1 const char deanimate_rcs[] = "$Id: deanimate.c,v 1.14 2006/07/18 14:48:45 david__schmidt Exp $";
2 /*********************************************************************
4 * File : $Source: /cvsroot/ijbswa/current/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, 2006 by 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 1.14 2006/07/18 14:48:45 david__schmidt
44 * Reorganizing the repository: swapping out what was HEAD (the old 3.1 branch)
45 * with what was really the latest development (the v_3_0_branch branch)
47 * Revision 1.12.2.1 2004/10/03 12:53:32 david__schmidt
48 * Add the ability to check jpeg images for invalid
49 * lengths of comment blocks. Defensive strategy
50 * against the exploit:
51 * Microsoft Security Bulletin MS04-028
52 * Buffer Overrun in JPEG Processing (GDI+) Could
53 * Allow Code Execution (833987)
54 * Enabled with +inspect-jpegs in actions files.
56 * Revision 1.12 2002/05/12 21:36:29 jongfoster
57 * Correcting function comments
59 * Revision 1.11 2002/03/26 22:29:54 swa
60 * we have a new homepage!
62 * Revision 1.10 2002/03/24 13:25:43 swa
63 * name change related issues
65 * Revision 1.9 2002/03/13 00:27:04 jongfoster
68 * Revision 1.8 2002/03/09 19:42:47 jongfoster
69 * Fixing more warnings
71 * Revision 1.7 2002/03/08 17:46:04 jongfoster
72 * Fixing int/size_t warnings
74 * Revision 1.6 2002/03/07 03:46:17 oes
75 * Fixed compiler warnings
77 * Revision 1.5 2001/09/10 10:16:06 oes
78 * Silenced compiler warnings
80 * Revision 1.4 2001/07/18 12:28:49 oes
81 * - Added feature for extracting the first frame
83 * - Separated image buffer extension into buf_extend
84 * - Extended gif deanimation to GIF87a (untested!)
87 * Revision 1.3 2001/07/15 13:57:50 jongfoster
88 * Adding #includes string.h and miscutil.h
90 * Revision 1.2 2001/07/13 13:46:20 oes
91 * Introduced GIF deanimation feature
94 **********************************************************************/
104 #include "deanimate.h"
105 #include "miscutil.h"
107 const char deanimate_h_rcs[] = DEANIMATE_H_VERSION;
109 /*********************************************************************
111 * Function : buf_free
113 * Description : Safely frees a struct binbuffer
116 * 1 : buf = Pointer to the binbuffer to be freed
120 *********************************************************************/
121 void buf_free(struct binbuffer *buf)
123 if (buf == NULL) return;
125 if (buf->buffer != NULL)
135 /*********************************************************************
137 * Function : buf_extend
139 * Description : Ensure that a given binbuffer can hold a given amount
140 * of bytes, by reallocating its buffer if necessary.
141 * Allocate new mem in chunks of 1024 bytes, so we don't
142 * have to realloc() too often.
145 * 1 : buf = Pointer to the binbuffer
146 * 2 : length = Desired minimum size
149 * Returns : 0 on success, 1 on failiure.
151 *********************************************************************/
152 int buf_extend(struct binbuffer *buf, size_t length)
156 if (buf->offset + length > buf->size)
158 buf->size = ((buf->size + length + (size_t)1023) & ~(size_t)1023);
159 newbuf = (char *)realloc(buf->buffer, buf->size);
168 buf->buffer = newbuf;
177 /*********************************************************************
179 * Function : buf_copy
181 * Description : Safely copies a given amount of bytes from one
182 * struct binbuffer to another, advancing the
183 * offsets appropriately.
186 * 1 : src = Pointer to the source binbuffer
187 * 2 : dst = Pointer to the destination binbuffer
188 * 3 : length = Number of bytes to be copied
190 * Returns : 0 on success, 1 on failiure.
192 *********************************************************************/
193 int buf_copy(struct binbuffer *src, struct binbuffer *dst, size_t length)
197 * Sanity check: Can't copy more data than we have
199 if (src->offset + length > src->size)
205 * Ensure that dst can hold the new data
207 if (buf_extend(dst, length))
213 * Now that it's safe, memcpy() the desired amount of
214 * data from src to dst and adjust the offsets
216 memcpy(dst->buffer + dst->offset, src->buffer + src->offset, length);
217 src->offset += length;
218 dst->offset += length;
225 /*********************************************************************
227 * Function : buf_getbyte
229 * Description : Safely gets a byte from a given binbuffer at a
233 * 1 : src = Pointer to the source binbuffer
234 * 2 : offset = Offset to the desired byte
236 * Returns : The byte on success, or 0 on failiure
238 *********************************************************************/
239 unsigned char buf_getbyte(const struct binbuffer *src, size_t offset)
241 if (src->offset + offset < src->size)
243 return (unsigned char)*(src->buffer + src->offset + offset);
253 /*********************************************************************
255 * Function : gif_skip_data_block
257 * Description : Safely advances the offset of a given struct binbuffer
258 * that contains a GIF image and whose offset is
259 * positioned at the start of a data block, behind
263 * 1 : buf = Pointer to the binbuffer
265 * Returns : 0 on success, or 1 on failiure
267 *********************************************************************/
268 int gif_skip_data_block(struct binbuffer *buf)
273 * Data blocks are sequences of chunks, which are headed
274 * by a one-byte length field, with the last chunk having
277 while((c = buf_getbyte(buf, 0)) != '\0')
279 buf->offset += (size_t)c + 1;
280 if (buf->offset >= buf->size - 1)
292 /*********************************************************************
294 * Function : gif_extract_image
296 * Description : Safely extracts an image data block from a given
297 * struct binbuffer that contains a GIF image and whose
298 * offset is positioned at the start of a data block
299 * into a given destination binbuffer.
302 * 1 : src = Pointer to the source binbuffer
303 * 2 : dst = Pointer to the destination binbuffer
305 * Returns : 0 on success, or 1 on failiure
307 *********************************************************************/
308 int gif_extract_image(struct binbuffer *src, struct binbuffer *dst)
313 * Remember the colormap flag and copy the image head
315 c = buf_getbyte(src, 9);
316 if (buf_copy(src, dst, 10))
322 * If the image has a local colormap, copy it.
326 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
331 if (buf_copy(src, dst, 1)) return 1;
334 * Copy the image chunk by chunk.
336 while((c = buf_getbyte(src, 0)) != '\0')
338 if (buf_copy(src, dst, 1 + (size_t) c)) return 1;
340 if (buf_copy(src, dst, 1)) return 1;
343 * Trim and rewind the dst buffer
345 if (NULL == (dst->buffer = (char *)realloc(dst->buffer, dst->offset))) return 1;
346 dst->size = dst->offset;
353 /*********************************************************************
355 * Function : gif_deanimate
357 * Description : Deanimate a given GIF image, i.e. given a GIF with
358 * an (optional) image block and an arbitrary number
359 * of image extension blocks, produce an output GIF with
360 * only one image block that contains the last image
361 * (extenstion) block of the original.
362 * Also strip Comments, Application extenstions, etc.
365 * 1 : src = Pointer to the source binbuffer
366 * 2 : dst = Pointer to the destination binbuffer
367 * 3 : get_first_image = Flag: If set, get the first image
368 * If unset (default), get the last
370 * Returns : 0 on success, or 1 on failiure
372 *********************************************************************/
373 int gif_deanimate(struct binbuffer *src, struct binbuffer *dst, int get_first_image)
376 struct binbuffer *image;
378 if (NULL == src || NULL == dst)
383 c = buf_getbyte(src, 10);
386 * Check & copy GIF header
388 if (strncmp(src->buffer, "GIF89a", 6) && strncmp(src->buffer, "GIF87a", 6))
394 if (buf_copy(src, dst, 13))
401 * Look for global colormap and copy if found.
405 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
412 * Reserve a buffer for the current image block
414 if (NULL == (image = (struct binbuffer *)zalloc(sizeof(*image))))
420 * Parse the GIF block by block and copy the relevant
423 while(src->offset < src->size)
425 switch(buf_getbyte(src, 0))
428 * End-of-GIF Marker: Append current image and return
434 * Image block: Extract to current image buffer.
438 if (gif_extract_image(src, image)) goto failed;
439 if (get_first_image) goto write;
443 * Extension block: Look at next byte and decide
446 switch (buf_getbyte(src, 1))
449 * Image extension: Copy extension header and image
450 * to the current image buffer
454 if (buf_copy(src, image, 8) || buf_getbyte(src, 0) != 0x2c) goto failed;
455 if (gif_extract_image(src, image)) goto failed;
456 if (get_first_image) goto write;
460 * Application extension: Skip
463 if ((src->offset += 14) >= src->size || gif_skip_data_block(src)) goto failed;
467 * Comment extension: Skip
470 if ((src->offset += 2) >= src->size || gif_skip_data_block(src)) goto failed;
474 * Plain text extension: Skip
477 if ((src->offset += 15) >= src->size || gif_skip_data_block(src)) goto failed;
481 * Ooops, what type of extension is that?
489 * Ooops, what type of block is that?
495 } /* -END- while src */
498 * Either we got here by goto, or because the GIF is
499 * bogus and EOF was reached before an end-of-gif marker
508 * Append the current image to dst and return
512 if (buf_copy(image, dst, image->size)) goto failed;
513 if (buf_extend(dst, 1)) goto failed;
514 *(dst->buffer + dst->offset++) = 0x3b;
521 /*********************************************************************
523 * Function : jpeg_inspect
525 * Description : Checks a jpeg image for an invalid length in a
526 * comment block (0xFFFE0000 or 0xFFFE0001) and
527 * changes it to 0xFFFE0002. Defensive strategy
528 * against the exploit:
529 * Microsoft Security Bulletin MS04-028
530 * Buffer Overrun in JPEG Processing (GDI+) Could
531 * Allow Code Execution (833987)
534 * 1 : src = Pointer to the image binbuffer
536 * Returns : 0 on success, or 1 on failiure
538 *********************************************************************/
539 int jpeg_inspect(struct binbuffer *src, struct binbuffer *dst)
543 * We process the image using a simple finite state machine,
544 * searching for byte patterns.
546 enum { J_INIT, /* The initial state */
547 J_FF, /* Found byte 0xFF */
548 J_FE, /* Found bytes 0xFF 0xFE */
549 J_00, /* Found bytes 0xFF 0xFE 0x00 */
551 * Found bytes 0xFF 0xDA; short-circuit to done-ness
552 * since this signals the beginning end of headers.
555 short state = J_INIT;
558 if (NULL == src || NULL == dst)
563 if (buf_copy(src, dst, src->size))
568 /* Need to search the jpg for patterns:
569 * 0xFF 0xFE 0x00 0x00
571 * 0xFF 0xFE 0x00 0x01
572 * from beginning until:
574 * (or the end of the buffer)
575 * If found, change the pattern to 0xFF 0xFE 0x00 0x02
578 for (i = 0; i < dst->size; i++)
589 state = J_DA; /* End of headers - we're done with this image. */
602 if ((c == 0x00) || (c == 0x01))
604 dst->buffer[i] = 2; /* Reset comment block size to 2. */
605 log_error(LOG_LEVEL_INFO, "JPEG comment exploit removed.");
607 * I'm unsure if we can have more than one comment block. Just in case,
608 * we'll scan the rest of the header for more by going back to J_INIT
609 * state. If there is no possibility of >1 comment block, we could
610 * short-circuit to done-ness here.