155714Skris// SPDX-License-Identifier: GPL-2.0
255714Skris
355714Skris/*
455714Skris * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH
555714Skris *
655714Skris * Author: Roberto Sassu <roberto.sassu@huawei.com>
755714Skris */
855714Skris
955714Skris#include "vmlinux.h"
1055714Skris#include <errno.h>
1155714Skris#include <bpf/bpf_helpers.h>
1255714Skris#include <bpf/bpf_tracing.h>
1355714Skris#include "bpf_kfuncs.h"
1455714Skris
1555714Skris#define MAX_DATA_SIZE (1024 * 1024)
1655714Skris#define MAX_SIG_SIZE 1024
1755714Skris
1855714Skris__u32 monitored_pid;
1955714Skris__u32 user_keyring_serial;
2055714Skris__u64 system_keyring_id;
2155714Skris
2255714Skrisstruct data {
2355714Skris	__u8 data[MAX_DATA_SIZE];
2455714Skris	__u32 data_len;
2555714Skris	__u8 sig[MAX_SIG_SIZE];
2655714Skris	__u32 sig_len;
2755714Skris};
2855714Skris
2955714Skrisstruct {
3055714Skris	__uint(type, BPF_MAP_TYPE_ARRAY);
3155714Skris	__uint(max_entries, 1);
3255714Skris	__type(key, __u32);
3355714Skris	__type(value, struct data);
3455714Skris} data_input SEC(".maps");
3555714Skris
3655714Skrischar _license[] SEC("license") = "GPL";
3755714Skris
3855714SkrisSEC("lsm.s/bpf")
3955714Skrisint BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size)
4055714Skris{
4155714Skris	struct bpf_dynptr data_ptr, sig_ptr;
4255714Skris	struct data *data_val;
4355714Skris	struct bpf_key *trusted_keyring;
4455714Skris	__u32 pid;
4555714Skris	__u64 value;
4655714Skris	int ret, zero = 0;
4755714Skris
4855714Skris	pid = bpf_get_current_pid_tgid() >> 32;
4955714Skris	if (pid != monitored_pid)
5055714Skris		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