gnupg/common/iobuf.c

/* iobuf.c  -  File Handling for OpenPGP.
 * Copyright (C) 1998, 1999, 2000, 2001, 2003, 2004, 2006, 2007, 2008,
 *               2009, 2010, 2011  Free Software Foundation, Inc.
 * Copyright (C) 2015  g10 Code GmbH
 *
 * This file is part of GnuPG.
 *
 * This file is free software; you can redistribute it and/or modify
 * it under the terms of either
 *
 *   - the GNU Lesser General Public License as published by the Free
 *     Software Foundation; either version 3 of the License, or (at
 *     your option) any later version.
 *
 * or
 *
 *   - 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.
 *
 * or both in parallel, as here.
 *
 * This file 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, see <http://www.gnu.org/licenses/>.
 */

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include <assert.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#ifdef HAVE_W32_SYSTEM
# ifdef HAVE_WINSOCK2_H
#  include <winsock2.h>
# endif
# include <windows.h>
#endif
#ifdef __riscos__
# include <kernel.h>
# include <swis.h>
#endif /* __riscos__ */

#include <assuan.h>

#include "util.h"
#include "sysutils.h"
#include "iobuf.h"

/*-- Begin configurable part.  --*/

/* The size of the internal buffers.
   NOTE: If you change this value you MUST also adjust the regression
   test "armored_key_8192" in armor.test! */
#define IOBUF_BUFFER_SIZE  8192

/* To avoid a potential DoS with compression packets we better limit
   the number of filters in a chain.  */
#define MAX_NESTING_FILTER 64

/*-- End configurable part.  --*/


#ifdef HAVE_W32_SYSTEM
# ifdef HAVE_W32CE_SYSTEM
#  define FD_FOR_STDIN  (es_fileno (es_stdin))
#  define FD_FOR_STDOUT (es_fileno (es_stdout))
# else
#  define FD_FOR_STDIN  (GetStdHandle (STD_INPUT_HANDLE))
#  define FD_FOR_STDOUT (GetStdHandle (STD_OUTPUT_HANDLE))
# endif
#else /*!HAVE_W32_SYSTEM*/
# define FD_FOR_STDIN  (0)
# define FD_FOR_STDOUT (1)
#endif /*!HAVE_W32_SYSTEM*/


/* The context used by the file filter.  */
typedef struct
{
  gnupg_fd_t fp;       /* Open file pointer or handle.  */
  int keep_open;
  int no_cache;
  int eof_seen;
  int print_only_name; /* Flags indicating that fname is not a real file.  */
  char fname[1];       /* Name of the file.  */
} file_filter_ctx_t;

/* The context used by the estream filter.  */
typedef struct
{
  estream_t fp;        /* Open estream handle.  */
  int keep_open;
  int no_cache;
  int eof_seen;
  int print_only_name; /* Flags indicating that fname is not a real file.  */
  char fname[1];       /* Name of the file.  */
} file_es_filter_ctx_t;


/* Object to control the "close cache".  */
struct close_cache_s
{
  struct close_cache_s *next;
  gnupg_fd_t fp;
  char fname[1];
};
typedef struct close_cache_s *close_cache_t;
static close_cache_t close_cache;



#ifdef HAVE_W32_SYSTEM
typedef struct
{
  int sock;
  int keep_open;
  int no_cache;
  int eof_seen;
  int print_only_name;	/* Flag indicating that fname is not a real file.  */
  char fname[1];	/* Name of the file */

} sock_filter_ctx_t;
#endif /*HAVE_W32_SYSTEM*/

/* The first partial length header block must be of size 512
 * to make it easier (and efficienter) we use a min. block size of 512
 * for all chunks (but the last one) */
#define OP_MIN_PARTIAL_CHUNK	  512
#define OP_MIN_PARTIAL_CHUNK_2POW 9

/* The context we use for the block filter (used to handle OpenPGP
   length information header).  */
typedef struct
{
  int use;
  size_t size;
  size_t count;
  int partial;	   /* 1 = partial header, 2 in last partial packet.  */
  char *buffer;	   /* Used for partial header.  */
  size_t buflen;   /* Used size of buffer.  */
  int first_c;	   /* First character of a partial header (which is > 0).  */
  int eof;
}
block_filter_ctx_t;


/* Global flag to tell whether special file names are enabled.  See
   gpg.c for an explanation of these file names.  FIXME: it does not
   belong into the iobuf subsystem. */
static int special_names_enabled;

/* Local prototypes.  */
static int underflow (iobuf_t a, int clear_pending_eof);
static int translate_file_handle (int fd, int for_write);

/* Sends any pending data to the filter's FILTER function.  Note: this
   works on the filter and not on the whole pipeline.  That is,
   iobuf_flush doesn't necessarily cause data to be written to any
   underlying file; it just causes any data buffered at the filter A
   to be sent to A's filter function.

   If A is a IOBUF_TEMP filter, then this also enlarges the buffer by
   IOBUF_BUFFER_SIZE.

   May only be called on an IOBUF_OUTPUT or IOBUF_TEMP filters.  */
static int filter_flush (iobuf_t a);



/* This is a replacement for strcmp.  Under W32 it does not
   distinguish between backslash and slash.  */
static int
fd_cache_strcmp (const char *a, const char *b)
{
#ifdef HAVE_DOSISH_SYSTEM
  for (; *a && *b; a++, b++)
    {
      if (*a != *b && !((*a == '/' && *b == '\\')
                        || (*a == '\\' && *b == '/')) )
        break;
    }
  return *(const unsigned char *)a - *(const unsigned char *)b;
#else
  return strcmp (a, b);
#endif
}

/*
 * Invalidate (i.e. close) a cached iobuf
 */
static int
fd_cache_invalidate (const char *fname)
{
  close_cache_t cc;
  int rc = 0;

  assert (fname);
  if (DBG_IOBUF)
    log_debug ("fd_cache_invalidate (%s)\n", fname);

  for (cc = close_cache; cc; cc = cc->next)
    {
      if (cc->fp != GNUPG_INVALID_FD && !fd_cache_strcmp (cc->fname, fname))
	{
	  if (DBG_IOBUF)
	    log_debug ("                did (%s)\n", cc->fname);
#ifdef HAVE_W32_SYSTEM
	  if (!CloseHandle (cc->fp))
            rc = -1;
#else
	  rc = close (cc->fp);
#endif
	  cc->fp = GNUPG_INVALID_FD;
	}
    }
  return rc;
}


/* Try to sync changes to the disk.  This is to avoid data loss during
   a system crash in write/close/rename cycle on some file
   systems.  */
static int
fd_cache_synchronize (const char *fname)
{
  int err = 0;

#ifdef HAVE_FSYNC
  close_cache_t cc;

  if (DBG_IOBUF)
    log_debug ("fd_cache_synchronize (%s)\n", fname);

  for (cc=close_cache; cc; cc = cc->next )
    {
      if (cc->fp != GNUPG_INVALID_FD && !fd_cache_strcmp (cc->fname, fname))
	{
	  if (DBG_IOBUF)
	    log_debug ("                 did (%s)\n", cc->fname);

	  err = fsync (cc->fp);
	}
    }
#else
  (void)fname;
#endif /*HAVE_FSYNC*/

  return err;
}


static gnupg_fd_t
direct_open (const char *fname, const char *mode, int mode700)
{
#ifdef HAVE_W32_SYSTEM
  unsigned long da, cd, sm;
  HANDLE hfile;

  /* Note, that we do not handle all mode combinations */

  /* According to the ReactOS source it seems that open() of the
   * standard MSW32 crt does open the file in shared mode which is
   * something new for MS applications ;-)
   */
  if (strchr (mode, '+'))
    {
      if (fd_cache_invalidate (fname))
        return GNUPG_INVALID_FD;
      da = GENERIC_READ | GENERIC_WRITE;
      cd = OPEN_EXISTING;
      sm = FILE_SHARE_READ | FILE_SHARE_WRITE;
    }
  else if (strchr (mode, 'w'))
    {
      if (fd_cache_invalidate (fname))
        return GNUPG_INVALID_FD;
      da = GENERIC_WRITE;
      cd = CREATE_ALWAYS;
      sm = FILE_SHARE_WRITE;
    }
  else
    {
      da = GENERIC_READ;
      cd = OPEN_EXISTING;
      sm = FILE_SHARE_READ;
    }

#ifdef HAVE_W32CE_SYSTEM
  {
    wchar_t *wfname = utf8_to_wchar (fname);
    if (wfname)
      {
        hfile = CreateFile (wfname, da, sm, NULL, cd,
                            FILE_ATTRIBUTE_NORMAL, NULL);
        xfree (wfname);
      }
    else
      hfile = INVALID_HANDLE_VALUE;
  }
#else
  hfile = CreateFile (fname, da, sm, NULL, cd, FILE_ATTRIBUTE_NORMAL, NULL);
#endif
  return hfile;

#else /*!HAVE_W32_SYSTEM*/

  int oflag;
  int cflag = S_IRUSR | S_IWUSR;

  if (!mode700)
    cflag |= S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH;

  /* Note, that we do not handle all mode combinations */
  if (strchr (mode, '+'))
    {
      if (fd_cache_invalidate (fname))
        return GNUPG_INVALID_FD;
      oflag = O_RDWR;
    }
  else if (strchr (mode, 'w'))
    {
      if (fd_cache_invalidate (fname))
        return GNUPG_INVALID_FD;
      oflag = O_WRONLY | O_CREAT | O_TRUNC;
    }
  else
    {
      oflag = O_RDONLY;
    }
#ifdef O_BINARY
  if (strchr (mode, 'b'))
    oflag |= O_BINARY;
#endif

#ifdef __riscos__
  {
    struct stat buf;

    /* Don't allow iobufs on directories */
    if (!stat (fname, &buf) && S_ISDIR (buf.st_mode) && !S_ISREG (buf.st_mode))
      return __set_errno (EISDIR);
  }
#endif
  return open (fname, oflag, cflag);

#endif /*!HAVE_W32_SYSTEM*/
}


/*
 * Instead of closing an FD we keep it open and cache it for later reuse
 * Note that this caching strategy only works if the process does not chdir.
 */
static void
fd_cache_close (const char *fname, gnupg_fd_t fp)
{
  close_cache_t cc;

  assert (fp);
  if (!fname || !*fname)
    {
#ifdef HAVE_W32_SYSTEM
      CloseHandle (fp);
#else
      close (fp);
#endif
      if (DBG_IOBUF)
	log_debug ("fd_cache_close (%d) real\n", (int)fp);
      return;
    }
  /* try to reuse a slot */
  for (cc = close_cache; cc; cc = cc->next)
    {
      if (cc->fp == GNUPG_INVALID_FD && !fd_cache_strcmp (cc->fname, fname))
	{
	  cc->fp = fp;
	  if (DBG_IOBUF)
	    log_debug ("fd_cache_close (%s) used existing slot\n", fname);
	  return;
	}
    }
  /* add a new one */
  if (DBG_IOBUF)
    log_debug ("fd_cache_close (%s) new slot created\n", fname);
  cc = xcalloc (1, sizeof *cc + strlen (fname));
  strcpy (cc->fname, fname);
  cc->fp = fp;
  cc->next = close_cache;
  close_cache = cc;
}

/*
 * Do an direct_open on FNAME but first try to reuse one from the fd_cache
 */
static gnupg_fd_t
fd_cache_open (const char *fname, const char *mode)
{
  close_cache_t cc;

  assert (fname);
  for (cc = close_cache; cc; cc = cc->next)
    {
      if (cc->fp != GNUPG_INVALID_FD && !fd_cache_strcmp (cc->fname, fname))
	{
	  gnupg_fd_t fp = cc->fp;
	  cc->fp = GNUPG_INVALID_FD;
	  if (DBG_IOBUF)
	    log_debug ("fd_cache_open (%s) using cached fp\n", fname);
#ifdef HAVE_W32_SYSTEM
	  if (SetFilePointer (fp, 0, NULL, FILE_BEGIN) == 0xffffffff)
	    {
	      log_error ("rewind file failed on handle %p: ec=%d\n",
			 fp, (int) GetLastError ());
	      fp = GNUPG_INVALID_FD;
	    }
#else
	  if (lseek (fp, 0, SEEK_SET) == (off_t) - 1)
	    {
	      log_error ("can't rewind fd %d: %s\n", fp, strerror (errno));
	      fp = GNUPG_INVALID_FD;
	    }
#endif
	  return fp;
	}
    }
  if (DBG_IOBUF)
    log_debug ("fd_cache_open (%s) not cached\n", fname);
  return direct_open (fname, mode, 0);
}


/****************
 * Read data from a file into buf which has an allocated length of *LEN.
 * return the number of read bytes in *LEN. OPAQUE is the FILE * of
 * the stream. A is not used.
 * control may be:
 * IOBUFCTRL_INIT: called just before the function is linked into the
 *		   list of function. This can be used to prepare internal
 *		   data structures of the function.
 * IOBUFCTRL_FREE: called just before the function is removed from the
 *		    list of functions and can be used to release internal
 *		    data structures or close a file etc.
 * IOBUFCTRL_UNDERFLOW: called by iobuf_underflow to fill the buffer
 *		    with new stuff. *RET_LEN is the available size of the
 *		    buffer, and should be set to the number of bytes
 *		    which were put into the buffer. The function
 *		    returns 0 to indicate success, -1 on EOF and
 *		    GPG_ERR_xxxxx for other errors.
 *
 * IOBUFCTRL_FLUSH: called by iobuf_flush() to write out the collected stuff.
 *		    *RET_LAN is the number of bytes in BUF.
 *
 * IOBUFCTRL_CANCEL: send to all filters on behalf of iobuf_cancel.  The
 *		    filter may take appropriate action on this message.
 */
static int
file_filter (void *opaque, int control, iobuf_t chain, byte * buf,
	     size_t * ret_len)
{
  file_filter_ctx_t *a = opaque;
  gnupg_fd_t f = a->fp;
  size_t size = *ret_len;
  size_t nbytes = 0;
  int rc = 0;

  (void)chain; /* Not used.  */

  if (control == IOBUFCTRL_UNDERFLOW)
    {
      assert (size); /* We need a buffer.  */
      if (a->eof_seen)
	{
	  rc = -1;
	  *ret_len = 0;
	}
      else
	{
#ifdef HAVE_W32_SYSTEM
	  unsigned long nread;

	  nbytes = 0;
	  if (!ReadFile (f, buf, size, &nread, NULL))
	    {
	      int ec = (int) GetLastError ();
	      if (ec != ERROR_BROKEN_PIPE)
		{
		  rc = gpg_error_from_errno (ec);
		  log_error ("%s: read error: ec=%d\n", a->fname, ec);
		}
	    }
	  else if (!nread)
	    {
	      a->eof_seen = 1;
	      rc = -1;
	    }
	  else
	    {
	      nbytes = nread;
	    }

#else

	  int n;

	  nbytes = 0;
	  do
	    {
	      n = read (f, buf, size);
	    }
	  while (n == -1 && errno == EINTR);
	  if (n == -1)
	    {			/* error */
	      if (errno != EPIPE)
		{
		  rc = gpg_error_from_syserror ();
		  log_error ("%s: read error: %s\n",
			     a->fname, strerror (errno));
		}
	    }
	  else if (!n)
	    {			/* eof */
	      a->eof_seen = 1;
	      rc = -1;
	    }
	  else
	    {
	      nbytes = n;
	    }
#endif
	  *ret_len = nbytes;
	}
    }
  else if (control == IOBUFCTRL_FLUSH)
    {
      if (size)
	{
#ifdef HAVE_W32_SYSTEM
	  byte *p = buf;
	  unsigned long n;

	  nbytes = size;
	  do
	    {
	      if (size && !WriteFile (f, p, nbytes, &n, NULL))
		{
		  int ec = (int) GetLastError ();
		  rc = gpg_error_from_errno (ec);
		  log_error ("%s: write error: ec=%d\n", a->fname, ec);
		  break;
		}
	      p += n;
	      nbytes -= n;
	    }
	  while (nbytes);
	  nbytes = p - buf;
#else
	  byte *p = buf;
	  int n;

	  nbytes = size;
	  do
	    {
	      do
		{
		  n = write (f, p, nbytes);
		}
	      while (n == -1 && errno == EINTR);
	      if (n > 0)
		{
		  p += n;
		  nbytes -= n;
		}
	    }
	  while (n != -1 && nbytes);
	  if (n == -1)
	    {
	      rc = gpg_error_from_syserror ();
	      log_error ("%s: write error: %s\n", a->fname, strerror (errno));
	    }
	  nbytes = p - buf;
#endif
	}
      *ret_len = nbytes;
    }
  else if (control == IOBUFCTRL_INIT)
    {
      a->eof_seen = 0;
      a->keep_open = 0;
      a->no_cache = 0;
    }
  else if (control == IOBUFCTRL_DESC)
    {
      *(char **) buf = "file_filter(fd)";
    }
  else if (control == IOBUFCTRL_FREE)
    {
      if (f != FD_FOR_STDIN && f != FD_FOR_STDOUT)
	{
	  if (DBG_IOBUF)
	    log_debug ("%s: close fd/handle %d\n", a->fname, FD2INT (f));
	  if (!a->keep_open)
	    fd_cache_close (a->no_cache ? NULL : a->fname, f);
	}
      f = GNUPG_INVALID_FD;
      xfree (a); /* We can free our context now. */
    }

  return rc;
}


/* Similar to file_filter but using the estream system.  */
static int
file_es_filter (void *opaque, int control, iobuf_t chain, byte * buf,
                size_t * ret_len)
{
  file_es_filter_ctx_t *a = opaque;
  estream_t f = a->fp;
  size_t size = *ret_len;
  size_t nbytes = 0;
  int rc = 0;

  (void)chain; /* Not used.  */

  if (control == IOBUFCTRL_UNDERFLOW)
    {
      assert (size); /* We need a buffer.  */
      if (a->eof_seen)
	{
	  rc = -1;
	  *ret_len = 0;
	}
      else
	{
          nbytes = 0;
          rc = es_read (f, buf, size, &nbytes);
	  if (rc == -1)
	    {			/* error */
              rc = gpg_error_from_syserror ();
              log_error ("%s: read error: %s\n", a->fname, strerror (errno));
	    }
	  else if (!nbytes)
	    {			/* eof */
	      a->eof_seen = 1;
	      rc = -1;
	    }
	  *ret_len = nbytes;
	}
    }
  else if (control == IOBUFCTRL_FLUSH)
    {
      if (size)
	{
	  byte *p = buf;
	  size_t nwritten;

	  nbytes = size;
	  do
	    {
              nwritten = 0;
              if (es_write (f, p, nbytes, &nwritten))
                {
                  rc = gpg_error_from_syserror ();
                  log_error ("%s: write error: %s\n",
                             a->fname, strerror (errno));
                  break;
                }
              p += nwritten;
              nbytes -= nwritten;
	    }
	  while (nbytes);
	  nbytes = p - buf;
	}
      *ret_len = nbytes;
    }
  else if (control == IOBUFCTRL_INIT)
    {
      a->eof_seen = 0;
      a->no_cache = 0;
    }
  else if (control == IOBUFCTRL_DESC)
    {
      *(char **) buf = "estream_filter";
    }
  else if (control == IOBUFCTRL_FREE)
    {
      if (f != es_stdin && f != es_stdout)
	{
	  if (DBG_IOBUF)
	    log_debug ("%s: es_fclose %p\n", a->fname, f);
	  if (!a->keep_open)
	    es_fclose (f);
	}
      f = NULL;
      xfree (a); /* We can free our context now. */
    }

  return rc;
}


#ifdef HAVE_W32_SYSTEM
/* Because network sockets are special objects under Lose32 we have to
   use a dedicated filter for them. */
static int
sock_filter (void *opaque, int control, iobuf_t chain, byte * buf,
	     size_t * ret_len)
{
  sock_filter_ctx_t *a = opaque;
  size_t size = *ret_len;
  size_t nbytes = 0;
  int rc = 0;

  (void)chain;

  if (control == IOBUFCTRL_UNDERFLOW)
    {
      assert (size);		/* need a buffer */
      if (a->eof_seen)
	{
	  rc = -1;
	  *ret_len = 0;
	}
      else
	{
	  int nread;

	  nread = recv (a->sock, buf, size, 0);
	  if (nread == SOCKET_ERROR)
	    {
	      int ec = (int) WSAGetLastError ();
	      rc = gpg_error_from_errno (ec);
	      log_error ("socket read error: ec=%d\n", ec);
	    }
	  else if (!nread)
	    {
	      a->eof_seen = 1;
	      rc = -1;
	    }
	  else
	    {
	      nbytes = nread;
	    }
	  *ret_len = nbytes;
	}
    }
  else if (control == IOBUFCTRL_FLUSH)
    {
      if (size)
	{
	  byte *p = buf;
	  int n;

	  nbytes = size;
	  do
	    {
	      n = send (a->sock, p, nbytes, 0);
	      if (n == SOCKET_ERROR)
		{
		  int ec = (int) WSAGetLastError ();
		  rc = gpg_error_from_errno (ec);
		  log_error ("socket write error: ec=%d\n", ec);
		  break;
		}
	      p += n;
	      nbytes -= n;
	    }
	  while (nbytes);
	  nbytes = p - buf;
	}
      *ret_len = nbytes;
    }
  else if (control == IOBUFCTRL_INIT)
    {
      a->eof_seen = 0;
      a->keep_open = 0;
      a->no_cache = 0;
    }
  else if (control == IOBUFCTRL_DESC)
    {
      *(char **) buf = "sock_filter";
    }
  else if (control == IOBUFCTRL_FREE)
    {
      if (!a->keep_open)
	closesocket (a->sock);
      xfree (a);		/* we can free our context now */
    }
  return rc;
}
#endif /*HAVE_W32_SYSTEM*/

/****************
 * This is used to implement the block write mode.
 * Block reading is done on a byte by byte basis in readbyte(),
 * without a filter
 */
static int
block_filter (void *opaque, int control, iobuf_t chain, byte * buffer,
	      size_t * ret_len)
{
  block_filter_ctx_t *a = opaque;
  char *buf = (char *)buffer;
  size_t size = *ret_len;
  int c, needed, rc = 0;
  char *p;

  if (control == IOBUFCTRL_UNDERFLOW)
    {
      size_t n = 0;

      p = buf;
      assert (size);		/* need a buffer */
      if (a->eof)		/* don't read any further */
	rc = -1;
      while (!rc && size)
	{
	  if (!a->size)
	    {			/* get the length bytes */
	      if (a->partial == 2)
		{
		  a->eof = 1;
		  if (!n)
		    rc = -1;
		  break;
		}
	      else if (a->partial)
		{
		  /* These OpenPGP introduced huffman like encoded length
		   * bytes are really a mess :-( */
		  if (a->first_c)
		    {
		      c = a->first_c;
		      a->first_c = 0;
		    }
		  else if ((c = iobuf_get (chain)) == -1)
		    {
		      log_error ("block_filter: 1st length byte missing\n");
		      rc = GPG_ERR_BAD_DATA;
		      break;
		    }
		  if (c < 192)
		    {
		      a->size = c;
		      a->partial = 2;
		      if (!a->size)
			{
			  a->eof = 1;
			  if (!n)
			    rc = -1;
			  break;
			}
		    }
		  else if (c < 224)
		    {
		      a->size = (c - 192) * 256;
		      if ((c = iobuf_get (chain)) == -1)
			{
			  log_error
			    ("block_filter: 2nd length byte missing\n");
			  rc = GPG_ERR_BAD_DATA;
			  break;
			}
		      a->size += c + 192;
		      a->partial = 2;
		      if (!a->size)
			{
			  a->eof = 1;
			  if (!n)
			    rc = -1;
			  break;
			}
		    }
		  else if (c == 255)
		    {
		      a->size = (size_t)iobuf_get (chain) << 24;
		      a->size |= iobuf_get (chain) << 16;
		      a->size |= iobuf_get (chain) << 8;
		      if ((c = iobuf_get (chain)) == -1)
			{
			  log_error ("block_filter: invalid 4 byte length\n");
			  rc = GPG_ERR_BAD_DATA;
			  break;
			}
		      a->size |= c;
                      a->partial = 2;
                      if (!a->size)
                        {
                          a->eof = 1;
                          if (!n)
                            rc = -1;
                          break;
			}
		    }
		  else
		    { /* Next partial body length. */
		      a->size = 1 << (c & 0x1f);
		    }
		  /*  log_debug("partial: ctx=%p c=%02x size=%u\n", a, c, a->size); */
		}
	      else
		BUG ();
	    }

	  while (!rc && size && a->size)
	    {
	      needed = size < a->size ? size : a->size;
	      c = iobuf_read (chain, p, needed);
	      if (c < needed)
		{
		  if (c == -1)
		    c = 0;
		  log_error
		    ("block_filter %p: read error (size=%lu,a->size=%lu)\n",
		     a, (ulong) size + c, (ulong) a->size + c);
		  rc = GPG_ERR_BAD_DATA;
		}
	      else
		{
		  size -= c;
		  a->size -= c;
		  p += c;
		  n += c;
		}
	    }
	}
      *ret_len = n;
    }
  else if (control == IOBUFCTRL_FLUSH)
    {
      if (a->partial)
	{			/* the complicated openpgp scheme */
	  size_t blen, n, nbytes = size + a->buflen;

	  assert (a->buflen <= OP_MIN_PARTIAL_CHUNK);
	  if (nbytes < OP_MIN_PARTIAL_CHUNK)
	    {
	      /* not enough to write a partial block out; so we store it */
	      if (!a->buffer)
		a->buffer = xmalloc (OP_MIN_PARTIAL_CHUNK);
	      memcpy (a->buffer + a->buflen, buf, size);
	      a->buflen += size;
	    }
	  else
	    {			/* okay, we can write out something */
	      /* do this in a loop to use the most efficient block lengths */
	      p = buf;
	      do
		{
		  /* find the best matching block length - this is limited
		   * by the size of the internal buffering */
		  for (blen = OP_MIN_PARTIAL_CHUNK * 2,
		       c = OP_MIN_PARTIAL_CHUNK_2POW + 1; blen <= nbytes;
		       blen *= 2, c++)
		    ;
		  blen /= 2;
		  c--;
		  /* write the partial length header */
		  assert (c <= 0x1f);	/*;-) */
		  c |= 0xe0;
		  iobuf_put (chain, c);
		  if ((n = a->buflen))
		    {		/* write stuff from the buffer */
		      assert (n == OP_MIN_PARTIAL_CHUNK);
		      if (iobuf_write (chain, a->buffer, n))
			rc = gpg_error_from_syserror ();
		      a->buflen = 0;
		      nbytes -= n;
		    }
		  if ((n = nbytes) > blen)
		    n = blen;
		  if (n && iobuf_write (chain, p, n))
		    rc = gpg_error_from_syserror ();
		  p += n;
		  nbytes -= n;
		}
	      while (!rc && nbytes >= OP_MIN_PARTIAL_CHUNK);
	      /* store the rest in the buffer */
	      if (!rc && nbytes)
		{
		  assert (!a->buflen);
		  assert (nbytes < OP_MIN_PARTIAL_CHUNK);
		  if (!a->buffer)
		    a->buffer = xmalloc (OP_MIN_PARTIAL_CHUNK);
		  memcpy (a->buffer, p, nbytes);
		  a->buflen = nbytes;
		}
	    }
	}
      else
	BUG ();
    }
  else if (control == IOBUFCTRL_INIT)
    {
      if (DBG_IOBUF)
	log_debug ("init block_filter %p\n", a);
      if (a->partial)
	a->count = 0;
      else if (a->use == IOBUF_INPUT)
	a->count = a->size = 0;
      else
	a->count = a->size;	/* force first length bytes */
      a->eof = 0;
      a->buffer = NULL;
      a->buflen = 0;
    }
  else if (control == IOBUFCTRL_DESC)
    {
      *(char **) buf = "block_filter";
    }
  else if (control == IOBUFCTRL_FREE)
    {
      if (a->use == IOBUF_OUTPUT)
	{			/* write the end markers */
	  if (a->partial)
	    {
	      u32 len;
	      /* write out the remaining bytes without a partial header
	       * the length of this header may be 0 - but if it is
	       * the first block we are not allowed to use a partial header
	       * and frankly we can't do so, because this length must be
	       * a power of 2. This is _really_ complicated because we
	       * have to check the possible length of a packet prior
	       * to it's creation: a chain of filters becomes complicated
	       * and we need a lot of code to handle compressed packets etc.
	       *   :-(((((((
	       */
	      /* construct header */
	      len = a->buflen;
	      /*log_debug("partial: remaining length=%u\n", len ); */
	      if (len < 192)
		rc = iobuf_put (chain, len);
	      else if (len < 8384)
		{
		  if (!(rc = iobuf_put (chain, ((len - 192) / 256) + 192)))
		    rc = iobuf_put (chain, ((len - 192) % 256));
		}
	      else
		{		/* use a 4 byte header */
		  if (!(rc = iobuf_put (chain, 0xff)))
		    if (!(rc = iobuf_put (chain, (len >> 24) & 0xff)))
		      if (!(rc = iobuf_put (chain, (len >> 16) & 0xff)))
			if (!(rc = iobuf_put (chain, (len >> 8) & 0xff)))
			  rc = iobuf_put (chain, len & 0xff);
		}
	      if (!rc && len)
		rc = iobuf_write (chain, a->buffer, len);
	      if (rc)
		{
		  log_error ("block_filter: write error: %s\n",
			     strerror (errno));
		  rc = gpg_error_from_syserror ();
		}
	      xfree (a->buffer);
	      a->buffer = NULL;
	      a->buflen = 0;
	    }
	  else
	    BUG ();
	}
      else if (a->size)
	{
	  log_error ("block_filter: pending bytes!\n");
	}
      if (DBG_IOBUF)
	log_debug ("free block_filter %p\n", a);
      xfree (a);		/* we can free our context now */
    }

  return rc;
}

static const char *
iobuf_desc (iobuf_t a)
{
  size_t dummy_len = 0;
  const char *desc = "?";

  if (! a || ! a->filter)
    return desc;

  a->filter (a->filter_ov, IOBUFCTRL_DESC, NULL,
	     (byte *) & desc, &dummy_len);

  return desc;
}

static void
print_chain (iobuf_t a)
{
  if (!DBG_IOBUF)
    return;
  for (; a; a = a->chain)
    {

      log_debug ("iobuf chain: %d.%d '%s' filter_eof=%d start=%d len=%d\n",
		 a->no, a->subno, iobuf_desc (a), a->filter_eof,
		 (int) a->d.start, (int) a->d.len);
    }
}

int
iobuf_print_chain (iobuf_t a)
{
  print_chain (a);
  return 0;
}

/* Allocate a new io buffer, with no function assigned.

   USE is the desired usage: IOBUF_INPUT for input, IOBUF_OUTPUT for
   output, or IOBUF_TEMP for a temp buffer.

   BUFSIZE is a suggested buffer size.
 */
iobuf_t
iobuf_alloc (int use, size_t bufsize)
{
  iobuf_t a;
  static int number = 0;

  assert (use == IOBUF_INPUT || use == IOBUF_OUTPUT || use == IOBUF_TEMP);

  a = xcalloc (1, sizeof *a);
  a->use = use;
  a->d.buf = xmalloc (bufsize);
  a->d.size = bufsize;
  a->no = ++number;
  a->subno = 0;
  a->real_fname = NULL;
  return a;
}

int
iobuf_close (iobuf_t a)
{
  iobuf_t a_chain;
  size_t dummy_len = 0;
  int rc = 0;

  for (; a; a = a_chain)
    {
      int rc2 = 0;

      a_chain = a->chain;

      if (a->use == IOBUF_OUTPUT && (rc = filter_flush (a)))
	log_error ("filter_flush failed on close: %s\n", gpg_strerror (rc));

      if (DBG_IOBUF)
	log_debug ("iobuf-%d.%d: close '%s'\n",
		   a->no, a->subno, iobuf_desc (a));

      if (a->filter && (rc2 = a->filter (a->filter_ov, IOBUFCTRL_FREE,
					 a->chain, NULL, &dummy_len)))
	log_error ("IOBUFCTRL_FREE failed on close: %s\n", gpg_strerror (rc));
      if (! rc && rc2)
	/* Whoops!  An error occured.  Save it in RC if we haven't
	   already recorded an error.  */
	rc = rc2;

      xfree (a->real_fname);
      if (a->d.buf)
	{
	  memset (a->d.buf, 0, a->d.size);	/* erase the buffer */
	  xfree (a->d.buf);
	}
      xfree (a);
    }
  return rc;
}

int
iobuf_cancel (iobuf_t a)
{
  const char *s;
  iobuf_t a2;
  int rc;
#if defined(HAVE_W32_SYSTEM) || defined(__riscos__)
  char *remove_name = NULL;
#endif

  if (a && a->use == IOBUF_OUTPUT)
    {
      s = iobuf_get_real_fname (a);
      if (s && *s)
	{
#if defined(HAVE_W32_SYSTEM) || defined(__riscos__)
	  remove_name = xstrdup (s);
#else
	  remove (s);
#endif
	}
    }

  /* send a cancel message to all filters */
  for (a2 = a; a2; a2 = a2->chain)
    {
      size_t dummy;
      if (a2->filter)
	a2->filter (a2->filter_ov, IOBUFCTRL_CANCEL, a2->chain, NULL, &dummy);
    }

  rc = iobuf_close (a);
#if defined(HAVE_W32_SYSTEM) || defined(__riscos__)
  if (remove_name)
    {
      /* Argg, MSDOS does not allow to remove open files.  So
       * we have to do it here */
#ifdef HAVE_W32CE_SYSTEM
      wchar_t *wtmp = utf8_to_wchar (remove_name);
      if (wtmp)
        DeleteFile (wtmp);
      xfree (wtmp);
#else
      remove (remove_name);
#endif
      xfree (remove_name);
    }
#endif
  return rc;
}


/****************
 * create a temporary iobuf, which can be used to collect stuff
 * in an iobuf and later be written by iobuf_write_temp() to another
 * iobuf.
 */
iobuf_t
iobuf_temp ()
{
  iobuf_t a;

  a = iobuf_alloc (IOBUF_TEMP, IOBUF_BUFFER_SIZE);

  return a;
}

iobuf_t
iobuf_temp_with_content (const char *buffer, size_t length)
{
  iobuf_t a;
  int i;

  a = iobuf_alloc (IOBUF_INPUT, length);
  /* memcpy (a->d.buf, buffer, length); */
  for (i=0; i < length; i++)
    a->d.buf[i] = buffer[i];
  a->d.len = length;

  return a;
}

void
iobuf_enable_special_filenames (int yes)
{
  special_names_enabled = yes;
}


/* See whether the filename has the form "-&nnnn", where n is a
   non-zero number.  Returns this number or -1 if it is not the
   case.  */
static int
check_special_filename (const char *fname)
{
  if (special_names_enabled && fname && *fname == '-' && fname[1] == '&')
    {
      int i;

      fname += 2;
      for (i = 0; digitp (fname+i); i++)
	;
      if (!fname[i])
	return atoi (fname);
    }
  return -1;
}


/* This fucntion returns true if FNAME indicates a PIPE (stdout or
   stderr) or a special file name if those are enabled. */
int
iobuf_is_pipe_filename (const char *fname)
{
  if (!fname || (*fname=='-' && !fname[1]) )
    return 1;
  return check_special_filename (fname) != -1;
}

static iobuf_t
do_open (const char *fname, int special_filenames,
	 int use, const char *opentype, int mode700)
{
  iobuf_t a;
  gnupg_fd_t fp;
  file_filter_ctx_t *fcx;
  size_t len = 0;
  int print_only = 0;
  int fd;

  if (special_filenames
      /* NULL or '-'.  */
      && (!fname || (*fname == '-' && !fname[1])))
    {
      if (use == IOBUF_INPUT)
	{
	  fp = FD_FOR_STDIN;
	  fname = "[stdin]";
	}
      else
	{
	  fp = FD_FOR_STDOUT;
	  fname = "[stdout]";
	}
      print_only = 1;
    }
  else if (!fname)
    return NULL;
  else if (special_filenames && (fd = check_special_filename (fname)) != -1)
    return iobuf_fdopen (translate_file_handle (fd, use == IOBUF_INPUT ? 0 : 1),
			 opentype);
  else
    {
      if (use == IOBUF_INPUT)
	fp = fd_cache_open (fname, opentype);
      else
	fp = direct_open (fname, opentype, mode700);
      if (fp == GNUPG_INVALID_FD)
	return NULL;
    }

  a = iobuf_alloc (use, IOBUF_BUFFER_SIZE);
  fcx = xmalloc (sizeof *fcx + strlen (fname));
  fcx->fp = fp;
  fcx->print_only_name = print_only;
  strcpy (fcx->fname, fname);
  if (!print_only)
    a->real_fname = xstrdup (fname);
  a->filter = file_filter;
  a->filter_ov = fcx;
  file_filter (fcx, IOBUFCTRL_INIT, NULL, NULL, &len);
  if (DBG_IOBUF)
    log_debug ("iobuf-%d.%d: open '%s' desc=%s fd=%d\n",
	       a->no, a->subno, fname, iobuf_desc (a), FD2INT (fcx->fp));

  return a;
}

/****************
 * Create a head iobuf for reading from a file
 * returns: NULL if an error occures and sets errno
 */
iobuf_t
iobuf_open (const char *fname)
{
  return do_open (fname, 1, IOBUF_INPUT, "rb", 0);
}

iobuf_t
iobuf_create (const char *fname, int mode700)
{
  return do_open (fname, 1, IOBUF_OUTPUT, "wb", mode700);
}

iobuf_t
iobuf_openrw (const char *fname)
{
  return do_open (fname, 0, IOBUF_OUTPUT, "r+b", 0);
}


static iobuf_t
do_iobuf_fdopen (int fd, const char *mode, int keep_open)
{
  iobuf_t a;
  gnupg_fd_t fp;
  file_filter_ctx_t *fcx;
  size_t len;

  fp = INT2FD (fd);

  a = iobuf_alloc (strchr (mode, 'w') ? IOBUF_OUTPUT : IOBUF_INPUT,
		   IOBUF_BUFFER_SIZE);
  fcx = xmalloc (sizeof *fcx + 20);
  fcx->fp = fp;
  fcx->print_only_name = 1;
  fcx->keep_open = keep_open;
  sprintf (fcx->fname, "[fd %d]", fd);
  a->filter = file_filter;
  a->filter_ov = fcx;
  file_filter (fcx, IOBUFCTRL_INIT, NULL, NULL, &len);
  if (DBG_IOBUF)
    log_debug ("iobuf-%d.%d: fdopen%s '%s'\n",
               a->no, a->subno, keep_open? "_nc":"", fcx->fname);
  iobuf_ioctl (a, IOBUF_IOCTL_NO_CACHE, 1, NULL);
  return a;
}


/* Create a head iobuf for reading or writing from/to a file Returns:
 * NULL and sets ERRNO if an error occured.  */
iobuf_t
iobuf_fdopen (int fd, const char *mode)
{
  return do_iobuf_fdopen (fd, mode, 0);
}

iobuf_t
iobuf_fdopen_nc (int fd, const char *mode)
{
  return do_iobuf_fdopen (fd, mode, 1);
}


iobuf_t
iobuf_esopen (estream_t estream, const char *mode, int keep_open)
{
  iobuf_t a;
  file_es_filter_ctx_t *fcx;
  size_t len;

  a = iobuf_alloc (strchr (mode, 'w') ? IOBUF_OUTPUT : IOBUF_INPUT,
		   IOBUF_BUFFER_SIZE);
  fcx = xtrymalloc (sizeof *fcx + 30);
  fcx->fp = estream;
  fcx->print_only_name = 1;
  fcx->keep_open = keep_open;
  sprintf (fcx->fname, "[fd %p]", estream);
  a->filter = file_es_filter;
  a->filter_ov = fcx;
  file_es_filter (fcx, IOBUFCTRL_INIT, NULL, NULL, &len);
  if (DBG_IOBUF)
    log_debug ("iobuf-%d.%d: esopen%s '%s'\n",
               a->no, a->subno, keep_open? "_nc":"", fcx->fname);
  return a;
}


iobuf_t
iobuf_sockopen (int fd, const char *mode)
{
  iobuf_t a;
#ifdef HAVE_W32_SYSTEM
  sock_filter_ctx_t *scx;
  size_t len;

  a = iobuf_alloc (strchr (mode, 'w') ? IOBUF_OUTPUT : IOBUF_INPUT,
		   IOBUF_BUFFER_SIZE);
  scx = xmalloc (sizeof *scx + 25);
  scx->sock = fd;
  scx->print_only_name = 1;
  sprintf (scx->fname, "[sock %d]", fd);
  a->filter = sock_filter;
  a->filter_ov = scx;
  sock_filter (scx, IOBUFCTRL_INIT, NULL, NULL, &len);
  if (DBG_IOBUF)
    log_debug ("iobuf-%d.%d: sockopen '%s'\n", a->no, a->subno, scx->fname);
  iobuf_ioctl (a, IOBUF_IOCTL_NO_CACHE, 1, NULL);
#else
  a = iobuf_fdopen (fd, mode);
#endif
  return a;
}

int
iobuf_ioctl (iobuf_t a, iobuf_ioctl_t cmd, int intval, void *ptrval)
{
  if (cmd == IOBUF_IOCTL_KEEP_OPEN)
    {
      /* Keep system filepointer/descriptor open.  This was used in
         the past by http.c; this ioctl is not directly used
         anymore.  */
      if (DBG_IOBUF)
	log_debug ("iobuf-%d.%d: ioctl '%s' keep_open=%d\n",
		   a ? a->no : -1, a ? a->subno : -1, iobuf_desc (a),
		   intval);
      for (; a; a = a->chain)
	if (!a->chain && a->filter == file_filter)
	  {
	    file_filter_ctx_t *b = a->filter_ov;
	    b->keep_open = intval;
	    return 0;
	  }
#ifdef HAVE_W32_SYSTEM
	else if (!a->chain && a->filter == sock_filter)
	  {
	    sock_filter_ctx_t *b = a->filter_ov;
	    b->keep_open = intval;
	    return 0;
	  }
#endif
    }
  else if (cmd == IOBUF_IOCTL_INVALIDATE_CACHE)
    {
      if (DBG_IOBUF)
	log_debug ("iobuf-*.*: ioctl '%s' invalidate\n",
		   ptrval ? (char *) ptrval : "?");
      if (!a && !intval && ptrval)
	{
	  if (fd_cache_invalidate (ptrval))
            return -1;
	  return 0;
	}
    }
  else if (cmd == IOBUF_IOCTL_NO_CACHE)
    {
      if (DBG_IOBUF)
	log_debug ("iobuf-%d.%d: ioctl '%s' no_cache=%d\n",
		   a ? a->no : -1, a ? a->subno : -1, iobuf_desc (a),
		   intval);
      for (; a; a = a->chain)
	if (!a->chain && a->filter == file_filter)
	  {
	    file_filter_ctx_t *b = a->filter_ov;
	    b->no_cache = intval;
	    return 0;
	  }
#ifdef HAVE_W32_SYSTEM
	else if (!a->chain && a->filter == sock_filter)
	  {
	    sock_filter_ctx_t *b = a->filter_ov;
	    b->no_cache = intval;
	    return 0;
	  }
#endif
    }
  else if (cmd == IOBUF_IOCTL_FSYNC)
    {
      /* Do a fsync on the open fd and return any errors to the caller
         of iobuf_ioctl.  Note that we work on a file name here. */
      if (DBG_IOBUF)
        log_debug ("iobuf-*.*: ioctl '%s' fsync\n",
                   ptrval? (const char*)ptrval:"<null>");

	if (!a && !intval && ptrval)
	  {
	    return fd_cache_synchronize (ptrval);
	  }
      }


  return -1;
}


/****************
 * Register an i/o filter.
 */
int
iobuf_push_filter (iobuf_t a,
		   int (*f) (void *opaque, int control,
			     iobuf_t chain, byte * buf, size_t * len),
                   void *ov)
{
  return iobuf_push_filter2 (a, f, ov, 0);
}

int
iobuf_push_filter2 (iobuf_t a,
		    int (*f) (void *opaque, int control,
			      iobuf_t chain, byte * buf, size_t * len),
		    void *ov, int rel_ov)
{
  iobuf_t b;
  size_t dummy_len = 0;
  int rc = 0;

  if (a->use == IOBUF_OUTPUT && (rc = filter_flush (a)))
    return rc;

  if (a->subno >= MAX_NESTING_FILTER)
    {
      log_error ("i/o filter too deeply nested - corrupted data?\n");
      return GPG_ERR_BAD_DATA;
    }

  /* make a copy of the current stream, so that
   * A is the new stream and B the original one.
   * The contents of the buffers are transferred to the
   * new stream.
   */
  b = xmalloc (sizeof *b);
  memcpy (b, a, sizeof *b);
  /* fixme: it is stupid to keep a copy of the name at every level
   * but we need the name somewhere because the name known by file_filter
   * may have been released when we need the name of the file */
  b->real_fname = a->real_fname ? xstrdup (a->real_fname) : NULL;
  /* remove the filter stuff from the new stream */
  a->filter = NULL;
  a->filter_ov = NULL;
  a->filter_ov_owner = 0;
  a->filter_eof = 0;
  if (a->use == IOBUF_TEMP)
    /* make a write stream from a temp stream */
    a->use = IOBUF_OUTPUT;

  if (a->use == IOBUF_OUTPUT)
    {				/* allocate a fresh buffer for the
                                   original stream */
      b->d.buf = xmalloc (a->d.size);
      b->d.len = 0;
      b->d.start = 0;
    }
  else
    {				/* allocate a fresh buffer for the new
                                   stream */
      a->d.buf = xmalloc (a->d.size);
      a->d.len = 0;
      a->d.start = 0;
    }
  /* disable nlimit for the new stream */
  a->ntotal = b->ntotal + b->nbytes;
  a->nlimit = a->nbytes = 0;
  a->nofast = 0;
  /* make a link from the new stream to the original stream */
  a->chain = b;

  /* setup the function on the new stream */
  a->filter = f;
  a->filter_ov = ov;
  a->filter_ov_owner = rel_ov;

  a->subno = b->subno + 1;

  if (DBG_IOBUF)
    {
      log_debug ("iobuf-%d.%d: push '%s'\n",
		 a->no, a->subno, iobuf_desc (a));
      print_chain (a);
    }

  /* now we can initialize the new function if we have one */
  if (a->filter && (rc = a->filter (a->filter_ov, IOBUFCTRL_INIT, a->chain,
				    NULL, &dummy_len)))
    log_error ("IOBUFCTRL_INIT failed: %s\n", gpg_strerror (rc));
  return rc;
}

/****************
 * Remove an i/o filter.
 */
static int
pop_filter (iobuf_t a, int (*f) (void *opaque, int control,
			       iobuf_t chain, byte * buf, size_t * len),
	    void *ov)
{
  iobuf_t b;
  size_t dummy_len = 0;
  int rc = 0;

  if (DBG_IOBUF)
    log_debug ("iobuf-%d.%d: pop '%s'\n",
	       a->no, a->subno, iobuf_desc (a));
  if (!a->filter)
    {				/* this is simple */
      b = a->chain;
      assert (b);
      xfree (a->d.buf);
      xfree (a->real_fname);
      memcpy (a, b, sizeof *a);
      xfree (b);
      return 0;
    }
  for (b = a; b; b = b->chain)
    if (b->filter == f && (!ov || b->filter_ov == ov))
      break;
  if (!b)
    log_bug ("pop_filter(): filter function not found\n");

  /* flush this stream if it is an output stream */
  if (a->use == IOBUF_OUTPUT && (rc = filter_flush (b)))
    {
      log_error ("filter_flush failed in pop_filter: %s\n", gpg_strerror (rc));
      return rc;
    }
  /* and tell the filter to free it self */
  if (b->filter && (rc = b->filter (b->filter_ov, IOBUFCTRL_FREE, b->chain,
				    NULL, &dummy_len)))
    {
      log_error ("IOBUFCTRL_FREE failed: %s\n", gpg_strerror (rc));
      return rc;
    }
  if (b->filter_ov && b->filter_ov_owner)
    {
      xfree (b->filter_ov);
      b->filter_ov = NULL;
    }


  /* and see how to remove it */
  if (a == b && !b->chain)
    log_bug ("can't remove the last filter from the chain\n");
  else if (a == b)
    {				/* remove the first iobuf from the chain */
      /* everything from b is copied to a. This is save because
       * a flush has been done on the to be removed entry
       */
      b = a->chain;
      xfree (a->d.buf);
      xfree (a->real_fname);
      memcpy (a, b, sizeof *a);
      xfree (b);
      if (DBG_IOBUF)
	log_debug ("iobuf-%d.%d: popped filter\n", a->no, a->subno);
    }
  else if (!b->chain)
    {				/* remove the last iobuf from the chain */
      log_bug ("Ohh jeee, trying to remove a head filter\n");
    }
  else
    {				/* remove an intermediate iobuf from the chain */
      log_bug ("Ohh jeee, trying to remove an intermediate filter\n");
    }

  return rc;
}


/****************
 * read underflow: read more bytes into the buffer and return
 * the first byte or -1 on EOF.
 */
static int
underflow (iobuf_t a, int clear_pending_eof)
{
  size_t len;
  int rc;

  if (DBG_IOBUF)
    log_debug ("iobuf-%d.%d: underflow: buffer size: %d; still buffered: %d => space for %d bytes\n",
	       a->no, a->subno,
	       (int) a->d.size, (int) (a->d.len - a->d.start),
	       (int) (a->d.size - (a->d.len - a->d.start)));

  assert (a->use == IOBUF_INPUT);

  /* If there is still some buffered data, then move it to the start
     of the buffer and try to fill the end of the buffer.  (This is
     useful if we are called from iobuf_peek().)  */
  assert (a->d.start <= a->d.len);
  a->d.len -= a->d.start;
  memmove (a->d.buf, &a->d.buf[a->d.start], a->d.len);
  a->d.start = 0;

  if (a->d.len == 0 && a->filter_eof)
    /* The last time we tried to read from this filter, we got an EOF.
       We couldn't return the EOF, because there was buffered data.
       Since there is no longer any buffered data, return the
       error.  */
    {
      if (DBG_IOBUF)
	log_debug ("iobuf-%d.%d: underflow: eof (pending eof)\n",
		   a->no, a->subno);
      if (! clear_pending_eof)
	return -1;

      if (a->chain)
	/* A filter follows this one.  Free this filter.  */
	{
	  iobuf_t b = a->chain;
	  if (DBG_IOBUF)
	    log_debug ("iobuf-%d.%d: filter popped (pending EOF returned)\n",
		       a->no, a->subno);
	  xfree (a->d.buf);
	  xfree (a->real_fname);
	  memcpy (a, b, sizeof *a);
	  xfree (b);
	  print_chain (a);
	}
      else
	a->filter_eof = 0;	/* for the top level filter */
      return -1;		/* return one(!) EOF */
    }

  if (a->d.len == 0 && a->error)
    /* The last time we tried to read from this filter, we got an
       error.  We couldn't return the error, because there was
       buffered data.  Since there is no longer any buffered data,
       return the error.  */
    {
      if (DBG_IOBUF)
	log_debug ("iobuf-%d.%d: pending error (%s) returned\n",
		   a->no, a->subno, gpg_strerror (a->error));
      return -1;
    }

  if (a->filter && ! a->filter_eof && ! a->error)
    /* We have a filter function and the last time we tried to read we
       didn't get an EOF or an error.  Try to fill the buffer.  */
    {
      /* Be careful to account for any buffered data.  */
      len = a->d.size - a->d.len;
      if (DBG_IOBUF)
	log_debug ("iobuf-%d.%d: underflow: A->FILTER (%lu bytes)\n",
		   a->no, a->subno, (ulong) len);
      if (len == 0)
	/* There is no space for more data.  Don't bother calling
	   A->FILTER.  */
	rc = 0;
      else
	rc = a->filter (a->filter_ov, IOBUFCTRL_UNDERFLOW, a->chain,
			&a->d.buf[a->d.len], &len);
      a->d.len += len;

      if (DBG_IOBUF)
	log_debug ("iobuf-%d.%d: A->FILTER() returned rc=%d (%s), read %lu bytes\n",
		   a->no, a->subno,
		   rc, rc == 0 ? "ok" : rc == -1 ? "EOF" : gpg_strerror (rc),
		   (ulong) len);
/*  	    if( a->no == 1 ) */
/*                   log_hexdump ("     data:", a->d.buf, len); */

      if (rc == -1)
	/* EOF.  */
	{
	  size_t dummy_len = 0;

	  /* Tell the filter to free itself */
	  if ((rc = a->filter (a->filter_ov, IOBUFCTRL_FREE, a->chain,
			       NULL, &dummy_len)))
	    log_error ("IOBUFCTRL_FREE failed: %s\n", gpg_strerror (rc));

	  /* Free everything except for the internal buffer.  */
	  if (a->filter_ov && a->filter_ov_owner)
	    xfree (a->filter_ov);
	  a->filter_ov = NULL;
	  a->filter = NULL;
	  a->filter_eof = 1;

	  if (clear_pending_eof && a->d.len == 0 && a->chain)
	    /* We don't need to keep this filter around at all:

	         - we got an EOF
		 - we have no buffered data
		 - a filter follows this one.

	      Unlink this filter.  */
	    {
	      iobuf_t b = a->chain;
	      if (DBG_IOBUF)
		log_debug ("iobuf-%d.%d: pop in underflow (nothing buffered, got EOF)\n",
			   a->no, a->subno);
	      xfree (a->d.buf);
	      xfree (a->real_fname);
	      memcpy (a, b, sizeof *a);
	      xfree (b);

	      print_chain (a);

	      return -1;
	    }
	  else if (a->d.len == 0)
	    /* We can't unlink this filter (it is the only one in the
	       pipeline), but we can immediately return EOF.  */
	    return -1;
	}
      else if (rc)
	/* Record the error.  */
	{
	  a->error = rc;

	  if (a->d.len == 0)
	    /* There is no buffered data.  Immediately return EOF.  */
	    return -1;
	}
    }

  assert (a->d.start <= a->d.len);
  if (a->d.start < a->d.len)
    return a->d.buf[a->d.start++];

  /* EOF.  */
  return -1;
}


static int
filter_flush (iobuf_t a)
{
  size_t len;
  int rc;

  if (a->use == IOBUF_TEMP)
    {				/* increase the temp buffer */
      size_t newsize = a->d.size + IOBUF_BUFFER_SIZE;

      if (DBG_IOBUF)
	log_debug ("increasing temp iobuf from %lu to %lu\n",
		   (ulong) a->d.size, (ulong) newsize);

      a->d.buf = xrealloc (a->d.buf, newsize);
      a->d.size = newsize;
      return 0;
    }
  else if (a->use != IOBUF_OUTPUT)
    log_bug ("flush on non-output iobuf\n");
  else if (!a->filter)
    log_bug ("filter_flush: no filter\n");
  len = a->d.len;
  rc = a->filter (a->filter_ov, IOBUFCTRL_FLUSH, a->chain, a->d.buf, &len);
  if (!rc && len != a->d.len)
    {
      log_info ("filter_flush did not write all!\n");
      rc = GPG_ERR_INTERNAL;
    }
  else if (rc)
    a->error = rc;
  a->d.len = 0;

  return rc;
}


/****************
 * Read a byte from the iobuf; returns -1 on EOF
 */
int
iobuf_readbyte (iobuf_t a)
{
  int c;

  if (a->nlimit && a->nbytes >= a->nlimit)
    return -1;			/* forced EOF */

  if (a->d.start < a->d.len)
    {
      c = a->d.buf[a->d.start++];
    }
  else if ((c = underflow (a, 1)) == -1)
    return -1;			/* EOF */

  a->nbytes++;
  return c;
}


int
iobuf_read (iobuf_t a, void *buffer, unsigned int buflen)
{
  unsigned char *buf = (unsigned char *)buffer;
  int c, n;

  if (a->nlimit)
    {
      /* Handle special cases. */
      for (n = 0; n < buflen; n++)
	{
	  if ((c = iobuf_readbyte (a)) == -1)
	    {
	      if (!n)
		return -1;	/* eof */
	      break;
	    }
	  else if (buf)
	    *buf = c;
	  if (buf)
	    buf++;
	}
      return n;
    }

  n = 0;
  do
    {
      if (n < buflen && a->d.start < a->d.len)
	{
	  unsigned size = a->d.len - a->d.start;
	  if (size > buflen - n)
	    size = buflen - n;
	  if (buf)
	    memcpy (buf, a->d.buf + a->d.start, size);
	  n += size;
	  a->d.start += size;
	  if (buf)
	    buf += size;
	}
      if (n < buflen)
	{
	  if ((c = underflow (a, 1)) == -1)
	    {
	      a->nbytes += n;
	      return n ? n : -1 /*EOF*/;
	    }
	  if (buf)
	    *buf++ = c;
	  n++;
	}
    }
  while (n < buflen);
  a->nbytes += n;
  return n;
}



int
iobuf_peek (iobuf_t a, byte * buf, unsigned buflen)
{
  int n = 0;

  assert (buflen > 0);
  assert (a->use == IOBUF_INPUT);

  if (buflen > a->d.size)
    /* We can't peek more than we can buffer.  */
    buflen = a->d.size;

  /* Try to fill the internal buffer with enough data to satisfy the
     request.  */
  while (buflen > a->d.len - a->d.start)
    {
      if (underflow (a, 0) == -1)
	/* EOF.  We can't read any more.  */
	break;

      /* Underflow consumes the first character (it's the return
	 value).  unget() it by resetting the "file position".  */
      assert (a->d.start == 1);
      a->d.start = 0;
    }

  n = a->d.len - a->d.start;
  if (n > buflen)
    n = buflen;

  if (n == 0)
    /* EOF.  */
    return -1;

  memcpy (buf, &a->d.buf[a->d.start], n);

  return n;
}




int
iobuf_writebyte (iobuf_t a, unsigned int c)
{
  int rc;

  if (a->d.len == a->d.size)
    if ((rc=filter_flush (a)))
      return rc;

  assert (a->d.len < a->d.size);
  a->d.buf[a->d.len++] = c;
  return 0;
}


int
iobuf_write (iobuf_t a, const void *buffer, unsigned int buflen)
{
  const unsigned char *buf = (const unsigned char *)buffer;
  int rc;

  do
    {
      if (buflen && a->d.len < a->d.size)
	{
	  unsigned size = a->d.size - a->d.len;
	  if (size > buflen)
	    size = buflen;
	  memcpy (a->d.buf + a->d.len, buf, size);
	  buflen -= size;
	  buf += size;
	  a->d.len += size;
	}
      if (buflen)
	{
	  rc = filter_flush (a);
          if (rc)
	    return rc;
	}
    }
  while (buflen);
  return 0;
}


int
iobuf_writestr (iobuf_t a, const char *buf)
{
  int rc;

  for (; *buf; buf++)
    if ((rc=iobuf_writebyte (a, *buf)))
      return rc;
  return 0;
}



/****************
 * copy the contents of TEMP to A.
 */
int
iobuf_write_temp (iobuf_t a, iobuf_t temp)
{
  while (temp->chain)
    pop_filter (temp, temp->filter, NULL);
  return iobuf_write (a, temp->d.buf, temp->d.len);
}

/****************
 * copy the contents of the temp io stream to BUFFER.
 */
size_t
iobuf_temp_to_buffer (iobuf_t a, byte * buffer, size_t buflen)
{
  size_t n = a->d.len;

  if (n > buflen)
    n = buflen;
  memcpy (buffer, a->d.buf, n);
  return n;
}


/****************
 * Call this function to terminate processing of the temp stream
 * without closing it.	This removes all filters from the stream
 * makes sure that iobuf_get_temp_{buffer,length}() returns correct
 * values.
 */
void
iobuf_flush_temp (iobuf_t temp)
{
  while (temp->chain)
    pop_filter (temp, temp->filter, NULL);
}


/****************
 * Set a limit on how many bytes may be read from the input stream A.
 * Setting the limit to 0 disables this feature.
 */
void
iobuf_set_limit (iobuf_t a, off_t nlimit)
{
  if (nlimit)
    a->nofast = 1;
  else
    a->nofast = 0;
  a->nlimit = nlimit;
  a->ntotal += a->nbytes;
  a->nbytes = 0;
}



/* Return the length of an open file A.  IF OVERFLOW is not NULL it
   will be set to true if the file is larger than what off_t can cope
   with.  The function return 0 on error or on overflow condition.  */
off_t
iobuf_get_filelength (iobuf_t a, int *overflow)
{
  struct stat st;

  if (overflow)
    *overflow = 0;

  /* Hmmm: file_filter may have already been removed */
  for ( ; a; a = a->chain )
    if ( !a->chain && a->filter == file_filter )
      {
        file_filter_ctx_t *b = a->filter_ov;
        gnupg_fd_t fp = b->fp;

#if defined(HAVE_W32_SYSTEM)
        ulong size;
        static int (* __stdcall get_file_size_ex) (void *handle,
                                                   LARGE_INTEGER *r_size);
        static int get_file_size_ex_initialized;

        if (!get_file_size_ex_initialized)
          {
            void *handle;

            handle = dlopen ("kernel32.dll", RTLD_LAZY);
            if (handle)
              {
                get_file_size_ex = dlsym (handle, "GetFileSizeEx");
                if (!get_file_size_ex)
                  dlclose (handle);
              }
            get_file_size_ex_initialized = 1;
          }

        if (get_file_size_ex)
          {
            /* This is a newer system with GetFileSizeEx; we use this
               then because it seem that GetFileSize won't return a
               proper error in case a file is larger than 4GB. */
            LARGE_INTEGER exsize;

            if (get_file_size_ex (fp, &exsize))
              {
                if (!exsize.u.HighPart)
                  return exsize.u.LowPart;
                if (overflow)
                  *overflow = 1;
                return 0;
              }
          }
        else
          {
            if ((size=GetFileSize (fp, NULL)) != 0xffffffff)
              return size;
          }
        log_error ("GetFileSize for handle %p failed: %s\n",
                   fp, w32_strerror (0));
#else
        if ( !fstat (FD2INT (fp), &st) )
          return st.st_size;
        log_error("fstat() failed: %s\n", strerror(errno) );
#endif
        break/*the for loop*/;
      }

    return 0;
}


/* Return the file descriptor of the underlying file or -1 if it is
   not available.  */
int
iobuf_get_fd (iobuf_t a)
{
  for ( ; a; a = a->chain )
    if (!a->chain && a->filter == file_filter)
      {
        file_filter_ctx_t *b = a->filter_ov;
        gnupg_fd_t fp = b->fp;

        return FD2INT (fp);
      }

  return -1;
}



/****************
 * Tell the file position, where the next read will take place
 */
off_t
iobuf_tell (iobuf_t a)
{
  return a->ntotal + a->nbytes;
}


#if !defined(HAVE_FSEEKO) && !defined(fseeko)

#ifdef HAVE_LIMITS_H
# include <limits.h>
#endif
#ifndef LONG_MAX
# define LONG_MAX ((long) ((unsigned long) -1 >> 1))
#endif
#ifndef LONG_MIN
# define LONG_MIN (-1 - LONG_MAX)
#endif

/****************
 * A substitute for fseeko, for hosts that don't have it.
 */
static int
fseeko (FILE * stream, off_t newpos, int whence)
{
  while (newpos != (long) newpos)
    {
      long pos = newpos < 0 ? LONG_MIN : LONG_MAX;
      if (fseek (stream, pos, whence) != 0)
	return -1;
      newpos -= pos;
      whence = SEEK_CUR;
    }
  return fseek (stream, (long) newpos, whence);
}
#endif

/****************
 * This is a very limited implementation. It simply discards all internal
 * buffering and removes all filters but the first one.
 */
int
iobuf_seek (iobuf_t a, off_t newpos)
{
  file_filter_ctx_t *b = NULL;

  if (a->use != IOBUF_TEMP)
    {
      for (; a; a = a->chain)
	{
	  if (!a->chain && a->filter == file_filter)
	    {
	      b = a->filter_ov;
	      break;
	    }
	}
      if (!a)
	return -1;
#ifdef HAVE_W32_SYSTEM
      if (SetFilePointer (b->fp, newpos, NULL, FILE_BEGIN) == 0xffffffff)
	{
	  log_error ("SetFilePointer failed on handle %p: ec=%d\n",
		     b->fp, (int) GetLastError ());
	  return -1;
	}
#else
      if (lseek (b->fp, newpos, SEEK_SET) == (off_t) - 1)
	{
	  log_error ("can't lseek: %s\n", strerror (errno));
	  return -1;
	}
#endif
    }
  /* Discard the buffer unless it is a temp stream.  */
  if (a->use != IOBUF_TEMP)
    a->d.len = 0;
  a->d.start = 0;
  a->nbytes = 0;
  a->nlimit = 0;
  a->nofast = 0;
  a->ntotal = newpos;
  a->error = 0;
  /* remove filters, but the last */
  if (a->chain)
    log_debug ("pop_filter called in iobuf_seek - please report\n");
  while (a->chain)
    pop_filter (a, a->filter, NULL);

  return 0;
}






/****************
 * Retrieve the real filename.  This is the filename actually used on
 * disk and not a made up one.  Returns NULL if no real filename is
 * available.
 */
const char *
iobuf_get_real_fname (iobuf_t a)
{
  if (a->real_fname)
    return a->real_fname;

  /* the old solution */
  for (; a; a = a->chain)
    if (!a->chain && a->filter == file_filter)
      {
	file_filter_ctx_t *b = a->filter_ov;
	return b->print_only_name ? NULL : b->fname;
      }

  return NULL;
}


/****************
 * Retrieve the filename.  This name should only be used in diagnostics.
 */
const char *
iobuf_get_fname (iobuf_t a)
{
  for (; a; a = a->chain)
    if (!a->chain && a->filter == file_filter)
      {
	file_filter_ctx_t *b = a->filter_ov;
	return b->fname;
      }
  return NULL;
}

/* Same as iobuf_get_fname but never returns NULL.  */
const char *
iobuf_get_fname_nonnull (iobuf_t a)
{
  const char *fname;

  fname = iobuf_get_fname (a);
  return fname? fname : "[?]";
}


/****************
 * enable partial block mode as described in the OpenPGP draft.
 * LEN is the first length byte on read, but ignored on writes.
 */
void
iobuf_set_partial_block_mode (iobuf_t a, size_t len)
{
  block_filter_ctx_t *ctx = xcalloc (1, sizeof *ctx);

  assert (a->use == IOBUF_INPUT || a->use == IOBUF_OUTPUT);
  ctx->use = a->use;
  if (!len)
    {
      if (a->use == IOBUF_INPUT)
	log_debug ("pop_filter called in set_partial_block_mode"
		   " - please report\n");
      pop_filter (a, block_filter, NULL);
    }
  else
    {
      ctx->partial = 1;
      ctx->size = 0;
      ctx->first_c = len;
      iobuf_push_filter (a, block_filter, ctx);
    }
}



/****************
 * Same as fgets() but if the buffer is too short a larger one will
 * be allocated up to some limit *max_length.
 * A line is considered a byte stream ending in a LF.
 * Returns the length of the line. EOF is indicated by a line of
 * length zero. The last LF may be missing due to an EOF.
 * is max_length is zero on return, the line has been truncated.
 *
 * Note: The buffer is allocated with enough space to append a CR,LF,EOL
 */
unsigned int
iobuf_read_line (iobuf_t a, byte ** addr_of_buffer,
		 unsigned *length_of_buffer, unsigned *max_length)
{
  int c;
  char *buffer = (char *)*addr_of_buffer;
  unsigned length = *length_of_buffer;
  unsigned nbytes = 0;
  unsigned maxlen = *max_length;
  char *p;

  /* The code assumes that we have space for at least a newline and a
     NUL character in the buffer.  This requires at least 2 bytes.  We
     don't complicate the code by handling the stupid corner case, but
     simply assert that it can't happen.  */
  assert (length >= 2 || maxlen >= 2);

  if (!buffer || length <= 1)
    /* must allocate a new buffer */
    {
      length = 256 <= maxlen ? 256 : maxlen;
      buffer = xrealloc (buffer, length);
      *addr_of_buffer = (unsigned char *)buffer;
      *length_of_buffer = length;
    }

  p = buffer;
  while ((c = iobuf_get (a)) != -1)
    {
      *p++ = c;
      nbytes++;
      if (c == '\n')
	break;

      if (nbytes == length - 1)
	/* We don't have enough space to add a \n and a \0.  Increase
	   the buffer size.  */
	{
	  if (length == maxlen)
	    /* We reached the buffer's size limit!  */
	    {
	      /* Skip the rest of the line.  */
	      while (c != '\n' && (c = iobuf_get (a)) != -1)
		;

	      /* p is pointing at the last byte in the buffer.  We
		 always terminate the line with "\n\0" so overwrite
		 the previous byte with a \n.  */
	      assert (p > buffer);
	      p[-1] = '\n';

	      /* Indicate truncation.  */
	      *max_length = 0;
	      break;
	    }

	  length += length < 1024 ? 256 : 1024;
	  if (length > maxlen)
	    length = maxlen;

	  buffer = xrealloc (buffer, length);
	  *addr_of_buffer = (unsigned char *)buffer;
	  *length_of_buffer = length;
	  p = buffer + nbytes;
	}
    }
  /* Add the terminating NUL.  */
  *p = 0;

  /* Return the number of characters written to the buffer including
     the newline, but not including the terminating NUL.  */
  return nbytes;
}

static int
translate_file_handle (int fd, int for_write)
{
#if defined(HAVE_W32CE_SYSTEM)
  /* This is called only with one of the special filenames.  Under
     W32CE the FD here is not a file descriptor but a rendezvous id,
     thus we need to finish the pipe first.  */
  fd = _assuan_w32ce_finish_pipe (fd, for_write);
#elif defined(HAVE_W32_SYSTEM)
  {
    int x;

    (void)for_write;

    if (fd == 0)
      x = (int) GetStdHandle (STD_INPUT_HANDLE);
    else if (fd == 1)
      x = (int) GetStdHandle (STD_OUTPUT_HANDLE);
    else if (fd == 2)
      x = (int) GetStdHandle (STD_ERROR_HANDLE);
    else
      x = fd;

    if (x == -1)
      log_debug ("GetStdHandle(%d) failed: ec=%d\n",
		 fd, (int) GetLastError ());

    fd = x;
  }
#else
  (void)for_write;
#endif
  return fd;
}


void
iobuf_skip_rest (iobuf_t a, unsigned long n, int partial)
{
  if ( partial )
    {
      for (;;)
        {
          if (a->nofast || a->d.start >= a->d.len)
            {
              if (iobuf_readbyte (a) == -1)
                {
                  break;
                }
	    }
          else
            {
              unsigned long count = a->d.len - a->d.start;
              a->nbytes += count;
              a->d.start = a->d.len;
	    }
	}
    }
  else
    {
      unsigned long remaining = n;
      while (remaining > 0)
        {
          if (a->nofast || a->d.start >= a->d.len)
            {
              if (iobuf_readbyte (a) == -1)
                {
                  break;
		}
              --remaining;
	    }
          else
            {
              unsigned long count = a->d.len - a->d.start;
              if (count > remaining)
                {
                  count = remaining;
		}
              a->nbytes += count;
              a->d.start += count;
              remaining -= count;
	    }
	}
    }
}