:
- "3000:3000"
- "127.0.0.1:2222:22"
```
You can see that we're also exposing the container SSH port to port 2222 on the host, and binding this
to 127.0.0.1 to prevent it being accessible external to the host machine itself.
On the **host**, you should create the file `/app/gitea/gitea` with the following contents and
make it executable (`chmod +x /app/gitea/gitea`):
```
#!/bin/sh
ssh -p 2222 -o StrictHostKeyChecking=no git@127.0.0.1 "SSH_ORIGINAL_COMMAND=\"$SSH_ORIGINAL_COMMAND\" $0 $@"
```
Your `git` user needs to have an SSH key generated:
```
sudo -u git ssh-keygen -t rsa -b 4096 -C "Gitea Host Key"
```
Still on the host, symlink the container `.ssh/authorized_keys` file to your git user `.ssh/authorized_keys`.
This can be done on the host as the `/var/lib/gitea` directory is mounted inside the container under `/data`:
```
ln -s /var/lib/gitea/git/.ssh/authorized_keys /home/git/.ssh/authorized_keys
```
Then echo the `git` user SSH key into the authorized_keys file so the host can talk to the container over SSH:
```
echo "no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-pty $(cat /home/git/.ssh/id_rsa.pub)" >> /var/lib/gitea/git/.ssh/authorized_keys
```
Now you should be able to use Git over SSH to your container without disrupting SSH access to the host.
Please note: SSH container passthrough will work only if using opensshd in container, and will not work if
`AuthorizedKeysCommand` is used in combination with setting `SSH_CREATE_AUTHORIZED_KEYS_FILE=false` to disable
authorized files key generation.