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Fix integer wraparound in Buffer bounds checks on 32-bit platforms #193

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Merged
garretrieger merged 1 commit into from
Apr 16, 2026
Merged

Fix integer wraparound in Buffer bounds checks on 32-bit platforms #193

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20 changes: 13 additions & 7 deletions src/buffer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -82,7 +82,7 @@ class Buffer {
}

inline bool ReadU8(uint8_t *value) {
if (offset_ + 1 > length_) {
if (length_ < 1 || offset_ > length_ - 1) {
return FONT_COMPRESSION_FAILURE();
}
*value = buffer_[offset_];
Expand All @@ -91,7 +91,7 @@ class Buffer {
}

bool ReadU16(uint16_t *value) {
if (offset_ + 2 > length_) {
if (length_ < 2 || offset_ > length_ - 2) {
return FONT_COMPRESSION_FAILURE();
}
std::memcpy(value, buffer_ + offset_, sizeof(uint16_t));
Expand All @@ -105,7 +105,7 @@ class Buffer {
}

bool ReadU24(uint32_t *value) {
if (offset_ + 3 > length_) {
if (length_ < 3 || offset_ > length_ - 3) {
return FONT_COMPRESSION_FAILURE();
}
*value = static_cast<uint32_t>(buffer_[offset_]) << 16 |
Expand All @@ -116,7 +116,7 @@ class Buffer {
}

bool ReadU32(uint32_t *value) {
if (offset_ + 4 > length_) {
if (length_ < 4 || offset_ > length_ - 4) {
return FONT_COMPRESSION_FAILURE();
}
std::memcpy(value, buffer_ + offset_, sizeof(uint32_t));
Expand All @@ -130,7 +130,7 @@ class Buffer {
}

bool ReadTag(uint32_t *value) {
if (offset_ + 4 > length_) {
if (length_ < 4 || offset_ > length_ - 4) {
return FONT_COMPRESSION_FAILURE();
}
std::memcpy(value, buffer_ + offset_, sizeof(uint32_t));
Expand All @@ -139,7 +139,7 @@ class Buffer {
}

bool ReadR64(uint64_t *value) {
if (offset_ + 8 > length_) {
if (length_ < 8 || offset_ > length_ - 8) {
return FONT_COMPRESSION_FAILURE();
}
std::memcpy(value, buffer_ + offset_, sizeof(uint64_t));
Expand All @@ -151,7 +151,13 @@ class Buffer {
size_t offset() const { return offset_; }
size_t length() const { return length_; }

void set_offset(size_t newoffset) { offset_ = newoffset; }
bool set_offset(size_t newoffset) {
if (newoffset > length_) {
return FONT_COMPRESSION_FAILURE();
}
offset_ = newoffset;
return true;
}

private:
const uint8_t * const buffer_;
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4 changes: 3 additions & 1 deletion src/font.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -155,7 +155,9 @@ bool ReadTrueTypeCollection(Buffer* file, const uint8_t* data, size_t len,

std::map<uint32_t, Font::Table*> all_tables;
for (const auto offset : offsets) {
file->set_offset(offset);
if (!file->set_offset(offset)) {
return FONT_COMPRESSION_FAILURE();
}
Font& font = *font_it++;
if (!ReadCollectionFont(file, data, len, &font, &all_tables)) {
return FONT_COMPRESSION_FAILURE();
Expand Down