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Manual Pages  — SETKEY


setkey – manually manipulate the IPsec SA/SP database



setkey [-v] -c
setkey [-v] -f filename
setkey [-Pgltv] -D
setkey [-Pv] -F
setkey [-h] -x


The setkey utility adds, updates, dumps, or flushes Security Association Database (SAD) entries as well as Security Policy Database (SPD) entries in the kernel.

The setkey utility takes a series of operations from the standard input (if invoked with -c) or the file named filename (if invoked with -f filename).
  Dump the SAD entries. If with -P, the SPD entries are dumped.
  Flush the SAD entries. If with -P, the SPD entries are flushed.
  Only SPD entries with global scope are dumped with -D and -P flags.
  Only SPD entries with ifnet scope are dumped with -D and -P flags. Such SPD entries are linked to the corresponding if_ipsec(4) virtual tunneling interface.
  Add hexadecimal dump on -x mode.
  Loop forever with short output on -D.
  Be verbose. The program will dump messages exchanged on PF_KEY socket, including messages sent from other processes to the kernel.
  Loop forever and dump all the messages transmitted to PF_KEY socket. -xx makes each timestamp unformatted.

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 ... amp;; 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 amp;; Show an SAD entry.
delete [-46n] src dst protocol spi amp;; Remove an SAD entry.
deleteall [-46n] src dst protocol amp;; Remove all SAD entries that match the specification.
flush [protocol] amp;; Clear all SAD entries matched by the options. -F on the command line achieves the same functionality.
dump [protocol] amp;; 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 amp;; Add an SPD entry.
spddelete [-46n] src_range dst_range upperspec -P direction amp;; Delete an SPD entry.
spdflush amp;; Clear all SPD entries. -FP on the command line achieves the same functionality.
spddump amp;; Dumps all SPD entries. -DP on the command line achieves the same functionality.

Meta-arguments are as follows:

  Source/destination of the secure communication is specified as IPv4/v6 address. The setkey utility can resolve a 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 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.

  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.
  Do not allow cyclic sequence number.
-lh time
-ls time
  Specify hard/soft life time duration of the SA.

-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.

  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:

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.

  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 is expressed in one of the following three formats:

-P directiondiscard
-P directionnone
protocol/mode/src-dst/level [...]

The direction of a policy must be specified as one of: out or in. The direction is followed by one of the following policy levels: discard, none, or ipsec. The discard policylevel means that packets matching the supplied indices will be discarded while none means that IPsec operations will not take place on the packet and ipsec means that IPsec operation will take place onto the packet. 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.,amp; 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) 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 ‘:amp;’ 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.


The following lists show the supported algorithms.

Authentication Algorithms

The following authentication algorithms can be used as aalgo in the -A aalgo of the protocol parameter:
algorithm       keylen (bits)   comment
hmac-md5        128             ah/esp: rfc2403
                128             ah-old/esp-old: rfc2085
hmac-sha1       160             ah/esp: rfc2404
                160             ah-old/esp-old: 128bit ICV (no document)
keyed-md5       128             ah/esp: 96bit ICV (no document)
                128             ah-old/esp-old: rfc1828
keyed-sha1      160             ah/esp: 96bit ICV (no document)
                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)
hmac-ripemd160  160             ah/esp: 96bit ICV (RFC2857)
                                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

Encryption Algorithms

The following encryption algorithms can be used as the ealgo in the -E ealgo of the protocol parameter:
algorithm       keylen (bits)   comment
des-cbc         64              esp-old: rfc1829, esp: rfc2405
3des-cbc        192             rfc2451
null            0 to 2048       rfc2410
blowfish-cbc    40 to 448       rfc2451
cast128-cbc     40 to 128       rfc2451
des-deriv       64              ipsec-ciph-des-derived-01
aes-cbc         128/192/256     rfc3602
aes-ctr         160/224/288     rfc3686
aes-gcm-16      160/224/288     AEAD; rfc4106
camellia-cbc    128/192/256     rfc4312

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


The utility exits 0 on success, and >0 if an error occurs.


Add an ESP SA between two IPv6 addresses using the des-cbc encryption algorithm.
add 3ffe:501:4819::1 3ffe:501:481d::1 esp 123457
        -E des-cbc 0x3ffe05014819ffff ;

Add an authentication SA between two FQDN specified hosts:
add -6 myhost.example.com yourhost.example.com ah 123456
        -A hmac-sha1 "AH SA configuration!" ;

Use both ESP and AH between two numerically specified hosts:
add esp 0x10001
        -E des-cbc 0x3ffe05014819ffff
        -A hmac-md5 "authentication!!" ;

Get the SA information associated with first example above:
get 3ffe:501:4819::1 3ffe:501:481d::1 ah 123456 ;

Flush all entries from the database:
flush ;

Dump the ESP entries from the database:
dump esp ;

Add a security policy between two networks that uses ESP in tunnel mode:
spdadd[21][any] any
        -P out ipsec esp/tunnel/ ;

Use TCP MD5 between two numerically specified hosts:
add tcp 0x1000 -A tcp-md5 "TCP-MD5 BGP secret" ;
add tcp 0x1001 -A tcp-md5 "TCP-MD5 BGP secret" ;


ipsec_set_policy(3), if_ipsec(4), racoon(8), sysctl(8) http://www.kame.net/newsletter/19991007/

Changed manual key configuration for IPsec, October 1999.


The setkey utility first appeared in WIDE Hydrangea IPv6 protocol stack kit. The utility was completely re-designed in June 1998. It first appeared in FreeBSD 4.0 .


The setkey utility should report and handle syntax errors better.

For IPsec gateway configuration, src_range and dst_range with TCP/UDP port number do not work, as the gateway does not reassemble packets (cannot inspect upper-layer headers).

SETKEY (8) September 13, 2022

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