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
 9char _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
17char expected_digest[SIZEOF_STRUCT_FSVERITY_DIGEST + SHA256_DIGEST_SIZE];
18char digest[SIZEOF_STRUCT_FSVERITY_DIGEST + SHA256_DIGEST_SIZE];
19__u32 monitored_pid;
20__u32 got_fsverity;
21__u32 digest_matches;
22
23SEC("lsm.s/file_open")
24int 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}