# Inspiration: https://github.com/Tecnativa/docker-socket-proxy/blob/master/haproxy.cfg

global
    maxconn 10

defaults
    timeout connect 30s
    timeout client 30s
    timeout server 1800s

frontend http
    mode http
    bind :::2375 v4v6
    http-request deny unless { src 127.0.0.1 } || { src ::1 } || { src NC_IPV4_PLACEHOLDER } || { src NC_IPV6_PLACEHOLDER }
    # ACL to detect JSON \uXXXX unicode escape sequences in the request body.
    # All values we accept (names, types, etc.) are restricted to plain ASCII
    # (e.g. ^nc_app_[a-zA-Z0-9_.-]+), so a legitimate request never needs one.
    # Without this, an attacker can hide literal strings such as "device" or
    # "Binds" from the other regex-based ACLs below by encoding a character as
    # e.g. "\u0064evice", bypassing those keyword checks entirely.
    acl body_has_unicode_escape req.body -m reg -i "\\\\u[0-9a-f]{4}"
    http-request deny if body_has_unicode_escape

    # docker system _ping
    http-request allow if { path,url_dec -m reg -i ^(/v[\d\.]+)?/_ping$ } METH_GET
    # docker inspect image: GET images/%s/json
    http-request allow if { path,url_dec -m reg -i ^(/v[\d\.]+)?/images/.*/json } METH_GET
    # container inspect: GET containers/%s/json
    http-request allow if { path,url_dec -m reg -i ^(/v[\d\.]+)?/containers/nc_app_[a-zA-Z0-9_.-]+/json } METH_GET
    # container inspect: GET containers/%s/logs
    http-request allow if { path,url_dec -m reg -i ^(/v[\d\.]+)?/containers/nc_app_[a-zA-Z0-9_.-]+/logs } METH_GET
    # container start/stop: POST containers/%s/start containers/%s/stop
    http-request allow if { path,url_dec -m reg -i ^(/v[\d\.]+)?/containers/nc_app_[a-zA-Z0-9_.-]+/((start)|(stop)) } METH_POST
    # container rm: DELETE containers/%s
    http-request allow if { path,url_dec -m reg -i ^(/v[\d\.]+)?/containers/nc_app_[a-zA-Z0-9_.-]+ } METH_DELETE
    # container update/exec: POST containers/%s/update containers/%s/exec
    http-request allow if { path,url_dec -m reg -i ^(/v[\d\.]+)?/containers/nc_app_[a-zA-Z0-9_.-]+/((update)|(exec)) } METH_POST
    # container put: PUT containers/%s/archive
    http-request allow if { path,url_dec -m reg -i ^(/v[\d\.]+)?/containers/nc_app_[a-zA-Z0-9_.-]+/archive } METH_PUT
    # run exec instance: POST exec/%s
    http-request allow if { path,url_dec -m reg -i ^(/v[\d\.]+)?/exec/[a-zA-Z0-9_.-]+/start } METH_POST

    # container create: POST containers/create?name=%s
    # ACL to restrict container name to nc_app_[a-zA-Z0-9_.-]+
    acl nc_app_container_name url_param(name) -m reg -i "^nc_app_[a-zA-Z0-9_.-]+"

    # ACL to restrict the number of Mounts to 1
    acl one_mount_volume req.body -m reg -i "\"Mounts\"\s*:\s*\[\s*(?:(?!\"Mounts\"\s*:\s*\[)[^}]*)}[^}]*\]"
    # ACL to deny if there are any binds
    acl binds_present req.body -m reg -i "\"HostConfig\"\s*:.*\"Binds\"\s*:"
    # ACL to restrict the type of Mounts to volume
    acl type_not_volume req.body -m reg -i "\"Mounts\"\s*:\s*\[[^\]]*(\"Type\"\s*:\s*\"(?!volume\b)\w+\"[^\]]*)+\]"
    # Deny if HostConfig.Binds is present, independently of other mounts or volumes
    http-request deny if { path,url_dec -m reg -i ^(/v[\d\.]+)?/containers/create } nc_app_container_name binds_present
    # Deny if required conditions are not met.
    http-request deny if { path,url_dec -m reg -i ^(/v[\d\.]+)?/containers/create } nc_app_container_name !one_mount_volume type_not_volume METH_POST

    # ACL to restrict container creation, that it has HostConfig.Privileged(by searching for "Privileged" word in all payload)
    acl no_privileged_flag req.body -m reg -i "\"Privileged\""
    # ACL to allow mount volume with strict pattern for name: nc_app_[a-zA-Z0-9_.-]+_data
    acl nc_app_volume_data_only req.body -m reg -i "\"Mounts\"\s*:\s*\[\s*{[^}]*\"Source\"\s*:\s*\"nc_app_[a-zA-Z0-9_.-]+_data\""
    http-request allow if { path,url_dec -m reg -i ^(/v[\d\.]+)?/containers/create } nc_app_container_name !no_privileged_flag nc_app_volume_data_only METH_POST
    # end of container create

    # volume create: POST volumes/create
    # restrict name
    acl nc_app_volume_data req.body -m reg -i "\"Name\"\s*:\s*\"nc_app_[a-zA-Z0-9_.-]+_data\""
    # do not allow to use "device" word e.g., "--opt device=:/path/to/dir"
    acl volume_no_device req.body -m reg -i "\"device\""
    http-request allow if { path,url_dec -m reg -i ^(/v[\d\.]+)?/volumes/create } nc_app_volume_data !volume_no_device METH_POST
    # volume rm: DELETE volumes/%s
    http-request allow if { path,url_dec -m reg -i ^(/v[\d\.]+)?/volumes/nc_app_[a-zA-Z0-9_.-]+_data } METH_DELETE
    # image pull: POST images/create?fromImage=%s
    http-request allow if { path,url_dec -m reg -i ^(/v[\d\.]+)?/images/create } METH_POST
    http-request deny
    default_backend dockerbackend

backend dockerbackend
    mode http
    server dockersocket /var/run/docker.sock