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KEYCTL_READ(3)            Linux Key Management Calls            KEYCTL_READ(3)



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, char **_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  pay-
       load 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  ker-
       nel.

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              The key specified had been revoked.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)



Linux                             4 May 2006                    KEYCTL_READ(3)