// 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>
#include "bpf_misc.h"

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;

struct {
        __uint(type, BPF_MAP_TYPE_RINGBUF);
        __uint(max_entries, 4096);
} ringbuf SEC(".maps");

struct {
        __uint(type, BPF_MAP_TYPE_ARRAY);
        __uint(max_entries, 1);
        __type(key, __u32);
        __type(value, __u32);
} array_map SEC(".maps");

int err, pid;

char _license[] SEC("license") = "GPL";

SEC("?lsm.s/bpf")
__failure __msg("cannot pass in dynptr at an offset=-8")
int BPF_PROG(not_valid_dynptr, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
{
        unsigned long val;

        return bpf_verify_pkcs7_signature((struct bpf_dynptr *)&val,
                                          (struct bpf_dynptr *)&val, NULL);
}

SEC("?lsm.s/bpf")
__failure __msg("arg#0 expected pointer to stack or const struct bpf_dynptr")
int BPF_PROG(not_ptr_to_stack, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
{
        static struct bpf_dynptr val;

        return bpf_verify_pkcs7_signature(&val, &val, NULL);
}

SEC("lsm.s/bpf")
int BPF_PROG(dynptr_data_null, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
{
        struct bpf_key *trusted_keyring;
        struct bpf_dynptr ptr;
        __u32 *value;
        int ret, zero = 0;

        if (bpf_get_current_pid_tgid() >> 32 != pid)
                return 0;

        value = bpf_map_lookup_elem(&array_map, &zero);
        if (!value)
                return 0;

        /* Pass invalid flags. */
        ret = bpf_dynptr_from_mem(value, sizeof(*value), ((__u64)~0ULL), &ptr);
        if (ret != -EINVAL)
                return 0;

        trusted_keyring = bpf_lookup_system_key(0);
        if (!trusted_keyring)
                return 0;

        err = bpf_verify_pkcs7_signature(&ptr, &ptr, trusted_keyring);

        bpf_key_put(trusted_keyring);

        return 0;
}