path: root/compress.c

/* Copyright (C) 1997 Alain Penders <Alain@Finale-Dev.com>
 * Copyright (C) 2016 Richard Russon <rich@flatcap.org>
 *
 *     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.
 */

#if HAVE_CONFIG_H
#include "config.h"
#endif

#include <errno.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>

#include "mutt.h"
#include "mailbox.h"
#include "mutt_curses.h"
#include "mx.h"
#include "compress.h"

/* Notes:
 * Any references to compressed files also apply to encrypted files.
 * ctx->path     == plaintext file
 * ctx->realpath == compressed file
 */

/**
 * struct COMPRESS_INFO - Private data for compress
 *
 * This object gets attached to the mailbox's CONTEXT.
 */
typedef struct
{
  const char *append;             /* append-hook command */
  const char *close;              /* close-hook  command */
  const char *open;               /* open-hook   command */
  off_t size;                     /* size of the compressed file */
  struct mx_ops *child_ops;       /* callbacks of de-compressed file */
  int locked;                     /* if realpath is locked */
  FILE *lockfp;                   /* fp used for locking */
} COMPRESS_INFO;


/**
 * lock_realpath - Try to lock the ctx->realpath
 * @ctx:  Mailbox to lock
 * @excl: Lock exclusively?
 *
 * Try to (exclusively) lock the mailbox.  If we succeed, then we mark the
 * mailbox as locked.  If we fail, but we didn't want exclusive rights, then
 * the mailbox will be marked readonly.
 *
 * Returns:
 *      1: Success (locked or readonly)
 *      0: Error (can't lock the file)
 */
static int
lock_realpath (CONTEXT *ctx, int excl)
{
  if (!ctx)
    return 0;

  COMPRESS_INFO *ci = ctx->compress_info;
  if (!ci)
    return 0;

  if (ci->locked)
    return 1;

  if (excl)
    ci->lockfp = fopen (ctx->realpath, "a");
  else
    ci->lockfp = fopen (ctx->realpath, "r");
  if (!ci->lockfp)
  {
    mutt_perror (ctx->realpath);
    return 0;
  }

  int r = mx_lock_file (ctx->realpath, fileno (ci->lockfp), excl, 1, 1);

  if (r == 0)
    ci->locked = 1;
  else if (excl == 0)
  {
    safe_fclose (&ci->lockfp);
    ctx->readonly = 1;
    return 1;
  }

  return (r == 0);
}

/**
 * unlock_realpath - Unlock the ctx->realpath
 * @ctx: Mailbox to unlock
 *
 * Unlock a mailbox previously locked by lock_mailbox().
 */
static void
unlock_realpath (CONTEXT *ctx)
{
  if (!ctx)
    return;

  COMPRESS_INFO *ci = ctx->compress_info;
  if (!ci)
    return;

  if (!ci->locked)
    return;

  mx_unlock_file (ctx->realpath, fileno (ci->lockfp), 1);

  ci->locked = 0;
  safe_fclose (&ci->lockfp);
}

/**
 * setup_paths - Set the mailbox paths
 * @ctx: Mailbox to modify
 *
 * Save the compressed filename in ctx->realpath.
 * Create a temporary filename and put its name in ctx->path.
 * The temporary file is created to prevent symlink attacks.
 *
 * Returns:
 *      0: Success
 *      -1: Error
 */
static int
setup_paths (CONTEXT *ctx)
{
  if (!ctx)
    return -1;

  char tmppath[_POSIX_PATH_MAX];
  FILE *tmpfp;

  /* Setup the right paths */
  FREE(&ctx->realpath);
  ctx->realpath = ctx->path;

  /* We will uncompress to /tmp */
  mutt_mktemp (tmppath, sizeof (tmppath));
  ctx->path = safe_strdup (tmppath);

  if ((tmpfp = safe_fopen (ctx->path, "w")) == NULL)
    return -1;

  safe_fclose (&tmpfp);
  return 0;
}

/**
 * get_size - Get the size of a file
 * @path: File to measure
 *
 * Returns:
 *      number: Size in bytes
 *      0:      On error
 */
static int
get_size (const char *path)
{
  if (!path)
    return 0;

  struct stat sb;
  if (stat (path, &sb) != 0)
    return 0;

  return sb.st_size;
}

/**
 * store_size - Save the size of the compressed file
 * @ctx: Mailbox
 *
 * Save the compressed file size in the compress_info struct.
 */
static void
store_size (const CONTEXT *ctx)
{
  if (!ctx)
    return;

  COMPRESS_INFO *ci = ctx->compress_info;
  if (!ci)
    return;

  ci->size = get_size (ctx->realpath);
}

/**
 * find_hook - Find a hook to match a path
 * @type: Type of hook, e.g. MUTT_CLOSEHOOK
 * @path: Filename to test
 *
 * Each hook has a type and a pattern.
 * Find a command that matches the type and path supplied. e.g.
 *
 * User config:
 *      open-hook '\.gz$' "gzip -cd '%f' > '%t'"
 *
 * Call:
 *      find_hook (MUTT_OPENHOOK, "myfile.gz");
 *
 * Returns:
 *      string: Matching hook command
 *      NULL:   No matches
 */
static const char *
find_hook (int