Dockerfile

FROM alpine:latest
MAINTAINER Jurrian Fahner

#Install packages
RUN apk update && apk upgrade && apk add bash openssh git

#Copy scripts
ADD addkey /usr/bin/
ADD key /usr/bin/
ADD recreatehostfiles /usr/bin/
ADD repo /usr/bin/

#Harden ssh server
ADD sshd_config /etc/ssh/

#Empty motd
RUN echo -n "" > /etc/motd

#Create initial host keys 
WORKDIR /etc/ssh
RUN ssh-keygen -N "" -t ed25519 -f ssh_host_ed25519_key < /dev/null
#RUN ssh-keygen -N "" -t rsa -b 4096 -f ssh_host_rsa_key < /dev/null

#Create git user
RUN adduser -D -s /usr/bin/git-shell git
RUN passwd -d -u git

#Create location where the repositories should be stored
#See for more information: https://git-scm.com/book/en/v1/Git-on-the-Server-Setting-Up-the-Server
RUN mkdir -p /opt/git
WORKDIR /opt
RUN chown -R git: ./git

#Configure ssh 
USER git
WORKDIR /home/git
RUN mkdir .ssh
RUN chmod 700 .ssh
RUN touch .ssh/authorized_keys
RUN touch .ssh/known_hosts
RUN chmod 600 .ssh/authorized_keys

#Usual docker stuf...
EXPOSE 22
USER root
CMD /usr/sbin/sshd -D