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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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KEYCTL_READ(2const) KEYCTL_READ(2const)
KEYCTL_READ - read a key
Standard C library (libc, -lc)
#include <linux/keyctl.h> /* Definition of KEY* constants */
#include <sys/syscall.h> /* Definition of SYS_* constants */
#include <unistd.h>
long syscall(SYS_keyctl, KEYCTL_READ, key_serial_t key,
char buf[_Nullable .size], size_t size);
Read the payload data of a key.
The ID of the key whose payload is to be read is specified in key.
This can be the ID of an existing key, or any of the special key
IDs listed for KEYCTL_GET_KEYRING_ID(2const).
The payload is placed in the buffer pointed by buf; the size of
that buffer must be specified in size.
The returned data will be processed for presentation according to
the key type. For example, a keyring will return an array of
key_serial_t entries representing the IDs of all the keys that are
linked to it. The user key type will return its data as is.
If buf is not NULL, as much of the payload data as will fit is
copied into the buffer. On a successful return, the return value
is always the total size of the payload data. To determine
whether the buffer was of sufficient size, check to see that the
return value is less than or equal to the value supplied in size.
The key must either grant the caller read permission, or grant the
caller search permission when searched for from the process
keyrings (i.e., the key is possessed).
On success, the amount of data that is available in the key,
irrespective of the provided buffer size.
On error, -1 is returned, and errno is set to indicate the error.
EOPNOTSUPP
The key type does not support reading (e.g., the type is
"login").
A wrapper is provided in the libkeyutils library: keyctl_read(3).
Linux.
Linux 2.6.10.
keyctl(2), keyctl_read(3), keyctl_read_alloc(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.10.tar.gz
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⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-02-02. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.10 2024-08-21 KEYCTL_READ(2const)
Pages that refer to this page: keyctl(2), KEYCTL_ASSUME_AUTHORITY(2const), KEYCTL_SETPERM(2const)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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