/* exif-mnote-data-canon.c

 *

 * Copyright (c) 2002, 2003 Lutz Mueller <lutz@users.sourceforge.net>

 * Copyright (c) 2003 Matthieu Castet <mat-c@users.sourceforge.net>

 *

 * 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 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.

 *

 * SPDX-License-Identifier: LGPL-2.0-or-later

 */

#include <config.h>

#include "exif-mnote-data-canon.h"

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#include <libexif/exif-byte-order.h>

#include <libexif/exif-utils.h>

#include <libexif/exif-data.h>

#define CHECKOVERFLOW(offset,datasize,structsize) (( (offset) >= (datasize)) || ((structsize) > (datasize)) || ((offset) > (datasize) - (structsize) ))

/* Total size limit to prevent abuse by DoS */

#define FAILSAFE_SIZE_MAX 1000000L

static void

exif_mnote_data_canon_clear (ExifMnoteDataCanon *n)

{

  ExifMnoteData *d = (ExifMnoteData *) n;

  unsigned int i;

  if (!n) return;

  if (n->entries) {

    for (i = 0; i < n->count; i++)

      if (n->entries[i].data) {

        exif_mem_free (d->mem, n->entries[i].data);

        n->entries[i].data = NULL;

      }

    exif_mem_free (d->mem, n->entries);

    n->entries = NULL;

    n->count = 0;

  }

}

static void

exif_mnote_data_canon_free (ExifMnoteData *n)

{

  if (!n) return;

  exif_mnote_data_canon_clear ((ExifMnoteDataCanon *) n);

}

static void

exif_mnote_data_canon_get_tags (ExifMnoteDataCanon *dc, unsigned int n,

    unsigned int *m, unsigned int *s)

{

  unsigned int from = 0, to;

  if (s) *s = 0;

  if (!dc || !m) return;

  for (*m = 0; *m < dc->count; (*m)++) {

    to = from + mnote_canon_entry_count_values (&dc->entries[*m]);

    if (to > n) {

      if (s) *s = n - from;

      break;

    }

    from = to;

  }

}

static char *

exif_mnote_data_canon_get_value (ExifMnoteData *note, unsigned int n, char *val, unsigned int maxlen)

{

  ExifMnoteDataCanon *dc = (ExifMnoteDataCanon *) note;

  unsigned int m, s;

  if (!dc) return NULL;

  exif_mnote_data_canon_get_tags (dc, n, &m, &s);

  if (m >= dc->count) return NULL;

  return mnote_canon_entry_get_value (&dc->entries[m], s, val, maxlen);

}

static void

exif_mnote_data_canon_set_byte_order (ExifMnoteData *d, ExifByteOrder o)

{

  ExifByteOrder o_orig;

  ExifMnoteDataCanon *n = (ExifMnoteDataCanon *) d;

  unsigned int i;

  if (!n) return;

  o_orig = n->order;

  n->order = o;

  for (i = 0; i < n->count; i++) {

    if (n->entries[i].components && (n->entries[i].size/n->entries[i].components < exif_format_get_size (n->entries[i].format)))

      continue;

    n->entries[i].order = o;

    exif_array_set_byte_order (n->entries[i].format, n->entries[i].data,

        n->entries[i].components, o_orig, o);

  }

}

static void

exif_mnote_data_canon_set_offset (ExifMnoteData *n, unsigned int o)

{

  if (n) ((ExifMnoteDataCanon *) n)->offset = o;

}

static void

exif_mnote_data_canon_save (ExifMnoteData *ne, 

  unsigned char **buf, unsigned int *buf_size)

{

  ExifMnoteDataCanon *n = (ExifMnoteDataCanon *) ne;

  size_t i, o, s, doff;

  unsigned char *t;

  size_t ts;

  if (!n || !buf || !buf_size) return;

  /*

   * Allocate enough memory for all entries and the number

   * of entries.

   */

  *buf_size = 2 + n->count * 12 + 4;

  *buf = exif_mem_alloc (ne->mem, sizeof (char) * *buf_size);

  if (!*buf) {

    EXIF_LOG_NO_MEMORY(ne->log, "ExifMnoteCanon", *buf_size);

    return;

  }

  /* Save the number of entries */

  exif_set_short (*buf, n->order, (ExifShort) n->count);

  /* Save each entry */

  for (i = 0; i < n->count; i++) {

    o = 2 + i * 12;

    exif_set_short (*buf + o + 0, n->order, (ExifShort) n->entries[i].tag);

    exif_set_short (*buf + o + 2, n->order, (ExifShort) n->entries[i].format);

    exif_set_long  (*buf + o + 4, n->order,

        n->entries[i].components);

    o += 8;

    s = exif_format_get_size (n->entries[i].format) *

            n->entries[i].components;

    if (s > 65536) {

      /* Corrupt data: EXIF data size is limited to the

       * maximum size of a JPEG segment (64 kb).

       */

      continue;

    }

    if (s > 4) {

      ts = *buf_size + s;

      /* Ensure even offsets. Set padding bytes to 0. */

      if (s & 1) ts += 1;

      t = exif_mem_realloc (ne->mem, *buf,

             sizeof (char) * ts);

      if (!t) {

        EXIF_LOG_NO_MEMORY(ne->log, "ExifMnoteCanon", ts);

        return;

      }

      *buf = t;

      *buf_size = ts;

      doff = *buf_size - s;

      if (s & 1) { doff--; *(*buf + *buf_size - 1) = '\0'; }

      exif_set_long (*buf + o, n->order, n->offset + doff);

    } else

      doff = o;

    /*

     * Write the data. Fill unneeded bytes with 0. Do not

     * crash if data is NULL.

     */

    if (!n->entries[i].data) memset (*buf + doff, 0, s);

    else memcpy (*buf + doff, n->entries[i].data, s);

    if (s < 4) memset (*buf + doff + s, 0, (4 - s));

  }

}

/* XXX

 * FIXME: exif_mnote_data_canon_load() may fail and there is no

 *        semantics to express that.

 *        See bug #1054323 for details, especially the comment by liblit

 *        after it has supposedly been fixed:

 *

 *        https://sourceforge.net/tracker/?func=detail&aid=1054323&group_id=12272&atid=112272

 *        Unfortunately, the "return" statements aren't commented at

 *        all, so it isn't trivial to find out what is a normal

 *        return, and what is a reaction to an error condition.

 */

static void

exif_mnote_data_canon_load (ExifMnoteData *ne,

  const unsigned char *buf, unsigned int buf_size)

{

  ExifMnoteDataCanon *n = (ExifMnoteDataCanon *) ne;

  ExifShort c;

  size_t i, tcount, o, datao;

  long failsafe_size = 0;

  if (!n) return;

  if (!buf || !buf_size) {

    exif_log (ne->log, EXIF_LOG_CODE_CORRUPT_DATA,

        "ExifMnoteCanon", "Short MakerNote");

    return;

  }

  if (CHECKOVERFLOW(n->offset, buf_size, 8)) {

    exif_log (ne->log, EXIF_LOG_CODE_CORRUPT_DATA,

        "ExifMnoteCanon", "Short MakerNote");

    return;

  }

  datao = 6 + n->offset;

  /* Read the number of tags */

  c = exif_get_short (buf + datao, n->order);

  datao += 2;

  /* Just use an arbitrary max tag limit here to avoid needing to much memory or time. There are 24 named tags currently.

   * current 2020 camera EOS M6 Mark 2 had 156 entries.

   * The format allows specifying the same range of memory as often as it can, so this multiplies quickly. */

  if (c > 250) {

    exif_log (ne->log, EXIF_LOG_CODE_CORRUPT_DATA, "ExifMnoteCanon", "Too much tags (%d) in Canon MakerNote", c);

    return;

  }

  /* Remove any old entries */

  exif_mnote_data_canon_clear (n);

  /* Reserve enough space for all the possible MakerNote tags */

  n->entries = exif_mem_alloc (ne->mem, sizeof (MnoteCanonEntry) * c);

  if (!n->entries) {

    EXIF_LOG_NO_MEMORY(ne->log, "ExifMnoteCanon", sizeof (MnoteCanonEntry) * c);

    return;

  }

  /* Parse the entries */

  tcount = 0;

  for (i = c, o = datao; i; --i, o += 12) {

    size_t s;

    memset(&n->entries[tcount], 0, sizeof(MnoteCanonEntry));

    if (CHECKOVERFLOW(o,buf_size,12)) {

      exif_log (ne->log, EXIF_LOG_CODE_CORRUPT_DATA,

        "ExifMnoteCanon", "Short MakerNote");

      break;

    }

    n->entries[tcount].tag        = exif_get_short (buf + o, n->order);

    n->entries[tcount].format     = exif_get_short (buf + o + 2, n->order);

    n->entries[tcount].components = exif_get_long (buf + o + 4, n->order);

    n->entries[tcount].order      = n->order;

    exif_log (ne->log, EXIF_LOG_CODE_DEBUG, "ExifMnoteCanon",

      "Loading entry 0x%x ('%s')...", n->entries[tcount].tag,

       mnote_canon_tag_get_name (n->entries[tcount].tag));

    /* Check if we overflow the multiplication. Use buf_size as the max size for integer overflow detection,

     * we will check the buffer sizes closer later. */

    if (  exif_format_get_size (n->entries[tcount].format) &&

      buf_size / exif_format_get_size (n->entries[tcount].format) < n->entries[tcount].components

    ) {

      exif_log (ne->log, EXIF_LOG_CODE_CORRUPT_DATA,

          "ExifMnoteCanon", "Tag size overflow detected (%u * %lu)", exif_format_get_size (n->entries[tcount].format), n->entries[tcount].components);

      continue;

    }

    /*

     * Size? If bigger than 4 bytes, the actual data is not

     * in the entry but somewhere else (offset).

     */

    s = exif_format_get_size (n->entries[tcount].format) * 

                  n->entries[tcount].components;

    n->entries[tcount].size = s;

    if (!s) {

      exif_log (ne->log, EXIF_LOG_CODE_CORRUPT_DATA,

          "ExifMnoteCanon",

          "Invalid zero-length tag size");

      continue;

    } else {

      size_t dataofs = o + 8;

      if (s > 4) dataofs = exif_get_long (buf + dataofs, n->order) + 6;

      if (CHECKOVERFLOW(dataofs, buf_size, s)) {

        exif_log (ne->log, EXIF_LOG_CODE_DEBUG,

          "ExifMnoteCanon",

          "Tag data past end of buffer (%u > %u)",

          (unsigned)(dataofs + s), buf_size);

        continue;

      }

      n->entries[tcount].data = exif_mem_alloc (ne->mem, s);

      if (!n->entries[tcount].data) {

        EXIF_LOG_NO_MEMORY(ne->log, "ExifMnoteCanon", s);

        continue;

      }

      memcpy (n->entries[tcount].data, buf + dataofs, s);

    }

    /* Track the size of decoded tag data. A malicious file could

     * be crafted to cause extremely large values here without

     * tripping any buffer range checks.  This is especially bad

     * with the libexif representation of Canon MakerNotes because

     * some arrays are turned into individual tags that the

     * application must loop around. */

    failsafe_size += mnote_canon_entry_count_values(&n->entries[tcount]);

    if (failsafe_size > FAILSAFE_SIZE_MAX) {

      /* Abort if the total size of the data in the tags extraordinarily large, */

      exif_mem_free (ne->mem, n->entries[tcount].data);

      exif_log (ne->log, EXIF_LOG_CODE_CORRUPT_DATA,

            "ExifMnoteCanon", "Failsafe tag size overflow (%lu > %ld)",

            failsafe_size, FAILSAFE_SIZE_MAX);

      break;

    }

    /* Tag was successfully parsed */

    ++tcount;

  }

  /* Store the count of successfully parsed tags */

  n->count = tcount;

}

static unsigned int

exif_mnote_data_canon_count (ExifMnoteData *n)

{

  ExifMnoteDataCanon *dc = (ExifMnoteDataCanon *) n;

  unsigned int i, c;

  for (i = c = 0; dc && (i < dc->count); i++)

    c += mnote_canon_entry_count_values (&dc->entries[i]);

  return c;

}

static unsigned int

exif_mnote_data_canon_get_id (ExifMnoteData *d, unsigned int i)

{

  ExifMnoteDataCanon *dc = (ExifMnoteDataCanon *) d;

  unsigned int m;

  if (!dc) return 0;

  exif_mnote_data_canon_get_tags (dc, i, &m, NULL);

  if (m >= dc->count) return 0;

  return dc->entries[m].tag;

}

static const char *

exif_mnote_data_canon_get_name (ExifMnoteData *note, unsigned int i)

{

  ExifMnoteDataCanon *dc = (ExifMnoteDataCanon *) note;

  unsigned int m, s;

  if (!dc) return NULL;

  exif_mnote_data_canon_get_tags (dc, i, &m, &s);

  if (m >= dc->count) return NULL;

  return mnote_canon_tag_get_name_sub (dc->entries[m].tag, s, dc->options);

}

static const char *

exif_mnote_data_canon_get_title (ExifMnoteData *note, unsigned int i)

{

  ExifMnoteDataCanon *dc = (ExifMnoteDataCanon *) note;

  unsigned int m, s;

  if (!dc) return NULL;

  exif_mnote_data_canon_get_tags (dc, i, &m, &s);

  if (m >= dc->count) return NULL;

  return mnote_canon_tag_get_title_sub (dc->entries[m].tag, s, dc->options);

}

static const char *

exif_mnote_data_canon_get_description (ExifMnoteData *note, unsigned int i)

{

  ExifMnoteDataCanon *dc = (ExifMnoteDataCanon *) note;

  unsigned int m;

  if (!dc) return NULL;

  exif_mnote_data_canon_get_tags (dc, i, &m, NULL);

  if (m >= dc->count) return NULL;

  return mnote_canon_tag_get_description (dc->entries[m].tag);

}

int

exif_mnote_data_canon_identify (const ExifData *ed, const ExifEntry *e)

{

  char value[8];

  ExifEntry *em = exif_data_get_entry (ed, EXIF_TAG_MAKE);

  if (!em) 

    return 0;

  (void) e;  /* unused */

  return !strcmp (exif_entry_get_value (em, value, sizeof (value)), "Canon");

}

ExifMnoteData *

exif_mnote_data_canon_new (ExifMem *mem, ExifDataOption o)

{

  ExifMnoteData *d;

  ExifMnoteDataCanon *dc;

  if (!mem) return NULL;

  d = exif_mem_alloc (mem, sizeof (ExifMnoteDataCanon));

  if (!d)

    return NULL;

  exif_mnote_data_construct (d, mem);

  /* Set up function pointers */

  d->methods.free            = exif_mnote_data_canon_free;

  d->methods.set_byte_order  = exif_mnote_data_canon_set_byte_order;

  d->methods.set_offset      = exif_mnote_data_canon_set_offset;

  d->methods.load            = exif_mnote_data_canon_load;

  d->methods.save            = exif_mnote_data_canon_save;

  d->methods.count           = exif_mnote_data_canon_count;

  d->methods.get_id          = exif_mnote_data_canon_get_id;

  d->methods.get_name        = exif_mnote_data_canon_get_name;

  d->methods.get_title       = exif_mnote_data_canon_get_title;

  d->methods.get_description = exif_mnote_data_canon_get_description;

  d->methods.get_value       = exif_mnote_data_canon_get_value;

  dc = (ExifMnoteDataCanon*)d;

  dc->options = o;

  return d;

}