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 
12 u32 monitored_pid = 0;
13 
14 struct {
15 	__uint(type, BPF_MAP_TYPE_RINGBUF);
16 	__uint(max_entries, 1 << 12);
17 } ringbuf SEC(".maps");
18 
19 char _license[] SEC("license") = "GPL";
20 
21 bool use_ima_file_hash;
22 bool enable_bprm_creds_for_exec;
23 bool enable_kernel_read_file;
24 bool test_deny;
25 
26 static 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 
55 static 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 
66 SEC("lsm.s/bprm_committed_creds")
67 void BPF_PROG(bprm_committed_creds, struct linux_binprm *bprm)
68 {
69 	ima_test_common(bprm->file);
70 }
71 
72 SEC("lsm.s/bprm_creds_for_exec")
73 int 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 
82 SEC("lsm.s/kernel_read_file")
83 int 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