IPSECADM(8) OpenBSD System Manager's Manual IPSECADM(8)
ipsecadm - interface to set up IPsec
ipsecadm [command] modifiers ...
To use ipsecadm, IPsec must be enabled by having one or more of the fol-
lowing sysctl(3) variables set:
net.inet.esp.enable Enable the ESP IPsec protocol
net.inet.ah.enable Enable the AH IPsec protocol
net.inet.ipcomp.enable Enable the IPComp protocol
Both the ESP and AH protocols are enabled by default. To keep local mod-
ifications of these variables across reboots, see sysctl.conf(5).
The ipsecadm utility sets up security associations in the kernel to be
used with ipsec(4). It can be used to specify the encryption and authen-
tication algorithms and key material for the network layer security pro-
vided by IPsec. The possible commands are:
new esp Set up a Security Association (SA) which uses the new esp trans-
forms. A SA consists of the destination address, a Security Pa-
rameter Index (SPI) and a security protocol. Encryption and au-
thentication algorithms can be applied. This is the default
mode. Allowed modifiers are: -dst, -src, -proxy, -spi, -enc,
-srcid_type, -srcid, -dstid_type, -dstid, -auth, -authkey,
-authkeyfile, -forcetunnel, -udpencap, -key, and -keyfile.
old esp Set up an SA which uses the old esp transforms. Only encryption
algorithms can be applied. Allowed modifiers are: -dst, -src,
-proxy, -spi, -enc, -srcid_type, -srcid, -dstid_type, -dstid,
-halfiv, -forcetunnel, -key, and -keyfile.
new ah Set up an SA which uses the new ah transforms. Authentication
will be done with HMAC using the specified hash algorithm. Al-
lowed modifiers are: -dst, -src, -proxy, -spi, -srcid_type,
-srcid, -dstid_type, -dstid, -forcetunnel, -auth, -key, and
old ah Set up an SA which uses the old ah transforms. Simple keyed
hashes will be used for authentication. Allowed modifiers are:
-dst, -src, -proxy, -spi, -srcid_type, -srcid, -dstid_type,
-dstid, -forcetunnel, -auth, -key, and -keyfile.
group Group two SAs together, such that whenever the first one is ap-
plied, the second one will be applied as well (SA bundle). Ar-
bitrarily long SA bundles can thus be created. Note that the
last SA in the bundle is the one that is applied last. Thus, if
an ESP and an AH SA are bundled together (in that order), then
the resulting packet will have an AH header, followed by an ESP
header, followed by the encrypted payload. Allowed modifiers
are: -dst, -spi, -proto, -dst2, -spi2, and -proto2.
ip4 Set up an SA which uses the IP-in-IP encapsulation protocol.
This mode offers no security services by itself, but can be used
to route other (experimental or otherwise) protocols over an IP
network. The SPI value is not used for anything other than ref-
erencing the information, and does not appear on the wire. Un-
like other setups, like new esp, there is no necessary setup in
the receiving side. Allowed modifiers are: -dst, -src, and
delspi The specified SA will be deleted. Allowed modifiers are: -dst,
-spi, and -proto.
flow Create a flow determining what security parameters a packet
should have (input or output). Allowed modifiers are: -src,
-dst, -proto, -addr, -transport, -sport, -dport, -delete, -in,
-out, -srcid, -dstid, -srcid_type, -dstid_type, -acquire,
-require, -dontacq, -use, -bypass, -permit and -deny. The
netstat(1) command shows all specified flows. Flows are direc-
tional, and the -in and -out modifiers are used to specify the
direction. By default, flows are assumed to apply to outgoing
packets. The kernel will attempt to find an appropriate Securi-
ty Association from those already present (an SA that matches
the destination address, if set, and the security protocol). If
the destination address is set to all zeroes (0.0.0.0) or left
unspecified, the destination address from the packet will be
used to locate an SA (the source address is used for incoming
flows). For incoming flows, the destination address (if speci-
fied) should point to the expected source of the SA (the remote
SA peer). If no such SA exists, key management daemons will be
used to generate them if -acquire or -require were used. If
-acquire was used, traffic will be allowed out (or in) and IPsec
will be used when the relevant SAs have been established. If
-require was used, traffic will not be allowed in or out until
it is protected by IPsec. If -dontacq was used, traffic will
not be allowed in or out until it is protected by IPsec, but key
management will not be asked to provide such an SA. The -proto
argument (by default set to esp) will be used to determine what
type of SA should be established. A bypass or permit flow is
used to specify a flow for which IPsec processing will be by-
passed, i.e packets will/need not be processed by any SAs. For
bypass or permit flows, additional modifiers are restricted to:
-addr, -transport, -sport, -dport, -in, -out, and -delete. A
deny flow is used to specify classes of packets that must be
dropped (either on output or input) without further processing.
deny takes the same additional modifiers as bypass.
flush Flush SAs from kernel. This includes flushing any flows and
routing entries associated with the SAs. Allowed modifiers are:
-ah, -esp, -oldah, -oldesp, -ip4, -ipcomp, and -tcpmd5. Default
action is to flush all types of security associations from the
show Show SAs from kernel. Allowed modifiers are: -ah, -esp, -oldah,
-oldesp, -ip4, -ipcomp, and -tcpmd5. Default action is to show
all types of security associations from the kernel.
monitor Continuously display all PF_KEY messages exchanged with the ker-
ipcomp Set up an IP Compression Association (IPCA) which will use the
IPcomp transforms. Just like an SA, an IPCA consists of the
destination address, a Compression Parameter Index (CPI) and a
protocol (which is fixed to IPcomp). Compression algorithms are
applied. Allowed modifiers are: -dst, -src, -cpi, -comp, and
-forcetunnel. To create an IPsec SA using compression, an IPCA
and an SA must first be created. After this an IPCA/SA bundle
must be created using the group keyword. The IPCA must be ap-
tcpmd5 Set up a key for use by the RFC 2385 TCP MD5 option. Allowed
modifiers are: -dst, -src, -spi, -key, and -keyfile.
If no command is given ipsecadm defaults to new esp mode.
The modifiers have the following meanings:
-src The source IP address for the SA. This is necessary for in-
coming SAs to avoid source address spoofing between mutually
suspicious hosts that have established SAs with us. For out-
going SAs, this field is used to fill in the source address
when doing tunneling.
-dst The destination IP address for the SA.
The second IP address used by group.
This IP address, if provided, is checked against the inner IP
address when doing tunneling to a firewall, to prevent source
spoofing attacks. It is strongly recommended that this op-
tion is provided when applicable. It is applicable in a sce-
nario when host A is using IPsec to communicate with firewall
B, and through that to host C. In that case, the proxy ad-
dress for the incoming SA should be C. This option is not
necessary for outgoing SAs.
-spi The Security Parameter Index (SPI), given as a hexadecimal
The second SPI used by group.
-cpi The Compression Parameter Index (CPI), given as a 16 bit hex-
This option has been deprecated. The arguments are ignored,
and it otherwise has the same effect as the forcetunnel op-
This option has been deprecated.
Force IP-inside-IP encapsulation before ESP or AH processing
is performed for outgoing packets. The source/destination
addresses of the outgoing IP packet will be those provided in
the src and dst options. Notice that the IPsec stack will
perform IP-inside-IP encapsulation when deemed necessary,
even if this flag has not been set.
Enable ESP-inside-UDP encapsulation. The UDP destination
port must be specified on the command line. This port will
be used for sending encapsulated UDP packets.
-enc The encryption algorithm to be used with the SA. Possible
des This is available for both old and new esp. Notice
that hardware crackers for DES can be (and have
been) built for US$250,000 (in 1998). Use DES for
encryption of critical information at your own
risk. We suggest using 3DES or AES instead. DES
support is kept for interoperability (with old im-
plementations) purposes only. See des_cipher(3).
3des This is available for both old and new esp. It is
considered more secure than straight DES, since it
uses larger keys.
aes Rijndael encryption is available only in new esp.
blf Blowfish encryption is available only in new esp.
cast CAST encryption is available only in new esp.
skipjack SKIPJACK encryption is available only in new esp.
This algorithm was designed by the NSA and is
faster than 3DES. However, since it was designed
by the NSA it is a poor choice.
The authentication algorithm to be used with the SA. Possi-
ble values are: md5 and sha1 for both old and new ah and also
new esp. Also rmd160, sha2-256, sha2-384, sha2-512 for both
new ah and esp.
The compression algorithm to be used with the IPCA. Possible
values are: deflate and lzs. Note that lzs is only available
with hifn(4) because of the patent held by Hifn, Inc.
-key The secret symmetric key used for encryption and authentica-
tion. The size for des and 3des is fixed to 8 and 24 respec-
tively. For other ciphers like cast, aes, or blf the key
length can vary (depending on the algorithm). The key should
be given in hexadecimal digits. The key should be chosen at
random (ideally, using some true-random source like coin
flipping). It is very important that the key is not guess-
able. One practical way of generating 160-bit (20-byte) keys
is as follows:
$ openssl rand 20 | hexdump -e '20/1 "%02x"'
Read the key from a file. May be used instead of the -key
flag, and has the same syntax considerations.
The secret key material used for authentication if additional
authentication in new esp mode is required. For old or new
ah the key material for authentication is passed with the key
option. The key should be given in hexadecimal digits. The
key should be chosen at random (ideally, using some true-ran-
dom source like coin flipping). It is very important that
the key is not guessable. One practical way of generating
160-bit (20-byte) keys is as follows:
$ openssl rand 20 | hexdump -e '20/1 "%02x"'
Read the authkey from a file. May be used instead of the
-authkey flag, and has the same syntax considerations.
-iv This option has been deprecated. The argument is ignored.
When applicable, it has the same behaviour as the halfiv op-
This option causes use of a 4 byte IV in old ESP (as opposed
to 8 bytes). It may only be used with old ESP.
The security protocol needed by delspi or flow, to uniquely
specify the SA. The default value is 50 which means
IPPROTO_ESP. Other accepted values are 51 (IPPROTO_AH), and
4 (IPPROTO_IP). One can also specify the symbolic names
"esp", "ah", and "ip4", case insensitive.
The second security protocol used by group. It defaults to
IPPROTO_AH, otherwise takes the same values as -proto.
The source address, source network mask, destination address
and destination network mask against which packets need to
match to use the specified Security Association. Alterna-
tively, addresses and masks can be specified as
``source/prefixlen destination/prefixlen''. All addresses
must be of the same address family (IPv4 or IPv6).
The protocol number which packets need to match to use the
specified Security Association. By default the protocol num-
ber is not used for matching. Instead of a number, a valid
protocol name that appears in protocols(5) can be used.
The source port which packets have to match for the flow. By
default the source port is not used for matching. Instead of
a number, a valid service name that appears in services(5)
can be used.
The destination port which packets have to match for the
flow. By default the source port is not used for matching.
Instead of a number, a valid service name that appears in
services(5) can be used.
For flow, used to specify what local identity key management
should use when negotiating the SAs. If left unspecified,
the source address of the flow is used (see the discussion on
flow above, with regard to source address).
For flow, used to specify what the remote identity key man-
agement should expect is. If left unspecified, the destina-
tion address of the flow is used (see the discussion on flow
above, with regard to destination address).
For flow, used to specify the type of identity given by
-srcid. Valid values are prefix, fqdn, and ufqdn. The
prefix type implies an IPv4 or IPv6 address followed by a
forward slash character and a decimal number indicating the
number of important bits in the address (equivalent to a net-
mask, in IPv4 terms). Key management then has to pick a lo-
cal identity that falls within the address space indicated.
The fqdn and ufqdn types are DNS-style host names and mail-
box-format user addresses, respectively, and are especially
useful for mobile user scenarios. Note that no validity
checking on the identities is done.
Instead of creating a flow, an existing flow is deleted.
For flow, create or delete a bypass flow. Packets matching
this flow will not be processed by IPsec.
Same as -bypass.
For flow, create or delete a deny flow. Packets matching
this flow will be dropped.
-use For flow, specify that packets matching this flow should try
to use IPsec if possible.
For flow, specify that packets matching this flow should try
to use IPsec and establish SAs dynamically if possible, but
permit unencrypted traffic.
For flow, specify that packets matching this flow must use
IPsec, and establish SAs dynamically as needed. If no SAs
are established, traffic is not allowed through.
For flow, specify that packets matching this flow must use
IPsec. If such SAs are not present, simply drop the packets.
Such a policy may be used to demand peers establish SAs be-
fore they can communicate with us, without going through the
burden of initiating the SA ourselves (thus allowing for some
denial of service attacks). This flow type is particularly
suitable for security gateways.
-in For flow, specify that it should be used to match incoming
-out For flow, specify that it should be used to match outgoing
-ah For flush, only flush SAs of type ah.
-esp For flush, only flush SAs of type esp.
For flush, only flush SAs of type old ah.
For flush, only flush SAs of type old esp.
-ip4 For flush, only flush SAs of type ip4.
Set up an SA which uses new esp with 3des encryption and HMAC-SHA1 au-
# ipsecadm new esp -enc 3des -auth sha1 -spi 100a -dst 126.96.36.199 \
-src 188.8.131.52 \
-key 638063806380638063806380638063806380638063806380 \
Set up an SA for authentication with old ah only:
# ipsecadm old ah -auth md5 -spi 10f2 -dst 184.108.40.206 -src 220.127.116.11 \
Set up a flow requiring use of AH:
# ipsecadm flow -dst 18.104.22.168 -proto ah \
-addr 10.1.1.0/24 10.0.0.0/24 -out -require
Set up an inbound SA:
# ipsecadm new esp -enc blf -auth md5 -spi 1002 -dst 22.214.171.124 \
-src 126.96.36.199 \
-key abadbeef15deadbeefabadbeef15deadbeefabadbeef15deadbeef \
Set up an ingress flow for the inbound SA:
# ipsecadm flow -addr 10.0.0.0/8 10.1.1.0/24 \
-dst 188.8.131.52 -proto esp -in -require
Set up a bypass flow:
# ipsecadm flow -bypass -out \
-addr 10.1.1.0/24 10.1.1.0/24
Set up a key for the TCP MD5 option:
# ipsecadm tcpmd5 -src ::1 -dst ::1 -spi 0100 -key deadbeef
Delete all esp SAs and their flows and routing information:
# ipsecadm flush -esp
netstat(1), enc(4), ipsec(4), protocols(5), services(5), sysctl.conf(5),
OpenBSD 3.6 August 26, 1997 7