/*
  ISC License

  Copyright (c) 2026, Antonio SJ Musumeci <trapexit@spawn.link>

  Permission to use, copy, modify, and/or distribute this software for any
  purpose with or without fee is hereby granted, provided that the above
  copyright notice and this permission notice appear in all copies.

  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "caps.hpp"

#if defined __linux__

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/prctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <grp.h>
#include <linux/capability.h>
#include <linux/securebits.h>


static
int
capset(cap_user_header_t     header_,
       const cap_user_data_t data_)
{
  return ::syscall(SYS_capset,header_,data_);
}

static
int
capget(cap_user_header_t header_,
       cap_user_data_t   data_)
{
  return ::syscall(SYS_capget,header_,data_);
}

static
int
capset(int cap_bit_)
{
  int rv;
  struct __user_cap_header_struct header;
  struct __user_cap_data_struct data[2];

  header.version = _LINUX_CAPABILITY_VERSION_3;
  header.pid = 0;

  rv = capget(&header,data);
  if(rv < 0)
    return rv;

  int word = cap_bit_ / 32;
  int bit  = cap_bit_ % 32;

  data[word].permitted   |= (1 << bit);
  data[word].effective   |= (1 << bit);
  data[word].inheritable |= (1 << bit);

  rv = capset(&header,data);
  if(rv < 0)
    return rv;

  return 0;
}

int
caps::setup()
{
  int rv;

  rv = capset(CAP_DAC_OVERRIDE);
  if(rv < 0)
    return rv;
  rv = capset(CAP_DAC_READ_SEARCH);
  if(rv < 0)
    return rv;
  rv = capset(CAP_FOWNER);
  if(rv < 0)
    return rv;
  rv = capset(CAP_CHOWN);
  if(rv < 0)
    return rv;
  rv = capset(CAP_SETUID);
  if(rv < 0)
    return rv;
  rv = capset(CAP_SETGID);
  if(rv < 0)
    return rv;

  rv = prctl(PR_SET_SECUREBITS,
             SECBIT_KEEP_CAPS | SECBIT_NO_SETUID_FIXUP);
  if(rv < 0)
    return -errno;

  return 0;
}
#else
#include <errno.h>

int
caps::setup()
{
  return -ENOSYS;
}
#endif