Section: Linux Key Management Calls (2)
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request_key - Request a key from the kernel's key management facility
key_serial_t request_key(const char *type, const char *description,
const char *callout_info, key_serial_t keyring);
asks the kernel to find a key of the given
that matches the specified
and, if successful, to attach it to the nominated
and to return its serial number.
first recursively searches all the keyrings attached to the calling process in
the order thread-specific keyring, process-specific keyring and then session
keyring for a matching key.
is called from a program invoked by
on behalf of some other process to generate a key, then the keyrings of that
other process will be searched next, using that other process's UID, GID,
groups and security context to control access.
The keys in each keyring searched are checked for a match before any child
keyrings are recursed into. Only keys that are
for the caller may be found, and only
keyrings may be searched.
If the key is not found then, if
is set, this function will attempt to look further afield. In such a case, the
is passed to a userspace service such as
to generate the key.
If that is unsuccessful also, then an error will be returned, and a temporary
negative key will be installed in the nominated
This will expire after a few seconds, but will cause subsequent
to fail until it does.
serial number may be that of a valid keyring to which the caller has write
permission, or it may be a special keyring ID:
This specifies the caller's thread-specific keyring.
This specifies the caller's process-specific keyring.
This specifies the caller's session-specific keyring.
This specifies the caller's UID-specific keyring.
This specifies the caller's UID-session keyring.
If a key is created, no matter whether it's a valid key or a negative key, it
will displace any other key of the same type and description from the
returns the serial number of the key it found.
On error, the value
will be returned and errno will have been set to an appropriate error.
No matching key was found.
An expired key was found, but no replacement could be obtained.
A revoked key was found, but no replacement could be obtained.
The attempt to generate a new key was rejected.
Insufficient memory to create a key.
The request was interrupted by a signal.
The key quota for this user would be exceeded by creating this key or linking
it to the keyring.
The keyring wasn't available for modification by the user.
Although this is a Linux system call, it is not present in
but can be found rather in
should be specified to the linker.
This page is part of release 3.27 of the Linux
A description of the project,
and information about reporting bugs,
can be found at
- RETURN VALUE
- SEE ALSO
This document was created by
using the manual pages.