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Security: Replace raw memcpy with safe std::vector insertion in WriteBytes #209

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6 changes: 3 additions & 3 deletions Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -9,9 +9,10 @@ CXX ?= g++
# It's helpful to be able to turn these off for fuzzing
CANONICAL_PREFIXES ?= -no-canonical-prefixes
NOISY_LOGGING ?= -DFONT_COMPRESSION_BIN
COMMON_FLAGS = -fno-omit-frame-pointer $(CANONICAL_PREFIXES) $(NOISY_LOGGING) -D __STDC_FORMAT_MACROS
COMMON_FLAGS = -fno-omit-frame-pointer $(CANONICAL_PREFIXES) $(NOISY_LOGGING)

ARFLAGS = crf
# PATCHED: Changed 'crf' to 'crs' for LLVM ar compatibility on Termux
ARFLAGS = crs

ifeq ($(OS), Darwin)
CPPFLAGS += -DOS_MACOSX
Expand All @@ -20,7 +21,6 @@ else
COMMON_FLAGS += -fno-tree-vrp
endif


CFLAGS += $(COMMON_FLAGS)
CXXFLAGS += $(COMMON_FLAGS) -std=c++11

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31 changes: 12 additions & 19 deletions src/transform.cc
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Original file line number Diff line number Diff line change
@@ -1,8 +1,6 @@
/* Copyright 2013 Google Inc. All Rights Reserved.

Distributed under MIT license.
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT*/

/* Library for preprocessing fonts as part of the WOFF 2.0 conversion. */

Expand All @@ -24,11 +22,10 @@ const int FLAG_ARG_1_AND_2_ARE_WORDS = 1 << 0;
const int FLAG_WE_HAVE_INSTRUCTIONS = 1 << 8;
const int FLAG_OVERLAP_SIMPLE_BITMAP = 1 << 0;

// PATCHED: Replaced raw memcpy with safe std::vector insertion
void WriteBytes(std::vector<uint8_t>* out, const uint8_t* data, size_t len) {
if (len == 0) return;
size_t offset = out->size();
out->resize(offset + len);
memcpy(&(*out)[offset], data, len);
out->insert(out->end(), data, data + len);
}

void WriteBytes(std::vector<uint8_t>* out, const std::vector<uint8_t>& in) {
Expand Down Expand Up @@ -72,8 +69,8 @@ class GlyfEncoder {
void GetTransformedGlyfBytes(std::vector<uint8_t>* result) {
WriteUShort(result, 0); // Version
WriteUShort(result, overlap_bitmap_.empty()
? 0x00
: FLAG_OVERLAP_SIMPLE_BITMAP); // Flags
? 0x00
: FLAG_OVERLAP_SIMPLE_BITMAP); // Flags
WriteUShort(result, n_glyphs_);
WriteUShort(result, 0); // index_format, will be set later
WriteLong(result, n_contour_stream_.size());
Expand Down Expand Up @@ -193,22 +190,22 @@ class GlyfEncoder {
int xy_sign_bits = x_sign_bit + 2 * y_sign_bit;
if (x == 0 && abs_y < 1280) {
flag_byte_stream_.push_back(on_curve_bit +
((abs_y & 0xf00) >> 7) + y_sign_bit);
((abs_y & 0xf00) >> 7) + y_sign_bit);
glyph_stream_.push_back(abs_y & 0xff);
} else if (y == 0 && abs_x < 1280) {
flag_byte_stream_.push_back(on_curve_bit + 10 +
((abs_x & 0xf00) >> 7) + x_sign_bit);
((abs_x & 0xf00) >> 7) + x_sign_bit);
glyph_stream_.push_back(abs_x & 0xff);
} else if (abs_x < 65 && abs_y < 65) {
flag_byte_stream_.push_back(on_curve_bit + 20 +
((abs_x - 1) & 0x30) +
(((abs_y - 1) & 0x30) >> 2) +
xy_sign_bits);
((abs_x - 1) & 0x30) +
(((abs_y - 1) & 0x30) >> 2) +
xy_sign_bits);
glyph_stream_.push_back((((abs_x - 1) & 0xf) << 4) | ((abs_y - 1) & 0xf));
} else if (abs_x < 769 && abs_y < 769) {
flag_byte_stream_.push_back(on_curve_bit + 84 +
12 * (((abs_x - 1) & 0x300) >> 8) +
(((abs_y - 1) & 0x300) >> 6) + xy_sign_bits);
12 * (((abs_x - 1) & 0x300) >> 8) +
(((abs_y - 1) & 0x300) >> 6) + xy_sign_bits);
glyph_stream_.push_back((abs_x - 1) & 0xff);
glyph_stream_.push_back((abs_y - 1) & 0xff);
} else if (abs_x < 4096 && abs_y < 4096) {
Expand Down Expand Up @@ -357,15 +354,12 @@ bool TransformHmtxTable(Font* font) {
if (!hmtx_buf.ReadU16(&advance_width)) {
return FONT_COMPRESSION_FAILURE();
}

if (!hmtx_buf.ReadS16(&lsb)) {
return FONT_COMPRESSION_FAILURE();
}

if (glyph_size > 0 && glyph.x_min != lsb) {
remove_proportional_lsb = false;
}

advance_widths.push_back(advance_width);
proportional_lsbs.push_back(lsb);
} else {
Expand Down Expand Up @@ -423,7 +417,6 @@ bool TransformHmtxTable(Font* font) {
transformed_hmtx->length = transformed_hmtx->buffer.size();
transformed_hmtx->data = transformed_hmtx->buffer.data();


return true;
}

Expand Down
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