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commit 0da9dfdd2cd9889201bc6f6f43580c99165cd087 upstream.
This fixes CVE-2013-1792.
There is a race in install_user_keyrings() that can cause a NULL pointer
dereference when called concurrently for the same user if the uid and
uid-session keyrings are not yet created. It might be possible for an
unprivileged user to trigger this by calling keyctl() from userspace in
parallel immediately after logging in.
Assume that we have two threads both executing lookup_user_key(), both
looking for KEY_SPEC_USER_SESSION_KEYRING.
THREAD A THREAD B
=============================== ===============================
==>call install_user_keyrings();
if (!cred->user->session_keyring)
==>call install_user_keyrings()
...
user->uid_keyring = uid_keyring;
if (user->uid_keyring)
return 0;
<==
key = cred->user->session_keyring [== NULL]
user->session_keyring = session_keyring;
atomic_inc(&key->usage); [oops]
At the point thread A dereferences cred->user->session_keyring, thread B
hasn't updated user->session_keyring yet, but thread A assumes it is
populated because install_user_keyrings() returned ok.
The race window is really small but can be exploited if, for example,
thread B is interrupted or preempted after initializing uid_keyring, but
before doing setting session_keyring.
This couldn't be reproduced on a stock kernel. However, after placing
systemtap probe on 'user->session_keyring = session_keyring;' that
introduced some delay, the kernel could be crashed reliably.
Fix this by checking both pointers before deciding whether to return.
Alternatively, the test could be done away with entirely as it is checked
inside the mutex - but since the mutex is global, that may not be the best
way.
Signed-off-by: David Howells <dhowells@redhat.com>
Reported-by: Mateusz Guzik <mguzik@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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The test for "if (cred->request_key_auth->flags & KEY_FLAG_REVOKED) {"
should actually testing that the (1 << KEY_FLAG_REVOKED) bit is set.
The current code actually checks for KEY_FLAG_DEAD.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
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The keyctl call:
keyctl_get_keyring_ID(KEY_SPEC_SESSION_KEYRING, 1)
should create a session keyring if the process doesn't have one of its own
because the create flag argument is set - rather than subscribing to and
returning the user-session keyring as:
keyctl_get_keyring_ID(KEY_SPEC_SESSION_KEYRING, 0)
will do.
This can be tested by commenting out pam_keyinit in the /etc/pam.d files and
running the following program a couple of times in a row:
#include <stdio.h>
#include <stdlib.h>
#include <keyutils.h>
int main(int argc, char *argv[])
{
key_serial_t uk, usk, sk, nsk;
uk = keyctl_get_keyring_ID(KEY_SPEC_USER_KEYRING, 0);
usk = keyctl_get_keyring_ID(KEY_SPEC_USER_SESSION_KEYRING, 0);
sk = keyctl_get_keyring_ID(KEY_SPEC_SESSION_KEYRING, 0);
nsk = keyctl_get_keyring_ID(KEY_SPEC_SESSION_KEYRING, 1);
printf("keys: %08x %08x %08x %08x\n", uk, usk, sk, nsk);
return 0;
}
Without this patch, I see:
keys: 3975ddc7 119c0c66 119c0c66 119c0c66
keys: 3975ddc7 119c0c66 119c0c66 119c0c66
With this patch, I see:
keys: 2cb4997b 34112878 34112878 17db2ce3
keys: 2cb4997b 34112878 34112878 39f3c73e
As can be seen, the session keyring starts off the same as the user-session
keyring each time, but with the patch a new session keyring is created when
the create flag is set.
Reported-by: Greg Wettstein <greg@enjellic.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Greg Wettstein <greg@enjellic.com>
Signed-off-by: James Morris <jmorris@namei.org>
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If install_session_keyring() is given a keyring, it should install it rather
than just creating a new one anyway. This was accidentally broken in:
commit d84f4f992cbd76e8f39c488cf0c5d123843923b1
Author: David Howells <dhowells@redhat.com>
Date: Fri Nov 14 10:39:23 2008 +1100
Subject: CRED: Inaugurate COW credentials
The impact of that commit is that pam_keyinit no longer works correctly if
'force' isn't specified against a login process. This is because:
keyctl_get_keyring_ID(KEY_SPEC_SESSION_KEYRING, 0)
now always creates a new session keyring and thus the check whether the session
keyring and the user-session keyring are the same is always false. This leads
pam_keyinit to conclude that a session keyring is installed and it shouldn't be
revoked by pam_keyinit here if 'revoke' is specified.
Any system that specifies 'force' against pam_keyinit in the PAM configuration
files for login methods (login, ssh, su -l, kdm, etc.) is not affected since
that bypasses the broken check and forces the creation of a new session keyring
anyway (for which the revoke flag is not cleared) - and any subsequent call to
pam_keyinit really does have a session keyring already installed, and so the
check works correctly there.
Reverting to the previous behaviour will cause the kernel to subscribe the
process to the user-session keyring as its session keyring if it doesn't have a
session keyring of its own. pam_keyinit will detect this and install a new
session keyring anyway (and won't clear the revert flag).
This can be tested by commenting out pam_keyinit in the /etc/pam.d files and
running the following program a couple of times in a row:
#include <stdio.h>
#include <stdlib.h>
#include <keyutils.h>
int main(int argc, char *argv[])
{
key_serial_t uk, usk, sk;
uk = keyctl_get_keyring_ID(KEY_SPEC_USER_KEYRING, 0);
usk = keyctl_get_keyring_ID(KEY_SPEC_USER_SESSION_KEYRING, 0);
sk = keyctl_get_keyring_ID(KEY_SPEC_SESSION_KEYRING, 0);
printf("keys: %08x %08x %08x\n", uk, usk, sk);
return 0;
}
Without the patch, I see:
keys: 3884e281 24c4dfcf 22825f8e
keys: 3884e281 24c4dfcf 068772be
With the patch, I see:
keys: 26be9c83 0e755ce0 0e755ce0
keys: 26be9c83 0e755ce0 0e755ce0
As can be seen, with the patch, the session keyring is the same as the
user-session keyring each time; without the patch a new session keyring is
generated each time.
Reported-by: Greg Wettstein <greg@enjellic.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Greg Wettstein <greg@enjellic.com>
Signed-off-by: James Morris <jmorris@namei.org>
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Since this cred was not created with copy_creds(), it needs to get
initialized. Otherwise use of syscall(__NR_keyctl, KEYCTL_SESSION_TO_PARENT);
can lead to a NULL deref. Thanks to Robert for finding this.
But introduced by commit 47a150edc2a ("Cache user_ns in struct cred").
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Reported-by: Robert Święcki <robert@swiecki.net>
Cc: David Howells <dhowells@redhat.com>
Cc: stable@kernel.org (2.6.39)
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Improve /proc/keys by:
(1) Don't attempt to summarise the payload of a negated key. It won't have
one. To this end, a helper function - key_is_instantiated() has been
added that allows the caller to find out whether the key is positively
instantiated (as opposed to being uninstantiated or negatively
instantiated).
(2) Do show keys that are negative, expired or revoked rather than hiding
them. This requires an override flag (no_state_check) to be passed to
search_my_process_keyrings() and keyring_search_aux() to suppress this
check.
Without this, keys that are possessed by the caller, but only grant
permissions to the caller if possessed are skipped as the possession check
fails.
Keys that are visible due to user, group or other checks are visible with
or without this patch.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
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Fix up comments in the key management code. No functional changes.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Do a bit of a style clean up in the key management code. No functional
changes.
Done using:
perl -p -i -e 's!^/[*]*/\n!!' security/keys/*.c
perl -p -i -e 's!} /[*] end [a-z0-9_]*[(][)] [*]/\n!}\n!' security/keys/*.c
sed -i -s -e ": next" -e N -e 's/^\n[}]$/}/' -e t -e P -e 's/^.*\n//' -e "b next" security/keys/*.c
To remove /*****/ lines, remove comments on the closing brace of a
function to name the function and remove blank lines before the closing
brace of a function.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Fix an incorrect error check that returns 1 for error instead of the
expected error code.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Make /proc/keys check to see if the calling process possesses each key before
performing the security check. The possession check can be skipped if the key
doesn't have the possessor-view permission bit set.
This causes the keys a process possesses to show up in /proc/keys, even if they
don't have matching user/group/other view permissions.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
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call_usermodehelper_keys() uses call_usermodehelper_setkeys() to change
subprocess_info->cred in advance. Now that we have info->init() we can
change this code to set tgcred->session_keyring in context of execing
kernel thread.
Note: since currently call_usermodehelper_keys() is never called with
UMH_NO_WAIT, call_usermodehelper_keys()->key_get() and umh_keys_cleanup()
are not really needed, we could rely on install_session_keyring_to_cred()
which does key_get() on success.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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We were using the wrong variable here so the error codes weren't being returned
properly. The original code returns -ENOKEY.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
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implicit slab.h inclusion from percpu.h
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files. percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.
percpu.h -> slab.h dependency is about to be removed. Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability. As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.
http://userweb.kernel.org/~tj/misc/slabh-sweep.py
The script does the followings.
* Scan files for gfp and slab usages and update includes such that
only the necessary includes are there. ie. if only gfp is used,
gfp.h, if slab is used, slab.h.
* When the script inserts a new include, it looks at the include
blocks and try to put the new include such that its order conforms
to its surrounding. It's put in the include block which contains
core kernel includes, in the same order that the rest are ordered -
alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
doesn't seem to be any matching order.
* If the script can't find a place to put a new include (mostly
because the file doesn't have fitting include block), it prints out
an error message indicating which .h file needs to be added to the
file.
The conversion was done in the following steps.
1. The initial automatic conversion of all .c files updated slightly
over 4000 files, deleting around 700 includes and adding ~480 gfp.h
and ~3000 slab.h inclusions. The script emitted errors for ~400
files.
2. Each error was manually checked. Some didn't need the inclusion,
some needed manual addition while adding it to implementation .h or
embedding .c file was more appropriate for others. This step added
inclusions to around 150 files.
3. The script was run again and the output was compared to the edits
from #2 to make sure no file was left behind.
4. Several build tests were done and a couple of problems were fixed.
e.g. lib/decompress_*.c used malloc/free() wrappers around slab
APIs requiring slab.h to be added manually.
5. The script was run on all .h files but without automatically
editing them as sprinkling gfp.h and slab.h inclusions around .h
files could easily lead to inclusion dependency hell. Most gfp.h
inclusion directives were ignored as stuff from gfp.h was usually
wildly available and often used in preprocessor macros. Each
slab.h inclusion directive was examined and added manually as
necessary.
6. percpu.h was updated not to include slab.h.
7. Build test were done on the following configurations and failures
were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my
distributed build env didn't work with gcov compiles) and a few
more options had to be turned off depending on archs to make things
build (like ipr on powerpc/64 which failed due to missing writeq).
* x86 and x86_64 UP and SMP allmodconfig and a custom test config.
* powerpc and powerpc64 SMP allmodconfig
* sparc and sparc64 SMP allmodconfig
* ia64 SMP allmodconfig
* s390 SMP allmodconfig
* alpha SMP allmodconfig
* um on x86_64 SMP allmodconfig
8. percpu.h modifications were reverted so that it could be applied as
a separate patch and serve as bisection point.
Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
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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>
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Allow keys for which the key type has been removed to be unlinked. Currently
dead-type keys can only be disposed of by completely clearing the keyrings
that point to them.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
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- is_single_threaded(task) is not safe unless task == current,
we can't use task->signal or task->mm.
- it doesn't make sense unless task == current, the task can
fork right after the check.
Rename it to current_is_single_threaded() and kill the argument.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
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per-uid keys were looked by uid only. Use the user namespace
to distinguish the same uid in different namespaces.
This does not address key_permission. So a task can for instance
try to join a keyring owned by the same uid in another namespace.
That will be handled by a separate patch.
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
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Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
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Inaugurate copy-on-write credentials management. This uses RCU to manage the
credentials pointer in the task_struct with respect to accesses by other tasks.
A process may only modify its own credentials, and so does not need locking to
access or modify its own credentials.
A mutex (cred_replace_mutex) is added to the task_struct to control the effect
of PTRACE_ATTACHED on credential calculations, particularly with respect to
execve().
With this patch, the contents of an active credentials struct may not be
changed directly; rather a new set of credentials must be prepared, modified
and committed using something like the following sequence of events:
struct cred *new = prepare_creds();
int ret = blah(new);
if (ret < 0) {
abort_creds(new);
return ret;
}
return commit_creds(new);
There are some exceptions to this rule: the keyrings pointed to by the active
credentials may be instantiated - keyrings violate the COW rule as managing
COW keyrings is tricky, given that it is possible for a task to directly alter
the keys in a keyring in use by another task.
To help enforce this, various pointers to sets of credentials, such as those in
the task_struct, are declared const. The purpose of this is compile-time
discouragement of altering credentials through those pointers. Once a set of
credentials has been made public through one of these pointers, it may not be
modified, except under special circumstances:
(1) Its reference count may incremented and decremented.
(2) The keyrings to which it points may be modified, but not replaced.
The only safe way to modify anything else is to create a replacement and commit
using the functions described in Documentation/credentials.txt (which will be
added by a later patch).
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
This now prepares and commits credentials in various places in the
security code rather than altering the current creds directly.
(2) Temporary credential overrides.
do_coredump() and sys_faccessat() now prepare their own credentials and
temporarily override the ones currently on the acting thread, whilst
preventing interference from other threads by holding cred_replace_mutex
on the thread being dumped.
This will be replaced in a future patch by something that hands down the
credentials directly to the functions being called, rather than altering
the task's objective credentials.
(3) LSM interface.
A number of functions have been changed, added or removed:
(*) security_capset_check(), ->capset_check()
(*) security_capset_set(), ->capset_set()
Removed in favour of security_capset().
(*) security_capset(), ->capset()
New. This is passed a pointer to the new creds, a pointer to the old
creds and the proposed capability sets. It should fill in the new
creds or return an error. All pointers, barring the pointer to the
new creds, are now const.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
Changed; now returns a value, which will cause the process to be
killed if it's an error.
(*) security_task_alloc(), ->task_alloc_security()
Removed in favour of security_prepare_creds().
(*) security_cred_free(), ->cred_free()
New. Free security data attached to cred->security.
(*) security_prepare_creds(), ->cred_prepare()
New. Duplicate any security data attached to cred->security.
(*) security_commit_creds(), ->cred_commit()
New. Apply any security effects for the upcoming installation of new
security by commit_creds().
(*) security_task_post_setuid(), ->task_post_setuid()
Removed in favour of security_task_fix_setuid().
(*) security_task_fix_setuid(), ->task_fix_setuid()
Fix up the proposed new credentials for setuid(). This is used by
cap_set_fix_setuid() to implicitly adjust capabilities in line with
setuid() changes. Changes are made to the new credentials, rather
than the task itself as in security_task_post_setuid().
(*) security_task_reparent_to_init(), ->task_reparent_to_init()
Removed. Instead the task being reparented to init is referred
directly to init's credentials.
NOTE! This results in the loss of some state: SELinux's osid no
longer records the sid of the thread that forked it.
(*) security_key_alloc(), ->key_alloc()
(*) security_key_permission(), ->key_permission()
Changed. These now take cred pointers rather than task pointers to
refer to the security context.
(4) sys_capset().
This has been simplified and uses less locking. The LSM functions it
calls have been merged.
(5) reparent_to_kthreadd().
This gives the current thread the same credentials as init by simply using
commit_thread() to point that way.
(6) __sigqueue_alloc() and switch_uid()
__sigqueue_alloc() can't stop the target task from changing its creds
beneath it, so this function gets a reference to the currently applicable
user_struct which it then passes into the sigqueue struct it returns if
successful.
switch_uid() is now called from commit_creds(), and possibly should be
folded into that. commit_creds() should take care of protecting
__sigqueue_alloc().
(7) [sg]et[ug]id() and co and [sg]et_current_groups.
The set functions now all use prepare_creds(), commit_creds() and
abort_creds() to build and check a new set of credentials before applying
it.
security_task_set[ug]id() is called inside the prepared section. This
guarantees that nothing else will affect the creds until we've finished.
The calling of set_dumpable() has been moved into commit_creds().
Much of the functionality of set_user() has been moved into
commit_creds().
The get functions all simply access the data directly.
(8) security_task_prctl() and cap_task_prctl().
security_task_prctl() has been modified to return -ENOSYS if it doesn't
want to handle a function, or otherwise return the return value directly
rather than through an argument.
Additionally, cap_task_prctl() now prepares a new set of credentials, even
if it doesn't end up using it.
(9) Keyrings.
A number of changes have been made to the keyrings code:
(a) switch_uid_keyring(), copy_keys(), exit_keys() and suid_keys() have
all been dropped and built in to the credentials functions directly.
They may want separating out again later.
(b) key_alloc() and search_process_keyrings() now take a cred pointer
rather than a task pointer to specify the security context.
(c) copy_creds() gives a new thread within the same thread group a new
thread keyring if its parent had one, otherwise it discards the thread
keyring.
(d) The authorisation key now points directly to the credentials to extend
the search into rather pointing to the task that carries them.
(e) Installing thread, process or session keyrings causes a new set of
credentials to be created, even though it's not strictly necessary for
process or session keyrings (they're shared).
(10) Usermode helper.
The usermode helper code now carries a cred struct pointer in its
subprocess_info struct instead of a new session keyring pointer. This set
of credentials is derived from init_cred and installed on the new process
after it has been cloned.
call_usermodehelper_setup() allocates the new credentials and
call_usermodehelper_freeinfo() discards them if they haven't been used. A
special cred function (prepare_usermodeinfo_creds()) is provided
specifically for call_usermodehelper_setup() to call.
call_usermodehelper_setkeys() adjusts the credentials to sport the
supplied keyring as the new session keyring.
(11) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) selinux_setprocattr() no longer does its check for whether the
current ptracer can access processes with the new SID inside the lock
that covers getting the ptracer's SID. Whilst this lock ensures that
the check is done with the ptracer pinned, the result is only valid
until the lock is released, so there's no point doing it inside the
lock.
(12) is_single_threaded().
This function has been extracted from selinux_setprocattr() and put into
a file of its own in the lib/ directory as join_session_keyring() now
wants to use it too.
The code in SELinux just checked to see whether a task shared mm_structs
with other tasks (CLONE_VM), but that isn't good enough. We really want
to know if they're part of the same thread group (CLONE_THREAD).
(13) nfsd.
The NFS server daemon now has to use the COW credentials to set the
credentials it is going to use. It really needs to pass the credentials
down to the functions it calls, but it can't do that until other patches
in this series have been applied.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: James Morris <jmorris@namei.org>
|
|
Separate per-task-group keyrings from signal_struct and dangle their anchor
from the cred struct rather than the signal_struct.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <jmorris@namei.org>
Signed-off-by: James Morris <jmorris@namei.org>
|
|
Use RCU to access another task's creds and to release a task's own creds.
This means that it will be possible for the credentials of a task to be
replaced without another task (a) requiring a full lock to read them, and (b)
seeing deallocated memory.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
|
|
Wrap current->cred and a few other accessors to hide their actual
implementation.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
|
|
Separate the task security context from task_struct. At this point, the
security data is temporarily embedded in the task_struct with two pointers
pointing to it.
Note that the Alpha arch is altered as it refers to (E)UID and (E)GID in
entry.S via asm-offsets.
With comment fixes Signed-off-by: Marc Dionne <marc.c.dionne@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
|
|
Alter the use of the key instantiation and negation functions' link-to-keyring
arguments. Currently this specifies a keyring in the target process to link
the key into, creating the keyring if it doesn't exist. This, however, can be
a problem for copy-on-write credentials as it means that the instantiating
process can alter the credentials of the requesting process.
This patch alters the behaviour such that:
(1) If keyctl_instantiate_key() or keyctl_negate_key() are given a specific
keyring by ID (ringid >= 0), then that keyring will be used.
(2) If keyctl_instantiate_key() or keyctl_negate_key() are given one of the
special constants that refer to the requesting process's keyrings
(KEY_SPEC_*_KEYRING, all <= 0), then:
(a) If sys_request_key() was given a keyring to use (destringid) then the
key will be attached to that keyring.
(b) If sys_request_key() was given a NULL keyring, then the key being
instantiated will be attached to the default keyring as set by
keyctl_set_reqkey_keyring().
(3) No extra link will be made.
Decision point (1) follows current behaviour, and allows those instantiators
who've searched for a specifically named keyring in the requestor's keyring so
as to partition the keys by type to still have their named keyrings.
Decision point (2) allows the requestor to make sure that the key or keys that
get produced by request_key() go where they want, whilst allowing the
instantiator to request that the key is retained. This is mainly useful for
situations where the instantiator makes a secondary request, the key for which
should be retained by the initial requestor:
+-----------+ +--------------+ +--------------+
| | | | | |
| Requestor |------->| Instantiator |------->| Instantiator |
| | | | | |
+-----------+ +--------------+ +--------------+
request_key() request_key()
This might be useful, for example, in Kerberos, where the requestor requests a
ticket, and then the ticket instantiator requests the TGT, which someone else
then has to go and fetch. The TGT, however, should be retained in the
keyrings of the requestor, not the first instantiator. To make this explict
an extra special keyring constant is also added.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <jmorris@namei.org>
Signed-off-by: James Morris <jmorris@namei.org>
|
|
Don't generate the per-UID user and user session keyrings unless they're
explicitly accessed. This solves a problem during a login process whereby
set*uid() is called before the SELinux PAM module, resulting in the per-UID
keyrings having the wrong security labels.
This also cures the problem of multiple per-UID keyrings sometimes appearing
due to PAM modules (including pam_keyinit) setuiding and causing user_structs
to come into and go out of existence whilst the session keyring pins the user
keyring. This is achieved by first searching for extant per-UID keyrings
before inventing new ones.
The serial bound argument is also dropped from find_keyring_by_name() as it's
not currently made use of (setting it to 0 disables the feature).
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: <kwc@citi.umich.edu>
Cc: <arunsr@cse.iitk.ac.in>
Cc: <dwalsh@redhat.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: James Morris <jmorris@namei.org>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Convert instances of ERR_PTR(PTR_ERR(p)) to ERR_CAST(p) using:
perl -spi -e 's/ERR_PTR[(]PTR_ERR[(](.*)[)][)]/ERR_CAST(\1)/' `grep -rl 'ERR_PTR[(]*PTR_ERR' fs crypto net security`
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Make request_key() and co fundamentally asynchronous to make it easier for
NFS to make use of them. There are now accessor functions that do
asynchronous constructions, a wait function to wait for construction to
complete, and a completion function for the key type to indicate completion
of construction.
Note that the construction queue is now gone. Instead, keys under
construction are linked in to the appropriate keyring in advance, and that
anyone encountering one must wait for it to be complete before they can use
it. This is done automatically for userspace.
The following auxiliary changes are also made:
(1) Key type implementation stuff is split from linux/key.h into
linux/key-type.h.
(2) AF_RXRPC provides a way to allocate null rxrpc-type keys so that AFS does
not need to call key_instantiate_and_link() directly.
(3) Adjust the debugging macros so that they're -Wformat checked even if
they are disabled, and make it so they can be enabled simply by defining
__KDEBUG to be consistent with other code of mine.
(3) Documentation.
[alan@lxorguk.ukuu.org.uk: keys: missing word in documentation]
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Name some of the remaning 'old_style_spin_init' locks
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
|
|
Add the ability for key creation to overrun the user's quota in some
circumstances - notably when a session keyring is created and assigned to a
process that didn't previously have one.
This means it's still possible to log in, should PAM require the creation of a
new session keyring, and fix an overburdened key quota.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
|
|
Add a revocation notification method to the key type and calls it whilst
the key's semaphore is still write-locked after setting the revocation
flag.
The patch then uses this to maintain a reference on the task_struct of the
process that calls request_key() for as long as the authorisation key
remains unrevoked.
This fixes a potential race between two processes both of which have
assumed the authority to instantiate a key (one may have forked the other
for example). The problem is that there's no locking around the check for
revocation of the auth key and the use of the task_struct it points to, nor
does the auth key keep a reference on the task_struct.
Access to the "context" pointer in the auth key must thenceforth be done
with the auth key semaphore held. The revocation method is called with the
target key semaphore held write-locked and the search of the context
process's keyrings is done with the auth key semaphore read-locked.
The check for the revocation state of the auth key just prior to searching
it is done after the auth key is read-locked for the search. This ensures
that the auth key can't be revoked between the check and the search.
The revocation notification method is added so that the context task_struct
can be released as soon as instantiation happens rather than waiting for
the auth key to be destroyed, thus avoiding the unnecessary pinning of the
requesting process.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
|
|
Introduce SELinux hooks to support the access key retention subsystem
within the kernel. Incorporate new flask headers from a modified version
of the SELinux reference policy, with support for the new security class
representing retained keys. Extend the "key_alloc" security hook with a
task parameter representing the intended ownership context for the key
being allocated. Attach security information to root's default keyrings
within the SELinux initialization routine.
Has passed David's testsuite.
Signed-off-by: Michael LeMay <mdlemay@epoch.ncsc.mil>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Acked-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
|
|
Remove an unnecessary memory barrier (implicit in rcu_dereference()) from
install_session_keyring().
install_session_keyring() is also rearranged a little to make it slightly
more efficient.
As install_*_keyring() may schedule (in synchronize_rcu() or
keyring_alloc()), they may not be entered with interrupts disabled - and so
there's no point saving the interrupt disablement state over the critical
section.
exec_keys() will also be invoked with interrupts enabled, and so that doesn't
need to save the interrupt state either.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
|
|
Semaphore to mutex conversion.
The conversion was generated via scripts, and the result was validated
automatically via a script as well.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Stephen Smalley <sds@epoch.ncsc.mil>
Cc: James Morris <jmorris@namei.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
|
|
Make it possible for a running process (such as gssapid) to be able to
instantiate a key, as was requested by Trond Myklebust for NFS4.
The patch makes the following changes:
(1) A new, optional key type method has been added. This permits a key type
to intercept requests at the point /sbin/request-key is about to be
spawned and do something else with them - passing them over the
rpc_pipefs files or netlink sockets for instance.
The uninstantiated key, the authorisation key and the intended operation
name are passed to the method.
(2) The callout_info is no longer passed as an argument to /sbin/request-key
to prevent unauthorised viewing of this data using ps or by looking in
/proc/pid/cmdline.
This means that the old /sbin/request-key program will not work with the
patched kernel as it will expect to see an extra argument that is no
longer there.
A revised keyutils package will be made available tomorrow.
(3) The callout_info is now attached to the authorisation key. Reading this
key will retrieve the information.
(4) A new field has been added to the task_struct. This holds the
authorisation key currently active for a thread. Searches now look here
for the caller's set of keys rather than looking for an auth key in the
lowest level of the session keyring.
This permits a thread to be servicing multiple requests at once and to
switch between them. Note that this is per-thread, not per-process, and
so is usable in multithreaded programs.
The setting of this field is inherited across fork and exec.
(5) A new keyctl function (KEYCTL_ASSUME_AUTHORITY) has been added that
permits a thread to assume the authority to deal with an uninstantiated
key. Assumption is only permitted if the authorisation key associated
with the uninstantiated key is somewhere in the thread's keyrings.
This function can also clear the assumption.
(6) A new magic key specifier has been added to refer to the currently
assumed authorisation key (KEY_SPEC_REQKEY_AUTH_KEY).
(7) Instantiation will only proceed if the appropriate authorisation key is
assumed first. The assumed authorisation key is discarded if
instantiation is successful.
(8) key_validate() is moved from the file of request_key functions to the
file of permissions functions.
(9) The documentation is updated.
From: <Valdis.Kletnieks@vt.edu>
Build fix.
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Alexander Zangerl <az@bond.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
|
|
The attached patch adds LSM hooks for key management facilities. The notable
changes are:
(1) The key struct now supports a security pointer for the use of security
modules. This will permit key labelling and restrictions on which
programs may access a key.
(2) Security modules get a chance to note (or abort) the allocation of a key.
(3) The key permission checking can now be enhanced by the security modules;
the permissions check consults LSM if all other checks bear out.
(4) The key permissions checking functions now return an error code rather
than a boolean value.
(5) An extra permission has been added to govern the modification of
attributes (UID, GID, permissions).
Note that there isn't an LSM hook specifically for each keyctl() operation,
but rather the permissions hook allows control of individual operations based
on the permission request bits.
Key management access control through LSM is enabled by automatically if both
CONFIG_KEYS and CONFIG_SECURITY are enabled.
This should be applied on top of the patch ensubjected:
[PATCH] Keys: Possessor permissions should be additive
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Chris Wright <chrisw@osdl.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
|
|
The attached patch adds extra permission grants to keys for the possessor of a
key in addition to the owner, group and other permissions bits. This makes
SUID binaries easier to support without going as far as labelling keys and key
targets using the LSM facilities.
This patch adds a second "pointer type" to key structures (struct key_ref *)
that can have the bottom bit of the address set to indicate the possession of
a key. This is propagated through searches from the keyring to the discovered
key. It has been made a separate type so that the compiler can spot attempts
to dereference a potentially incorrect pointer.
The "possession" attribute can't be attached to a key structure directly as
it's not an intrinsic property of a key.
Pointers to keys have been replaced with struct key_ref *'s wherever
possession information needs to be passed through.
This does assume that the bottom bit of the pointer will always be zero on
return from kmem_cache_alloc().
The key reference type has been made into a typedef so that at least it can be
located in the sources, even though it's basically a pointer to an undefined
type. I've also renamed the accessor functions to be more useful, and all
reference variables should now end in "_ref".
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
|
|
semaphore pinned
The attached patch prevents an error during the key session joining operation
from hanging future joins in the D state [CAN-2005-2098].
The problem is that the error handling path for the KEYCTL_JOIN_SESSION_KEYRING
operation has one error path that doesn't release the session management
semaphore. Further attempts to get the semaphore will then sleep for ever in
the D state.
This can happen in four situations, all involving an attempt to allocate a new
session keyring:
(1) ENOMEM.
(2) The users key quota being reached.
(3) A keyring name that is an empty string.
(4) A keyring name that is too long.
Any user may attempt this operation, and so any user can cause the problem to
occur.
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
|
|
2.6.12-rc6-mm1 has a few remaining synchronize_kernel()s, some (but not
all) in comments. This patch changes these synchronize_kernel() calls (and
comments) to synchronize_rcu() or synchronize_sched() as follows:
- arch/x86_64/kernel/mce.c mce_read(): change to synchronize_sched() to
handle races with machine-check exceptions (synchronize_rcu() would not cut
it given RCU implementations intended for hardcore realtime use.
- drivers/input/serio/i8042.c i8042_stop(): change to synchronize_sched() to
handle races with i8042_interrupt() interrupt handler. Again,
synchronize_rcu() would not cut it given RCU implementations intended for
hardcore realtime use.
- include/*/kdebug.h comments: change to synchronize_sched() to handle races
with NMIs. As before, synchronize_rcu() would not cut it...
- include/linux/list.h comment: change to synchronize_rcu(), since this
comment is for list_del_rcu().
- security/keys/key.c unregister_key_type(): change to synchronize_rcu(),
since this is interacting with RCU read side.
- security/keys/process_keys.c install_session_keyring(): change to
synchronize_rcu(), since this is interacting with RCU read side.
Signed-off-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
|
|
The attached patch makes the following changes:
(1) There's a new special key type called ".request_key_auth".
This is an authorisation key for when one process requests a key and
another process is started to construct it. This type of key cannot be
created by the user; nor can it be requested by kernel services.
Authorisation keys hold two references:
(a) Each refers to a key being constructed. When the key being
constructed is instantiated the authorisation key is revoked,
rendering it of no further use.
(b) The "authorising process". This is either:
(i) the process that called request_key(), or:
(ii) if the process that called request_key() itself had an
authorisation key in its session keyring, then the authorising
process referred to by that authorisation key will also be
referred to by the new authorisation key.
This means that the process that initiated a chain of key requests
will authorise the lot of them, and will, by default, wind up with
the keys obtained from them in its keyrings.
(2) request_key() creates an authorisation key which is then passed to
/sbin/request-key in as part of a new session keyring.
(3) When request_key() is searching for a key to hand back to the caller, if
it comes across an authorisation key in the session keyring of the
calling process, it will also search the keyrings of the process
specified therein and it will use the specified process's credentials
(fsuid, fsgid, groups) to do that rather than the calling process's
credentials.
This allows a process started by /sbin/request-key to find keys belonging
to the authorising process.
(4) A key can be read, even if the process executing KEYCTL_READ doesn't have
direct read or search permission if that key is contained within the
keyrings of a process specified by an authorisation key found within the
calling process's session keyring, and is searchable using the
credentials of the authorising process.
This allows a process started by /sbin/request-key to read keys belonging
to the authorising process.
(5) The magic KEY_SPEC_*_KEYRING key IDs when passed to KEYCTL_INSTANTIATE or
KEYCTL_NEGATE will specify a keyring of the authorising process, rather
than the process doing the instantiation.
(6) One of the process keyrings can be nominated as the default to which
request_key() should attach new keys if not otherwise specified. This is
done with KEYCTL_SET_REQKEY_KEYRING and one of the KEY_REQKEY_DEFL_*
constants. The current setting can also be read using this call.
(7) request_key() is partially interruptible. If it is waiting for another
process to finish constructing a key, it can be interrupted. This permits
a request-key cycle to be broken without recourse to rebooting.
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-Off-By: Benoit Boissinot <benoit.boissinot@ens-lyon.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The attached patch uses RCU to manage the session keyring pointer in struct
signal_struct. This means that searching need not disable interrupts and get
a the sighand spinlock to access this pointer. Furthermore, by judicious use
of rcu_read_(un)lock(), this patch also avoids the need to take and put
refcounts on the session keyring itself, thus saving on even more atomic ops.
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The attached patch changes the key implementation in a number of ways:
(1) It removes the spinlock from the key structure.
(2) The key flags are now accessed using atomic bitops instead of
write-locking the key spinlock and using C bitwise operators.
The three instantiation flags are dealt with with the construction
semaphore held during the request_key/instantiate/negate sequence, thus
rendering the spinlock superfluous.
The key flags are also now bit numbers not bit masks.
(3) The key payload is now accessed using RCU. This permits the recursive
keyring search algorithm to be simplified greatly since no locks need be
taken other than the usual RCU preemption disablement. Searching now does
not require any locks or semaphores to be held; merely that the starting
keyring be pinned.
(4) The keyring payload now includes an RCU head so that it can be disposed
of by call_rcu(). This requires that the payload be copied on unlink to
prevent introducing races in copy-down vs search-up.
(5) The user key payload is now a structure with the data following it. It
includes an RCU head like the keyring payload and for the same reason. It
also contains a data length because the data length in the key may be
changed on another CPU whilst an RCU protected read is in progress on the
payload. This would then see the supposed RCU payload and the on-key data
length getting out of sync.
I'm tempted to drop the key's datalen entirely, except that it's used in
conjunction with quota management and so is a little tricky to get rid
of.
(6) Update the keys documentation.
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
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