linux/arch/avr32
David Howells ee18d64c1f KEYS: Add a keyctl to install a process's session keyring on its parent [try #6]
Add a keyctl to install a process's session keyring onto its parent.  This
replaces the parent's session keyring.  Because the COW credential code does
not permit one process to change another process's credentials directly, the
change is deferred until userspace next starts executing again.  Normally this
will be after a wait*() syscall.

To support this, three new security hooks have been provided:
cred_alloc_blank() to allocate unset security creds, cred_transfer() to fill in
the blank security creds and key_session_to_parent() - which asks the LSM if
the process may replace its parent's session keyring.

The replacement may only happen if the process has the same ownership details
as its parent, and the process has LINK permission on the session keyring, and
the session keyring is owned by the process, and the LSM permits it.

Note that this requires alteration to each architecture's notify_resume path.
This has been done for all arches barring blackfin, m68k* and xtensa, all of
which need assembly alteration to support TIF_NOTIFY_RESUME.  This allows the
replacement to be performed at the point the parent process resumes userspace
execution.

This allows the userspace AFS pioctl emulation to fully emulate newpag() and
the VIOCSETTOK and VIOCSETTOK2 pioctls, all of which require the ability to
alter the parent process's PAG membership.  However, since kAFS doesn't use
PAGs per se, but rather dumps the keys into the session keyring, the session
keyring of the parent must be replaced if, for example, VIOCSETTOK is passed
the newpag flag.

This can be tested with the following program:

	#include <stdio.h>
	#include <stdlib.h>
	#include <keyutils.h>

	#define KEYCTL_SESSION_TO_PARENT	18

	#define OSERROR(X, S) do { if ((long)(X) == -1) { perror(S); exit(1); } } while(0)

	int main(int argc, char **argv)
	{
		key_serial_t keyring, key;
		long ret;

		keyring = keyctl_join_session_keyring(argv[1]);
		OSERROR(keyring, "keyctl_join_session_keyring");

		key = add_key("user", "a", "b", 1, keyring);
		OSERROR(key, "add_key");

		ret = keyctl(KEYCTL_SESSION_TO_PARENT);
		OSERROR(ret, "KEYCTL_SESSION_TO_PARENT");

		return 0;
	}

Compiled and linked with -lkeyutils, you should see something like:

	[dhowells@andromeda ~]$ keyctl show
	Session Keyring
	       -3 --alswrv   4043  4043  keyring: _ses
	355907932 --alswrv   4043    -1   \_ keyring: _uid.4043
	[dhowells@andromeda ~]$ /tmp/newpag
	[dhowells@andromeda ~]$ keyctl show
	Session Keyring
	       -3 --alswrv   4043  4043  keyring: _ses
	1055658746 --alswrv   4043  4043   \_ user: a
	[dhowells@andromeda ~]$ /tmp/newpag hello
	[dhowells@andromeda ~]$ keyctl show
	Session Keyring
	       -3 --alswrv   4043  4043  keyring: hello
	340417692 --alswrv   4043  4043   \_ user: a

Where the test program creates a new session keyring, sticks a user key named
'a' into it and then installs it on its parent.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
2009-09-02 21:29:22 +10:00
..
boards Merge branch 'avr32-arch' of git://git.kernel.org/pub/scm/linux/kernel/git/hskinnemoen/avr32-2.6 2009-06-13 15:34:22 +02:00
boot avr32: remove .note.gnu.build-id section when making vmlinux.bin 2008-12-17 11:44:10 +01:00
configs avr32: Add support for Mediama RMTx add-on board for ATNGW100 2009-06-08 12:55:35 +02:00
include/asm KEYS: Extend TIF_NOTIFY_RESUME to (almost) all architectures [try #6] 2009-09-02 21:29:19 +10:00
kernel KEYS: Add a keyctl to install a process's session keyring on its parent [try #6] 2009-09-02 21:29:22 +10:00
lib avr32: Fix out-of-range rcalls in large kernels 2009-01-16 09:31:57 +01:00
mach-at32ap avr32: Fix clash in ATMEL_USART_ flags 2009-06-03 11:38:20 +02:00
mm Move FAULT_FLAG_xyz into handle_mm_fault() callers 2009-06-21 13:08:22 -07:00
oprofile Add kernel support for oprofile callgraphs on AVR32 2008-09-22 09:51:01 +02:00
Kconfig Merge branch 'avr32-arch' of git://git.kernel.org/pub/scm/linux/kernel/git/hskinnemoen/avr32-2.6 2009-04-05 11:15:28 -07:00
Kconfig.debug [AVR32] Include instrumentation menu 2008-01-25 08:31:40 +01:00
Makefile avr32: drop unused CLEAN_FILES 2009-05-01 10:54:00 +02:00