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.
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
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 success keyctl_read_alloc() returns the amount of data in the
On error, both functions set errno to an appropriate code and return
the value -1.
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The key specified had been revoked.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.
The key type does not support reading of the payload data.
This page is part of the keyutils (key management utilities) project.
Information about the project can be found at [unknown -- if you
know, please contact email@example.com] If you have a bug report for
this manual page, send it to firstname.lastname@example.org. This page was
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Linux 21 Feb 2014 KEYCTL_READ(3)