port google OTP code from kylemanna/openvpn

Dockerfile

@@ -5,7 +5,7 @@ MAINTAINER Pieter Lange <pieter@ptlc.nl>
 
 RUN echo "http://dl-4.alpinelinux.org/alpine/edge/community/" >> /etc/apk/repositories && \
     echo "http://dl-4.alpinelinux.org/alpine/edge/testing/" >> /etc/apk/repositories && \
-    apk add --update openvpn iptables bash easy-rsa libintl inotify-tools && \
+    apk add --update openvpn iptables bash easy-rsa libintl inotify-tools openvpn-auth-pam google-authenticator pamtester && \
     apk add --virtual build_deps gettext &&  \
     cp /usr/bin/envsubst /usr/local/bin/envsubst && \
     ln -s /usr/share/easy-rsa/easyrsa /usr/local/bin && \
@@ -34,4 +34,7 @@ COPY entrypoint.sh /sbin/entrypoint.sh
 COPY watch-portmapping.sh /sbin/watch-portmapping.sh
 COPY openvpn.tmpl $OVPN_TEMPLATE
 
+# Add support for OTP authentication using a PAM module
+ADD ./otp/openvpn /etc/pam.d/
+
 CMD ["/sbin/entrypoint.sh"]

bin/ovpn_otp_user

@@ -0,0 +1,33 @@
+#!/bin/bash
+
+#
+# Generate OpenVPN users via google authenticator
+#
+
+if [ -z $1 ]; then
+    echo "Usage: ovpn_otp_user USERNAME"
+    exit 1
+fi
+
+# Server name is in the form "udp://vpn.example.com:1194"
+if [[ "$OVPN_SERVER_URL" =~ ^((udp|tcp)://)?([0-9a-zA-Z\.\-]+)(:([0-9]+))?$ ]]; then
+    OVPN_PROTO=${BASH_REMATCH[2]};
+    OVPN_CN=${BASH_REMATCH[3]};
+    OVPN_PORT=${BASH_REMATCH[5]};
+else
+    echo "Need to pass in OVPN_SERVER_URL in 'proto://fqdn:port' format"
+    exit 1
+fi
+
+# Ensure the otp folder is present
+[ -d /etc/openvpn/otp ] || mkdir -p /etc/openvpn/otp
+
+# Binary is present in image, save an $user.google_authenticator file in /etc/openvpn/otp
+if [ "$2" == "interactive" ]; then
+    # Authenticator will ask for other parameters. User can choose rate limit, token reuse policy and time window policy
+    # Always use time base OTP otherwise storage for counters must be configured somewhere in volume
+    google-authenticator --time-based --force -l "${1}@${OVPN_CN}" -s /etc/openvpn/otp/${1}.google_authenticator
+else
+    google-authenticator --time-based --disallow-reuse --force --rate-limit=3 --rate-time=30 --window-size=3 \
+        -l "${1}@${OVPN_CN}" -s /etc/openvpn/otp/${1}.google_authenticator
+fi

entrypoint.sh

@@ -75,6 +75,11 @@ if [ -r $OVPN_CRL ]; then
     addArg "--crl-verify" "$OVPN_CRL"
 fi
 
+# Optional OTP authentication support
+if [ -n "${OVPN_OTP_AUTH:-}" ]; then
+    addArg "--plugin" "/usr/lib/openvpn/plugins/openvpn-plugin-auth-pam.so" "openvpn"
+fi
+
 if [ $DEBUG ]; then
     echo "openvpn.conf:"
     cat $OVPN_CONFIG

otp/openvpn

@@ -0,0 +1,7 @@
+# Uses google authenticator library as PAM module using a single folder for all users tokens
+# User root is required to stick with an hardcoded user when trying to determine user id and allow unexisting system users
+# See https://github.com/google/google-authenticator/tree/master/libpam#secretpathtosecretfile--usersome-user
+auth required pam_google_authenticator.so secret=${OVPN_OTP}/${USER}.google_authenticator user=root
+
+# Accept any user since we're dealing with virtual users there's no need to have a system account (pam_unix.so)
+account sufficient pam_permit.so