Move Courgette...

courgette/image_info.cc

+// 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 = &sections_[i];
+    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 = &sections_[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 = &sections_[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 = &sections_[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