The Tor Browser / file revision

 // Copyright (c) 2010, Google Inc.

 // All rights reserved.

 //

 // Redistribution and use in source and binary forms, with or without

 // modification, are permitted provided that the following conditions are

 // met:

 //

 //     * Redistributions of source code must retain the above copyright

 // notice, this list of conditions and the following disclaimer.

 //     * Redistributions in binary form must reproduce the above

 // copyright notice, this list of conditions and the following disclaimer

 // in the documentation and/or other materials provided with the

 // distribution.

 //     * Neither the name of Google Inc. nor the names of its

 // contributors may be used to endorse or promote products derived from

 // this software without specific prior written permission.

 //

 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 // Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>

 // macho_reader.cc: Implementation of google_breakpad::Mach_O::FatReader and

 // google_breakpad::Mach_O::Reader. See macho_reader.h for details.

 #include "common/mac/macho_reader.h"

 #include <assert.h>

 #include <stdio.h>

 #include <stdlib.h>

 // Unfortunately, CPU_TYPE_ARM is not define for 10.4.

 #if !defined(CPU_TYPE_ARM)

 #define CPU_TYPE_ARM 12

 #endif

 namespace google_breakpad {

 namespace mach_o {

 // If NDEBUG is #defined, then the 'assert' macro doesn't evaluate its

 // arguments, so you can't place expressions that do necessary work in

 // the argument of an assert. Nor can you assign the result of the

 // expression to a variable and assert that the variable's value is

 // true: you'll get unused variable warnings when NDEBUG is #defined.

 //

 // ASSERT_ALWAYS_EVAL always evaluates its argument, and asserts that

 // the result is true if NDEBUG is not #defined.

 #if defined(NDEBUG)

 #define ASSERT_ALWAYS_EVAL(x) (x)

 #else

 #define ASSERT_ALWAYS_EVAL(x) assert(x)

 #endif

 void FatReader::Reporter::BadHeader() {

   fprintf(stderr, "%s: file is neither a fat binary file"

           " nor a Mach-O object file\n", filename_.c_str());

 }

 void FatReader::Reporter::TooShort() {

   fprintf(stderr, "%s: file too short for the data it claims to contain\n",

           filename_.c_str());

 }

 void FatReader::Reporter::MisplacedObjectFile() {

   fprintf(stderr, "%s: file too short for the object files it claims"

           " to contain\n", filename_.c_str());

 }

 bool FatReader::Read(const uint8_t *buffer, size_t size) {

   buffer_.start = buffer;

   buffer_.end = buffer + size;

   ByteCursor cursor(&buffer_);

   // Fat binaries always use big-endian, so read the magic number in

   // that endianness. To recognize Mach-O magic numbers, which can use

   // either endianness, check for both the proper and reversed forms

   // of the magic numbers.

   cursor.set_big_endian(true);

   if (cursor >> magic_) {

     if (magic_ == FAT_MAGIC) {

       // How many object files does this fat binary contain?

       uint32_t object_files_count;

       if (!(cursor >> object_files_count)) {  // nfat_arch

         reporter_->TooShort();

         return false;

       }

       // Read the list of object files.

       object_files_.resize(object_files_count);

       for (size_t i = 0; i < object_files_count; i++) {

         struct fat_arch *objfile = &object_files_[i];

         // Read this object file entry, byte-swapping as appropriate.

         cursor >> objfile->cputype

                >> objfile->cpusubtype

                >> objfile->offset

                >> objfile->size

                >> objfile->align;

         if (!cursor) {

           reporter_->TooShort();

           return false;

         }

         // Does the file actually have the bytes this entry refers to?

         size_t fat_size = buffer_.Size();

         if (objfile->offset > fat_size ||

             objfile->size > fat_size - objfile->offset) {

           reporter_->MisplacedObjectFile();

           return false;

         }

       }

       return true;

     } else if (magic_ == MH_MAGIC || magic_ == MH_MAGIC_64 ||

                magic_ == MH_CIGAM || magic_ == MH_CIGAM_64) {

       // If this is a little-endian Mach-O file, fix the cursor's endianness.

       if (magic_ == MH_CIGAM || magic_ == MH_CIGAM_64)

         cursor.set_big_endian(false);

       // Record the entire file as a single entry in the object file list.

       object_files_.resize(1);

       // Get the cpu type and subtype from the Mach-O header.

       if (!(cursor >> object_files_[0].cputype

                    >> object_files_[0].cpusubtype)) {

         reporter_->TooShort();

         return false;

       }

       object_files_[0].offset = 0;

       object_files_[0].size = static_cast<uint32_t>(buffer_.Size());

       // This alignment is correct for 32 and 64-bit x86 and ppc.

       // See get_align in the lipo source for other architectures:

       // http://www.opensource.apple.com/source/cctools/cctools-773/misc/lipo.c

       object_files_[0].align = 12;  // 2^12 == 4096

       return true;

     }

   }

   reporter_->BadHeader();

   return false;

 }

 void Reader::Reporter::BadHeader() {

   fprintf(stderr, "%s: file is not a Mach-O object file\n", filename_.c_str());

 }

 void Reader::Reporter::CPUTypeMismatch(cpu_type_t cpu_type,

                                        cpu_subtype_t cpu_subtype,

                                        cpu_type_t expected_cpu_type,

                                        cpu_subtype_t expected_cpu_subtype) {

   fprintf(stderr, "%s: CPU type %d, subtype %d does not match expected"

           " type %d, subtype %d\n",

           filename_.c_str(), cpu_type, cpu_subtype,

           expected_cpu_type, expected_cpu_subtype);

 }

 void Reader::Reporter::HeaderTruncated() {

   fprintf(stderr, "%s: file does not contain a complete Mach-O header\n",

           filename_.c_str());

 }

 void Reader::Reporter::LoadCommandRegionTruncated() {

   fprintf(stderr, "%s: file too short to hold load command region"

           " given in Mach-O header\n", filename_.c_str());

 }

 void Reader::Reporter::LoadCommandsOverrun(size_t claimed, size_t i,

                                            LoadCommandType type) {

   fprintf(stderr, "%s: file's header claims there are %ld"

           " load commands, but load command #%ld",

           filename_.c_str(), claimed, i);

   if (type) fprintf(stderr, ", of type %d,", type);

   fprintf(stderr, " extends beyond the end of the load command region\n");

 }

 void Reader::Reporter::LoadCommandTooShort(size_t i, LoadCommandType type) {

   fprintf(stderr, "%s: the contents of load command #%ld, of type %d,"

           " extend beyond the size given in the load command's header\n",

           filename_.c_str(), i, type);

 }

 void Reader::Reporter::SectionsMissing(const string &name) {

   fprintf(stderr, "%s: the load command for segment '%s'"

           " is too short to hold the section headers it claims to have\n",

           filename_.c_str(), name.c_str());

 }

 void Reader::Reporter::MisplacedSegmentData(const string &name) {

   fprintf(stderr, "%s: the segment '%s' claims its contents lie beyond"

           " the end of the file\n", filename_.c_str(), name.c_str());

 }

 void Reader::Reporter::MisplacedSectionData(const string &section,

                                             const string &segment) {

   fprintf(stderr, "%s: the section '%s' in segment '%s'"

           " claims its contents lie outside the segment's contents\n",

           filename_.c_str(), section.c_str(), segment.c_str());

 }

 void Reader::Reporter::MisplacedSymbolTable() {

   fprintf(stderr, "%s: the LC_SYMTAB load command claims that the symbol"

           " table's contents are located beyond the end of the file\n",

           filename_.c_str());

 }

 void Reader::Reporter::UnsupportedCPUType(cpu_type_t cpu_type) {

   fprintf(stderr, "%s: CPU type %d is not supported\n",

           filename_.c_str(), cpu_type);

 }

 bool Reader::Read(const uint8_t *buffer,

                   size_t size,

                   cpu_type_t expected_cpu_type,

                   cpu_subtype_t expected_cpu_subtype) {

   assert(!buffer_.start);

   buffer_.start = buffer;

   buffer_.end = buffer + size;

   ByteCursor cursor(&buffer_, true);

   uint32_t magic;

   if (!(cursor >> magic)) {

     reporter_->HeaderTruncated();

     return false;

   }

   if (expected_cpu_type != CPU_TYPE_ANY) {

     uint32_t expected_magic;

     // validate that magic matches the expected cpu type

     switch (expected_cpu_type) {

       case CPU_TYPE_ARM:

       case CPU_TYPE_I386:

         expected_magic = MH_CIGAM;

         break;

       case CPU_TYPE_POWERPC:

         expected_magic = MH_MAGIC;

         break;

       case CPU_TYPE_X86_64:

         expected_magic = MH_CIGAM_64;

         break;

       case CPU_TYPE_POWERPC64:

         expected_magic = MH_MAGIC_64;

         break;

       default:

         reporter_->UnsupportedCPUType(expected_cpu_type);

         return false;

     }

     if (expected_magic != magic) {

       reporter_->BadHeader();

       return false;

     }

   }

   // Since the byte cursor is in big-endian mode, a reversed magic number

   // always indicates a little-endian file, regardless of our own endianness.

   switch (magic) {

     case MH_MAGIC:    big_endian_ = true;  bits_64_ = false; break;

     case MH_CIGAM:    big_endian_ = false; bits_64_ = false; break;

     case MH_MAGIC_64: big_endian_ = true;  bits_64_ = true;  break;

     case MH_CIGAM_64: big_endian_ = false; bits_64_ = true;  break;

     default:

       reporter_->BadHeader();

       return false;

   }

   cursor.set_big_endian(big_endian_);

   uint32_t commands_size, reserved;

   cursor >> cpu_type_ >> cpu_subtype_ >> file_type_ >> load_command_count_

          >> commands_size >> flags_;

   if (bits_64_)

     cursor >> reserved;

   if (!cursor) {

     reporter_->HeaderTruncated();

     return false;

   }

   if (expected_cpu_type != CPU_TYPE_ANY &&

       (expected_cpu_type != cpu_type_ ||

        expected_cpu_subtype != cpu_subtype_)) {

     reporter_->CPUTypeMismatch(cpu_type_, cpu_subtype_,

                               expected_cpu_type, expected_cpu_subtype);

     return false;

   }

   cursor

       .PointTo(&load_commands_.start, commands_size)

       .PointTo(&load_commands_.end, 0);

   if (!cursor) {

     reporter_->LoadCommandRegionTruncated();

     return false;

   }

   return true;

 }

 bool Reader::WalkLoadCommands(Reader::LoadCommandHandler *handler) const {

   ByteCursor list_cursor(&load_commands_, big_endian_);

   for (size_t index = 0; index < load_command_count_; ++index) {

     // command refers to this load command alone, so that cursor will

     // refuse to read past the load command's end. But since we haven't

     // read the size yet, let command initially refer to the entire

     // remainder of the load command series.

     ByteBuffer command(list_cursor.here(), list_cursor.Available());

     ByteCursor cursor(&command, big_endian_);

     // Read the command type and size --- fields common to all commands.

     uint32_t type, size;

     if (!(cursor >> type)) {

       reporter_->LoadCommandsOverrun(load_command_count_, index, 0);

       return false;

     }

     if (!(cursor >> size) || size > command.Size()) {

       reporter_->LoadCommandsOverrun(load_command_count_, index, type);

       return false;

     }

     // Now that we've read the length, restrict command's range to this

     // load command only.

     command.end = command.start + size;

     switch (type) {

       case LC_SEGMENT:

       case LC_SEGMENT_64: {

         Segment segment;

         segment.bits_64 = (type == LC_SEGMENT_64);

         size_t word_size = segment.bits_64 ? 8 : 4;

         cursor.CString(&segment.name, 16);

         size_t file_offset, file_size;

         cursor

             .Read(word_size, false, &segment.vmaddr)

             .Read(word_size, false, &segment.vmsize)

             .Read(word_size, false, &file_offset)

             .Read(word_size, false, &file_size);

         cursor >> segment.maxprot

                >> segment.initprot

                >> segment.nsects

                >> segment.flags;

         if (!cursor) {

           reporter_->LoadCommandTooShort(index, type);

           return false;

         }

         if (file_offset > buffer_.Size() ||

             file_size > buffer_.Size() - file_offset) {

           reporter_->MisplacedSegmentData(segment.name);

           return false;

         }

         // Mach-O files in .dSYM bundles have the contents of the loaded

         // segments removed, and their file offsets and file sizes zeroed

         // out. To help us handle this special case properly, give such

         // segments' contents NULL starting and ending pointers.

         if (file_offset == 0 && file_size == 0) {

           segment.contents.start = segment.contents.end = NULL;

         } else {

           segment.contents.start = buffer_.start + file_offset;

           segment.contents.end = segment.contents.start + file_size;

         }

         // The section list occupies the remainder of this load command's space.

         segment.section_list.start = cursor.here();

         segment.section_list.end = command.end;

         if (!handler->SegmentCommand(segment))

           return false;

         break;

       }

       case LC_SYMTAB: {

         uint32_t symoff, nsyms, stroff, strsize;

         cursor >> symoff >> nsyms >> stroff >> strsize;

         if (!cursor) {

           reporter_->LoadCommandTooShort(index, type);

           return false;

         }

         // How big are the entries in the symbol table?

         // sizeof(struct nlist_64) : sizeof(struct nlist),

         // but be paranoid about alignment vs. target architecture.

         size_t symbol_size = bits_64_ ? 16 : 12;

         // How big is the entire symbol array?

         size_t symbols_size = nsyms * symbol_size;

         if (symoff > buffer_.Size() || symbols_size > buffer_.Size() - symoff ||

             stroff > buffer_.Size() || strsize > buffer_.Size() - stroff) {

           reporter_->MisplacedSymbolTable();

           return false;

         }

         ByteBuffer entries(buffer_.start + symoff, symbols_size);

         ByteBuffer names(buffer_.start + stroff, strsize);

         if (!handler->SymtabCommand(entries, names))

           return false;

         break;

       }

       default: {

         if (!handler->UnknownCommand(type, command))

           return false;

         break;

       }

     }

     list_cursor.set_here(command.end);

   }

   return true;

 }

 // A load command handler that looks for a segment of a given name.

 class Reader::SegmentFinder : public LoadCommandHandler {

  public:

   // Create a load command handler that looks for a segment named NAME,

   // and sets SEGMENT to describe it if found.

   SegmentFinder(const string &name, Segment *segment) 

       : name_(name), segment_(segment), found_() { }

   // Return true if the traversal found the segment, false otherwise.

   bool found() const { return found_; }

   bool SegmentCommand(const Segment &segment) {

     if (segment.name == name_) {

       *segment_ = segment;

       found_ = true;

       return false;

     }

     return true;

   }

  private:

   // The name of the segment our creator is looking for.

   const string &name_;

   // Where we should store the segment if found. (WEAK)

   Segment *segment_;

   // True if we found the segment.

   bool found_;

 };

 bool Reader::FindSegment(const string &name, Segment *segment) const {

   SegmentFinder finder(name, segment);

   WalkLoadCommands(&finder);

   return finder.found();

 }

 bool Reader::WalkSegmentSections(const Segment &segment,

                                  SectionHandler *handler) const {

   size_t word_size = segment.bits_64 ? 8 : 4;

   ByteCursor cursor(&segment.section_list, big_endian_);

   for (size_t i = 0; i < segment.nsects; i++) {

     Section section;

     section.bits_64 = segment.bits_64;

     uint64_t size;

     uint32_t offset, dummy32;

     cursor

         .CString(&section.section_name, 16)

         .CString(&section.segment_name, 16)

         .Read(word_size, false, &section.address)

         .Read(word_size, false, &size)

         >> offset

         >> section.align

         >> dummy32

         >> dummy32

         >> section.flags

         >> dummy32

         >> dummy32;

     if (section.bits_64)

       cursor >> dummy32;

     if (!cursor) {

       reporter_->SectionsMissing(segment.name);

       return false;

     }

     if ((section.flags & SECTION_TYPE) == S_ZEROFILL) {

       // Zero-fill sections have a size, but no contents.

       section.contents.start = section.contents.end = NULL;

     } else if (segment.contents.start == NULL && 

                segment.contents.end == NULL) {

       // Mach-O files in .dSYM bundles have the contents of the loaded

       // segments removed, and their file offsets and file sizes zeroed

       // out.  However, the sections within those segments still have

       // non-zero sizes.  There's no reason to call MisplacedSectionData in

       // this case; the caller may just need the section's load

       // address. But do set the contents' limits to NULL, for safety.

       section.contents.start = section.contents.end = NULL;

     } else {

       if (offset < size_t(segment.contents.start - buffer_.start) ||

           offset > size_t(segment.contents.end - buffer_.start) ||

           size > size_t(segment.contents.end - buffer_.start - offset)) {

         reporter_->MisplacedSectionData(section.section_name,

                                         section.segment_name);

         return false;

       }

       section.contents.start = buffer_.start + offset;

       section.contents.end = section.contents.start + size;

     }

     if (!handler->HandleSection(section))

       return false;

   }

   return true;

 }

 // A SectionHandler that builds a SectionMap for the sections within a

 // given segment.

 class Reader::SectionMapper: public SectionHandler {

  public:

   // Create a SectionHandler that populates MAP with an entry for

   // each section it is given.

   SectionMapper(SectionMap *map) : map_(map) { }

   bool HandleSection(const Section &section) {

     (*map_)[section.section_name] = section;

     return true;

   }

  private:

   // The map under construction. (WEAK)

   SectionMap *map_;

 };

 bool Reader::MapSegmentSections(const Segment &segment,

                                 SectionMap *section_map) const {

   section_map->clear();

   SectionMapper mapper(section_map);

   return WalkSegmentSections(segment, &mapper);

 }

 }  // namespace mach_o

 }  // namespace google_breakpad