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The key specified had been revoked.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.
