1// SPDX-License-Identifier: GPL-2.0
2
3/*
4 * Copyright 2020 Google LLC.
5 */
6
7#include "vmlinux.h"
8#include <errno.h>
9#include <bpf/bpf_helpers.h>
10#include <bpf/bpf_tracing.h>
11
12u32 monitored_pid = 0;
13
14struct {
15	__uint(type, BPF_MAP_TYPE_RINGBUF);
16	__uint(max_entries, 1 << 12);
17} ringbuf SEC(".maps");
18
19char _license[] SEC("license") = "GPL";
20
21bool use_ima_file_hash;
22bool enable_bprm_creds_for_exec;
23bool enable_kernel_read_file;
24bool test_deny;
25
26static void ima_test_common(struct file *file)
27{
28	u64 ima_hash = 0;
29	u64 *sample;
30	int ret;
31	u32 pid;
32
33	pid = bpf_get_current_pid_tgid() >> 32;
34	if (pid == monitored_pid) {
35		if (!use_ima_file_hash)
36			ret = bpf_ima_inode_hash(file->f_inode, &ima_hash,
37						 sizeof(ima_hash));
38		else
39			ret = bpf_ima_file_hash(file, &ima_hash,
40						sizeof(ima_hash));
41		if (ret < 0 || ima_hash == 0)
42			return;
43
44		sample = bpf_ringbuf_reserve(&ringbuf, sizeof(u64), 0);
45		if (!sample)
46			return;
47
48		*sample = ima_hash;
49		bpf_ringbuf_submit(sample, 0);
50	}
51
52	return;
53}
54
55static int ima_test_deny(void)
56{
57	u32 pid;
58
59	pid = bpf_get_current_pid_tgid() >> 32;
60	if (pid == monitored_pid && test_deny)
61		return -EPERM;
62
63	return 0;
64}
65
66SEC("lsm.s/bprm_committed_creds")
67void BPF_PROG(bprm_committed_creds, struct linux_binprm *bprm)
68{
69	ima_test_common(bprm->file);
70}
71
72SEC("lsm.s/bprm_creds_for_exec")
73int BPF_PROG(bprm_creds_for_exec, struct linux_binprm *bprm)
74{
75	if (!enable_bprm_creds_for_exec)
76		return 0;
77
78	ima_test_common(bprm->file);
79	return 0;
80}
81
82SEC("lsm.s/kernel_read_file")
83int BPF_PROG(kernel_read_file, struct file *file, enum kernel_read_file_id id,
84	     bool contents)
85{
86	int ret;
87
88	if (!enable_kernel_read_file)
89		return 0;
90
91	if (!contents)
92		return 0;
93
94	if (id != READING_POLICY)
95		return 0;
96
97	ret = ima_test_deny();
98	if (ret < 0)
99		return ret;
100
101	ima_test_common(file);
102	return 0;
103}
104