linux/security
David Howells 0b0a84154e KEYS: request_key() should reget expired keys rather than give EKEYEXPIRED
Since the keyring facility can be viewed as a cache (at least in some
applications), the local expiration time on the key should probably be viewed
as a 'needs updating after this time' property rather than an absolute 'anyone
now wanting to use this object is out of luck' property.

Since request_key() is the main interface for the usage of keys, this should
update or replace an expired key rather than issuing EKEYEXPIRED if the local
expiration has been reached (ie. it should refresh the cache).

For absolute conditions where refreshing the cache probably doesn't help, the
key can be negatively instantiated using KEYCTL_REJECT_KEY with EKEYEXPIRED
given as the error to issue.  This will still cause request_key() to return
EKEYEXPIRED as that was explicitly set.

In the future, if the key type has an update op available, we might want to
upcall with the expired key and allow the upcall to update it.  We would pass
a different operation name (the first column in /etc/request-key.conf) to the
request-key program.

request_key() returning EKEYEXPIRED is causing an NFS problem which Chuck
Lever describes thusly:

	After about 10 minutes, my NFSv4 functional tests fail because the
	ownership of the test files goes to "-2". Looking at /proc/keys
	shows that the id_resolv keys that map to my test user ID have
	expired. The ownership problem persists until the expired keys are
	purged from the keyring, and fresh keys are obtained.

	I bisected the problem to 3.13 commit b2a4df200d ("KEYS: Expand
	the capacity of a keyring"). This commit inadvertantly changes the
	API contract of the internal function keyring_search_aux().

	The root cause appears to be that b2a4df200d made "no state check"
	the default behavior. "No state check" means the keyring search
	iterator function skips checking the key's expiry timeout, and
	returns expired keys.  request_key_and_link() depends on getting
	an -EAGAIN result code to know when to perform an upcall to refresh
	an expired key.

This patch can be tested directly by:

	keyctl request2 user debug:fred a @s
	keyctl timeout %user:debug:fred 3
	sleep 4
	keyctl request2 user debug:fred a @s

Without the patch, the last command gives error EKEYEXPIRED, but with the
command it gives a new key.

Reported-by: Carl Hetherington <cth@carlh.net>
Reported-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Chuck Lever <chuck.lever@oracle.com>
2014-12-01 22:52:53 +00:00
..
apparmor module: rename KERNEL_PARAM_FL_NOARG to avoid confusion 2014-08-27 21:54:07 +09:30
integrity Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity into for-linus 2014-10-29 15:03:54 +11:00
keys KEYS: request_key() should reget expired keys rather than give EKEYEXPIRED 2014-12-01 22:52:53 +00:00
selinux Merge branch 'stable-3.18' of git://git.infradead.org/users/pcmoore/selinux into for-linus 2014-11-13 21:49:53 +11:00
smack Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2014-10-12 10:13:55 -04:00
tomoyo tomoyo: Fix pathname calculation breakage. 2014-08-26 21:52:09 -05:00
yama yama: Better permission check for ptraceme 2013-03-26 13:17:58 -07:00
Kconfig security: select correct default LSM_MMAP_MIN_ADDR on arm on arm64 2014-02-05 14:59:14 +00:00
Makefile security: cleanup Makefiles to use standard syntax for specifying sub-directories 2014-02-17 11:08:04 +11:00
capability.c security: make security_file_set_fowner, f_setown and __f_setown void return 2014-09-09 16:01:36 -04:00
commoncap.c CAPABILITIES: remove undefined caps from all processes 2014-07-24 21:53:47 +10:00
device_cgroup.c cgroup: rename cgroup_subsys->base_cftypes to ->legacy_cftypes 2014-07-15 11:05:09 -04:00
inode.c Documentation: Docbook: Fix generated DocBook/kernel-api.xml 2014-09-09 10:34:56 +02:00
lsm_audit.c audit: anchor all pid references in the initial pid namespace 2014-03-20 10:11:55 -04:00
min_addr.c mmap_min_addr check CAP_SYS_RAWIO only for write 2010-04-23 08:56:31 +10:00
security.c security: make security_file_set_fowner, f_setown and __f_setown void return 2014-09-09 16:01:36 -04:00