NAME

       keyctl_read - Read a key

SYNOPSIS

       #include <keyutils.h>

       long keyctl_read(key_serial_t key, char *buffer,
       size_tbuflen);

       long keyctl_read_alloc(key_serial_t key, void **_buffer);

DESCRIPTION

       keyctl_read() reads the payload of a key if the key type supports it.

       The caller must have read permission on a key to be able to read it.

       buffer  and  buflen specify the buffer into which the payload data will be placed.  If the
       buffer is too small, the full size of the payload will be returned, and no copy will  take
       place.

       keyctl_read_alloc()  is  similar  to  keyctl_read()  except that it allocates a buffer big
       enough to hold the payload data and places the data in it.  If successful,  A  pointer  to
       the buffer is placed in *_buffer.  The caller must free the buffer.

READING KEYRINGS

       This  call  can  be  used to list the contents of a keyring.  The data is presented to the
       user as an array of key_serial_t values, each of which corresponds to a key to  which  the
       keyring holds a link.

       The  size  of  the  keyring will be sizeof(key_serial_t) multiplied by the number of keys.
       The size of key_serial_t is invariant  across  different  word  sizes,  though  the  byte-
       ordering is as appropriate for the kernel.

RETURN VALUE

       On success keyctl_read() returns the amount of data placed into the buffer.  If the buffer
       was too small, then the size of buffer required will be returned,  but  no  data  will  be
       transferred.   On  error, the value -1 will be returned and errno will have been set to an
       appropriate error.

       On success keyctl_read_alloc() returns the amount of data in the buffer.   On  error,  the
       value -1 will be returned and errno will have been set to an appropriate error.

ERRORS

       ENOKEY The key specified is invalid.

       EKEYEXPIRED
              The key specified has expired.

       EKEYREVOKED
              The key specified had been revoked.

       EACCES The key exists, but is not readable by the calling process.

       EOPNOTSUPP
              The key type does not support reading of the payload data.

LINKING

       This  is  a  library  function that can be found in libkeyutils.  When linking, -lkeyutils
       should be specified to the linker.

SEE ALSO

       keyctl(1),
       add_key(2),
       keyctl(2),
       request_key(2),
       keyctl(3),
       request-key(8)