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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
[...]
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.
Sometimes capable catches itself starting up:
# ./capable.py
TIME UID PID COMM CAP NAME AUDIT
22:22:19 0 21949 capable.py 21 CAP_SYS_ADMIN 1
22:22:19 0 21949 capable.py 21 CAP_SYS_ADMIN 1
22:22:19 0 21949 capable.py 21 CAP_SYS_ADMIN 1
22:22:19 0 21949 capable.py 21 CAP_SYS_ADMIN 1
22:22:19 0 21949 capable.py 21 CAP_SYS_ADMIN 1
22:22:19 0 21949 capable.py 21 CAP_SYS_ADMIN 1
22:22:19 0 21952 run 24 CAP_SYS_RESOURCE 1
[...]
These are capability checks from BPF and perf_events syscalls.
USAGE:
# ./capable.py -h
usage: capable.py [-h] [-v] [-p PID]
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
examples:
./capable # trace capability checks
./capable -v # verbose: include non-audit checks
./capable -p 181 # only trace PID 181