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ADD_KEY(2)                Linux Key Management CallsADD_KEY(2)NAME       add_key - add a key to the kernel's key management facilitySYNOPSIS       #include <sys/types.h>       #include <keyutils.h>       key_serial_t add_key(const char *type, const char *description,                            const void *payload, size_t plen,                            key_serial_t keyring);       No glibc wrapper is provided for this system call; see NOTES.DESCRIPTION       add_key()  creates  or updates a key of the given type and description,       instantiates it with the payload of length plen,  attaches  it  to  the       nominated keyring, and returns the key's serial number.       The  key may be rejected if the provided data is in the wrong format or       it is invalid in some other way.       If the destination keyring already contains  a  key  that  matches  the       specified type and description, then, if the key type supports it, that       key will be updated rather than a new key being created; if not, a  new       key (with a different ID) will be created and it will displace the link       to the extant key from the keyring.       The destination keyring serial number may be that of  a  valid  keyring       for  which  the  caller has write permission.  Alternatively, it may be       one of the following special keyring IDs:       KEY_SPEC_THREAD_KEYRING              This specifies the  caller's  thread-specific  keyring  (thread-keyring(7)).       KEY_SPEC_PROCESS_KEYRING              This  specifies  the caller's process-specific keyring (process-keyring(7)).       KEY_SPEC_SESSION_KEYRING              This specifies the caller's session-specific  keyring  (session-keyring(7)).       KEY_SPEC_USER_KEYRING              This   specifies   the   caller's  UID-specific  keyring  (user-keyring(7)).       KEY_SPEC_USER_SESSION_KEYRING              This specifies the caller's UID-session  keyring  (user-session-keyring(7)).   Key types       The  key  type  is a string that specifies the key's type.  Internally,       the kernel defines a number of key types that are available in the core       key management code.  Among the types that are available for user-space       use and can be specified as the type argument to add_key() are the fol-       lowing:       "keyring"              Keyrings  are  special  key  types that may contain links to se-              quences of other keys of any type.  If this interface is used to              create a keyring, then payload should be NULL and plen should be              zero.       "user" This is a general purpose key type whose payload may be read and              updated  by  user-space  applications.  The key is kept entirely              within kernel memory.  The payload for keys of this  type  is  a              blob of arbitrary data of up to 32,767 bytes.       "logon" (since Linux 3.3)              This key type is essentially the same as "user", but it does not              permit the key to read.  This is suitable for  storing  payloads              that you do not want to be readable from user space.       This  key type vets the description to ensure that it is qualified by a       "service" prefix, by checking to ensure that the description contains a       ':' that is preceded by other characters.       "big_key" (since Linux 3.13)              This key type is similar to "user", but may hold a payload of up              to 1 MiB.  If the key payload is large enough, then  it  may  be              stored encrypted in tmpfs (which can be swapped out) rather than              kernel memory.       For further details on these key types, seekeyrings(7).RETURN VALUE       On success, add_key() returns the serial number of the key  it  created       or  updated.  On error, -1 is returned and errno is set to indicate the       cause of the error.ERRORS       EACCES The keyring wasn't available for modification by the user.       EDQUOT The key quota for this user would be exceeded by  creating  this              key or linking it to the keyring.       EFAULT One  or  more  of  type, description, and payload points outside              process's accessible address space.       EINVAL The size of the string (including  the  terminating  null  byte)              specified  in  type  or description exceeded the limit (32 bytes              and 4096 bytes respectively).       EINVAL The payload data was invalid.       EINVAL type was "logon" and the description was not  qualified  with  a              prefix string of the form "service:".       EKEYEXPIRED              The keyring has expired.       EKEYREVOKED              The keyring has been revoked.       ENOKEY The keyring doesn't exist.       ENOMEM Insufficient memory to create a key.       EPERM  The type started with a period ('.').  Key types that begin with              a period are reserved to the implementation.       EPERM  type was "keyring" and the description  started  with  a  period              ('.').  Keyrings with descriptions (names) that begin with a pe-              riod are reserved to the implementation.VERSIONS       This system call first appeared in Linux 2.6.10.CONFORMING TO       This system call is a nonstandard Linux extension.NOTES       No wrapper for this system call is provided in  glibc.   A  wrapper  is       provided  in  the  libkeyutils  package.  When employing the wrapper in       that library, link with -lkeyutils.EXAMPLE       The program below creates a key with the type, description, and payload       specified  in  its  command-line arguments, and links that key into the       session keyring.  The following shell session demonstrates the  use  of       the program:           $ ./a.out user mykey "Some payload"           Key ID is 64a4dca           $ grep '64a4dca' /proc/keys           064a4dca I--Q---    1 perm 3f010000  1000  1000 user    mykey: 12   Program source       #include <sys/types.h>       #include <keyutils.h>       #include <stdio.h>       #include <stdlib.h>       #include <string.h>       int       main(int argc, char *argv[])       {           key_serial_t key;           if (argc != 4) {               fprintf(stderr, "Usage: %s type description payload\n",                       argv[0]);               exit(EXIT_FAILURE);           }           key = add_key(argv[1], argv[2], argv[3], strlen(argv[3]),                       KEY_SPEC_SESSION_KEYRING);           if (key == -1) {               perror("add_key");               exit(EXIT_FAILURE);           }           printf("Key ID is %lx\n", (long) key);           exit(EXIT_SUCCESS);       }SEE ALSOkeyctl(1),keyctl(2),request_key(2),keyctl(3),keyrings(7),keyutils(7),persistent-keyring(7),process-keyring(7),session-keyring(7),thread-keyring(7),user-keyring(7),user-session-keyring(7)       The kernel source files Documentation/security/keys/core.rst and       Documentation/keys/request-key.rst (or, before Linux 4.13, in the files       Documentation/security/keys.txt and       Documentation/security/keys-request-key.txt).COLOPHON       This page is part of release 5.05 of the Linux man-pages project.  A       description of the project, information about reporting bugs, and the       latest version of this page, can be found at       https://www.kernel.org/doc/man-pages/.Linux                             2019-03-06ADD_KEY(2)