vpncloud(1) =========== == Name vpncloud - Peer-to-peer VPN == SYNOPSIS *vpncloud [options] [--config ] [-p ] [-l ] [-c ...]* == OPTIONS *--config *:: Read configuration options from the specified file. Please see the section *CONFIG FILES* for documentation on the file format. If the same option is defined in the config file and as a parameter, the parameter overrides the config file. *-t *, *--type *:: Set the type of network. There are two options: *tap* devices process Ethernet frames *tun* devices process IP packets. [default: *tun*] *-d *, *--device *:: Name of the virtual device. Any *%d* will be filled with a free number. [default: *vpncloud%d*] *--device-path *:: The path of the base device inode, e.g. /dev/net/tun. *--fix-rp-filter*:: If this option is set, VpnCloud will change the rp_filter settings to protect against a potential system vulnerability. See *SECURITY* for more info. *-m *, *--mode *:: The mode of the VPN. The VPN can like a router, a switch or a hub. A *hub* will send all data always to all peers. A *switch* will learn addresses from incoming data and only send data to all peers when the address is unknown. A *router* will send data according to known subnets of the peers and ignore them otherwise. The *normal* mode is switch for tap devices and router for tun devices. [default: *normal*] *-l *, *--listen *:: The address on which to listen for data. This can be simply a port number or a full address in form IP:PORT. If the IP is specified as \'\*' or only a port number is given, then the socket will listen on all IPs (v4 and v6), otherwise the socket will only listen on the given IP. [default: **3210**] *-c *, *--peer *, *--connect *:: Address of a peer to connect to. The address should be in the form *addr:port*. If the node is not started, the connection will be retried periodically. This parameter can be repeated to connect to multiple peers. *--claim *:: The local subnets to claim. This parameter should be in the form *address/prefixlen* where address is an IPv4 address, an IPv6 address, or a MAC address. The prefix length is the number of significant front bits that distinguish the subnet from other subnets. Example: *10.1.1.0/24*. *--no-auto-claim*:: Do not automatically claim the IP set on the virtual interface (on TUN devices). *-p *, *--password *:: A password to encrypt the VPN data. This parameter must be set unless a password is given in a config file or a private key is set. See *SECURITY* for more info. *--key *, *--private-key *:: A private key to use for encryption. The key must be given as base62 as generated by *--genkey*. See *SECURITY* for more info. *--public-key *:: A public key matching the given private key. The key must be given as base62 as generated by *--genkey*. This argument is purely optional. See *SECURITY* for more info. *--trust *, **--trusted-key *:: A public key to trust. Any peer must have a key pair that is trusted by this node, otherwise it will be rejected. The key must be given as base62 as generated by *--genkey*. This argument can be given multiple times. If it is not set, only the own public key will be trusted. See *SECURITY* for more info. *--genkey*:: Generate and print a random key pair and exit. The key pair is printed as base62 and can be used as private-key, public-key and trusted-key options. *--algo *, *--algorithm *:: Supported encryption algorithms ("plain", "aes128", "aes256", or "chacha20"). Nodes exchange the supported algorithms and select the one that is fastest on both ends. This parameter can be given multiple times to enable multiple algorithms. *Warning:* "plain" means unencrypted and needs to be enabled explicitly. As default, all algorithms except "plain" are enabled. *--peer-timeout *:: Peer timeout in seconds. The peers will exchange information periodically and drop peers that are silent for this period of time. [default: *300*] *--keepalive *:: Interval of peer exchange messages in seconds. The peers will exchange information periodically to keep connections alive. This setting overrides how often this will happen. [default: *peer-timeout/2-60*] *--switch-timeout *:: Switch table entry timeout in seconds. This parameter is only used in switch mode. Addresses that have not been seen for the given period of time will be forgotten. [default: *300*] *--beacon-store *:: Periodically store beacons containing the address of this node in the given file or via the given command. If the parameter value starts with a pipe character (*|*), the rest of the value is interpreted as a shell command. Otherwise the value is interpreted as a file to write the beacon to. If this parameter is not given, beacon storage is disabled. Please see the section *BEACONS* for more information. *--beacon-load *:: Periodically load beacons containing the addresses of other nodes from the given file or via the given command. If the parameter value starts with a pipe character (*|*), the rest of the value is interpreted as a shell command. Otherwise the value is interpreted as a file to read the beacon from. If this parameter is not given, beacon loading is disabled. Please see the section *BEACONS* for more information. *--beacon-interval *:: Beacon storage/loading interval in seconds. If configured to do so via *--beacon-store* and *--beacon-load*, the node will periodically store its beacon and load beacons of other nodes. This parameter defines the interval in seconds. [default: *3600*] *--beacon-password *:: An optional password to use to encrypt all beacon data. See the section *BEACONS* for more information. *--ip
*:: An IP address (plus optional prefix length) for the interface. If this argument is given, the address (and if a prefix length is given, also the netmask) is configured on the device and the device is activated. If also *--ifup* is given, the interface is configured before the ifup command is executed. Please see *DEVICE SETUP* for more info. *--ifup *:: A command to setup the network interface. The command will be run (as parameter to *sh -c*) when the device has been created to configure it. The name of the allocated device will be available via the environment variable *IFNAME*. Please note that this command is executed with the full permissions of the caller. Please see *DEVICE SETUP* for more info. *--ifdown *:: A command to bring down the network interface. The command will be run (as parameter to *sh -c*) to remove any configuration from the device. The name of the allocated device will be available via the environment variable *IFNAME*. Please note that this command is executed with the (limited) permissions of the user and group given as *--user* and *--group*. *--pid-file *:: Store the process id in this file when running in the background. If set, the given file will be created containing the process id of the new background process. This option is only used when running in background. *--user *:: *--group *:: Change the user and/or group of the process once all the setup has been done. *--log-file *:: If set, print logs also to the given file. The file will be created and truncated if is exists. *--stats-file *:: If set, periodically write statistics on peers and current traffic to the given file. The file will be periodically overwritten with new data. *--statsd-server *:: If set, periodically send statistics on current traffic and some important events to the given statsd server (host:port). *--statsd-prefix *:: Sets the prefix to use for all statsd entries. [default: **vpncloud**] *--daemon*:: Spawn a background process instead of running the process in the foreground. If this flag is set, the process will first carry out all the initialization, then drop permissions if *--user* or *--group* is used and then spawn a background process and write its process id to a file if *--pid-file* is set. Then, the main process will exit and the background process continues to provide the VPN. At the time, when the main process exits, the interface exists and is properly configured to be used. *--no-port-forwarding*:: Disable automatic port forward. If this option is not set, VpnCloud tries to detect a NAT router and automatically add a port forwarding to it. *-v*, *--verbose*:: Print debug information, including information for data being received and sent. *-q*, *--quiet*:: Only print errors and warnings. *-h*, *--help*:: Display the help. == DESCRIPTION *VpnCloud* is a peer-to-peer VPN over UDP. It creates a virtual network interface on the host and forwards all received data via UDP to the destination. It can work in 3 different modes: *Switch mode*:: In this mode, the VPN will dynamically learn addresses as they are used as source addresses by peers and use them to forward data to its destination. Addresses that have not been seen for some time (option *switch_timeout*) will be forgotten. Data for unknown addresses will be broadcast to all peers. This mode is the default mode for TAP devices that process Ethernet frames but it can also be used with TUN devices and IP packets. *Hub mode*:: In this mode, all data will always be broadcast to all peers. This mode uses lots of bandwidth and should only be used in special cases. *Router mode*:: In this mode, data will be forwarded based on preconfigured address ranges ("claims"). Data for unclaimed addresses will be silently ignored. This mode is the default mode for TUN devices that work with IP packets but it can also be used with TAP devices and Ethernet frames. All connected VpnCloud nodes will form a peer-to-peer network and cross-connect automatically until the network is fully connected. The nodes will periodically exchange information with the other nodes to signal that they are still active and to allow the automatic cross-connect behavior. There are some important things to note: . The cross-connect behavior can be able to connect nodes that are behind firewalls or NATs as it can function as hole-punching. . The management traffic will increase with the peer number quadratically. It should still be reasonably small for high node numbers (below 10 KiB/s for 10.000 nodes). A longer *peer_timeout* can be used to reduce the traffic further. For high node numbers, router mode should be used as it never broadcasts data. VpnCloud does not implement any loop-avoidance. Since data received on the UDP socket will only be sent to the local network interface and vice versa, VpnCloud cannot produce loops on its own. On a TAP device, however STP data can be transported to avoid loops caused by other network components. For TAP devices, IEEE 802.1q frames (VLAN tagged) are detected and forwarded based on separate MAC tables. Any nested tags (Q-in-Q) will be ignored. == EXAMPLES === Simple multi-node connectivity In the example scenario, a simple layer-3 network tunnel is established. Most likely those commands need to be run as *root* using *sudo*. First, VpnCloud need to be started on both nodes (the address after *-c* is the address of the remote node and the the *X* in the interface address must be unique among all nodes, e.g. 0, 1, 2, ...): ---- vpncloud -c REMOTE_HOST:PORT --ip 10.0.0.X/24 --password PASSWORD ---- Afterwards, the interface can be used to communicate. === Routed TUN example In this example, 2 nodes and their subnets should communicate using IP. First, VpnCloud need to be started on both nodes: ---- vpncloud -t tun -c REMOTE_HOST:PORT --ip 10.0.X.1 --claim 10.0.X.0/24 --password PASSWORD ---- It is important to configure the interface in a way that all addresses on the VPN can be reached directly. E.g. if subnets 10.0.1.0/24, 10.0.2.0/24 and so on are used, the interface needs to be configured as 10.0.1.1/16. For TUN devices, this means that the prefix length of the subnets (/24 in this example) must be different than the prefix length that the interface is configured with (/16 in this example). === Important notes . VpnCloud can be used to connect two separate networks. TAP networks can be bridged using *brctl* and TUN networks must be routed. It is very important to be careful when setting up such a scenario in order to avoid network loops, security issues, DHCP issues and many more problems. . TAP devices will forward DHCP data. If done intentionally, this can be used to assign unique addresses to all participants. If this happens accidentally, it can conflict with DHCP servers of the local network and can have severe side effects. == CONFIG FILES The config file is a YAML file that contains configuration values. All entries are optional and override the defaults. Please see the section *OPTIONS* for detailed descriptions of the options. *device*:: A key-value map with device settings *type*:: Set the type of network. Same as *--type* *name*:: Name of the virtual device. Same as *--device* *path*:: Set the path of the base device. Same as *--device-path* *fix-rp-filter*:: Fix the rp_filter settings on the host. Same as *--fix-rp-filter* *ip*:: An IP address (plus optional prefix length) for the interface. Same as *--ip* *ifup*:: A command to setup the network interface. Same as *--ifup* *ifdown*:: A command to bring down the network interface. Same as *--ifdown* *crypto*:: A key-value map with crypto settings *algorithms*:: The encryption algorithms to support. See *--algorithm* *password*:: The password to use for encryption. Same as *--password* *private-key*:: The private key to use. Same as *--private-key* *public-key*:: The public key to use. Same as *--public-key* *trusted-keys*:: Other public keys to trust. See *--trusted-key* *listen*:: The address on which to listen for data. Same as *--listen* *peers*:: A list of addresses to connect to. See *--connect* *peer_timeout*:: Peer timeout in seconds. Same as *--peer-timeout* *keepalive*:: Periodically send message to keep connections alive. Same as *--keepalive* *beacon*:: A key-value map with beacon settings *store*:: Path or command to store beacons. Same as *--beacon-store* *load*:: Path or command to load beacons. Same as *--beacon-load* *interval*:: Interval for loading and storing beacons in seconds. Same as *--beacon-interval* *password*:: Password to encrypt the beacon with. Same as *--beacon-password* *mode*:: The mode of the VPN. Same as *--mode* *switch_timeout*:: Switch table entry timeout in seconds. Same as *--switch-timeout* *claims*:: A list of local subnets to claim. See *--claim* *auto-claim*:: Whether to automatically claim the device ip. See *--no-auto-claim* *port_forwarding*:: Whether to activate port forwardig. See *--no-port-forwarding* *user*:: The name of a user to run the background process under. Same as *--user* *group*:: The name of a group to run the background process under. Same as *--group* *pid_file*:: The path of the pid file to create. Same as *--pid-file* *stats_file*:: The path of the statistics file. Same as *--stats-file* *statsd*:: A key-value map with statsd settings *server*:: Server to report statistics to. Same as *--statsd-server* *prefix*:: Prefix to use when reporting to statsd. Same as *--statsd-prefix* === Example device: type: tun name: vpncloud%d ip: 10.0.1.1/16 crypto: password: mysecret listen: 3210 peers: - remote.machine.foo:3210 - remote.machine.bar:3210 peer_timeout: 600 mode: normal claims: - 10.0.1.0/24 port_forwarding: true user: nobody group: nogroup pid_file: /run/vpncloud.pid == SECURITY VpnCloud uses strong cryptography based on modern cryptographic primitives. Before exchanging any payload data with peers a secure connection is initialized based on key pairs. Each node has a key pair consisting of a private and a public key (*--private-key* and *--public-key*). Those key pairs can be generated via *--genkey*. To allow connections, nodes need to list the public keys of all other nodes as trusted keys (*--trusted-key*). To simplify the key exchange, key pairs can be derived from passwords (*--password*). If no trusted keys are configured, nodes will only trust their own public key. Nodes configured with the same password will therefore trust each others. In the initialization phase of the connection, nodes agree on a temporary key that is used to encrypt the next messages using a fast encryption algorithm. VpnCloud automatically benchmarks all supported algorithms and negotiates to use the fastest algorithm for each connection. Users can limit the supported algorithms if they wish using *--algorithm*. Although highly discouraged, users can opt out of encryption altogether by enabling the *plain* algorithm. (Note: both nodes in a connection must support this, otherwise encryption will take place.) The temporary encryption keys are rotated periodically so they are never used for a longer time. Please refer to the security whitepaper for more details. === CVE-2019-14899 The Linux kernel contains a vulnerability that affects all VPNs disregarding of the specific technology being used. Under some circumstances, the kernel accepts packets for the address range configured on the vpn interface also on other interfaces. This way, an attacker can test the presence of a VPN and find out the IPs being used. Also the attacker can with some effort inject data and manipulate connections that should be protected by the VPN. To mitigate this, the rp_filter setting should be configured to strict mode, which unfortunately a lot of distributions do not set as default. VpnCloud will detect this misconfiguration and offers to fix it via *--fix-rp-filter*. Note: This vulnerability affects all VPN technologies as it is not located in the VPN software but in the Linux kernel. == BEACONS Beacons are short character sequences that contain a timestamp and a list of addresses. They can be published and retrieved by other nodes to find peers without the need for static addresses. The beacons are short (less than 100 characters), encrypted and encoded with printable characters to allow publishing them in various places on the internet, e.g.: * On shared drives or synchronized folders (e.g. on Dropbox) * Via a dedicated database * Via a general purpose message board of message service (e.g. Twitter) The beacons are very robust. They only consist of alphanumeric characters and can be interleaved with non-alphanumeric characters (e.g. whitespace). Also the beacons contain a prefix and suffix that depends on the configured network magic and secret key (if set) so that all nodes can find beacons in a long text. When beacons are stored or loaded via a command (using the pipe character *|*), the command is interpreted using the configured shell *sh*. This command has access to the following environment variables: *$begin*:: The prefix of the beacon. *$end*:: The suffix of the beacon. *$data* (only on store):: The middle part of the beacon. Do not use this without prefix and suffix! *$beacon* (only on store):: The full beacon consisting of prefix, data and suffix. The commands are called in separate threads, so even longer running commands will not block the node. == STATSD SUPPORT When a statsd server is configured (either via **--statsd-server** or the config option **statsd_server**), VpnCloud sends out the following statistics every minute. Gauge values: *peer_count*:: Current number of peers *table_entries*:: Number of routing table / switch table entries The following statistics consist of two keys: *.bytes* and *.packets* that hold the values in bytes and packets. All values refer to the traffic during the last minute: *traffic.protocol.inbound*:: Complete incoming traffic with all peers *traffic.protocol.outbound*:: Complete outgoing traffic with all peers *traffic.payload.inbound*:: Incoming payload traffic with all peers *traffic.payload.outbound*:: Outgoing payload traffic with all peers *invalid_protocol_traffic*:: Invalid incoming protocol traffic *dropped_payload*:: Outgoing traffic that could not be routed All keys are prefixed by a common prefix. The prefix defaults to *vpncloud* but can be changed via **--statsd-prefix** or the config option **statsd_prefix**. == DEVICE SETUP The device is setup using the following steps: . The device is created with the type and name given as *--type* and *--device*. . Depending on the device type and the main network device of the systme, the optimal MTU is determined and configured on the device. . If and IP address (and optional prefix length) is given via *--ip*, the interface is configured with the address and the given netmask (default: 255.255.255.0). Also the interface is set to be active. . If a command is given as *--ifup*, the given command will be executed. The name of the interface is stored in an environment variable as "IFNAME". Note that VpnCloud waits for the command to exit before starting its normal operation. Note that most of the steps will need elevated permissions, so the vpncloud command needs to be executed as root (e.g. via sudo). Beware that the ifup command will also be executed using those permissions. VpnCloud can drop the elevated permissions when *--user* and *--group* is given. == COPYRIGHT Copyright (C) 2015-2020 Dennis Schwerdel This software is licensed under GPL-3 or newer (see LICENSE.md)