keyctl_search man page
keyctl_search — search a keyring for a key
#include <keyutils.h> long keyctl_search(key_serial_t keyring, const char *type, const char *description, key_serial_t destination);
keyctl_search() recursively searches the keyring for a key of the specified type and description.
If found, the key will be attached to the destination keyring (if given), and its serial number will be returned.
The source keyring must grant search permission to the caller, and for a key to be found, it must also grant search permission to the caller. Child keyrings will be only be recursively searched if they grant search permission to the caller as well.
If the destination keyring is zero, no attempt will be made to forge a link to the key, and just the serial number will be returned.
If the destination keyring is given, then the link may only be formed if the found key grants the caller link permission and the destination keyring grants the caller write permission.
If the search is successful, and if the destination keyring already contains a link to a key that matches the specified type and description, then that link will be replaced by a link to the found key.
The source keyring and destination keyring serial numbers may be those of valid keyrings to which the caller has appropriate permission, or they may be special keyring IDs:
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.
On success keyctl_search() returns the serial number of the key it found. On error, the value -1 will be returned and errno will have been set to an appropriate error.
One of the keyrings doesn't exist, no key was found by the search, or the only key found by the search was a negative key.
One of the keyrings is a valid key that isn't a keyring.
One of the keyrings has expired, or the only key found was expired.
One of the keyrings has been revoked, or the only key found was revoked.
Insufficient memory to expand the destination keyring.
The key quota for this user would be exceeded by creating a link to the found key in the destination keyring.
The source keyring didn't grant search permission, the destination keyring didn't grant write permission or the found key didn't grant link permission to the caller.
Although this is a Linux system call, it is not present in libc but can be found rather in libkeyutils. When linking, -lkeyutils should be specified to the linker.
keyctl(1), add_key(2), keyctl(2), request_key(2), keyctl(3), keyrings(7), keyutils(7)
keyctl(2), keyctl(3), keyrings(7).