capable_example.txt

Demonstrations of capable, the Linux eBPF/bcc version.

capable traces calls to the kernel cap_capable() function, which does security
capability checks, and prints details for each call. For example:

# ./capable.py
TIME      UID    PID    COMM             CAP  NAME                 AUDIT
22:11:23  114    2676   snmpd            12   CAP_NET_ADMIN        1
22:11:23  0      6990   run              24   CAP_SYS_RESOURCE     1
22:11:23  0      7003   chmod            3    CAP_FOWNER           1
22:11:23  0      7003   chmod            4    CAP_FSETID           1
22:11:23  0      7005   chmod            4    CAP_FSETID           1
22:11:23  0      7005   chmod            4    CAP_FSETID           1
22:11:23  0      7006   chown            4    CAP_FSETID           1
22:11:23  0      7006   chown            4    CAP_FSETID           1
22:11:23  0      6990   setuidgid        6    CAP_SETGID           1
22:11:23  0      6990   setuidgid        6    CAP_SETGID           1
22:11:23  0      6990   setuidgid        7    CAP_SETUID           1
22:11:24  0      7013   run              24   CAP_SYS_RESOURCE     1
22:11:24  0      7026   chmod            3    CAP_FOWNER           1
22:11:24  0      7026   chmod            4    CAP_FSETID           1
22:11:24  0      7028   chmod            4    CAP_FSETID           1
22:11:24  0      7028   chmod            4    CAP_FSETID           1
22:11:24  0      7029   chown            4    CAP_FSETID           1
22:11:24  0      7029   chown            4    CAP_FSETID           1
22:11:24  0      7013   setuidgid        6    CAP_SETGID           1
22:11:24  0      7013   setuidgid        6    CAP_SETGID           1
22:11:24  0      7013   setuidgid        7    CAP_SETUID           1
22:11:25  0      7036   run              24   CAP_SYS_RESOURCE     1
22:11:25  0      7049   chmod            3    CAP_FOWNER           1
22:11:25  0      7049   chmod            4    CAP_FSETID           1
22:11:25  0      7051   chmod            4    CAP_FSETID           1
22:11:25  0      7051   chmod            4    CAP_FSETID           1

Checks where AUDIT is 0 are ignored by default, which can be changed
with -v but is more verbose.

We can show the TID and INSETID columns with -x.
Since only a recent kernel version >= 5.1 reports the INSETID bit to cap_capable(),
the fallback value "N/A" will be displayed on older kernels.

# ./capable.py -x
TIME      UID    PID    TID    COMM             CAP  NAME                 AUDIT  INSETID
08:22:36  0      12869  12869  chown            0    CAP_CHOWN            1      0
08:22:36  0      12869  12869  chown            0    CAP_CHOWN            1      0
08:22:36  0      12869  12869  chown            0    CAP_CHOWN            1      0
08:23:02  0      13036  13036  setuidgid        6    CAP_SETGID           1      0
08:23:02  0      13036  13036  setuidgid        6    CAP_SETGID           1      0
08:23:02  0      13036  13036  setuidgid        7    CAP_SETUID           1      1
08:23:13  0      13085  13085  chmod            3    CAP_FOWNER           1      0
08:23:13  0      13085  13085  chmod            4    CAP_FSETID           1      0
08:23:13  0      13085  13085  chmod            3    CAP_FOWNER           1      0
08:23:13  0      13085  13085  chmod            4    CAP_FSETID           1      0
08:23:13  0      13085  13085  chmod            4    CAP_FSETID           1      0
08:24:27  0      13522  13522  ping             13   CAP_NET_RAW          1      0
[...]

This can be useful for general debugging, and also security enforcement:
determining a whitelist of capabilities an application needs.

The output above includes various capability checks: snmpd checking
CAP_NET_ADMIN, run checking CAP_SYS_RESOURCES, then some short-lived processes
checking CAP_FOWNER, CAP_FSETID, etc.

To see what each of these capabilities does, check the capabilities(7) man
page and the kernel source.

It is possible to include a kernel stack trace to the capable events by passing
-K to the command:

# ./capable.py -K
TIME      UID    PID    COMM             CAP  NAME                 AUDIT
15:32:21  1000   10708  fetchmail        7    CAP_SETUID           1
        cap_capable+0x1 [kernel]
        ns_capable_common+0x7a [kernel]
        __sys_setresuid+0xc8 [kernel]
        do_syscall_64+0x56 [kernel]
        entry_SYSCALL_64_after_hwframe+0x49 [kernel]
15:32:21  1000   30047  procmail         6    CAP_SETGID           1
        cap_capable+0x1 [kernel]
        ns_capable_common+0x7a [kernel]
        may_setgroups+0x2f [kernel]
        __x64_sys_setgroups+0x18 [kernel]
        do_syscall_64+0x56 [kernel]
        entry_SYSCALL_64_after_hwframe+0x49 [kernel]

Similarly, it is possible to include user-space stack with -U (or they can be
used both at the same time to include user and kernel stack).

Some processes can do a lot of security capability checks, generating a lot of
ouput. In this case, the --unique option is useful to only print once the same
set of capability, pid (or cgroup if --cgroupmap is used) and kernel/user
stacks (if -K or -U are used).

# ./capable.py -K -U --unique

The --cgroupmap option filters based on a cgroup set. It is meant to be used
with an externally created map.

# ./capable.py --cgroupmap /sys/fs/bpf/test01

For more details, see docs/special_filtering.md

USAGE:

# ./capable.py -h
usage: capable.py [-h] [-v] [-p PID] [-K] [-U] [-x] [--cgroupmap CGROUPMAP]
                  [--mntnsmap MNTNSMAP] [--unique]

Trace security capability checks

optional arguments:
  -h, --help            show this help message and exit
  -v, --verbose         include non-audit checks
  -p PID, --pid PID     trace this PID only
  -K, --kernel-stack    output kernel stack trace
  -U, --user-stack      output user stack trace
  -x, --extra           show extra fields in TID and INSETID columns
  --cgroupmap CGROUPMAP
                        trace cgroups in this BPF map only
  --mntnsmap MNTNSMAP   trace mount namespaces in this BPF map only
  --unique              don't repeat stacks for the same pid or cgroup

examples:
    ./capable             # trace capability checks
    ./capable -v          # verbose: include non-audit checks
    ./capable -p 181      # only trace PID 181
    ./capable -K          # add kernel stacks to trace
    ./capable -U          # add user-space stacks to trace
    ./capable -x          # extra fields: show TID and INSETID columns
    ./capable --unique    # don't repeat stacks for the same pid or cgroup
    ./capable --cgroupmap mappath  # only trace cgroups in this BPF map
    ./capable --mntnsmap mappath   # only trace mount namespaces in the map

docroot: /var/www/469ed2f6-4d4b-4a8a-9f5e-ee4ef04d3bc8/public_html

curdir: /usr/share/doc/bpfcc-tools/examples/doc

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X	bindsnoop_example.txt	4530
X	biolatency_example.txt	24021
X	biolatpcts_example.txt	3040
X	biopattern_example.txt	1406
X	biosnoop_example.txt	3549
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X	bitesize_example.txt	5100
X	bpflist_example.txt	2179
X	btrfsdist_example.txt	9545
X	btrfsslower_example.txt	6812
X	cachestat_example.txt	4012
X	cachetop_example.txt	3918
X	capable_example.txt	6655
X	cobjnew_example.txt	3044
X	compactsnoop_example.txt	10160
X	cpudist_example.txt	16876
X	cpuunclaimed_example.txt	15568
X	criticalstat_example.txt	4926
X	cthreads_example.txt	2132
X	dbslower_example.txt	3981
X	dbstat_example.txt	6656
X	dcsnoop_example.txt	4371
X	dcstat_example.txt	3343
X	deadlock_example.txt	16643
X	dirtop_example.txt	5097
X	drsnoop_example.txt	5120
X	execsnoop_example.txt	6795
X	exitsnoop_example.txt	6373
X	ext4dist_example.txt	8991
X	ext4slower_example.txt	11335
X	filegone_example.txt	743
X	filelife_example.txt	2092
X	fileslower_example.txt	5711
X	filetop_example.txt	6968
X	funccount_example.txt	13605
X	funcinterval_example.txt	15646
X	funclatency_example.txt	21485
X	funcslower_example.txt	6786
X	gethostlatency_example.txt	1317
X	hardirqs_example.txt	37936
X	inject_example.txt	6832
X	javacalls_example.txt	4000
X	javaflow_example.txt	6017
X	javagc_example.txt	3867
X	javaobjnew_example.txt	3044
X	javastat_example.txt	3052
X	javathreads_example.txt	2132
X	killsnoop_example.txt	1339
X	klockstat_example.txt	8536
X	kvmexit_example.txt	11909
	lib	4096
X	llcstat_example.txt	3315
X	mdflush_example.txt	1780
X	memleak_example.txt	10263
X	mountsnoop_example.txt	1481
X	mysqld_qslower_example.txt	2351
X	netqtop_example.txt	12497
X	nfsdist_example.txt	8508
X	nfsslower_example.txt	7867
X	nodegc_example.txt	3867
X	nodestat_example.txt	3052
X	offcputime_example.txt	19662
X	offwaketime_example.txt	38258
X	oomkill_example.txt	1925
X	opensnoop_example.txt	10573
X	perlcalls_example.txt	4000
X	perlflow_example.txt	6017
X	perlstat_example.txt	3052
X	phpcalls_example.txt	4000
X	phpflow_example.txt	6017
X	phpstat_example.txt	3052
X	pidpersec_example.txt	677
X	ppchcalls_example.txt	7097
X	profile_example.txt	31826
X	pythoncalls_example.txt	4000
X	pythonflow_example.txt	6017
X	pythongc_example.txt	3867
X	pythonstat_example.txt	3052
X	rdmaucma_example.txt	1983
X	readahead_example.txt	3248
X	reset-trace_example.txt	9365
X	rubycalls_example.txt	4000
X	rubyflow_example.txt	6017
X	rubygc_example.txt	3867
X	rubyobjnew_example.txt	3044
X	rubystat_example.txt	3052
X	runqlat_example.txt	32051
X	runqlen_example.txt	12136
X	runqslower_example.txt	2184
X	shmsnoop_example.txt	2798
X	slabratetop_example.txt	5347
X	sofdsnoop_example.txt	3211
X	softirqs_example.txt	11286
X	solisten_example.txt	2355
X	sslsniff_example.txt	6902
X	stackcount_example.txt	21965
X	statsnoop_example.txt	3091
X	swapin.txt	2632
X	swapin_example.txt	1421
X	syncsnoop_example.txt	387
X	syscount_example.txt	6419
X	tclcalls_example.txt	4000
X	tclflow_example.txt	6017
X	tclobjnew_example.txt	3044
X	tclstat_example.txt	3052
X	tcpaccept_example.txt	2822
X	tcpcong_example.txt	34106
X	tcpconnect_example.txt	6420
X	tcpconnlat_example.txt	2616
X	tcpdrop_example.txt	2001
X	tcplife_example.txt	6995
X	tcpretrans_example.txt	3938
X	tcprtt_example.txt	10070
X	tcpstates_example.txt	2908
X	tcpsubnet_example.txt	5503
X	tcpsynbl_example.txt	1179
X	tcptop_example.txt	5890
X	tcptracer_example.txt	2029
X	threadsnoop_example.txt	1094
X	tplist_example.txt	4507
X	trace_example.txt	22136
X	ttysnoop_example.txt	3315
X	vfscount_example.txt	2221
X	vfsstat_example.txt	1696
X	virtiostat_example.txt	2678
X	wakeuptime_example.txt	34048
X	xfsdist_example.txt	6928
X	xfsslower_example.txt	7080
X	zfsdist_example.txt	9753
X	zfsslower_example.txt	7551