KEYCTL(1)

Linux Key Management Utilities

KEYCTL(1)

NAME
keyctl - key management facility control

SYNOPSIS
keyctl --version
keyctl show [-x] [<keyring>]
keyctl add <type> <desc> <data> <keyring>
keyctl padd <type> <desc> <keyring>
keyctl request <type> <desc> [<dest_keyring>]
keyctl request2 <type> <desc> <info> [<dest_keyring>]
keyctl prequest2 <type> <desc> [<dest_keyring>]
keyctl update <key> <data>
keyctl pupdate <key>
keyctl newring <name> <keyring>
keyctl revoke <key>
keyctl clear <keyring>
keyctl link <key> <keyring>
keyctl unlink <key> [<keyring>]
keyctl search <keyring> <type> <desc> [<dest_keyring>]
keyctl restrict_keyring <keyring> [<type> [<restriction>]]
keyctl read <key>
keyctl pipe <key>
keyctl print <key>
keyctl list <keyring>
keyctl rlist <keyring>
keyctl describe <keyring>
keyctl rdescribe <keyring> [sep]
keyctl chown <key> <uid>
keyctl chgrp <key> <gid>
keyctl setperm <key> <mask>
keyctl new_session
keyctl session
keyctl session - [<prog> <arg1> <arg2> ...]
keyctl session <name> [<prog> <arg1> <arg2> ...]
keyctl instantiate <key> <data> <keyring>
keyctl pinstantiate <key> <keyring>
keyctl negate <key> <timeout> <keyring>
keyctl reject <key> <timeout> <error> <keyring>
keyctl timeout <key> <timeout>
keyctl security <key>
keyctl reap [-v]
keyctl purge <type>
keyctl purge [-i] [-p] <type> <desc>
keyctl purge -s <type> <desc>
keyctl get_persistent <keyring> [<uid>]
keyctl dh_compute <private> <prime> <base>
keyctl dh_compute_kdf <private> <prime> <base> <output_length> <hash_type>
keyctl dh_compute_kdf_oi <private> <prime> <base> <output_length>
<hash_type>
keyctl pkey_query <key> <pass> [k=v]*
keyctl pkey_encrypt <key> <pass> <datafile> [k=v]* ><encfile>
keyctl pkey_decrypt <key> <pass> <encfile> [k=v]* ><datafile>
keyctl pkey_sign <key> <pass> <datafile> [k=v]* ><sigfile>
keyctl pkey_decrypt <key> <pass> <datafile> <sigfile> [k=v]*
DESCRIPTION
This program is used to control the key management facility in various ways
using a variety of subcommands.

KEY IDENTIFIERS
The key identifiers passed to or returned from keyctl are, in general,
positive integers. There are, however, some special values with special meanings
that can be passed as arguments:

No key: 0

Thread keyring: @t or -1
Each thread may have its own keyring. This is searched first, before
all others. The thread keyring is replaced by (v)fork, exec and clone.

Process keyring: @p or -2
Each process (thread group) may have its own keyring. This is shared
between all members of a group and will be searched after the thread keyring. The
process keyring is replaced by (v)fork and exec.

Session keyring: @s or -3
Each process subscribes to a session keyring that is inherited across
(v)fork, exec and clone. This is searched after the process keyring. Session
keyrings can be named and an extant keyring can be joined in place of a
process's current session keyring.

User specific keyring: @u or -4

This keyring is shared between all the processes owned by a
particular user. It isn't searched directly, but is normally linked to from the
session keyring.

User default session keyring: @us or -5

This is the default session keyring for a particular user. Login
processes that change to a particular user will bind to this session until another
session is set.

Group specific keyring: @g or -6

This is a place holder for a group specific keyring, but is not
actually implemented yet in the kernel.

Assumed request_key authorisation key: @a or -7

This selects the authorisation key provided to the request_key()
helper to permit it to access the callers keyrings and instantiate the target key.

Keyring by name: %:<name>

A named keyring. This will be searched for in the process's keyrings
and in /proc/keys.

Key by name: %<type>:<name>

A named key of the given type. This will be searched for in the
process's keyrings and in /proc/keys.

COMMAND SYNTAX
Any non-ambiguous shortening of a command name may be used in lieu of the
full command name. This facility should not be used in scripting as new commands
may be added in future that then cause ambiguity.

Display the package version number

keyctl --version
 This command prints the package version number and build date and exits:

$ keyctl --version
keyctl from keyutils-1.5.3 (Built 2011-08-24)

Show process keyrings

keyctl show [-x] [<keyring>]

By default this command recursively shows what keyrings a process is

subscribed to and what keys and keyrings they contain. If a keyring is specified
then that keyring will be dumped instead. If -x is specified then the
keyring IDs will be dumped in hex instead of decimal.

Add a key to a keyring

keyctl add <type> <desc> <data> <keyring>
keyctl padd <type> <desc> <keyring>

This command creates a key of the specified type and description;

instantiates it with the given data and attaches it to the specified keyring. It
then prints the new key's ID on stdout:

$ keyctl add user mykey stuff @u

26

The padd variant of the command reads the data from stdin rather than taking
it from the command line:

$ echo -n stuff | keyctl padd user mykey @u 26

Request a key
keyctl request <type> <desc> [<dest_keyring>]
keyctl request2 <type> <desc> <info> [<dest_keyring>]
keyctl prequest2 <type> <desc> [<dest_keyring>]

These three commands request the lookup of a key of the given type
and description. The process's keyrings will be searched, and if a match is found
the matching key's ID will be printed to stdout; and if a destination
keyring is given, the key will be added to that keyring also.

If there is no key, the first command will simply return the error ENOKEY
and fail. The second and third commands will create a partial key with the type and
description, and call out to /sbin/request-key with that key and
the extra information supplied. This will then attempt to instantiate the
key in some manner, such that a valid key is obtained.

The third command is like the second, except that the callout information is
read from stdin rather than being passed on the command line.

If a valid key is obtained, the ID will be printed and the key attached as
if the original search had succeeded.

If there wasn't a valid key obtained, a temporary negative key will be

attached to the destination keyring if given and the error "Requested key not
available" will be given.

$ keyctl request2 user debug:hello wibble

23
$ echo -n wibble | keyctl prequest2 user debug:hello
 23
$ keyctl request user debug:hello
23

Update a key
keyctl update <key> <data>
keyctl pupdate <key>

This command replaces the data attached to a key with a new set of data. If
the type of the key doesn't support update then error "Operation not supported"
will be returned.

$ keyctl update 23 zebra

The pupdate variant of the command reads the data from stdin rather than
taking it from the command line:

$ echo -n zebra | keyctl pupdate 23

Create a keyring
keyctl newring <name> <keyring>

This command creates a new keyring of the specified name and attaches it to
the specified keyring. The ID of the new keyring will be printed to stdout if
successful.

$ keyctl newring squelch @us

27

Revoke a key
keyctl revoke <key>

This command marks a key as being revoked. Any further operations on that
key (apart from unlinking it) will return error "Key has been revoked".

$ keyctl revoke 26
$ keyctl describe 26
keyctl_describe: Key has been revoked

Clear a keyring
keyctl clear <keyring>

This command unlinks all the keys attached to the specified keyring. Error
"Not a directory" will be returned if the key specified is not a keyring.

$ keyctl clear 27

Link a key to a keyring

keyctl link <key> <keyring>

This command makes a link from the key to the keyring if there's enough
capacity to do so. Error "Not a directory" will be returned if the destination is
not a keyring. Error "Permission denied" will be returned if the key
doesn't have link permission or the keyring doesn't have write permission.
Error "File table overflow" will be returned if the keyring is full. Error
"Resource deadlock avoided" will be returned if an attempt was made to in‐
troduce a recursive link.

$ keyctl link 23 27
 $ keyctl link 27 27
keyctl_link: Resource deadlock avoided

Unlink a key from a keyring or the session keyring tree

keyctl unlink <key> [<keyring>]

If the keyring is specified, this command removes a link to the key from
the keyring. Error "Not a directory" will be returned if the destination is not a
keyring. Error "Permission denied" will be returned if the keyring
doesn't have write permission. Error "No such file or directory" will be
returned if the key is not linked to by the keyring.

If the keyring is not specified, this command performs a depth-first search

of the session keyring tree and removes all the links to the nominated key that it
finds (and that it is permitted to remove). It prints the number
of successful unlinks before exiting.

$ keyctl unlink 23 27

Search a keyring
keyctl search <keyring> <type> <desc> [<dest_keyring>]

This command non-recursively searches a keyring for a key of a particular

type and description. If found, the ID of the key will be printed on stdout and the
key will be attached to the destination keyring if present. Error
"Requested key not available" will be returned if the key is not found.

$ keyctl search @us user debug:hello

23
$ keyctl search @us user debug:bye
keyctl_search: Requested key not available

Restrict a keyring
keyctl restrict_keyring <keyring> [<type> [<restriction>]]

This command limits the linkage of keys to the given keyring using a
provided restriction scheme. The scheme is associated with a given key type, with
further details provided in the restriction option string. Options typi‐
cally contain a restriction name possibly followed by key ids or other data
relevant to the restriction. If no restriction scheme is provided, the keyring will
reject all links.

$ keyctl restrict_keyring $1 asymmetric builtin_trusted

Read a key
keyctl read <key>
keyctl pipe <key>
keyctl print <key>

These commands read the payload of a key. "read" prints it on stdout as a

hex dump, "pipe" dumps the raw data to stdout and "print" dumps it to stdout
directly if it's entirely printable or as a hexdump preceded by ":hex:" if
not.

If the key type does not support reading of the payload, then error
"Operation not supported" will be returned.

$ keyctl read 26
1 bytes of data in key:
 62
$ keyctl print 26
b
$ keyctl pipe 26
$

List a keyring
keyctl list <keyring>
keyctl rlist <keyring>

These commands list the contents of a key as a keyring. "list" pretty prints
the contents and "rlist" just produces a space-separated list of key IDs.

No attempt is made to check that the specified keyring is a keyring.

$ keyctl list @us

2 keys in keyring:
22: vrwsl---------- 4043 -1 keyring: _uid.4043
23: vrwsl---------- 4043 4043 user: debug:hello
$ keyctl rlist @us
22 23

Describe a key
keyctl describe <keyring>
keyctl rdescribe <keyring> [sep]

These commands fetch a description of a keyring. "describe" pretty prints

the description in the same fashion as the "list" command; "rdescribe" prints the
raw data returned from the kernel.

$ keyctl describe @us

-5: vrwsl---------- 4043 -1 keyring: _uid_ses.4043
$ keyctl rdescribe @us
keyring;4043;-1;3f1f0000;_uid_ses.4043

The raw string is "<type>;<uid>;<gid>;<perms>;<description>", where uid and

gid are the decimal user and group IDs, perms is the permissions mask in hex, type
and description are the type name and description strings (neither
of which will contain semicolons).

Change the access controls on a key

keyctl chown <key> <uid>
keyctl chgrp <key> <gid>

These two commands change the UID and GID associated with evaluating a key's
permissions mask. The UID also governs which quota a key is taken out of.

The chown command is not currently supported; attempting it will earn the
error "Operation not supported" at best.

For non-superuser users, the GID may only be set to the process's GID or a
GID in the process's groups list. The superuser may set any GID it likes.

$ sudo keyctl chown 27 0

keyctl_chown: Operation not supported
$ sudo keyctl chgrp 27 0

Set the permissions mask on a key

keyctl setperm <key> <mask>
 This command changes the permission control mask on a key. The mask may be
specified as a hex number if it begins "0x", an octal number if it begins "0" or a
decimal number otherwise.

The hex numbers are a combination of:

Possessor UID GID Other Permission Granted

======== ======== ======== ======== ==================
01000000 00010000 00000100 00000001 View
02000000 00020000 00000200 00000002 Read
04000000 00040000 00000400 00000004 Write
08000000 00080000 00000800 00000008 Search
10000000 00100000 00001000 00000010 Link
20000000 00200000 00002000 00000020 Set Attribute
3f000000 003f0000 00003f00 0000003f All

View permits the type, description and other parameters of a key to be

viewed.

Read permits the payload (or keyring list) to be read if supported by the
type.

Write permits the payload (or keyring list) to be modified or updated.

Search on a key permits it to be found when a keyring to which it is linked

is searched.

Link permits a key to be linked to a keyring.

Set Attribute permits a key to have its owner, group membership, permissions
mask and timeout changed.

$ keyctl setperm 27 0x1f1f1f00

Start a new session with fresh keyrings

keyctl session
keyctl session - [<prog> <arg1> <arg2> ...]
keyctl session <name> [<prog> <arg1> <arg2> ...]

These commands join or create a new keyring and then run a shell or other
program with that keyring as the session key.

The variation with no arguments just creates an anonymous session keyring

and attaches that as the session keyring; it then exec's $SHELL.

The variation with a dash in place of a name creates an anonymous session

keyring and attaches that as the session keyring; it then exec's the supplied
command, or $SHELL if one isn't supplied.

The variation with a name supplied creates or joins the named keyring and
attaches that as the session keyring; it then exec's the supplied command, or
$SHELL if one isn't supplied.

$ keyctl rdescribe @s
keyring;4043;-1;3f1f0000;_uid_ses.4043

$ keyctl session
Joined session keyring: 28
 $ keyctl rdescribe @s
keyring;4043;4043;3f1f0000;_ses.24082

$ keyctl session -
Joined session keyring: 29
$ keyctl rdescribe @s
keyring;4043;4043;3f1f0000;_ses.24139

$ keyctl session - keyctl rdescribe @s

Joined session keyring: 30
keyring;4043;4043;3f1f0000;_ses.24185

$ keyctl session fish

Joined session keyring: 34
$ keyctl rdescribe @s
keyring;4043;4043;3f1f0000;fish

$ keyctl session fish keyctl rdesc @s

Joined session keyring: 35
keyring;4043;4043;3f1f0000;fish

Instantiate a key
keyctl instantiate <key> <data> <keyring>
keyctl pinstantiate <key> <keyring>
keyctl negate <key> <timeout> <keyring>
keyctl reject <key> <timeout> <error> <keyring>

These commands are used to attach data to a partially set up key (as
created by the kernel and passed to /sbin/request-key). "instantiate" marks a key
as being valid and attaches the data as the payload. "negate" and "re‐
ject" mark a key as invalid and sets a timeout on it so that it'll go away
after a while. This prevents a lot of quickly sequential requests from slowing the
system down overmuch when they all fail, as all subsequent re‐
quests will then fail with error "Requested key not found" (if negated) or
the specified error (if rejected) until the negative key has expired.

Reject's error argument can either be a UNIX error number or one of

'rejected', 'expired' or 'revoked'.

The newly instantiated key will be attached to the specified keyring.

These commands may only be run from the program run by request-key - a
special authorisation key is set up by the kernel and attached to the request-key's
session keyring. This special key is revoked once the key to which it
refers has been instantiated one way or another.

$ keyctl instantiate $1 "Debug $3" $4

$ keyctl negate $1 30 $4
$ keyctl reject $1 30 64 $4

The pinstantiate variant of the command reads the data from stdin rather
than taking it from the command line:

$ echo -n "Debug $3" | keyctl pinstantiate $1 $4

Set the expiry time on a key

keyctl timeout <key> <timeout>
 This command is used to set the timeout on a key, or clear an existing
timeout if the value specified is zero. The timeout is given as a number of seconds
into the future.

$ keyctl timeout $1 45

Retrieve a key's security context

keyctl security <key>

This command is used to retrieve a key's LSM security context. The label is
printed on stdout.

$ keyctl security @s
unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023

Give the parent process a new session keyring

keyctl new_session

This command is used to give the invoking process (typically a shell) a new
session keyring, discarding its old session keyring.

$ keyctl session foo

Joined session keyring: 723488146
$ keyctl show
Session Keyring
-3 --alswrv 0 0 keyring: foo
$ keyctl new_session
490511412
$ keyctl show
Session Keyring
-3 --alswrv 0 0 keyring: _ses

Note that this affects the parent of the process that invokes the system
call, and so may only affect processes with matching credentials. Furthermore, the
change does not take effect till the parent process next transitions
from kernel space to user space - typically when the wait() system call
returns.

Remove dead keys from the session keyring tree

keyctl reap

This command performs a depth-first search of the caller's session keyring

tree and attempts to unlink any key that it finds that is inaccessible due to
expiry, revocation, rejection or negation. It does not attempt to re‐
move live keys that are unavailable simply due to a lack of granted
permission.

A key that is designated reapable will only be removed from a keyring if the
caller has Write permission on that keyring, and only keyrings that grant Search
permission to the caller will be searched.

The command prints the number of keys reaped before it exits. If the -v
flag is passed then the reaped keys are listed as they're being reaped, together
with the success or failure of the unlink.

Remove matching keys from the session keyring tree

keyctl purge <type>
keyctl purge [-i] [-p] <type> <desc>
keyctl purge -s <type> <desc>
 These commands perform a depth-first search to find matching keys in the
caller's session keyring tree and attempts to unlink them. The number of keys
successfully unlinked is printed at the end.

The keyrings must grant Read and View permission to the caller to be
searched, and the keys to be removed must also grant View permission. Keys can
only be removed from keyrings that grant Write permission.

The first variant purges all keys of the specified type.

The second variant purges all keys of the specified type that also match the
given description literally. The -i flag allows a case-independent match and the -
p flag allows a prefix match.

The third variant purges all keys of the specified type and matching
description using the key type's comparator in the kernel to match the description.
This permits the key type to match a key with a variety of descrip‐
tions.

Get persistent keyring

keyctl get_persistent <keyring> [<uid>]

This command gets the persistent keyring for either the current UID or the
specified UID and attaches it to the nominated keyring. The persistent keyring's
ID will be printed on stdout.

The kernel will create the keyring if it doesn't exist and every time this
command is called, will reset the expiration timeout on the keyring to the value
in:

/proc/sys/kernel/keys/persistent_keyring_expiry

(by default three days). Should the timeout be reached, the persistent
keyring will be removed and everything it pins can then be garbage collected.

If a UID other than the process's real or effective UIDs is specified, then
an error will be given if the process does not have the CAP_SETUID capability.

Compute a Diffie-Hellman shared secret or public key

keyctl dh_compute <private> <prime> <base>

This command computes either a Diffie-Hellman shared secret or the public

key corresponding to the provided private key using the payloads of three keys. The
computation is:

base ^ private (mod prime)

The three inputs must be user keys with read permission. If the
provided base key contains the shared generator value, the public key will be
computed. If the provided base key contains the remote public key value, the
shared secret will be computed.

The result is printed to stdout as a hex dump.

$ keyctl dh_compute $1 $2 $3
8 bytes of data in result:
00010203 04050607
 Compute a Diffie-Hellman shared secret and derive key material
keyctl dh_compute_kdf <private> <prime> <base> <output_length> <hash_type>

This command computes a Diffie-Hellman shared secret and derives key

material from the shared secret using a key derivation function (KDF). The shared
secret is derived as outlined above and is input to the KDF using the
specified hash type. The hash type must point to a hash name known to the
kernel crypto API.

The operation derives key material of the length specified by the caller.

The operation is compliant to the specification of SP800-56A.

The result is printed to stdout as hex dump.

Compute a Diffie-Hellman shared secret and apply KDF with other input
keyctl dh_compute_kdf_oi <private> <prime> <base> <output_length>
<hash_type>

This command is identical to the command dh_compute_kdf to generate a

Diffie-Hellman shared secret followed by a key derivation operation. This command
allows the caller to provide the other input data (OI data) compliant to
SP800-56A via stdin.

Perform public-key operations with an asymmetric key

keyctl pkey_query <key> <pass> [k=v]*
keyctl pkey_encrypt <key> <pass> <datafile> [k=v]* > <encfile>
keyctl pkey_decrypt <key> <pass> <encfile> [k=v]* > <datafile>
keyctl pkey_sign <key> <pass> <datafile> [k=v]* > <sigfile>
keyctl pkey_verify <key> <pass> <datafile> <sigfile> [k=v]*

These commands query an asymmetric key, encrypt data with it, decrypt the
encrypted data, generate a signature over some data and verify that signature. For
encrypt, decrypt and sign, the resulting data is written to stdout;
verify reads the data and the signature files and compares them.

[!] NOTE that the data is of very limited capacity, with no more bits than
the size of the key. For signatures, the caller is expected to digest the actual
data and pass in the result of the digest as the datafile. The name
of the digest should be specified on the end of the command line as
"hash=<name>".

The key ID indicates the key to use; pass is a placeholder for future
password provision and should be "0" for the moment; datafile is the unencrypted
data to be encrypted, signed or to have its signature checked; encfile is
a file containing encrypted data; and sigfile is a file containing a
signature.

A list of parameters in "key[=val]" form can be included on the end of the

command line. These specify things like the digest algorithm used ("hash=<name>")
or the encoding form ("enc=<type>").

k=`keyctl padd asymmetric "" @s <key.pkcs8.der`

keyctl pkey_query $k 0 enc=pkcs1 hash=sha256
keyctl pkey_encrypt $k 0 foo.hash enc=pkcs1 >foo.enc
keyctl pkey_decrypt $k 0 foo.enc enc=pkcs1 >foo.hash
keyctl pkey_sign $k 0 foo.hash enc=pkcs1 hash=sha256 >foo.sig
keyctl pkey_verify $k 0 foo.hash foo.sig enc=pkcs1 hash=sha256
 See asymmetric-key(7) for more information.

ERRORS
There are a number of common errors returned by this program:

"Not a directory" - a key wasn't a keyring.

"Requested key not found" - the looked for key isn't available.

"Key has been revoked" - a revoked key was accessed.

"Key has expired" - an expired key was accessed.

"Permission denied" - permission was denied by a UID/GID/mask combination.

SEE ALSO
keyctl(1), keyctl(2), request_key(2), keyctl(3), request-key.conf(5),
keyrings(7), request-key(8)

Linux
20 Feb 2014
KEYCTL(1)