IPSEC.CONF(5)             OpenBSD Programmer's Manual            IPSEC.CONF(5)

NAME
     ipsec.conf - IPsec configuration file

DESCRIPTION
     The ipsec.conf file specifies rules and definitions for IPsec, which pro-
     vides security services for IP datagrams.  IPsec itself is a pair of pro-
     tocols: Encapsulating Security Payload (ESP), which provides integrity
     and confidentiality; and Authentication Header (AH), which provides in-
     tegrity.  The IPsec protocol itself is described in ipsec(4).

     In its most basic form, a flow is established between hosts and/or net-
     works, and then Security Associations (SA) are established, which detail
     how the desired protection will be achieved.  IPsec uses flows to deter-
     mine whether to apply security services to an IP packet or not.

     Generally speaking an automated keying daemon, such as isakmpd(8), is
     used to set up flows and establish SAs, by specifying an `ike' line in
     ipsec.conf (see AUTOMATIC KEYING, below).  An authentication method, such
     as public key authentication, will also have to be set up: see the PKI
     section of isakmpd(8) for information on the types of authentication
     available, and the procedures for setting them up.

     The keying daemon, isakmpd(8), can be enabled to run at boot time via the
     isakmpd_flags variable in rc.conf.local(8).  Note that it will probably
     need to be run with at least the -K option, to avoid keynote(4) policy
     checking.  The ipsec.conf configuration itself is loaded at boot time if
     the variable ipsec is set to YES in rc.conf.local(8).  A utility called
     ipsecctl(8) is also available to load ipsec.conf configurations, and can
     additionally be used to view and modify IPsec flows.

     An alternative method of setting up SAs is also possible using manual
     keying.  Manual keying is not recommended, but can be convenient for
     quick setups and testing.  Those procedures are documented within this
     page.

IPSEC.CONF FILE FORMAT
     Lines beginning with `#' and empty lines are regarded as comments, and
     ignored.  Lines may be split using the `\' character.

     Addresses can be specified in CIDR notation (matching netblocks), as sym-
     bolic host names, interface names, or interface group names.

     Certain parameters can be expressed as lists, in which case ipsecctl(8)
     generates all the necessary combinations.  For example:

           ike esp from {192.168.1.1, 192.168.1.2} to \
                   {10.0.0.17, 10.0.0.18} peer 192.168.10.1

     Will expand to:

           ike esp from 192.168.1.1 to 10.0.0.17 peer 192.168.10.1
           ike esp from 192.168.1.1 to 10.0.0.18 peer 192.168.10.1
           ike esp from 192.168.1.2 to 10.0.0.17 peer 192.168.10.1
           ike esp from 192.168.1.2 to 10.0.0.18 peer 192.168.10.1

     Macros can be defined that will later be expanded in context.  Macro
     names must start with a letter, and may contain letters, digits and un-
     derscores.  Macro names may not be reserved words (for example flow,
     from, esp).  Macros are not expanded inside quotes.

     For example:

           remote_gw = "192.168.3.12"
           flow esp from 192.168.7.0/24 to 192.168.8.0/24 peer $remote_gw

     Additional configuration files can be included with the include keyword,
     for example:

           include "/etc/macros.conf"

AUTOMATIC KEYING
     In this scenario, ipsec.conf is used to set up flows and SAs automatical-
     ly using isakmpd(8).  Some examples of setting up automatic keying:

        # Set up a VPN:
        # First between the gateway machines 192.168.3.1 and 192.168.3.2
        # Second between the networks 10.1.1.0/24 and 10.1.2.0/24
        ike esp from 192.168.3.1 to 192.168.3.2
        ike esp from 10.1.1.0/24 to 10.1.2.0/24 peer 192.168.3.2

     The commands are as follows:

     ike [mode] [encap] [tmode]
           mode specifies the IKE mode to use: one of passive, active, or
           dynamic.  When passive is specified, isakmpd(8) will not immediate-
           ly start negotiation of this tunnel, but wait for an incoming re-
           quest from the remote peer.  When active or dynamic is specified,
           negotiation will be started at once.  The dynamic mode will addi-
           tionally enable Dead Peer Detection (DPD) and use the local host-
           name as the identity of the local peer, if not specified by the
           srcid parameter.  dynamic mode should be used for hosts with dynam-
           ic IP addresses like road warriors or dialup hosts.  If omitted,
           active mode will be used.

           encap specifies the encapsulation protocol to be used.  Possible
           protocols are esp and ah; the default is esp.

           tmode describes the encapsulation mode to be used.  Possible modes
           are tunnel and transport; the default is tunnel.

     proto protocol
           The optional proto parameter restricts the flow to a specific IP
           protocol.  Common protocols are icmp(4), tcp(4), and udp(4).  For a
           list of all the protocol name to number mappings used by
           ipsecctl(8), see the file /etc/protocols.

     from src [port sport] [(srcnat)] to dst [port dport]
           This rule applies for packets with source address src and destina-
           tion address dst.  The keyword any will match any address (i.e.
           0.0.0.0/0).  If the src argument specifies a fictional source ID,
           the srcnat parameter can be used to specify the actual source ad-
           dress.  This can be used in outgoing NAT/BINAT scenarios as de-
           scribed below.  Host addresses are parsed as type ``IPV4_ADDR'';
           adding the suffix /32 will change the type to ``IPV4_ADDR_SUBNET'',
           which can improve interoperability with some IKE implementations.

           The optional port modifiers restrict the flows to the specified
           ports.  They are only valid in conjunction with the tcp(4) and
           udp(4) protocols.  Ports can be specified by number or by name.
           For a list of all port name to number mappings used by ipsecctl(8),
           see the file /etc/services.

     local localip peer remote
           The local parameter specifies the address or FQDN of the local end-
           point.  Unless we are multi-homed or have aliases, this option is
           generally not needed.

           The peer parameter specifies the address or FQDN of the remote end-
           point.  For host-to-host connections where dst is identical to
           remote, this option is generally not needed as it will be set to
           dst automatically.  If it is not specified or if the keyword any is
           given, the default peer is used.

     mode auth algorithm enc algorithm group group
           These parameters define the mode and cryptographic transforms to be
           used for the phase 1 negotiation.  During phase 1 the machines au-
           thenticate and set up an encrypted channel.

           The mode can be either main, which specifies main mode, or
           aggressive, which specifies aggressive mode.  Possible values for
           auth, enc, and group are described below in CRYPTO TRANSFORMS.

           If omitted, ipsecctl(8) will use the default values main, hmac-
           sha1, aes, and modp1024.

     quick auth algorithm enc algorithm group group
           These parameters define the cryptographic transforms to be used for
           the phase 2 negotiation.  During phase 2 the actual IPsec negotia-
           tions happen.

           Possible values for auth, enc, and group are described below in
           CRYPTO TRANSFORMS.  If group is specified, Perfect Forward Security
           (PFS) is used.  If the value none is used, PFS is disabled.

           If omitted, ipsecctl(8) will use the default values hmac-sha2-256
           and aes; PFS will only be used if the remote side requests it.

     srcid string dstid string
           srcid defines an ID of type ``USER_FQDN'' or ``FQDN'' that will be
           used by isakmpd(8) as the identity of the local peer.  If the argu-
           ment is an email address (bob@example.com), ipsecctl(8) will use
           USER_FQDN as the ID type.  Anything else is considered to be an
           FQDN.  If srcid is omitted, the default is to use the IP address of
           the connecting machine.

           dstid is similar to srcid, but instead specifies the ID to be used
           by the remote peer.

     psk string
           Use a pre-shared key string for authentication.  If this option is
           not specified, public key authentication is used (see isakmpd(8)).

     tag string
           Add a pf(4) tag to all packets of phase 2 SAs created for this con-
           nection.  This will allow matching packets for this connection by
           defining rules in pf.conf(5) using the tagged keyword.

           The following variables can be used in tags to include information
           from the remote peer on runtime:

                 $id      The remote phase 1 ID.  It will be expanded to id-
                          type/id-value, e.g. fqdn/foo.bar.org.
                 $domain  Extract the domain from IDs of type FQDN or UFQDN.

           For example, if the ID is fqdn/foo.bar.org or ufqdn/user@bar.org,
           ``ipsec-$domain'' expands to ``ipsec-bar.org''.  The variable ex-
           pansion for the tag directive occurs only at runtime, not during
           configuration file parse time.

PACKET FILTERING
     IPsec traffic appears unencrypted on the enc(4) interface and can be fil-
     tered accordingly using the OpenBSD packet filter, pf(4).  The grammar
     for the packet filter is described in pf.conf(5).

     The following components are relevant to filtering IPsec traffic:

           external interface
           Interface for ISAKMP traffic and encapsulated IPsec traffic.

           proto udp port 500
           ISAKMP traffic on the external interface.

           proto udp port 4500
           ISAKMP NAT-Traversal traffic on the external interface.

           proto ah | esp
           Encapsulated IPsec traffic on the external interface.

           enc0
           Interface for outgoing traffic before it's been encapsulated, and
           incoming traffic after it's been decapsulated.  State on this in-
           terface should be interface bound; see enc(4) for further informa-
           tion.

           proto ipencap
           [tunnel mode only] IP-in-IP traffic flowing between gateways on the
           enc0 interface.

           tagged ipsec-example.org
           Match traffic of phase 2 SAs using the tag keyword.

     If the filtering rules specify to block everything by default, the fol-
     lowing rule would ensure that IPsec traffic never hits the packet filter-
     ing engine, and is therefore passed:

           set skip on enc0

     In the following example, all traffic is blocked by default.  IPsec-re-
     lated traffic from gateways {192.168.3.1, 192.168.3.2} and networks
     {10.0.1.0/24, 10.0.2.0/24} is permitted.

           block on sk0
           block on enc0

           pass  in on sk0 proto udp from 192.168.3.2 to 192.168.3.1 \
                   port {500, 4500}
           pass out on sk0 proto udp from 192.168.3.1 to 192.168.3.2 \
                   port {500, 4500}

           pass  in on sk0 proto esp from 192.168.3.2 to 192.168.3.1
           pass out on sk0 proto esp from 192.168.3.1 to 192.168.3.2

           pass  in on enc0 proto ipencap from 192.168.3.2 to 192.168.3.1 \
                   keep state (if-bound)
           pass out on enc0 proto ipencap from 192.168.3.1 to 192.168.3.2 \
                   keep state (if-bound)
           pass  in on enc0 from 10.0.2.0/24 to 10.0.1.0/24 \
                   keep state (if-bound)
           pass out on enc0 from 10.0.1.0/24 to 10.0.2.0/24 \
                   keep state (if-bound)

     pf(4) has the ability to filter IPsec-related packets based on an arbi-
     trary tag specified within a ruleset.  The tag is used as an internal
     marker which can be used to identify the packets later on.  This could be
     helpful, for example, in scenarios where users are connecting in from
     differing IP addresses, or to support queue-based bandwidth control,
     since the enc0 interface does not support it.

     The following pf.conf(5) fragment uses queues for all IPsec traffic with
     special handling for developers and employees:

           altq on sk0 cbq bandwidth 1000Mb \
                   queue { deflt, developers, employees, ipsec }
               queue deflt bandwidth 10% priority 0 cbq(default ecn)
               queue developers bandwidth 75% priority 7 cbq(borrow red)
               queue employees bandwidth 5% cbq(red)
               queue ipsec bandwidth 10% cbq(red)

           pass out on sk0 proto esp queue ipsec

           pass out on sk0 tagged ipsec-developers.bar.org queue developers
           pass out on sk0 tagged ipsec-employees.bar.org queue employees

     The tags will be assigned by the following ipsec.conf example:

           ike esp from 10.1.1.0/24 to 10.1.2.0/24 peer 192.168.3.2 \
                   tag ipsec-$domain

OUTGOING NETWORK ADDRESS TRANSLATION
     In some network topologies it is desirable to perform NAT on traffic
     leaving through the VPN tunnel.  In order to achieve that, the src argu-
     ment is used to negotiate the desired network ID with the peer and the
     srcnat parameter defines the true local subnet, so that a correct SA can
     be installed on the local side.

     For example, if the local subnet is 192.168.1.0/24 and all the traffic
     for a specific VPN peer should appear as coming from 10.10.10.1, the fol-
     lowing configuration is used:

           ike esp from 10.10.10.1 (192.168.1.0/24) to 192.168.2.0/24 \
                   peer 10.10.20.1

     Naturally, a relevant NAT rule is required in pf.conf(5).  For the exam-
     ple above, this would be:

           match on enc0 from 192.168.1.0/24 to 192.168.2.0/24 nat-to 10.10.10.1

     From the peer's point of view, the local end of the VPN tunnel is de-
     clared to be 10.10.10.1 and all the traffic arrives with that source ad-
     dress.

CRYPTO TRANSFORMS
     It is very important that keys are not guessable.  One practical way of
     generating keys is to use openssl(1).  The following generates a 160-bit
     (20-byte) key:

           $ openssl rand 20 | hexdump -e '20/1 "%02x"'

     The following authentication types are permitted with the auth keyword:

           Authentication      Key Length
           hmac-md5            128 bits
           hmac-ripemd160      160 bits      [phase 2 only]
           hmac-sha1           160 bits
           hmac-sha2-256       256 bits
           hmac-sha2-384       384 bits
           hmac-sha2-512       512 bits

     The following cipher types are permitted with the enc keyword:

           Cipher              Key Length
           des                 56 bits
           3des                168 bits
           aes                 128 bits
           aes-128             128 bits
           aes-192             192 bits
           aes-256             256 bits
           aesctr              160 bits      [phase 2 only]
           blowfish            160 bits
           cast                128 bits
           skipjack            80 bits
           null                (none)        [phase 2 only]

     Use of DES or Skipjack as an encryption algorithm is not recommended (ex-
     cept for backwards compatibility) due to their short key length.  Fur-
     thermore, attacks on Skipjack have shown severe weaknesses in its struc-
     ture.

     DES requires 8 bytes to form a 56-bit key and 3DES requires 24 bytes to
     form its 168-bit key.  This is because the most significant bit of each
     byte is used for parity.

     The keysize of AES-CTR is actually 128-bit.  However as well as the key,
     a 32-bit nonce has to be supplied.  Thus 160 bits of key material have to
     be supplied.

     Using NULL with ESP will only provide authentication.  This is useful in
     setups where AH can not be used, e.g. when NAT is involved.

     The following group types are permitted with the group keyword:

           Group               Size
           modp768             768           [DH group 1]
           modp1024            1024          [DH group 2]
           modp1536            1536          [DH group 5]
           modp2048            2048          [DH group 14]
           modp3072            3072          [DH group 15]
           modp4096            4096          [DH group 16]
           modp6144            6144          [DH group 17]
           modp8192            8192          [DH group 18]
           none                0             [phase 2 only]

MANUAL FLOWS
     In this scenario, ipsec.conf is used to set up flows manually.  IPsec us-
     es flows to determine whether to apply security services to an IP packet
     or not.  Some examples of setting up flows:

        # Set up two flows:
        # First between the machines 192.168.3.14 and 192.168.3.100
        # Second between the networks 192.168.7.0/24 and 192.168.8.0/24
        flow esp from 192.168.3.14 to 192.168.3.100
        flow esp from 192.168.7.0/24 to 192.168.8.0/24 peer 192.168.3.12

     The following types of flow are available:

     flow esp
           ESP can provide the following properties: authentication, integri-
           ty, replay protection, and confidentiality of the data.  If no flow
           type is specified, this is the default.

     flow ah
           AH provides authentication, integrity, and replay protection, but
           not confidentiality.

     flow ipip
           IPIP does not provide authentication, integrity, replay protection,
           or confidentiality.  However, it does allow tunnelling of IP traf-
           fic over IP, without setting up gif(4) interfaces.

     The commands are as follows:

     in or out
           This rule applies to incoming or outgoing packets.  If neither in
           nor out are specified, ipsecctl(8) will assume the direction out
           for this rule and will construct a proper in rule.  Thus packets in
           both directions will be matched.

     proto protocol
           The optional proto parameter restricts the flow to a specific IP
           protocol.  Common protocols are icmp(4), tcp(4), and udp(4).  For a
           list of all the protocol name to number mappings used by
           ipsecctl(8), see the file /etc/protocols.

     from src [port sport] to dst [port dport]
           This rule applies for packets with source address src and destina-
           tion address dst.  The keyword any will match any address (i.e.
           0.0.0.0/0).  The optional port modifiers restrict the flows to the
           specified ports.  They are only valid in conjunction with the
           tcp(4) and udp(4) protocols.  Ports can be specified by number or
           by name.  For a list of all port name to number mappings used by
           ipsecctl(8), see the file /etc/services.

     local localip
           The local parameter specifies the address or FQDN of the local end-
           point of this flow and can be usually left out.

     peer remote
           The peer parameter specifies the address or FQDN of the remote end-
           point of this flow.  For host-to-host connections where dst is
           identical to remote, the peer specification can be left out as it
           will be set to dst automatically.  Only if the keyword any is given
           is a flow without peer created.

     type modifier
           This optional parameter sets up special flows using modifiers.  By
           default, ipsecctl(8) will automatically set up normal flows with
           the corresponding type.  modifier may be one of the following:

                 acquire    Use IPsec and establish SAs dynamically.  Unen-
                            crypted traffic is permitted until it is protected
                            by IPsec.
                 bypass     Matching packets are not processed by IPsec.
                 deny       Matching packets are dropped.
                 dontacq    Use IPsec.  If no SAs are available, does not
                            trigger isakmpd(8).
                 require    Use IPsec and establish SAs dynamically.  Unen-
                            crypted traffic is not permitted until it is pro-
                            tected by IPsec.
                 use        Use IPsec.  Unencrypted traffic is permitted.
                            Does not trigger isakmpd(8).

MANUAL SECURITY ASSOCIATIONS (SAs)
     In this scenario, ipsec.conf is used to set up SAs manually.  The securi-
     ty parameters for a flow are stored in the Security Association Database
     (SADB).  An example of setting up an SA:

        # Set up an IPsec SA for flows between 192.168.3.14 and 192.168.3.12
        esp from 192.168.3.14 to 192.168.3.12 spi 0xdeadbeef:0xbeefdead \
                authkey file "auth14:auth12" enckey file "enc14:enc12"

     Parameters specify the peers, Security Parameter Index (SPI), crypto-
     graphic transforms, and key material to be used.  The following rules en-
     ter SAs in the SADB:

           esp       Enter an ESP SA.
           ah        Enter an AH SA.
           ipip      Enter an IPIP pseudo SA.
           tcpmd5    Enter a TCP MD5 SA.

     The commands are as follows:

     mode  For ESP and AH the encapsulation mode can be specified.  Possible
           modes are tunnel and transport.  When left out, tunnel is chosen.
           For details on modes see ipsec(4).

     from src to dst
           This SA is for a flow between the peers src and dst.

     spi number
           The SPI identifies a specific SA.  number is a 32-bit value and
           needs to be unique.

     auth algorithm
           For ESP and AH an authentication algorithm can be specified.  Pos-
           sible values are described above in CRYPTO TRANSFORMS.

           If no algorithm is specified, ipsecctl(8) will choose hmac-sha2-256
           by default.

     enc algorithm
           For ESP an encryption algorithm can be specified.  Possible values
           are described above in CRYPTO TRANSFORMS.

           If no algorithm is specified, ipsecctl(8) will choose aes by de-
           fault.

     authkey keyspec
           keyspec defines the authentication key to be used.  It is either a
           hexadecimal string or a path to a file containing the key.  The
           filename may be given as either an absolute path to the file or a
           relative pathname, and is specified as follows:

                 authkey file "filename"

     enckey keyspec
           The encryption key is defined similarly to authkey.

     tcpmd5 from src to dst spi number authkey keyspec
           TCP MD5 signatures are generally used between BGP daemons, such as
           bgpd(8).  Since bgpd(8) itself already provides this functionality,
           this option is generally not needed.  More information on TCP MD5
           signatures can be found in tcp(4), bgpd.conf(5), and RFC 2385.

           This rule applies for packets with source address src and destina-
           tion address dst.  The parameter spi is a 32-bit value defining the
           Security Parameter Index (SPI) for this SA.  The encryption key is
           defined similarly to authkey.

     Since an SA is directional, a second SA is normally configured in the re-
     verse direction.  This is done by adding a second, colon-separated, value
     to spi, authkey, and enckey.

SEE ALSO
     openssl(1), enc(4), ipsec(4), tcp(4), pf.conf(5), ipsecctl(8), isakmpd(8)

HISTORY
     The ipsec.conf file format first appeared in OpenBSD 3.8.

OpenBSD 4.7                     January 2, 2010                              8
