/usr/lib/ruby/vendor_ruby/ffi/ is in ruby-ffi 1.0.11debian-3.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/ffi/autopointer.rb
/usr/lib/ruby/vendor_ruby/ffi/buffer.rb
/usr/lib/ruby/vendor_ruby/ffi/callback.rb
/usr/lib/ruby/vendor_ruby/ffi/enum.rb
/usr/lib/ruby/vendor_ruby/ffi/errno.rb
/usr/lib/ruby/vendor_ruby/ffi/ffi.rb
/usr/lib/ruby/vendor_ruby/ffi/io.rb
/usr/lib/ruby/vendor_ruby/ffi/library.rb
/usr/lib/ruby/vendor_ruby/ffi/managedstruct.rb
/usr/lib/ruby/vendor_ruby/ffi/memorypointer.rb
/usr/lib/ruby/vendor_ruby/ffi/platform/
/usr/lib/ruby/vendor_ruby/ffi/platform.rb
/usr/lib/ruby/vendor_ruby/ffi/platform/arm-linux/
/usr/lib/ruby/vendor_ruby/ffi/platform/arm-linux/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/i386-darwin/
/usr/lib/ruby/vendor_ruby/ffi/platform/i386-darwin/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/i386-freebsd/
/usr/lib/ruby/vendor_ruby/ffi/platform/i386-freebsd/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/i386-linux/
/usr/lib/ruby/vendor_ruby/ffi/platform/i386-linux/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/i386-netbsd/
/usr/lib/ruby/vendor_ruby/ffi/platform/i386-netbsd/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/i386-openbsd/
/usr/lib/ruby/vendor_ruby/ffi/platform/i386-openbsd/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/i386-solaris/
/usr/lib/ruby/vendor_ruby/ffi/platform/i386-solaris/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/i386-windows/
/usr/lib/ruby/vendor_ruby/ffi/platform/i386-windows/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/i486-gnu/
/usr/lib/ruby/vendor_ruby/ffi/platform/i486-gnu/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/ia64-linux/
/usr/lib/ruby/vendor_ruby/ffi/platform/ia64-linux/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/mips-linux/
/usr/lib/ruby/vendor_ruby/ffi/platform/mips-linux/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/mipsel-linux/
/usr/lib/ruby/vendor_ruby/ffi/platform/mipsel-linux/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/powerpc-aix/
/usr/lib/ruby/vendor_ruby/ffi/platform/powerpc-aix/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/powerpc-darwin/
/usr/lib/ruby/vendor_ruby/ffi/platform/powerpc-darwin/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/powerpc-linux/
/usr/lib/ruby/vendor_ruby/ffi/platform/powerpc-linux/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/s390-linux/
/usr/lib/ruby/vendor_ruby/ffi/platform/s390-linux/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/s390x-linux/
/usr/lib/ruby/vendor_ruby/ffi/platform/s390x-linux/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/sparc-linux/
/usr/lib/ruby/vendor_ruby/ffi/platform/sparc-linux/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/sparc-solaris/
/usr/lib/ruby/vendor_ruby/ffi/platform/sparc-solaris/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/sparcv9-solaris/
/usr/lib/ruby/vendor_ruby/ffi/platform/sparcv9-solaris/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/x86_64-darwin/
/usr/lib/ruby/vendor_ruby/ffi/platform/x86_64-darwin/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/x86_64-freebsd/
/usr/lib/ruby/vendor_ruby/ffi/platform/x86_64-freebsd/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/x86_64-linux/
/usr/lib/ruby/vendor_ruby/ffi/platform/x86_64-linux/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/x86_64-netbsd/
/usr/lib/ruby/vendor_ruby/ffi/platform/x86_64-netbsd/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/x86_64-openbsd/
/usr/lib/ruby/vendor_ruby/ffi/platform/x86_64-openbsd/types.conf
/usr/lib/ruby/vendor_ruby/ffi/platform/x86_64-solaris/
/usr/lib/ruby/vendor_ruby/ffi/platform/x86_64-solaris/types.conf
/usr/lib/ruby/vendor_ruby/ffi/pointer.rb
/usr/lib/ruby/vendor_ruby/ffi/struct.rb
/usr/lib/ruby/vendor_ruby/ffi/struct_layout_builder.rb
/usr/lib/ruby/vendor_ruby/ffi/tools/
/usr/lib/ruby/vendor_ruby/ffi/tools/const_generator.rb
/usr/lib/ruby/vendor_ruby/ffi/tools/generator.rb
/usr/lib/ruby/vendor_ruby/ffi/tools/generator_task.rb
/usr/lib/ruby/vendor_ruby/ffi/tools/struct_generator.rb
/usr/lib/ruby/vendor_ruby/ffi/tools/types_generator.rb
/usr/lib/ruby/vendor_ruby/ffi/types.rb
/usr/lib/ruby/vendor_ruby/ffi/union.rb
/usr/lib/ruby/vendor_ruby/ffi/variadic.rb