Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Prevent overflow in chromaticity calculations #588

Closed
wants to merge 1 commit into from
Closed

Prevent overflow in chromaticity calculations #588

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
71 changes: 46 additions & 25 deletions png.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1203,6 +1203,24 @@ png_colorspace_sync(png_const_structrp png_ptr, png_inforp info_ptr)
#endif /* GAMMA */

#ifdef PNG_COLORSPACE_SUPPORTED
static int
png_safe_add(png_int_32 *addend0_and_result, png_int_32 addend1,
png_int_32 addend2) {
/* Safely add three integers. Returns 0 on success, 1 on overlow.
* IMPLEMENTATION NOTE: ANSI requires signed overflow not to occur, therefore
* relying on addition of two positive values producing a negative one is not
* safe.
*/
int addend0 = *addend0_and_result;
if (0x7fffffff - addend0 < addend1)
return 1;
addend0 += addend1;
if (0x7fffffff - addend1 < addend2)
return 1;
*addend0_and_result = addend0 + addend2;
return 0;
}

/* Added at libpng-1.5.5 to support read and write of true CIEXYZ values for
* cHRM, as opposed to using chromaticities. These internal APIs return
* non-zero on a parameter error. The X, Y and Z values are required to be
Expand All @@ -1211,38 +1229,52 @@ png_colorspace_sync(png_const_structrp png_ptr, png_inforp info_ptr)
static int
png_xy_from_XYZ(png_xy *xy, const png_XYZ *XYZ)
{
png_int_32 d, dwhite, whiteX, whiteY;
png_int_32 d, dred, dgreen, dwhite, whiteX, whiteY;

d = XYZ->red_X + XYZ->red_Y + XYZ->red_Z;
/* 'd' in each of the blocks below is just X+Y+Z for each component,
* x, y and z are X,Y,Z/(X+Y+Z).
*/
d = XYZ->red_X;
if (png_safe_add(&d, XYZ->red_Y, XYZ->red_Z))
return 1;
if (png_muldiv(&xy->redx, XYZ->red_X, PNG_FP_1, d) == 0)
return 1;
if (png_muldiv(&xy->redy, XYZ->red_Y, PNG_FP_1, d) == 0)
return 1;
dwhite = d;
dred = d;
whiteX = XYZ->red_X;
whiteY = XYZ->red_Y;

d = XYZ->green_X + XYZ->green_Y + XYZ->green_Z;
d = XYZ->green_X;
if (png_safe_add(&d, XYZ->green_Y, XYZ->green_Z))
return 1;
if (png_muldiv(&xy->greenx, XYZ->green_X, PNG_FP_1, d) == 0)
return 1;
if (png_muldiv(&xy->greeny, XYZ->green_Y, PNG_FP_1, d) == 0)
return 1;
dwhite += d;
dgreen = d;
whiteX += XYZ->green_X;
whiteY += XYZ->green_Y;

d = XYZ->blue_X + XYZ->blue_Y + XYZ->blue_Z;
d = XYZ->blue_X;
if (png_safe_add(&d, XYZ->blue_Y, XYZ->blue_Z))
return 1;
if (png_muldiv(&xy->bluex, XYZ->blue_X, PNG_FP_1, d) == 0)
return 1;
if (png_muldiv(&xy->bluey, XYZ->blue_Y, PNG_FP_1, d) == 0)
return 1;
dwhite += d;
whiteX += XYZ->blue_X;
whiteY += XYZ->blue_Y;

/* The reference white is simply the sum of the end-point (X,Y,Z) vectors,
* thus:
/* The reference white is simply the sum of the end-point (X,Y,Z) vectors so
* the fillowing calculates (X+Y+Z) of the reference white (media white,
* encoding white) itself:
*/
if (png_safe_add(&d, dred, dgreen))
return 1;

dwhite = d;

if (png_muldiv(&xy->whitex, whiteX, PNG_FP_1, dwhite) == 0)
return 1;
if (png_muldiv(&xy->whitey, whiteY, PNG_FP_1, dwhite) == 0)
Expand Down Expand Up @@ -1506,25 +1538,14 @@ png_XYZ_from_xy(png_XYZ *XYZ, const png_xy *xy)
static int
png_XYZ_normalize(png_XYZ *XYZ)
{
png_int_32 Y;
png_int_32 Y, Ytemp;

if (XYZ->red_Y < 0 || XYZ->green_Y < 0 || XYZ->blue_Y < 0 ||
XYZ->red_X < 0 || XYZ->green_X < 0 || XYZ->blue_X < 0 ||
XYZ->red_Z < 0 || XYZ->green_Z < 0 || XYZ->blue_Z < 0)
/* Normalize by scaling so the sum of the end-point Y values is PNG_FP_1. */
Ytemp = XYZ->red_Y;
if (png_safe_add(&Ytemp, XYZ->green_Y, XYZ->blue_Y))
return 1;

/* Normalize by scaling so the sum of the end-point Y values is PNG_FP_1.
* IMPLEMENTATION NOTE: ANSI requires signed overflow not to occur, therefore
* relying on addition of two positive values producing a negative one is not
* safe.
*/
Y = XYZ->red_Y;
if (0x7fffffff - Y < XYZ->green_X)
return 1;
Y += XYZ->green_Y;
if (0x7fffffff - Y < XYZ->blue_X)
return 1;
Y += XYZ->blue_Y;
Y = Ytemp;

if (Y != PNG_FP_1)
{
Expand Down