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#!/usr/bin/python
# @lint-avoid-python-3-compatibility-imports
#
# capable Trace security capabilitiy checks (cap_capable()).
# For Linux, uses BCC, eBPF. Embedded C.
#
# USAGE: capable [-h] [-v] [-p PID]
#
# ToDo: add -s for kernel stacks.
#
# Copyright 2016 Netflix, Inc.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 13-Sep-2016 Brendan Gregg Created this.
from __future__ import print_function
from bcc import BPF
import argparse
from time import strftime
import ctypes as ct
# arguments
examples = """examples:
./capable # trace capability checks
./capable -v # verbose: include non-audit checks
./capable -p 181 # only trace PID 181
"""
parser = argparse.ArgumentParser(
description="Trace security capability checks",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-v", "--verbose", action="store_true",
help="include non-audit checks")
parser.add_argument("-p", "--pid",
help="trace this PID only")
args = parser.parse_args()
debug = 0
# capabilities to names, generated from (and will need updating):
# awk '/^#define.CAP_.*[0-9]$/ { print " " $3 ": \"" $2 "\"," }' \
# include/uapi/linux/capability.h
capabilities = {
0: "CAP_CHOWN",
1: "CAP_DAC_OVERRIDE",
2: "CAP_DAC_READ_SEARCH",
3: "CAP_FOWNER",
4: "CAP_FSETID",
5: "CAP_KILL",
6: "CAP_SETGID",
7: "CAP_SETUID",
8: "CAP_SETPCAP",
9: "CAP_LINUX_IMMUTABLE",
10: "CAP_NET_BIND_SERVICE",
11: "CAP_NET_BROADCAST",
12: "CAP_NET_ADMIN",
13: "CAP_NET_RAW",
14: "CAP_IPC_LOCK",
15: "CAP_IPC_OWNER",
16: "CAP_SYS_MODULE",
17: "CAP_SYS_RAWIO",
18: "CAP_SYS_CHROOT",
19: "CAP_SYS_PTRACE",
20: "CAP_SYS_PACCT",
21: "CAP_SYS_ADMIN",
22: "CAP_SYS_BOOT",
23: "CAP_SYS_NICE",
24: "CAP_SYS_RESOURCE",
25: "CAP_SYS_TIME",
26: "CAP_SYS_TTY_CONFIG",
27: "CAP_MKNOD",
28: "CAP_LEASE",
29: "CAP_AUDIT_WRITE",
30: "CAP_AUDIT_CONTROL",
31: "CAP_SETFCAP",
32: "CAP_MAC_OVERRIDE",
33: "CAP_MAC_ADMIN",
34: "CAP_SYSLOG",
35: "CAP_WAKE_ALARM",
36: "CAP_BLOCK_SUSPEND",
37: "CAP_AUDIT_READ",
}
# define BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
#include <linux/sched.h>
struct data_t {
// switch to u32s when supported
u64 pid;
u64 uid;
int cap;
int audit;
char comm[TASK_COMM_LEN];
};
BPF_PERF_OUTPUT(events);
int kprobe__cap_capable(struct pt_regs *ctx, const struct cred *cred,
struct user_namespace *targ_ns, int cap, int audit)
{
u32 pid = bpf_get_current_pid_tgid();
FILTER1
FILTER2
u32 uid = bpf_get_current_uid_gid();
struct data_t data = {.pid = pid, .uid = uid, .cap = cap, .audit = audit};
bpf_get_current_comm(&data.comm, sizeof(data.comm));
events.perf_submit(ctx, &data, sizeof(data));
return 0;
};
"""
if args.pid:
bpf_text = bpf_text.replace('FILTER1',
'if (pid != %s) { return 0; }' % args.pid)
if not args.verbose:
bpf_text = bpf_text.replace('FILTER2', 'if (audit == 0) { return 0; }')
bpf_text = bpf_text.replace('FILTER1', '')
bpf_text = bpf_text.replace('FILTER2', '')
if debug:
print(bpf_text)
# initialize BPF
b = BPF(text=bpf_text)
TASK_COMM_LEN = 16 # linux/sched.h
class Data(ct.Structure):
_fields_ = [
("pid", ct.c_ulonglong),
("uid", ct.c_ulonglong),
("cap", ct.c_int),
("audit", ct.c_int),
("comm", ct.c_char * TASK_COMM_LEN)
]
# header
print("%-9s %-6s %-6s %-16s %-4s %-20s %s" % (
"TIME", "UID", "PID", "COMM", "CAP", "NAME", "AUDIT"))
# process event
def print_event(cpu, data, size):
event = ct.cast(data, ct.POINTER(Data)).contents
if event.cap in capabilities:
name = capabilities[event.cap]
else:
name = "?"
print("%-9s %-6d %-6d %-16s %-4d %-20s %d" % (strftime("%H:%M:%S"),
event.uid, event.pid, event.comm, event.cap, name, event.audit))
# loop with callback to print_event
b["events"].open_perf_buffer(print_event)
while 1:
b.kprobe_poll()