93 lines · c
1// SPDX-License-Identifier: GPL-2.02 3/*4 * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH5 *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#include "err.h"15 16#define MAX_DATA_SIZE (1024 * 1024)17#define MAX_SIG_SIZE 102418 19__u32 monitored_pid;20__u32 user_keyring_serial;21__u64 system_keyring_id;22 23struct data {24 __u8 data[MAX_DATA_SIZE];25 __u32 data_len;26 __u8 sig[MAX_SIG_SIZE];27 __u32 sig_len;28};29 30struct {31 __uint(type, BPF_MAP_TYPE_ARRAY);32 __uint(max_entries, 1);33 __type(key, __u32);34 __type(value, struct data);35} data_input SEC(".maps");36 37char _license[] SEC("license") = "GPL";38 39SEC("lsm.s/bpf")40int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size)41{42 struct bpf_dynptr data_ptr, sig_ptr;43 struct data *data_val;44 struct bpf_key *trusted_keyring;45 __u32 pid;46 __u64 value;47 int ret, zero = 0;48 49 pid = bpf_get_current_pid_tgid() >> 32;50 if (pid != monitored_pid)51 return 0;52 53 data_val = bpf_map_lookup_elem(&data_input, &zero);54 if (!data_val)55 return 0;56 57 ret = bpf_probe_read_kernel(&value, sizeof(value), &attr->value);58 if (ret)59 goto out;60 61 ret = bpf_copy_from_user(data_val, sizeof(struct data),62 (void *)(unsigned long)value);63 if (ret)64 goto out;65 66 if (data_val->data_len > sizeof(data_val->data))67 return -EINVAL;68 69 bpf_dynptr_from_mem(data_val->data, data_val->data_len, 0, &data_ptr);70 71 if (data_val->sig_len > sizeof(data_val->sig))72 return -EINVAL;73 74 bpf_dynptr_from_mem(data_val->sig, data_val->sig_len, 0, &sig_ptr);75 76 if (user_keyring_serial)77 trusted_keyring = bpf_lookup_user_key(user_keyring_serial, 0);78 else79 trusted_keyring = bpf_lookup_system_key(system_keyring_id);80 81 if (!trusted_keyring)82 return -ENOENT;83 84 ret = bpf_verify_pkcs7_signature(&data_ptr, &sig_ptr, trusted_keyring);85 86 bpf_key_put(trusted_keyring);87 88out:89 set_if_not_errno_or_zero(ret, -EFAULT);90 91 return ret;92}93