1 const char deanimate_rcs[] = "$Id: deanimate.c,v 1.12.2.1 2004/10/03 12:53:32 david__schmidt Exp $";
2 /*********************************************************************
4 * File : $Source: /cvsroot/ijbswa/current/Attic/deanimate.c,v $
6 * Purpose : Declares functions to manipulate binary images on the
7 * fly. High-level functions include:
8 * - Deanimation of GIF images
9 * - Fixup of malformed comment block in JPEG headers
11 * Functions declared include: gif_deanimate, buf_free,
12 * buf_copy, buf_getbyte, gif_skip_data_block,
13 * gif_extract_image and jpeg_inspect
15 * Copyright : Written by and Copyright (C) 2001 - 2004 by the the
16 * SourceForge Privoxy team. http://www.privoxy.org/
18 * Based on the GIF file format specification (see
19 * http://tronche.com/computer-graphics/gif/gif89a.html)
20 * and ideas from the Image::DeAnim Perl module by
21 * Ken MacFarlane, <ksm+cpan@universal.dca.net>
23 * This program is free software; you can redistribute it
24 * and/or modify it under the terms of the GNU General
25 * Public License as published by the Free Software
26 * Foundation; either version 2 of the License, or (at
27 * your option) any later version.
29 * This program is distributed in the hope that it will
30 * be useful, but WITHOUT ANY WARRANTY; without even the
31 * implied warranty of MERCHANTABILITY or FITNESS FOR A
32 * PARTICULAR PURPOSE. See the GNU General Public
33 * License for more details.
35 * The GNU General Public License should be included with
36 * this file. If not, you can view it at
37 * http://www.gnu.org/copyleft/gpl.html
38 * or write to the Free Software Foundation, Inc., 59
39 * Temple Place - Suite 330, Boston, MA 02111-1307, USA.
42 * $Log: deanimate.c,v $
43 * Revision 1.12.2.1 2004/10/03 12:53:32 david__schmidt
44 * Add the ability to check jpeg images for invalid
45 * lengths of comment blocks. Defensive strategy
46 * against the exploit:
47 * Microsoft Security Bulletin MS04-028
48 * Buffer Overrun in JPEG Processing (GDI+) Could
49 * Allow Code Execution (833987)
50 * Enabled with +inspect-jpegs in actions files.
52 * Revision 1.12 2002/05/12 21:36:29 jongfoster
53 * Correcting function comments
55 * Revision 1.11 2002/03/26 22:29:54 swa
56 * we have a new homepage!
58 * Revision 1.10 2002/03/24 13:25:43 swa
59 * name change related issues
61 * Revision 1.9 2002/03/13 00:27:04 jongfoster
64 * Revision 1.8 2002/03/09 19:42:47 jongfoster
65 * Fixing more warnings
67 * Revision 1.7 2002/03/08 17:46:04 jongfoster
68 * Fixing int/size_t warnings
70 * Revision 1.6 2002/03/07 03:46:17 oes
71 * Fixed compiler warnings
73 * Revision 1.5 2001/09/10 10:16:06 oes
74 * Silenced compiler warnings
76 * Revision 1.4 2001/07/18 12:28:49 oes
77 * - Added feature for extracting the first frame
79 * - Separated image buffer extension into buf_extend
80 * - Extended gif deanimation to GIF87a (untested!)
83 * Revision 1.3 2001/07/15 13:57:50 jongfoster
84 * Adding #includes string.h and miscutil.h
86 * Revision 1.2 2001/07/13 13:46:20 oes
87 * Introduced GIF deanimation feature
90 **********************************************************************/
100 #include "deanimate.h"
101 #include "miscutil.h"
103 const char deanimate_h_rcs[] = DEANIMATE_H_VERSION;
105 /*********************************************************************
107 * Function : buf_free
109 * Description : Safely frees a struct binbuffer
112 * 1 : buf = Pointer to the binbuffer to be freed
116 *********************************************************************/
117 void buf_free(struct binbuffer *buf)
119 if (buf == NULL) return;
121 if (buf->buffer != NULL)
131 /*********************************************************************
133 * Function : buf_extend
135 * Description : Ensure that a given binbuffer can hold a given amount
136 * of bytes, by reallocating its buffer if necessary.
137 * Allocate new mem in chunks of 1024 bytes, so we don't
138 * have to realloc() too often.
141 * 1 : buf = Pointer to the binbuffer
142 * 2 : length = Desired minimum size
145 * Returns : 0 on success, 1 on failiure.
147 *********************************************************************/
148 int buf_extend(struct binbuffer *buf, size_t length)
152 if (buf->offset + length > buf->size)
154 buf->size = ((buf->size + length + (size_t)1023) & ~(size_t)1023);
155 newbuf = (char *)realloc(buf->buffer, buf->size);
164 buf->buffer = newbuf;
173 /*********************************************************************
175 * Function : buf_copy
177 * Description : Safely copies a given amount of bytes from one
178 * struct binbuffer to another, advancing the
179 * offsets appropriately.
182 * 1 : src = Pointer to the source binbuffer
183 * 2 : dst = Pointer to the destination binbuffer
184 * 3 : length = Number of bytes to be copied
186 * Returns : 0 on success, 1 on failiure.
188 *********************************************************************/
189 int buf_copy(struct binbuffer *src, struct binbuffer *dst, size_t length)
193 * Sanity check: Can't copy more data than we have
195 if (src->offset + length > src->size)
201 * Ensure that dst can hold the new data
203 if (buf_extend(dst, length))
209 * Now that it's safe, memcpy() the desired amount of
210 * data from src to dst and adjust the offsets
212 memcpy(dst->buffer + dst->offset, src->buffer + src->offset, length);
213 src->offset += length;
214 dst->offset += length;
221 /*********************************************************************
223 * Function : buf_getbyte
225 * Description : Safely gets a byte from a given binbuffer at a
229 * 1 : src = Pointer to the source binbuffer
230 * 2 : offset = Offset to the desired byte
232 * Returns : The byte on success, or 0 on failiure
234 *********************************************************************/
235 unsigned char buf_getbyte(struct binbuffer *src, size_t offset)
237 if (src->offset + offset < src->size)
239 return (unsigned char)*(src->buffer + src->offset + offset);
249 /*********************************************************************
251 * Function : gif_skip_data_block
253 * Description : Safely advances the offset of a given struct binbuffer
254 * that contains a GIF image and whose offset is
255 * positioned at the start of a data block, behind
259 * 1 : buf = Pointer to the binbuffer
261 * Returns : 0 on success, or 1 on failiure
263 *********************************************************************/
264 int gif_skip_data_block(struct binbuffer *buf)
269 * Data blocks are sequences of chunks, which are headed
270 * by a one-byte length field, with the last chunk having
273 while((c = buf_getbyte(buf, 0)) != '\0')
275 if ((buf->offset += c + 1) >= buf->size - 1)
287 /*********************************************************************
289 * Function : gif_extract_image
291 * Description : Safely extracts an image data block from a given
292 * struct binbuffer that contains a GIF image and whose
293 * offset is positioned at the start of a data block
294 * into a given destination binbuffer.
297 * 1 : src = Pointer to the source binbuffer
298 * 2 : dst = Pointer to the destination binbuffer
300 * Returns : 0 on success, or 1 on failiure
302 *********************************************************************/
303 int gif_extract_image(struct binbuffer *src, struct binbuffer *dst)
308 * Remember the colormap flag and copy the image head
310 c = buf_getbyte(src, 9);
311 if (buf_copy(src, dst, 10))
317 * If the image has a local colormap, copy it.
321 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
326 if (buf_copy(src, dst, 1)) return 1;
329 * Copy the image chunk by chunk.
331 while((c = buf_getbyte(src, 0)) != '\0')
333 if (buf_copy(src, dst, 1 + (size_t) c)) return 1;
335 if (buf_copy(src, dst, 1)) return 1;
338 * Trim and rewind the dst buffer
340 if (NULL == (dst->buffer = (char *)realloc(dst->buffer, dst->offset))) return 1;
341 dst->size = dst->offset;
348 /*********************************************************************
350 * Function : gif_deanimate
352 * Description : Deanimate a given GIF image, i.e. given a GIF with
353 * an (optional) image block and an arbitrary number
354 * of image extension blocks, produce an output GIF with
355 * only one image block that contains the last image
356 * (extenstion) block of the original.
357 * Also strip Comments, Application extenstions, etc.
360 * 1 : src = Pointer to the source binbuffer
361 * 2 : dst = Pointer to the destination binbuffer
362 * 3 : get_first_image = Flag: If set, get the first image
363 * If unset (default), get the last
365 * Returns : 0 on success, or 1 on failiure
367 *********************************************************************/
368 int gif_deanimate(struct binbuffer *src, struct binbuffer *dst, int get_first_image)
371 struct binbuffer *image;
373 if (NULL == src || NULL == dst)
378 c = buf_getbyte(src, 10);
381 * Check & copy GIF header
383 if (strncmp(src->buffer, "GIF89a", 6) && strncmp(src->buffer, "GIF87a", 6))
389 if (buf_copy(src, dst, 13))
396 * Look for global colormap and copy if found.
400 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
407 * Reserve a buffer for the current image block
409 if (NULL == (image = (struct binbuffer *)zalloc(sizeof(*image))))
415 * Parse the GIF block by block and copy the relevant
418 while(src->offset < src->size)
420 switch(buf_getbyte(src, 0))
423 * End-of-GIF Marker: Append current image and return
429 * Image block: Extract to current image buffer.
433 if (gif_extract_image(src, image)) goto failed;
434 if (get_first_image) goto write;
438 * Extension block: Look at next byte and decide
441 switch (buf_getbyte(src, 1))
444 * Image extension: Copy extension header and image
445 * to the current image buffer
449 if (buf_copy(src, image, 8) || buf_getbyte(src, 0) != 0x2c) goto failed;
450 if (gif_extract_image(src, image)) goto failed;
451 if (get_first_image) goto write;
455 * Application extension: Skip
458 if ((src->offset += 14) >= src->size || gif_skip_data_block(src)) goto failed;
462 * Comment extension: Skip
465 if ((src->offset += 2) >= src->size || gif_skip_data_block(src)) goto failed;
469 * Plain text extension: Skip
472 if ((src->offset += 15) >= src->size || gif_skip_data_block(src)) goto failed;
476 * Ooops, what type of extension is that?
484 * Ooops, what type of block is that?
490 } /* -END- while src */
493 * Either we got here by goto, or because the GIF is
494 * bogus and EOF was reached before an end-of-gif marker
503 * Append the current image to dst and return
507 if (buf_copy(image, dst, image->size)) goto failed;
508 if (buf_extend(dst, 1)) goto failed;
509 *(dst->buffer + dst->offset++) = 0x3b;
516 /*********************************************************************
518 * Function : jpeg_inspect
520 * Description : Checks a jpeg image for an invalid length in a
521 * comment block (0xFFFE0000 or 0xFFFE0001) and
522 * changes it to 0xFFFE0002. Defensive strategy
523 * against the exploit:
524 * Microsoft Security Bulletin MS04-028
525 * Buffer Overrun in JPEG Processing (GDI+) Could
526 * Allow Code Execution (833987)
529 * 1 : src = Pointer to the image binbuffer
531 * Returns : 0 on success, or 1 on failiure
533 *********************************************************************/
534 int jpeg_inspect(struct binbuffer *src, struct binbuffer *dst)
538 * We process the image using a simple finite state machine,
539 * searching for byte patterns.
541 enum { J_INIT, /* The initial state */
542 J_FF, /* Found byte 0xFF */
543 J_FE, /* Found bytes 0xFF 0xFE */
544 J_00, /* Found bytes 0xFF 0xFE 0x00 */
546 * Found bytes 0xFF 0xDA; short-circuit to done-ness
547 * since this signals the beginning end of headers.
550 short state = J_INIT;
553 if (NULL == src || NULL == dst)
558 if (buf_copy(src, dst, src->size))
563 /* Need to search the jpg for patterns:
564 * 0xFF 0xFE 0x00 0x00
566 * 0xFF 0xFE 0x00 0x01
567 * from beginning until:
569 * (or the end of the buffer)
570 * If found, change the pattern to 0xFF 0xFE 0x00 0x02
573 for (i = 0; i < dst->size; i++)
584 state = J_DA; /* End of headers - we're done with this image. */
597 if ((c == 0x00) || (c == 0x01))
599 dst->buffer[i] = 2; /* Reset comment block size to 2. */
600 log_error(LOG_LEVEL_INFO, "JPEG comment exploit removed.");
602 * I'm unsure if we can have more than one comment block. Just in case,
603 * we'll scan the rest of the header for more by going back to J_INIT
604 * state. If there is no possibility of >1 comment block, we could
605 * short-circuit to done-ness here.