keyctl_read(3) — Linux manual page

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 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.

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 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.

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              The key specified had been revoked.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)

COLOPHON

       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 man-pages@man7.org] If you have a
       bug report for this manual page, send it to
       keyrings@linux-nfs.org.  This page was obtained from the
       project's upstream Git repository
       ⟨http://git.kernel.org/pub/scm/linux/kernel/git/dhowells/keyutils.git⟩
       on 2024-06-14.  (At that time, the date of the most recent commit
       that was found in the repository was 2023-03-20.)  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                          21 Feb 2014                KEYCTL_READ(3)

Pages that refer to this page: keyctl(2), request_key(2), keyctl(3)

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