Skip to content

fix(psd): avoid signed overflow computing layer/mask extents #5306

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

Open
lgritz wants to merge 1 commit into
base: main
Choose a base branch
from
+28 −16
Open

fix(psd): avoid signed overflow computing layer/mask extents #5306

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
44 changes: 28 additions & 16 deletions src/psd.imageio/psdinput.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -143,7 +143,7 @@ class PSDInput final : public ImageInput {
};

struct Layer {
uint32_t top, left, bottom, right;
int32_t top, left, bottom, right;
uint32_t width, height;
uint16_t channel_count;

Expand All @@ -157,7 +157,7 @@ class PSDInput final : public ImageInput {
uint32_t extra_length;

struct MaskData {
uint32_t top, left, bottom, right;
int32_t top, left, bottom, right;
uint8_t default_color;
uint8_t flags;
};
Expand Down Expand Up @@ -1557,16 +1557,22 @@ bool
PSDInput::load_layer(Layer& layer)
{
bool ok = true;
ok &= read_bige<uint32_t>(layer.top);
ok &= read_bige<uint32_t>(layer.left);
ok &= read_bige<uint32_t>(layer.bottom);
ok &= read_bige<uint32_t>(layer.right);
ok &= read_bige<int32_t>(layer.top);
ok &= read_bige<int32_t>(layer.left);
ok &= read_bige<int32_t>(layer.bottom);
ok &= read_bige<int32_t>(layer.right);
ok &= read_bige<uint16_t>(layer.channel_count);
if (!ok)
return false;

layer.width = std::abs((int)layer.right - (int)layer.left);
layer.height = std::abs((int)layer.bottom - (int)layer.top);
// The rectangle coordinates are signed 32-bit (a layer may have negative
// offsets). Widen to int64 before subtracting: a plain int32 subtraction
// can overflow (undefined behavior) on corrupt files with extreme values.
// The absolute difference of two int32 always fits in uint32.
int64_t w = int64_t(layer.right) - int64_t(layer.left);
int64_t h = int64_t(layer.bottom) - int64_t(layer.top);
layer.width = uint32_t(w < 0 ? -w : w);
layer.height = uint32_t(h < 0 ? -h : h);
if (!validate_resolution("Layer Record", layer.width, layer.height))
return false;
layer.channel_info.resize(layer.channel_count);
Expand Down Expand Up @@ -1608,10 +1614,10 @@ PSDInput::load_layer(Layer& layer)
auto lmd_end = lmd_start + lmd_length;

if (lmd_length >= 4 * 4 + 1 * 2) {
ok &= read_bige<uint32_t>(layer.mask_data.top);
ok &= read_bige<uint32_t>(layer.mask_data.left);
ok &= read_bige<uint32_t>(layer.mask_data.bottom);
ok &= read_bige<uint32_t>(layer.mask_data.right);
ok &= read_bige<int32_t>(layer.mask_data.top);
ok &= read_bige<int32_t>(layer.mask_data.left);
ok &= read_bige<int32_t>(layer.mask_data.bottom);
ok &= read_bige<int32_t>(layer.mask_data.right);
ok &= read_bige<uint8_t>(layer.mask_data.default_color);
ok &= read_bige<uint8_t>(layer.mask_data.flags);
}
Expand Down Expand Up @@ -1694,10 +1700,16 @@ PSDInput::load_layer_channel(Layer& layer, ChannelInfo& channel_info)
// Use mask_data size when channel_id is -2
uint32_t width, height;
if (channel_info.channel_id == ChannelID_LayerMask) {
width = (uint32_t)std::abs((int)layer.mask_data.right
- (int)layer.mask_data.left);
height = (uint32_t)std::abs((int)layer.mask_data.bottom
- (int)layer.mask_data.top);
// Widen to int64 before subtracting: a plain int32 subtraction can
// overflow (undefined behavior) on corrupt files with extreme
// values. The absolute difference of two int32 always fits in
// uint32.
int64_t w = int64_t(layer.mask_data.right)
- int64_t(layer.mask_data.left);
int64_t h = int64_t(layer.mask_data.bottom)
- int64_t(layer.mask_data.top);
width = uint32_t(w < 0 ? -w : w);
height = uint32_t(h < 0 ? -h : h);
} else {
width = layer.width;
height = layer.height;
Expand Down
Loading