1 // SPDX-License-Identifier: GPL-2.0
2
3 /*
4 * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH
5 *
6 * Author: Roberto Sassu <roberto.sassu@huawei.com>
7 */
8
9 #include "vmlinux.h"
10 #include <errno.h>
11 #include <bpf/bpf_helpers.h>
12 #include <bpf/bpf_tracing.h>
13 #include "bpf_misc.h"
14
15 extern struct bpf_key *bpf_lookup_system_key(__u64 id) __ksym;
16 extern void bpf_key_put(struct bpf_key *key) __ksym;
17 extern int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_ptr,
18 struct bpf_dynptr *sig_ptr,
19 struct bpf_key *trusted_keyring) __ksym;
20
21 struct {
22 __uint(type, BPF_MAP_TYPE_RINGBUF);
23 __uint(max_entries, 4096);
24 } ringbuf SEC(".maps");
25
26 struct {
27 __uint(type, BPF_MAP_TYPE_ARRAY);
28 __uint(max_entries, 1);
29 __type(key, __u32);
30 __type(value, __u32);
31 } array_map SEC(".maps");
32
33 int err, pid;
34
35 char _license[] SEC("license") = "GPL";
36
37 SEC("?lsm.s/bpf")
38 __failure __msg("cannot pass in dynptr at an offset=-8")
BPF_PROG(not_valid_dynptr,int cmd,union bpf_attr * attr,unsigned int size)39 int BPF_PROG(not_valid_dynptr, int cmd, union bpf_attr *attr, unsigned int size)
40 {
41 unsigned long val;
42
43 return bpf_verify_pkcs7_signature((struct bpf_dynptr *)&val,
44 (struct bpf_dynptr *)&val, NULL);
45 }
46
47 SEC("?lsm.s/bpf")
48 __failure __msg("arg#0 expected pointer to stack or dynptr_ptr")
BPF_PROG(not_ptr_to_stack,int cmd,union bpf_attr * attr,unsigned int size)49 int BPF_PROG(not_ptr_to_stack, int cmd, union bpf_attr *attr, unsigned int size)
50 {
51 unsigned long val = 0;
52
53 return bpf_verify_pkcs7_signature((struct bpf_dynptr *)val,
54 (struct bpf_dynptr *)val, NULL);
55 }
56
57 SEC("lsm.s/bpf")
BPF_PROG(dynptr_data_null,int cmd,union bpf_attr * attr,unsigned int size)58 int BPF_PROG(dynptr_data_null, int cmd, union bpf_attr *attr, unsigned int size)
59 {
60 struct bpf_key *trusted_keyring;
61 struct bpf_dynptr ptr;
62 __u32 *value;
63 int ret, zero = 0;
64
65 if (bpf_get_current_pid_tgid() >> 32 != pid)
66 return 0;
67
68 value = bpf_map_lookup_elem(&array_map, &zero);
69 if (!value)
70 return 0;
71
72 /* Pass invalid flags. */
73 ret = bpf_dynptr_from_mem(value, sizeof(*value), ((__u64)~0ULL), &ptr);
74 if (ret != -EINVAL)
75 return 0;
76
77 trusted_keyring = bpf_lookup_system_key(0);
78 if (!trusted_keyring)
79 return 0;
80
81 err = bpf_verify_pkcs7_signature(&ptr, &ptr, trusted_keyring);
82
83 bpf_key_put(trusted_keyring);
84
85 return 0;
86 }
87