libguestfs/daemon/file.c

/* libguestfs - the guestfsd daemon
 * Copyright (C) 2009-2012 Red Hat Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include <config.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>

#include "guestfs_protocol.h"
#include "daemon.h"
#include "actions.h"

int
do_touch (const char *path)
{
  int fd;
  int r;
  struct stat buf;

  /* RHBZ#582484: Restrict touch to regular files.  It's also OK
   * here if the file does not exist, since we will create it.
   *
   * XXX Coverity flags this as a time-of-check to time-of-use race
   * condition, particularly in the libguestfs live case.  Not clear
   * how to fix this yet, since unconditionally opening the file can
   * cause a hang, so you have to somehow check it first before you
   * open it.
   */
  CHROOT_IN;
  r = lstat (path, &buf);
  CHROOT_OUT;

  if (r == -1) {
    if (errno != ENOENT) {
      reply_with_perror ("lstat: %s", path);
      return -1;
    }
  } else {
    if (! S_ISREG (buf.st_mode)) {
      reply_with_error ("%s: touch can only be used on a regular files", path);
      return -1;
    }
  }

  CHROOT_IN;
  fd = open (path, O_WRONLY|O_CREAT|O_NOCTTY|O_CLOEXEC, 0666);
  CHROOT_OUT;

  if (fd == -1) {
    reply_with_perror ("open: %s", path);
    return -1;
  }

  r = futimens (fd, NULL);
  if (r == -1) {
    reply_with_perror ("futimens: %s", path);
    close (fd);
    return -1;
  }

  if (close (fd) == -1) {
    reply_with_perror ("close: %s", path);
    return -1;
  }

  return 0;
}

char *
do_cat (const char *path)
{
  int fd;
  size_t alloc, size, max;
  ssize_t r;
  char *buf, *buf2;

  CHROOT_IN;
  fd = open (path, O_RDONLY|O_CLOEXEC);
  CHROOT_OUT;

  if (fd == -1) {
    reply_with_perror ("open: %s", path);
    return NULL;
  }

  /* Read up to GUESTFS_MESSAGE_MAX - <overhead> bytes.  If it's
   * larger than that, we need to return an error instead (for
   * correctness).
   */
  max = GUESTFS_MESSAGE_MAX - 1000;
  buf = NULL;
  size = alloc = 0;

  for (;;) {
    if (size >= alloc) {
      alloc += 8192;
      if (alloc > max) {
        reply_with_error ("%s: file is too large for message buffer",
                          path);
        free (buf);
        close (fd);
        return NULL;
      }
      buf2 = realloc (buf, alloc);
      if (buf2 == NULL) {
        reply_with_perror ("realloc");
        free (buf);
        close (fd);
        return NULL;
      }
      buf = buf2;
    }

    r = read (fd, buf + size, alloc - size);
    if (r == -1) {
      reply_with_perror ("read: %s", path);
      free (buf);
      close (fd);
      return NULL;
    }
    if (r == 0) {
      buf[size] = '\0';
      break;
    }
    if (r > 0)
      size += r;
  }

  if (close (fd) == -1) {
    reply_with_perror ("close: %s", path);
    free (buf);
    return NULL;
  }

  return buf;			/* caller will free */
}

char **
do_read_lines (const char *path)
{
  DECLARE_STRINGSBUF (r);
  FILE *fp;
  char *line = NULL;
  size_t len = 0;
  ssize_t n;

  CHROOT_IN;
  fp = fopen (path, "r");
  CHROOT_OUT;

  if (!fp) {
    reply_with_perror ("fopen: %s", path);
    return NULL;
  }

  while ((n = getline (&line, &len, fp)) != -1) {
    /* Remove either LF or CRLF. */
    if (n >= 2 && line[n-2] == '\r' && line[n-1] == '\n')
      line[n-2] = '\0';
    else if (n >= 1 && line[n-1] == '\n')
      line[n-1] = '\0';

    if (add_string (&r, line) == -1) {
      free (line);
      fclose (fp);
      return NULL;
    }
  }

  free (line);

  if (end_stringsbuf (&r) == -1) {
    fclose (fp);
    return NULL;
  }

  if (fclose (fp) == EOF) {
    reply_with_perror ("fclose: %s", path);
    free_stringslen (r.argv, r.size);
    return NULL;
  }

  return r.argv;
}

int
do_rm (const char *path)
{
  int r;

  CHROOT_IN;
  r = unlink (path);
  CHROOT_OUT;

  if (r == -1) {
    reply_with_perror ("%s", path);
    return -1;
  }

  return 0;
}

int
do_chmod (int mode, const char *path)
{
  int r;

  if (mode < 0) {
    reply_with_error ("%s: mode is negative", path);
    return -1;
  }

  CHROOT_IN;
  r = chmod (path, mode);
  CHROOT_OUT;

  if (r == -1) {
    reply_with_perror ("%s: 0%o", path, mode);
    return -1;
  }

  return 0;
}

int
do_chown (int owner, int group, const char *path)
{
  int r;

  CHROOT_IN;
  r = chown (path, owner, group);
  CHROOT_OUT;

  if (r == -1) {
    reply_with_perror ("%s: %d.%d", path, owner, group);
    return -1;
  }

  return 0;
}

int
do_lchown (int owner, int group, const char *path)
{
  int r;

  CHROOT_IN;
  r = lchown (path, owner, group);
  CHROOT_OUT;

  if (r == -1) {
    reply_with_perror ("%s: %d.%d", path, owner, group);
    return -1;
  }

  return 0;
}

int
do_write_file (const char *path, const char *content, int size)
{
  int fd;

  /* This call is deprecated, and it has a broken interface.  New code
   * should use the 'guestfs_write' call instead.  Because we used an
   * XDR string type, 'content' cannot contain ASCII NUL and 'size'
   * must never be longer than the string.  We must check this to
   * ensure random stuff from XDR or daemon memory isn't written to
   * the file (RHBZ#597135).
   */
  if (size < 0) {
    reply_with_error ("size cannot be negative");
    return -1;
  }

  /* Note content_len must be small because of the limits on protocol
   * message size.
   */
  int content_len = (int) strlen (content);

  if (size == 0)
    size = content_len;
  else if (size > content_len) {
    reply_with_error ("size parameter is larger than string content");
    return -1;
  }

  CHROOT_IN;
  fd = open (path, O_WRONLY|O_TRUNC|O_CREAT|O_NOCTTY|O_CLOEXEC, 0666);
  CHROOT_OUT;

  if (fd == -1) {
    reply_with_perror ("open: %s", path);
    return -1;
  }

  if (xwrite (fd, content, size) == -1) {
    reply_with_perror ("write");
    close (fd);
    return -1;
  }

  if (close (fd) == -1) {
    reply_with_perror ("close: %s", path);
    return -1;
  }

  return 0;
}

int
do_write (const char *path, const char *content, size_t size)
{
  int fd;

  CHROOT_IN;
  fd = open (path, O_WRONLY|O_TRUNC|O_CREAT|O_NOCTTY|O_CLOEXEC, 0666);
  CHROOT_OUT;

  if (fd == -1) {
    reply_with_perror ("open: %s", path);
    return -1;
  }

  if (xwrite (fd, content, size) == -1) {
    reply_with_perror ("write");
    close (fd);
    return -1;
  }

  if (close (fd) == -1) {
    reply_with_perror ("close: %s", path);
    return -1;
  }

  return 0;
}

int
do_write_append (const char *path, const char *content, size_t size)
{
  int fd;

  CHROOT_IN;
  fd = open (path, O_WRONLY|O_APPEND|O_CREAT|O_NOCTTY|O_CLOEXEC, 0666);
  CHROOT_OUT;

  if (fd == -1) {
    reply_with_perror ("open: %s", path);
    return -1;
  }

  if (xwrite (fd, content, size) == -1) {
    reply_with_perror ("write");
    close (fd);
    return -1;
  }

  if (close (fd) == -1) {
    reply_with_perror ("close: %s", path);
    return -1;
  }

  return 0;
}

char *
do_read_file (const char *path, size_t *size_r)
{
  int fd;
  struct stat statbuf;
  char *r;

  CHROOT_IN;
  fd = open (path, O_RDONLY|O_CLOEXEC);
  CHROOT_OUT;

  if (fd == -1) {
    reply_with_perror ("open: %s", path);
    return NULL;
  }

  if (fstat (fd, &statbuf) == -1) {
    reply_with_perror ("fstat: %s", path);
    close (fd);
    return NULL;
  }

  /* The actual limit on messages is smaller than this.  This
   * check just limits the amount of memory we'll try and allocate
   * here.  If the message is larger than the real limit, that will
   * be caught later when we try to serialize the message.
   */
  if (statbuf.st_size >= GUESTFS_MESSAGE_MAX) {
    reply_with_error ("%s: file is too large for the protocol, use guestfs_download instead", path);
    close (fd);
    return NULL;
  }
  r = malloc (statbuf.st_size);
  if (r == NULL) {
    reply_with_perror ("malloc");
    close (fd);
    return NULL;
  }

  if (xread (fd, r, statbuf.st_size) == -1) {
    reply_with_perror ("read: %s", path);
    close (fd);
    free (r);
    return NULL;
  }

  if (close (fd) == -1) {
    reply_with_perror ("close: %s", path);
    free (r);
    return NULL;
  }

  /* Mustn't touch *size_r until we are sure that we won't return any
   * error (RHBZ#589039).
   */
  *size_r = statbuf.st_size;
  return r;
}

static char *
pread_fd (int fd, int count, int64_t offset, size_t *size_r,
          const char *display_path)
{
  ssize_t r;
  char *buf;

  if (count < 0) {
    reply_with_error ("count is negative");
    close (fd);
    return NULL;
  }

  if (offset < 0) {
    reply_with_error ("offset is negative");
    close (fd);
    return NULL;
  }

  /* The actual limit on messages is smaller than this.  This check
   * just limits the amount of memory we'll try and allocate in the
   * function.  If the message is larger than the real limit, that
   * will be caught later when we try to serialize the message.
   */
  if (count >= GUESTFS_MESSAGE_MAX) {
    reply_with_error ("%s: count is too large for the protocol, use smaller reads", display_path);
    close (fd);
    return NULL;
  }

  buf = malloc (count);
  if (buf == NULL) {
    reply_with_perror ("malloc");
    close (fd);
    return NULL;
  }

  r = pread (fd, buf, count, offset);
  if (r == -1) {
    reply_with_perror ("pread: %s", display_path);
    close (fd);
    free (buf);
    return NULL;
  }

  if (close (fd) == -1) {
    reply_with_perror ("close: %s", display_path);
    free (buf);
    return NULL;
  }

  /* Mustn't touch *size_r until we are sure that we won't return any
   * error (RHBZ#589039).
   */
  *size_r = r;
  return buf;
}

char *
do_pread (const char *path, int count, int64_t offset, size_t *size_r)
{
  int fd;

  CHROOT_IN;
  fd = open (path, O_RDONLY|O_CLOEXEC);
  CHROOT_OUT;

  if (fd == -1) {
    reply_with_perror ("open: %s", path);
    return NULL;
  }

  return pread_fd (fd, count, offset, size_r, path);
}

char *
do_pread_device (const char *device, int count, int64_t offset, size_t *size_r)
{
  int fd = open (device, O_RDONLY|O_CLOEXEC);
  if (fd == -1) {
    reply_with_perror ("open: %s", device);
    return NULL;
  }

  return pread_fd (fd, count, offset, size_r, device);
}

static int
pwrite_fd (int fd, const char *content, size_t size, int64_t offset,
           const char *display_path)
{
  ssize_t r;

  r = pwrite (fd, content, size, offset);
  if (r == -1) {
    reply_with_perror ("pwrite: %s", display_path);
    close (fd);
    return -1;
  }

  if (close (fd) == -1) {
    reply_with_perror ("close: %s", display_path);
    return -1;
  }

  return r;
}

int
do_pwrite (const char *path, const char *content, size_t size, int64_t offset)
{
  int fd;

  if (offset < 0) {
    reply_with_error ("offset is negative");
    return -1;
  }

  CHROOT_IN;
  fd = open (path, O_WRONLY|O_CLOEXEC);
  CHROOT_OUT;

  if (fd == -1) {
    reply_with_perror ("open: %s", path);
    return -1;
  }

  return pwrite_fd (fd, content, size, offset, path);
}

int
do_pwrite_device (const char *device, const char *content, size_t size,
                  int64_t offset)
{
  if (offset < 0) {
    reply_with_error ("offset is negative");
    return -1;
  }

  int fd = open (device, O_WRONLY|O_CLOEXEC);
  if (fd == -1) {
    reply_with_perror ("open: %s", device);
    return -1;
  }

  return pwrite_fd (fd, content, size, offset, device);
}

/* This runs the 'file' command. */
char *
do_file (const char *path)
{
  char *buf = NULL;
  const char *display_path = path;

  int is_dev = STRPREFIX (path, "/dev/");

  if (!is_dev) {
    buf = sysroot_path (path);
    if (!buf) {
      reply_with_perror ("malloc");
      return NULL;
    }
    path = buf;

    /* For non-dev, check this is a regular file, else just return the
     * file type as a string (RHBZ#582484).
     */
    struct stat statbuf;
    if (lstat (path, &statbuf) == -1) {
      reply_with_perror ("lstat: %s", display_path);
      free (buf);
      return NULL;
    }

    if (! S_ISREG (statbuf.st_mode)) {
      char *ret;

      free (buf);

      if (S_ISDIR (statbuf.st_mode))
        ret = strdup ("directory");
      else if (S_ISCHR (statbuf.st_mode))
        ret = strdup ("character device");
      else if (S_ISBLK (statbuf.st_mode))
        ret = strdup ("block device");
      else if (S_ISFIFO (statbuf.st_mode))
        ret = strdup ("FIFO");
      else if (S_ISLNK (statbuf.st_mode))
        ret = strdup ("symbolic link");
      else if (S_ISSOCK (statbuf.st_mode))
        ret = strdup ("socket");
      else
        ret = strdup ("unknown, not regular file");

      if (ret == NULL)
        reply_with_perror ("strdup");
      return ret;
    }
  }

  /* Which flags to use?  For /dev paths, follow links because
   * /dev/VG/LV is a symbolic link.
   */
  const char *flags = is_dev ? "-zbsL" : "-zb";

  char *out, *err;
  int r = command (&out, &err, "file", flags, path, NULL);
  free (buf);

  if (r == -1) {
    free (out);
    reply_with_error ("%s: %s", display_path, err);
    free (err);
    return NULL;
  }
  free (err);

  /* We need to remove the trailing \n from output of file(1). */
  size_t len = strlen (out);
  if (len > 0 && out[len-1] == '\n')
    out[len-1] = '\0';

  return out;			/* caller frees */
}

/* zcat | file */
char *
do_zfile (const char *method, const char *path)
{
  size_t len;
  const char *zcat;
  char *cmd;
  FILE *fp;
  char line[256];

  if (STREQ (method, "gzip") || STREQ (method, "compress"))
    zcat = "zcat";
  else if (STREQ (method, "bzip2"))
    zcat = "bzcat";
  else {
    reply_with_error ("unknown method");
    return NULL;
  }

  if (asprintf_nowarn (&cmd, "%s %R | file -bsL -", zcat, path) == -1) {
    reply_with_perror ("asprintf");
    return NULL;
  }

  if (verbose)
    fprintf (stderr, "%s\n", cmd);

  fp = popen (cmd, "r");
  if (fp == NULL) {
    reply_with_perror ("%s", cmd);
    free (cmd);
    return NULL;
  }

  free (cmd);

  if (fgets (line, sizeof line, fp) == NULL) {
    reply_with_perror ("fgets");
    fclose (fp);
    return NULL;
  }

  if (fclose (fp) == -1) {
    reply_with_perror ("fclose");
    return NULL;
  }

  len = strlen (line);
  if (len > 0 && line[len-1] == '\n')
    line[len-1] = '\0';

  return strdup (line);
}

int64_t
do_filesize (const char *path)
{
  int r;
  struct stat buf;

  CHROOT_IN;
  r = stat (path, &buf);        /* follow symlinks */
  CHROOT_OUT;

  if (r == -1) {
    reply_with_perror ("%s", path);
    return -1;
  }

  return buf.st_size;
}