Configuration syntax

With -c or -f on the command line, setkey accepts the following configuration syntax. Lines starting with hash signs (‘#’) are treated as comment lines.

add [-46n] src dst protocol spi [extensions] algorithm ... ;

Add an SAD entry. add can fail with multiple reasons, including when the key length does not match the specified algorithm.

get [-46n] src dst protocol spi ;

Show an SAD entry.

delete [-46n] src dst protocol spi ;

Remove an SAD entry.

deleteall [-46n] src dst protocol ;

Remove all SAD entries that match the specification.

flush [protocol] ;

Clear all SAD entries matched by the options. -F on the command line achieves the same functionality.

dump [protocol] ;

Dumps all SAD entries matched by the options. -D on the command line achieves the same functionality.

spdadd [-46n] src_range dst_range upperspec policy ;

Add an SPD entry.

spddelete [-46n] src_range dst_range upperspec -P direction ;

Delete an SPD entry.

spdflush ;

Clear all SPD entries. -FP on the command line achieves the same functionality.

spddump ;

Dumps all SPD entries. -DP on the command line achieves the same functionality.

Meta-arguments are as follows:

src

 

dst

Source/destination of the secure communication is specified as IPv4/v6 address. The setkey utility can resolve an FQDN into numeric addresses. If the FQDN resolves into multiple addresses, setkey will install multiple SAD/SPD entries into the kernel by trying all possible combinations. -4, -6 and -n restricts the address resolution of FQDN in certain ways. -4 and -6 restrict results into IPv4/v6 addresses only, respectively. -n avoids FQDN resolution and requires addresses to be numeric addresses.

protocol

protocol is one of following:

esp

ESP based on rfc2406

esp-old

ESP based on rfc1827

ah

AH based on rfc2402

ah-old

AH based on rfc1826

ipcomp

IPComp

tcp

TCP-MD5 based on rfc2385

spi

Security Parameter Index (SPI) for the SAD and the SPD. spi must be a decimal number, or a hexadecimal number with ‘0x’ prefix. SPI values between 0 and 255 are reserved for future use by IANA and they cannot be used.

extensions

take some of the following:

-m mode

Specify a security protocol mode for use. mode is one of following: transport, tunnel or any. The default value is any.

-r size

Specify the bitmap size in octets of the anti-replay window. size is a 32-bit unsigned integer, and its value is one eighth of the anti-replay window size in packets. If size is zero or not specified, an anti-replay check does not take place.

-u id

Specify the identifier of the policy entry in SPD. See policy.

-f pad_option

defines the content of the ESP padding. pad_option is one of following:

zero-pad

All of the padding are zero.

random-pad

A series of randomized values are set.

seq-pad

A series of sequential increasing numbers started from 1 are set.

-f nocyclic-seq

Do not allow cyclic sequence number.

-lh time

 

-ls time

Specify hard/soft life time duration of the SA.

-natt oai [ sport ] oar [ dport ]

Manually configure NAT-T for the SA, by specifying initiator oai and requestor oar ip addresses and ports. Note that the ‘[’ and ‘]’ symbols are part of the syntax for the ports specification, not indication of the optional components.

-natt_mtu fragsize

Configure NAT-T fragment size.

-esn

Enable Extended Sequence Number extension for this SA.

-hwif ifname

Request hardware offload to the specified interface ifname (only). By default offload occurs to all capable interfaces.

algorithm

-E ealgo key

Specify an encryption or Authenticated Encryption with Associated Data (AEAD) algorithm ealgo for ESP.

-E ealgo key -A aalgo key

Specify a encryption algorithm ealgo, as well as a payload authentication algorithm aalgo, for ESP.

-A aalgo key

Specify an authentication algorithm for AH.

-C calgo [-R]

Specify a compression algorithm for IPComp. If -R is specified, the spi field value will be used as the IPComp CPI (compression parameter index) on wire as is. If -R is not specified, the kernel will use well-known CPI on wire, and spi field will be used only as an index for kernel internal usage.

key must be double-quoted character string, or a series of hexadecimal digits preceded by ‘0x’.

Possible values for ealgo, aalgo and calgo are specified in separate section.

src_range

 

dst_range

These are selections of the secure communication specified as IPv4/v6 address or IPv4/v6 address range, and it may accompany TCP/UDP port specification. This takes the following form:

address
address/prefixlen
address[port]
address/prefixlen[port]

prefixlen and port must be a decimal number. The square brackets around port are necessary and are not manpage metacharacters. For FQDN resolution, the rules applicable to src and dst apply here as well.

upperspec

The upper layer protocol to be used. You can use one of the words in /etc/protocols as upperspec, as well as icmp6, ip4, or any. The word any stands for “any protocol”. The protocol number may also be used to specify the upperspec. A type and code related to ICMPv6 may also be specified as an upperspec. The type is specified first, followed by a comma and then the relevant code. The specification must be placed after icmp6. The kernel considers a zero to be a wildcard but cannot distinguish between a wildcard and an ICMPv6 type which is zero. The following example shows a policy where IPSec is not required for inbound Neighbor Solicitations:

spdadd ::/0 ::/0 icmp6 135,0 -P in none;

NOTE: upperspec does not work in the forwarding case at this moment, as it requires extra reassembly at forwarding node, which is not implemented at this moment. Although there are many protocols in /etc/protocols, protocols other than TCP, UDP and ICMP may not be suitable to use with IPsec.

policy

policy is expressed in one of the following three formats:

-P direction discard

 

-P direction none

 

-P direction ipsec protocol/mode/src-dst/level [...]

 

direction

The direction of a policy must be specified as one of: out or in.

policy level

The direction is followed by one of the following policy levels: discard, none, or ipsec.

• The discard policy level means that packets matching the supplied indices will be discarded.
• The none policy level means that IPsec operations will not take place on the packet.
• The ipsec policy level means that IPsec operation will take place onto the packet.

protocol/mode/src-dst/level

The protocol/mode/src-dst/level statement gives the rule for how to process the packet.

• The protocol is specified as ah, esp or ipcomp.
• The mode is either transport or tunnel.

If mode is tunnel, you must specify the end-point addresses of the SA as src and dst with a dash, ‘-’, between the addresses.

If mode is transport, both src and dst can be omitted.

The level is one of the following: default, use, require or unique. If the SA is not available in every level, the kernel will request the SA from the key exchange daemon.

• A value of default tells the kernel to use the system wide default protocol e.g., the one from the esp_trans_deflev sysctl variable, when the kernel processes the packet.
• A value of use means that the kernel will use an SA if it is available, otherwise the kernel will pass the packet as it would normally.
• A value of require means that an SA is required whenever the kernel sends a packet matched that matches the policy.
• The unique level is the same as require but, in addition, it allows the policy to bind with the unique out-bound SA.

  For example, if you specify the policy level unique, racoon(8) (ports/security/ipsec-tools) will configure the SA for the policy. If you configure the SA by manual keying for that policy, you can put the decimal number as the policy identifier after unique separated by colon ‘:’ as in the following example: unique:number. In order to bind this policy to the SA, number must be between 1 and 32767, which corresponds to extensions -u of manual SA configuration.

When you want to use an SA bundle, you can define multiple rules. For example, if an IP header was followed by an AH header followed by an ESP header followed by an upper layer protocol header, the rule would be:

esp/transport//require ah/transport//require

;

The rule order is very important.

Note that “discard” and “none” are not in the syntax described in ipsec_set_policy(3). There are small, but important, differences in the syntax. See ipsec_set_policy(3) for details.

Authentication Algorithms

The following authentication algorithms can be used as aalgo in the -A aalgo of the protocol parameter:

algorithm	keylen (bits)	comment
hmac-sha1	160		ah/esp: rfc2404
		160		ah-old/esp-old: 128bit ICV (no document)
null		0 to 2048	for debugging
hmac-sha2-256	256		ah/esp: 128bit ICV (RFC4868)
		256		ah-old/esp-old: 128bit ICV (no document)
hmac-sha2-384	384		ah/esp: 192bit ICV (RFC4868)
		384		ah-old/esp-old: 128bit ICV (no document)
hmac-sha2-512	512		ah/esp: 256bit ICV (RFC4868)
		512		ah-old/esp-old: 128bit ICV (no document)
aes-xcbc-mac	128		ah/esp: 96bit ICV (RFC3566)
		128		ah-old/esp-old: 128bit ICV (no document)
tcp-md5		8 to 640	tcp: rfc2385
chacha20-poly1305	256	ah/esp: 128bit ICV (RFC7634)

Encryption Algorithms

The following encryption algorithms can be used as the ealgo in the -E ealgo of the protocol parameter:

algorithm	keylen (bits)	comment
null		0 to 2048	rfc2410
aes-cbc		128/192/256	rfc3602
aes-ctr		160/224/288	rfc3686
aes-gcm-16	160/224/288	AEAD; rfc4106
chacha20-poly1305	256	rfc7634

Note that the first 128/192/256 bits of a key for aes-ctr or aes-gcm-16 will be used as the AES key, and the remaining 32 bits will be used as the nonce.

AEAD encryption algorithms such as aes-gcm-16 include authentication and should not be paired with a separate authentication algorithm via -A.

Compression Algorithms

The following compression algorithms can be used as the calgo in the -C calgo of the protocol parameter:

algorithm	comment
deflate		rfc2394