path: root/sbin/ipsecctl/ipsec.conf.5

.\"	$OpenBSD: ipsec.conf.5,v 1.74 2006/08/30 16:07:29 jmc Exp $
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.\" Copyright (c) 2004 Mathieu Sauve-Frankel  All rights reserved.
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.Dd April 9, 2005
.Dt IPSEC.CONF 5
.Os
.Sh NAME
.Nm ipsec.conf
.Nd IPsec configuration file
.Sh DESCRIPTION
The
.Nm
file specifies rules and definitions for
.Xr ipsec 4
IP security services.
The rulesets themselves can be loaded, viewed, and modified via the
.Xr ipsecctl 8
userland utility.
.Sh MACROS
Much like
.Xr cpp 1
or
.Xr m4 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 underscores.
Macro names may not be reserved words (for example
.Ic flow ,
.Ic from ,
.Ic esp ) .
Macros are not expanded inside quotes.
.Pp
For example:
.Bd -literal -offset indent
remote_gw = "192.168.3.12"
flow esp from 192.168.7.0/24 to 192.168.8.0/24 peer $remote_gw
.Ed
.Sh AUTOMATIC KEYING
Rules can also specify IPsec flows and SAs to be established automatically by
.Xr isakmpd 8 .
Some examples of setting up automatic keying:
.Bd -literal -offset 3n
# Set up two tunnels:
# First between the 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
.Ed
.Pp
Parameters specify the packets that will go through the tunnel and which
cryptographic transforms are used for
.Xr isakmpd 8 .
Some parameters are optional.
Certain parameters can be expressed as lists, in which case
.Xr ipsecctl 8
generates all needed rule combinations.
.Pp
Addresses can be specified in CIDR notation (matching netblocks),
as symbolic host names, interface names or interface group names.
.Bl -tag -width xxxx
.It Xo
.Ic ike
.Aq Ar mode
.Xc
When
.Ar passive
is specified,
.Xr isakmpd 8
will not immediately start negotiation of this tunnel, but wait for an incoming
request from the remote peer.
When
.Ar active
or
.Ar dynamic
is specified, negotiation will be started at once.
The
.Ar dynamic
mode will additionally enable Dead Peer Detection (DPD) and use the
local hostname as the identity of the local peer, if not specified by
the
.Ar srcid
parameter.
.Ar dynamic
mode should be used for hosts with dynamic IP addresses like road
warriors or dialup hosts.
If omitted,
.Ar active
mode will be used.
.Pp
See
.Xr isakmpd 8
for details on ISAKMP/IKE.
.It Xo
.Aq Ar encap
.Xc
The encapsulation protocol to be used.
Possible protocols are
.Ar esp
and
.Ar ah .
The default is
.Ar esp .
For details on ESP and AH see
.Xr ipsec 4 .
.It Xo
.Aq Ar tmode
.Xc
The encapsulation mode to be used can be specified.
Possible modes are
.Ar tunnel
and
.Ar transport .
When left out,
.Ar tunnel
is chosen.
For details on modes see
.Xr ipsec 4 .
.It Ic proto Aq Ar protocol
The optional
.Ic proto
parameter restricts the flow to a specific IP protocol.
Common protocols are
.Xr icmp 4 ,
.Xr tcp 4 ,
and
.Xr udp 4 .
For a list of all the protocol name to number mappings used by
.Xr ipsecctl 8 ,
see the file
.Pa /etc/protocols .
.It Xo
.Ic from
.Aq Ar src
.Ic port
.Aq Ar sport
.Ic to
.Aq Ar dst
.Ic port
.Aq Ar dport
.Xc
This rule applies for packets with source address
.Aq Ar src
and destination address
.Aq Ar dst .
The keyword
.Ar any
will match any address (i.e. 0.0.0.0/0).
The optional
.Ic port
modifiers restrict the flows to the specified ports.
They are only valid in conjunction with the
.Xr tcp 4
and
.Xr udp 4
protocols.
Ports can be specified by number or by name.
For a list of all port name to number mappings used by
.Xr ipsecctl 8 ,
see the file
.Pa /etc/services .
.It Ic local Aq Ar localip
The
.Ic local
parameter specifies the local address to be used, if we are multi-homed
or have aliases.
Usually this parameter can be left out.
.It Ic peer Aq Ar remote
The
.Ic peer
parameter specifies the address or FQDN of the remote endpoint of this
particular flow.
For host-to-host connections where
.Aq Ar dst
is identical to
.Aq Ar remote ,
the
.Ic peer
specification can be left out.
.It Xo
.Ic main auth
.Aq Ar algorithm
.Ic enc
.Aq Ar algorithm
.Ic group
.Aq Ar group
.Xc
These parameters define the cryptographic transforms to be used for main mode.
Possible values for
.Ic auth
are
.Ar hmac-md5 ,
.Ar hmac-sha1 ,
.Ar hmac-sha2-256 ,
.Ar hmac-sha2-384 ,
and
.Ar hmac-sha2-512 .
For
.Ic enc
the values
.Ar des ,
.Ar 3des ,
.Ar aes ,
.Ar blowfish ,
and
.Ar cast
are allowed.
For
.Ic group
the values
.Ar modp768 ,
.Ar modp1024 ,
.Ar modp1536 ,
.Ar modp2048 ,
.Ar modp3072 ,
.Ar modp4096 ,
.Ar modp6144 ,
and
.Ar modp8192
are allowed.
If omitted,
.Xr ipsecctl 8
will use the default values
.Ar hmac-sha1 ,
.Ar aes ,
and group
.Ar modp1024 .
.It Xo
.Ic quick auth
.Aq Ar algorithm
.Ic enc
.Aq Ar algorithm
.Ic group
.Aq Ar group
.Xc
Similar to
.Ic main ,
.Ic quick
defines the transforms to be used for quick mode.
However, the possible values for
.Ic auth
are
.Ar hmac-md5 ,
.Ar hmac-sha1 ,
.Ar hmac-ripemd160 ,
.Ar hmac-sha2-256 ,
.Ar hmac-sha2-384 ,
and
.Ar hmac-sha2-512 .
For
.Ic enc
valid values are
.Ar des ,
.Ar 3des ,
.Ar aes ,
.Ar aesctr ,
.Ar blowfish ,
and
.Ar cast .
For
.Ic group
the values
.Ar modp768 ,
.Ar modp1024 ,
.Ar modp1536 ,
.Ar modp2048 ,
.Ar modp3072 ,
.Ar modp4096 ,
.Ar modp6144 ,
.Ar modp8192 ,
and
.Ar none
are allowed.
When a group is specified perfect forward security (PFS) will be used.
When the value
.Ar none
is used, PFS will be disabled.
If no quick mode transforms are specified,
the default values
.Ar hmac-sha2-256
and
.Ar aes
are used;
PFS will only be used if the remote side requests it.
.It Xo
.Ic srcid
.Aq Ar fqdn
.Xc
This optional parameter defines either a UFQDN or an FQDN that will be used by
.Xr isakmpd 8
as the identity of the local peer.
If the argument is an email address (bob@example.com), ipsecctl will use UFQDN as the ID type.
Anything else is considered to be an FQDN.
.It Xo
.Ic dstid
.Aq Ar fqdn
.Xc
Similar to
.Ic srcid ,
this optional parameter defines a FQDN to be used by the remote peer.
.It Ic psk Aq Ar string
Use a pre-shared key
.Ar string
for authentication.
If not specified, RSA authentication will be used.
By default, the system startup script
.Xr rc 8
generates a key-pair for
.Xr isakmpd 8
when starting, if one does not already exist.
.El
.Sh MANUAL FLOWS
IPsec uses
.Em flows
to determine whether to apply security services to an IP packet or not.
Some examples of setting up flows:
.Bd -literal -offset 3n
# 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
.Ed
.Pp
The following security services are available:
.Bl -tag -width xxxx
.It Ic flow esp
ESP can provide the following properties:
authentication, integrity, replay protection, and confidentiality of the data.
.It Ic flow ah
AH provides authentication, integrity, and replay protection, but no
confidentiality.
.It Ic flow ipip
IPIP provides neither authentication, integrity, replay protection, nor
confidentiality.
However, it allows you to tunnel IP traffic over IP, without setting up
.Xr gif 4
interfaces.
.El
.Pp
For details on ESP and AH see
.Xr ipsec 4 .
When no service is specified,
.Xr ipsecctl 8
will use ESP.
The settings for the security services have to be negotiated by
.Xr isakmpd 8 .
As soon as a packet matches a flow,
.Xr isakmpd 8
automatically starts the negotiation.
See
.Xr isakmpd 8
for details.
.Pp
Parameters specify the packets to which a flow applies.
Some parameters are optional.
Certain parameters can be expressed as lists, in which case
.Xr ipsecctl 8
generates all needed rule combinations.
.Pp
Addresses can be specified in CIDR notation (matching netblocks),
as symbolic host names, interface names or interface group names.
.Bl -tag -width xxxx
.It Ic in No or Ic out
This rule applies to incoming or outgoing packets.
If neither
.Ic in
nor
.Ic out
are specified,
.Xr ipsecctl 8
will assume the direction
.Ic out
for this rule and will construct a proper
.Ic in
rule.
Thus packets in both directions will be matched.
.It Ic proto Aq Ar protocol
The optional
.Ic proto
parameter restricts the flow to a specific IP protocol.
Common protocols are
.Xr icmp 4 ,
.Xr tcp 4 ,
and
.Xr udp 4 .
For a list of all the protocol name to number mappings used by
.Xr ipsecctl 8 ,
see the file
.Pa /etc/protocols .
.It Xo
.Ic from
.Aq Ar src
.Ic port
.Aq Ar sport
.Ic to
.Aq Ar dst
.Ic port
.Aq Ar dport
.Xc
This rule applies for packets with source address
.Aq Ar src
and destination address
.Aq Ar dst .
The keyword
.Ar any
will match any address (i.e. 0.0.0.0/0).
The optional
.Ic port
modifiers restrict the flows to the specified ports.
They are only valid in conjunction with the
.Xr tcp 4
and
.Xr udp 4
protocols.
Ports can be specified by number or by name.
For a list of all port name to number mappings used by
.Xr ipsecctl 8 ,
see the file
.Pa /etc/services .
.It Ic local Aq Ar localip
The
.Ic local
parameter specifies the address or FQDN of the local endpoint of this
flow and can be usually left out.
.It Ic peer Aq Ar remote
The
.Ic peer
parameter specifies the address or FQDN of the remote endpoint of this
flow.
For host-to-host connections where
.Aq Ar dst
is identical to
.Aq Ar remote ,
the
.Ic peer
specification can be left out.
.It Ic type Aq Ar modifier
This optional parameter sets up special flows using the modifiers
.Ar require ,
.Ar use ,
.Ar acquire ,
.Ar dontacq ,
.Ar bypass
or
.Ar deny .
A bypass flow is used to specify a flow for which security processing
will be bypassed: matching packets will not be processed by any other
flows and handled in normal operation.
A deny flow is used to drop any matching packets.
By default,
.Xr ipsecctl 8
will automatically set up normal flows with the corresponding type.
.El
.Sh SECURITY ASSOCIATIONS (SAs)
The security parameters for a
.Ar flow
are stored in the Security Association Database
(SADB).
Some examples of setting up SAs:
.Bd -literal -offset 3n
# Set up IPsec SAs 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 \e
	auth hmac-sha2-256 enc aesctr authkey file "auth14:auth12" \e
	enckey file "enc14:enc12"
.Ed
.Pp
The following rules enter SAs in the SADB:
.Pp
.Bl -tag -width Ds -offset indent -compact
.It Ic esp
Enter an ESP SA.
.It Ic ah
Enter an AH SA.
.\".It Ic ipcomp
.\"Enter an IPCOMP SA.
.It Ic ipip
Enter an IPIP pseudo SA.
.It Ic tcpmd5
Enter a TCP MD5 SA.
.El
.Pp
Parameters specify the peers, Security Parameter Index (SPI),
cryptographic transforms, and key material to be used.
Certain parameters can be expressed as lists, in which case
.Xr ipsecctl 8
generates all needed rule combinations.
.Pp
Addresses can be specified in CIDR notation (matching netblocks),
as symbolic host names, interface names or interface group names.
.Bl -tag -width xxxx
.It Xo
.Aq Ar mode
.Xc
For
.Ic esp
and
.Ic ah ,
.\".Ic ipcomp
the encapsulation mode to be used can be specified.
Possible modes are
.Ar tunnel
and
.Ar transport .
When left out,
.Ar tunnel
is chosen.
For details on modes see
.Xr ipsec 4 .
.It Xo
.Ic from
.Aq Ar src
.Ic to
.Aq Ar dst
.Xc
This SA is for a
.Ar flow
between the peers
.Aq Ar src
and
.Aq Ar dst .
.It Xo
.Ic spi
.Aq Ar number
.Xc
The SPI identifies a specific SA.
.Ar number
is a 32-bit value and needs to be unique.
.It Xo
.Ic auth
.Aq Ar algorithm
.Xc
For both
.Ic esp
and
.Ic ah
an authentication algorithm can be specified.
Possible algorithms are
.Ar hmac-md5 ,
.Ar hmac-ripemd160 ,
.Ar hmac-sha1 ,
.Ar hmac-sha2-256 ,
.Ar hmac-sha2-384 ,
and
.Ar hmac-sha2-512 .
.Pp
If no algorithm is specified,
.Xr ipsecctl 8
will choose
.Ar hmac-sha2-256
by default.
.\".It Xo
.\".Ic comp
.\".Aq Ar algorithm
.\".Xc
.\"The compression algorithm to be used.
.\"Possible algorithms are
.\".Ar deflate
.\"and
.\".Ar lzs .
.\"Note that
.\".Ar lzs
.\"is only available with
.\".Xr hifn 4
.\"because of the patent held by Hifn, Inc.
.It Xo
.Ic enc
.Aq Ar algorithm
.Xc
For
.Ic esp
an encryption algorithm needs to be specified.
Possible algorithms are
.Ar 3des-cbc ,
.Ar des-cbc ,
.Ar aes ,
.Ar aesctr ,
.Ar blowfish ,
.Ar cast128 ,
.Ar null ,
and
.Ar skipjack .
.Pp
If no algorithm is specified,
.Xr ipsecctl 8
will choose
.Ar aes
by default.
.It Xo
.Ic authkey
.Aq Ar keyspec
.Xc
.Ar 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:
.Bd -literal -offset -indent
authkey file "filename"
.Ed
.Pp
It is also possible to specify two values separated by a colon.
.Xr ipsecctl 8
will then generate the matching incoming SA using the second value specified.
.It Xo
.Ic enckey
.Aq Ar keyspec
.Xc
The encryption key is defined similarly to
.Ic authkey .
.It Xo
.Ic tcpmd5
.Ic from
.Aq Ar src
.Ic to
.Aq Ar dst
.Ic spi
.Aq Ar number
.Ic authkey
.Aq Ar keyspec
.Xc
.Pp
This rule applies for packets with source address
.Aq Ar src
and destination address
.Aq Ar dst .
The parameter
.Ic spi
is a 32-bit value defining the Security Parameter Index (SPI) for this SA.
The encryption key is defined similarly to
.Ic authkey .
.Pp
For details on how to enable TCP MD5 signatures see
.Xr tcp 4 .
The mechanism of protecting
.Xr tcp 4
sessions using MD5 is described in RFC 2385.
.El
.Sh CRYPTO KEY SIZE
Different cipher types may require different sized keys:
.Pp
.Bl -column "CipherXX" "Key Length" -offset indent -compact
.It Em Cipher	Key Length
.It Li DES Ta "56 bits"
.It Li 3DES Ta "168 bits"
.It Li AES Ta "variable (128 bits recommended)"
.It Li Blowfish Ta "variable (160 bits recommended)"
.It Li CAST Ta "variable (128 bits maximum and recommended)"
.It Li Skipjack Ta "80 bits"
.El
.Pp
Use of DES or Skipjack as an encryption algorithm is not recommended
(except for backwards compatibility) due to their short key length.
Furthermore, attacks on Skipjack have shown severe weaknesses
in its structure.
.Pp
Note that 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.
.Pp
Different authentication types may also require different sized keys:
.Pp
.Bl -column "authenticationXX" "Key Length" -offset indent -compact
.It Em Authentication	Key Length
.It Li HMAC-MD5 Ta "128 bits"
.It Li HMAC-RIPEMD160 Ta "160 bits"
.It Li HMAC-SHA1 Ta "160 bits"
.It Li HMAC-SHA2-256 Ta "256 bits"
.It Li HMAC-SHA2-384 Ta "384 bits"
.It Li HMAC-SHA2-512 Ta "512 bits"
.El
.Pp
It is very important that keys are not guessable.
One practical way of generating keys is to use
.Xr openssl 1 .
The following generates a 160-bit (20-byte) key:
.Bd -literal -offset indent
$ openssl rand 20 | hexdump -e '20/1 "%02x"'
.Ed
.Sh SEE ALSO
.Xr openssl 1 ,
.\".Xr ipcomp 4 ,
.Xr ipsec 4 ,
.Xr tcp 4 ,
.Xr isakmpd.conf 5 ,
.Xr ipsecctl 8 ,
.Xr isakmpd 8
.Sh HISTORY
The
.Nm
file format first appeared in
.Ox 3.8 .