REQUEST_KEY(2)                                     Linux Key Management Calls                                     REQUEST_KEY(2)



NAME
       request_key - Request a key from the kernel's key management facility

SYNOPSIS
       #include <keyutils.h>

       key_serial_t request_key(const char *type, const char *description,
       const char *callout_info, key_serial_t keyring);

DESCRIPTION
       request_key()  asks the kernel to find a key of the given type that matches the specified description and, if successful,
       to attach it to the nominated keyring and to return its serial number.

       request_key() first recursively searches all the keyrings attached to the calling process in  the  order  thread-specific
       keyring, process-specific keyring and then session keyring for a matching key.

       If  request_key()  is  called  from a program invoked by request_key() on behalf of some other process to generate a key,
       then the keyrings of that other process will be searched next, using that other process's UID, GID, groups  and  security
       context to control access.

       The  keys  in  each keyring searched are checked for a match before any child keyrings are recursed into.  Only keys that
       are searchable for the caller may be found, and only searchable keyrings may be searched.

       If the key is not found then, if callout_info is set, this function will attempt to look further afield.  In such a case,
       the callout_info is passed to a userspace service such as /sbin/request-key to generate the key.

       If that is unsuccessful also, then an error will be returned, and a temporary negative key will be installed in the nomi-
       nated keyring.  This will expire after a few seconds, but will cause subsequent calls to request_key() to fail  until  it
       does.

       The keyring serial number may be that of a valid keyring to which the caller has write permission, or it may be a special
       keyring ID:

       KEY_SPEC_THREAD_KEYRING
              This specifies the caller's thread-specific keyring.

       KEY_SPEC_PROCESS_KEYRING
              This specifies the caller's process-specific keyring.

       KEY_SPEC_SESSION_KEYRING
              This specifies the caller's session-specific keyring.

       KEY_SPEC_USER_KEYRING
              This specifies the caller's UID-specific keyring.

       KEY_SPEC_USER_SESSION_KEYRING
              This specifies the caller's UID-session keyring.

       If a key is created, no matter whether it's a valid key or a negative key, it will displace any other  key  of  the  same
       type and description from the destination keyring.

RETURN VALUE
       On  success  request_key()  returns  the  serial number of the key it found.  On error, the value -1 will be returned and
       errno will have been set to an appropriate error.

ERRORS
       ENOKEY No matching key was found.

       EKEYEXPIRED
              An expired key was found, but no replacement could be obtained.

       EKEYREVOKED
              A revoked key was found, but no replacement could be obtained.

       EKEYREJECTED
              The attempt to generate a new key was rejected.

       ENOMEM Insufficient memory to create a key.

       EINTR  The request was interrupted by a signal.

       EDQUOT The key quota for this user would be exceeded by creating this key or linking it to the keyring.

       EACCES The keyring wasn't available for modification by the user.

LINKING
       Although this is a Linux system call, it is not present in libc but can be found rather in  libkeyutils.   When  linking,
       -lkeyutils should be specified to the linker.

SEE ALSO
       keyctl(1), add_key(2), keyctl(2), request-key(8)



Linux                                                      4 May 2006                                             REQUEST_KEY(2)