/* GNU Mailutils -- a suite of utilities for electronic mail
   Copyright (C) 1999-2020 Free Software Foundation, Inc.

   This library is free software; you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License as published by
   the Free Software Foundation; either version 3, or (at your option)
   any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with GNU Mailutils.  If not, see <http://www.gnu.org/licenses/>. */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#include <mailutils/types.h>
#include <mailutils/alloc.h>
#include <mailutils/errno.h>

#include <mailutils/nls.h>
#include <mailutils/stream.h>
#include <mailutils/sys/stream.h>
#include <mailutils/sys/xscript-stream.h>
#include <mailutils/cctype.h>
#include <mailutils/cstr.h>

/* A "transcript stream" transparently writes data to and reads data from
   an underlying transport stream, writing each lineful of data to a "log
   stream". Writes to log stream are prefixed with a string indicating
   direction of the data (read/write). Default prefixes are those used in
   RFCs -- "S: ", for data written ("Server"), and "C: ", for data read
   ("Client").

   The stream can operate in three distinct modes, called "transcript
   levels":

   MU_XSCRIPT_NORMAL
     The default level. Everything is logged indiscriminately. Programmers
     should excercise care when using this mode, as it can reveal security
     sensitive data (such as login credentials, etc.) as well as private
     user's information (mail content).

   MU_XSCRIPT_SECURE
     The stream attempts to locate passwords and replaces them with three
     asteriscs when sending to the log stream. This mode should be used before
     the session is authenticated. Currently the following two constructs are
     recognized:

       PASS <STRING>
       <WORD> LOGIN <STRING1> <STRING2>

     Here, <WORD> stands for an unquoted word, and <STRING> stands for a
     <WORD> or any sequence of characters enclosed in double-quotes. When
     the first construct is encountered, <STRING> is replaced with "***" in
     transcript. For the second construct, <STRING2> is replaced.

     These two cover two most used authentication methods used in POP and
     IMAP protocols.

   MU_XSCRIPT_PAYLOAD
     This mode is suitable when large amounts of user data are passed through
     the stream, e.g. when sending literals in IMAP or sending replies to
     RETR or TOP requests in POP protocol. In this mode, the stream logs
     the single string "(data...)" upon receiving first block of data and
     stops further logging.

     This mode can be enabled for a certain amount of data that is about
     to be sent, if such amount is known beforehand. In that case, the stream
     will automatically revert to MU_XSCRIPT_NORMAL mode after that much
     data has been processed. This is used when sending or receiving IMAP
     literals.

   Either direction (hereinafter called "channel") is implemented as an
   independent state machine, so that the above modes can be configured
   independently for each channel.

   The stream is configured using the MU_IOCTL_XSCRIPTSTREAM ioctl family.
   The following opcodes are implemented:

   MU_IOCTL_XSCRIPTSTREAM_LEVEL
     Set new transcript level(s) for both channels.

     Argument: int *X

     X is the desired transcript level. It will be set on both channels.
     If different transcript levels are desired, they can be packed into
     integer using the MU_XSCRIPT_LEVEL_PACK macro, e.g.

       int n = MU_XSCRIPT_LEVEL_PACK(MU_XSCRIPT_SECURE, MU_XSCRIPT_NORMAL);
       mu_stream_ioctl (str,
			MU_IOCTL_XSCRIPTSTREAM,
			MU_IOCTL_XSCRIPTSTREAM_LEVEL,
			&n);

     Upon successful return, previous transcript levels are stored in X.
     This allows the programmer to restore prior settings using the
     same ioctl.

     The returned value is a single transcript level, if levels are the same
     in both channels, or packed levels otherwise. This ensures compatibility
     with the prior versions of libmailutils.

     Whether it is packed or not, the level for each particular channel can be
     retrieved from X using the MU_XSCRIPT_LEVEL_UNPACK macro.

     It is advised to use MU_IOCTL_XSCRIPTSTREAM_LEVEL only when setting
     same level for both channels. Otherwise, please use
     MU_IOCTL_XSCRIPTSTREAM_CHANNEL.

   MU_IOCTL_XSCRIPTSTREAM_CHANNEL
     Reconfigure single channel.

     Argument: struct mu_xscript_channel *C

     Upon successful return, prior channel configuration is stored in the
     memory location pointed to by C.

     If C->level is MU_XSCRIPT_PAYLOAD, C->length can be set to a non-zero
     value, indicated the amount of user data about to be passed through
     the channel. The channel state will return to MU_XSCRIPT_NORMAL after
     that much data are processed.

     For any other value of C->level, C->length must be 0.
*/

enum
  {
    CHAN_READ = MU_TRANSPORT_INPUT,
    CHAN_WRITE = MU_TRANSPORT_OUTPUT
  };

enum
  {
    XST_NORMAL = MU_XSCRIPT_NORMAL,
    XST_SECURE = MU_XSCRIPT_SECURE,
    XST_PAYLOAD = MU_XSCRIPT_PAYLOAD,
    XST_SKIPLEN,
    XST_DISABLED
  };

static int
word_match (const char *buf, size_t len, int n, const char *word, size_t *pos)
{
  size_t i = 0;
  size_t wl = strlen (word);

  for (;; n--)
    {
      /* Skip whitespace separator */
      for (; i < len && mu_isspace (buf[i]); i++)
	;

      if (n == 0)
	break;

      /* Skip the argument */
      if (buf[i] == '"')
	{
	  for (i++; i < len && buf[i] != '"'; i++)
	    if (buf[i] == '\'')
	      i++;
	}
      else
	{
	  for (; i < len && !mu_isspace (buf[i]); i++)
	    ;
	}
    }

  if (i + wl <= len &&
      mu_c_strncasecmp (buf + i, word, wl) == 0 &&
      mu_isblank (buf[i + wl]))
    {
      *pos = i + wl;
      return 1;
    }

  return 0;
}

static void
print_transcript (struct _mu_xscript_stream *str, int dir,
		  const char *buf, size_t size)
{
  while (size)
    {
      const char *p;
      size_t len;

      switch (str->channel[dir].state)
	{
	case XST_NORMAL:
	case XST_SECURE:
	  mu_stream_write (str->logstr,
			   str->prefix[dir],
			   strlen (str->prefix[dir]),
			   NULL);
	  break;

	case XST_PAYLOAD:
	  mu_stream_write (str->logstr,
			   str->prefix[dir],
			   strlen (str->prefix[dir]),
			   NULL);
	  mu_stream_printf (str->logstr, "(data...)\n");
	  if (str->channel[dir].length > 0)
	    str->channel[dir].state = XST_SKIPLEN;
	  else
	    str->channel[dir].state = XST_DISABLED;
	  continue;

	case XST_SKIPLEN:
	  len = (size <= str->channel[dir].length)
		  ? size : str->channel[dir].length;
	  str->channel[dir].length -= len;
	  size -= len;
	  buf += len;
	  if (str->channel[dir].length == 0)
	    str->channel[dir].state = XST_NORMAL;
	  continue;

	case XST_DISABLED:
	  return;
	}

      p = memchr (buf, '\n', size);
      if (p)
	{
	  len = p - buf;
	  if (p > buf && p[-1] == '\r')
	    len--;

	  if (str->channel[dir].state == MU_XSCRIPT_SECURE)
	    {
	      size_t i;

	      if (word_match (buf, len, 0, "PASS", &i))
		mu_stream_printf (str->logstr, "PASS ***");
	      else if (word_match (buf, len, 1, "LOGIN", &i))
		{
		  /* Skip the whitespace separator */
		  for (; i < len && mu_isspace (buf[i]); i++)
		    ;
		  /* Skip the first argument (presumably the user name) */
		  if (buf[i] == '"')
		    {
		      for (i++; i < len && buf[i] != '"'; i++)
			if (buf[i] == '\\')
			  i++;
		      if (i < len && buf[i] == '"')
			i++;
		    }
		  else
		    {
		      for (; i < len && !mu_isspace (buf[i]); i++)
			;
		    }
		  mu_stream_write (str->logstr, buf, i, NULL);
		  mu_stream_write (str->logstr, " \"***\"", 6, NULL);
		}
	      else
		mu_stream_write (str->logstr, buf, len, NULL);
	    }
	  else
	    mu_stream_write (str->logstr, buf, len, NULL);
	  mu_stream_write (str->logstr, "\n", 1, NULL);

	  len = p - buf + 1;
	  buf = p + 1;
	  size -= len;
	}
      else
	{
	  mu_stream_write (str->logstr, buf, size, NULL);
	  break;
	}
    }
}

static void
_xscript_event_cb (mu_stream_t str, int ev, unsigned long size, void *ptr)
{
  struct _mu_xscript_stream *sp = (struct _mu_xscript_stream *)str;

  switch (ev)
    {
    case _MU_STR_EVENT_FILLBUF:
      print_transcript (sp, CHAN_READ, ptr, size);
      break;

    case _MU_STR_EVENT_FLUSHBUF:
      print_transcript (sp, CHAN_WRITE, ptr, size);
    }
}

static int
_xscript_read (struct _mu_stream *str, char *buf, size_t bufsize,
	       size_t *pnread)
{
  struct _mu_xscript_stream *sp = (struct _mu_xscript_stream *)str;
  return mu_stream_read (sp->transport, buf, bufsize, pnread);
}

static int
_xscript_write (struct _mu_stream *str, const char *buf, size_t bufsize,
		  size_t *pnwrite)
{
  struct _mu_xscript_stream *sp = (struct _mu_xscript_stream *)str;
  return mu_stream_write (sp->transport, buf, bufsize, pnwrite);
}

static int
_xscript_flush (struct _mu_stream *str)
{
  struct _mu_xscript_stream *sp = (struct _mu_xscript_stream *)str;
  return mu_stream_flush (sp->transport);
}

static int
_xscript_open (struct _mu_stream *str)
{
  struct _mu_xscript_stream *sp = (struct _mu_xscript_stream *)str;
  return mu_stream_open (sp->transport);
}

static int
_xscript_close (struct _mu_stream *str)
{
  struct _mu_xscript_stream *sp = (struct _mu_xscript_stream *)str;
  return mu_stream_close (sp->transport);
}

static void
_xscript_done (struct _mu_stream *str)
{
  struct _mu_xscript_stream *sp = (struct _mu_xscript_stream *)str;
  free (sp->prefix[0]);
  free (sp->prefix[1]);
  mu_stream_unref (sp->transport);
  mu_stream_unref (sp->logstr);
}

static int
_xscript_seek (struct _mu_stream *str, mu_off_t off, mu_off_t *ppos)
{
  struct _mu_xscript_stream *sp = (struct _mu_xscript_stream *)str;
  return mu_stream_seek (sp->transport, off, MU_SEEK_SET, ppos);
}

static int
_xscript_size (struct _mu_stream *str, mu_off_t *psize)
{
  struct _mu_xscript_stream *sp = (struct _mu_xscript_stream *)str;
  return mu_stream_size (sp->transport, psize);
}

static inline int
state_to_level(int s)
{
  return s >= XST_PAYLOAD ? XST_PAYLOAD : s;
}

static int
_xscript_ctl (struct _mu_stream *str, int code, int opcode, void *arg)
{
  struct _mu_xscript_stream *sp = (struct _mu_xscript_stream *)str;
  int status = 0;

  switch (code)
    {
    case MU_IOCTL_TRANSPORT:
      if (!arg)
	return EINVAL;
      else
	{
	  mu_transport_t *ptrans = arg;
	  switch (opcode)
	    {
	    case MU_IOCTL_OP_GET:
	      ptrans[0] = (mu_transport_t) sp->transport;
	      ptrans[1] = (mu_transport_t) sp->logstr;
	      break;

	    case MU_IOCTL_OP_SET:
	      ptrans = arg;
	      if (ptrans[0])
		sp->transport = (mu_stream_t) ptrans[0];
	      if (ptrans[1])
		sp->logstr = (mu_stream_t) ptrans[1];
	      break;

	    default:
	      return EINVAL;
	    }
	}
      break;

    case MU_IOCTL_SUBSTREAM:
      if (sp->transport
	  && ((status = mu_stream_ioctl (sp->transport, code, opcode, arg)) == 0
	      || status != ENOSYS))
	return status;
      /* fall through */

    case MU_IOCTL_TOPSTREAM:
      if (!arg)
	return EINVAL;
      switch (opcode)
	{
	case MU_IOCTL_OP_GET:
	  if (!sp->transport)
	    status = ENOSYS;
	  else
	    status = mu_stream_ioctl (sp->transport, code, opcode, arg);
	  if (status == EINVAL || status == ENOSYS)
	    {
	      mu_stream_t *pstr = arg;

	      pstr[0] = sp->transport;
	      mu_stream_ref (pstr[0]);
	      pstr[1] = sp->transport;
	      mu_stream_ref (pstr[1]);
	      status = 0;
	    }
	  break;

	case MU_IOCTL_OP_SET:
	  if (!sp->transport)
	    status = ENOSYS;
	  else
	    status = mu_stream_ioctl (sp->transport, code, opcode, arg);
	  if (status == EINVAL || status == ENOSYS)
	    {
	      mu_stream_t *pstr = arg;
	      mu_stream_t tmp;

	      if (pstr[0] != pstr[1])
		{
		  status = mu_iostream_create (&tmp, pstr[0], pstr[1]);
		  if (status)
		    return status;
		}
	      else
		{
		  tmp = pstr[0];
		  mu_stream_ref (tmp);
		  mu_stream_ref (tmp);
		  status = 0;
		}

	      mu_stream_unref (sp->transport);
	      sp->transport = tmp;
	    }
	}
      break;

    case MU_IOCTL_TRANSPORT_BUFFER:
      if (!sp->transport)
	return EINVAL;
      return mu_stream_ioctl (sp->transport, code, opcode, arg);

    case  MU_IOCTL_XSCRIPTSTREAM:
      if (!arg)
	return EINVAL;
      switch (opcode)
	{
	case MU_IOCTL_XSCRIPTSTREAM_LEVEL:
	  {
	    int imode = state_to_level (sp->channel[CHAN_READ].state);
	    int omode = state_to_level (sp->channel[CHAN_WRITE].state);
	    int pack = *(int*)arg;

	    sp->channel[CHAN_READ].state =
	      MU_XSCRIPT_LEVEL_UNPACK (CHAN_READ, pack);
	    sp->channel[CHAN_READ].length = 0;

	    sp->channel[CHAN_WRITE].state =
	      MU_XSCRIPT_LEVEL_UNPACK (CHAN_WRITE, pack);
	    sp->channel[CHAN_WRITE].length = 0;

	    *(int*)arg = MU_XSCRIPT_LEVEL_PACK (imode, omode);
	  }
	  break;

	case MU_IOCTL_XSCRIPTSTREAM_CHANNEL:
	  {
	    struct mu_xscript_channel ret;
	    struct mu_xscript_channel *chp = arg;

	    if (chp->cd < 0 || chp->cd > 1
		|| chp->level > MU_XSCRIPT_PAYLOAD
		|| (chp->level != MU_XSCRIPT_PAYLOAD && chp->length > 0))
	      return EINVAL;

	    ret.cd = chp->cd;
	    ret.level = state_to_level (sp->channel[chp->cd].state);
	    ret.length = sp->channel[chp->cd].length;

	    sp->channel[chp->cd].state = chp->level;
	    if (chp->level == MU_XSCRIPT_PAYLOAD)
	      sp->channel[chp->cd].length = chp->length;
	    else
	      sp->channel[chp->cd].length = 0;

	    *chp = ret;
	  }
	  break;
	default:
	  return EINVAL;
	}
      break;

    default:
      return mu_stream_ioctl (sp->transport, code, opcode, arg);
    }
  return status;
}

static int
_xscript_wait (struct _mu_stream *str, int *pflags, struct timeval *tvp)
{
  struct _mu_xscript_stream *sp = (struct _mu_xscript_stream *)str;
  return mu_stream_wait (sp->transport, pflags, tvp);
}

static int
_xscript_truncate (struct _mu_stream *str, mu_off_t size)
{
  struct _mu_xscript_stream *sp = (struct _mu_xscript_stream *)str;
  return mu_stream_truncate (sp->transport, size);
}

static int
_xscript_shutdown (struct _mu_stream *str, int how)
{
  struct _mu_xscript_stream *sp = (struct _mu_xscript_stream *)str;
  return mu_stream_shutdown (sp->transport, how);
}

static const char *
_xscript_error_string (struct _mu_stream *str, int rc)
{
  struct _mu_xscript_stream *sp = (struct _mu_xscript_stream *)str;
  const char *p = mu_stream_strerror (sp->transport, rc);
  if (!p)
    p = mu_strerror (rc);
  return p;
}

const char *default_prefix[2] = {
    "C: ", "S: "
};

int
mu_xscript_stream_create (mu_stream_t *pref, mu_stream_t transport,
			  mu_stream_t logstr,
			  const char *prefix[])
{
  int flags;
  struct _mu_xscript_stream *sp;

  mu_stream_get_flags (transport, &flags);
  sp = (struct _mu_xscript_stream *) _mu_stream_create (sizeof (*sp),
							flags | _MU_STR_OPEN);
  if (!sp)
    return ENOMEM;

  sp->stream.read = _xscript_read;
  sp->stream.write = _xscript_write;
  sp->stream.flush = _xscript_flush;
  sp->stream.open = _xscript_open;
  sp->stream.close = _xscript_close;
  sp->stream.done = _xscript_done;
  sp->stream.seek = _xscript_seek;
  sp->stream.size = _xscript_size;
  sp->stream.ctl = _xscript_ctl;
  sp->stream.wait = _xscript_wait;
  sp->stream.truncate = _xscript_truncate;
  sp->stream.shutdown = _xscript_shutdown;
  sp->stream.error_string = _xscript_error_string;
  sp->stream.event_cb = _xscript_event_cb;
  sp->stream.event_mask = _MU_STR_EVMASK(_MU_STR_EVENT_FILLBUF) |
			  _MU_STR_EVMASK(_MU_STR_EVENT_FLUSHBUF);
  mu_stream_ref (transport);
  mu_stream_ref (logstr);

  sp->transport = transport;
  sp->logstr = logstr;

  if (prefix)
    {
      sp->prefix[0] = strdup (prefix[0] ? prefix[0] : default_prefix[0]);
      sp->prefix[1] = strdup (prefix[1] ? prefix[1] : default_prefix[1]);
    }
  else
    {
      sp->prefix[0] = strdup (default_prefix[0]);
      sp->prefix[1] = strdup (default_prefix[1]);
    }

  if (sp->prefix[0] == NULL || sp->prefix[1] == 0)
    {
      free (sp->prefix[0]);
      free (sp->prefix[1]);
      free (sp);
      return ENOMEM;
    }
  mu_stream_set_buffer ((mu_stream_t) sp, mu_buffer_line, 0);
  *pref = (mu_stream_t) sp;
  return 0;
}
