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
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