sey ssh pub key from environment variable

Dockerfile

@@ -6,10 +6,14 @@ rm /etc/motd && \
 rm /etc/update-motd.d/10-uname && \
 mkdir /var/run/sshd && \
 sed -i 's/#PasswordAuthentication yes/PasswordAuthentication no/g' /etc/ssh/sshd_config && \
-sed -i 's/X11Forwarding yes/X11Forwarding no/g' /etc/ssh/sshd_config
+sed -i 's/X11Forwarding yes/X11Forwarding no/g' /etc/ssh/sshd_config && \
+if ! [ -d /root/.ssh ]; then mkdir /root/.ssh ; fi && \
+if ! [ -f /root/.ssh/authorized_keys ] ; then touch /root/.ssh/authorized_keys ; fi && \
+chmod 700 /root/.ssh && \
+chmod 400 /root/.ssh/authorized_keys
 
 COPY --from=docker:dind /usr/local/bin/docker /usr/local/bin/
 
 EXPOSE 22
 
-CMD ["/usr/sbin/sshd", "-D"]
+CMD ["/bin/bash", "-c", "echo $SSH_PUBLIC_KEY > /root/.ssh/authorized_keys; /usr/sbin/sshd -D"]