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Prevent potential overflow in rectangle functions

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We're limiting the functions to rects with positions and sizes < 1 billion for speed, which is totally fine for most SDL use cases. If you need rectangles larger than that, you can roll your own functions that use 64-bit intermediate values and do proper overflow handling of output values.

Fixes https://github.com/libsdl-org/SDL/issues/8879
This commit is contained in:
Sam Lantinga 2024-07-21 12:39:45 -07:00
parent 22bfbdbc02
commit bd27b89903
3 changed files with 43 additions and 0 deletions
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2
src/video/SDL_rect.c
View File

@ -91,6 +91,7 @@ SDL_bool SDL_GetSpanEnclosingRect(int width, int height,
#define BIGSCALARTYPE Sint64
#define COMPUTEOUTCODE ComputeOutCode
#define ENCLOSEPOINTS_EPSILON 1
#define SDL_RECT_CAN_OVERFLOW SDL_RectCanOverflow
#define SDL_HASINTERSECTION SDL_HasRectIntersection
#define SDL_INTERSECTRECT SDL_GetRectIntersection
#define SDL_RECTEMPTY SDL_RectEmpty
@ -105,6 +106,7 @@ SDL_bool SDL_GetSpanEnclosingRect(int width, int height,
#define BIGSCALARTYPE double
#define COMPUTEOUTCODE ComputeOutCodeFloat
#define ENCLOSEPOINTS_EPSILON 0.0f
#define SDL_RECT_CAN_OVERFLOW SDL_RectCanOverflowFloat
#define SDL_HASINTERSECTION SDL_HasRectIntersectionFloat
#define SDL_INTERSECTRECT SDL_GetRectIntersectionFloat
#define SDL_RECTEMPTY SDL_RectEmptyFloat

29
src/video/SDL_rect_impl.h
View File

@ -21,6 +21,19 @@
/* This file is #included twice to support int and float versions with the same code. */
static SDL_bool SDL_RECT_CAN_OVERFLOW(const RECTTYPE *rect)
{
if (rect->x <= (SCALARTYPE)(SDL_MIN_SINT32 / 2) ||
rect->x >= (SCALARTYPE)(SDL_MAX_SINT32 / 2) ||
rect->y <= (SCALARTYPE)(SDL_MIN_SINT32 / 2) ||
rect->y >= (SCALARTYPE)(SDL_MAX_SINT32 / 2) ||
rect->w >= (SCALARTYPE)(SDL_MAX_SINT32 / 2) ||
rect->h >= (SCALARTYPE)(SDL_MAX_SINT32 / 2)) {
return SDL_TRUE;
}
return SDL_FALSE;
}
SDL_bool SDL_HASINTERSECTION(const RECTTYPE *A, const RECTTYPE *B)
{
SCALARTYPE Amin, Amax, Bmin, Bmax;
@ -31,6 +44,10 @@ SDL_bool SDL_HASINTERSECTION(const RECTTYPE *A, const RECTTYPE *B)
} else if (!B) {
SDL_InvalidParamError("B");
return SDL_FALSE;
} else if (SDL_RECT_CAN_OVERFLOW(A) ||
SDL_RECT_CAN_OVERFLOW(B)) {
SDL_SetError("Potential rect math overflow");
return SDL_FALSE;
} else if (SDL_RECTEMPTY(A) || SDL_RECTEMPTY(B)) {
return SDL_FALSE; /* Special cases for empty rects */
}
@ -76,6 +93,10 @@ SDL_bool SDL_INTERSECTRECT(const RECTTYPE *A, const RECTTYPE *B, RECTTYPE *resul
} else if (!B) {
SDL_InvalidParamError("B");
return SDL_FALSE;
} else if (SDL_RECT_CAN_OVERFLOW(A) ||
SDL_RECT_CAN_OVERFLOW(B)) {
SDL_SetError("Potential rect math overflow");
return SDL_FALSE;
} else if (!result) {
SDL_InvalidParamError("result");
return SDL_FALSE;
@ -124,6 +145,10 @@ int SDL_UNIONRECT(const RECTTYPE *A, const RECTTYPE *B, RECTTYPE *result)
return SDL_InvalidParamError("A");
} else if (!B) {
return SDL_InvalidParamError("B");
} else if (SDL_RECT_CAN_OVERFLOW(A) ||
SDL_RECT_CAN_OVERFLOW(B)) {
SDL_SetError("Potential rect math overflow");
return SDL_FALSE;
} else if (!result) {
return SDL_InvalidParamError("result");
} else if (SDL_RECTEMPTY(A)) { /* Special cases for empty Rects */
@ -300,6 +325,9 @@ SDL_bool SDL_INTERSECTRECTANDLINE(const RECTTYPE *rect, SCALARTYPE *X1, SCALARTY
if (!rect) {
SDL_InvalidParamError("rect");
return SDL_FALSE;
} else if (SDL_RECT_CAN_OVERFLOW(rect)) {
SDL_SetError("Potential rect math overflow");
return SDL_FALSE;
} else if (!X1) {
SDL_InvalidParamError("X1");
return SDL_FALSE;
@ -430,6 +458,7 @@ SDL_bool SDL_INTERSECTRECTANDLINE(const RECTTYPE *rect, SCALARTYPE *X1, SCALARTY
#undef BIGSCALARTYPE
#undef COMPUTEOUTCODE
#undef ENCLOSEPOINTS_EPSILON
#undef SDL_RECT_CAN_OVERFLOW
#undef SDL_HASINTERSECTION
#undef SDL_INTERSECTRECT
#undef SDL_RECTEMPTY

12
test/testautomation_rect.c
View File

@ -2,6 +2,7 @@
* Original code: automated SDL rect test written by Edgar Simo "bobbens"
* New/updated tests: aschiffler at ferzkopp dot net
*/
#include <limits.h>
#include <SDL3/SDL.h>
#include <SDL3/SDL_test.h>
#include "testautomation_suites.h"
@ -161,6 +162,17 @@ static int rect_testIntersectRectAndLine(void *arg)
intersected = SDL_GetRectAndLineIntersection(&rect, &x1, &y1, &x2, &y2);
validateIntersectRectAndLineResults(intersected, SDL_TRUE, &rect, &refRect, x1, y1, x2, y2, 31, 0, 0, 31);
/* Test some overflow cases */
refRect.x = INT_MAX - 4;
refRect.y = INT_MAX - 4;
x1 = INT_MAX;
y1 = INT_MIN;
x2 = INT_MIN;
y2 = INT_MAX;
rect = refRect;
intersected = SDL_GetRectAndLineIntersection(&rect, &x1, &y1, &x2, &y2);
validateIntersectRectAndLineResults(intersected, SDL_FALSE, &rect, &refRect, x1, y1, x2, y2, x1, y1, x2, y2);
return TEST_COMPLETED;
}