postprocessor.c

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/*
     This file is part of libmicrohttpd
     (C) 2007 Daniel Pittman and Christian Grothoff

     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 2.1 of the License, 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 this library; if not, write to the Free Software
     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include "internal.h"

#define XBUF_SIZE 1024

enum PP_State
{
  /* general states */
  PP_Error,
  PP_Done,
  PP_Init,

  /* url encoding-states */
  PP_ProcessValue,
  PP_ExpectNewLine,

  /* post encoding-states  */
  PP_ProcessEntryHeaders,
  PP_PerformCheckMultipart,
  PP_ProcessValueToBoundary,
  PP_PerformCleanup,

  /* nested post-encoding states */
  PP_Nested_Init,
  PP_Nested_PerformMarking,
  PP_Nested_ProcessEntryHeaders,
  PP_Nested_ProcessValueToBoundary,
  PP_Nested_PerformCleanup,

};

enum RN_State
{
  RN_Inactive = 0,

  RN_OptN = 1,

  RN_Full = 2,

  RN_Dash = 3,

  RN_Dash2 = 4,
};

enum NE_State
{
  NE_none = 0,
  NE_content_name = 1,
  NE_content_type = 2,
  NE_content_filename = 4,
  NE_content_transfer_encoding = 8,
};

struct MHD_PostProcessor
{

  struct MHD_Connection *connection;

  MHD_PostDataIterator ikvi;

  void *cls;

  const char *encoding;

  const char *boundary;

  char *nested_boundary;

  char *content_name;

  char *content_type;

  char *content_filename;

  char *content_transfer_encoding;

  char xbuf[8];

  unsigned int buffer_size;

  unsigned int buffer_pos;

  unsigned int xbuf_pos;

  unsigned int value_offset;

  size_t blen;

  size_t nlen;

  enum PP_State state;

  enum RN_State skip_rn;

  enum PP_State dash_state;

  enum NE_State have;

};


struct MHD_PostProcessor *
MHD_create_post_processor (struct MHD_Connection *connection,
                           unsigned int buffer_size,
                           MHD_PostDataIterator ikvi, void *cls)
{
  struct MHD_PostProcessor *ret;
  const char *encoding;
  const char *boundary;
  size_t blen;

  if ((buffer_size < 256) || (connection == NULL) || (ikvi == NULL))
    abort ();
  encoding = MHD_lookup_connection_value (connection,
                                          MHD_HEADER_KIND,
                                          MHD_HTTP_HEADER_CONTENT_TYPE);
  if (encoding == NULL)
    return NULL;
  boundary = NULL;
  if (0 != strcasecmp (MHD_HTTP_POST_ENCODING_FORM_URLENCODED, encoding))
    {
      if (0 !=
          strncasecmp (MHD_HTTP_POST_ENCODING_MULTIPART_FORMDATA, encoding,
                       strlen (MHD_HTTP_POST_ENCODING_MULTIPART_FORMDATA)))
        return NULL;
      boundary =
        &encoding[strlen (MHD_HTTP_POST_ENCODING_MULTIPART_FORMDATA)];
      /* Q: should this be "strcasestr"? */
      if (NULL != strstr (boundary, "boundary="))
        boundary = strstr (boundary, "boundary=") + strlen ("boundary=");
      else
        return NULL;            /* failed to determine boundary */
      blen = strlen (boundary);
      if ((blen == 0) || (blen * 2 + 2 > buffer_size))
        return NULL;            /* (will be) out of memory or invalid boundary */
    }
  else
    blen = 0;
  ret = malloc (sizeof (struct MHD_PostProcessor) + buffer_size + 1);
  if (ret == NULL)
    return NULL;
  memset (ret, 0, sizeof (struct MHD_PostProcessor) + buffer_size + 1);
  ret->connection = connection;
  ret->ikvi = ikvi;
  ret->cls = cls;
  ret->encoding = encoding;
  ret->buffer_size = buffer_size;
  ret->state = PP_Init;
  ret->blen = blen;
  ret->boundary = boundary;
  ret->skip_rn = RN_Inactive;
  return ret;
}

static int
post_process_urlencoded (struct MHD_PostProcessor *pp,
                         const char *post_data, unsigned int post_data_len)
{
  unsigned int equals;
  unsigned int amper;
  unsigned int poff;
  unsigned int xoff;
  unsigned int delta;
  int end_of_value_found;
  char *buf;
  char xbuf[XBUF_SIZE + 1];

  buf = (char *) &pp[1];
  poff = 0;
  while (poff < post_data_len)
    {
      switch (pp->state)
        {
        case PP_Error:
          return MHD_NO;
        case PP_Done:
          /* did not expect to receive more data */
          pp->state = PP_Error;
          return MHD_NO;
        case PP_Init:
          equals = 0;
          while ((equals + poff < post_data_len) &&
                 (post_data[equals + poff] != '='))
            equals++;
          if (equals + pp->buffer_pos > pp->buffer_size)
            {
              pp->state = PP_Error;     /* out of memory */
              return MHD_NO;
            }
          memcpy (&buf[pp->buffer_pos], &post_data[poff], equals);
          pp->buffer_pos += equals;
          if (equals + poff == post_data_len)
            return MHD_YES;     /* no '=' yet */
          buf[pp->buffer_pos] = '\0';   /* 0-terminate key */
          pp->buffer_pos = 0;   /* reset for next key */
          MHD_http_unescape (buf);
          poff += equals + 1;
          pp->state = PP_ProcessValue;
          pp->value_offset = 0;
          break;
        case PP_ProcessValue:
          /* obtain rest of value from previous iteration */
          memcpy (xbuf, pp->xbuf, pp->xbuf_pos);
          xoff = pp->xbuf_pos;
          pp->xbuf_pos = 0;

          /* find last position in input buffer that is part of the value */
          amper = 0;
          while ((amper + poff < post_data_len) &&
                 (amper < XBUF_SIZE) &&
                 (post_data[amper + poff] != '&') &&
                 (post_data[amper + poff] != '\n') &&
                 (post_data[amper + poff] != '\r'))
            amper++;
          end_of_value_found = ((amper + poff < post_data_len) &&
                                ((post_data[amper + poff] == '&') ||
                                 (post_data[amper + poff] == '\n') ||
                                 (post_data[amper + poff] == '\r')));
          /* compute delta, the maximum number of bytes that we will be able to
             process right now (either amper-limited of xbuf-size limited) */
          delta = amper;
          if (delta > XBUF_SIZE - xoff)
            delta = XBUF_SIZE - xoff;

          /* move input into processing buffer */
          memcpy (&xbuf[xoff], &post_data[poff], delta);
          xoff += delta;
          poff += delta;

          /* find if escape sequence is at the end of the processing buffer;
             if so, exclude those from processing (reduce delta to point at
             end of processed region) */
          delta = xoff;
          if ((delta > 0) && (xbuf[delta - 1] == '%'))
            delta--;
          else if ((delta > 1) && (xbuf[delta - 2] == '%'))
            delta -= 2;

          /* if we have an incomplete escape sequence, save it to
             pp->xbuf for later */
          if (delta < xoff)
            {
              memcpy (pp->xbuf, &xbuf[delta], xoff - delta);
              pp->xbuf_pos = xoff - delta;
              xoff = delta;
            }

          /* If we have nothing to do (delta == 0) and
             not just because the value is empty (are
             waiting for more data), go for next iteration */
          if ((xoff == 0) && (poff == post_data_len))
            continue;

          /* unescape */
          xbuf[xoff] = '\0';    /* 0-terminate in preparation */
          MHD_http_unescape (xbuf);

          /* finally: call application! */
          if (MHD_NO == pp->ikvi (pp->cls, MHD_POSTDATA_KIND, (const char *) &pp[1],    /* key */
                                  NULL, NULL, NULL, xbuf, pp->value_offset,
                                  xoff))
            {
              pp->state = PP_Error;
              return MHD_NO;
            }
          pp->value_offset += xoff;

          /* are we done with the value? */
          if (end_of_value_found)
            {
              /* we found the end of the value! */
              if ((post_data[poff] == '\n') || (post_data[poff] == '\r'))
                {
                  pp->state = PP_ExpectNewLine;
                }
              else
                {
                  poff++;       /* skip '&' */
                  pp->state = PP_Init;
                }
            }
          break;
        case PP_ExpectNewLine:
          if ((post_data[poff] == '\n') || (post_data[poff] == '\r'))
            {
              poff++;
              /* we are done, report error if we receive any more... */
              pp->state = PP_Done;
              return MHD_YES;
            }
          return MHD_NO;
        default:
          abort ();             /* should never happen! */
        }
    }
  return MHD_YES;
}

static int
try_match_header (const char *prefix, char *line, char **suffix)
{
  if (NULL != *suffix)
    return MHD_NO;
  while (*line != 0)
    {
      if (0 == strncasecmp (prefix, line, strlen (prefix)))
        {
          *suffix = strdup (&line[strlen (prefix)]);
          return MHD_YES;
        }
      ++line;
    }
  return MHD_NO;
}

static int
find_boundary (struct MHD_PostProcessor *pp,
               const char *boundary,
               size_t blen,
               unsigned int *ioffptr,
               enum PP_State next_state, enum PP_State next_dash_state)
{
  char *buf = (char *) &pp[1];

  if (pp->buffer_pos < 2 + blen)
    {
      if (pp->buffer_pos == pp->buffer_size)
        pp->state = PP_Error;   /* out of memory */
      return MHD_NO;            /* not enough data */
    }
  if ((0 != memcmp ("--", buf, 2)) || (0 != memcmp (&buf[2], boundary, blen)))
    {
      pp->state = PP_Error;
      return MHD_NO;            /* expected boundary */
    }
  /* remove boundary from buffer */
  (*ioffptr) += 2 + blen;
  /* next: start with headers */
  pp->skip_rn = RN_Dash;
  pp->state = next_state;
  pp->dash_state = next_dash_state;
  return MHD_YES;
}

static void
try_get_value (const char *buf, const char *key, char **destination)
{
  const char *spos;
  const char *bpos;
  const char *endv;
  size_t klen;
  size_t vlen;

  if (NULL != *destination)
    return;
  bpos = buf;
  klen = strlen (key);
  while (NULL != (spos = strstr (bpos, key)))
    {
      if ((spos[klen] != '=') || ((spos != buf) && (spos[-1] != ' ')))
        {
          /* no match */
          bpos = spos + 1;
          continue;
        }
      if (spos[klen + 1] != '"')
        return;                 /* not quoted */
      if (NULL == (endv = strstr (&spos[klen + 2], "\"")))
        return;                 /* no end-quote */
      vlen = endv - spos - klen - 1;
      *destination = malloc (vlen);
      if (NULL == *destination)
        return;                 /* out of memory */
      (*destination)[vlen - 1] = '\0';
      memcpy (*destination, &spos[klen + 2], vlen - 1);
      return;                   /* success */
    }
}

static int
process_multipart_headers (struct MHD_PostProcessor *pp,
                           unsigned int *ioffptr, enum PP_State next_state)
{
  char *buf = (char *) &pp[1];
  unsigned int newline;

  newline = 0;
  while ((newline < pp->buffer_pos) &&
         (buf[newline] != '\r') && (buf[newline] != '\n'))
    newline++;
  if (newline == pp->buffer_size)
    {
      pp->state = PP_Error;
      return MHD_NO;            /* out of memory */
    }
  if (newline == pp->buffer_pos)
    return MHD_NO;              /* will need more data */
  if (newline == 0)
    {
      /* empty line - end of headers */
      pp->skip_rn = RN_Full;
      pp->state = next_state;
      return MHD_YES;
    }
  /* got an actual header */
  if (buf[newline] == '\r')
    pp->skip_rn = RN_OptN;
  buf[newline] = '\0';
  if (0 == strncasecmp ("Content-disposition: ",
                        buf, strlen ("Content-disposition: ")))
    {
      try_get_value (&buf[strlen ("Content-disposition: ")],
                     "name", &pp->content_name);
      try_get_value (&buf[strlen ("Content-disposition: ")],
                     "filename", &pp->content_filename);
    }
  else
    {
      try_match_header ("Content-type: ", buf, &pp->content_type);
      try_match_header ("Content-Transfer-Encoding: ",
                        buf, &pp->content_transfer_encoding);
    }
  (*ioffptr) += newline + 1;
  return MHD_YES;
}

static int
process_value_to_boundary (struct MHD_PostProcessor *pp,
                           unsigned int *ioffptr,
                           const char *boundary,
                           size_t blen,
                           enum PP_State next_state,
                           enum PP_State next_dash_state)
{
  char *buf = (char *) &pp[1];
  unsigned int newline;

  /* all data in buf until the boundary
     (\r\n--+boundary) is part of the value */
  newline = 0;
  while (1)
    {
      while ((newline + 4 < pp->buffer_pos) &&
             (0 != memcmp ("\r\n--", &buf[newline], 4)))
        newline++;
      if (newline + pp->blen + 4 <= pp->buffer_pos)
        {
          /* can check boundary */
          if (0 != memcmp (&buf[newline + 4], boundary, pp->blen))
            {
              /* no boundary, "\r\n--" is part of content, skip */
              newline += 4;
              continue;
            }
          else
            {
              /* boundary found, process until newline then
                 skip boundary and go back to init */
              pp->skip_rn = RN_Dash;
              pp->state = next_state;
              pp->dash_state = next_dash_state;
              (*ioffptr) += pp->blen + 4;       /* skip boundary as well */
              break;
            }
        }
      else
        {
          /* cannot check for boundary, process content that
             we have and check again later; except, if we have
             no content, abort (out of memory) */
          if ((newline == 0) && (pp->buffer_pos == pp->buffer_size))
            {
              pp->state = PP_Error;
              return MHD_NO;
            }
          break;
        }
    }
  /* newline is either at beginning of boundary or
     at least at the last character that we are sure
     is not part of the boundary */
  if (MHD_NO == pp->ikvi (pp->cls,
                          MHD_POSTDATA_KIND,
                          pp->content_name,
                          pp->content_filename,
                          pp->content_type,
                          pp->content_transfer_encoding,
                          buf, pp->value_offset, newline))
    {
      pp->state = PP_Error;
      return MHD_NO;
    }
  pp->value_offset += newline;
  (*ioffptr) += newline;
  return MHD_YES;
}

static void
free_unmarked (struct MHD_PostProcessor *pp)
{
  if ((pp->content_name != NULL) && (0 == (pp->have & NE_content_name)))
    {
      free (pp->content_name);
      pp->content_name = NULL;
    }
  if ((pp->content_type != NULL) && (0 == (pp->have & NE_content_type)))
    {
      free (pp->content_type);
      pp->content_type = NULL;
    }
  if ((pp->content_filename != NULL) &&
      (0 == (pp->have & NE_content_filename)))
    {
      free (pp->content_filename);
      pp->content_filename = NULL;
    }
  if ((pp->content_transfer_encoding != NULL) &&
      (0 == (pp->have & NE_content_transfer_encoding)))
    {
      free (pp->content_transfer_encoding);
      pp->content_transfer_encoding = NULL;
    }
}

static int
post_process_multipart (struct MHD_PostProcessor *pp,
                        const char *post_data, unsigned int post_data_len)
{
  char *buf;
  unsigned int max;
  unsigned int ioff;
  unsigned int poff;
  int state_changed;

  buf = (char *) &pp[1];
  ioff = 0;
  poff = 0;
  state_changed = 1;
  while ((poff < post_data_len) ||
         ((pp->buffer_pos > 0) && (state_changed != 0)))
    {
      /* first, move as much input data
         as possible to our internal buffer */
      max = pp->buffer_size - pp->buffer_pos;
      if (max > post_data_len - poff)
        max = post_data_len - poff;
      memcpy (&buf[pp->buffer_pos], &post_data[poff], max);
      poff += max;
      pp->buffer_pos += max;
      if ((max == 0) && (state_changed == 0) && (poff < post_data_len))
        {
          pp->state = PP_Error;
          return MHD_NO;        /* out of memory */
        }
      state_changed = 0;

      /* first state machine for '\r'-'\n' and '--' handling */
      switch (pp->skip_rn)
        {
        case RN_Inactive:
          break;
        case RN_OptN:
          if (buf[0] == '\n')
            {
              ioff++;
              pp->skip_rn = RN_Inactive;
              goto AGAIN;
            }
        case RN_Dash:
          if (buf[0] == '-')
            {
              ioff++;
              pp->skip_rn = RN_Dash2;
              goto AGAIN;
            }
          pp->skip_rn = RN_Full;
          /* fall-through! */
        case RN_Full:
          if (buf[0] == '\r')
            {
              if ((pp->buffer_pos > 1) && (buf[1] == '\n'))
                {
                  pp->skip_rn = RN_Inactive;
                  ioff += 2;
                }
              else
                {
                  pp->skip_rn = RN_OptN;
                  ioff++;
                }
              goto AGAIN;
            }
          if (buf[0] == '\n')
            {
              ioff++;
              pp->skip_rn = RN_Inactive;
              goto AGAIN;
            }
          pp->skip_rn = RN_Inactive;
          pp->state = PP_Error;
          return MHD_NO;        /* no '\r\n' */
        case RN_Dash2:
          if (buf[0] == '-')
            {
              ioff++;
              pp->skip_rn = RN_Full;
              pp->state = pp->dash_state;
              goto AGAIN;
            }
          pp->state = PP_Error;
          break;
        }

      /* main state engine */
      switch (pp->state)
        {
        case PP_Error:
          return MHD_NO;
        case PP_Done:
          /* did not expect to receive more data */
          pp->state = PP_Error;
          return MHD_NO;
        case PP_Init:
          if (MHD_NO == find_boundary (pp,
                                       pp->boundary,
                                       pp->blen,
                                       &ioff,
                                       PP_ProcessEntryHeaders, PP_Done))
            {
              if (pp->state == PP_Error)
                return MHD_NO;
              goto END;
            }
          break;
        case PP_ProcessEntryHeaders:
          if (MHD_NO ==
              process_multipart_headers (pp, &ioff, PP_PerformCheckMultipart))
            {
              if (pp->state == PP_Error)
                return MHD_NO;
              else
                goto END;
            }
          state_changed = 1;
          break;
        case PP_PerformCheckMultipart:
          if ((pp->content_type != NULL) &&
              (0 == strncasecmp (pp->content_type,
                                 "multipart/mixed",
                                 strlen ("multipart/mixed"))))
            {
              pp->nested_boundary = strstr (pp->content_type, "boundary=");
              if (pp->nested_boundary == NULL)
                {
                  pp->state = PP_Error;
                  return MHD_NO;
                }
              pp->nested_boundary =
                strdup (&pp->nested_boundary[strlen ("boundary=")]);
              if (pp->nested_boundary == NULL)
                {
                  /* out of memory */
                  pp->state = PP_Error;
                  return MHD_NO;
                }
              /* free old content type, we will need that field
                 for the content type of the nested elements */
              free (pp->content_type);
              pp->content_type = NULL;
              pp->nlen = strlen (pp->nested_boundary);
              pp->state = PP_Nested_Init;
              state_changed = 1;
              break;
            }
          pp->state = PP_ProcessValueToBoundary;
          pp->value_offset = 0;
          state_changed = 1;
          break;
        case PP_ProcessValueToBoundary:
          if (MHD_NO == process_value_to_boundary (pp,
                                                   &ioff,
                                                   pp->boundary,
                                                   pp->blen,
                                                   PP_PerformCleanup,
                                                   PP_Done))
            {
              if (pp->state == PP_Error)
                return MHD_NO;
              break;
            }
          break;
        case PP_PerformCleanup:
          /* clean up state of one multipart form-data element! */
          pp->have = NE_none;
          free_unmarked (pp);
          if (pp->nested_boundary != NULL)
            {
              free (pp->nested_boundary);
              pp->nested_boundary = NULL;
            }
          pp->state = PP_ProcessEntryHeaders;
          state_changed = 1;
          break;
        case PP_Nested_Init:
          if (pp->nested_boundary == NULL)
            {
              pp->state = PP_Error;
              return MHD_NO;
            }
          if (MHD_NO == find_boundary (pp,
                                       pp->nested_boundary,
                                       pp->nlen,
                                       &ioff,
                                       PP_Nested_PerformMarking,
                                       PP_Init /* or PP_Error? */ ))
            {
              if (pp->state == PP_Error)
                return MHD_NO;
              goto END;
            }
          break;
        case PP_Nested_PerformMarking:
          /* remember what headers were given
             globally */
          pp->have = NE_none;
          if (pp->content_name != NULL)
            pp->have |= NE_content_name;
          if (pp->content_type != NULL)
            pp->have |= NE_content_type;
          if (pp->content_filename != NULL)
            pp->have |= NE_content_filename;
          if (pp->content_transfer_encoding != NULL)
            pp->have |= NE_content_transfer_encoding;
          pp->state = PP_Nested_ProcessEntryHeaders;
          state_changed = 1;
          break;
        case PP_Nested_ProcessEntryHeaders:
          pp->value_offset = 0;
          if (MHD_NO ==
              process_multipart_headers (pp, &ioff,
                                         PP_Nested_ProcessValueToBoundary))
            {
              if (pp->state == PP_Error)
                return MHD_NO;
              else
                goto END;
            }
          state_changed = 1;
          break;
        case PP_Nested_ProcessValueToBoundary:
          if (MHD_NO == process_value_to_boundary (pp,
                                                   &ioff,
                                                   pp->nested_boundary,
                                                   pp->nlen,
                                                   PP_Nested_PerformCleanup,
                                                   PP_Init))
            {
              if (pp->state == PP_Error)
                return MHD_NO;
              break;
            }
          break;
        case PP_Nested_PerformCleanup:
          free_unmarked (pp);
          pp->state = PP_Nested_ProcessEntryHeaders;
          state_changed = 1;
          break;
        default:
          abort ();             /* should never happen! */
        }
    AGAIN:
      if (ioff > 0)
        {
          memmove (buf, &buf[ioff], pp->buffer_pos - ioff);
          pp->buffer_pos -= ioff;
          ioff = 0;
          state_changed = 1;
        }
    }
END:
  if (ioff != 0)
    {
      memmove (buf, &buf[ioff], pp->buffer_pos - ioff);
      pp->buffer_pos -= ioff;
    }
  if (poff < post_data_len)
    {
      pp->state = PP_Error;
      return MHD_NO;            /* serious error */
    }
  return MHD_YES;
}

int
MHD_post_process (struct MHD_PostProcessor *pp,
                  const char *post_data, unsigned int post_data_len)
{
  if (post_data_len == 0)
    return MHD_YES;
  if (pp == NULL)
    return MHD_NO;
  if (0 == strcasecmp (MHD_HTTP_POST_ENCODING_FORM_URLENCODED, pp->encoding))
    return post_process_urlencoded (pp, post_data, post_data_len);
  if (0 ==
      strncasecmp (MHD_HTTP_POST_ENCODING_MULTIPART_FORMDATA, pp->encoding,
                   strlen (MHD_HTTP_POST_ENCODING_MULTIPART_FORMDATA)))
    return post_process_multipart (pp, post_data, post_data_len);
  /* this should never be reached */
  return MHD_NO;
}

int
MHD_destroy_post_processor (struct MHD_PostProcessor *pp)
{
  int ret;

  /* These internal strings need cleaning up since
     the post-processing may have been interrupted
     at any stage */
  if ((pp->xbuf_pos > 0) || (pp->state != PP_Done))
    ret = MHD_NO;
  else
    ret = MHD_YES;
  pp->have = NE_none;
  free_unmarked (pp);
  if (pp->nested_boundary != NULL)
    free (pp->nested_boundary);
  free (pp);
  return ret;
}

/* end of postprocessor.c */

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