Added CPUTypeMismatchException (#450)

1. New exception triggers when there is a cputype or cputype
mismatch between fat header and internal macho slice in the
FatFile#populate_machos method.

2. Added a test for it along with adding a new binary file
to the test/bin/llvm folder.

Author: apainintheneck

lib/macho/exceptions.rb

@@ -63,6 +63,21 @@ def initialize
     end
   end
 
+  # Raised when there is a mismatch between the fat arch
+  # and internal slice cputype or cpusubtype.
+  class CPUTypeMismatchError < NotAMachOError
+    def initialize(fat_cputype, fat_cpusubtype, macho_cputype, macho_cpusubtype)
+      # @param cputype_fat [Integer] the CPU type in the fat header
+      # @param cpusubtype_fat [Integer] the CPU subtype in the fat header
+      # @param cputype_macho [Integer] the CPU type in the macho header
+      # @param cpusubtype_macho [Integer] the CPU subtype in the macho header
+      super ("Mismatch between cputypes >> 0x%08<fat_cputype>x and 0x%08<macho_cputype>x\n" \
+             "and/or cpusubtypes >> 0x%08<fat_cpusubtype>x and 0x%08<macho_cpusubtype>x" %
+            { :fat_cputype => fat_cputype, :macho_cputype => macho_cputype,
+              :fat_cpusubtype => fat_cpusubtype, :macho_cpusubtype => macho_cpusubtype })
+    end
+  end
+
   # Raised when a fat binary is loaded with MachOFile.
   class FatBinaryError < MachOError
     def initialize

lib/macho/fat_file.rb

@@ -379,6 +379,13 @@ def populate_machos
 
       fat_archs.each do |arch|
         machos << MachOFile.new_from_bin(@raw_data[arch.offset, arch.size], **options)
+
+        # Make sure that each fat_arch and internal slice.
+        # contain matching cputypes and cpusubtypes
+        next if machos.last.header.cputype == arch.cputype &&
+                machos.last.header.cpusubtype == arch.cpusubtype
+
+        raise CPUTypeMismatchError.new(arch.cputype, arch.cpusubtype, machos.last.header.cputype, machos.last.header.cpusubtype)
       end
 
       machos

test/bin/llvm/macho-invalid-fat_cputype

@@ -42,6 +42,12 @@ def test_zero_arch_file
     end
   end
 
+  def test_mismatch_cpu_arch_file
+    assert_raises MachO::CPUTypeMismatchError do
+      MachO::FatFile.new("test/bin/llvm/macho-invalid-fat_cputype")
+    end
+  end
+
   def test_fat_header
     filenames = FAT_ARCH_PAIRS.map { |a| fixture(a, "hello.bin") }