Merge pull request #102 from fabn/otp
Two factor authentication using a token application
This commit is contained in:
Kyle Manna
commit
eb22992a2f
@ -1,12 +1,13 @@
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# Original credit: https://github.com/jpetazzo/dockvpn
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# Leaner build then Ubuntu
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# Smallest base image
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FROM alpine:3.2
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MAINTAINER Kyle Manna <kyle@kylemanna.com>
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RUN echo "http://dl-4.alpinelinux.org/alpine/edge/community/" >> /etc/apk/repositories && \
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apk add --update openvpn iptables bash easy-rsa && \
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echo "http://dl-4.alpinelinux.org/alpine/edge/testing/" >> /etc/apk/repositories && \
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apk add --update openvpn iptables bash easy-rsa openvpn-auth-pam google-authenticator pamtester && \
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ln -s /usr/share/easy-rsa/easyrsa /usr/local/bin && \
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rm -rf /tmp/* /var/tmp/* /var/cache/apk/*
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@ -26,3 +27,6 @@ CMD ["ovpn_run"]
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ADD ./bin /usr/local/bin
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RUN chmod a+x /usr/local/bin/*
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# Add support for OTP authentication using a PAM module
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ADD ./otp/openvpn /etc/pam.d/
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@ -79,6 +79,7 @@ Conveniently, `kylemanna/openvpn` comes with a script called `ovpn_getclient`,
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which dumps an inline OpenVPN client configuration file. This single file can
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then be given to a client for access to the VPN.
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To enable Two Factor Authentication for clients (a.k.a. OTP) see [this document](/docs/otp.md).
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## OpenVPN Details
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@ -50,6 +50,7 @@ usage() {
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echo " -C A list of allowable TLS ciphers delimited by a colon (cipher)."
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echo " -a Authenticate packets with HMAC using the given message digest algorithm (auth)."
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echo " -z Enable comp-lzo compression."
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echo " -2 Enable two factor authentication using Google Authenticator."
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}
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if [ "$DEBUG" == "1" ]; then
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@ -79,7 +80,7 @@ OVPN_AUTH=''
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[ -r "$OVPN_ENV" ] && source "$OVPN_ENV"
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# Parse arguments
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while getopts ":a:C:T:r:s:du:cp:n:DNm:tz" opt; do
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while getopts ":a:C:T:r:s:du:cp:n:DNm:tz2" opt; do
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case $opt in
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a)
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OVPN_AUTH="$OPTARG"
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@ -126,6 +127,9 @@ while getopts ":a:C:T:r:s:du:cp:n:DNm:tz" opt; do
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z)
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OVPN_COMP_LZO=1
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;;
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2)
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OVPN_OTP_AUTH=1
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;;
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\?)
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set +x
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echo "Invalid option: -$OPTARG" >&2
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@ -172,6 +176,7 @@ export OVPN_SERVER_URL OVPN_ENV OVPN_PROTO OVPN_CN OVPN_PORT
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export OVPN_CLIENT_TO_CLIENT OVPN_PUSH OVPN_NAT OVPN_DNS OVPN_MTU OVPN_DEVICE
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export OVPN_TLS_CIPHER OVPN_CIPHER OVPN_AUTH
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export OVPN_COMP_LZO
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export OVPN_OTP_AUTH
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# Preserve config
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if [ -f "$OVPN_ENV" ]; then
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@ -233,6 +238,12 @@ for i in "${OVPN_PUSH[@]}"; do
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echo push \"$i\" >> "$conf"
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done
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# Optional OTP authentication support
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if [ -n "$OVPN_OTP_AUTH" ]; then
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echo -e "\n\n# Enable OTP+PAM for user authentication" >> "$conf"
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echo "plugin /usr/lib/openvpn/plugins/openvpn-plugin-auth-pam.so openvpn" >> "$conf"
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fi
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set +e
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# Clean-up duplicate configs
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@ -85,6 +85,11 @@ $OVPN_ADDITIONAL_CLIENT_CONFIG
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echo "auth $OVPN_AUTH"
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fi
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if [ -n "$OVPN_OTP_AUTH" ]; then
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echo "auth-user-pass"
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echo "auth-nocache"
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fi
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if [ -n "$OVPN_COMP_LZO" ]; then
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echo "comp-lzo"
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fi
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33
bin/ovpn_otp_user
Executable file
33
bin/ovpn_otp_user
Executable file
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#!/bin/bash
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#
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# Generate OpenVPN users via google authenticator
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#
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if ! source "$OPENVPN/ovpn_env.sh"; then
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echo "Could not source $OPENVPN/ovpn_env.sh."
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exit 1
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fi
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if [ "x$OVPN_OTP_AUTH" != "x1" ]; then
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echo "OTP authentication not enabled, please regenerate configuration using -2 flag"
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exit 1
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fi
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if [ -z $1 ]; then
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echo "Usage: ovpn_otp_user USERNAME"
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exit 1
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fi
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# Ensure the otp folder is present
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[ -d /etc/openvpn/otp ] || mkdir -p /etc/openvpn/otp
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# Binary is present in image, save an $user.google_authenticator file in /etc/openvpn/otp
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if [ "$2" == "interactive" ]; then
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# Authenticator will ask for other parameters. User can choose rate limit, token reuse policy and time window policy
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# Always use time base OTP otherwise storage for counters must be configured somewhere in volume
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google-authenticator --time-based --force -l "${1}@${OVPN_CN}" -s /etc/openvpn/otp/${1}.google_authenticator
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else
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google-authenticator --time-based --disallow-reuse --force --rate-limit=3 --rate-time=30 --window-size=3 \
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-l "${1}@${OVPN_CN}" -s /etc/openvpn/otp/${1}.google_authenticator
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fi
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72
docs/otp.md
Normal file
72
docs/otp.md
Normal file
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# Using two factor authentication for users
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Instead of relying on complex passwords for client certificates (that usually get written somewhere) this image
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provides support for two factor authentication with OTP devices.
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The most common app that provides OTP generation is Google Authenticator ([iOS](https://itunes.apple.com/it/app/google-authenticator/id388497605?mt=8) and
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[Android](https://play.google.com/store/apps/details?id=com.google.android.apps.authenticator2&hl=it)) you can download it
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and use this image to generate user configuration.
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## Usage
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In order to enable two factor authentication the following steps are required.
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* Generate server configuration with `-2` option
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docker run --volumes-from $OVPN_DATA --rm fabn/openvpn ovpn_genconfig -u udp://vpn.example.com -2
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* Generate your client certificate (possibly without a password since you're using OTP)
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docker run --volumes-from $OVPN_DATA --rm -it fabn/openvpn easyrsa build-client-full <user> nopass
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* Generate authentication configuration for your client. -t is needed to show QR code, -i is optional for interactive usage
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docker run --volumes-from $OVPN_DATA --rm -t fabn/openvpn ovpn_otp_user <user>
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The last step will generate OTP configuration for the provided user with the following options
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```
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google-authenticator --time-based --disallow-reuse --force --rate-limit=3 --rate-time=30 --window-size=3 \
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-l "${1}@${OVPN_CN}" -s /etc/openvpn/otp/${1}.google_authenticator
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```
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It will also show a shell QR code in terminal you can scan with the Google Authenticator application. It also provides
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a link to a google chart url that will display a QR code for the authentication.
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**Do not share QR code (or generated url) with anyone but final user, that is your second factor for authentication
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that is used to generate OTP codes**
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Here's an example QR code generated for an hypotetical user@example.com user.
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Generate client configuration for `<user>` and import it in OpenVPN client. On connection it will prompt for user and password.
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Enter your username and a 6 digit code generated by Authenticator app and you're logged in.
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## TL;DR
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Under the hood this configuration will setup an `openvpn` PAM service configuration (`/etc/pam.d/openvpn`)
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that relies on the awesome [Google Authenticator PAM module](https://github.com/google/google-authenticator).
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In this configuration the `auth` part of PAM flow is managed by OTP codes and the `account` part is not enforced
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because you're likely dealing with virtual users and you do not want to create a system account for every VPN user.
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`ovpn_otp_user` script will store OTP credentials under `/etc/openvpn/otp/<user>.google_authentication`. In this
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way when you take a backup OTP users are included as well.
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Finally it will enable the openvpn plugin `openvpn-plugin-auth-pam.so` in server configuration and append the
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`auth-user-pass` directive in client configuration.
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## Debug
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If something is not working you can verify your PAM setup with these commands
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```
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# Start a shell in container
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docker run --volumes-from $OVPN_DATA --rm -it fabn/openvpn bash
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# Then in container install pamtester utility
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apt-get update && apt-get install -y pamtester
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# To check authentication use this command that will prompt for a valid code from Authenticator APP
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pamtester -v openvpn <user> authenticate
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```
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If you configured everything correctly you should get authenticated by entering a OTP code from the app.
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7
otp/openvpn
Normal file
7
otp/openvpn
Normal file
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# Uses google authenticator library as PAM module using a single folder for all users tokens
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# User root is required to stick with an hardcoded user when trying to determine user id and allow unexisting system users
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# See https://github.com/google/google-authenticator/tree/master/libpam#secretpathtosecretfile--usersome-user
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auth required pam_google_authenticator.so secret=/etc/openvpn/otp/${USER}.google_authenticator user=root
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# Accept any user since we're dealing with virtual users there's no need to have a system account (pam_unix.so)
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account sufficient pam_permit.so
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81
tests/otp.sh
Executable file
81
tests/otp.sh
Executable file
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#!/bin/bash
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set -ex
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OVPN_DATA=basic-data-otp
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CLIENT=travis-client
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IMG=kylemanna/openvpn
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OTP_USER=otp
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# Function to fail
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abort() { cat <<< "$@" 1>&2; exit 1; }
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#
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# Create a docker container with the config data
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#
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docker run --name $OVPN_DATA -v /etc/openvpn busybox
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ip addr ls
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SERV_IP=$(ip -4 -o addr show scope global | awk '{print $4}' | sed -e 's:/.*::' | head -n1)
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# Configure server with two factor authentication
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docker run --volumes-from $OVPN_DATA --rm $IMG ovpn_genconfig -u udp://$SERV_IP -2
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# nopass is insecure
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docker run --volumes-from $OVPN_DATA --rm -it -e "EASYRSA_BATCH=1" -e "EASYRSA_REQ_CN=Travis-CI Test CA" $IMG ovpn_initpki nopass
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docker run --volumes-from $OVPN_DATA --rm -it $IMG easyrsa build-client-full $CLIENT nopass
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# Generate OTP credentials for user named test, should return QR code for test user
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docker run --volumes-from $OVPN_DATA --rm -it $IMG ovpn_otp_user $OTP_USER | tee client/qrcode.txt
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# Ensure a chart link is printed in client OTP configuration
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grep 'https://www.google.com/chart' client/qrcode.txt || abort 'Link to chart not generated'
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grep 'Your new secret key is:' client/qrcode.txt || abort 'Secret key is missing'
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# Extract an emergency code from textual output, grepping for line and trimming spaces
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OTP_TOKEN=$(grep -A1 'Your emergency scratch codes are' client/qrcode.txt | tail -1 | tr -d '[[:space:]]')
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# Token should be present
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if [ -z $OTP_TOKEN ]; then
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abort "QR Emergency Code not detected"
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fi
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# Store authentication credentials in config file and tell openvpn to use them
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echo -e "$OTP_USER\n$OTP_TOKEN" > client/credentials.txt
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# Override the auth-user-pass directive to use a credentials file
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docker run --volumes-from $OVPN_DATA --rm $IMG ovpn_getclient $CLIENT | sed 's/auth-user-pass/auth-user-pass \/client\/credentials.txt/' | tee client/config.ovpn
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#
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# Fire up the server
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#
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sudo iptables -N DOCKER || echo 'Firewall already configured'
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sudo iptables -I FORWARD -j DOCKER || echo 'Forward already configured'
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# run in shell bg to get logs
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docker run --name "ovpn-test" --volumes-from $OVPN_DATA --rm -p 1194:1194/udp --privileged $IMG &
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#for i in $(seq 10); do
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# SERV_IP=$(docker inspect --format '{{ .NetworkSettings.IPAddress }}')
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# test -n "$SERV_IP" && break
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#done
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#sed -ie s:SERV_IP:$SERV_IP:g client/config.ovpn
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#
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# Fire up a client in a container since openvpn is disallowed by Travis-CI, don't NAT
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# the host as it confuses itself:
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# "Incoming packet rejected from [AF_INET]172.17.42.1:1194[2], expected peer address: [AF_INET]10.240.118.86:1194"
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#
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docker run --rm --net=host --privileged --volume $PWD/client:/client $IMG /client/wait-for-connect.sh
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#
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# Client either connected or timed out, kill server
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#
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kill %1
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#
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# Celebrate
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#
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cat <<EOF
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___________
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< it worked >
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-----------
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\ ^__^
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\ (oo)\_______
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(__)\ )\/\\
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||----w |
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EOF
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