// Copyright 2017 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #include "pdf/font_table_linux.h" #include #include #include #include #include #include "base/numerics/safe_conversions.h" #include "base/posix/eintr_wrapper.h" #include "base/sys_byteorder.h" namespace pdf { // TODO(drott): This should be should be replaced with using FreeType for the // purpose instead of reimplementing table parsing. bool GetFontTable(int fd, uint32_t table_tag, off_t offset, uint8_t* output, size_t* output_length) { if (offset < 0) return false; size_t data_length = 0; // the length of the file data. off_t data_offset = 0; // the offset of the data in the file. if (table_tag == 0) { // Get the entire font file. struct stat st; if (fstat(fd, &st) < 0) return false; data_length = base::checked_cast(st.st_size); } else { // Get a font table. Read the header to find its offset in the file. uint16_t num_tables; ssize_t n = HANDLE_EINTR( pread(fd, &num_tables, sizeof(num_tables), 4 /* skip the font type */)); if (n != sizeof(num_tables)) return false; // Font data is stored in net (big-endian) order. num_tables = base::NetToHost16(num_tables); // Read the table directory. static const size_t kTableEntrySize = 16; const size_t directory_size = num_tables * kTableEntrySize; std::unique_ptr table_entries(new uint8_t[directory_size]); n = HANDLE_EINTR(pread(fd, table_entries.get(), directory_size, 12 /* skip the SFNT header */)); if (n != base::checked_cast(directory_size)) return false; for (uint16_t i = 0; i < num_tables; ++i) { uint8_t* entry = table_entries.get() + i * kTableEntrySize; uint32_t tag = *reinterpret_cast(entry); if (tag == table_tag) { // Font data is stored in net (big-endian) order. data_offset = base::NetToHost32(*reinterpret_cast(entry + 8)); data_length = base::NetToHost32(*reinterpret_cast(entry + 12)); break; } } } if (!data_length) return false; // Clamp |offset| inside the allowable range. This allows the read to succeed // but return 0 bytes. offset = std::min(offset, base::checked_cast(data_length)); // Make sure it's safe to add the data offset and the caller's logical offset. // Define the maximum positive offset on 32 bit systems. static const off_t kMaxPositiveOffset32 = 0x7FFFFFFF; // 2 GB - 1. if ((offset > kMaxPositiveOffset32 / 2) || (data_offset > kMaxPositiveOffset32 / 2)) return false; data_offset += offset; data_length -= offset; if (output) { // 'output_length' holds the maximum amount of data the caller can accept. data_length = std::min(data_length, *output_length); ssize_t n = HANDLE_EINTR(pread(fd, output, data_length, data_offset)); if (n != base::checked_cast(data_length)) return false; } *output_length = data_length; return true; } } // namespace pdf