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long keyctl_read(key_serial_t key, char *buffer,
long keyctl_read_alloc(key_serial_t key, char **_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, 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 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.
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, but no data will be transferred. On error, the value
-1 will be returned and errno will have been set to an appropriate
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.
ENOKEY The key specified is invalid.
The key specified has expired.
The key specified had been revoked.
EACCES The key exists, but is not readable by the calling process.
Linux 4 May 2006 KEYCTL_READ(3)