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Re: [PATCH] Vtable pointer verification (corruption/attach detection -- new feature
- From: Xinliang David Li <davidxl at google dot com>
- To: Caroline Tice <cmtice at google dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Sun, 4 Nov 2012 22:02:58 -0800
- Subject: Re: [PATCH] Vtable pointer verification (corruption/attach detection -- new feature
- References: <CABtf2+RvLG_K1t+iCzrQxLc1p=FuPHB3Ae+Gm7RfpRXk7tn=4g@mail.gmail.com>
Can you split the patch into two parts? One for runtime and and one
for GCC ? Please also use -up option in the diff command to generate
the patch file.
thanks,
David
On Thu, Nov 1, 2012 at 1:07 PM, Caroline Tice <cmtice@google.com> wrote:
> We have been developing a new security hardening feature for GCC that
> is designed to detect and handle (during program execution) when a
> vtable pointer that is about to be used for a virtual function call is
> not a valid vtable pointer for that call (i.e. it has become
> corrupted, possibly due to a hacker attack). We gave a presentation
> on this work at the Gnu Tools Cauldron in Prague last July. We now
> have the implementation fully working and are submitting this patch
> for review. We would like to get this into the next release of GCC if
> possible.
>
> The general idea is to collect class hierarchy and vtable pointer data
> while parsing the classes, then use this data to generate (at runtime)
> sets of valid vtable pointers, one for each class. We also find every
> virtual function call and insert a verification call before the
> virtual function call. The verification call takes the set of valid
> vtable pointers for the declared class of the object, and the actual
> vtable pointer in the object. If the vtable pointer in the object is
> in the set of valid vtable pointers for the object, then verification
> succeeds and the virtual call is allowed. Otherwise verification
> fails and the program aborts.
>
> We have a written a more detailed design document, which I am also
> attaching to this email (GCCVtableSecurityHardeningProposal.txt).
>
> The implementation can be divided into roughly two parts:
> modifications to the main gcc compiler, for things that happen at
> compile time (collecting the class hierarchy & vtable information;
> generating the runtime calls to build the data sets from this data;
> inserting calls to the verification function); and modifications to
> the runtime, i.e. functions that go into libstdc++ for building the
> data sets, for doing the verification against the data sets, for
> protecting the memory where the data sets reside, etc.).
>
> Please let me know if there is any more information you need, or if
> you have any questions about this patch.
>
> -- Caroline Tice
> cmtice@google.com
>
> libstdc++/ChangeLog
>
> 2012-11-01 Caroline Tice <cmtice@google.com>
>
> * src/Makefile.am: Add libvtv___la_LIBDD definition; update CXXLINK
> to search in libvtv___la_LIBADD and to link in libvtv_init.
> * src/Makefile.in: Regenerate.
> * libsupc++/Makefile.am: Add libvtv_init.la and libvtv_stubs.la to
> toolexeclib_LTLIBRARIES. Add vtv_rts.cc, vtv_malloc.cc and
> vtv_utils.cc to sources. Define vtv_init_sources and
> vtv_stubs_sources. Also define libvtv_init_la_SOURCES and
> libvtv_stubs_la_sources.
> * libsupc++/Makefile.in: Regenerate.
> * libsupc++/vtv_rts.cc: New file.
> * libsupc++/vtv_malloc.h: New file.
> * libsupc++/vtv_rts.h: New file.
> * libsupc++/vtv_fail.h: New file.
> * libsupc++/vtv_set.h: New file.
> * libsupc++/vtv_stubs.cc: New file.
> * libsupc++/vtv_utils.cc: New file.
> * libcupc++/vtv_utils.h: New file.
> * libsupc++/vtv_init.cc: New file.
> * libsupc++/vtv_malloc.cc: New file.
> * config/abi/pre/gnu.ver (GLIBCXX_3.4.18): Add vtable verification
> functions and vtable map variables to library export list.
>
> gcc/ChangeLog:
>
> 2012-11-01 Caroline Tice <cmtice@google.com>
>
> * tree.h (save_vtable_map_decl): New function decl.
> * tree-pass.h (pass_vtable_verify): New pass declaration.
> * cp/init.c (build_vtbl_address): Remove 'static' qualifier from
> function declaration and definition.
> * cp/class.c (finish_struct_1): Add call to vtv_save_class_info,
> if the vtable verify flag is set.
> * cp/Make-lang.in: Add vtable-class-hierarchy.o to list of object
> files. Add definition for building vtable-class-hierarchy.o.
> * cp/pt.c (mark_class_instantiated): Add call to vtv_save_class_info
> if the vtable verify flag is set.
> * cp/decl2 (start_objects): Remove 'static' qualifier from function
> declaratin and definition. Add new paramater, 'extra_name'. Change
> 'type' var from char array to char *. Call xmalloc & free for 'type'.
> Add 'extra_name' to 'type' string.
> (finish_objects): Remove 'static' qualifier from function declaration
> and definition. Change return type from void to tree. Make function
> return early if we're doing vtable verification and the function is
> a vtable verification constructor init function. Make this function
> return 'fn'.
> (generate_ctor_or_dtor_function): Add third argument to calls to
> start_objects.
> (cp_write_global_declarations): Add calls to vtv_recover_class_info,
> vtv_compute_class_hierarchy_transitive_closure, and
> vtv_generate_init_routine, if the vtable verify flag is set.
> * cp/config-lang.in (gtfiles): Add vtable-class-hierarchy.c to the
> list of gtfiles.
> * cp/vtable-class-hierarchy.c: New file.
> * cp/mangle.c (get_mangled_id): Remove static qualifier from function
> definition.
> * cp/cp-tree.h: Add extern function declarations for start_objects,
> finish_objects, build_vtbl_address, get_mangled_id,
> vtv_compute_class_hierarchy_transitive_closure,
> vtv_generate_init_routine, vtv_save_class_info and
> vtv_recover_class_info.
> * timevar.def: Add TV_VTABLE_VERIFICATION.
> * flag-types.h: Add enum vtv_priority defintion.
> * tree-vtable-verify.c: New file.
> * tree-vtable-verify.h: New file.
> * common.opt: Add definitions for fvtable-verify= and its string
> options (vtv_priority enum values).
> * varasm.c (assemble_variable): Check to see if the variable is a
> vtable map variable, and if so, put it into the vtable map variable
> section, and make it comdat.
> (assemble_vtv_preinit_initializer): New function, to put the
> vtable verification constructor initialization function in the preinit
> array, if appropriate.
> * output.h: Add extern declaration for
> assemble_vtv_preinit_initializer.
> * Makefile.in: Add tree-vtable-verify.o to list of OBJS. Add build
> rule for tree-vtable-verify.o Add tre-vtable-verify.c to list of source
> files.
> * passes.c (init_optimization_passes): Add pass_vtable_verify.