keyctl

KEYCTL(1)               Linux Key Management Utilities               KEYCTL(1)



NAME
       keyctl - Key management facility control

SYNOPSIS
       keyctl show
       keyctl add    
       keyctl padd   
       keyctl request   []
       keyctl request2    []
       keyctl prequest2   []
       keyctl update  
       keyctl pupdate 
       keyctl newring  
       keyctl revoke 
       keyctl clear 
       keyctl link  
       keyctl unlink  
       keyctl search    []
       keyctl read 
       keyctl pipe 
       keyctl print 
       keyctl list 
       keyctl rlist 
       keyctl describe 
       keyctl rdescribe  [sep]
       keyctl chown  
       keyctl chgrp  
       keyctl setperm  
       keyctl session
       keyctl session - [   ...]
       keyctl session  [   ...]
       keyctl instantiate   
       keyctl pinstantiate  
       keyctl negate   
       keyctl timeout  

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  pro‐
       cesses 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  actu‐
       ally 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.

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.

       (*) Show process keyrings

       keyctl show

       This command recursively shows what keyrings a process is subscribed to
       and what keys and keyrings they contain.

       (*) Add a key to a keyring

       keyctl add    
       keyctl padd   

       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:

              testbox>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:

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

       (*) Request a key

       keyctl request   []
       keyctl request2    []
       keyctl prequest2   []

       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 desti‐
       nation 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 informa‐
       tion 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.

              testbox>keyctl request2 user debug:hello wibble
              23
              testbox>echo -n wibble | keyctl prequest2 user debug:hello
              23
              testbox>keyctl request user debug:hello
              23

       (*) Update a key

       keyctl update  
       keyctl pupdate 

       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  "Opera‐
       tion not supported" will be returned.

              testbox>keyctl update 23 zebra

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

              testbox>echo -n zebra | keyctl pupdate 23

       (*) Create a keyring

       keyctl newring  

       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.

              testbox>keyctl newring squelch @us
              27

       (*) Revoke a key

       keyctl revoke 

       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".

              testbox>keyctl revoke 26
              testbox>keyctl describe 26
              keyctl_describe: Key has been revoked

       (*) Clear a keyring

       keyctl clear 

       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.

              testbox>keyctl clear 27

       (*) Link a key to a keyring

       keyctl link  

       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 des‐
       tination 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 introduce a recursive link.

              testbox>keyctl link 23 27
              testbox>keyctl link 27 27
              keyctl_link: Resource deadlock avoided

       (*) Unlink a key from a keyring

       keyctl unlink  

       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.

       Note that this only removes one key link from the keyring; any  further
       links to the same key are not deleted.

              testbox>keyctl unlink 23 27

       (*) Search a keyring

       keyctl search    []

       This command non-recursively searches a keyring for a key of a particu‐
       lar 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.

              testbox>keyctl search @us user debug:hello
              23
              testbox>keyctl search @us user debug:bye
              keyctl_search: Requested key not available

       (*) Read a key

       keyctl read 
       keyctl pipe 
       keyctl print 

       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.

              testbox>keyctl read 26
              1 bytes of data in key:
              62
              testbox>keyctl print 26
              b
              testbox>keyctl pipe 26
              btestbox>

       (*) List a keyring

       keyctl list 
       keyctl rlist 

       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.

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

       (*) Describe a key

       keyctl describe 
       keyctl rdescribe  [sep]

       These  commands  fetch  a  description  of a keyring. "describe" pretty
       prints the description in the same fashion as the "list" command; "rde‐
       scribe" prints the raw data returned from the kernel.

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

       The raw string is ";;;;", 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  
       keyctl chgrp  

       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.

              testbox>sudo keyctl chown 27 0
              keyctl_chown: Operation not supported
              testbox>sudo keyctl chgrp 27 0

       (*) Set the permissions mask on a key

       keyctl setperm  

       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,  per‐
       missions mask and timeout changed.

              testbox>keyctl setperm 27 0x1f1f1f00

       (*) Start a new session with fresh keyrings

       keyctl session
       keyctl session - [   ...]
       keyctl session  [   ...]

       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  ses‐
       sion  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.

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

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

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

              testbox>keyctl session - keyctl rdescribe @s
              Joined session keyring: 30
              keyring;4043;4043;3f1f0000;_ses.24185

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

              testbox>keyctl session fish keyctl rdesc @s
              Joined session keyring: 35
              keyring;4043;4043;3f1f0000;fish

       (*) Instantiate a key

       keyctl instantiate   
       keyctl pinstantiate  
       keyctl negate   

       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"  marks 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 requests will then fail with error  "Requested  key  not
       found" until the negative key has expired.

       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.

              testbox>keyctl instantiate $1 "Debug $3" $4
              testbox>keyctl negate $1 30 $4

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

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

       (*) Set the expiry time on a key

       keyctl 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  num‐
       ber of seconds into the future.

              testbox>keyctl timeout $1 45


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 combina‐
       tion.


SEE ALSO
       keyctl(1), request-key.conf(5)



Linux                             17 Nov 2005                        KEYCTL(1)