1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
3
4 #include "vmlinux.h"
5 #include <bpf/bpf_helpers.h>
6 #include <bpf/bpf_tracing.h>
7 #include "bpf_kfuncs.h"
8
9 char _license[] SEC("license") = "GPL";
10
11 #ifndef SHA256_DIGEST_SIZE
12 #define SHA256_DIGEST_SIZE 32
13 #endif
14
15 #define SIZEOF_STRUCT_FSVERITY_DIGEST 4 /* sizeof(struct fsverity_digest) */
16
17 char expected_digest[SIZEOF_STRUCT_FSVERITY_DIGEST + SHA256_DIGEST_SIZE];
18 char digest[SIZEOF_STRUCT_FSVERITY_DIGEST + SHA256_DIGEST_SIZE];
19 __u32 monitored_pid;
20 __u32 got_fsverity;
21 __u32 digest_matches;
22
23 SEC("lsm.s/file_open")
24 int BPF_PROG(test_file_open, struct file *f)
25 {
26 struct bpf_dynptr digest_ptr;
27 __u32 pid;
28 int ret;
29 int i;
30
31 pid = bpf_get_current_pid_tgid() >> 32;
32 if (pid != monitored_pid)
33 return 0;
34
35 bpf_dynptr_from_mem(digest, sizeof(digest), 0, &digest_ptr);
36 ret = bpf_get_fsverity_digest(f, &digest_ptr);
37 if (ret < 0)
38 return 0;
39 got_fsverity = 1;
40
41 for (i = 0; i < (int)sizeof(digest); i++) {
42 if (digest[i] != expected_digest[i])
43 return 0;
44 }
45
46 digest_matches = 1;
47 return 0;
48 }
49
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