Ovpnmcgen.rb

OpenVPN iOS Configuration Profile Utility

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Generates iOS configuration profiles (.mobileconfig) that configures OpenVPN for use with VPN-on-Demand that are not accessible through the Apple Configurator or the iPhone Configuration Utility.

Although there are many possible VPN-on-Demand (VoD) triggers, this utility currently only implements SSIDMatch, InterfaceTypeMatch, and optionally URLStringProbe. For 'high' (default) security level, the following algorithm is executed upon network changes, in order:

  • If wireless SSID matches any specified with --trusted-ssids, tear down the VPN connection and do not reconnect on demand.
  • Else if wireless SSID matches any specified with --untrusted-ssids, unconditionally bring up the VPN connection on the next network attempt.
  • Else if the primary network interface becomes Wifi (any SSID except those above), unconditionally bring up the VPN connection on the next network attempt.
  • Else if the primary network interface becomes Cellular, leave any existing VPN connection up, but do not reconnect on demand.
  • Else, leave any existing VPN connection up, but do not reconnect on demand.

Note: The other match triggers, such as DNSDomainMatch, DNSServerAddressMatch, and per-connection domain inspection (ActionParameters), are not implemented. I reckon some kind of DSL will need to be built to support them; pull-requests are welcome.

Installation

Install the production version from Rubygems.org:

$ gem install ovpnmcgen.rb

Local Development

Clone the source:

$ git clone https://github.com/iphoting/ovpnmcgen.rb

Build and install the gem:

$ cd ovpnmcgen.rb/
$ bundle install   # install dependencies
# Hack away...
$ rake install     # build and install gem

Usage

Usage: ovpnmcgen.rb generate [options] <user> <device>

  Options:
    -c, --config FILE    Specify path to config file. [Default: .ovpnmcgen.rb.yml]
    --cafile FILE        Path to OpenVPN CA file. (Required)
    --tafile FILE        Path to TLS-Auth Key file.
    --host HOSTNAME      Hostname of OpenVPN server. (Required)
    --proto PROTO        OpenVPN server protocol. [Default: udp]
    -p, --port PORT      OpenVPN server port. [Default: 1194]
    --p12file FILE       Path to user PKCS#12 file. (Required)
    --p12pass PASSWORD   Password to unlock PKCS#12 file.
    --[no-]vod           Enable or Disable VPN-On-Demand. [Default: Enabled]
    --security-level LEVEL Security level of VPN-On-Demand Behaviour: paranoid, high, medium. [Default: high]
    --vpn-uuid UUID      Override a VPN configuration payload UUID.
    --profile-uuid UUID  Override a Profile UUID.
    --cert-uuid UUID     Override a Certificate payload UUID.
    -t, --trusted-ssids SSIDS List of comma-separated trusted SSIDs.
    -u, --untrusted-ssids SSIDS List of comma-separated untrusted SSIDs.
    --url-probe URL      This URL must return HTTP status 200, without redirection, before the VPN service will try establishing.
    --remotes REMOTES   List of comma-separated alternate remotes: "<host> <port> <proto>".
    --ovpnconfigfile FILE Path to OpenVPN client config file.
    -o, --output FILE    Output to file. [Default: stdout]

Configuration

Option flags can be set using environment variables or placed into a YAML formatted file. The default filename .ovpnmcgen.rb.yml will be searched for in ./, and then ~/.

Note: Only for YAML configuration files and environment variables, flags with hyphens (-) are replaced with underscores (_), i.e. --trusted-ssids safe should be trusted_ssids: safe.

Sample:

untrusted_ssids: [dangerous1, dangerous2]
trusted_ssids: [trust]
host: vpn.example.com
cafile: /etc/openvpn/ca.crt
tafile: /etc/openvpn/ta.key
url_probe: https://vpn.example.com/canVPN.php

Security Levels

There are three different security levels to choose from, 'paranoid', 'high' (default), and 'medium'. The algorithm illustrated above is for 'high'.

For 'paranoid' security level, the following algorithm is executed upon network changes, in order:

  • If wireless SSID matches any specified with --trusted-ssids, tear down the VPN connection and do not reconnect on demand.
  • Else if wireless SSID matches any specified with --untrusted-ssids, unconditionally bring up the VPN connection on the next network attempt.
  • Else if the primary network interface becomes Wifi (any SSID except those above), unconditionally bring up the VPN connection on the next network attempt.
  • Else if the primary network interface becomes Cellular, unconditionally bring up the VPN connection on the next network attempt.
  • Else, leave any existing VPN connection up, but do not reconnect on demand.

For 'medium' security level, the following algorithm is executed upon network changes, in order:

  • If wireless SSID matches any specified with --trusted-ssids, tear down the VPN connection and do not reconnect on demand.
  • Else if wireless SSID matches any specified with --untrusted-ssids, unconditionally bring up the VPN connection on the next network attempt.
  • Else if the primary network interface becomes Wifi (any SSID except those above), leave any existing VPN connection up, but do not reconnect on demand.
  • Else if the primary network interface becomes Cellular, leave any existing VPN connection up, but do not reconnect on demand.
  • Else, leave any existing VPN connection up, but do not reconnect on demand.

URL Probe

Apple provides a URLStringProbe test condition where a VPN connection will only be established, if and only if a specified URL is successfully fetched (returning a 200 HTTP status code) without redirection.

This feature can be enabled for statistical and maintenance-protection reasons. Otherwise, it can also workaround a circular limitation with unsecured wireless captive portals. See Known Issues below for further elaboration.

By enabling this option, you will need to reliably and quickly respond with HTTP status code 200 at the URL string supplied.

Examples

Typical Usage

$ ovpnmcgen.rb gen --trusted-ssids home --host vpn.example.com \
--cafile path/to/ca.pem --tafile path/to/ta.key \
--url-probe http://vpn.example.com/status \
--p12file path/to/john-ipad.p12 --p12pass p12passphrase john ipad

Output:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>PayloadContent</key>
    <array>
        <dict>
            <key>PayloadDescription</key>
            <string>Configures VPN settings, including authentication.</string>
            <key>PayloadDisplayName</key>
            <string>VPN (vpn.example.com/VoD)</string>
            <key>PayloadIdentifier</key>
            <string>com.example.vpn.john-ipad.vpnconfig</string>
            <key>PayloadOrganization</key>
            <string>vpn.example.com</string>
            <key>PayloadType</key>
            <string>com.apple.vpn.managed</string>
            <key>PayloadUUID</key>
            <string>...</string>
            <key>PayloadVersion</key>
            <integer>1</integer>
            <key>UserDefinedName</key>
            <string>vpn.example.com/VoD</string>
            <key>VPN</key>
            <dict>
                <key>AuthenticationMethod</key>
                <string>Certificate</string>
                <key>OnDemandEnabled</key>
                <integer>1</integer>
                <key>OnDemandRules</key>
                <array>
                    <dict>
                        <key>Action</key>
                        <string>Disconnect</string>
                        <key>SSIDMatch</key>
                        <array>
                            <string>home</string>
                        </array>
                        <key>URLStringProbe</key>
                        <string>http://vpn.example.com/status</string>
                    </dict>
                    <dict>
                        <key>Action</key>
                        <string>Connect</string>
                        <key>InterfaceTypeMatch</key>
                        <string>WiFi</string>
                        <key>URLStringProbe</key>
                        <string>http://vpn.example.com/status</string>
                    </dict>
                    <dict>
                        <key>Action</key>
                        <string>Ignore</string>
                        <key>InterfaceTypeMatch</key>
                        <string>Cellular</string>
                        <key>URLStringProbe</key>
                        <string>http://vpn.example.com/status</string>
                    </dict>
                    <dict>
                        <key>Action</key>
                        <string>Connect</string>
                        <key>URLStringProbe</key>
                        <string>http://vpn.example.com/status</string>
                    </dict>
                </array>
                <key>PayloadCertificateUUID</key>
                <string>...</string>
                <key>RemoteAddress</key>
                <string>DEFAULT</string>
            </dict>
            <key>VPNSubType</key>
            <string>net.openvpn.OpenVPN-Connect.vpnplugin</string>
            <key>VPNType</key>
            <string>VPN</string>
            <key>VendorConfig</key>
            <dict>
                <key>ca</key>
                <string>-----BEGIN CERTIFICATE-----\n...\n-----END CERTIFICATE-----</string>
                <key>client</key>
                <string>NOARGS</string>
                <key>comp-lzo</key>
                <string>NOARGS</string>
                <key>dev</key>
                <string>tun</string>
                <key>key-direction</key>
                <string>1</string>
                <key>persist-key</key>
                <string>NOARGS</string>
                <key>persist-tun</key>
                <string>NOARGS</string>
                <key>proto</key>
                <string>udp</string>
                <key>remote</key>
                <string>vpn.example.com 1194 udp</string>
                <key>remote-cert-tls</key>
                <string>server</string>
                <key>resolv-retry</key>
                <string>infinite</string>
                <key>tls-auth</key>
                <string>#\n# 2048 bit OpenVPN static key\n#\n-----BEGIN OpenVPN Static key V1-----\n...\n-----END OpenVPN Static key V1-----</string>
                <key>verb</key>
                <string>3</string>
            </dict>
        </dict>
        <dict>
            <key>Password</key>
            <string>p12passphrase</string>
            <key>PayloadCertificateFileName</key>
            <string>john-ipad.p12</string>
            <key>PayloadContent</key>
            <data>
            base64data
            </data>
            <key>PayloadDescription</key>
            <string>Provides device authentication (certificate or identity).</string>
            <key>PayloadDisplayName</key>
            <string>john-ipad.p12</string>
            <key>PayloadIdentifier</key>
            <string>com.example.vpn.john-ipad.credential</string>
            <key>PayloadOrganization</key>
            <string>vpn.example.com</string>
            <key>PayloadType</key>
            <string>com.apple.security.pkcs12</string>
            <key>PayloadUUID</key>
            <string>...</string>
            <key>PayloadVersion</key>
            <integer>1</integer>
        </dict>
    </array>
    <key>PayloadDescription</key>
    <string>OpenVPN Configuration Payload for john-ipad@vpn.example.com</string>
    <key>PayloadDisplayName</key>
    <string>vpn.example.com OpenVPN iphoting@ipad</string>
    <key>PayloadIdentifier</key>
    <string>com.example.vpn.john-ipad</string>
    <key>PayloadOrganization</key>
    <string>vpn.example.com</string>
    <key>PayloadRemovalDisallowed</key>
    <false/>
    <key>PayloadType</key>
    <string>Configuration</string>
    <key>PayloadUUID</key>
    <string>...</string>
    <key>PayloadVersion</key>
    <integer>1</integer>
</dict>
</plist>

Extended Usage

$ ovpnmcgen.rb gen --trusted-ssids home,school --untrusted-ssids virusnet \
--host vpn.example.com --cafile path/to/ca.pem --tafile path/to/ta.key \
--url-probe http://vpn.example.com/status \
--p12file path/to/john-ipad.p12 --p12pass p12passphrase john ipad

Output similar to above:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>PayloadContent</key>
    <array>
        <dict>
            ...
            <key>VPN</key>
            <dict>
                ...
                <key>OnDemandRules</key>
                <array>
                    <dict>
                        <key>Action</key>
                        <string>Disconnect</string>
                        <key>SSIDMatch</key>
                        <array>
                            <string>home</string>
                            <string>school</string>
                        </array>
                    </dict>
                    <dict>
                        <key>Action</key>
                        <string>Connect</string>
                        <key>SSIDMatch</key>
                        <array>
                            <string>virusnet</string>
                        </array>
                        <key>URLStringProbe</key>
                        <string>http://vpn.example.com/status</string>
                    </dict>
                    <dict>
                        <key>Action</key>
                        <string>Connect</string>
                        <key>InterfaceTypeMatch</key>
                        <string>WiFi</string>
                        <key>URLStringProbe</key>
                        <string>http://vpn.example.com/status</string>
                    </dict>
                    <dict>
                        <key>Action</key>
                        <string>Ignore</string>
                        <key>InterfaceTypeMatch</key>
                        <string>Cellular</string>
                        <key>URLStringProbe</key>
                        <string>http://vpn.example.com/status</string>
                    </dict>
                    <dict>
                        <key>Action</key>
                        <string>Connect</string>
                        <key>URLStringProbe</key>
                        <string>http://vpn.example.com/status</string>
                    </dict>
                </array>
                ...
            </dict>
            ...
        </dict>
        ...
    </array>
    ...
</dict>
</plist>

Using OpenSSL to convert files into PKCS#12 (.p12)

openssl pkcs12 -export -out path/to/john-ipad.p12 \
-inkey path/to/john-ipad.key -in path/to/john-ipad.crt \
-passout pass:p12passphrase -name john-ipad@vpn.example.com

Known Issues

  • "Not connected to Internet" error/behaviour when VPN should be established.

    Diagnosis: Load any site in Safari. An error message "Safari cannot open the page because your iPhone is not connected to the Internet" will be presented.

    There is a bug in the iOS/OS X network routing code that hangs the routing system, preventing the gateway or IP address from being set. This happens more frequently when the tunnel is brought up/down more frequently.

    Solution: Upgrade to iOS 8.1. The new iOS update seems to have mostly solved issues surrounding the networking stack.

    Workaround: Hard-restart iOS. Press and hold down both the home and sleep/wake buttons until iOS turns off and back on with the Apple boot up screen. Release when the Apple boot up screen appears.

  • Weird Rapid Connecting…/Disconnected behaviour.

    Diagnosis: VPN status in Settings.app rapid alternates between Connecting… and Disconnected.

    Usually happens when the VoD component is stuck in an infinite loop. Not sure what triggers it.

    Solution: Upgrade to iOS 8.1. The new iOS update seems to have mostly solved issues surrounding the networking stack.

    Workaround: Hard-restart iOS. Press and hold down both the home and sleep/wake buttons until iOS turns off and back on with the Apple boot up screen. Release when the Apple boot up screen appears.

  • Cannot load Captive Portals (Hotspots on unsecured Wireless networks).

    Some unsecured hotspots require navigating certain webpages before full access to the internet is available. This requirement blocks VPN connections and iOS will also block captive portal access, waiting on the VPN connection. This circular dependency results in no internet access.

    Solution: Implement URLStringProbe where, if and only if this URL is successfully fetched (returning a 200 HTTP status code) without redirection, will the VPN service be required, relied on, and brought up. Enable with the --url-probe flag.

    Workaround: Manually disable VPN-on-Demand in Settings.app > VPN > Server (i) option screen. Reenable only after Internet access is available.

TODO

  • Config file to specify global options, such as --cafile, --tafile, --host, --[un]trusted-ssids.

    See commit #d9c015618 for feature.

  • Batch-operation mode, with CSV-file as input, and a CSV UUID-index file to track generated profiles as output.

    The same UUID should be used for profile updates, so that iOS knows which profile to replace, especially in MDM environments.

    Custom UUID overrides now supported via --{profile,vpn,cert}-uuid.

  • Adopt OpenVPN parameters from an OpenVPN-compatible client.conf input file.

    Implemented, but does not support inline <ca|tls-auth> data enclosures, and command line flags (that are required) override config file values.

  • Sign/Encrypt .mobileconfig.

    Current workaround is to use a trusted MDM solution to securely push these unsigned, unencrypted profiles to iOS devices, through the encrypted MDM connected.

References

Contributing

  1. Fork it (http://github.com/iphoting/ovpnmcgen.rb/fork)
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request