keyctl_read - read a key
#include <keyutils.h>
long keyctl_read(key_serial_t key, char *buffer, size_t buflen);
long keyctl_read_alloc(key_serial_t key, void **_buffer);
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, then the full size of the payload
will be returned, and the contents of the buffer may be overwritten in some
undefined way.
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.
keyctl_read_alloc() adds a NUL character after the data it retrieves,
though this is not counted in the size value it returns.
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.
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, and the contents of the buffer may have been overwritten in some
undefined way.
On success
keyctl_read_alloc() returns the amount of data in the buffer.
On error, both functions set
errno to an appropriate code and return the
value
-1.
- 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- The key specified had been revoked.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.
This is a library function that can be found in
libkeyutils. When
linking,
-lkeyutils should be specified to the linker.
keyctl(1),
add_key(2),
keyctl(2),
request_key(2),
keyctl(3),
keyrings(7),
keyutils(7)