posix man page for keyctl_read

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 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  dif-
       ferent 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	      The key specified had been revoked.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_get_keyring_ID(3),
       keyctl_join_session_keyring(3),
       keyctl_update(3),
       keyctl_revoke(3),
       keyctl_chown(3),
       keyctl_setperm(3),
       keyctl_describe(3),
       keyctl_clear(3),
       keyctl_link(3),
       keyctl_unlink(3),
       keyctl_search(3),
       keyctl_instantiate(3),
       keyctl_negate(3),
       keyctl_set_reqkey_keyring(3),
       keyctl_set_timeout(3),
       keyctl_assume_authority(3),
       keyctl_describe_alloc(3),
       request-key(8)

Linux								    4 May 2006							    KEYCTL_READ(3)