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authorPierre Ossman <ossman@cendio.se>2019-09-10 15:36:42 +0200
committerPierre Ossman <ossman@cendio.se>2019-11-15 11:20:26 +0100
commitb4ada8d0c6dac98c8b91fc64d112569a8ae5fb95 (patch)
treed3b6ebc4ee5fcceb7ea951d63937f3f2ca17e344 /common
parent9f615301aba1cc54a749950bf9462c5a85217bc4 (diff)
downloadtigervnc-b4ada8d0c6dac98c8b91fc64d112569a8ae5fb95.tar.gz
tigervnc-b4ada8d0c6dac98c8b91fc64d112569a8ae5fb95.zip
Handle empty Tight gradient rects
We always assumed there would be one pixel per row so a rect with a zero width would result in us writing to unknown memory. This could theoretically be used by a malicious server to inject code in to the viewer process. Issue found by Pavel Cheremushkin from Kaspersky Lab.
Diffstat (limited to 'common')
-rw-r--r--common/rfb/tightDecode.h37
1 files changed, 21 insertions, 16 deletions
diff --git a/common/rfb/tightDecode.h b/common/rfb/tightDecode.h
index b6e86ed5..8f77aebd 100644
--- a/common/rfb/tightDecode.h
+++ b/common/rfb/tightDecode.h
@@ -56,15 +56,17 @@ TightDecoder::FilterGradient24(const rdr::U8 *inbuf,
int rectWidth = r.width();
for (y = 0; y < rectHeight; y++) {
- /* First pixel in a row */
- for (c = 0; c < 3; c++) {
- pix[c] = inbuf[y*rectWidth*3+c] + prevRow[c];
- thisRow[c] = pix[c];
- }
- pf.bufferFromRGB((rdr::U8*)&outbuf[y*stride], pix, 1);
+ for (x = 0; x < rectWidth; x++) {
+ /* First pixel in a row */
+ if (x == 0) {
+ for (c = 0; c < 3; c++) {
+ pix[c] = inbuf[y*rectWidth*3+c] + prevRow[c];
+ thisRow[c] = pix[c];
+ }
+ pf.bufferFromRGB((rdr::U8*)&outbuf[y*stride], pix, 1);
+ continue;
+ }
- /* Remaining pixels of a row */
- for (x = 1; x < rectWidth; x++) {
for (c = 0; c < 3; c++) {
est[c] = prevRow[x*3+c] + pix[c] - prevRow[(x-1)*3+c];
if (est[c] > 0xff) {
@@ -103,17 +105,20 @@ void TightDecoder::FilterGradient(const rdr::U8* inbuf,
int rectWidth = r.width();
for (y = 0; y < rectHeight; y++) {
- /* First pixel in a row */
- pf.rgbFromBuffer(pix, &inbuf[y*rectWidth], 1);
- for (c = 0; c < 3; c++)
- pix[c] += prevRow[c];
+ for (x = 0; x < rectWidth; x++) {
+ /* First pixel in a row */
+ if (x == 0) {
+ pf.rgbFromBuffer(pix, &inbuf[y*rectWidth], 1);
+ for (c = 0; c < 3; c++)
+ pix[c] += prevRow[c];
- memcpy(thisRow, pix, sizeof(pix));
+ memcpy(thisRow, pix, sizeof(pix));
- pf.bufferFromRGB((rdr::U8*)&outbuf[y*stride], pix, 1);
+ pf.bufferFromRGB((rdr::U8*)&outbuf[y*stride], pix, 1);
+
+ continue;
+ }
- /* Remaining pixels of a row */
- for (x = 1; x < rectWidth; x++) {
for (c = 0; c < 3; c++) {
est[c] = prevRow[x*3+c] + pix[c] - prevRow[(x-1)*3+c];
if (est[c] > 255) {