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_kfuncs.h" |
14 | |
15 | #define MAX_DATA_SIZE (1024 * 1024) |
16 | #define MAX_SIG_SIZE 1024 |
17 | |
18 | __u32 monitored_pid; |
19 | __u32 user_keyring_serial; |
20 | __u64 system_keyring_id; |
21 | |
22 | struct data { |
23 | __u8 data[MAX_DATA_SIZE]; |
24 | __u32 data_len; |
25 | __u8 sig[MAX_SIG_SIZE]; |
26 | __u32 sig_len; |
27 | }; |
28 | |
29 | struct { |
30 | __uint(type, BPF_MAP_TYPE_ARRAY); |
31 | __uint(max_entries, 1); |
32 | __type(key, __u32); |
33 | __type(value, struct data); |
34 | } data_input SEC(".maps" ); |
35 | |
36 | char _license[] SEC("license" ) = "GPL" ; |
37 | |
38 | SEC("lsm.s/bpf" ) |
39 | int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size) |
40 | { |
41 | struct bpf_dynptr data_ptr, sig_ptr; |
42 | struct data *data_val; |
43 | struct bpf_key *trusted_keyring; |
44 | __u32 pid; |
45 | __u64 value; |
46 | int ret, zero = 0; |
47 | |
48 | pid = bpf_get_current_pid_tgid() >> 32; |
49 | if (pid != monitored_pid) |
50 | return 0; |
51 | |
52 | data_val = bpf_map_lookup_elem(&data_input, &zero); |
53 | if (!data_val) |
54 | return 0; |
55 | |
56 | ret = bpf_probe_read_kernel(&value, sizeof(value), &attr->value); |
57 | if (ret) |
58 | return ret; |
59 | |
60 | ret = bpf_copy_from_user(data_val, sizeof(struct data), |
61 | (void *)(unsigned long)value); |
62 | if (ret) |
63 | return ret; |
64 | |
65 | if (data_val->data_len > sizeof(data_val->data)) |
66 | return -EINVAL; |
67 | |
68 | bpf_dynptr_from_mem(data_val->data, data_val->data_len, 0, &data_ptr); |
69 | |
70 | if (data_val->sig_len > sizeof(data_val->sig)) |
71 | return -EINVAL; |
72 | |
73 | bpf_dynptr_from_mem(data_val->sig, data_val->sig_len, 0, &sig_ptr); |
74 | |
75 | if (user_keyring_serial) |
76 | trusted_keyring = bpf_lookup_user_key(user_keyring_serial, 0); |
77 | else |
78 | trusted_keyring = bpf_lookup_system_key(system_keyring_id); |
79 | |
80 | if (!trusted_keyring) |
81 | return -ENOENT; |
82 | |
83 | ret = bpf_verify_pkcs7_signature(&data_ptr, &sig_ptr, trusted_keyring); |
84 | |
85 | bpf_key_put(trusted_keyring); |
86 | |
87 | return ret; |
88 | } |
89 | |