.\" Copyright (C) 2006 Red Hat, Inc. All Rights Reserved. .\" Written by David Howells (dhowells@redhat.com) .\" and Copyright (C) 2016 Michael Kerrisk .\" .\" %%%LICENSE_START(GPLv2+_SW_ONEPARA) .\" This program is free software; you can redistribute it and/or .\" modify it under the terms of the GNU General Public License .\" as published by the Free Software Foundation; either version .\" 2 of the License, or (at your option) any later version. .\" %%%LICENSE_END .\" .TH ADD_KEY 2 2019-03-06 Linux "Linux Key Management Calls" .SH NAME add_key \- add a key to the kernel's key management facility .SH SYNOPSIS .nf .B #include .B #include .PP .BI "key_serial_t add_key(const char *" type ", const char *" description , .BI " const void *" payload ", size_t " plen , .BI " key_serial_t " keyring ");" .fi .PP No glibc wrapper is provided for this system call; see NOTES. .SH DESCRIPTION .BR add_key () creates or updates a key of the given .I type and .IR description , instantiates it with the .I payload of length .IR plen , attaches it to the nominated .IR keyring , and returns the key's serial number. .PP The key may be rejected if the provided data is in the wrong format or it is invalid in some other way. .PP If the destination .I keyring already contains a key that matches the specified .IR type and .IR description , then, if the key type supports it, .\" FIXME The aforementioned phrases begs the question: .\" which key types support this? 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. .\" FIXME Perhaps elaborate the implications here? Namely, the new .\" key will have a new ID, and if the old key was a keyring that .\" is consequently unlinked, then keys that it was anchoring .\" will have their reference count decreased by one (and may .\" consequently be garbage collected). Is this all correct? .PP The destination .I keyring serial number may be that of a valid keyring for which the caller has .I write permission. Alternatively, it may be one of the following special keyring IDs: .\" FIXME . Perhaps have a separate page describing special keyring IDs? .TP .B KEY_SPEC_THREAD_KEYRING This specifies the caller's thread-specific keyring .RB ( thread-keyring (7)). .TP .B KEY_SPEC_PROCESS_KEYRING This specifies the caller's process-specific keyring .RB ( process-keyring (7)). .TP .B KEY_SPEC_SESSION_KEYRING This specifies the caller's session-specific keyring .RB ( session-keyring (7)). .TP .B KEY_SPEC_USER_KEYRING This specifies the caller's UID-specific keyring .RB ( user-keyring (7)). .TP .B KEY_SPEC_USER_SESSION_KEYRING This specifies the caller's UID-session keyring .RB ( user-session-keyring (7)). .SS Key types The key .I 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 .I type argument to .BR add_key () are the following: .TP .I """keyring""" Keyrings are special key types that may contain links to sequences of other keys of any type. If this interface is used to create a keyring, then .I payload should be NULL and .I plen should be zero. .TP .IR """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. .TP .IR """logon""" " (since Linux 3.3)" .\" commit 9f6ed2ca257fa8650b876377833e6f14e272848b This key type is essentially the same as .IR """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. .PP This key type vets the .I description to ensure that it is qualified by a "service" prefix, by checking to ensure that the .I description contains a ':' that is preceded by other characters. .TP .IR """big_key""" " (since Linux 3.13)" .\" commit ab3c3587f8cda9083209a61dbe3a4407d3cada10 This key type is similar to .IR """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. .PP For further details on these key types, see .BR keyrings (7). .SH RETURN VALUE On success, .BR add_key () returns the serial number of the key it created or updated. On error, \-1 is returned and .I errno is set to indicate the cause of the error. .SH ERRORS .TP .B EACCES The keyring wasn't available for modification by the user. .TP .B EDQUOT The key quota for this user would be exceeded by creating this key or linking it to the keyring. .TP .B EFAULT One or more of .IR type , .IR description , and .I payload points outside process's accessible address space. .TP .B EINVAL The size of the string (including the terminating null byte) specified in .I type or .I description exceeded the limit (32 bytes and 4096 bytes respectively). .TP .B EINVAL The payload data was invalid. .TP .B EINVAL .IR type was .IR """logon""" and the .I description was not qualified with a prefix string of the form .IR """service:""" . .TP .B EKEYEXPIRED The keyring has expired. .TP .B EKEYREVOKED The keyring has been revoked. .TP .B ENOKEY The keyring doesn't exist. .TP .B ENOMEM Insufficient memory to create a key. .TP .B EPERM The .I type started with a period (\(aq.\(aq). Key types that begin with a period are reserved to the implementation. .TP .B EPERM .I type was .I """keyring""" and the .I description started with a period (\(aq.\(aq). Keyrings with descriptions (names) that begin with a period are reserved to the implementation. .SH VERSIONS This system call first appeared in Linux 2.6.10. .SH CONFORMING TO This system call is a nonstandard Linux extension. .SH NOTES No wrapper for this system call is provided in glibc. A wrapper is provided in the .IR libkeyutils package. When employing the wrapper in that library, link with .IR \-lkeyutils . .SH 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: .PP .in +4n .EX $ \fB./a.out user mykey "Some payload"\fP Key ID is 64a4dca $ \fBgrep \(aq64a4dca\(aq /proc/keys\fP 064a4dca I--Q--- 1 perm 3f010000 1000 1000 user mykey: 12 .EE .in .SS Program source \& .EX #include #include #include #include #include int main(int argc, char *argv[]) { key_serial_t key; if (argc != 4) { fprintf(stderr, "Usage: %s type description payload\en", 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\en", (long) key); exit(EXIT_SUCCESS); } .EE .SH SEE ALSO .ad l .nh .BR keyctl (1), .BR keyctl (2), .BR request_key (2), .BR keyctl (3), .BR keyrings (7), .BR keyutils (7), .BR persistent\-keyring (7), .BR process\-keyring (7), .BR session\-keyring (7), .BR thread\-keyring (7), .BR user\-keyring (7), .BR user\-session\-keyring (7) .PP The kernel source files .IR Documentation/security/keys/core.rst and .IR Documentation/keys/request\-key.rst (or, before Linux 4.13, in the files .\" commit b68101a1e8f0263dbc7b8375d2a7c57c6216fb76 .IR Documentation/security/keys.txt and .\" commit 3db38ed76890565772fcca3279cc8d454ea6176b .IR Documentation/security/keys\-request\-key.txt ). .SH COLOPHON This page is part of release 5.04 of the Linux .I 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/.