linux-toradex.git/security/integrity/ima, branch v3.16-rc7

ima: introduce ima_kernel_read()

2014-06-12T21:58:08+00:00

Commit 8aac62706 "move exit_task_namespaces() outside of exit_notify"
introduced the kernel opps since the kernel v3.10, which happens when
Apparmor and IMA-appraisal are enabled at the same time.

----------------------------------------------------------------------
[  106.750167] BUG: unable to handle kernel NULL pointer dereference at
0000000000000018
[  106.750221] IP: [] our_mnt+0x1a/0x30
[  106.750241] PGD 0
[  106.750254] Oops: 0000 [#1] SMP
[  106.750272] Modules linked in: cuse parport_pc ppdev bnep rfcomm
bluetooth rpcsec_gss_krb5 nfsd auth_rpcgss nfs_acl nfs lockd sunrpc
fscache dm_crypt intel_rapl x86_pkg_temp_thermal intel_powerclamp
kvm_intel snd_hda_codec_hdmi kvm crct10dif_pclmul crc32_pclmul
ghash_clmulni_intel aesni_intel aes_x86_64 glue_helper lrw gf128mul
ablk_helper cryptd snd_hda_codec_realtek dcdbas snd_hda_intel
snd_hda_codec snd_hwdep snd_pcm snd_page_alloc snd_seq_midi
snd_seq_midi_event snd_rawmidi psmouse snd_seq microcode serio_raw
snd_timer snd_seq_device snd soundcore video lpc_ich coretemp mac_hid lp
parport mei_me mei nbd hid_generic e1000e usbhid ahci ptp hid libahci
pps_core
[  106.750658] CPU: 6 PID: 1394 Comm: mysqld Not tainted 3.13.0-rc7-kds+ #15
[  106.750673] Hardware name: Dell Inc. OptiPlex 9010/0M9KCM, BIOS A08
09/19/2012
[  106.750689] task: ffff8800de804920 ti: ffff880400fca000 task.ti:
ffff880400fca000
[  106.750704] RIP: 0010:[]  []
our_mnt+0x1a/0x30
[  106.750725] RSP: 0018:ffff880400fcba60  EFLAGS: 00010286
[  106.750738] RAX: 0000000000000000 RBX: 0000000000000100 RCX:
ffff8800d51523e7
[  106.750764] RDX: ffffffffffffffea RSI: ffff880400fcba34 RDI:
ffff880402d20020
[  106.750791] RBP: ffff880400fcbae0 R08: 0000000000000000 R09:
0000000000000001
[  106.750817] R10: 0000000000000000 R11: 0000000000000001 R12:
ffff8800d5152300
[  106.750844] R13: ffff8803eb8df510 R14: ffff880400fcbb28 R15:
ffff8800d51523e7
[  106.750871] FS:  0000000000000000(0000) GS:ffff88040d200000(0000)
knlGS:0000000000000000
[  106.750910] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  106.750935] CR2: 0000000000000018 CR3: 0000000001c0e000 CR4:
00000000001407e0
[  106.750962] Stack:
[  106.750981]  ffffffff813434eb ffff880400fcbb20 ffff880400fcbb18
0000000000000000
[  106.751037]  ffff8800de804920 ffffffff8101b9b9 0001800000000000
0000000000000100
[  106.751093]  0000010000000000 0000000000000002 000000000000000e
ffff8803eb8df500
[  106.751149] Call Trace:
[  106.751172]  [] ? aa_path_name+0x2ab/0x430
[  106.751199]  [] ? sched_clock+0x9/0x10
[  106.751225]  [] aa_path_perm+0x7d/0x170
[  106.751250]  [] ? native_sched_clock+0x15/0x80
[  106.751276]  [] aa_file_perm+0x33/0x40
[  106.751301]  [] common_file_perm+0x8e/0xb0
[  106.751327]  [] apparmor_file_permission+0x18/0x20
[  106.751355]  [] security_file_permission+0x23/0xa0
[  106.751382]  [] rw_verify_area+0x52/0xe0
[  106.751407]  [] vfs_read+0x6d/0x170
[  106.751432]  [] kernel_read+0x41/0x60
[  106.751457]  [] ima_calc_file_hash+0x225/0x280
[  106.751483]  [] ? ima_calc_file_hash+0x32/0x280
[  106.751509]  [] ima_collect_measurement+0x9d/0x160
[  106.751536]  [] ? trace_hardirqs_on+0xd/0x10
[  106.751562]  [] ? ima_file_free+0x6c/0xd0
[  106.751587]  [] ima_update_xattr+0x34/0x60
[  106.751612]  [] ima_file_free+0xc0/0xd0
[  106.751637]  [] __fput+0xd5/0x300
[  106.751662]  [] ____fput+0xe/0x10
[  106.751687]  [] task_work_run+0xc4/0xe0
[  106.751712]  [] do_exit+0x2bd/0xa90
[  106.751738]  [] ? retint_swapgs+0x13/0x1b
[  106.751763]  [] do_group_exit+0x4c/0xc0
[  106.751788]  [] SyS_exit_group+0x14/0x20
[  106.751814]  [] system_call_fastpath+0x1a/0x1f
[  106.751839] Code: c3 0f 1f 44 00 00 55 48 89 e5 e8 22 fe ff ff 5d c3
0f 1f 44 00 00 55 65 48 8b 04 25 c0 c9 00 00 48 8b 80 28 06 00 00 48 89
e5 5d <48> 8b 40 18 48 39 87 c0 00 00 00 0f 94 c0 c3 0f 1f 80 00 00 00
[  106.752185] RIP  [] our_mnt+0x1a/0x30
[  106.752214]  RSP 
[  106.752236] CR2: 0000000000000018
[  106.752258] ---[ end trace 3c520748b4732721 ]---
----------------------------------------------------------------------

The reason for the oops is that IMA-appraisal uses "kernel_read()" when
file is closed. kernel_read() honors LSM security hook which calls
Apparmor handler, which uses current->nsproxy->mnt_ns. The 'guilty'
commit changed the order of cleanup code so that nsproxy->mnt_ns was
not already available for Apparmor.

Discussion about the issue with Al Viro and Eric W. Biederman suggested
that kernel_read() is too high-level for IMA. Another issue, except
security checking, that was identified is mandatory locking. kernel_read
honors it as well and it might prevent IMA from calculating necessary hash.
It was suggested to use simplified version of the function without security
and locking checks.

This patch introduces special version ima_kernel_read(), which skips security
and mandatory locking checking. It prevents the kernel oops to happen.

Signed-off-by: Dmitry Kasatkin 
Suggested-by: Eric W. Biederman 
Signed-off-by: Mimi Zohar 
Cc:

ima: check inode integrity cache in violation check

2014-06-12T21:58:07+00:00

When IMA did not support ima-appraisal, existance of the S_IMA flag
clearly indicated that the file was measured. With IMA appraisal S_IMA
flag indicates that file was measured and/or appraised. Because of
this, when measurement is not enabled by the policy, violations are
still reported.

To differentiate between measurement and appraisal policies this
patch checks the inode integrity cache flags.  The IMA_MEASURED
flag indicates whether the file was actually measured, while the
IMA_MEASURE flag indicates whether the file should be measured.
Unfortunately, the IMA_MEASURED flag is reset to indicate the file
needs to be re-measured.  Thus, this patch checks the IMA_MEASURE
flag.

This patch limits the false positive violation reports, but does
not fix it entirely.  The IMA_MEASURE/IMA_MEASURED flags are
indications that, at some point in time, the file opened for read
was in policy, but might not be in policy now (eg. different uid).
Other changes would be needed to further limit false positive
violation reports.

Changelog:
- expanded patch description based on conversation with Roberto (Mimi)

Signed-off-by: Dmitry Kasatkin 
Signed-off-by: Mimi Zohar

ima: prevent unnecessary policy checking

2014-06-12T21:58:06+00:00

ima_rdwr_violation_check is called for every file openning.
The function checks the policy even when violation condition
is not met. It causes unnecessary policy checking.

This patch does policy checking only if violation condition is met.

Changelog:
- check writecount is greater than zero (Mimi)

Signed-off-by: Dmitry Kasatkin 
Signed-off-by: Mimi Zohar

ima: prevent new digsig xattr from being replaced

2014-06-12T21:58:05+00:00

Even though a new xattr will only be appraised on the next access,
set the DIGSIG flag to prevent a signature from being replaced with
a hash on file close.

Signed-off-by: Mimi Zohar

ima: audit log files opened with O_DIRECT flag

2014-06-03T19:21:50+00:00

Files are measured or appraised based on the IMA policy.  When a
file, in policy, is opened with the O_DIRECT flag, a deadlock
occurs.

The first attempt at resolving this lockdep temporarily removed the
O_DIRECT flag and restored it, after calculating the hash.  The
second attempt introduced the O_DIRECT_HAVELOCK flag. Based on this
flag, do_blockdev_direct_IO() would skip taking the i_mutex a second
time.  The third attempt, by Dmitry Kasatkin, resolves the i_mutex
locking issue, by re-introducing the IMA mutex, but uncovered
another problem.  Reading a file with O_DIRECT flag set, writes
directly to userspace pages.  A second patch allocates a user-space
like memory.  This works for all IMA hooks, except ima_file_free(),
which is called on __fput() to recalculate the file hash.

Until this last issue is addressed, do not 'collect' the
measurement for measuring, appraising, or auditing files opened
with the O_DIRECT flag set.  Based on policy, permit or deny file
access.  This patch defines a new IMA policy rule option named
'permit_directio'.  Policy rules could be defined, based on LSM
or other criteria, to permit specific applications to open files
with the O_DIRECT flag set.

Changelog v1:
- permit or deny file access based IMA policy rules

Signed-off-by: Mimi Zohar 
Acked-by: Dmitry Kasatkin 
Cc:

ima: skip memory allocation for empty files

2014-03-07T17:15:48+00:00

Memory allocation is unnecessary for empty files.
This patch calculates the hash without memory allocation.

Signed-off-by: Dmitry Kasatkin 
Signed-off-by: Mimi Zohar

ima: return d_name.name if d_path fails

2014-03-07T17:15:46+00:00

This is a small refactoring so ima_d_path() returns dentry name
if path reconstruction fails. It simplifies callers actions
and removes code duplication.

Signed-off-by: Dmitry Kasatkin 
Signed-off-by: Mimi Zohar

integrity: fix checkpatch errors

2014-03-07T17:15:45+00:00

Between checkpatch changes (eg. sizeof) and inconsistencies between
Lindent and checkpatch, unfixed checkpatch errors make it difficult
to see new errors. This patch fixes them. Some lines with over 80 chars
remained unchanged to improve code readability.

The "extern" keyword is removed from internal evm.h to make it consistent
with internal ima.h.

Signed-off-by: Dmitry Kasatkin 
Signed-off-by: Mimi Zohar

ima: fix erroneous removal of security.ima xattr

2014-03-07T17:15:44+00:00

ima_inode_post_setattr() calls ima_must_appraise() to check if the
file needs to be appraised. If it does not then it removes security.ima
xattr. With original policy matching code it might happen that even
file needs to be appraised with FILE_CHECK hook, it might not be
for POST_SETATTR hook. 'security.ima' might be erronously removed.

This patch treats POST_SETATTR as special wildcard function and will
cause ima_must_appraise() to be true if any of the hooks rules matches.
security.ima will not be removed if any of the hooks would require
appraisal.

Signed-off-by: Dmitry Kasatkin 
Signed-off-by: Mimi Zohar

security: integrity: Use a more current logging style

2014-03-07T17:15:21+00:00

Convert printks to pr_.
Add pr_fmt.
Remove embedded prefixes.

Signed-off-by: Joe Perches 
Signed-off-by: Mimi Zohar