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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH
*
* Author: Roberto Sassu <roberto.sassu@huawei.com>
*/
#include "vmlinux.h"
#include <errno.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#define MAX_DATA_SIZE (1024 * 1024)
#define MAX_SIG_SIZE 1024
extern struct bpf_key *bpf_lookup_user_key(__u32 serial, __u64 flags) __ksym;
extern struct bpf_key *bpf_lookup_system_key(__u64 id) __ksym;
extern void bpf_key_put(struct bpf_key *key) __ksym;
extern int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_ptr,
struct bpf_dynptr *sig_ptr,
struct bpf_key *trusted_keyring) __ksym;
__u32 monitored_pid;
__u32 user_keyring_serial;
__u64 system_keyring_id;
struct data {
__u8 data[MAX_DATA_SIZE];
__u32 data_len;
__u8 sig[MAX_SIG_SIZE];
__u32 sig_len;
};
struct {
__uint(type, BPF_MAP_TYPE_ARRAY);
__uint(max_entries, 1);
__type(key, __u32);
__type(value, struct data);
} data_input SEC(".maps");
char _license[] SEC("license") = "GPL";
SEC("lsm.s/bpf")
int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size)
{
struct bpf_dynptr data_ptr, sig_ptr;
struct data *data_val;
struct bpf_key *trusted_keyring;
__u32 pid;
__u64 value;
int ret, zero = 0;
pid = bpf_get_current_pid_tgid() >> 32;
if (pid != monitored_pid)
return 0;
data_val = bpf_map_lookup_elem(&data_input, &zero);
if (!data_val)
return 0;
ret = bpf_probe_read_kernel(&value, sizeof(value), &attr->value);
if (ret)
return ret;
ret = bpf_copy_from_user(data_val, sizeof(struct data),
(void *)(unsigned long)value);
if (ret)
return ret;
if (data_val->data_len > sizeof(data_val->data))
return -EINVAL;
bpf_dynptr_from_mem(data_val->data, data_val->data_len, 0, &data_ptr);
if (data_val->sig_len > sizeof(data_val->sig))
return -EINVAL;
bpf_dynptr_from_mem(data_val->sig, data_val->sig_len, 0, &sig_ptr);
if (user_keyring_serial)
trusted_keyring = bpf_lookup_user_key(user_keyring_serial, 0);
else
trusted_keyring = bpf_lookup_system_key(system_keyring_id);
if (!trusted_keyring)
return -ENOENT;
ret = bpf_verify_pkcs7_signature(&data_ptr, &sig_ptr, trusted_keyring);
bpf_key_put(trusted_keyring);
return ret;
}
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