// SPDX-License-Identifier: GPL-2.0

/*
 * Copyright 2020 Google LLC.
 */

#include "vmlinux.h"
#include <errno.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>

u32 monitored_pid = 0;

struct {
        __uint(type, BPF_MAP_TYPE_RINGBUF);
        __uint(max_entries, 1 << 12);
} ringbuf SEC(".maps");

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

bool use_ima_file_hash;
bool enable_bprm_creds_for_exec;
bool enable_kernel_read_file;
bool test_deny;

static void ima_test_common(struct file *file)
{
        u64 ima_hash = 0;
        u64 *sample;
        int ret;
        u32 pid;

        pid = bpf_get_current_pid_tgid() >> 32;
        if (pid == monitored_pid) {
                if (!use_ima_file_hash)
                        ret = bpf_ima_inode_hash(file->f_inode, &ima_hash,
                                                 sizeof(ima_hash));
                else
                        ret = bpf_ima_file_hash(file, &ima_hash,
                                                sizeof(ima_hash));
                if (ret < 0 || ima_hash == 0)
                        return;

                sample = bpf_ringbuf_reserve(&ringbuf, sizeof(u64), 0);
                if (!sample)
                        return;

                *sample = ima_hash;
                bpf_ringbuf_submit(sample, 0);
        }

        return;
}

static int ima_test_deny(void)
{
        u32 pid;

        pid = bpf_get_current_pid_tgid() >> 32;
        if (pid == monitored_pid && test_deny)
                return -EPERM;

        return 0;
}

SEC("lsm.s/bprm_committed_creds")
void BPF_PROG(bprm_committed_creds, struct linux_binprm *bprm)
{
        ima_test_common(bprm->file);
}

SEC("lsm.s/bprm_creds_for_exec")
int BPF_PROG(bprm_creds_for_exec, struct linux_binprm *bprm)
{
        if (!enable_bprm_creds_for_exec)
                return 0;

        ima_test_common(bprm->file);
        return 0;
}

SEC("lsm.s/kernel_read_file")
int BPF_PROG(kernel_read_file, struct file *file, enum kernel_read_file_id id,
             bool contents)
{
        int ret;

        if (!enable_kernel_read_file)
                return 0;

        if (!contents)
                return 0;

        if (id != READING_POLICY)
                return 0;

        ret = ima_test_deny();
        if (ret < 0)
                return ret;

        ima_test_common(file);
        return 0;
}