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 user-space 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  nominated  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

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

       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.

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

       EKEYREJECTED
              The attempt to generate a new key was rejected.

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

       ENOMEM Insufficient memory to create a key.

       ENOKEY No matching key was found.

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), keyctl(3), keyrings(7), request-key(8)

COLOPHON

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       information   about   reporting   bugs,   and   the  latest  version  of  this  page,  can  be  found  at
       http://www.kernel.org/doc/man-pages/.