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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] [-K] [-U]
#
# 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 os import getpid
from functools import partial
from bcc import BPF
import errno
import argparse
from time import strftime
# arguments
examples = """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
"""
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")
parser.add_argument("-K", "--kernel-stack", action="store_true",
help="output kernel stack trace")
parser.add_argument("-U", "--user-stack", action="store_true",
help="output user stack trace")
parser.add_argument("-x", "--extra", action="store_true",
help="show extra fields in TID and INSETID columns")
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",
}
class Enum(set):
def __getattr__(self, name):
if name in self:
return name
raise AttributeError
# Stack trace types
StackType = Enum(("Kernel", "User",))
# define BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
#include <linux/sched.h>
#include <linux/security.h>
struct data_t {
u32 tgid;
u32 pid;
u32 uid;
int cap;
int audit;
int insetid;
char comm[TASK_COMM_LEN];
#ifdef KERNEL_STACKS
int kernel_stack_id;
#endif
#ifdef USER_STACKS
int user_stack_id;
#endif
};
BPF_PERF_OUTPUT(events);
#if defined(USER_STACKS) || defined(KERNEL_STACKS)
BPF_STACK_TRACE(stacks, 2048);
#endif
int kprobe__cap_capable(struct pt_regs *ctx, const struct cred *cred,
struct user_namespace *targ_ns, int cap, int cap_opt)
{
u64 __pid_tgid = bpf_get_current_pid_tgid();
u32 tgid = __pid_tgid >> 32;
u32 pid = __pid_tgid;
int audit;
int insetid;
#ifdef CAP_OPT_NONE
audit = (cap_opt & 0b10) == 0;
insetid = (cap_opt & 0b100) != 0;
#else
audit = cap_opt;
insetid = -1;
#endif
FILTER1
FILTER2
FILTER3
u32 uid = bpf_get_current_uid_gid();
struct data_t data = {.tgid = tgid, .pid = pid, .uid = uid, .cap = cap, .audit = audit, .insetid = insetid};
#ifdef KERNEL_STACKS
data.kernel_stack_id = stacks.get_stackid(ctx, 0);
#endif
#ifdef USER_STACKS
data.user_stack_id = stacks.get_stackid(ctx, BPF_F_USER_STACK);
#endif
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; }')
if args.kernel_stack:
bpf_text = "#define KERNEL_STACKS\n" + bpf_text
if args.user_stack:
bpf_text = "#define USER_STACKS\n" + bpf_text
bpf_text = bpf_text.replace('FILTER1', '')
bpf_text = bpf_text.replace('FILTER2', '')
bpf_text = bpf_text.replace('FILTER3',
'if (pid == %s) { return 0; }' % getpid())
if debug:
print(bpf_text)
# initialize BPF
b = BPF(text=bpf_text)
# header
if args.extra:
print("%-9s %-6s %-6s %-6s %-16s %-4s %-20s %-6s %s" % (
"TIME", "UID", "PID", "TID", "COMM", "CAP", "NAME", "AUDIT", "INSETID"))
else:
print("%-9s %-6s %-6s %-16s %-4s %-20s %-6s" % (
"TIME", "UID", "PID", "COMM", "CAP", "NAME", "AUDIT"))
def stack_id_err(stack_id):
# -EFAULT in get_stackid normally means the stack-trace is not availible,
# Such as getting kernel stack trace in userspace code
return (stack_id < 0) and (stack_id != -errno.EFAULT)
def print_stack(bpf, stack_id, stack_type, tgid):
if stack_id_err(stack_id):
print(" [Missed %s Stack]" % stack_type)
return
stack = list(bpf.get_table("stacks").walk(stack_id))
for addr in stack:
print(" ", end="")
print("%s" % (bpf.sym(addr, tgid, show_module=True, show_offset=True)))
# process event
def print_event(bpf, cpu, data, size):
event = b["events"].event(data)
if event.cap in capabilities:
name = capabilities[event.cap]
else:
name = "?"
if args.extra:
print("%-9s %-6d %-6d %-6d %-16s %-4d %-20s %-6d %s" % (strftime("%H:%M:%S"),
event.uid, event.pid, event.tgid, event.comm.decode('utf-8', 'replace'),
event.cap, name, event.audit, str(event.insetid) if event.insetid != -1 else "N/A"))
else:
print("%-9s %-6d %-6d %-16s %-4d %-20s %-6d" % (strftime("%H:%M:%S"),
event.uid, event.pid, event.comm.decode('utf-8', 'replace'),
event.cap, name, event.audit))
if args.kernel_stack:
print_stack(bpf, event.kernel_stack_id, StackType.Kernel, -1)
if args.user_stack:
print_stack(bpf, event.user_stack_id, StackType.User, event.tgid)
# loop with callback to print_event
callback = partial(print_event, b)
b["events"].open_perf_buffer(callback)
while 1:
try:
b.perf_buffer_poll()
except KeyboardInterrupt:
exit()
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