1 const char deanimate_rcs[] = "$Id: deanimate.c,v 1.16 2007/07/14 08:01:58 fabiankeil 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 1.16 2007/07/14 08:01:58 fabiankeil
46 * Revision 1.15 2007/01/03 14:39:19 fabiankeil
47 * Fix a gcc43 warning and mark the binbuffer
48 * as immutable for buf_getbyte().
50 * Revision 1.14 2006/07/18 14:48:45 david__schmidt
51 * Reorganizing the repository: swapping out what was HEAD (the old 3.1 branch)
52 * with what was really the latest development (the v_3_0_branch branch)
54 * Revision 1.12.2.1 2004/10/03 12:53:32 david__schmidt
55 * Add the ability to check jpeg images for invalid
56 * lengths of comment blocks. Defensive strategy
57 * against the exploit:
58 * Microsoft Security Bulletin MS04-028
59 * Buffer Overrun in JPEG Processing (GDI+) Could
60 * Allow Code Execution (833987)
61 * Enabled with +inspect-jpegs in actions files.
63 * Revision 1.12 2002/05/12 21:36:29 jongfoster
64 * Correcting function comments
66 * Revision 1.11 2002/03/26 22:29:54 swa
67 * we have a new homepage!
69 * Revision 1.10 2002/03/24 13:25:43 swa
70 * name change related issues
72 * Revision 1.9 2002/03/13 00:27:04 jongfoster
75 * Revision 1.8 2002/03/09 19:42:47 jongfoster
76 * Fixing more warnings
78 * Revision 1.7 2002/03/08 17:46:04 jongfoster
79 * Fixing int/size_t warnings
81 * Revision 1.6 2002/03/07 03:46:17 oes
82 * Fixed compiler warnings
84 * Revision 1.5 2001/09/10 10:16:06 oes
85 * Silenced compiler warnings
87 * Revision 1.4 2001/07/18 12:28:49 oes
88 * - Added feature for extracting the first frame
90 * - Separated image buffer extension into buf_extend
91 * - Extended gif deanimation to GIF87a (untested!)
94 * Revision 1.3 2001/07/15 13:57:50 jongfoster
95 * Adding #includes string.h and miscutil.h
97 * Revision 1.2 2001/07/13 13:46:20 oes
98 * Introduced GIF deanimation feature
101 **********************************************************************/
111 #include "deanimate.h"
112 #include "miscutil.h"
114 const char deanimate_h_rcs[] = DEANIMATE_H_VERSION;
116 /*********************************************************************
118 * Function : buf_free
120 * Description : Safely frees a struct binbuffer
123 * 1 : buf = Pointer to the binbuffer to be freed
127 *********************************************************************/
128 void buf_free(struct binbuffer *buf)
130 if (buf == NULL) return;
132 if (buf->buffer != NULL)
142 /*********************************************************************
144 * Function : buf_extend
146 * Description : Ensure that a given binbuffer can hold a given amount
147 * of bytes, by reallocating its buffer if necessary.
148 * Allocate new mem in chunks of 1024 bytes, so we don't
149 * have to realloc() too often.
152 * 1 : buf = Pointer to the binbuffer
153 * 2 : length = Desired minimum size
156 * Returns : 0 on success, 1 on failure.
158 *********************************************************************/
159 static int buf_extend(struct binbuffer *buf, size_t length)
163 if (buf->offset + length > buf->size)
165 buf->size = ((buf->size + length + (size_t)1023) & ~(size_t)1023);
166 newbuf = (char *)realloc(buf->buffer, buf->size);
175 buf->buffer = newbuf;
184 /*********************************************************************
186 * Function : buf_copy
188 * Description : Safely copies a given amount of bytes from one
189 * struct binbuffer to another, advancing the
190 * offsets appropriately.
193 * 1 : src = Pointer to the source binbuffer
194 * 2 : dst = Pointer to the destination binbuffer
195 * 3 : length = Number of bytes to be copied
197 * Returns : 0 on success, 1 on failure.
199 *********************************************************************/
200 static int buf_copy(struct binbuffer *src, struct binbuffer *dst, size_t length)
204 * Sanity check: Can't copy more data than we have
206 if (src->offset + length > src->size)
212 * Ensure that dst can hold the new data
214 if (buf_extend(dst, length))
220 * Now that it's safe, memcpy() the desired amount of
221 * data from src to dst and adjust the offsets
223 memcpy(dst->buffer + dst->offset, src->buffer + src->offset, length);
224 src->offset += length;
225 dst->offset += length;
232 /*********************************************************************
234 * Function : buf_getbyte
236 * Description : Safely gets a byte from a given binbuffer at a
240 * 1 : src = Pointer to the source binbuffer
241 * 2 : offset = Offset to the desired byte
243 * Returns : The byte on success, or 0 on failure
245 *********************************************************************/
246 static unsigned char buf_getbyte(const struct binbuffer *src, size_t offset)
248 if (src->offset + offset < src->size)
250 return (unsigned char)*(src->buffer + src->offset + offset);
260 /*********************************************************************
262 * Function : gif_skip_data_block
264 * Description : Safely advances the offset of a given struct binbuffer
265 * that contains a GIF image and whose offset is
266 * positioned at the start of a data block, behind
270 * 1 : buf = Pointer to the binbuffer
272 * Returns : 0 on success, or 1 on failure
274 *********************************************************************/
275 static int gif_skip_data_block(struct binbuffer *buf)
280 * Data blocks are sequences of chunks, which are headed
281 * by a one-byte length field, with the last chunk having
284 while((c = buf_getbyte(buf, 0)) != '\0')
286 buf->offset += (size_t)c + 1;
287 if (buf->offset >= buf->size - 1)
299 /*********************************************************************
301 * Function : gif_extract_image
303 * Description : Safely extracts an image data block from a given
304 * struct binbuffer that contains a GIF image and whose
305 * offset is positioned at the start of a data block
306 * into a given destination binbuffer.
309 * 1 : src = Pointer to the source binbuffer
310 * 2 : dst = Pointer to the destination binbuffer
312 * Returns : 0 on success, or 1 on failure
314 *********************************************************************/
315 static int gif_extract_image(struct binbuffer *src, struct binbuffer *dst)
320 * Remember the colormap flag and copy the image head
322 c = buf_getbyte(src, 9);
323 if (buf_copy(src, dst, 10))
329 * If the image has a local colormap, copy it.
333 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
338 if (buf_copy(src, dst, 1)) return 1;
341 * Copy the image chunk by chunk.
343 while((c = buf_getbyte(src, 0)) != '\0')
345 if (buf_copy(src, dst, 1 + (size_t) c)) return 1;
347 if (buf_copy(src, dst, 1)) return 1;
350 * Trim and rewind the dst buffer
352 if (NULL == (dst->buffer = (char *)realloc(dst->buffer, dst->offset))) return 1;
353 dst->size = dst->offset;
360 /*********************************************************************
362 * Function : gif_deanimate
364 * Description : Deanimate a given GIF image, i.e. given a GIF with
365 * an (optional) image block and an arbitrary number
366 * of image extension blocks, produce an output GIF with
367 * only one image block that contains the last image
368 * (extenstion) block of the original.
369 * Also strip Comments, Application extenstions, etc.
372 * 1 : src = Pointer to the source binbuffer
373 * 2 : dst = Pointer to the destination binbuffer
374 * 3 : get_first_image = Flag: If set, get the first image
375 * If unset (default), get the last
377 * Returns : 0 on success, or 1 on failure
379 *********************************************************************/
380 int gif_deanimate(struct binbuffer *src, struct binbuffer *dst, int get_first_image)
383 struct binbuffer *image;
385 if (NULL == src || NULL == dst)
390 c = buf_getbyte(src, 10);
393 * Check & copy GIF header
395 if (strncmp(src->buffer, "GIF89a", 6) && strncmp(src->buffer, "GIF87a", 6))
401 if (buf_copy(src, dst, 13))
408 * Look for global colormap and copy if found.
412 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
419 * Reserve a buffer for the current image block
421 if (NULL == (image = (struct binbuffer *)zalloc(sizeof(*image))))
427 * Parse the GIF block by block and copy the relevant
430 while(src->offset < src->size)
432 switch(buf_getbyte(src, 0))
435 * End-of-GIF Marker: Append current image and return
441 * Image block: Extract to current image buffer.
445 if (gif_extract_image(src, image)) goto failed;
446 if (get_first_image) goto write;
450 * Extension block: Look at next byte and decide
453 switch (buf_getbyte(src, 1))
456 * Image extension: Copy extension header and image
457 * to the current image buffer
461 if (buf_copy(src, image, 8) || buf_getbyte(src, 0) != 0x2c) goto failed;
462 if (gif_extract_image(src, image)) goto failed;
463 if (get_first_image) goto write;
467 * Application extension: Skip
470 if ((src->offset += 14) >= src->size || gif_skip_data_block(src)) goto failed;
474 * Comment extension: Skip
477 if ((src->offset += 2) >= src->size || gif_skip_data_block(src)) goto failed;
481 * Plain text extension: Skip
484 if ((src->offset += 15) >= src->size || gif_skip_data_block(src)) goto failed;
488 * Ooops, what type of extension is that?
496 * Ooops, what type of block is that?
502 } /* -END- while src */
505 * Either we got here by goto, or because the GIF is
506 * bogus and EOF was reached before an end-of-gif marker
515 * Append the current image to dst and return
519 if (buf_copy(image, dst, image->size)) goto failed;
520 if (buf_extend(dst, 1)) goto failed;
521 *(dst->buffer + dst->offset++) = 0x3b;
528 /*********************************************************************
530 * Function : jpeg_inspect
532 * Description : Checks a jpeg image for an invalid length in a
533 * comment block (0xFFFE0000 or 0xFFFE0001) and
534 * changes it to 0xFFFE0002. Defensive strategy
535 * against the exploit:
536 * Microsoft Security Bulletin MS04-028
537 * Buffer Overrun in JPEG Processing (GDI+) Could
538 * Allow Code Execution (833987)
541 * 1 : src = Pointer to the image binbuffer
543 * Returns : 0 on success, or 1 on failure
545 *********************************************************************/
546 int jpeg_inspect(struct binbuffer *src, struct binbuffer *dst)
550 * We process the image using a simple finite state machine,
551 * searching for byte patterns.
553 enum { J_INIT, /* The initial state */
554 J_FF, /* Found byte 0xFF */
555 J_FE, /* Found bytes 0xFF 0xFE */
556 J_00, /* Found bytes 0xFF 0xFE 0x00 */
558 * Found bytes 0xFF 0xDA; short-circuit to done-ness
559 * since this signals the beginning end of headers.
562 short state = J_INIT;
565 if (NULL == src || NULL == dst)
570 if (buf_copy(src, dst, src->size))
575 /* Need to search the jpg for patterns:
576 * 0xFF 0xFE 0x00 0x00
578 * 0xFF 0xFE 0x00 0x01
579 * from beginning until:
581 * (or the end of the buffer)
582 * If found, change the pattern to 0xFF 0xFE 0x00 0x02
585 for (i = 0; i < dst->size; i++)
596 state = J_DA; /* End of headers - we're done with this image. */
609 if ((c == 0x00) || (c == 0x01))
611 dst->buffer[i] = 2; /* Reset comment block size to 2. */
612 log_error(LOG_LEVEL_INFO, "JPEG comment exploit removed.");
614 * I'm unsure if we can have more than one comment block. Just in case,
615 * we'll scan the rest of the header for more by going back to J_INIT
616 * state. If there is no possibility of >1 comment block, we could
617 * short-circuit to done-ness here.