| // Copyright (c) 2009 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 "courgette/image_info.h" |
| |
| #include <memory.h> |
| #include <algorithm> |
| #include <map> |
| #include <set> |
| #include <sstream> |
| #include <vector> |
| |
| #include "base/logging.h" |
| |
| namespace courgette { |
| |
| std::string SectionName(const Section* section) { |
| if (section == NULL) |
| return "<none>"; |
| char name[9]; |
| memcpy(name, section->name, 8); |
| name[8] = '\0'; // Ensure termination. |
| return name; |
| } |
| |
| PEInfo::PEInfo() |
| : failure_reason_("uninitialized"), |
| start_(0), end_(0), length_(0), |
| is_PE32_plus_(0), file_length_(0), has_text_section_(false) { |
| } |
| |
| void PEInfo::Init(const void* start, size_t length) { |
| start_ = reinterpret_cast<const uint8*>(start); |
| length_ = length; |
| end_ = start_ + length_; |
| failure_reason_ = "unparsed"; |
| } |
| |
| // DescribeRVA is for debugging only. I would put it under #ifdef DEBUG except |
| // that during development I'm finding I need to call it when compiled in |
| // Release mode. Hence: |
| // TODO(sra): make this compile only for debug mode. |
| std::string PEInfo::DescribeRVA(RVA rva) const { |
| const Section* section = RVAToSection(rva); |
| std::ostringstream s; |
| s << std::hex << rva; |
| if (section) { |
| s << " ("; |
| s << SectionName(section) << "+" |
| << std::hex << (rva - section->virtual_address) |
| << ")"; |
| } |
| return s.str(); |
| } |
| |
| const Section* PEInfo::FindNextSection(uint32 fileOffset) const { |
| const Section* best = 0; |
| for (int i = 0; i < number_of_sections_; i++) { |
| const Section* section = §ions_[i]; |
| if (section->size_of_raw_data > 0) { // i.e. has data in file. |
| if (fileOffset <= section->file_offset_of_raw_data) { |
| if (best == 0 || |
| section->file_offset_of_raw_data < best->file_offset_of_raw_data) { |
| best = section; |
| } |
| } |
| } |
| } |
| return best; |
| } |
| |
| const Section* PEInfo::RVAToSection(RVA rva) const { |
| for (int i = 0; i < number_of_sections_; i++) { |
| const Section* section = §ions_[i]; |
| uint32 offset = rva - section->virtual_address; |
| if (offset < section->virtual_size) { |
| return section; |
| } |
| } |
| return NULL; |
| } |
| |
| int PEInfo::RVAToFileOffset(RVA rva) const { |
| const Section* section = RVAToSection(rva); |
| if (section) { |
| uint32 offset = rva - section->virtual_address; |
| if (offset < section->size_of_raw_data) { |
| return section->file_offset_of_raw_data + offset; |
| } else { |
| return kNoOffset; // In section but not in file (e.g. uninit data). |
| } |
| } |
| |
| // Small RVA values point into the file header in the loaded image. |
| // RVA 0 is the module load address which Windows uses as the module handle. |
| // RVA 2 sometimes occurs, I'm not sure what it is, but it would map into the |
| // DOS header. |
| if (rva == 0 || rva == 2) |
| return rva; |
| |
| NOTREACHED(); |
| return kNoOffset; |
| } |
| |
| const uint8* PEInfo::RVAToPointer(RVA rva) const { |
| int file_offset = RVAToFileOffset(rva); |
| if (file_offset == kNoOffset) |
| return NULL; |
| else |
| return start_ + file_offset; |
| } |
| |
| RVA PEInfo::FileOffsetToRVA(uint32 file_offset) const { |
| for (int i = 0; i < number_of_sections_; i++) { |
| const Section* section = §ions_[i]; |
| uint32 offset = file_offset - section->file_offset_of_raw_data; |
| if (offset < section->size_of_raw_data) { |
| return section->virtual_address + offset; |
| } |
| } |
| return 0; |
| } |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| namespace { |
| |
| // Constants and offsets gleaned from WINNT.H and various articles on the |
| // format of Windows PE executables. |
| |
| // This is FIELD_OFFSET(IMAGE_DOS_HEADER, e_lfanew): |
| const size_t kOffsetOfFileAddressOfNewExeHeader = 0x3c; |
| |
| const uint16 kImageNtOptionalHdr32Magic = 0x10b; |
| const uint16 kImageNtOptionalHdr64Magic = 0x20b; |
| |
| const size_t kSizeOfCoffHeader = 20; |
| const size_t kOffsetOfDataDirectoryFromImageOptionalHeader32 = 96; |
| const size_t kOffsetOfDataDirectoryFromImageOptionalHeader64 = 112; |
| |
| // These helper functions avoid the need for casts in the main code. |
| inline uint16 ReadU16(const uint8* address, size_t offset) { |
| return *reinterpret_cast<const uint16*>(address + offset); |
| } |
| |
| inline uint32 ReadU32(const uint8* address, size_t offset) { |
| return *reinterpret_cast<const uint32*>(address + offset); |
| } |
| |
| inline uint64 ReadU64(const uint8* address, size_t offset) { |
| return *reinterpret_cast<const uint64*>(address + offset); |
| } |
| |
| } // namespace |
| |
| // ParseHeader attempts to match up the buffer with the Windows data |
| // structures that exist within a Windows 'Portable Executable' format file. |
| // Returns 'true' if the buffer matches, and 'false' if the data looks |
| // suspicious. Rather than try to 'map' the buffer to the numerous windows |
| // structures, we extract the information we need into the courgette::PEInfo |
| // structure. |
| // |
| bool PEInfo::ParseHeader() { |
| if (length_ < kOffsetOfFileAddressOfNewExeHeader + 4 /*size*/) |
| return Bad("Too small"); |
| |
| // Have 'MZ' magic for a DOS header? |
| if (start_[0] != 'M' || start_[1] != 'Z') |
| return Bad("Not MZ"); |
| |
| // offset from DOS header to PE header is stored in DOS header. |
| uint32 offset = ReadU32(start_, kOffsetOfFileAddressOfNewExeHeader); |
| |
| const uint8* const pe_header = start_ + offset; |
| const size_t kMinPEHeaderSize = 4 /*signature*/ + kSizeOfCoffHeader; |
| if (pe_header <= start_ || pe_header >= end_ - kMinPEHeaderSize) |
| return Bad("Bad offset to PE header"); |
| |
| if (offset % 8 != 0) |
| return Bad("Misaligned PE header"); |
| |
| // The 'PE' header is an IMAGE_NT_HEADERS structure as defined in WINNT.H. |
| // See http://msdn.microsoft.com/en-us/library/ms680336(VS.85).aspx |
| // |
| // The first field of the IMAGE_NT_HEADERS is the signature. |
| if (!(pe_header[0] == 'P' && |
| pe_header[1] == 'E' && |
| pe_header[2] == 0 && |
| pe_header[3] == 0)) |
| return Bad("no PE signature"); |
| |
| // The second field of the IMAGE_NT_HEADERS is the COFF header. |
| // The COFF header is also called an IMAGE_FILE_HEADER |
| // http://msdn.microsoft.com/en-us/library/ms680313(VS.85).aspx |
| const uint8* const coff_header = pe_header + 4; |
| machine_type_ = ReadU16(coff_header, 0); |
| number_of_sections_ = ReadU16(coff_header, 2); |
| size_of_optional_header_ = ReadU16(coff_header, 16); |
| |
| // The rest of the IMAGE_NT_HEADERS is the IMAGE_OPTIONAL_HEADER(32|64) |
| const uint8* const optional_header = coff_header + kSizeOfCoffHeader; |
| optional_header_ = optional_header; |
| |
| if (optional_header + size_of_optional_header_ >= end_) |
| return Bad("optional header past end of file"); |
| |
| // Check we can read the magic. |
| if (size_of_optional_header_ < 2) |
| return Bad("optional header no magic"); |
| |
| uint16 magic = ReadU16(optional_header, 0); |
| |
| if (magic == kImageNtOptionalHdr32Magic) { |
| is_PE32_plus_ = false; |
| offset_of_data_directories_ = |
| kOffsetOfDataDirectoryFromImageOptionalHeader32; |
| } else if (magic == kImageNtOptionalHdr64Magic) { |
| is_PE32_plus_ = true; |
| offset_of_data_directories_ = |
| kOffsetOfDataDirectoryFromImageOptionalHeader64; |
| } else { |
| return Bad("unrecognized magic"); |
| } |
| |
| // Check that we can read the rest of the the fixed fields. Data directories |
| // directly follow the fixed fields of the IMAGE_OPTIONAL_HEADER. |
| if (size_of_optional_header_ < offset_of_data_directories_) |
| return Bad("optional header too short"); |
| |
| // The optional header is either an IMAGE_OPTIONAL_HEADER32 or |
| // IMAGE_OPTIONAL_HEADER64 |
| // http://msdn.microsoft.com/en-us/library/ms680339(VS.85).aspx |
| // |
| // Copy the fields we care about. |
| size_of_code_ = ReadU32(optional_header, 4); |
| size_of_initialized_data_ = ReadU32(optional_header, 8); |
| size_of_uninitialized_data_ = ReadU32(optional_header, 12); |
| base_of_code_ = ReadU32(optional_header, 20); |
| if (is_PE32_plus_) { |
| base_of_data_ = 0; |
| image_base_ = ReadU64(optional_header, 24); |
| } else { |
| base_of_data_ = ReadU32(optional_header, 24); |
| image_base_ = ReadU32(optional_header, 28); |
| } |
| size_of_image_ = ReadU32(optional_header, 56); |
| number_of_data_directories_ = |
| ReadU32(optional_header, (is_PE32_plus_ ? 108 : 92)); |
| |
| if (size_of_code_ >= length_ || |
| size_of_initialized_data_ >= length_ || |
| size_of_code_ + size_of_initialized_data_ >= length_) { |
| // This validation fires on some perfectly fine executables. |
| // return Bad("code or initialized data too big"); |
| } |
| |
| // TODO(sra): we can probably get rid of most of the data directories. |
| bool b = true; |
| // 'b &= ...' could be short circuit 'b = b && ...' but it is not necessary |
| // for correctness and it compiles smaller this way. |
| b &= ReadDataDirectory(0, &export_table_); |
| b &= ReadDataDirectory(1, &import_table_); |
| b &= ReadDataDirectory(2, &resource_table_); |
| b &= ReadDataDirectory(3, &exception_table_); |
| b &= ReadDataDirectory(5, &base_relocation_table_); |
| b &= ReadDataDirectory(11, &bound_import_table_); |
| b &= ReadDataDirectory(12, &import_address_table_); |
| b &= ReadDataDirectory(13, &delay_import_descriptor_); |
| b &= ReadDataDirectory(14, &clr_runtime_header_); |
| if (!b) { |
| return Bad("malformed data directory"); |
| } |
| |
| // Sections follow the optional header. |
| sections_ = |
| reinterpret_cast<const Section*>(optional_header + |
| size_of_optional_header_); |
| file_length_ = 0; |
| |
| for (int i = 0; i < number_of_sections_; ++i) { |
| const Section* section = §ions_[i]; |
| |
| // TODO(sra): consider using the 'characteristics' field of the section |
| // header to see if the section contains instructions. |
| if (memcmp(section->name, ".text", 6) == 0) |
| has_text_section_ = true; |
| |
| uint32 section_end = |
| section->file_offset_of_raw_data + section->size_of_raw_data; |
| if (section_end > file_length_) |
| file_length_ = section_end; |
| } |
| |
| failure_reason_ = NULL; |
| return true; |
| } |
| |
| bool PEInfo::ReadDataDirectory(int index, ImageDataDirectory* directory) { |
| if (index < number_of_data_directories_) { |
| size_t offset = index * 8 + offset_of_data_directories_; |
| if (offset >= size_of_optional_header_) |
| return Bad("number of data directories inconsistent"); |
| const uint8* data_directory = optional_header_ + offset; |
| if (data_directory < start_ || data_directory + 8 >= end_) |
| return Bad("data directory outside image"); |
| RVA rva = ReadU32(data_directory, 0); |
| size_t size = ReadU32(data_directory, 4); |
| if (size > size_of_image_) |
| return Bad("data directory size too big"); |
| |
| // TODO(sra): validate RVA. |
| directory->address_ = rva; |
| directory->size_ = size; |
| return true; |
| } else { |
| directory->address_ = 0; |
| directory->size_ = 0; |
| return true; |
| } |
| } |
| |
| bool PEInfo::Bad(const char* reason) { |
| failure_reason_ = reason; |
| return false; |
| } |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| bool PEInfo::ParseRelocs(std::vector<RVA> *relocs) { |
| relocs->clear(); |
| |
| size_t relocs_size = base_relocation_table_.size_; |
| if (relocs_size == 0) |
| return true; |
| |
| // The format of the base relocation table is a sequence of variable sized |
| // IMAGE_BASE_RELOCATION blocks. Search for |
| // "The format of the base relocation data is somewhat quirky" |
| // at http://msdn.microsoft.com/en-us/library/ms809762.aspx |
| |
| const uint8* start = RVAToPointer(base_relocation_table_.address_); |
| const uint8* end = start + relocs_size; |
| |
| // Make sure entire base relocation table is within the buffer. |
| if (start < start_ || |
| start >= end_ || |
| end <= start_ || |
| end > end_) { |
| return Bad(".relocs outside image"); |
| } |
| |
| const uint8* block = start; |
| |
| // Walk the variable sized blocks. |
| while (block + 8 < end) { |
| RVA page_rva = ReadU32(block, 0); |
| uint32 size = ReadU32(block, 4); |
| if (size < 8 || // Size includes header ... |
| size % 4 != 0) // ... and is word aligned. |
| return Bad("unreasonable relocs block"); |
| |
| const uint8* end_entries = block + size; |
| |
| if (end_entries <= block || end_entries <= start_ || end_entries > end_) |
| return Bad(".relocs block outside image"); |
| |
| // Walk through the two-byte entries. |
| for (const uint8* p = block + 8; p < end_entries; p += 2) { |
| uint16 entry = ReadU16(p, 0); |
| int type = entry >> 12; |
| int offset = entry & 0xFFF; |
| |
| RVA rva = page_rva + offset; |
| if (type == 3) { // IMAGE_REL_BASED_HIGHLOW |
| relocs->push_back(rva); |
| } else if (type == 0) { // IMAGE_REL_BASED_ABSOLUTE |
| // Ignore, used as padding. |
| } else { |
| // Does not occur in Windows x86 executables. |
| return Bad("unknown type of reloc"); |
| } |
| } |
| |
| block += size; |
| } |
| |
| std::sort(relocs->begin(), relocs->end()); |
| |
| return true; |
| } |
| |
| } // namespace courgette |