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       add_key - Add a key to the kernel’s key management facility


       #include <keyutils.h>

       key_serial_t add_key(const char *type, const char *description,
       const void *payload, size_t plen, key_serial_t keyring);


       add_key()  asks  the kernel to create or update a key of the given type
       and description, instantiate it with the payload of length plen, and to
       attach it to the nominated keyring and to return its serial number.

       The key type may reject the data if it’s in the wrong format or in some
       other way invalid.

       If the destination keyring already contains  a  key  that  matches  the
       specified  type and description then, if the key type supports it, that
       key will be updated rather than a new key being created; if not, a  new
       key  will  be  created  and it will displace the link to the extant key
       from the keyring.

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

              This specifies the caller’s thread-specific keyring.

              This specifies the caller’s process-specific keyring.

              This specifies the caller’s session-specific keyring.

              This specifies the caller’s UID-specific keyring.

              This specifies the caller’s UID-session keyring.


       There are a number of key types available in the  core  key  management
       code, and these can be specified to this function:

       “user” Keys  of  the  user-defined  key  type  may  contain  a  blob of
              arbitrary data, and the description may  be  any  valid  string,
              though  it  is preferred that the description be prefixed with a
              string representing the service to which the key is of  interest
              and  a  colon  (for  instance  “afs:mykey”).  The payload may be
              empty or NULL for keys of this type.

              Keyrings are  special  key  types  that  may  contain  links  to
              sequences  of other keys of any type.  If this interface is used
              to create a keyring, then a NULL payload  should  be  specified,
              and plen should be zero.


       On success add_key() returns the serial number of the key it created or
       updated.  On error, the value -1 will be returned and errno  will  have
       been set to an appropriate error.


       ENOKEY The keyring doesn’t exist.

              The keyring has expired.

              The keyring has been revoked.

       EINVAL The payload data was invalid.

       ENOMEM Insufficient memory to create a key.

       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.


       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.


       keyctl(1), keyctl(2), request_key(2)


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