utils.h

/* bubblewrap
 * Copyright (C) 2016 Alexander Larsson
 * SPDX-License-Identifier: LGPL-2.0-or-later
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
 *
 */

#pragma once

#include <assert.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>

#ifdef BWRAP_DEBUG
extern bool bwrap_is_debugging;
#define debug(...) bwrap_log (LOG_DEBUG, __VA_ARGS__)
#else
#define debug(...)
#endif

#define UNUSED __attribute__((__unused__))

#define BWRAP_KERNEL_VERSION(a, b, c) (((a) << 16) + ((b) << 8) + (c))
#ifdef HAVE_ASSUMED_KERNEL
#  define ASSUMED_KERNEL \
     BWRAP_KERNEL_VERSION (ASSUMED_KERNEL_MAJOR, ASSUMED_KERNEL_MINOR, ASSUMED_KERNEL_PATCH)
#else
#  define ASSUMED_KERNEL 0
#endif

#define N_ELEMENTS(arr) (sizeof (arr) / sizeof ((arr)[0]))

#ifndef TEMP_FAILURE_RETRY
#define TEMP_FAILURE_RETRY(expression) \
  (__extension__                                                              \
    ({ long int __result;                                                     \
       do __result = (long int) (expression);                                 \
       while (__result == -1L && errno == EINTR);                             \
       __result; }))
#endif

#define PIPE_READ_END 0
#define PIPE_WRITE_END 1

#ifndef PR_SET_CHILD_SUBREAPER
#define PR_SET_CHILD_SUBREAPER 36
#endif

extern bool bwrap_level_prefix;
extern int proc_fd;

void  bwrap_log (int severity,
                 const char *format,
                 ...) __attribute__((format (printf, 2, 3)));
#define warn(...) bwrap_log (LOG_WARNING, __VA_ARGS__)

void  die_with_error (const char *format,
                      ...) __attribute__((__noreturn__)) __attribute__((format (printf, 1, 2)));
void  die_with_mount_error (const char *format,
                            ...) __attribute__((__noreturn__)) __attribute__((format (printf, 1, 2)));
void  die (const char *format,
           ...) __attribute__((__noreturn__)) __attribute__((format (printf, 1, 2)));
void  die_oom (void) __attribute__((__noreturn__));
void  die_unless_label_valid (const char *label);

void  fork_intermediate_child (void);

void *xmalloc (size_t size);
void *xcalloc (size_t nmemb, size_t size);
void *xrealloc (void  *ptr,
                size_t size);
char *xstrdup (const char *str);
char *xstrndup(const char *str, size_t n);
void  strfreev (char **str_array);
void  xclearenv (void);
void  xsetenv (const char *name,
               const char *value,
               int         overwrite);
void  xunsetenv (const char *name);
char *strconcat (const char *s1,
                 const char *s2);
char *strconcat3 (const char *s1,
                  const char *s2,
                  const char *s3);
char * xasprintf (const char *format,
                  ...) __attribute__((format (printf, 1, 2)));
bool  has_prefix (const char *str,
                  const char *prefix);
bool  has_path_prefix (const char *str,
                       const char *prefix);
bool  path_equal (const char *path1,
                  const char *path2);
int   fdwalk (int (*cb)(void *data,
                        int fd),
              void *data);
char *load_file_data (int     fd,
                      size_t *size);
char *load_file_at (int         dirfd,
                    const char *path);
int   write_file_at (int         dirfd,
                     const char *path,
                     const char *content);
int   write_to_fd (int         fd,
                   const char *content,
                   ssize_t     len);
int   copy_file_data (int sfd,
                      int dfd);
int   copy_file (const char *src_path,
                 const char *dst_path,
                 mode_t      mode);
int   create_file (const char *path,
                   mode_t      mode,
                   const char *content);
int   ensure_file (const char *path,
                   mode_t      mode);
int   ensure_dir (const char *path,
                  mode_t      mode);
int   get_file_mode (int fd);
int   mkdir_with_parents (const char *pathname,
                          mode_t      mode,
                          bool        create_last);
void create_pid_socketpair (int sockets[2]);
void send_pid_on_socket (int socket);
int  read_pid_from_socket (int socket);
char *get_oldroot_path (const char *path);
char *readlink_malloc (const char *pathname);
char *fd_to_proc_path (int fd);

/* syscall wrappers */
int   raw_clone (unsigned long flags,
                 void         *child_stack);
int   pivot_root (const char *new_root,
                  const char *put_old);
char *label_mount (const char *opt,
                   const char *mount_label);
int   label_exec (const char *exec_label);
int   label_create_file (const char *file_label);

extern bool opt_force_openat_fallback;
extern bool opt_force_mount_setattr_fallback;

int safe_openat (int dirfd,
                 const char *rootfs,
                 const char *path,
                 int flags,
                 int mode);
char *chroot_realpath (const char *chroot,
                       const char *path,
                       char resolved_path[]);

static inline bool
is_empty_string (const char *s)
{
  return s == NULL || s[0] == '\0';
}

const char *mount_strerror (int errsv);

static inline void
cleanup_freep (void *p)
{
  void **pp = (void **) p;

  if (*pp)
    free (*pp);
}

static inline void
cleanup_strvp (void *p)
{
  void **pp = (void **) p;

  strfreev (*pp);
}

static inline void
cleanup_fdp (int *fdp)
{
  int fd;

  assert (fdp);

  fd = *fdp;
  if (fd != -1)
    (void) close (fd);
}

#define cleanup_free __attribute__((cleanup (cleanup_freep)))
#define cleanup_fd __attribute__((cleanup (cleanup_fdp)))
#define cleanup_strv __attribute__((cleanup (cleanup_strvp)))

static inline int
steal_fd (int *fdp)
{
  int fd = *fdp;
  *fdp = -1;
  return fd;
}

static inline void *
steal_pointer (void *pp)
{
  void **ptr = (void **) pp;
  void *ref;

  ref = *ptr;
  *ptr = NULL;

  return ref;
}

/* type safety */
#define steal_pointer(pp) \
  (0 ? (*(pp)) : (steal_pointer) (pp))

typedef struct {
  int    *fds;
  size_t  len;
  size_t  alloc;
} FdSet;

static inline int
fdset_add (FdSet *set, int fd)
{
  if (set->len == set->alloc)
    {
      set->alloc = set->alloc ? set->alloc * 2 : 4;
      set->fds = xrealloc (set->fds, set->alloc * sizeof (int));
    }
  set->fds[set->len++] = fd;
  return fd;
}

static inline void
cleanup_fdsetp (FdSet *set)
{
  size_t i;

  for (i = 0; i < set->len; i++)
    if (set->fds[i] >= 0)
      close (set->fds[i]);
  free (set->fds);
}

#define cleanup_fdset __attribute__((cleanup (cleanup_fdsetp)))

static inline char *
fdset_add_to_proc_path (FdSet *set, int fd)
{
  return fd_to_proc_path (fdset_add (set, fd));
}

typedef struct _StringBuilder StringBuilder;

struct _StringBuilder
{
  char * str;
  size_t size;
  size_t offset;
};

void strappend (StringBuilder *dest,
                const char    *src);
void strappendf (StringBuilder *dest,
                 const char    *fmt,
                 ...);
void strappend_escape_for_mount_options (StringBuilder *dest,
                                         const char    *src);

#ifndef MOUNT_ATTR_RDONLY

#include <linux/types.h>

struct mount_attr
{
  __u64 attr_set;
  __u64 attr_clr;
  __u64 propagation;
  __u64 userns_fd;
};

#define MOUNT_ATTR_RDONLY       0x00000001
#define MOUNT_ATTR_NOSUID       0x00000002
#define MOUNT_ATTR_NODEV        0x00000004
#define MOUNT_ATTR_NOEXEC       0x00000008
#define MOUNT_ATTR__ATIME       0x00000070
#define MOUNT_ATTR_RELATIME     0x00000000
#define MOUNT_ATTR_NOATIME      0x00000010
#define MOUNT_ATTR_STRICTATIME  0x00000020
#define MOUNT_ATTR_NODIRATIME   0x00000080
#define MOUNT_ATTR_IDMAP        0x00100000
#define MOUNT_ATTR_NOSYMFOLLOW  0x00200000
#endif

#ifndef AT_RECURSIVE
#define AT_RECURSIVE  0x8000
#endif

int mount_setattr_wrapper (int dirfd, const char *path, unsigned int flags,
                           struct mount_attr *attr, size_t size);