Commit Graph

3429 Commits

Author SHA1 Message Date
Casey Schaufler 57e7ba04d4 lsm: fix smack_inode_removexattr and xattr_getsecurity memleak
security_inode_getsecurity() provides the text string value
of a security attribute. It does not provide a "secctx".
The code in xattr_getsecurity() that calls security_inode_getsecurity()
and then calls security_release_secctx() happened to work because
SElinux and Smack treat the attribute and the secctx the same way.
It fails for cap_inode_getsecurity(), because that module has no
secctx that ever needs releasing. It turns out that Smack is the
one that's doing things wrong by not allocating memory when instructed
to do so by the "alloc" parameter.

The fix is simple enough. Change the security_release_secctx() to
kfree() because it isn't a secctx being returned by
security_inode_getsecurity(). Change Smack to allocate the string when
told to do so.

Note: this also fixes memory leaks for LSMs which implement
inode_getsecurity but not release_secctx, such as capabilities.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reported-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: stable@vger.kernel.org
Signed-off-by: James Morris <james.l.morris@oracle.com>
2017-10-04 18:03:15 +11:00
James Morris 2569e7e1d6 Merge commit 'keys-fixes-20170927' into fixes-v4.14-rc3
From David Howells:

"There are two sets of patches here:
 (1) A bunch of core keyrings bug fixes from Eric Biggers.

 (2) Fixing big_key to use safe crypto from Jason A. Donenfeld."
2017-09-28 09:11:28 +10:00
Jason A. Donenfeld 428490e38b security/keys: rewrite all of big_key crypto
This started out as just replacing the use of crypto/rng with
get_random_bytes_wait, so that we wouldn't use bad randomness at boot
time. But, upon looking further, it appears that there were even deeper
underlying cryptographic problems, and that this seems to have been
committed with very little crypto review. So, I rewrote the whole thing,
trying to keep to the conventions introduced by the previous author, to
fix these cryptographic flaws.

It makes no sense to seed crypto/rng at boot time and then keep
using it like this, when in fact there's already get_random_bytes_wait,
which can ensure there's enough entropy and be a much more standard way
of generating keys. Since this sensitive material is being stored
untrusted, using ECB and no authentication is simply not okay at all. I
find it surprising and a bit horrifying that this code even made it past
basic crypto review, which perhaps points to some larger issues. This
patch moves from using AES-ECB to using AES-GCM. Since keys are uniquely
generated each time, we can set the nonce to zero. There was also a race
condition in which the same key would be reused at the same time in
different threads. A mutex fixes this issue now.

So, to summarize, this commit fixes the following vulnerabilities:

  * Low entropy key generation, allowing an attacker to potentially
    guess or predict keys.
  * Unauthenticated encryption, allowing an attacker to modify the
    cipher text in particular ways in order to manipulate the plaintext,
    which is is even more frightening considering the next point.
  * Use of ECB mode, allowing an attacker to trivially swap blocks or
    compare identical plaintext blocks.
  * Key re-use.
  * Faulty memory zeroing.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Eric Biggers <ebiggers3@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Kirill Marinushkin <k.marinushkin@gmail.com>
Cc: security@kernel.org
Cc: stable@vger.kernel.org
2017-09-25 23:31:58 +01:00
Jason A. Donenfeld 910801809b security/keys: properly zero out sensitive key material in big_key
Error paths forgot to zero out sensitive material, so this patch changes
some kfrees into a kzfrees.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Eric Biggers <ebiggers3@gmail.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Kirill Marinushkin <k.marinushkin@gmail.com>
Cc: security@kernel.org
Cc: stable@vger.kernel.org
2017-09-25 23:31:41 +01:00
Eric Biggers e007ce9c59 KEYS: use kmemdup() in request_key_auth_new()
kmemdup() is preferred to kmalloc() followed by memcpy().

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
2017-09-25 15:19:57 +01:00
Eric Biggers 4aa68e07d8 KEYS: restrict /proc/keys by credentials at open time
When checking for permission to view keys whilst reading from
/proc/keys, we should use the credentials with which the /proc/keys file
was opened.  This is because, in a classic type of exploit, it can be
possible to bypass checks for the *current* credentials by passing the
file descriptor to a suid program.

Following commit 34dbbcdbf6 ("Make file credentials available to the
seqfile interfaces") we can finally fix it.  So let's do it.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
2017-09-25 15:19:57 +01:00
Eric Biggers 8f674565d4 KEYS: reset parent each time before searching key_user_tree
In key_user_lookup(), if there is no key_user for the given uid, we drop
key_user_lock, allocate a new key_user, and search the tree again.  But
we failed to set 'parent' to NULL at the beginning of the second search.
If the tree were to be empty for the second search, the insertion would
be done with an invalid 'parent', scribbling over freed memory.

Fortunately this can't actually happen currently because the tree always
contains at least the root_key_user.  But it still should be fixed to
make the code more robust.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
2017-09-25 15:19:57 +01:00
Eric Biggers 37863c43b2 KEYS: prevent KEYCTL_READ on negative key
Because keyctl_read_key() looks up the key with no permissions
requested, it may find a negatively instantiated key.  If the key is
also possessed, we went ahead and called ->read() on the key.  But the
key payload will actually contain the ->reject_error rather than the
normal payload.  Thus, the kernel oopses trying to read the
user_key_payload from memory address (int)-ENOKEY = 0x00000000ffffff82.

Fortunately the payload data is stored inline, so it shouldn't be
possible to abuse this as an arbitrary memory read primitive...

Reproducer:
    keyctl new_session
    keyctl request2 user desc '' @s
    keyctl read $(keyctl show | awk '/user: desc/ {print $1}')

It causes a crash like the following:
     BUG: unable to handle kernel paging request at 00000000ffffff92
     IP: user_read+0x33/0xa0
     PGD 36a54067 P4D 36a54067 PUD 0
     Oops: 0000 [#1] SMP
     CPU: 0 PID: 211 Comm: keyctl Not tainted 4.14.0-rc1 #337
     Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-20170228_101828-anatol 04/01/2014
     task: ffff90aa3b74c3c0 task.stack: ffff9878c0478000
     RIP: 0010:user_read+0x33/0xa0
     RSP: 0018:ffff9878c047bee8 EFLAGS: 00010246
     RAX: 0000000000000001 RBX: ffff90aa3d7da340 RCX: 0000000000000017
     RDX: 0000000000000000 RSI: 00000000ffffff82 RDI: ffff90aa3d7da340
     RBP: ffff9878c047bf00 R08: 00000024f95da94f R09: 0000000000000000
     R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
     R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
     FS:  00007f58ece69740(0000) GS:ffff90aa3e200000(0000) knlGS:0000000000000000
     CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
     CR2: 00000000ffffff92 CR3: 0000000036adc001 CR4: 00000000003606f0
     Call Trace:
      keyctl_read_key+0xac/0xe0
      SyS_keyctl+0x99/0x120
      entry_SYSCALL_64_fastpath+0x1f/0xbe
     RIP: 0033:0x7f58ec787bb9
     RSP: 002b:00007ffc8d401678 EFLAGS: 00000206 ORIG_RAX: 00000000000000fa
     RAX: ffffffffffffffda RBX: 00007ffc8d402800 RCX: 00007f58ec787bb9
     RDX: 0000000000000000 RSI: 00000000174a63ac RDI: 000000000000000b
     RBP: 0000000000000004 R08: 00007ffc8d402809 R09: 0000000000000020
     R10: 0000000000000000 R11: 0000000000000206 R12: 00007ffc8d402800
     R13: 00007ffc8d4016e0 R14: 0000000000000000 R15: 0000000000000000
     Code: e5 41 55 49 89 f5 41 54 49 89 d4 53 48 89 fb e8 a4 b4 ad ff 85 c0 74 09 80 3d b9 4c 96 00 00 74 43 48 8b b3 20 01 00 00 4d 85 ed <0f> b7 5e 10 74 29 4d 85 e4 74 24 4c 39 e3 4c 89 e2 4c 89 ef 48
     RIP: user_read+0x33/0xa0 RSP: ffff9878c047bee8
     CR2: 00000000ffffff92

Fixes: 61ea0c0ba9 ("KEYS: Skip key state checks when checking for possession")
Cc: <stable@vger.kernel.org>	[v3.13+]
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
2017-09-25 15:19:57 +01:00
Eric Biggers 237bbd29f7 KEYS: prevent creating a different user's keyrings
It was possible for an unprivileged user to create the user and user
session keyrings for another user.  For example:

    sudo -u '#3000' sh -c 'keyctl add keyring _uid.4000 "" @u
                           keyctl add keyring _uid_ses.4000 "" @u
                           sleep 15' &
    sleep 1
    sudo -u '#4000' keyctl describe @u
    sudo -u '#4000' keyctl describe @us

This is problematic because these "fake" keyrings won't have the right
permissions.  In particular, the user who created them first will own
them and will have full access to them via the possessor permissions,
which can be used to compromise the security of a user's keys:

    -4: alswrv-----v------------  3000     0 keyring: _uid.4000
    -5: alswrv-----v------------  3000     0 keyring: _uid_ses.4000

Fix it by marking user and user session keyrings with a flag
KEY_FLAG_UID_KEYRING.  Then, when searching for a user or user session
keyring by name, skip all keyrings that don't have the flag set.

Fixes: 69664cf16a ("keys: don't generate user and user session keyrings unless they're accessed")
Cc: <stable@vger.kernel.org>	[v2.6.26+]
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
2017-09-25 15:19:57 +01:00
Eric Biggers e645016abc KEYS: fix writing past end of user-supplied buffer in keyring_read()
Userspace can call keyctl_read() on a keyring to get the list of IDs of
keys in the keyring.  But if the user-supplied buffer is too small, the
kernel would write the full list anyway --- which will corrupt whatever
userspace memory happened to be past the end of the buffer.  Fix it by
only filling the space that is available.

Fixes: b2a4df200d ("KEYS: Expand the capacity of a keyring")
Cc: <stable@vger.kernel.org>	[v3.13+]
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
2017-09-25 15:19:57 +01:00
Eric Biggers 7fc0786d95 KEYS: fix key refcount leak in keyctl_read_key()
In keyctl_read_key(), if key_permission() were to return an error code
other than EACCES, we would leak a the reference to the key.  This can't
actually happen currently because key_permission() can only return an
error code other than EACCES if security_key_permission() does, only
SELinux and Smack implement that hook, and neither can return an error
code other than EACCES.  But it should still be fixed, as it is a bug
waiting to happen.

Fixes: 29db919063 ("[PATCH] Keys: Add LSM hooks for key management [try #3]")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
2017-09-25 15:19:57 +01:00
Eric Biggers 884bee0215 KEYS: fix key refcount leak in keyctl_assume_authority()
In keyctl_assume_authority(), if keyctl_change_reqkey_auth() were to
fail, we would leak the reference to the 'authkey'.  Currently this can
only happen if prepare_creds() fails to allocate memory.  But it still
should be fixed, as it is a more severe bug waiting to happen.

This patch also moves the read of 'authkey->serial' to before the
reference to the authkey is dropped.  Doing the read after dropping the
reference is very fragile because it assumes we still hold another
reference to the key.  (Which we do, in current->cred->request_key_auth,
but there's no reason not to write it in the "obviously correct" way.)

Fixes: d84f4f992c ("CRED: Inaugurate COW credentials")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
2017-09-25 15:19:57 +01:00
Eric Biggers f7b48cf08f KEYS: don't revoke uninstantiated key in request_key_auth_new()
If key_instantiate_and_link() were to fail (which fortunately isn't
possible currently), the call to key_revoke(authkey) would crash with a
NULL pointer dereference in request_key_auth_revoke() because the key
has not yet been instantiated.

Fix this by removing the call to key_revoke().  key_put() is sufficient,
as it's not possible for an uninstantiated authkey to have been used for
anything yet.

Fixes: b5f545c880 ("[PATCH] keys: Permit running process to instantiate keys")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
2017-09-25 15:19:56 +01:00
Eric Biggers 44d8143340 KEYS: fix cred refcount leak in request_key_auth_new()
In request_key_auth_new(), if key_alloc() or key_instantiate_and_link()
were to fail, we would leak a reference to the 'struct cred'.  Currently
this can only happen if key_alloc() fails to allocate memory.  But it
still should be fixed, as it is a more severe bug waiting to happen.

Fix it by cleaning things up to use a helper function which frees a
'struct request_key_auth' correctly.

Fixes: d84f4f992c ("CRED: Inaugurate COW credentials")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
2017-09-25 15:03:55 +01:00
Linus Torvalds a302824782 Merge branch 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security
Pull misc security layer update from James Morris:
 "This is the remaining 'general' change in the security tree for v4.14,
  following the direct merging of SELinux (+ TOMOYO), AppArmor, and
  seccomp.

  That's everything now for the security tree except IMA, which will
  follow shortly (I've been traveling for the past week with patchy
  internet)"

* 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  security: fix description of values returned by cap_inode_need_killpriv
2017-09-24 11:40:41 -07:00
Stefan Berger ab5348c9c2 security: fix description of values returned by cap_inode_need_killpriv
cap_inode_need_killpriv returns 1 if security.capability exists and
has a value and inode_killpriv() is required, 0 otherwise. Fix the
description of the return value to reflect this.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
2017-09-23 21:15:41 -07:00
Linus Torvalds 79444df4e7 + Features
- in preparation for secid mapping add support for absolute root view
     based labels
   - add base infastructure for socket mediation
   - add mount mediation
   - add signal mediation
 
 + minor cleanups and changes
   - be defensive, ensure unconfined profiles have dfas initialized
   - add more debug asserts to apparmorfs
   - enable policy unpacking to audit different reasons for failure
   - cleanup conditional check for label in label_print
   - Redundant condition: prev_ns. in [label.c:1498]
 
 + Bug Fixes
   - fix regression in apparmorfs DAC access permissions
   - fix build failure on sparc caused by undeclared signals
   - fix sparse report of incorrect type assignment when freeing label proxies
   - fix race condition in null profile creation
   - Fix an error code in aafs_create()
   - Fix logical error in verify_header()
   - Fix shadowed local variable in unpack_trans_table()
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Merge tag 'apparmor-pr-2017-09-22' of git://git.kernel.org/pub/scm/linux/kernel/git/jj/linux-apparmor

Pull apparmor updates from John Johansen:
 "This is the apparmor pull request, similar to SELinux and seccomp.

  It's the same series that I was sent to James' security tree + one
  regression fix that was found after the series was sent to James and
  would have been sent for v4.14-rc2.

  Features:
  - in preparation for secid mapping add support for absolute root view
    based labels
  - add base infastructure for socket mediation
  - add mount mediation
  - add signal mediation

  minor cleanups and changes:
  - be defensive, ensure unconfined profiles have dfas initialized
  - add more debug asserts to apparmorfs
  - enable policy unpacking to audit different reasons for failure
  - cleanup conditional check for label in label_print
  - Redundant condition: prev_ns. in [label.c:1498]

  Bug Fixes:
  - fix regression in apparmorfs DAC access permissions
  - fix build failure on sparc caused by undeclared signals
  - fix sparse report of incorrect type assignment when freeing label proxies
  - fix race condition in null profile creation
  - Fix an error code in aafs_create()
  - Fix logical error in verify_header()
  - Fix shadowed local variable in unpack_trans_table()"

* tag 'apparmor-pr-2017-09-22' of git://git.kernel.org/pub/scm/linux/kernel/git/jj/linux-apparmor:
  apparmor: fix apparmorfs DAC access permissions
  apparmor: fix build failure on sparc caused by undeclared signals
  apparmor: fix incorrect type assignment when freeing proxies
  apparmor: ensure unconfined profiles have dfas initialized
  apparmor: fix race condition in null profile creation
  apparmor: move new_null_profile to after profile lookup fns()
  apparmor: add base infastructure for socket mediation
  apparmor: add more debug asserts to apparmorfs
  apparmor: make policy_unpack able to audit different info messages
  apparmor: add support for absolute root view based labels
  apparmor: cleanup conditional check for label in label_print
  apparmor: add mount mediation
  apparmor: add the ability to mediate signals
  apparmor: Redundant condition: prev_ns. in [label.c:1498]
  apparmor: Fix an error code in aafs_create()
  apparmor: Fix logical error in verify_header()
  apparmor: Fix shadowed local variable in unpack_trans_table()
2017-09-23 05:33:29 -10:00
John Johansen bf81100f63 apparmor: fix apparmorfs DAC access permissions
The DAC access permissions for several apparmorfs files are wrong.

.access - needs to be writable by all tasks to perform queries
the others in the set only provide a read fn so should be read only.

With policy namespace virtualization all apparmor needs to control
the permission and visibility checks directly which means DAC
access has to be allowed for all user, group, and other.

BugLink: http://bugs.launchpad.net/bugs/1713103
Fixes: c97204baf8 ("apparmor: rename apparmor file fns and data to indicate use")
Signed-off-by: John Johansen <john.johansen@canonical.com>
2017-09-22 13:20:01 -07:00
John Johansen b1545dba09 apparmor: fix build failure on sparc caused by undeclared signals
In file included from security/apparmor/ipc.c:23:0:
  security/apparmor/include/sig_names.h:26:3: error: 'SIGSTKFLT' undeclared here (not in a function)
    [SIGSTKFLT] = 16, /* -, 16, - */
     ^
  security/apparmor/include/sig_names.h:26:3: error: array index in initializer not of integer type
  security/apparmor/include/sig_names.h:26:3: note: (near initialization for 'sig_map')
  security/apparmor/include/sig_names.h:51:3: error: 'SIGUNUSED' undeclared here (not in a function)
    [SIGUNUSED] = 34, /* -, 31, - */
     ^
  security/apparmor/include/sig_names.h:51:3: error: array index in initializer not of integer type
  security/apparmor/include/sig_names.h:51:3: note: (near initialization for 'sig_map')

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Fixes: c6bf1adaecaa ("apparmor: add the ability to mediate signals")
Signed-off-by: John Johansen <john.johansen@canonical.com>
2017-09-22 13:00:58 -07:00
John Johansen bc4d82fb94 apparmor: fix incorrect type assignment when freeing proxies
sparse reports

poisoning the proxy->label before freeing the struct is resulting in
a sparse build warning.
../security/apparmor/label.c:52:30: warning: incorrect type in assignment (different address spaces)
../security/apparmor/label.c:52:30:    expected struct aa_label [noderef] <asn:4>*label
../security/apparmor/label.c:52:30:    got struct aa_label *<noident>

fix with RCU_INIT_POINTER as this is one of those cases where
rcu_assign_pointer() is not needed.

Signed-off-by: John Johansen <john.johansen@canonical.com>
2017-09-22 13:00:58 -07:00
John Johansen 15372b97aa apparmor: ensure unconfined profiles have dfas initialized
Generally unconfined has early bailout tests and does not need the
dfas initialized, however if an early bailout test is ever missed
it will result in an oops.

Be defensive and initialize the unconfined profile to have null dfas
(no permission) so if an early bailout test is missed we fail
closed (no perms granted) instead of oopsing.

Signed-off-by: John Johansen <john.johansen@canonical.com>
2017-09-22 13:00:58 -07:00
John Johansen 290638a52a apparmor: fix race condition in null profile creation
There is a race when null- profile is being created between the
initial lookup/creation of the profile and lock/addition of the
profile. This could result in multiple version of a profile being
added to the list which need to be removed/replaced.

Since these are learning profile their is no affect on mediation.

Signed-off-by: John Johansen <john.johansen@canonical.com>
2017-09-22 13:00:58 -07:00
John Johansen d07881d2ed apparmor: move new_null_profile to after profile lookup fns()
new_null_profile will need to use some of the profile lookup fns()
so move instead of doing forward fn declarations.

Signed-off-by: John Johansen <john.johansen@canonical.com>
2017-09-22 13:00:58 -07:00
John Johansen 651e28c553 apparmor: add base infastructure for socket mediation
Provide a basic mediation of sockets. This is not a full net mediation
but just whether a spcific family of socket can be used by an
application, along with setting up some basic infrastructure for
network mediation to follow.

the user space rule hav the basic form of
  NETWORK RULE = [ QUALIFIERS ] 'network' [ DOMAIN ]
                 [ TYPE | PROTOCOL ]

  DOMAIN = ( 'inet' | 'ax25' | 'ipx' | 'appletalk' | 'netrom' |
             'bridge' | 'atmpvc' | 'x25' | 'inet6' | 'rose' |
	     'netbeui' | 'security' | 'key' | 'packet' | 'ash' |
	     'econet' | 'atmsvc' | 'sna' | 'irda' | 'pppox' |
	     'wanpipe' | 'bluetooth' | 'netlink' | 'unix' | 'rds' |
	     'llc' | 'can' | 'tipc' | 'iucv' | 'rxrpc' | 'isdn' |
	     'phonet' | 'ieee802154' | 'caif' | 'alg' | 'nfc' |
	     'vsock' | 'mpls' | 'ib' | 'kcm' ) ','

  TYPE = ( 'stream' | 'dgram' | 'seqpacket' |  'rdm' | 'raw' |
           'packet' )

  PROTOCOL = ( 'tcp' | 'udp' | 'icmp' )

eg.
  network,
  network inet,

Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>
2017-09-22 13:00:58 -07:00
John Johansen cbf2d0e1a9 apparmor: add more debug asserts to apparmorfs
Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>
2017-09-22 13:00:58 -07:00
John Johansen 2410aa96d6 apparmor: make policy_unpack able to audit different info messages
Switch unpack auditing to using the generic name field in the audit
struct and make it so we can start adding new info messages about
why an unpack failed.

Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>
2017-09-22 13:00:58 -07:00
John Johansen 26b7899510 apparmor: add support for absolute root view based labels
With apparmor policy virtualization based on policy namespace View's
we don't generally want/need absolute root based views, however there
are cases like debugging and some secid based conversions where
using a root based view is important.

Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>
2017-09-22 13:00:58 -07:00
John Johansen f872af75d3 apparmor: cleanup conditional check for label in label_print
Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>
2017-09-22 13:00:57 -07:00
John Johansen 2ea3ffb778 apparmor: add mount mediation
Add basic mount mediation. That allows controlling based on basic
mount parameters. It does not include special mount parameters for
apparmor, super block labeling, or any triggers for apparmor namespace
parameter modifications on pivot root.

default userspace policy rules have the form of
  MOUNT RULE = ( MOUNT | REMOUNT | UMOUNT )

  MOUNT = [ QUALIFIERS ] 'mount' [ MOUNT CONDITIONS ] [ SOURCE FILEGLOB ]
          [ '->' MOUNTPOINT FILEGLOB ]

  REMOUNT = [ QUALIFIERS ] 'remount' [ MOUNT CONDITIONS ]
            MOUNTPOINT FILEGLOB

  UMOUNT = [ QUALIFIERS ] 'umount' [ MOUNT CONDITIONS ] MOUNTPOINT FILEGLOB

  MOUNT CONDITIONS = [ ( 'fstype' | 'vfstype' ) ( '=' | 'in' )
                       MOUNT FSTYPE EXPRESSION ]
		       [ 'options' ( '=' | 'in' ) MOUNT FLAGS EXPRESSION ]

  MOUNT FSTYPE EXPRESSION = ( MOUNT FSTYPE LIST | MOUNT EXPRESSION )

  MOUNT FSTYPE LIST = Comma separated list of valid filesystem and
                      virtual filesystem types (eg ext4, debugfs, etc)

  MOUNT FLAGS EXPRESSION = ( MOUNT FLAGS LIST | MOUNT EXPRESSION )

  MOUNT FLAGS LIST = Comma separated list of MOUNT FLAGS.

  MOUNT FLAGS = ( 'ro' | 'rw' | 'nosuid' | 'suid' | 'nodev' | 'dev' |
                  'noexec' | 'exec' | 'sync' | 'async' | 'remount' |
		  'mand' | 'nomand' | 'dirsync' | 'noatime' | 'atime' |
		  'nodiratime' | 'diratime' | 'bind' | 'rbind' | 'move' |
		  'verbose' | 'silent' | 'loud' | 'acl' | 'noacl' |
		  'unbindable' | 'runbindable' | 'private' | 'rprivate' |
		  'slave' | 'rslave' | 'shared' | 'rshared' |
		  'relatime' | 'norelatime' | 'iversion' | 'noiversion' |
		  'strictatime' | 'nouser' | 'user' )

  MOUNT EXPRESSION = ( ALPHANUMERIC | AARE ) ...

  PIVOT ROOT RULE = [ QUALIFIERS ] pivot_root [ oldroot=OLD PUT FILEGLOB ]
                    [ NEW ROOT FILEGLOB ]

  SOURCE FILEGLOB = FILEGLOB

  MOUNTPOINT FILEGLOB = FILEGLOB

eg.
  mount,
  mount /dev/foo,
  mount options=ro /dev/foo -> /mnt/,
  mount options in (ro,atime) /dev/foo -> /mnt/,
  mount options=ro options=atime,

Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>
2017-09-22 13:00:57 -07:00
John Johansen cd1dbf76b2 apparmor: add the ability to mediate signals
Add signal mediation where the signal can be mediated based on the
signal, direction, or the label or the peer/target. The signal perms
are verified on a cross check to ensure policy consistency in the case
of incremental policy load/replacement.

The optimization of skipping the cross check when policy is guaranteed
to be consistent (single compile unit) remains to be done.

policy rules have the form of
  SIGNAL_RULE = [ QUALIFIERS ] 'signal' [ SIGNAL ACCESS PERMISSIONS ]
                [ SIGNAL SET ] [ SIGNAL PEER ]

  SIGNAL ACCESS PERMISSIONS = SIGNAL ACCESS | SIGNAL ACCESS LIST

  SIGNAL ACCESS LIST = '(' Comma or space separated list of SIGNAL
                           ACCESS ')'

  SIGNAL ACCESS = ( 'r' | 'w' | 'rw' | 'read' | 'write' | 'send' |
                    'receive' )

  SIGNAL SET = 'set' '=' '(' SIGNAL LIST ')'

  SIGNAL LIST = Comma or space separated list of SIGNALS

  SIGNALS = ( 'hup' | 'int' | 'quit' | 'ill' | 'trap' | 'abrt' |
              'bus' | 'fpe' | 'kill' | 'usr1' | 'segv' | 'usr2' |
	      'pipe' | 'alrm' | 'term' | 'stkflt' | 'chld' | 'cont' |
	      'stop' | 'stp' | 'ttin' | 'ttou' | 'urg' | 'xcpu' |
	      'xfsz' | 'vtalrm' | 'prof' | 'winch' | 'io' | 'pwr' |
	      'sys' | 'emt' | 'exists' | 'rtmin+0' ... 'rtmin+32'
            )

  SIGNAL PEER = 'peer' '=' AARE

eg.
  signal,                                 # allow all signals
  signal send set=(hup, kill) peer=foo,

Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>
2017-09-22 13:00:57 -07:00
John Johansen c5561700c9 apparmor: Redundant condition: prev_ns. in [label.c:1498]
Reported-by: David Binderman <dcb314@hotmail.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
2017-09-22 13:00:57 -07:00
Dan Carpenter 5d314a81ec apparmor: Fix an error code in aafs_create()
We accidentally forgot to set the error code on this path.  It means we
return NULL instead of an error pointer.  I looked through a bunch of
callers and I don't think it really causes a big issue, but the
documentation says we're supposed to return error pointers here.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
2017-09-22 13:00:57 -07:00
Christos Gkekas 86aea56f14 apparmor: Fix logical error in verify_header()
verify_header() is currently checking whether interface version is less
than 5 *and* greater than 7, which always evaluates to false. Instead it
should check whether it is less than 5 *or* greater than 7.

Signed-off-by: Christos Gkekas <chris.gekas@gmail.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
2017-09-22 13:00:57 -07:00
Geert Uytterhoeven 19fe43a54f apparmor: Fix shadowed local variable in unpack_trans_table()
with W=2:

    security/apparmor/policy_unpack.c: In function ‘unpack_trans_table’:
    security/apparmor/policy_unpack.c:469: warning: declaration of ‘pos’ shadows a previous local
    security/apparmor/policy_unpack.c:451: warning: shadowed declaration is here

Rename the old "pos" to "saved_pos" to fix this.

Fixes: 5379a33120 ("apparmor: support v7 transition format compatible with label_parse")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
2017-09-22 13:00:57 -07:00
Linus Torvalds 581bfce969 Merge branch 'work.set_fs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull more set_fs removal from Al Viro:
 "Christoph's 'use kernel_read and friends rather than open-coding
  set_fs()' series"

* 'work.set_fs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fs: unexport vfs_readv and vfs_writev
  fs: unexport vfs_read and vfs_write
  fs: unexport __vfs_read/__vfs_write
  lustre: switch to kernel_write
  gadget/f_mass_storage: stop messing with the address limit
  mconsole: switch to kernel_read
  btrfs: switch write_buf to kernel_write
  net/9p: switch p9_fd_read to kernel_write
  mm/nommu: switch do_mmap_private to kernel_read
  serial2002: switch serial2002_tty_write to kernel_{read/write}
  fs: make the buf argument to __kernel_write a void pointer
  fs: fix kernel_write prototype
  fs: fix kernel_read prototype
  fs: move kernel_read to fs/read_write.c
  fs: move kernel_write to fs/read_write.c
  autofs4: switch autofs4_write to __kernel_write
  ashmem: switch to ->read_iter
2017-09-14 18:13:32 -07:00
Linus Torvalds 7f85565a3f selinux/stable-4.14 PR 20170831
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Merge tag 'selinux-pr-20170831' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux

Pull selinux updates from Paul Moore:
 "A relatively quiet period for SELinux, 11 patches with only two/three
  having any substantive changes.

  These noteworthy changes include another tweak to the NNP/nosuid
  handling, per-file labeling for cgroups, and an object class fix for
  AF_UNIX/SOCK_RAW sockets; the rest of the changes are minor tweaks or
  administrative updates (Stephen's email update explains the file
  explosion in the diffstat).

  Everything passes the selinux-testsuite"

[ Also a couple of small patches from the security tree from Tetsuo
  Handa for Tomoyo and LSM cleanup. The separation of security policy
  updates wasn't all that clean - Linus ]

* tag 'selinux-pr-20170831' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
  selinux: constify nf_hook_ops
  selinux: allow per-file labeling for cgroupfs
  lsm_audit: update my email address
  selinux: update my email address
  MAINTAINERS: update the NetLabel and Labeled Networking information
  selinux: use GFP_NOWAIT in the AVC kmem_caches
  selinux: Generalize support for NNP/nosuid SELinux domain transitions
  selinux: genheaders should fail if too many permissions are defined
  selinux: update the selinux info in MAINTAINERS
  credits: update Paul Moore's info
  selinux: Assign proper class to PF_UNIX/SOCK_RAW sockets
  tomoyo: Update URLs in Documentation/admin-guide/LSM/tomoyo.rst
  LSM: Remove security_task_create() hook.
2017-09-12 13:21:00 -07:00
Linus Torvalds dd198ce714 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull namespace updates from Eric Biederman:
 "Life has been busy and I have not gotten half as much done this round
  as I would have liked. I delayed it so that a minor conflict
  resolution with the mips tree could spend a little time in linux-next
  before I sent this pull request.

  This includes two long delayed user namespace changes from Kirill
  Tkhai. It also includes a very useful change from Serge Hallyn that
  allows the security capability attribute to be used inside of user
  namespaces. The practical effect of this is people can now untar
  tarballs and install rpms in user namespaces. It had been suggested to
  generalize this and encode some of the namespace information
  information in the xattr name. Upon close inspection that makes the
  things that should be hard easy and the things that should be easy
  more expensive.

  Then there is my bugfix/cleanup for signal injection that removes the
  magic encoding of the siginfo union member from the kernel internal
  si_code. The mips folks reported the case where I had used FPE_FIXME
  me is impossible so I have remove FPE_FIXME from mips, while at the
  same time including a return statement in that case to keep gcc from
  complaining about unitialized variables.

  I almost finished the work to get make copy_siginfo_to_user a trivial
  copy to user. The code is available at:

     git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git neuter-copy_siginfo_to_user-v3

  But I did not have time/energy to get the code posted and reviewed
  before the merge window opened.

  I was able to see that the security excuse for just copying fields
  that we know are initialized doesn't work in practice there are buggy
  initializations that don't initialize the proper fields in siginfo. So
  we still sometimes copy unitialized data to userspace"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  Introduce v3 namespaced file capabilities
  mips/signal: In force_fcr31_sig return in the impossible case
  signal: Remove kernel interal si_code magic
  fcntl: Don't use ambiguous SIG_POLL si_codes
  prctl: Allow local CAP_SYS_ADMIN changing exe_file
  security: Use user_namespace::level to avoid redundant iterations in cap_capable()
  userns,pidns: Verify the userns for new pid namespaces
  signal/testing: Don't look for __SI_FAULT in userspace
  signal/mips: Document a conflict with SI_USER with SIGFPE
  signal/sparc: Document a conflict with SI_USER with SIGFPE
  signal/ia64: Document a conflict with SI_USER with SIGFPE
  signal/alpha: Document a conflict with SI_USER for SIGTRAP
2017-09-11 18:34:47 -07:00
Linus Torvalds 0fb02e718f audit/stable-4.14 PR 20170907
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Merge tag 'audit-pr-20170907' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit

Pull audit updates from Paul Moore:
 "A small pull request for audit this time, only four patches and only
  two with any real code changes.

  Those two changes are the removal of a pointless SELinux AVC
  initialization audit event and a fix to improve the audit timestamp
  overhead.

  The other two patches are comment cleanup and administrative updates,
  nothing very exciting.

  Everything passes our tests"

* tag 'audit-pr-20170907' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit:
  audit: update the function comments
  selinux: remove AVC init audit log message
  audit: update the audit info in MAINTAINERS
  audit: Reduce overhead using a coarse clock
2017-09-07 20:48:25 -07:00
Linus Torvalds 828f4257d1 This series has the ultimate goal of providing a sane stack rlimit when
running set*id processes. To do this, the bprm_secureexec LSM hook is
 collapsed into the bprm_set_creds hook so the secureexec-ness of an exec
 can be determined early enough to make decisions about rlimits and the
 resulting memory layouts. Other logic acting on the secureexec-ness of an
 exec is similarly consolidated. Capabilities needed some special handling,
 but the refactoring removed other special handling, so that was a wash.
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Merge tag 'secureexec-v4.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull secureexec update from Kees Cook:
 "This series has the ultimate goal of providing a sane stack rlimit
  when running set*id processes.

  To do this, the bprm_secureexec LSM hook is collapsed into the
  bprm_set_creds hook so the secureexec-ness of an exec can be
  determined early enough to make decisions about rlimits and the
  resulting memory layouts. Other logic acting on the secureexec-ness of
  an exec is similarly consolidated. Capabilities needed some special
  handling, but the refactoring removed other special handling, so that
  was a wash"

* tag 'secureexec-v4.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  exec: Consolidate pdeath_signal clearing
  exec: Use sane stack rlimit under secureexec
  exec: Consolidate dumpability logic
  smack: Remove redundant pdeath_signal clearing
  exec: Use secureexec for clearing pdeath_signal
  exec: Use secureexec for setting dumpability
  LSM: drop bprm_secureexec hook
  commoncap: Move cap_elevated calculation into bprm_set_creds
  commoncap: Refactor to remove bprm_secureexec hook
  smack: Refactor to remove bprm_secureexec hook
  selinux: Refactor to remove bprm_secureexec hook
  apparmor: Refactor to remove bprm_secureexec hook
  binfmt: Introduce secureexec flag
  exec: Correct comments about "point of no return"
  exec: Rename bprm->cred_prepared to called_set_creds
2017-09-07 20:35:29 -07:00
Richard Guy Briggs 19128341d6 selinux: remove AVC init audit log message
In the process of normalizing audit log messages, it was noticed that the AVC
initialization code registered an audit log KERNEL record that didn't fit the
standard format.  In the process of attempting to normalize it it was
determined that this record was not even necessary.  Remove it.

Ref: http://marc.info/?l=selinux&m=149614868525826&w=2
See: https://github.com/linux-audit/audit-kernel/issues/48
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Steve Grubb <sgrubb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
2017-09-05 09:46:57 -04:00
Christoph Hellwig e13ec939e9 fs: fix kernel_write prototype
Make the position an in/out argument like all the other read/write
helpers and and make the buf argument a void pointer.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-09-04 19:05:15 -04:00
Christoph Hellwig bdd1d2d3d2 fs: fix kernel_read prototype
Use proper ssize_t and size_t types for the return value and count
argument, move the offset last and make it an in/out argument like
all other read/write helpers, and make the buf argument a void pointer
to get rid of lots of casts in the callers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-09-04 19:05:15 -04:00
Serge E. Hallyn 8db6c34f1d Introduce v3 namespaced file capabilities
Root in a non-initial user ns cannot be trusted to write a traditional
security.capability xattr.  If it were allowed to do so, then any
unprivileged user on the host could map his own uid to root in a private
namespace, write the xattr, and execute the file with privilege on the
host.

However supporting file capabilities in a user namespace is very
desirable.  Not doing so means that any programs designed to run with
limited privilege must continue to support other methods of gaining and
dropping privilege.  For instance a program installer must detect
whether file capabilities can be assigned, and assign them if so but set
setuid-root otherwise.  The program in turn must know how to drop
partial capabilities, and do so only if setuid-root.

This patch introduces v3 of the security.capability xattr.  It builds a
vfs_ns_cap_data struct by appending a uid_t rootid to struct
vfs_cap_data.  This is the absolute uid_t (that is, the uid_t in user
namespace which mounted the filesystem, usually init_user_ns) of the
root id in whose namespaces the file capabilities may take effect.

When a task asks to write a v2 security.capability xattr, if it is
privileged with respect to the userns which mounted the filesystem, then
nothing should change.  Otherwise, the kernel will transparently rewrite
the xattr as a v3 with the appropriate rootid.  This is done during the
execution of setxattr() to catch user-space-initiated capability writes.
Subsequently, any task executing the file which has the noted kuid as
its root uid, or which is in a descendent user_ns of such a user_ns,
will run the file with capabilities.

Similarly when asking to read file capabilities, a v3 capability will
be presented as v2 if it applies to the caller's namespace.

If a task writes a v3 security.capability, then it can provide a uid for
the xattr so long as the uid is valid in its own user namespace, and it
is privileged with CAP_SETFCAP over its namespace.  The kernel will
translate that rootid to an absolute uid, and write that to disk.  After
this, a task in the writer's namespace will not be able to use those
capabilities (unless rootid was 0), but a task in a namespace where the
given uid is root will.

Only a single security.capability xattr may exist at a time for a given
file.  A task may overwrite an existing xattr so long as it is
privileged over the inode.  Note this is a departure from previous
semantics, which required privilege to remove a security.capability
xattr.  This check can be re-added if deemed useful.

This allows a simple setxattr to work, allows tar/untar to work, and
allows us to tar in one namespace and untar in another while preserving
the capability, without risking leaking privilege into a parent
namespace.

Example using tar:

 $ cp /bin/sleep sleepx
 $ mkdir b1 b2
 $ lxc-usernsexec -m b:0:100000:1 -m b:1:$(id -u):1 -- chown 0:0 b1
 $ lxc-usernsexec -m b:0:100001:1 -m b:1:$(id -u):1 -- chown 0:0 b2
 $ lxc-usernsexec -m b:0:100000:1000 -- tar --xattrs-include=security.capability --xattrs -cf b1/sleepx.tar sleepx
 $ lxc-usernsexec -m b:0:100001:1000 -- tar --xattrs-include=security.capability --xattrs -C b2 -xf b1/sleepx.tar
 $ lxc-usernsexec -m b:0:100001:1000 -- getcap b2/sleepx
   b2/sleepx = cap_sys_admin+ep
 # /opt/ltp/testcases/bin/getv3xattr b2/sleepx
   v3 xattr, rootid is 100001

A patch to linux-test-project adding a new set of tests for this
functionality is in the nsfscaps branch at github.com/hallyn/ltp

Changelog:
   Nov 02 2016: fix invalid check at refuse_fcap_overwrite()
   Nov 07 2016: convert rootid from and to fs user_ns
   (From ebiederm: mar 28 2017)
     commoncap.c: fix typos - s/v4/v3
     get_vfs_caps_from_disk: clarify the fs_ns root access check
     nsfscaps: change the code split for cap_inode_setxattr()
   Apr 09 2017:
       don't return v3 cap for caps owned by current root.
      return a v2 cap for a true v2 cap in non-init ns
   Apr 18 2017:
      . Change the flow of fscap writing to support s_user_ns writing.
      . Remove refuse_fcap_overwrite().  The value of the previous
        xattr doesn't matter.
   Apr 24 2017:
      . incorporate Eric's incremental diff
      . move cap_convert_nscap to setxattr and simplify its usage
   May 8, 2017:
      . fix leaking dentry refcount in cap_inode_getsecurity

Signed-off-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-09-01 14:57:15 -05:00
Arvind Yadav 0c3014f22d selinux: constify nf_hook_ops
nf_hook_ops are not supposed to change at runtime. nf_register_net_hooks
and nf_unregister_net_hooks are working with const nf_hook_ops.
So mark the non-const nf_hook_ops structs as const.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
2017-08-28 17:33:19 -04:00
Antonio Murdaca 901ef845fa selinux: allow per-file labeling for cgroupfs
This patch allows genfscon per-file labeling for cgroupfs. For instance,
this allows to label the "release_agent" file within each
cgroup mount and limit writes to it.

Signed-off-by: Antonio Murdaca <amurdaca@redhat.com>
[PM: subject line and merge tweaks]
Signed-off-by: Paul Moore <paul@paul-moore.com>
2017-08-22 15:38:18 -04:00
Stephen Smalley 5d72801538 lsm_audit: update my email address
Update my email address since epoch.ncsc.mil no longer exists.
MAINTAINERS and CREDITS are already correct.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
2017-08-17 15:33:39 -04:00
Stephen Smalley 7efbb60b45 selinux: update my email address
Update my email address since epoch.ncsc.mil no longer exists.
MAINTAINERS and CREDITS are already correct.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
2017-08-17 15:32:55 -04:00
Michal Hocko 476accbe2f selinux: use GFP_NOWAIT in the AVC kmem_caches
There is a strange __GFP_NOMEMALLOC usage pattern in SELinux,
specifically GFP_ATOMIC | __GFP_NOMEMALLOC which doesn't make much
sense.  GFP_ATOMIC on its own allows to access memory reserves while
__GFP_NOMEMALLOC dictates we cannot use memory reserves.  Replace this
with the much more sane GFP_NOWAIT in the AVC code as we can tolerate
memory allocation failures in that code.

Signed-off-by: Michal Hocko <mhocko@kernel.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Paul Moore <paul@paul-moore.com>
2017-08-08 09:12:23 -04:00
Stephen Smalley af63f4193f selinux: Generalize support for NNP/nosuid SELinux domain transitions
As systemd ramps up enabling NNP (NoNewPrivileges) for system services,
it is increasingly breaking SELinux domain transitions for those services
and their descendants.  systemd enables NNP not only for services whose
unit files explicitly specify NoNewPrivileges=yes but also for services
whose unit files specify any of the following options in combination with
running without CAP_SYS_ADMIN (e.g. specifying User= or a
CapabilityBoundingSet= without CAP_SYS_ADMIN): SystemCallFilter=,
SystemCallArchitectures=, RestrictAddressFamilies=, RestrictNamespaces=,
PrivateDevices=, ProtectKernelTunables=, ProtectKernelModules=,
MemoryDenyWriteExecute=, or RestrictRealtime= as per the systemd.exec(5)
man page.

The end result is bad for the security of both SELinux-disabled and
SELinux-enabled systems.  Packagers have to turn off these
options in the unit files to preserve SELinux domain transitions.  For
users who choose to disable SELinux, this means that they miss out on
at least having the systemd-supported protections.  For users who keep
SELinux enabled, they may still be missing out on some protections
because it isn't necessarily guaranteed that the SELinux policy for
that service provides the same protections in all cases.

commit 7b0d0b40cd ("selinux: Permit bounded transitions under
NO_NEW_PRIVS or NOSUID.") allowed bounded transitions under NNP in
order to support limited usage for sandboxing programs.  However,
defining typebounds for all of the affected service domains
is impractical to implement in policy, since typebounds requires us
to ensure that each domain is allowed everything all of its descendant
domains are allowed, and this has to be repeated for the entire chain
of domain transitions.  There is no way to clone all allow rules from
descendants to their ancestors in policy currently, and doing so would
be undesirable even if it were practical, as it requires leaking
permissions to objects and operations into ancestor domains that could
weaken their own security in order to allow them to the descendants
(e.g. if a descendant requires execmem permission, then so do all of
its ancestors; if a descendant requires execute permission to a file,
then so do all of its ancestors; if a descendant requires read to a
symbolic link or temporary file, then so do all of its ancestors...).
SELinux domains are intentionally not hierarchical / bounded in this
manner normally, and making them so would undermine their protections
and least privilege.

We have long had a similar tension with SELinux transitions and nosuid
mounts, albeit not as severe.  Users often have had to choose between
retaining nosuid on a mount and allowing SELinux domain transitions on
files within those mounts.  This likewise leads to unfortunate tradeoffs
in security.

Decouple NNP/nosuid from SELinux transitions, so that we don't have to
make a choice between them. Introduce a nnp_nosuid_transition policy
capability that enables transitions under NNP/nosuid to be based on
a permission (nnp_transition for NNP; nosuid_transition for nosuid)
between the old and new contexts in addition to the current support
for bounded transitions.  Domain transitions can then be allowed in
policy without requiring the parent to be a strict superset of all of
its children.

With this change, systemd unit files can be left unmodified from upstream.
SELinux-disabled and SELinux-enabled users will benefit from retaining any
of the systemd-provided protections.  SELinux policy will only need to
be adapted to enable the new policy capability and to allow the
new permissions between domain pairs as appropriate.

NB: Allowing nnp_transition between two contexts opens up the potential
for the old context to subvert the new context by installing seccomp
filters before the execve.  Allowing nosuid_transition between two contexts
opens up the potential for a context transition to occur on a file from
an untrusted filesystem (e.g. removable media or remote filesystem).  Use
with care.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
2017-08-02 16:36:04 -04:00
Kees Cook 35b372b76f smack: Remove redundant pdeath_signal clearing
This removes the redundant pdeath_signal clearing in Smack: the check in
smack_bprm_committing_creds() matches the check in smack_bprm_set_creds()
(which used to be in the now-removed smack_bprm_securexec() hook) and
since secureexec is now being checked for clearing pdeath_signal, this
is redundant to the common exec code.

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
2017-08-01 12:03:12 -07:00