root/trunk/lib-src/movemail.c

/* movemail foo bar -- move file foo to file bar,
   locking file foo the way /bin/mail respects.
   Copyright (C) 1986, 1992, 1993, 1994, 1996, 1999, 2001, 2002, 2003, 2004,
                 2005, 2006, 2007, 2008  Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs 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 3, or (at your option)
any later version.

GNU Emacs 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 GNU Emacs; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.  */

/* Important notice: defining MAIL_USE_FLOCK or MAIL_USE_LOCKF *will
   cause loss of mail* if you do it on a system that does not normally
   use flock as its way of interlocking access to inbox files.  The
   setting of MAIL_USE_FLOCK and MAIL_USE_LOCKF *must agree* with the
   system's own conventions.  It is not a choice that is up to you.

   So, if your system uses lock files rather than flock, then the only way
   you can get proper operation is to enable movemail to write lockfiles there.
   This means you must either give that directory access modes
   that permit everyone to write lockfiles in it, or you must make movemail
   a setuid or setgid program.  */

/*
 * Modified January, 1986 by Michael R. Gretzinger (Project Athena)
 *
 * Added POP (Post Office Protocol) service.  When compiled -DMAIL_USE_POP
 * movemail will accept input filename arguments of the form
 * "po:username".  This will cause movemail to open a connection to
 * a pop server running on $MAILHOST (environment variable).  Movemail
 * must be setuid to root in order to work with POP.
 *
 * New module: popmail.c
 * Modified routines:
 *      main - added code within #ifdef MAIL_USE_POP; added setuid (getuid ())
 *              after POP code.
 * New routines in movemail.c:
 *      get_errmsg - return pointer to system error message
 *
 * Modified August, 1993 by Jonathan Kamens (OpenVision Technologies)
 *
 * Move all of the POP code into a separate file, "pop.c".
 * Use strerror instead of get_errmsg.
 *
 */

#define NO_SHORTNAMES   /* Tell config not to load remap.h */
#include <config.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <stdio.h>
#include <errno.h>

#include <getopt.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif
#include "syswait.h"
#ifdef MAIL_USE_POP
#include "pop.h"
#endif

#ifdef MSDOS
#undef access
#endif /* MSDOS */

#ifndef DIRECTORY_SEP
#define DIRECTORY_SEP '/'
#endif
#ifndef IS_DIRECTORY_SEP
#define IS_DIRECTORY_SEP(_c_) ((_c_) == DIRECTORY_SEP)
#endif

#ifdef WINDOWSNT
#include "ntlib.h"
#ifndef MEADOW
#undef access
#undef unlink
#endif
#define fork() 0
#define wait(var) (*(var) = 0)
/* Unfortunately, Samba doesn't seem to properly lock Unix files even
   though the locking call succeeds (and indeed blocks local access from
   other NT programs).  If you have direct file access using an NFS
   client or something other than Samba, the locking call might work
   properly - make sure it does before you enable this!

   [18-Feb-97 andrewi] I now believe my comment above to be incorrect,
   since it was based on a misunderstanding of how locking calls are
   implemented and used on Unix.  */
//#define DISABLE_DIRECT_ACCESS

#include <fcntl.h>
#endif /* WINDOWSNT */

#ifndef F_OK
#define F_OK 0
#define X_OK 1
#define W_OK 2
#define R_OK 4
#endif

#if defined (XENIX) || defined (WINDOWSNT)
#include <sys/locking.h>
#endif

#ifdef MAIL_USE_LOCKF
#define MAIL_USE_SYSTEM_LOCK
#endif

#ifdef MAIL_USE_FLOCK
#define MAIL_USE_SYSTEM_LOCK
#endif

#ifdef MAIL_USE_MMDF
extern int lk_open (), lk_close ();
#endif

#if !defined (MAIL_USE_SYSTEM_LOCK) && !defined (MAIL_USE_MMDF) && \
        (defined (HAVE_LIBMAIL) || defined (HAVE_LIBLOCKFILE)) && \
        defined (HAVE_MAILLOCK_H)
#include <maillock.h>
/* We can't use maillock unless we know what directory system mail
   files appear in. */
#ifdef MAILDIR
#define MAIL_USE_MAILLOCK
static char *mail_spool_name ();
#endif
#endif

#ifndef errno
extern int errno;
#endif
char *strerror ();
#ifdef HAVE_INDEX
extern char *index __P ((const char *, int));
#endif
#ifdef HAVE_RINDEX
extern char *rindex __P((const char *, int));
#endif

void fatal ();
void error ();
void pfatal_with_name ();
void pfatal_and_delete ();
char *concat ();
long *xmalloc ();
int popmail ();
int pop_retr ();
int mbx_write ();
int mbx_delimit_begin ();
int mbx_delimit_end ();

/* Nonzero means this is name of a lock file to delete on fatal error.  */
char *delete_lockname;

#ifdef MEADOW
#define USE_POP_OPT
#endif /* MEADOW */

int
main (argc, argv)
     int argc;
     char **argv;
{
  char *inname, *outname;
  int indesc, outdesc;
  int nread;
  WAITTYPE status;
  int c, preserve_mail = 0;

#ifndef MAIL_USE_SYSTEM_LOCK
  struct stat st;
  long now;
  int tem;
  char *lockname, *p;
  char *tempname;
  int desc;
#endif /* not MAIL_USE_SYSTEM_LOCK */

#ifdef MAIL_USE_MAILLOCK
  char *spool_name;
#endif

#ifdef MAIL_USE_POP
  int pop_reverse_order = 0;
# define ARGSTR "pr"
#else /* ! MAIL_USE_POP */
# define ARGSTR "p"
#endif /* MAIL_USE_POP */

#ifdef WINDOWSNT
  /* Ensure all file i/o is in binary mode. */
  _fmode = _O_BINARY;
#endif

  delete_lockname = 0;

  while ((c = getopt (argc, argv, ARGSTR)) != EOF)
    {
      switch (c) {
#ifdef MAIL_USE_POP
      case 'r':
        pop_reverse_order = 1;
        break;
#endif
      case 'p':
        preserve_mail++;
        break;
      default:
        exit (EXIT_FAILURE);
      }
    }

  if (
#ifdef MAIL_USE_POP
      (argc - optind < 2) || (argc - optind > 3)
#else
      (argc - optind != 2)
#endif
      )
    {
#ifdef MAIL_USE_POP
      fprintf (stderr, "Usage: movemail [-p] inbox destfile%s\n",
               " [POP-password]");
#else
      fprintf (stderr, "Usage: movemail [-p] inbox destfile%s\n", "");
#endif
      exit (EXIT_FAILURE);
    }

  inname = argv[optind];
  outname = argv[optind+1];

#ifdef MAIL_USE_MMDF
  mmdf_init (argv[0]);
#endif

  if (*outname == 0)
    fatal ("Destination file name is empty", 0, 0);

  /* Check access to output file.  */
  if (access (outname, F_OK) == 0 && access (outname, W_OK) != 0)
    pfatal_with_name (outname);

  /* Also check that outname's directory is writable to the real uid.  */
  {
    char *buf = (char *) xmalloc (strlen (outname) + 1);
    char *p;
    strcpy (buf, outname);
    p = buf + strlen (buf);
    while (p > buf && !IS_DIRECTORY_SEP (p[-1]))
      *--p = 0;
    if (p == buf)
      *p++ = '.';
    if (access (buf, W_OK) != 0)
      pfatal_with_name (buf);
    free (buf);
  }

#ifdef MAIL_USE_POP
  if (!strncmp (inname, "po:", 3))
    {
      int status;

      status = popmail (inname + 3, outname, preserve_mail,
                        (argc - optind == 3) ? argv[optind+2] : NULL,
                        pop_reverse_order);
      exit (status);
    }

  setuid (getuid ());
#endif /* MAIL_USE_POP */

#ifndef DISABLE_DIRECT_ACCESS

  /* Check access to input file.  */
  if (access (inname, R_OK | W_OK) != 0)
    pfatal_with_name (inname);

#ifndef MAIL_USE_MMDF
#ifndef MAIL_USE_SYSTEM_LOCK
#ifdef MAIL_USE_MAILLOCK
  spool_name = mail_spool_name (inname);
  if (! spool_name)
#endif
    {
      /* Use a lock file named after our first argument with .lock appended:
         If it exists, the mail file is locked.  */
      /* Note: this locking mechanism is *required* by the mailer
         (on systems which use it) to prevent loss of mail.

         On systems that use a lock file, extracting the mail without locking
         WILL occasionally cause loss of mail due to timing errors!

         So, if creation of the lock file fails
         due to access permission on the mail spool directory,
         you simply MUST change the permission
         and/or make movemail a setgid program
         so it can create lock files properly.

         You might also wish to verify that your system is one
         which uses lock files for this purpose.  Some systems use other methods.

         If your system uses the `flock' system call for mail locking,
         define MAIL_USE_SYSTEM_LOCK in config.h or the s-*.h file
         and recompile movemail.  If the s- file for your system
         should define MAIL_USE_SYSTEM_LOCK but does not, send a bug report
         to bug-gnu-emacs@prep.ai.mit.edu so we can fix it.  */

      lockname = concat (inname, ".lock", "");
      tempname = (char *) xmalloc (strlen (inname) + strlen ("EXXXXXX") + 1);
      strcpy (tempname, inname);
      p = tempname + strlen (tempname);
      while (p != tempname && !IS_DIRECTORY_SEP (p[-1]))
        p--;
      *p = 0;
      strcpy (p, "EXXXXXX");
      mktemp (tempname);
      unlink (tempname);

      while (1)
        {
          /* Create the lock file, but not under the lock file name.  */
          /* Give up if cannot do that.  */
          desc = open (tempname, O_WRONLY | O_CREAT | O_EXCL, 0666);
          if (desc < 0)
            {
              char *message = (char *) xmalloc (strlen (tempname) + 50);
              sprintf (message, "creating %s, which would become the lock file",
                       tempname);
              pfatal_with_name (message);
            }
          close (desc);

          tem = link (tempname, lockname);
          unlink (tempname);
          if (tem >= 0)
            break;
          sleep (1);

          /* If lock file is five minutes old, unlock it.
             Five minutes should be good enough to cope with crashes
             and wedgitude, and long enough to avoid being fooled
             by time differences between machines.  */
          if (stat (lockname, &st) >= 0)
            {
              now = time (0);
              if (st.st_ctime < now - 300)
                unlink (lockname);
            }
        }

      delete_lockname = lockname;
    }
#endif /* not MAIL_USE_SYSTEM_LOCK */
#endif /* not MAIL_USE_MMDF */

  if (fork () == 0)
    {
      int lockcount = 0;
      int status = 0;
#if defined (MAIL_USE_MAILLOCK) && defined (HAVE_TOUCHLOCK)
      long touched_lock, now;
#endif

      setuid (getuid ());

#ifndef MAIL_USE_MMDF
#ifdef MAIL_USE_SYSTEM_LOCK
      indesc = open (inname, O_RDWR);
#else  /* if not MAIL_USE_SYSTEM_LOCK */
      indesc = open (inname, O_RDONLY);
#endif /* not MAIL_USE_SYSTEM_LOCK */
#else  /* MAIL_USE_MMDF */
      indesc = lk_open (inname, O_RDONLY, 0, 0, 10);
#endif /* MAIL_USE_MMDF */

      if (indesc < 0)
        pfatal_with_name (inname);

#if defined (BSD_SYSTEM) || defined (XENIX)
      /* In case movemail is setuid to root, make sure the user can
         read the output file.  */
      /* This is desirable for all systems
         but I don't want to assume all have the umask system call */
      umask (umask (0) & 0333);
#endif /* BSD_SYSTEM || XENIX */
      outdesc = open (outname, O_WRONLY | O_CREAT | O_EXCL, 0666);
      if (outdesc < 0)
        pfatal_with_name (outname);

      /* This label exists so we can retry locking
         after a delay, if it got EAGAIN or EBUSY.  */
    retry_lock:

      /* Try to lock it.  */
#ifdef MAIL_USE_MAILLOCK
      if (spool_name)
        {
          /* The "0 - " is to make it a negative number if maillock returns
             non-zero. */
          status = 0 - maillock (spool_name, 1);
#ifdef HAVE_TOUCHLOCK
          touched_lock = time (0);
#endif
          lockcount = 5;
        }
      else
#endif /* MAIL_USE_MAILLOCK */
        {
#ifdef MAIL_USE_SYSTEM_LOCK
#ifdef MAIL_USE_LOCKF
          status = lockf (indesc, F_LOCK, 0);
#else /* not MAIL_USE_LOCKF */
#ifdef XENIX
          status = locking (indesc, LK_RLCK, 0L);
#else
#ifdef WINDOWSNT
          status = locking (indesc, LK_RLCK, -1L);
#else
          status = flock (indesc, LOCK_EX);
#endif
#endif
#endif /* not MAIL_USE_LOCKF */
#endif /* MAIL_USE_SYSTEM_LOCK */
        }

      /* If it fails, retry up to 5 times
         for certain failure codes.  */
      if (status < 0)
        {
          if (++lockcount <= 5)
            {
#ifdef EAGAIN
              if (errno == EAGAIN)
                {
                  sleep (1);
                  goto retry_lock;
                }
#endif
#ifdef EBUSY
              if (errno == EBUSY)
                {
                  sleep (1);
                  goto retry_lock;
                }
#endif
            }

          pfatal_with_name (inname);
        }

      {
        char buf[1024];

        while (1)
          {
            nread = read (indesc, buf, sizeof buf);
            if (nread < 0)
              pfatal_with_name (inname);
            if (nread != write (outdesc, buf, nread))
              {
                int saved_errno = errno;
                unlink (outname);
                errno = saved_errno;
                pfatal_with_name (outname);
              }
            if (nread < sizeof buf)
              break;
#if defined (MAIL_USE_MAILLOCK) && defined (HAVE_TOUCHLOCK)
            if (spool_name)
              {
                now = time (0);
                if (now - touched_lock > 60)
                  {
                    touchlock ();
                    touched_lock = now;
                  }
              }
#endif /* MAIL_USE_MAILLOCK */
          }
      }

#ifdef BSD_SYSTEM
      if (fsync (outdesc) < 0)
        pfatal_and_delete (outname);
#endif

      /* Check to make sure no errors before we zap the inbox.  */
      if (close (outdesc) != 0)
        pfatal_and_delete (outname);

#ifdef MAIL_USE_SYSTEM_LOCK
      if (! preserve_mail)
        {
#if defined (STRIDE) || defined (XENIX)
          /* Stride, xenix have file locking, but no ftruncate.
             This mess will do. */
          close (open (inname, O_CREAT | O_TRUNC | O_RDWR, 0666));
#else
          ftruncate (indesc, 0L);
#endif /* STRIDE or XENIX */
        }
#endif /* MAIL_USE_SYSTEM_LOCK */

#ifdef MAIL_USE_MMDF
      lk_close (indesc, 0, 0, 0);
#else
      close (indesc);
#endif

#ifndef MAIL_USE_SYSTEM_LOCK
      if (! preserve_mail)
        {
          /* Delete the input file; if we can't, at least get rid of its
             contents.  */
#ifdef MAIL_UNLINK_SPOOL
          /* This is generally bad to do, because it destroys the permissions
             that were set on the file.  Better to just empty the file.  */
          if (unlink (inname) < 0 && errno != ENOENT)
#endif /* MAIL_UNLINK_SPOOL */
            creat (inname, 0600);
        }
#endif /* not MAIL_USE_SYSTEM_LOCK */

#ifdef MAIL_USE_MAILLOCK
      /* This has to occur in the child, i.e., in the process that
         acquired the lock! */
      if (spool_name)
        mailunlock ();
#endif
      exit (EXIT_SUCCESS);
    }

  wait (&status);
  if (!WIFEXITED (status))
    exit (EXIT_FAILURE);
  else if (WRETCODE (status) != 0)
    exit (WRETCODE (status));

#if !defined (MAIL_USE_MMDF) && !defined (MAIL_USE_SYSTEM_LOCK)
#ifdef MAIL_USE_MAILLOCK
  if (! spool_name)
#endif /* MAIL_USE_MAILLOCK */
    unlink (lockname);
#endif /* not MAIL_USE_MMDF and not MAIL_USE_SYSTEM_LOCK */

#endif /* ! DISABLE_DIRECT_ACCESS */

  return EXIT_SUCCESS;
}

#ifdef MAIL_USE_MAILLOCK
/* This function uses stat to confirm that the mail directory is
   identical to the directory of the input file, rather than just
   string-comparing the two paths, because one or both of them might
   be symbolic links pointing to some other directory. */
static char *
mail_spool_name (inname)
     char *inname;
{
  struct stat stat1, stat2;
  char *indir, *fname;
  int status;

  if (! (fname = rindex (inname, '/')))
    return NULL;

  fname++;

  if (stat (MAILDIR, &stat1) < 0)
    return NULL;

  indir = (char *) xmalloc (fname - inname + 1);
  strncpy (indir, inname, fname - inname);
  indir[fname-inname] = '\0';


  status = stat (indir, &stat2);

  free (indir);

  if (status < 0)
    return NULL;

  if (stat1.st_dev == stat2.st_dev
      && stat1.st_ino == stat2.st_ino)
    return fname;

  return NULL;
}
#endif /* MAIL_USE_MAILLOCK */

/* Print error message and exit.  */

void
fatal (s1, s2, s3)
     char *s1, *s2, *s3;
{
  if (delete_lockname)
    unlink (delete_lockname);
  error (s1, s2, s3);
  exit (EXIT_FAILURE);
}

/* Print error message.  `s1' is printf control string, `s2' and `s3'
   are args for it or null. */

void
error (s1, s2, s3)
     char *s1, *s2, *s3;
{
  fprintf (stderr, "movemail: ");
  if (s3)
    fprintf (stderr, s1, s2, s3);
  else if (s2)
    fprintf (stderr, s1, s2);
  else
    fprintf (stderr, s1);
  fprintf (stderr, "\n");
}

void
pfatal_with_name (name)
     char *name;
{
  fatal ("%s for %s", strerror (errno), name);
}

void
pfatal_and_delete (name)
     char *name;
{
  char *s = strerror (errno);
  unlink (name);
  fatal ("%s for %s", s, name);
}

/* Return a newly-allocated string whose contents concatenate those of s1, s2, s3.  */

char *
concat (s1, s2, s3)
     char *s1, *s2, *s3;
{
  int len1 = strlen (s1), len2 = strlen (s2), len3 = strlen (s3);
  char *result = (char *) xmalloc (len1 + len2 + len3 + 1);

  strcpy (result, s1);
  strcpy (result + len1, s2);
  strcpy (result + len1 + len2, s3);
  *(result + len1 + len2 + len3) = 0;