capable_example.txt

Demonstrations of capable, the Linux bpftrace/eBPF version.


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

# ./capable.bt
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.


There is another version of this tool in bcc: https://github.com/iovisor/bcc
The bcc version provides options to customize the output.