Added explicit "allow restarts" permission.

Dockerfile

 FROM haproxy:1.9-alpine
 
 EXPOSE 2375
-ENV AUTH=0 \
+ENV ALLOW_RESTARTS=0 \
+    AUTH=0 \
     BUILD=0 \
     COMMIT=0 \
     CONFIGS=0 \

haproxy.cfg

@@ -42,6 +42,7 @@ backend dockerbackend
 frontend dockerfrontend
     bind :2375
     http-request deny unless METH_GET || { env(POST) -m bool }
+    http-request deny if { path,url_dec -m reg -i ^(/v[\d\.]+)?/containers/[^/]+/((stop)|(restart)|(kill)) } ! { env(ALLOW_RESTARTS) -m bool }
     http-request deny if { path,url_dec -m reg -i ^(/v[\d\.]+)?/auth } ! { env(AUTH) -m bool }
     http-request deny if { path,url_dec -m reg -i ^(/v[\d\.]+)?/build } ! { env(BUILD) -m bool }
     http-request deny if { path,url_dec -m reg -i ^(/v[\d\.]+)?/commit } ! { env(COMMIT) -m bool }