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_t buflen);
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, then the full size of the pay-
load will be returned, and the contents of the buffer may be overwrit-
ten in some undefined way.
keyctl_read_alloc() is similar to keyctl_read() except that it allo-
cates 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.
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, and the contents of the buffer may have been over-
written in some undefined way.
On success keyctl_read_alloc() returns the amount of data in the buf-
fer.
On error, both functions set errno to an appropriate code and return
the value -1.
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The key specified had been revoked.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),
keyrings(7), keyutils(7)
Linux 21 Feb 2014 KEYCTL_READ(3)
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