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
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