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164 lines
6.8 KiB
164 lines
6.8 KiB
From e1cd2d7ab032e7fe80b4c13e07895194c8bac85e Mon Sep 17 00:00:00 2001
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From: Brian May <brian@linuxpenguins.xyz>
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Date: Thu, 7 Dec 2017 07:46:47 +1100
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Subject: [PATCH 1/4] [PATCH] tiff2pdf: Fix CVE-2017-9935
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Fix for http://bugzilla.maptools.org/show_bug.cgi?id=2704
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This vulnerability - at least for the supplied test case - is because we
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assume that a tiff will only have one transfer function that is the same
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for all pages. This is not required by the TIFF standards.
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We than read the transfer function for every page. Depending on the
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transfer function, we allocate either 2 or 4 bytes to the XREF buffer.
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We allocate this memory after we read in the transfer function for the
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page.
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For the first exploit - POC1, this file has 3 pages. For the first page
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we allocate 2 extra extra XREF entries. Then for the next page 2 more
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entries. Then for the last page the transfer function changes and we
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allocate 4 more entries.
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When we read the file into memory, we assume we have 4 bytes extra for
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each and every page (as per the last transfer function we read). Which
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is not correct, we only have 2 bytes extra for the first 2 pages. As a
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result, we end up writing past the end of the buffer.
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There are also some related issues that this also fixes. For example,
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TIFFGetField can return uninitalized pointer values, and the logic to
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detect a N=3 vs N=1 transfer function seemed rather strange.
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It is also strange that we declare the transfer functions to be of type
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float, when the standard says they are unsigned 16 bit values. This is
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fixed in another patch.
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This patch will check to ensure that the N value for every transfer
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function is the same for every page. If this changes, we abort with an
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error. In theory, we should perhaps check that the transfer function
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itself is identical for every page, however we don't do that due to the
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confusion of the type of the data in the transfer function.
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---
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libtiff/tif_dir.c | 3 +++
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tools/tiff2pdf.c | 69 +++++++++++++++++++++++++++++++----------------
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2 files changed, 49 insertions(+), 23 deletions(-)
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diff --git a/libtiff/tif_dir.c b/libtiff/tif_dir.c
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index f00f808..c36a5f3 100644
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--- a/libtiff/tif_dir.c
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+++ b/libtiff/tif_dir.c
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@@ -1067,6 +1067,9 @@ _TIFFVGetField(TIFF* tif, uint32 tag, va_list ap)
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if (td->td_samplesperpixel - td->td_extrasamples > 1) {
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*va_arg(ap, uint16**) = td->td_transferfunction[1];
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*va_arg(ap, uint16**) = td->td_transferfunction[2];
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+ } else {
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+ *va_arg(ap, uint16**) = NULL;
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+ *va_arg(ap, uint16**) = NULL;
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}
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break;
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case TIFFTAG_REFERENCEBLACKWHITE:
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diff --git a/tools/tiff2pdf.c b/tools/tiff2pdf.c
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index bdb9126..bd23c9e 100644
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--- a/tools/tiff2pdf.c
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+++ b/tools/tiff2pdf.c
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@@ -239,7 +239,7 @@ typedef struct {
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float tiff_whitechromaticities[2];
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float tiff_primarychromaticities[6];
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float tiff_referenceblackwhite[2];
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- float* tiff_transferfunction[3];
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+ uint16* tiff_transferfunction[3];
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int pdf_image_interpolate; /* 0 (default) : do not interpolate,
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1 : interpolate */
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uint16 tiff_transferfunctioncount;
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@@ -1049,6 +1049,8 @@ void t2p_read_tiff_init(T2P* t2p, TIFF* input){
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uint16 pagen=0;
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uint16 paged=0;
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uint16 xuint16=0;
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+ uint16 tiff_transferfunctioncount=0;
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+ uint16* tiff_transferfunction[3];
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directorycount=TIFFNumberOfDirectories(input);
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if(directorycount > TIFF_DIR_MAX) {
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@@ -1157,26 +1159,48 @@ void t2p_read_tiff_init(T2P* t2p, TIFF* input){
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}
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#endif
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if (TIFFGetField(input, TIFFTAG_TRANSFERFUNCTION,
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- &(t2p->tiff_transferfunction[0]),
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- &(t2p->tiff_transferfunction[1]),
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- &(t2p->tiff_transferfunction[2]))) {
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- if((t2p->tiff_transferfunction[1] != (float*) NULL) &&
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- (t2p->tiff_transferfunction[2] != (float*) NULL) &&
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- (t2p->tiff_transferfunction[1] !=
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- t2p->tiff_transferfunction[0])) {
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- t2p->tiff_transferfunctioncount = 3;
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- t2p->tiff_pages[i].page_extra += 4;
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- t2p->pdf_xrefcount += 4;
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- } else {
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- t2p->tiff_transferfunctioncount = 1;
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- t2p->tiff_pages[i].page_extra += 2;
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- t2p->pdf_xrefcount += 2;
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- }
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- if(t2p->pdf_minorversion < 2)
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- t2p->pdf_minorversion = 2;
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+ &(tiff_transferfunction[0]),
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+ &(tiff_transferfunction[1]),
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+ &(tiff_transferfunction[2]))) {
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+
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+ if((tiff_transferfunction[1] != (uint16*) NULL) &&
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+ (tiff_transferfunction[2] != (uint16*) NULL)
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+ ) {
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+ tiff_transferfunctioncount=3;
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+ } else {
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+ tiff_transferfunctioncount=1;
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+ }
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} else {
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- t2p->tiff_transferfunctioncount=0;
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+ tiff_transferfunctioncount=0;
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}
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+
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+ if (i > 0){
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+ if (tiff_transferfunctioncount != t2p->tiff_transferfunctioncount){
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+ TIFFError(
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+ TIFF2PDF_MODULE,
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+ "Different transfer function on page %d",
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+ i);
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+ t2p->t2p_error = T2P_ERR_ERROR;
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+ return;
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+ }
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+ }
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+
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+ t2p->tiff_transferfunctioncount = tiff_transferfunctioncount;
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+ t2p->tiff_transferfunction[0] = tiff_transferfunction[0];
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+ t2p->tiff_transferfunction[1] = tiff_transferfunction[1];
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+ t2p->tiff_transferfunction[2] = tiff_transferfunction[2];
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+ if(tiff_transferfunctioncount == 3){
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+ t2p->tiff_pages[i].page_extra += 4;
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+ t2p->pdf_xrefcount += 4;
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+ if(t2p->pdf_minorversion < 2)
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+ t2p->pdf_minorversion = 2;
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+ } else if (tiff_transferfunctioncount == 1){
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+ t2p->tiff_pages[i].page_extra += 2;
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+ t2p->pdf_xrefcount += 2;
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+ if(t2p->pdf_minorversion < 2)
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+ t2p->pdf_minorversion = 2;
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+ }
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+
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if( TIFFGetField(
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input,
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TIFFTAG_ICCPROFILE,
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@@ -1837,10 +1861,9 @@ void t2p_read_tiff_data(T2P* t2p, TIFF* input){
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&(t2p->tiff_transferfunction[0]),
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&(t2p->tiff_transferfunction[1]),
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&(t2p->tiff_transferfunction[2]))) {
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- if((t2p->tiff_transferfunction[1] != (float*) NULL) &&
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- (t2p->tiff_transferfunction[2] != (float*) NULL) &&
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- (t2p->tiff_transferfunction[1] !=
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- t2p->tiff_transferfunction[0])) {
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+ if((t2p->tiff_transferfunction[1] != (uint16*) NULL) &&
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+ (t2p->tiff_transferfunction[2] != (uint16*) NULL)
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+ ) {
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t2p->tiff_transferfunctioncount=3;
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} else {
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t2p->tiff_transferfunctioncount=1;
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--
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2.17.0
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