|author||David Howells <firstname.lastname@example.org>||2013-09-24 10:35:19 +0100|
|committer||David Howells <email@example.com>||2013-09-24 10:35:19 +0100|
|parent||KEYS: Implement a big key type that can save to tmpfs (diff)|
KEYS: Add per-user_namespace registers for persistent per-UID kerberos caches
Add support for per-user_namespace registers of persistent per-UID kerberos caches held within the kernel. This allows the kerberos cache to be retained beyond the life of all a user's processes so that the user's cron jobs can work. The kerberos cache is envisioned as a keyring/key tree looking something like: struct user_namespace \___ .krb_cache keyring - The register \___ _krb.0 keyring - Root's Kerberos cache \___ _krb.5000 keyring - User 5000's Kerberos cache \___ _krb.5001 keyring - User 5001's Kerberos cache \___ tkt785 big_key - A ccache blob \___ tkt12345 big_key - Another ccache blob Or possibly: struct user_namespace \___ .krb_cache keyring - The register \___ _krb.0 keyring - Root's Kerberos cache \___ _krb.5000 keyring - User 5000's Kerberos cache \___ _krb.5001 keyring - User 5001's Kerberos cache \___ tkt785 keyring - A ccache \___ krbtgt/REDHAT.COM@REDHAT.COM big_key \___ http/REDHAT.COM@REDHAT.COM user \___ afs/REDHAT.COM@REDHAT.COM user \___ nfs/REDHAT.COM@REDHAT.COM user \___ krbtgt/KERNEL.ORG@KERNEL.ORG big_key \___ http/KERNEL.ORG@KERNEL.ORG big_key What goes into a particular Kerberos cache is entirely up to userspace. Kernel support is limited to giving you the Kerberos cache keyring that you want. The user asks for their Kerberos cache by: krb_cache = keyctl_get_krbcache(uid, dest_keyring); The uid is -1 or the user's own UID for the user's own cache or the uid of some other user's cache (requires CAP_SETUID). This permits rpc.gssd or whatever to mess with the cache. The cache returned is a keyring named "_krb.<uid>" that the possessor can read, search, clear, invalidate, unlink from and add links to. Active LSMs get a chance to rule on whether the caller is permitted to make a link. Each uid's cache keyring is created when it first accessed and is given a timeout that is extended each time this function is called so that the keyring goes away after a while. The timeout is configurable by sysctl but defaults to three days. Each user_namespace struct gets a lazily-created keyring that serves as the register. The cache keyrings are added to it. This means that standard key search and garbage collection facilities are available. The user_namespace struct's register goes away when it does and anything left in it is then automatically gc'd. Signed-off-by: David Howells <firstname.lastname@example.org> Tested-by: Simo Sorce <email@example.com> cc: Serge E. Hallyn <firstname.lastname@example.org> cc: Eric W. Biederman <email@example.com>
Diffstat (limited to 'security/keys/Kconfig')
1 files changed, 17 insertions, 0 deletions
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index b56362275ec8..53d8748c9564 100644
@@ -20,6 +20,23 @@ config KEYS
If you are unsure as to whether this is required, answer N.
+ bool "Enable register of persistent per-UID keyrings"
+ depends on KEYS
+ This option provides a register of persistent per-UID keyrings,
+ primarily aimed at Kerberos key storage. The keyrings are persistent
+ in the sense that they stay around after all processes of that UID
+ have exited, not that they survive the machine being rebooted.
+ A particular keyring may be accessed by either the user whose keyring
+ it is or by a process with administrative privileges. The active
+ LSMs gets to rule on which admin-level processes get to access the
+ Keyrings are created and added into the register upon demand and get
+ removed if they expire (a default timeout is set upon creation).
tristate "Large payload keys"
depends on KEYS